CN115314022A

CN115314022A - Transverse-excited film bulk acoustic resonator matrix filter with input and output impedance matching to radio frequency front end element

Info

Publication number: CN115314022A
Application number: CN202210493533.2A
Authority: CN
Inventors: 安德鲁·古耶特; 尼尔·芬齐; 迈克尔·艾迪; 布莱恩特·加西亚
Original assignee: Resonant Inc
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2021-05-07
Filing date: 2022-05-07
Publication date: 2022-11-08
Also published as: JP2022173148A

Abstract

A matrix filter having antenna ports, receive ports, and transmit ports is disclosed. A receive matrix filter coupled between each receive port and the antenna port; a transmit matrix filter is coupled between the antenna port and each transmit port. The impedance at the receive port is matched to the input impedance of a Low Noise Amplifier (LNA), the impedance at the transmit port is matched to the output impedance of a Power Amplifier (PA), and the impedance at the antenna port is matched to the impedance of the antenna.

Description

Transverse-excited film bulk acoustic resonator matrix filter with input and output impedance matching to radio frequency front-end element

Technical Field

The present disclosure relates to radio frequency filters using acoustic wave resonators, and more particularly to filters for use in communication devices.

Background

A Radio Frequency (RF) filter is a two-terminal device that is configured to pass some frequencies and block others, where "pass" means transmit with relatively low signal loss and "block" means block or substantially attenuate. The range of frequencies passed by the filter is referred to as the "passband" of the filter. The frequency range blocked by such a filter is called the "stop band" of the filter. A typical RF filter has at least one pass band and at least one stop band. The specific requirements of the pass band or stop band depend on the specific application. For example, a "passband" may be defined as a range of frequencies in which the insertion loss of the filter is better than a defined value such as 1dB, 2dB, or 3 dB. A "stop band" may be defined as a frequency range in which the rejection of the filter is greater than a defined value, for example a value of 20dB, 30dB, 40dB or more, depending on the particular application.

RF filters are used in communication systems that transmit information over wireless links. For example, RF filters can be found in the RF front-ends of cellular base stations, mobile phones and computing devices, satellite transceivers and ground stations, internet of things (IoT) devices, laptops and tablets, fixed-point radio links, and other communication systems. RF filters are also used in radar and electronic and information warfare systems.

RF filters typically require many design tradeoffs to achieve the best compromise between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size and cost for each particular application. Specific designs and manufacturing methods and enhancements may benefit from one or more of these needs simultaneously.

The performance enhancement of RF filters in wireless systems can have a wide impact on system performance. System performance can be improved by improving the RF filter, such as larger cell size, longer battery life, higher data rate, larger network capacity, lower cost, greater security, higher reliability, etc. These improvement points may be implemented individually or in combination at various levels of the wireless system, for example at the RF module, RF transceiver, mobile or fixed subsystem or network level.

High performance RF filters for current communication systems typically incorporate acoustic wave resonators including Surface Acoustic Wave (SAW) resonators, bulk acoustic wave BAW) resonators, thin Film Bulk Acoustic Resonators (FBAR), and other types of acoustic wave resonators. However, these prior art techniques are not suitable for use at higher frequencies and bandwidths that will be required for future communication networks.

To obtain a wider communication channel bandwidth, it is necessary to use a higher frequency communication band. The 3GPP (third generation partnership project) has standardized radio access technologies for mobile telephone networks. The radio access technology for fifth generation mobile networks is defined in the 5G NR (new radio) standard. The 5G NR standard defines several new communication bands. Two of these new communications bands are N77 and N79, where N77 uses a frequency range of 3300MHz to 4200MHz and N79 uses a frequency range of 4400MHz to 5000 MHz. Both frequency band N77 and frequency band N79 use Time Division Duplex (TDD), so that communication devices operating in frequency band N77 and/or frequency band N79 use the same frequency for uplink and downlink transmissions. The band pass filters for the N77 and N79 frequency bands must be able to handle the transmit power of the communication device. High frequencies and wide bandwidths are also required in the 5GHz and 6GHz wireless bands. The 5G NR standard also defines the millimeter wave communication band at frequencies between 24.25GHz and 40 GHz.

Laterally excited thin film bulk acoustic resonators (XBARs) are acoustic resonator structures used in microwave filters. This XBAR is described in U.S. Pat. No. 10,491,291 entitled "TRANSVERSELY EXCITED FILM BULK ACOUSTIC RESONATOR". XBAR resonators include interdigital transducers (IDTs) formed on a thin floating layer or membrane having a single crystal of piezoelectric material. The IDT includes a first set of parallel fingers extending from a first bus bar and a second set of parallel fingers extending from a second bus bar. The first set of parallel fingers and the second set of parallel fingers are interleaved. The microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm. XBAR resonators provide high electromechanical coupling and high frequency capability. XBAR resonators can be used in a variety of RF filters including band-stop filters, band-pass filters, duplexers, and multiplexers. XBAR is well suited for use in filters for communication bands with frequencies above 3 GHz. The matrix XBAR filter is also suitable for frequencies between 1GHz and 3 GHz.

Disclosure of Invention

The invention discloses a matrix filtering duplexer, comprising: a receive matrix filter coupled between the receive port and the antenna port; and a transmit matrix filter coupled between the antenna port and the transmit port, wherein an impedance at the receive port matches an input impedance of a Low Noise Amplifier (LNA), an impedance at the transmit port matches an output impedance of a Power Amplifier (PA), and an impedance at the antenna port matches an impedance of an antenna.

Wherein the impedance at the receive port is 300 ohms of the filter output port, which matches the input impedance of a Low Noise Amplifier (LNA) of the RF receiver, the impedance at the transmit port is 4 ohms of the filter output port, which matches the output impedance of a Power Amplifier (PA) of the RF transmitter, and the impedance at the antenna port is 50 ohms of the filter input port, which matches the impedance of a Radio Frequency (RF) antenna.

Wherein the receive matrix filter and the transmit matrix filter each comprise: two or more sub-filters connected between the filter antenna port and a respective filter output port, each sub-filter comprising a ladder circuit having n series elements of laterally excited thin film bulk acoustic resonators (XBAR) and n-1 parallel elements of capacitance, wherein n, the order of the sub-filter, is an integer greater than 2.

Wherein the two or more sub-filters have non-contiguous passbands, and wherein each of the non-contiguous passbands is a passband of only one sub-filter.

Wherein each of the two or more sub-filters has a non-continuous pass band separated by a stop band, the stop band being present if an input-output transfer function of the matrix filter is less than-20 dB.

Wherein the XBAR series element comprises a first end XBAR connected to the first sub-filter port, a second end XBAR connected to the second sub-filter port, and one or more intermediate XBARs connected between the first and second end acoustic resonators.

Wherein a radio frequency signal applied to the transmit port or the antenna port excites a primary shear acoustic mode in the XBAR series element.

The invention also discloses a matrix filter multiplexer, comprising: first and second receive matrix filters coupled between the first and second receive ports and an antenna port; and first and second transmit matrix filters coupled between the antenna port and the first and second transmit ports, wherein impedances at the first and second receive ports match an input impedance of the low noise amplifier, impedances at the first and second transmit ports match an output impedance of the power amplifier, and impedances at the antenna port match an impedance of the antenna.

Wherein the impedance at the first and second receive ports is 300 ohms of a filter output port, which is matched to an input impedance of Low Noise Amplifiers (LNAs) of the first and second radio frequency receivers, the impedance at the first and second transmit ports is 4 ohms of the filter output port, which is matched to an output impedance of Power Amplifiers (PAs) of the first and second radio frequency transmitters, and the impedance at the antenna port is 50 ohms of the filter input port, which is matched to an impedance of a Radio Frequency (RF) antenna.

Wherein the first and second receive matrix filters and the first and second transmit matrix filters each comprise: two or more sub-filters connected between the filter antenna port and a respective filter output port, each sub-filter comprising a ladder circuit having n series elements of laterally excited thin film bulk acoustic resonators (XBAR) and n-1 parallel elements of capacitance, wherein n, the order of the sub-filter, is an integer greater than 2.

Wherein a radio frequency signal applied to one of the first transmit port, the second transmit port, or the antenna port excites a primary shear acoustic mode in the XBAR series element.

The invention further discloses a matrix filter, comprising: a filter input port; and two or more sub-filters connected between the filter input port and a respective filter output port, each sub-filter comprising a ladder circuit having n series elements of laterally excited thin film bulk acoustic resonators (XBAR) and n-1 parallel elements of capacitance, where n, the order of the sub-filters, is an integer greater than 2, wherein the impedance at the output ports of the first plurality of respective filters matches the input impedance of the low noise amplifier, the impedance at the output ports of the second plurality of respective filters matches the output impedance of the power amplifier, and the impedance at the input ports matches the impedance of the antenna.

Wherein only one of the two or more sub-filters is selected to be connected between the filter input port and the respective filter output port; and wherein no input-output transfer function of a single sub-filter intersects the input-output transfer function of another sub-filter at frequencies where the transfer functions of both filters are above-20 dB.

Wherein sub-filter connections between the filter inputs and respective filter output ports may be switched to select one or more non-contiguous passbands.

The invention further discloses a three-band diversity receiver, comprising: a matrix triplexer coupled between an antenna and three receivers, the triplexer comprising; a first sub-filter coupled between a first filter port and a second filter port, wherein the second filter port is coupled to the first receiver; a second sub-filter coupled between the first filter port and a third filter port, wherein the third filter port is coupled to the second receiver; a third sub-filter coupled between the first filter port and a fourth filter port, wherein the fourth filter port is coupled to the third receiver; wherein each sub-filter comprises a ladder circuit having at least three laterally excited thin film bulk acoustic resonator (XBAR) series elements and at least two capacitive parallel elements; and wherein the impedance of the second, third and fourth filter ports is matched to the input impedance of the respective low noise amplifiers and the impedance at said first filter port is matched to the impedance of the antenna.

