CN113556095B - Cross-coupled acoustic filter - Google Patents
Cross-coupled acoustic filter Download PDFInfo
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- CN113556095B CN113556095B CN202110835188.1A CN202110835188A CN113556095B CN 113556095 B CN113556095 B CN 113556095B CN 202110835188 A CN202110835188 A CN 202110835188A CN 113556095 B CN113556095 B CN 113556095B
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- 230000008878 coupling Effects 0.000 claims abstract description 46
- 238000010168 coupling process Methods 0.000 claims abstract description 46
- 238000005859 coupling reaction Methods 0.000 claims abstract description 46
- 239000003990 capacitor Substances 0.000 claims description 7
- 238000003780 insertion Methods 0.000 abstract description 12
- 230000037431 insertion Effects 0.000 abstract description 12
- 230000001965 increasing effect Effects 0.000 abstract description 8
- 230000001629 suppression Effects 0.000 abstract description 7
- 230000005540 biological transmission Effects 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000006880 cross-coupling reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000005764 inhibitory process Effects 0.000 description 3
- 238000010295 mobile communication Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000010897 surface acoustic wave method Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02062—Details relating to the vibration mode
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
- H03H9/56—Monolithic crystal filters
- H03H9/564—Monolithic crystal filters implemented with thin-film techniques
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
- H03H9/58—Multiple crystal filters
- H03H9/582—Multiple crystal filters implemented with thin-film techniques
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
- H03H9/703—Networks using bulk acoustic wave devices
- H03H9/706—Duplexers
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
A capacitive cross-coupled acoustic filter comprising: a series main circuit formed by connecting m first acoustic resonators in series between an input terminal and an output terminal; n parallel branches, one end of each parallel branch is connected to m-1 nodes between adjacent first acoustic resonators and/or the head end and the tail end of a serial main loop, and the other end of each parallel branch is grounded; the n parallel branches are numbered in sequence, and each parallel branch comprises at least one second acoustic resonator; at least 2 coupling branches connected to one ends of the n parallel branches, wherein the difference between the serial number of the parallel branch connected to the first end and the serial number of the parallel branch connected to the second end is greater than or equal to 2; the first end of at least one coupling leg is connected between the first end and the second end of the other coupling leg, and the second end is connected outside the first end and the second end of the other coupling leg. In accordance with the acoustic filter of the present invention, additional transmission zeroes are added, suppression on both sides of the passband is increased and in-band insertion loss is optimized.
Description
Technical Field
The present invention relates to a cross-coupled acoustic filter, and in particular to a capacitive cross-coupled acoustic filter.
Background
In recent years, with the progress of mobile communication systems, portable information terminals and the like have rapidly spread. Related efforts have been made to develop the terminal to reduce the size and improve the performance thereof. Both analog and digital are used in mobile telephone systems. Piezoelectric surface acoustic wave filters or film bulk acoustic wave (SAW or FBAR) resonator filters have been proposed for use in devices of mobile communication systems.
Fig. 1A to 1C are circuit diagrams showing an acoustic filter using an FBAR according to the related art, respectively. In the prior art shown in fig. 1A, an electromagnetic LC filter circuit 00 and a ladder-type FBAR network cascade formed by FBAR resonators 131-133 are used, and the left/right roll-off and near stop band suppression of the filter are modified by connecting two parallel branches FBARs with an inductor/capacitor 20. However, the adopted mode can only independently trim the roll-off and the inhibition of one side, and the inhibition of two sides cannot be controlled simultaneously.
In the prior art shown in fig. 1B, the tuning of the resonant frequency of the FBARs 101, 102 in parallel with the additional capacitances 103, 104 is used to optimize the roll-off coefficient and in-band matching of the entire filter/duplexer, but this approach belongs to the self-tuning of the FBARs themselves, belongs to the intrinsic tuning, and cannot generate additional transmission zeros and transmission poles.
In the prior art shown in fig. 1C, the effect of enhancing the sideband roll-off in the traditional duplexer is achieved by adopting a mode that the electromagnetic LC network 11 is connected with the FBAR 12 in series, and the mode belongs to simple performance superposition, increases the matching difficulty of the antenna end while increasing the insertion loss, and is not beneficial to practical application.
Disclosure of Invention
It is therefore an object of the present invention to provide an FBAR filter that overcomes the above technical hurdles.
The invention provides a cross-coupled acoustic filter comprising:
a series main circuit formed by connecting m first acoustic resonators in series between an input terminal and an output terminal, wherein m is an integer of 3 or more;
One end of each of the n parallel branches is connected to m-1 nodes between adjacent first acoustic resonators and/or the head end and the tail end of the serial main loop respectively, and the other ends of the n parallel branches are grounded; and n parallel branches are numbered in sequence, each parallel branch comprises at least one second acoustic resonator, wherein n is an integer greater than or equal to 4;
At least 2 coupling branches connected to one ends of the n parallel branches, wherein the difference between the serial number of the parallel branch connected to the first end of each coupling branch and the serial number of the parallel branch connected to the second end of the coupling branch is greater than or equal to 2;
the first end of at least one coupling leg is connected between the first end and the second end of the other coupling leg, and the second end of the at least one coupling leg is connected outside the first end and the second end of the other coupling leg.