Wherein each of the 3 sub-filters has a non-continuous pass band separated from the pass bands of all other 3 sub-filters, wherein the separation is done by a stop band, which is present in case of less than-20 dB at the input-output transfer function of the matrix filter.

Wherein each of the XBAR series elements is connected in series between the first sub-filter port and the second sub-filter port; and each of said parallel capacitors is connected between ground and a node between a respective pair of XBAR series elements.

Drawings

Fig. 1 includes a schematic plan view, two schematic cross-sectional views and a detailed cross-sectional view of a laterally excited thin film bulk acoustic resonator (XBAR).

Fig. 2A is an equivalent circuit model of an acoustic resonator.

Fig. 2B is an admittance diagram of an ideal acoustic resonator.

Fig. 2C is a circuit symbol of the acoustic resonator.

Fig. 3A is a schematic diagram of a matrix filter using acoustic resonators having input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 3B is a schematic diagram of the sub-filter of fig. 3A.

Fig. 4 is a performance graph of one embodiment of the filter of fig. 3A, showing the resonant frequencies of the sub-filters.

Fig. 5 is a performance graph of an embodiment of the filter of fig. 3A, illustrating the passband frequencies of the sub-filters.

Fig. 6 is a schematic diagram of a matrix duplexer using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 7 is a graph of an input-output transfer function of an embodiment of the switchplexer of fig. 6.

Fig. 8 is a schematic diagram of a matrix triplexer using an acoustic resonator with input and output impedances matched to a Radio Frequency Front End (RFFE) element.

Figure 9 is a graph of the input-output transfer function of the embodiment of the triplexer of figure 8.

Figure 10A is a schematic diagram of a reconfigurable switch matrix filter using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 10B is a schematic diagram of a sub-filter and switch module of fig. 10A.

Fig. 10C is a schematic diagram of another seed filter and switch module of fig. 10A.

Figure 11 is a graph of input-output transfer functions for two configurations of the embodiment of the reconfigurable switch matrix filter of figure 10A.

Fig. 12 is a schematic block diagram of a Frequency Division Duplex (FDD) radio having input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 13 is a block diagram of a triple-band diversity receiver using a matrix triplexer with input and output impedances matched to radio frequency front-end (RFFE) elements.

Figure 14 is a block diagram of a dual band split radio using a matrix multiplexer filter with input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 15A is a schematic diagram of a matrix filter using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements.

Fig. 15B shows specific component characteristics of the first example of fig. 15A.

Fig. 15C shows specific component characteristics of the second example of fig. 15A.

Throughout the specification, elements appearing in the drawings are assigned a three-digit or four-digit reference numeral, where the two least significant bits are specific to the element and one or two most significant bits are the figure number showing the element first. Elements not described in connection with the figures may be assumed to have the same characteristics and functions as previously described elements having the same reference numerals.

Detailed Description

Description of the devices

A laterally excited thin film bulk acoustic resonator (XBAR) is a new resonator structure used as an acoustic filter for filtering microwave signals. Such an XBAR is described in patent U.S. Pat. No. 10,491,291, entitled TRANSVERSELY EXCITED FILM BULK ACOUSTIC RESONATOR, the entire contents of which are incorporated herein by reference. XBAR resonators include a conductor pattern with an interdigital transducer (IDT) formed on a thin floating layer or diaphragm of piezoelectric material. The IDT has two bus bars, each connected to a set of fingers, and the two sets of fingers are interleaved over a cavity on the diaphragm, the cavity being formed in the substrate on which the resonators are mounted. The diaphragm spans the cavity and may include front and/or back dielectric layers. A microwave signal applied to the IDT excites shear dominant acoustic waves in the piezoelectric membrane such that acoustic energy flows substantially perpendicular to the surface of the layer that is perpendicular or transverse to the direction of the electric field generated by the IDT. XBAR resonators provide very high electromechanical coupling and high frequency capability.

A matrix filter is a filter architecture that allows the implementation of various low frequency filters using small XBAR resonators. The sub-filters of the matrix filter may provide low frequency non-continuous band pass filtering. Such a bandpass sub-filter has a ladder filter circuit with an XBAR series element and a capacitor parallel element. Improved XBAR resonators, filters and fabrication techniques are described below that set the input and/or output impedance of a matrix filter over a wide range in order to provide impedance matching to Radio Frequency Front End (RFFE) elements, such as antennas (Ant), power Amplifiers (PA) and low noise amplifiers (LN). Since the matrix filter has an impedance matched to the RFFE, no external impedance matching or switching is required.

Fig. 1 shows a simplified schematic top view, orthogonal cross-sectional view and detailed cross-sectional view of a laterally excited thin film bulk acoustic resonator (XBAR) 100. XBAR resonators such as resonator 100 may be used in a variety of RF filters including band-stop filters, band-pass filters, duplexers, and multiplexers. XBAR is particularly suitable for filters in the communication bands with frequencies above 3 GHz. The matrix XBAR filter described in this patent is also applicable to frequencies above 1 GHz.

XBAR 100 is comprised of a thin film conductor pattern formed on the surface of a piezoelectric plate 110 having parallel front and

back surfaces

112 and 114, respectively. The piezoelectric plate is a thin single crystal layer made of a piezoelectric material such as lithium niobate, lithium tantalate, langasite, gallium nitride, or aluminum nitride. The piezoelectric plate is cut such that the orientation of the X, Y and Z crystal axes with respect to the front and back faces is known and consistent. The piezoelectric plate may be Z-cut (i.e., the Z-axis is perpendicular to the front and back faces 112, 114), rotationally Z-cut, or rotationally YX-cut. XBARs can be fabricated on piezoelectric plates having other crystallographic orientations.

The back side 114 of the piezoelectric plate 110 is attached to the surface of the substrate 120, except that a portion of the piezoelectric plate 110 is not attached to the surface of the substrate 120, wherein the portion of the piezoelectric plate 110 forms a diaphragm 115, the diaphragm 115 spanning a cavity 140 formed in the substrate. The portion of the piezoelectric plate spanning the cavity is referred to herein as the "diaphragm" 115 because this portion is physically similar to the diaphragm of the microphone. As shown in fig. 1, the diaphragm 115 abuts the remainder of the piezoelectric plate 110 around the entire perimeter 145 of the cavity 140. In this case, "adjacent" means "continuously connected without any other article in between". In other configurations, the diaphragm 115 may abut the piezoelectric plate around at least 50% of the perimeter 145 of the cavity 140.

The substrate 120 provides mechanical support for the piezoelectric plate 110. The substrate 120 may be, for example, silicon, sapphire, quartz, or some other material, or a combination of these materials. The back side 114 of the piezoelectric plate 110 may be attached to the substrate 120 using a wafer bonding process. Alternatively, the piezoelectric plate 110 may be grown on the substrate 120 or attached to the substrate in some other manner. The piezoelectric plate 110 may be attached directly to the substrate, or may be attached to the substrate 120 via one or more intermediate layers of material (not shown in fig. 1).

The conventional meaning of "cavity" is "empty space within a solid". The cavity 140 may bebase:Sub>A hole completely through the substrate 120 (as shown in cross-sectionsbase:Sub>A-base:Sub>A and B-B) or may bebase:Sub>A groove in the substrate 120 below the diaphragm 115. For example, the cavity 140 may be formed by selectively etching the substrate 120 before or after attaching the piezoelectric plate 110 to the substrate 120.

The conductor pattern of XBAR 100 includes an interdigital transducer (IDT) 130. The IDT130 includes a first plurality of parallel fingers, such as finger 136, extending from the first bus bar 132 and a second plurality of fingers extending from the second bus bar 134. The first and second pluralities of parallel fingers are interleaved. The interleaved fingers overlap a distance AP, which is commonly referred to as the "aperture" of the IDT. The center-to-center distance L between the outermost fingers of IDT130 is the "length" of the IDT.

First and

second busbars

132, 134 serve as terminals of XBAR 100. A radio frequency or microwave signal applied between the two

bus bars

132, 134 of the IDT130 excites a primary acoustic mode within the piezoelectric plate 110. The primary acoustic mode of the XBAR is the bulk shear mode, in which acoustic energy propagates in a direction substantially perpendicular to the surface of the piezoelectric plate 110, which is also perpendicular or transverse to the direction of the electric field generated by the IDT fingers. XBAR is therefore considered to be a laterally excited thin film bulk wave resonator.

The IDT130 is placed on the piezoelectric plate 110 such that at least the fingers of the IDT130 are disposed on the diaphragm 115 of the piezoelectric plate, the diaphragm 115 straddling or suspended over the cavity 140. As shown in fig. 1, the cavity 140 has a rectangular shape with a dimension that is greater than the length L of the aperture AP and IDT 130. The cavities of the XBAR may have different shapes, such as regular or irregular polygons. The cavities of the XBAR may have more or less than four sides, which may be straight or curved.

A detailed cross-sectional view (detail C) shows two

IDT fingers

136a, 136b on the surface of the piezoelectric plate 110. Dimension p is the "pitch" of the IDT and dimension w is the width or "mark" of the IDT fingers. A dielectric layer 150 can be formed between and optionally over the IDT fingers (see IDT finger 136 a). The dielectric layer 150 may be a non-piezoelectric dielectric material such as silicon dioxide or silicon nitride. The dielectric layer 150 may be formed of multiple layers of two or more materials.

IDT fingers

136a and 136b can be aluminum, copper, beryllium, gold, tungsten, molybdenum, alloys, combinations thereof, or some other electrically conductive material. Thin (relative to the total thickness of the conductor) layers of other metals (e.g., chromium or titanium) may be formed under and/or over the fingers and/or as layers within the fingers to improve adhesion between the fingers and the piezoelectric plate 110 and/or to passivate or encapsulate the fingers and/or to improve power handling. The bus bars of the IDT130 can be made of the same or different material than the fingers.

For ease of illustration in fig. 1, the geometrical spacing and width of the IDT fingers are greatly exaggerated relative to the length (dimension L) and aperture (dimension AP) of the XBAR. A typical XBAR has more than ten parallel fingers in the IDT 110. An XBAR may have hundreds of parallel fingers in IDT 110. Similarly, the thickness of the fingers is greatly exaggerated in the cross-sectional view.

XBARs based on shear acoustic resonance can achieve better performance than current state-of-the-art Surface Acoustic Wave (SAW), film Bulk Acoustic Resonator (FBAR) and solid state fabricated resonator bulk acoustic wave (SMR BAW) devices. In particular, the piezoelectric coupling of shear wave XBAR resonances can be very high (> 20%) compared to other acoustic resonators. High voltage galvanic coupling enables the design and implementation of various types of microwave and millimeter wave filters with appreciable bandwidth.

The basic behavior of acoustic resonators, including XBARs, is typically described using a butterworth-vandyke (BVD) circuit model as shown in fig. 2A. The BVD circuit model consists of one dynamic arm and one static arm. The dynamic arm comprises a dynamic inductor L _m Dynamic capacitor C _m And a resistance R _m . The static arm comprises a static capacitor C ₀ And a resistance R ₀ . Although the BVD model does not fully describe the behavior of the acoustic resonator, it well models the two main resonances used to design bandpass filters, duplexers and multiplexers (a multiplexer is a filter that has more than 2 input or output ports with multiple passbands).

The first dominant resonance of the BVD model is due to the dynamic inductance L _m And a dynamic capacitance C _m Dynamic resonance caused by the series combination of (a). The second main resonance of the BVD model is due to the dynamic inductance L _m Dynamic capacitor C _m And a static capacitance C ₀ The resulting antiresonance of the combination. In a lossless resonator (R) _m ＝R ₀ = 0), the frequency Fr of the dynamic resonance is given by the following equation

Frequency F of antiresonance _a Is given by

Wherein γ = C ₀ /C _m Depending on the resonator structure and the type and orientation of the crystal axis of the piezoelectric material.

Fig. 2B is a graph 200 of admittance magnitude of a theoretical lossless acoustic resonator. The acoustic resonator has a resonance 212 at a resonance frequency where the admittance of the resonator approaches infinity. Resonance is determined by the dynamic inductance L in the BVD model of FIG. 2A _m And a dynamic capacitance C _m Due to the series combination of (a). The acoustic resonator also exhibits an anti-resonance 214 when the admittance of the resonator is near zero. The anti-resonance being caused by a dynamic inductance L _m Dynamic capacitor C _m And a static capacitor C ₀ Is caused by a combination of (a). In a lossless resonator (R) _m ＝R ₀ = 0), resonant frequency F _r Is given by

Frequency F of antiresonance _a Is given by

In overly simplified terms, a lossless acoustic resonator may be considered to be a short circuit at the resonant frequency 212 and an open circuit at the anti-resonant frequency 214. The resonant and anti-resonant frequencies in fig. 2B are representative, and the acoustic resonator may be designed for other frequencies.

Fig. 2C shows a circuit symbol of an acoustic resonator such as an XBAR. This notation will be used to designate each acoustic resonator in the filter schematic in subsequent figures.

Fig. 3A is a schematic diagram of a matrix filter 300 using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements. The matrix filter 300 comprises an array 310 of n sub-filters 320-1, 320-2,320-n connected in parallel between a first filter port (FP 1) and a second filter port (FP 2), where n is an integer larger than 1. The sub-filters 320-1, 320-2,320-n have discrete pass bands such that the bandwidth of the matrix filter 300 is not equal to the sum of the bandwidths of the constituent sub-filters, but rather have three separate and independent pass bands, the pass bands being separated by stop bands, which exist where the input-output transfer function of the matrix filter 300 is less than-20 dB. In the subsequent examples of this patent, n =3. N may be less than or greater than 3 as desired to provide the desired non-contiguous passband for matrix filter 300. In some cases, the n sub-filters 320-1, 320-2,320-n may include one or more XBARs. The filter 300 and/or the sub-filters may be RF filters that pass a frequency band defined by the 5G NR standard.

The sub-filter array 310 is terminated at FP1 by acoustic resonators XL1 and XH1, which are preferably, but not necessarily, XBARs. The sub-filter array 310 is terminated at FP2 by acoustic resonators XL2 and XH2, which are preferably but not necessarily XBARs. Acoustic resonators XL1, XL2, XH1, and XH2 produce "transmission zeros" at their respective resonant frequencies. The "transmission zero" is the frequency at which the input-output transfer function of filter 300 is very low (zero if acoustic resonators XL1, XL2, XH1, and XH2 are lossless). A zero transmission may be caused by one or more acoustic resonator pairs producing a very low impedance, and therefore, in such a configuration, the sub-filter is removed as a filtering component since the acoustic resonators are substantially shorted to ground, and therefore the sub-filter has no effect on the filter 300 during transmission of the zero frequency. The resonant frequencies of XL1 and XL2 are usually, but not necessarily, equal, and the resonant frequencies of XH1 and XH2 are equal. The resonant frequencies of the acoustic resonators XL1, XL2 are selected to provide transmission zeroes adjacent the lower edge of the filter passband. XL1 and XL2 may be referred to as "low-edge resonators" because their resonant frequencies are near the lower edge of the filter passband. The acoustic resonators XL1 and XL2 also act as shunt inductors to help match the impedance at the filter ports to the desired impedance value. In subsequent examples of this patent, the impedance of each port of the filter may be matched to 50 ohms when connected to a radio frequency antenna; when the filter is connected to a power amplifier such as a radio frequency transmitter, the impedance of each port of the filter can be matched to 4 ohms; and when connected to a low noise amplifier (e.g., an RF receiver), the impedance of each port of the filter may be matched to 300 ohms. Specific examples of these embodiments are given in fig. 15A-C. In other cases, the impedance may be another value, such as 20 ohms, 100 ohms, or 1000 ohms, if desired. The resonant frequencies of the acoustic resonators XH1, XH2 are selected to provide transmission zeroes at or above the upper edges of the filter passband. XH1 and XH2 may be referred to as "high-side resonators" because their resonant frequencies are close to the high side of the filter passband. Not all matrix filters require high-side resonators XH1 and XH2, for example filters with sub-filters will not pass the relative amplitudes of the signals at these high-side frequencies.

Fig. 3B is a schematic diagram of a sub-filter 350 suitable for use in each of sub-filters 320-1, 320-2, and 320-n of filter 300. The sub-filter 350 comprises three acoustic resonators XA, XB, XC connected in series between a first sub-filter port (SP 1) connectable to FP1 and a second sub-filter port (SP 2) connectable to FP2. The acoustic resonators XA, XB, XC are preferably, but not necessarily, XBARs. The sub-filter 350 comprises two coupling capacitors CA, CB, each coupled between ground and a respective node between two acoustic resonators. It is exemplary that sub-filter 350 includes three acoustic resonators. The sub-filter may have m acoustic resonators, where m is an integer greater than one. A sub-filter with m acoustic resonators comprises m-1 coupling capacitors. The m acoustic resonators of the sub-filter are connected in series between two ports SP1 and SP2 of the sub-filter, and each of the m-1 coupling capacitors is connected between ground and a node between a respective pair of the m acoustic resonators.

Compared to other types of acoustic resonators, XBARs have very high electromechanical coupling (which results in a large difference between the resonance frequency and the anti-resonance frequency), but low capacitance per unit area. The matrix filter architecture, as shown in fig. 3A and 3B, takes advantage of the high electromechanical coupling of XBARs without requiring high resonator capacitance.

Fig. 4 is a graph 400 of the performance 405 of an exemplary embodiment of a matrix filter implemented using XBARs for all acoustic resonators. The performance 405 in graph 400 may be the performance of the transfer function S21 of filter 300 with 3 non-continuous-pass band-

pass filters

1,2 and 3. Specifically, performance 405 includes a solid line, a dashed line, and dashed lines 410, 420, and 430, which are each plots of S21, the filter transfer function of FP1 through FP2 over frequency, where each of lines 410, 420, and 430 are for non-continuous

pass band sub-filters

1,2, and 3, respectively. That is, the solid line 410 is a graph of S21, the FP1 to FP2 individual transfer functions of the sub-filters 1 of the filter as a function of frequency and isolated from the resonance frequency SF 1. The dashed line 420 is the graph of S21, the individual transfer functions FP1 to FP2 of the sub-filters 2 of the filter as a function of frequency and isolated from the resonance frequency SF 2. The dashed line 430 is the graph of S21 with the individual transfer functions FP1 to FP2 of the sub-filters 3 of the filter as a function of frequency and isolated from the resonance frequency SF 3. Since the exemplary filter is asymmetric, the solid, dashed and dotted lines 410, 420 and 430 are not plots of S12.

Fig. 5 is a graph 500 of the passband frequencies of the sub-filters within the exemplary matrix filter of the filter of fig. 3A, the performance of which is shown in fig. 4. The example of graph 500 may be used for reception frequencies for

LTE bands

3, 1, and 7 (from low to high frequencies), with the passband defined above-3 dB. Specifically, P1, P2, and P3 are passband frequencies that are-3 dB higher than the magnitude of the input-output transfer functions of sub-filter 1, sub-filter 2, and sub-filter 3, respectively. The pass bands P1, P2 and P3 are discontinuous in that each pair of adjacent pass bands is separated by a stop band in which the input-output transfer function of the matrix filter is less than-20 dB. For example, the pass bands P1 and P2 are discontinuous because the pair of pass bands are separated by a stop band SB1, which is present where the input-output transfer function S21 of the matrix filter 300 is less than-20 dB. Furthermore, the pass bands P2 and P3 are discontinuous in that the pair of pass bands are separated by a stop band SB2, which stop band SB2 is present where the input-output transfer function S21 of the matrix filter 300 is less than-20 dB.