Wherein a matching circuit is further included between the input terminal and/or the output terminal and the series main loop. Wherein the matching circuit comprises a capacitance and/or an inductance in series and/or parallel.
Wherein each parallel branch further comprises a series inductance between the second FBAR resonator and ground potential.
Wherein all or a portion of the coupling branch comprises a series capacitor or a series inductor.
The invention also provides a diplexer comprising a cross-coupled acoustic filter according to any preceding claim.
According to the acoustic filter of the present invention, a plurality of cross-coupling structures of different polarities are introduced on the FBAR ladder network, additional transmission zeroes are added, suppression on both sides of the passband is increased and in-band insertion loss is optimized.
The stated objects of the application, as well as other objects not listed herein, are met within the scope of the independent claims of the present application. Embodiments of the application are defined in the independent claims and specific features are defined in the dependent claims thereof.
Drawings
The technical solution of the present invention is described in detail below with reference to the attached drawings, wherein:
FIGS. 1A-1C show circuit diagrams of prior art FBAR filters, respectively;
fig. 2 shows a circuit diagram of a cross-coupled acoustic filter according to the present invention;
FIG. 3A shows a circuit diagram of a cross-coupled acoustic filter according to an embodiment of the present invention;
FIG. 3B shows the insertion loss of the cross-coupled acoustic filter of FIG. 3A;
FIG. 4A shows a circuit diagram of a cross-coupled acoustic filter according to another embodiment of the present invention;
Fig. 4B shows the insertion loss of the cross-coupled acoustic filter of fig. 4A.
Detailed Description
The features of the technical solution of the present application and its technical effects are described in detail below with reference to the accompanying drawings in combination with exemplary embodiments, and a cross-coupled acoustic filter is disclosed. It should be noted that like reference numerals refer to like structures and that the terms "first," "second," "upper," "lower," and the like as used herein may be used to modify various device structures. These modifications, unless specifically stated, do not imply a spatial, sequential, or hierarchical relationship to the modified device structures.
As shown in fig. 2, A cross-coupled acoustic filter according to the principles of the present invention includes A series-parallel network of A plurality of first acoustic resonators (fbars) and A plurality of inductors between A first (input) terminal A and A second (output) terminal B, wherein m (m is an integer equal to or greater than 3) first FBAR resonators S1, S2 … Sm are sequentially connected in series to form A series main loop, N (where N is an integer equal to or greater than 4) parallel branches are connected at one end to m-1 nodes N1, N2 … Nm "1 between adjacent first FBAR resonators and/or at the first end of the series main loop, the other end is grounded, N parallel branches are sequentially numbered, each parallel branch includes at least one second acoustic resonator, that is, each parallel branch includes A second FBAR resonator P1, P2 … Pm 1 connected in series to ground, preferably, the respective parallel branches may have additional zero-level coupling effected beyond Pm 1, pm 2L …, and no additional zero level coupling is effected thereto. At least 2 capacitive coupling structures C1, C2 … Cm-3 are coupled between m-1 nodes and preferably the difference in the number of the node coupled at the first end (e.g., N1, N2) and the number of the node coupled at the second end (e.g., N3, N4) of each coupling structure is greater than or equal to 2 such that the node coupled at the first end of the latter coupling structure is between the two coupling nodes of the former coupling structure. The first end of at least one coupling leg is connected between the first end and the second end of the other coupling leg, and the second end of the at least one coupling leg is connected outside the first end and the second end of the other coupling leg. Preferably, a matching circuit is further included between the input terminal a and the series main circuit, and in the embodiment of fig. 2, the matching circuit includes a capacitor C0 (only shown in series, actually may be parallel, or a plurality of LCs connected in series and parallel in the figure), and in the embodiment of fig. 2, the matching circuit further includes a matching circuit between the output terminal B and the series main circuit, and in the embodiment of fig. 2, the matching circuit includes an inductance L0 (only shown in parallel, actually may be connected in series, or a plurality of LCs connected in series and parallel in the figure) connected in parallel or in series in parallel in the figure, so as to adjust the loading phase of the filter to meet the basic chebyshev filtering function. Preferably, the coupling structures are all capacitive, and the capacitive negative coupling structure brings about a function of suppression increase on both sides of the passband and in-band interpolation loss optimization. It is further preferred that at least one of the coupling structures is an inductance and the remaining part is a capacitance (i.e. the coupling structure is partly a capacitance), the addition of coupling structures of different polarity also producing a similar effect as capacitive coupling.
Fig. 3A shows an N79 full band filter made up of cross-coupled acoustic filters with a frequency band of 4.4-5GHZ according to a preferred embodiment of the present invention. Where m is selected to be 5, both coupling structures are capacitors C1, C2, and the four inductances attached to the parallel branches are l1= 1.07911pH, l2= 1.54999pH, l3= 3.19846pH, and l4= 1.10204pH, respectively, for ports C0, e.g., 0-50pf, L0, e.g., 0-50nH, L1-L4, 0-10nH. Wherein L2 and L3 are important parts for expanding the bandwidth of the whole filter, the action mechanism is that the series resonance frequency of P2 and P3 is reduced, and the equivalent electromechanical coupling coefficient (kteff) which is the difference value representing the resonant frequency of the FBAR is increased, so that the bandwidth is expanded. The two coupling capacitors are loaded between P1 and P3 and between P2 and P4, increasing near-stop band rejection and roll-off on both sides of the filter. As described with reference to fig. 2, the matching circuits, i.e., the matching devices C0 and L0, on both sides adjust the respective phases.