The matrix filter of fig. 4 and 5 comprises 3 sub-filters with connections between input and output ports that can be switched in and out to provide a large number of passbands for input and output RF communication signals. Each sub-filter may include three XBARs, as shown in fig. 3A and 3B. In other cases, there may be two, four, five, or up to ten sub-filters. Further, each sub-filter may include more than three XBARs and 2 coupling capacitors. Some sub-filters may have m acoustic resonators, where m = four, five, six or up to 10; and a corresponding m-1 coupling capacitors as shown in fig. 3B. In this example and all subsequent examples, filter performance was determined by simulating the filter using the BVD model of XBAR (fig. 2A). It will be appreciated that the concept of 3 sub-filters herein may be extended to only two or up to four, five or up to any number determined by size and routing complexity considerations.

The input-output transfer function of the exemplary filter, as shown in fig. 4, is the vector sum of the input-output transfer functions of three sub-filters, where the three sub-filters have non-contiguous passbands. A non-continuous passband may mean that no single sub-filter input-output transfer function intersects the other sub-filter input-output transfer function at frequencies where both filter S21 transfer functions are above-20 dB. To this end, the input-output transfer functions of

sub-filters

1 and 2 intersect at a frequency slightly below 2GHz, where (a) the S21 of both filters is no higher than-20 dB and (b) the input-output transfer functions of both filters are substantially equal. In this case, "not higher" means low enough to cause no objectionable variation in any of the transfer functions of the sub-filters due to the transfer functions of the different sub-filters of the matrix filter within the pass band of the filter (in this case, the pass band ranges from 1.5 to 3 GHz). The quantitative value of "not higher" may be different in different filter applications. Similar requirements apply to sub-filter 2 and sub-filter 3. In a matrix filter with more than three sub-filters, similar requirements apply to each adjacent (in frequency) sub-filter pair.

In some cases, a "continuous" passband matrix filter describes a matrix filter having a passband that is the sum of the passbands of more than one sub-filter, while a "discontinuous" passband matrix filter describes a matrix filter where each passband is the passband of only one sub-filter. For some switched matrix filters, the pass bands of the "non-contiguous" sub-filters are not adjacent or do not overlap above-20 dB. The matrix filter may also have some continuous sub-filters and other discontinuous sub-filters. For example, it may be a filter having at least one stop band between the pass bands of at least one pair of adjacent sub-filters.

In one example, the lowest-passband, non-continuous-passband sub-filter 1 is the LTE band Rx 3 and has 3 resonators and 2 coupling capacitors. Here, the middle-passband, discontinuous-passband sub-filter 2 is the LTE band Rx 1 and has 5 resonators and 4 coupling capacitors. The highest pass band, non-continuous pass band sub-filter 3 is the LTE band Rx 7, and the sub-filter has 4 resonators and 3 coupling capacitors. The filter may have one or more XL resonators and zero or more XH resonators.

The exemplary matrix filter is asymmetric because the impedances at FP1 and FP2 are different. The impedance of port FP1 may be 50 ohms of the filter input port to match the impedance of the RF antenna. The impedance at port FP2 may be 4 ohms of the filter output port to match the output impedance of a power amplifier, such as an RF transmitter, for example, when filter 300 is used as a transmit filter. In another case, the impedance at port FP2 may be 300 ohms of the filter output port to match the input impedance of a low noise amplifier such as an RF receiver, for example, when filter 300 is used as a receive filter. The vertical dash-dot line identifies the resonant frequency of the XBAR within the exemplary matrix filter. The line labeled "XL" represents the resonant frequency of resonators XL1 and XL2, which is adjacent to the lower edge of the filter passband. Similarly, the line labeled "XL" represents the resonant frequencies of resonators XH1 and XH2, which is adjacent to the upper edge of the filter passband. The two lines labeled "SF1" in fig. 4 separately identify the resonant frequencies of the XBARs within sub-filter 1. The two lines labeled "PBF1" in fig. 5 separately identify the passband frequencies of the XBAR within sub-filter 1. Note that both resonance frequencies are below the center of the pass band. This is because the resonance frequency of the series resonator and the capacitor is higher than the resonance frequency of the isolated resonator. Similarly, the two lines labeled "SF2" identify the resonant frequencies of XBAR within sub-filter 2 and the two lines labeled "SF3" identify the resonant frequencies of XBAR within sub-filter 3. Similarly, the two lines labeled "SF2" identify the resonant frequency and the two lines labeled "PBF2" in fig. 5 identify the passband frequency of the XBAR within sub-filter 2. Finally, the two lines labeled "SF3" in fig. 4 identify the resonant frequencies and the two lines labeled "PBF3" in fig. 5 identify the passband frequencies of the XBAR within the sub-filter 3.

Fig. 6 is a schematic diagram of a matrix filter 600 configured as a duplexer with input and output impedances matched to Radio Frequency Front End (RFFE) elements. The matrix filter 600 includes an array 610 of three sub-filters 620-1, 620-2, 620-n. Sub-filter 1-1 is connected between a first filter port (FP 1) and a second filter port (FP 2). Sub-filter 2-2 and sub-filter 3-3 are connected in parallel between FP1 and the third filter port (FP 3). FP1 is the common or input port of the duplexer, FP2 and FP3 are the branch or output ports. As previously described, sub-filter array 610 is terminated at both ends by XBAR XL and XH.

Fig. 7 is a graph 700 of performance 705 of the example of the matrix filter duplexer 600 of fig. 6. In this example, XL, XH, and the three sub-filters are the same as the corresponding elements of matrix filter 300 of fig. 3A. In fig. 7, solid line 410 below 710 is a plot of S21, the transfer function of FP1 through FP2, as a function of frequency. Dashed line 430 below dashed lines 420 and 720 is a plot of the transfer function of S31, FP1 through FP3, as a function of frequency. Since the exemplary filter is asymmetric, dashed line 420 and dashed line 430 under solid lines 410 and 720, respectively, under 710 are not plots of S12 and S13. The switch matrix filter 600 is exemplary. In most applications, the diplexer will have the same number (two, three or more) of sub-filters in parallel between the common or input port and the two branch ports.

FP1 may be considered a common or input port of the matrix filter duplexer 600. FP2 may be considered a "low band" port and FP3 may be considered a "high band" port. When the matrix filter duplexer is used for a frequency division duplex radio, one of FP2 and FP3 may be a receive or output port of the duplexer, and the other of FP2 and FP3 may be a transmit or output port of the duplexer, depending on whether the frequency allocation is for receive or transmit.

In the second duplexer configuration, which is a variation of the filter 600, the sub-filter 1-1 and the sub-filter 2-2 are connected in parallel between FP1 and FP2. Here, the sub-filter 3-3 is connected between FP1 and FP 3. In this case, the performance graph of the example of the matrix filter duplexer has a graph of a solid line 410 and a broken line 420 as S21; dashed line 430 is shown as a plot of S31 as a function of frequency.

In the third duplexer configuration which is a variation of the filter 600, the sub-filter 1-1 and the sub-filter 3-3 are connected in parallel between FP1 and FP2. Here, the sub-filter 2 620-2 is connected between FP1 and FP 3. In this case, the performance graph of the example of the switch matrix filter duplexer has a solid line 410 and a broken line 430 as a graph of S21; and the dashed line 420 acts as a plot of S31 as a function of frequency.

The duplex filter 600 and both variants are switch matrix filters, as either of the branch ports FP2 or FP3 can be selected or switched as the output of the filter. For example, the sub-filter connections between the input and output ports may be switched in and out to provide a large number of passbands for the input and output radio frequency communication signals. A processor (not shown) may be coupled to and may control the operation of the switches within filter 600, for example, to provide branch port selection.

In any configuration of the duplex filter 600, the impedance at the port FP1 can be 50 ohms of the filter input port to match the impedance of the RF antenna. The impedance of each of ports FP2 and FP3 may be 4 ohms of the filter output port to match the output impedance of a power amplifier such as an RF transmitter; or it may be 300 ohms of the filter output port to match the input impedance of a low noise amplifier, such as an RF receiver. In some cases, the impedance at port FP2 is the same as the impedance at FP 3. In other cases, they are different.

Fig. 8 is a schematic diagram of a matrix triplexer 800 using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements. The matrix filter 800 includes an array 810 of three sub-filters 820-1, 820-2, 820-n. Sub-filter 1 820-1 is connected between a first filter port (FP 1) and a second filter port (FP 2). Sub-filter 2 820-2 is connected between FP1 and the third filter port (FP 3). Sub-filter 3 820-3 is connected between FP1 and the fourth filter port (FP 4). As before, the sub-filter array 810 is terminated at both ends by XBAR XL and XH. FP1 is the common or input port of the multiplexer and FP2, FP3 and FP4 are the branch or output ports of the multiplexer. The multiplexer may have more than three branch ports. A multiplexer having two branch ports is commonly referred to as a "diplexer", and a multiplexer having three branch ports may be referred to as a "triplexer".

Fig. 9 is a performance graph 900 of a functional example of the embodiment of the triplexer 800 of fig. 8. In this example, XL, XH, and the three sub-filters are the same as the corresponding elements of matrix filter 300 of fig. 3A. In fig. 9, the solid line below 910 is a graph of S21, the transfer function of FP1 to FP2, as a function of frequency. The dashed line below 920 is a plot of the transfer function of S31, FP1 through FP3, as a function of frequency. The dashed line below 930 is a plot of the transfer function of S41, FP1 through FP4, as a function of frequency. Since the exemplary filter is asymmetric, the solid line below 910, the dashed line below 920, and the dashed line below 930 are not plots of S12, S13, and S14, respectively.

FP1 can be considered a common or input port of the matrix filter. FP2 may be considered a "low band" port, FP3 may be considered a "mid band" port, and FP4 may be considered a "high band" port. When the matrix filter is used for a Frequency Division Duplex (FDD) radio, one of FP2, FP3 and FP4 may be a receive or output port, while another of FP2, FP3 and FP4 may be a transmit or output port, depending on whether the allocated frequency is used for reception or transmission. In other cases, in an FDD radio, two of FP2, FP3 and FP4 may be receive or output ports and another of FP2, FP3 and FP4 may be transmit or output ports, or vice versa.

In an additional multiplexer configuration that is a variation of filter 800, any one or more of sub-filter 1 820-1, sub-filter 2 820-2, and sub-filter 3 820-3 may be connected in parallel between FP1 and FP2, FP3, and/or FP4. In this case, the performance diagram of the example of the matrix filter duplexer has the corresponding lines of the solid, dashed and dashed lines 410, 420 and/or 430 as graphs of S21, S31 and/or S41 as a function of frequency.

The multiplexer filter 800 and both variants may be a switch matrix filter in that any one or more of the ports FP2, FP3 and FP4 may be selected or switched as the output of the filter. For example, the sub-filter connections between the input and output ports may be switched in and out to provide a large number of passbands for the input and output radio frequency communication signals. In one example, a switched XBAR matrix filter with 3 sub-filters for

LTE bands

3, 1, and 7 provides a multi-passband reconfigurable filter that can be configured for all 7 possible states: only 1, only 3, only 7, 1+3, 1+7, 3+7, and +3+7. The low loss of this filter is due to its matrix architecture, e.g. due to the position of the switches and due to the fact that no inductor is needed for the filter. A processor (not shown) may be coupled to the switches within filter 800 and may control the operation of the switches to, for example, select sub-filters and ports FP2, FP3, and FP4.

In any configuration of the triplexer 800, the impedance at port FP1 may be 50 ohms of the filter input port to match the impedance of the RF antenna. The impedance of each of ports FP2, FP3 and FP4 may be 4 ohms of the filter output port to match the output impedance of a power amplifier such as an RF transmitter; or it may be 300 ohms of the filter output port to match the input impedance of a low noise amplifier, such as an RF receiver. In some cases, the impedance is the same for all ports FP2, FP3, and FP4. In other cases, the impedance of one of the 3 ports is different from the impedance of the other two ports.

Fig. 10A is a schematic diagram of a reconfigurable switch-matrix filter 1000 using XBARs with input and output impedances matched to Radio Frequency Front End (RFFE) elements. The reconfigurable switch matrix filter 1000 includes an array 1010 of n sub-filter/switch circuits 1020-1, 1020-2, 1020-n connected in parallel between a first filter port (FP 1) and a second filter port (FP 2), where n is an integer greater than one. In the examples that follow, n =3. In other cases, n may be greater than 3 as needed to provide the required bandwidth for reconfigurable matrix filter 1000. Each sub-filter/switch circuit functions as a discontinuous bandpass filter that can be selectively enabled (i.e., connected between FP1 and FP 2) or disabled (i.e., not connected between FP1 and FP 2). As previously described, the array of sub-filter/switch circuits 1010 is terminated at both ends by XBAR XL and XH.

The sub-filter/switch circuits 1020-1, 1020-2, 1020-n have discrete pass-bands such that the bandwidth of the matrix filter 1000 when all sub-filter/switch modules are enabled is not equal to the sum of the bandwidths making up the sub-filters, but instead has three separate and independent pass-bands separated by stop-bands that exist where the input-output transfer function of the matrix filter 300 is less than-20 dB. One or more sub-filter/switch circuits may be disabled to adjust the matrix filter bandwidth or to insert a notch or stop band within the entire pass band, e.g., to provide the matrix filter with a desired non-continuous pass band. The filter 1000 and/or the sub-filters may be RF filters that pass the frequency band defined by the 5G NR standard.

FIG. 10B is a schematic diagram of a sub-filter/switch circuit 1050 suitable for use in the sub-filter/switch circuits 1020-1, 1020-2 and 1020-n of FIG. 10A. The sub-filter/switch circuit 1050 includes three acoustic resonators X1, X2, X3 connected in series between a first sub-filter port (SP 1) and a second sub-filter port (SP 2), and coupling capacitors C1, C2, the coupling capacitors C1, C2 being connected to ground from a junction point between adjacent acoustic resonators. It is exemplary that sub-filter/switch circuit 1050 include three acoustic resonators, and that the sub-filter/switch circuit may have more than three acoustic resonators. When the sub-filter/switch circuit comprises more than three acoustic resonators, the number of coupling capacitors will be one less than the number of acoustic resonators. The acoustic resonators X1, X2, X3 are preferably, but not necessarily, XBARs.

The sub-filter/switch circuit 1050 includes a switch SW in series with the acoustic resonator X2. When switch SW is closed, the sub-filter/switch circuit operates as a sub-filter applicable to any of the previous examples. In this case, the sub-filter/switch circuit connection between the input and output ports is switched on to provide the passband of the sub-filter for the input and output radio frequency communication signals. When switch SW is open, the sub-filter/switch circuit presents the appropriate impedance to SP1 and SP2, but with an open input-output transfer function. In this case, the sub-filter/switch circuit connection between the input and output ports is cut off and the pass band of the sub-filter is not provided for the input and output RF communication signals. When the sub-filter/switch circuit comprises more than three acoustic resonators, the switch may be in series with any acoustic resonator except the two acoustic resonators connected to the two sub-filter ports. In other words, the switch may be in series with any "middle acoustic resonator" located in the middle of the resonator string, but not with the two "end acoustic resonators" located at the ends of the string. In some cases, filter 1000 may be described as having respective output ports SP2 of all its sub-filters connected to a common output port FP2.

Fig. 10C is a schematic diagram of a sub-filter/switch circuit 1075 suitable for use in the sub-filter/switch circuits 1020-1, 1020-2 and 1020-n of fig. 10A. The sub-filter/switch circuit 1075 includes three acoustic resonators X1, X2, X3 connected in series between a first sub-filter port (SP 1) and a second sub-filter port (SP 2), and coupling capacitors C1, C2, the coupling capacitors C1, C2 being grounded from a junction between adjacent acoustic resonators. It is exemplary that the sub-filter/switch circuit 1075 includes three acoustic resonators, and the sub-filter/switch circuit may have more than three acoustic resonators. When the sub-filter/switch circuit comprises more than three acoustic resonators, the number of coupling capacitors will be one less than the number of acoustic resonators. The acoustic resonators X1, X2, X3 are preferably, but not necessarily, XBARs.

The sub-filter/switch circuit 1075 includes a switch SW1 in parallel with the first parallel capacitor C1 and a switch SW2 in parallel with the last parallel capacitor C2. When switches SW1 and SW2 are open, the sub-filter/switch circuit operates as a sub-filter suitable for any of the previous examples. In this case, the sub-filter/switch circuit connection between the input and output ports is turned on to provide the passband of the sub-filter for the input and output RF communication signals. When switches SW1 and SW2 are closed, the sub-filter/switch circuit presents the appropriate impedance to SP1 and SP2, but with an open input-output transfer function. In this case, the sub-filter/switch circuit connection between the input and output ports is disconnected and the pass band of the sub-filter is not provided for the input and output RF communication signals. Switches SW1 and SW2 may be used instead of the switch SW of fig. 10B to switch the input and output of some sub-filters between the input and output ports.

When the sub-filter/switch circuit comprises more than two parallel capacitors, the switch is connected in parallel with two parallel capacitors next to the acoustic resonator connected to the two sub-filter ports. In other words, the switch is connected in parallel with the "first parallel capacitor" and the "last parallel capacitor", not in the middle of the resonator string, but inside the two "end acoustic resonators" at the ends of the string. For example, a first switch is connected in parallel with a first capacitor parallel element between the XBAR series element immediately adjacent to the input port of the filter and the XBAR series element remote from the input port; the second switch is in parallel with the last capacitor parallel element between the XBAR series element immediately adjacent the output port of the filter and the XBAR series element further from the output port.

Fig. 11 is a graph 1100 of performance 1105 of an example of the reconfigurable switch matrix filter 1000 of fig. 10. In this example, XL, XH, and the elements within the three sub-filter/switch circuits are the same as the corresponding elements of matrix filter 300 of fig. 3A. In fig. 11, the solid line below 1110 is a graph of the transfer function of S21, i.e., port 1 to port 2 of the filter, as a function of frequency when sub-filter/switch circuit 1 is enabled and sub-filter/

switch circuits

2 and 3 are disabled. The dashed line below 1120 is a plot of S21 versus frequency when sub-filter/switch circuit 2 is enabled and sub-filter/

switch circuits

1 and 3 are disabled. The dashed line below 1130 is a plot of S21 versus frequency when sub-filter/switch circuit 3 is enabled and sub-filter/

switch circuits

1 and 2 are disabled. The sum of the two curves below 1110 and 1130 is not shown, but we can easily imagine,

is the port 1 to port 2 transfer function as a function of frequency when the sub-filter/

switch circuits

1 and 3 are enabled and the sub-filter/switch circuit 2 is disabled. The sum of the two curves below 1110 and 1120 is the port 1 to port 2 transfer function as a function of frequency when sub-filter/

switch circuits

1 and 2 are enabled and sub-filter/switch circuit 2 is disabled. The sum of the two curves below 1110 and 1130 is the port 1 to port 2 transfer function as a function of frequency when sub-filter/

switch circuits

1 and 3 are enabled and sub-filter/switch circuit 2 is disabled. The sum of the two curves below 1120 and 1130 is the port 1 to port 2 transfer function as a function of frequency when sub-filter/

switch circuits

2 and 3 are enabled and sub-filter/switch circuit 1 is disabled. 1110. The sum of the three curves below 1120 and 1130 is the port 1 to port 2 transfer function as a function of frequency when the sub-filter/

switch circuits

1,2 and 3 are enabled. The open input-output transfer function is the port 1 to port 2 transfer function that varies with frequency when all sub-filter/

switch circuits

1,2 and 3 are disabled. All eight filter configurations may be achieved by enabling various combinations of three sub-filter/switch circuits. A processor (not shown) may be connected to and include operation of switches within

filters

1000, 1050, and/or 1075 to, for example, select sub-filters.