Fig. 3B shows the insertion loss of the cross-coupled acoustic filter of fig. 3A, where the horizontal axis is frequency GHz and the vertical axis is insertion loss dB. The curve marked by the broken line in the figure is the circuit simulation result before the cross coupling is not added, and the solid line is the insertion loss of the new scheme. It can be obviously seen that after the coupling capacitor is added, zero is added to the right side of the near-stop band, the near-stop band inhibition on the two sides is enhanced by 5-10dB, and collapse occurs to a certain extent on the right side of the pass band.
Fig. 4A shows an N79 full band filter made up of cross-coupled acoustic filters with a frequency band of 4.4-5GHZ according to another preferred embodiment of the present invention. Where m is chosen to be 5, two coupling structures are Lc and Cc, four inductors attached to the parallel branches are l1= 0.992685pH, l2= 1.99773pH, l3= 4.09519pH and l4= 1.19841pH, respectively, C0, e.g. 0-50pf, L0, e.g. 0-50nH, alternatively L1-L4 are chosen to be 0-10nH at the ports. Wherein L2 and L3 are important parts for expanding the bandwidth of the whole filter, the action mechanism is that the series resonance frequency of P2 and P3 is reduced, and the equivalent electromechanical coupling coefficient (kteff) which is the difference value representing the resonant frequency of the FBAR is increased, so that the bandwidth is expanded. The coupling inductance Lc and the coupling capacitance Cc are respectively loaded between P1 and P3 and between P2 and P4, so that near-stop band suppression and roll-off on both sides of the filter are increased. The matching devices C0 and L0 on both sides adjust the respective phases.
Fig. 4B shows the insertion loss of the cross-coupled acoustic filter of fig. 4A, where the horizontal axis is frequency GHz and the vertical axis is insertion loss dB. The curve marked by the broken line in the figure is the circuit simulation result before the cross coupling is not added, and the solid line is the insertion loss of the new scheme. Compared to pure capacitive coupling, it can be seen that the lower sideband (the frequency band below the lower edge of the passband) has a significant enhancement in suppression level and an additional transmission zero is added. At the same time, the upper sideband (the frequency band above the upper edge of the passband) rejection also remains at a level of 30 dB.
According to the acoustic filter of the present invention, a plurality of cross-coupling structures of different polarities are introduced on the FBAR ladder network, additional transmission zeroes are added, suppression on both sides of the passband is increased and in-band insertion loss is optimized.
While the invention has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various suitable changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings disclosed without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the device structure and method of making the same will include all embodiments falling within the scope of the present invention.
Claims (6)
1. A cross-coupled acoustic filter comprising:
a series main circuit formed by connecting m first acoustic resonators in series between an input terminal and an output terminal, wherein m is an integer of 3 or more;
One end of each of the n parallel branches is connected to m-1 nodes between adjacent first acoustic resonators and/or the head end and the tail end of the serial main loop respectively, and the other ends of the n parallel branches are grounded; and n parallel branches are numbered in sequence, each parallel branch comprises at least one second acoustic resonator, wherein n is an integer greater than or equal to 4;
At least 2 coupling branches connected to one ends of the n parallel branches, wherein the difference between the serial number of the parallel branch connected to the first end of each coupling branch and the serial number of the parallel branch connected to the second end of the coupling branch is greater than or equal to 2;
the first end of at least one coupling leg is connected between the first end and the second end of the other coupling leg, and the second end of the at least one coupling leg is connected outside the first end and the second end of the other coupling leg.
2. The cross-coupled acoustic filter of claim 1, wherein the input terminal and/or the output terminal further comprises a matching circuit between the input terminal and the series main loop.
3. The cross-coupled acoustic filter of claim 2, wherein the matching circuit comprises a capacitance and/or inductance in series and/or parallel.
4. The cross-coupled acoustic filter of claim 1 wherein each parallel branch further comprises a series inductance between the second FBAR resonator and ground potential.
5. The cross-coupled acoustic filter of claim 1, wherein all or a portion of the coupling branches comprise a series capacitor or a series inductor.
6. A diplexer comprising a cross-coupled acoustic filter according to any one of claims 1-5.
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| CN202110835188.1A CN113556095B (en) | 2021-07-23 | 2021-07-23 | Cross-coupled acoustic filter |
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| CN202110835188.1A CN113556095B (en) | 2021-07-23 | 2021-07-23 | Cross-coupled acoustic filter |
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| CN113556095B true CN113556095B (en) | 2024-04-19 |
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| CN116865714B (en) * | 2023-09-05 | 2023-12-19 | 深圳新声半导体有限公司 | Filter for N79 frequency band |
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