In any configuration of

filters

1000, 1050, and/or 1075, the impedance at port FPl may be 50 ohms of the filter input port to match the impedance of the RF antenna. The impedance at port FP2 may be 4 ohms of the filter output port to match the output impedance of a power amplifier such as an RF transmitter; or it may be 300 ohms of the filter output port to match the input impedance of a low noise amplifier, such as an RF receiver.

The sub-filter/switch circuit connections between the input and output ports of

filters

1000, 1050, and/or 1075 may be switched to select a desired pass band and a desired impedance at port FP2. For example, the switch SW of fig. 10B may be used to select one of the sub-filters 1050 of the filter 1000, the sub-filter 1050 having a desired pass band and a desired impedance for a transmit signal from a transmitter to match the output impedance of the transmitter's power amplifier. In addition, the switch SW of fig. 10B may be used to select one of the sub-filters 1050 of the filter 1000, the sub-filter 1050 having a desired pass band and a desired impedance for signals received from the antenna to be transmitted to the receiver to match the input impedance of the low noise amplifier of the receiver. In addition, switches SW1 and SW2 of fig. 10C may be used to select one of the sub-filters 1075 of filter 1000, the sub-filter 1075 having a desired pass band and a desired impedance as described by switch SW.

Fig. 12 is a schematic block diagram of a Frequency Division Duplex (FDD) radio 1200 having input and output impedances matched to Radio Frequency Front End (RFFE) elements. FDD radios transmit and receive in different frequency ranges in defined communication bands. The transmit and receive frequency ranges are typically, but not necessarily, adjacent. The radio apparatus 1200 comprises an antenna 1205, a matrix filter duplexer 1210 having a common filter port FP1 configured to be connected to the antenna 1205, a transmit filter port FP3 coupled to an output port Out of a transmitter 1220, and a receive filter port FP2 coupled to an input port In of a receiver 1225.

Radio 1200 is configured for operation in a designated communications band. The matrix filter duplexer 1210 includes a receive filter coupled between FP1 and FP2 and a transmit filter coupled between FP1 and FP 3. The receive filter may include one or more receive sub-filters. The transmit filter may include one or more transmit sub-filters. The transmit filter must be compatible with the RF power generated by the transmitter 1220. The matrix filter duplexer 1210 may be implemented using acoustic resonators, which may be XBARs.

The matrix filter duplexer 1210 may be similar to two of the matrix filters 300 of fig. 3-B. 3A-B. Here, each of the filters 300 is a transmit or receive filter, having an equal number of sub-filters turned on for each transmit or receive filter. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of the filter 300; the transmit port FP3 of the matrix filter duplexer 1210 is port FP2 of the transmit filter version of the filter 300; the receive port FP2 of the matrix filter duplexer 1210 is the port FP2 of the receive filter version of the filter 300. The two filters 300 may have different passbands. In this case, the port FP1 may be common to both filters 300.

The matrix filter duplexer 1210 may be similar to the matrix duplexer 600 of fig. 6, with the same number of sub-filters in the transmit and receive filters. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of the matrix duplexer 600; the transmit or output port FP3 may be either FP2 or FP3 of the matrix duplexer 600; the receive or output port FP2 may be the other of FP2 and FP3 of the matrix duplexer 600.

In another case, the matrix filter duplexer 1210 may be similar to the matrix triplexer filter 800 of fig. 8. There are the same number of sub-filters in the transmit and receive filters. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of the matrix triplexer 800; the transmit or output port FP3 may be any of FP2, FP3 or FP4 of matrix triplexer 800; the receive or output port FP2 may be any of FP2, FP3 or FP4 of matrix triplexer 800.

Further, the matrix filter duplexer 1210 may be similar to two of the matrix filters 1000 of fig. 10A-C. Here, each of the filters 1000 is a transmit or receive filter, with an equal number of sub-filters turned on for each transmit or receive filter. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of each of the matrix filters 1000; the transmit port FP3 of the matrix filter duplexer 1210 is the port FP2 of the transmit filter version of the filter 1000 based on the switching on and off of the sub-filters of the matrix filter 1000; the receive port FP2 of the matrix filter duplexer 1210 is the port FP2 of the receive filter version of the filter 1000 based on the switching on and off of the sub-filters of the matrix filter 1000. In this case, the port FP1 may be common to both filters 1000.

It is also contemplated that the matrix filter duplexer 1210 may be similar to a combination of two of the

filters

300, 600, 800, and 1000, with an equal number of sub-filters turned on for each transmit or receive filter. Here, port FP1 of the matrix filter duplexer 1210 is a common port; a transmitting port FP3 of the matrix filter duplexer 1210 is a transmitting port; the receive port FP2 of the matrix filter duplexer 1210 is a receive port of one of the

filters

300, 600, 800 and 1000. In this case, the port FP1 may be common to the combination of filters.

In any configuration of the filter 1210, the impedance at port FPl is 50 ohms to match the impedance of the RF antenna 1205. The impedance at port FP3 matches 1220 the output impedance of the Power Amplifier (PA) of the RF transmitter. For example, the impedance at port FP3 may be about 4 ohms. The impedance at port FP2 matches the input impedance of the Low Noise Amplifier (LNA) of the RF receiver 1225. The impedance at port FP2 may be an impedance that minimizes the noise figure of the LNA. For example, the impedance may be about 300 ohms.

Fig. 13 is a schematic block diagram of a three-band diversity receiver 1300 using a matrix triplexer with input and output impedances matched to radio frequency front-end (RFFE) elements. A triple-band diversity radio receiver receives in three different frequency ranges corresponding to three communication bands. The receiver 1300 includes an antenna 1305, a matrix filter triplexer 1310 having a common filter port FP1 configured to be connected to the antenna 1305, a first output or receive filter port FP2 coupled to an input port In1 of the receiver 1320, a second output or receive filter port FP3 coupled to an input port In2 of a receiver 1325, a third output or receive filter port FP4 coupled to an input port In3 of a receiver 1330.

Receiver 1300 is configured for operation in a designated communication band. Matrix filter triplexer 1310 includes a coupler between FP1 and FP2; between FP1 and FP 3; and a receive filter in each of FP1 and F4. The receive filter includes a discontinuous passband receive sub-filter. Matrix filter triplexer 1310 may be implemented using acoustic resonators, which may be XBARs.

Matrix filter triplexer 1310 may be similar to three of matrix filters 300 of fig. 3A-B. 3A-B. Here, each of the filters 300 is a reception filter having an equal number of sub-filters turned on for each reception filter. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of each filter 300; and the FP2, FP3, and FP4 ports of matrix filter triplexer 1310 may be FP2 of each of the three receive filter versions of filter 300. The three filters 300 may have different passbands. In this case, the port FP1 may be common to the three filters 300.

Matrix filter triplexer 1310 may be matrix triplexer 800 of fig. 8. The FP1, FP2, FP3, and FP4 ports of matrix filter triplexer 1310 may be the FP1, FP2, FP3, and FP4 ports of matrix multiplexer 800.

In another case, matrix filter triplexer 1310 may be similar to three of reconfigurable switch filters 1000 of fig. 10A-C, with each of the three receive filters having an equal number of sub-filters. The FP1 port of matrix filter triplexer 1310 may be FP1 of three reconfigurable switch filters 1000;

and the FP2, FP3, and FP4 ports of matrix filter triplexer 1310 may be FP2 of each of the three reconfigurable switch filters 1000, where the three filters 1000 may have different passbands based on the turning on and off of the sub-filters of the three matrix filters 1000. In this case, port FP1 may be common to all three filters 1000.

It is also contemplated that matrix filter triplexer 1310 may be similar to a combination of any three of

filters

600, 800, and 1000, with an equal number of sub-filters switched on for each receive filter. Here, port FP1 of matrix filter triplexer 1310 is a common port; each of ports FP2, FP3, and/or FP4 of matrix filter triplexer 1310 is a receive port of one of

filters

600, 800, and 1000. In this case, the port FP1 may be common to the filter combination.

In any configuration of the filter 1310, the impedance at the port FP1 is 50 ohms of the filter input port, which matches the impedance of the RF antenna 1305. The impedances at ports FP2, FP3, and FP4 are matched to the input impedance of the Low Noise Amplifier (LNA) of each of the

RF receivers

1320, 1325, and 1330, respectively. The impedance at each port FP2, FP3, FP4 may be an impedance that minimizes the noise figure of the corresponding LNA. The impedance at each port may be, for example, about 300 ohms. The impedances at the three ports may be different to accommodate the characteristics of the LNAs of

RF receivers

1320, 1325 and 1330.

Fig. 14 is a schematic block diagram of a dual band split radio using a matrix multiplexer filter with input and output impedances matched to Radio Frequency Front End (RFFE) elements. Radio 1400 transmits and receives in different frequency ranges having defined communication bands. The transmit and receive frequency ranges are typically, but not necessarily, adjacent. Radio 1400 includes an antenna 1405, a matrix filter multiplexer 1410 having a common filter port FP1 configured to connect to antenna 1405; transmit filter ports FP2 and FP3 coupled to output ports Out1 and Out2 of

transmitters

1420 and 1425, respectively; receive filter ports FP4 and FP5 coupled to input ports In1 and In2 of

receivers

1430 and 1435, respectively.

Radio 1400 is configured to operate in a designated communication band. Matrix filter multiplexer 1410 includes a first transmit filter coupled between FP1 and FP2; a second transmit filter coupled between FP1 and FP 3; a first receive filter coupled between FP1 and FP 4; a second receive filter coupled between FP1 and FP5. The transmit filter may include one or more transmit sub-filters. The receive filter may include one or more receive sub-filters. The transmit filter is compatible with the RF power generated by

transmitters

1420 and 1425. The matrix filter multiplexer 1410 may be implemented using acoustic resonators, which may be XBARs.

The matrix filter multiplexer 1410 may be similar to the four matrix filters 300 of fig. 3A-B. Here, each of the filters 300 is a transmit or receive filter, with an equal number of sub-filters switched on for each transmit or receive filter. Here, the common filter port FP1 of the matrix filter multiplexer 1410 is FP1 of the filter 300; the transmit ports FP2 and FP3 of the matrix filter duplexer 1210 are port FP2 of the transmit filter version of the filter 300; and the receive ports FP4 and FP5 of the matrix filter duplexer 1210 are port FP2 of the receive filter version of the filter 300. The transmit and receive filter 300 pairs may have different passbands. In this case, the port FP1 may be common to the four filters 300.

The matrix filter multiplexer 1410 may be similar to two of the matrix duplexers 600 of fig. 6. 6 have the same number of sub-filters in the transmit and receive filters. Here, the common filter port FP1 of the matrix filter multiplexer 1410 is FP1 of the two matrix duplexers 600; the transmit or output ports FP2 and FP3 may be either FP2 or FP3 of the two matrix duplexers 600; and the receive or output ports FP4 and FP5 may be the other of FP2 and FP3 of the two matrix duplexers 600. The transmit and receive filter pairs of filter 600 may have different passbands. In this case, the port FP1 may be common to the four filters 600.

In another case, the matrix filter multiplexer 1410 may be similar to the matrix triplexer multiplexer filter 800 of fig. 8. Fig. 8 has 4 sub-filters (e.g., one quadplexer) instead of three sub-filters as the transmit and receive filters. This filter adds a sub-filter 4 (not shown), the sub-filter 4 being similar to the other sub-filters but being connected to the input port FP1 and having an output port FP5. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of the matrix triplexer 800; the transmit or output ports FP2 and FP3 of matrix filter duplexer 1210 may be any two of FP2, FP3, FP4, or FP5 of matrix triplexer 800; and receive or output ports FP4 and FP5 may be two other of FP2, FP3, FP4, or FP5 of matrix triplexer 800. The transmit and receive filter pairs of filter 600 may have different passbands.

Further, the matrix filter multiplexers 1410 may be similar to four of the matrix filters 1000 of fig. 10A-C. Here, each of the filters 1000 is a transmit or receive filter, with an equal number of sub-filters turned on for each transmit or receive filter. Here, the common filter port FP1 of the matrix filter duplexer 1210 is FP1 of each filter 1000; the transmit ports FP2 and FP3 of the matrix filter multiplexer 1410 are ports FP2 of the transmit filter version of the filter 1000 based on the switching on and off of the sub-filters of the matrix filter 1000; and the receive ports FP4 and FP5 of the matrix filter multiplexer 1210 are the ports FP2 of the receive filter version of the filter 1000 based on the switching on and off of the sub-filters of the matrix filter 1000. The transmit and receive filter pairs of filter 1000 may have different passbands. In this case, the port FP1 may be common to the four filters 1000.

It is also contemplated that matrix filter multiplexer 1410 may be similar to a combination of two or four of

filters

300, 600, 800, and 1000, with an equal number of sub-filters turned on for each transmit or receive filter. Here, port FP1 of matrix filter multiplexer 1410 is a common port; the transmit ports FP2 and FP3 of the matrix filter multiplexer 1410 are the transmit ports of the transmit filters, respectively; the receive ports FP4 and FP5 of the matrix filter multiplexer 1410 are receive ports of receive filters of one of the

filters

300, 600, 800 and 1000, respectively. In this case, the port FP1 may be common to the combination of filters.

In any configuration of the filter 1410, the impedance at port FP1 is 50 ohms of the filter input port, which matches the impedance of the RF antenna 1405. The impedance at each of the ports FP2 and FP3 is matched to the output impedance of the Power Amplifiers (PAs) of the

RF transmitters

1420 and 1425. The impedance at each port FP4 and FP5 is matched to the input impedance of the Low Noise Amplifiers (LNAs) of the

RF receivers

1430 and 1435, respectively.

The four transmit and receive filters of multiplexer 1410 may transmit and receive on various frequency bands. For example, each of the four transmit and receive filters within matrix multiplexer filter 1410 would use a separate bandpass. In the example of fig. 14, the transmit filter between FP1 and FP2, and the receive filter between FP1 and FP4 may pass uplink and downlink frequencies of LTE band 1; while the transmit filter between FP1 and FP3 and the receive filter between FP1 and FP5 pass the uplink and downlink of LTE band 3. Specifically, the transmission filter between FP1 and FP2 passes LTE band 1Tx with frequency 1900-1980 MHz; the receiving filter between FP1 and FP4 passes through the LTE band 1Rx with frequencies 2110-2170; the transmission filter between FP1 and FP3 passes the LTE frequency band 3Tx with the frequency of 1710-1785 MHz; the receive filter between FP1 and FP5 passes LTE band 1Rx at frequencies 1805-1880.

Fig. 15A is a schematic diagram of a matrix filter 1500 using acoustic resonators with input and output impedances matched to Radio Frequency Front End (RFFE) elements. Fig. 15A is a specific example of fig. 3A-B. The matrix filter 1500 includes an array 1510 of 3 sub-filters 1520-1, 1520-2, and 1520-3 connected in parallel between an input filter port (FP 1) and an output filter port (FP 2). The sub-filters 1520-1, 1520-2, and 1520-3 have non-contiguous pass bands such that the bandwidth of the matrix filter 1500 is not equal to the sum of the bandwidths of the constituent sub-filters, but rather have three separate and independent pass bands, the pass bands being separated by stop bands that exist where the input-output transfer function of the matrix filter 1500 is less than-20 dB.

Each of filter 1500 and/or sub-filters 1520-1, 1520-2, and 1520-3 may be an RF filter that passes a frequency band defined by the 5G NR standard. The sub-filter array 1510 is terminated at the input or FP1 and output or FP2 ends by acoustic resonators that create "transmission zeros" for the filter 300 as described above.

Each of the sub-filters 1520-1, 1520-2, and 1520-3 includes three acoustic resonators XA, XB, XC connected in series between FP1 and FP1. The acoustic resonators XA, XB, XC are preferably, but not necessarily, XBARs. Each sub-filter comprises two coupling capacitors CA, CB, each coupled between ground and a respective node between the two acoustic resonators. The acoustic resonators XL1 and XL2 of filter 1500 also act as shunt inductors to help match the impedance at the filter ports to the desired impedance values.

The filter 1500 has an input port FP1 impedance of 50 ohms and an output port FP2 impedance of 4 ohms or 300 ohms. When connected to an RF antenna, the impedance at FP1 can be matched to 50 ohms. The impedance at FP2 may be matched to 4 ohms when connected to a power amplifier such as an RF transmitter, and may be matched to 300 ohms when connected to a low noise amplifier such as an RF receiver.

The description of FP1 as the input port and FP2 as the output port may be reversed, for example, when FP2 is connected to a low noise amplifier or RF receiver. The sub-filters 1520-1, 1520-2, and 1520-3 may each pass various frequency bands, as described herein. In some cases, separate bandpass may be used for each, as described in any of FIGS. 4-5,7,9, and 11-14.

Fig. 15B shows the specific component characteristics of the first example of fig. 15A, with the input port FP1 impedance of 50 ohms and the output port FP2 impedance of 4 ohms. In this case, FP1 may be matched to 50 ohms when connected to an RF antenna, while the impedance at FP2 may be matched to 4 ohms when connected to a power amplifier such as an RF transmitter. Fig. 15B shows that the characteristics of the maximum capacitance (resonator "X" C0 value and coupling capacitor "C0 value) are closer to the 4 ohm port FP2 than to FP1. For example, the capacitance of the X3 resonator is greater than the capacitance of the X1 or X2 resonator. Further, the capacitance of the C2 capacitor is larger than that of the C1 capacitor. Finally, the capacitances of the H2 and L2 resonators are greater than the capacitances of the H1 and L1 resonators. The passband of the example of fig. 15B of filter 1500 may be any of a variety of passband frequencies for FP1 matched to 50 ohms and FP2 matched to 4 ohms as described herein.

Fig. 15C shows the specific component characteristics of the second example of fig. 15A, with an input port FP2 impedance of 300 ohms and an output port FP1 impedance of 50 ohms. In this case, FP1 may be matched to 50 ohms when connected to an RF antenna, while the impedance at FP2 may be matched to 300 ohms when connected to a low noise amplifier such as an RF receiver. Fig. 15B shows those with the largest capacitances (resonator "X" C0 value and coupling capacitor "C0 value) characterized closer to the 50 ohm port FP1 than to FP2. For example, the capacitance of the X1 resonator is greater than the capacitance of the X2 or X3 resonators. Further, the capacitance of the C1 capacitor is larger than the capacitance of the C2 capacitor. Finally, the capacitances of the H1 and L1 resonators are greater than the capacitances of the H2 and L2 resonators. The passband of the example of fig. 15C of filter 1500 may be any of a variety of passband frequencies for FP1 matched to 50 ohms and FP2 matched to 300 ohms as described herein.

For certain embodiments herein, port FP1 may be described as a common or filter input port of a transmit or receive filter between the input and output ports of the matrix filter herein. When the impedance of the port matches the output impedance of a power amplifier, e.g., an RF transmitter, the port FP2, FP3, FP4, or FP5 may be described as a transmit or filter output port of the transmit filter between the input and output ports of the matrix filter herein. When the impedance of the port matches the input impedance of a low noise amplifier, such as an RF receiver, the port FP2, FP3, FP4, or FP5 may be described herein as a receive or filter output port of a transmit filter between the input and output ports of the matrix filter.

In some embodiments, the description herein of impedance values, such as 50 ohms, 4 ohms, and 300 ohms, may vary significantly to meet RFFE requirements. Although the description herein includes impedances that may be 50 ohms matched to the impedance of the RF antenna, 300 ohms matched to the input impedance of a Low Noise Amplifier (LNA), and 4 ohms matched to the output impedance of a Power Amplifier (PA), it will be appreciated that various other impedances may be used to match the antenna, LNA, and/or PA.

One key advantage of the matrix filter herein is the ability to set the input and/or output impedance of the filter over a wide range to provide matching to Radio Frequency Front End (RFFE) components such as antenna (Ant), power Amplifier (PA) and low noise amplifier (LN). By matching the impedance to that of RFFE, the matrix filter herein has input and output impedances that minimize the noise figure from Ant, receiver LNA and transmitter PA. Since the matrix filter has an impedance matched to RFFE, no external impedance matching or switching is required. Further, acoustic resonator matrix filter topologies herein, such as

filters

300, 600, 800, and/or 1000; radios 1200 and/or 1400; receiver 1300 may reduce the size of the resonators in the filter, thereby: the assembly and manufacturing cost of the filter is reduced; providing a filter having an achievable impedance transformation to match impedances at the filter input and output; and provides a minimum noise figure matched filter for the LNA connected to the output without any matching inductors.

Ending phrase

Throughout the specification, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and processes disclosed or claimed. Although many of the examples provided herein involve specific combinations of method acts or system elements, it should be understood that those acts and those elements may be combined in other ways to accomplish the same objectives. With regard to flow diagrams, additional steps and fewer steps may be taken, and the illustrated steps may be combined or further refined to implement the methods described herein. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments.

As used herein, "plurality" refers to two or more. As used herein, a "set" of items may include one or more of such items. As used herein, the terms "comprising," "including," "carrying," "having," "containing," "involving," and the like, whether in the written detailed description or in the claims, are to be construed as open-ended, i.e., to mean including but not limited to. With respect to the claims, the transition phrases "consisting of and" consisting essentially of "\8230303030the" are closed or semi-closed transition phrases. Ordinal terms such as "first," "second," "third," etc., used in the claims are used to modify a claim element and do not by itself connote any priority, precedence, or order of one claim element over another or the order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a same name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. As used herein, "and/or" means that the listed items are alternatives, but alternatives also include any combination of the listed items.

Claims

1. A matrix filtering duplexer comprising:

a receive matrix filter coupled between the receive port and the antenna port; and

a transmit matrix filter coupled between the antenna port and the transmit port, wherein

The impedance at the receive port is matched to the input impedance of a Low Noise Amplifier (LNA),

the impedance at the transmit port is matched to the output impedance of a Power Amplifier (PA), an

The impedance at the antenna port is matched to the impedance of the antenna.

2. The matrix filter duplexer of claim 1,

the impedance at the receive port is 300 ohms of the filter output port, which matches the input impedance of the Low Noise Amplifier (LNA) of the RF receiver,

the impedance at the transmit port is 4 ohms of the filter output port, which matches the output impedance of the Power Amplifier (PA) of the RF transmitter, and

the impedance at the antenna port is 50 ohms of the filter input port, which matches the impedance of a Radio Frequency (RF) antenna.

3. The matrix filter duplexer of claim 1, wherein the receive matrix filter and the transmit matrix filter each comprise:

two or more sub-filters connected between the filter antenna port and a respective filter output port, each sub-filter comprising a ladder circuit having n series elements of laterally excited thin film bulk acoustic resonators (XBAR) and n-1 parallel elements of capacitance, wherein n, the order of the sub-filter, is an integer greater than 2.

4. The matrix filter duplexer of claim 3, wherein the two or more sub-filters have non-contiguous passbands, and wherein each of the non-contiguous passbands is a passband of only one sub-filter.

5. The matrix filter duplexer of claim 3, wherein each of the two or more sub-filters has a non-continuous pass band separated by a stop band, the stop band being present if an input-output transfer function of the matrix filter is less than-20 dB.

6. The matrix filter duplexer of claim 3,

the XBAR series element comprises a first end XBAR connected to the first sub-filter port, a second end XBAR connected to the second sub-filter port, and one or more intermediate XBARs connected between the first and second end acoustic resonators.

7. The matrix filter duplexer of claim 3,

a radio frequency signal applied to the transmit port or the antenna port excites a primary shear acoustic mode in the XBAR series element.

8. A matrix filter multiplexer, comprising:

first and second receive matrix filters coupled between the first and second receive ports and antenna ports;

and

first and second transmit matrix filters coupled between the antenna port and first and second transmit ports,

wherein

The impedances at the first and second receive ports are matched to the input impedance of the low noise amplifier,

the impedances at the first and second transmit ports are matched to the output impedance of the power amplifier, and

the impedance at the antenna port is matched to the impedance of the antenna.

9. The matrix filter multiplexer of claim 8,

an impedance at the first and second receive ports of 300 ohms of the filter output port, the impedance matching an input impedance of Low Noise Amplifiers (LNAs) of the first and second radio frequency receivers,

the impedance at the first and second transmit ports is 4 ohms of the filter output port, which impedance matches the output impedance of the Power Amplifiers (PAs) of the first and second radio frequency transmitters, and

10. The matrix filter multiplexer of claim 8 wherein the first and second receive matrix filters and the first and second transmit matrix filters each comprise:

11. The matrix filter multiplexer of claim 10 wherein the two or more sub-filters have noncontiguous passbands, and wherein each of the noncontiguous passbands is a passband of only one sub-filter.

12. The matrix filter multiplexer of claim 10, wherein each of the two or more sub-filters has a non-continuous pass band separated by a stop band, the stop band being present if an input-output transfer function of the matrix filter is less than-20 dB.

13. The matrix filter multiplexer of claim 10 wherein the XBAR series elements comprise a first end XBAR connected to a first sub-filter port, a second end XBAR connected to a second sub-filter port, and one or more intermediate XBARs connected between the first and second end acoustic resonators.

14. The matrix filter multiplexer according to claim 10,

a radio frequency signal applied to one of the first transmit port, the second transmit port, or the antenna port excites a primary shear acoustic mode in the XBAR series element.

15. A matrix filter, comprising:

a filter input port; and

two or more sub-filters connected between the filter input port and a respective filter output port, each sub-filter comprising a ladder circuit having n series elements of laterally excited thin film bulk acoustic resonators (XBAR) and n-1 parallel elements of capacitance, where n, the order of the sub-filter, is an integer greater than 2, wherein

The impedance at the output ports of the first plurality of respective filters is matched to the input impedance of the low noise amplifier,

the impedance at the output ports of the second plurality of respective filters is matched to the output impedance of the power amplifier, and

the impedance at the input port matches the impedance of the antenna.

16. The filter of claim 15, wherein the two or more sub-filters have noncontiguous passbands, and wherein each of the noncontiguous passbands is a passband of only one sub-filter.

17. The filter of claim 15, wherein each of the two or more sub-filters has a non-continuous pass band separated by a stop band, wherein the stop band is present if an input-output transfer function of the matrix filter is less than-20 dB.

18. The filter of claim 15, wherein only one of the two or more sub-filters is selected to be connected between the filter input port and the respective filter output port; and wherein no input-output transfer function of a single sub-filter intersects the input-output transfer function of the other sub-filter at frequencies where the transfer functions of both filters are higher than-20 dB.

19. The filter of claim 15, wherein the sub-filter connections between the filter input and the respective filter output ports are switchable to select one or more non-contiguous passbands.

20. A three-band diversity receiver, comprising:

a matrix triplexer coupled between an antenna and three receivers, the triplexer comprising;

a first sub-filter coupled between a first filter port and a second filter port, wherein the second filter port is coupled to the first receiver;

a second sub-filter coupled between the first filter port and a third filter port, wherein the third filter port is coupled to the second receiver;

a third sub-filter coupled between the first filter port and a fourth filter port, wherein the fourth filter port is coupled to the third receiver;

wherein each sub-filter comprises a ladder circuit having at least three laterally excited thin film bulk acoustic resonator (XBAR) series elements and at least two capacitive parallel elements;

and wherein the impedance of the second, third and fourth filter ports is matched to the input impedance of the respective low noise amplifiers, an

The impedance at the first filter port matches the impedance of the antenna.

21. The filter of claim 20, wherein each of the 3 sub-filters has a non-continuous pass band separated from the pass bands of all other 3 sub-filters, wherein the separation is accomplished by a stop band that exists at less than-20 dB at the input-output transfer function of the matrix filter.

22. The filter of claim 20,

each of the XBAR series elements is connected in series between the first sub-filter port and the second sub-filter port; and

each of the parallel capacitors is connected between ground and a node between a respective pair of XBAR series elements.