CN116781035A - Filter, multiplexer and RF front-end module - Google Patents
Filter, multiplexer and RF front-end module Download PDFInfo
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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
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
- H03H9/6483—Ladder SAW filters
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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
- H03H9/02086—Means for compensation or elimination of undesirable effects
- H03H9/02102—Means for compensation or elimination of undesirable effects of temperature influence
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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
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02834—Means for compensation or elimination of undesirable effects of temperature influence
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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
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
- H03H9/56—Monolithic crystal filters
- H03H9/566—Electric coupling means therefor
- H03H9/568—Electric coupling means therefor consisting of a ladder configuration
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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
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
- H03H9/58—Multiple crystal filters
- H03H9/60—Electric coupling means therefor
- H03H9/605—Electric coupling means therefor consisting of a ladder configuration
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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
- H03H9/70—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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- 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
- H03H9/72—Networks using surface acoustic waves
- H03H9/725—Duplexers
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Abstract
The application relates to a filter, a multiplexer and a radio frequency front end module, comprising: a series arm resonator connected between the input terminal and the output terminal; a parallel arm resonator having one end connected to the series arm resonator and the other end connected to a ground terminal; a first resonator; the series arm resonator includes a second resonator, the first resonator being connected in parallel with the second resonator; the anti-resonance frequency of the first resonator is smaller than the resonance frequency of the parallel arm resonator, so that a transmission zero point is generated on a low-frequency stop band outside the pass band of the filter, and the out-of-band rejection level of the filter on the low-frequency side is improved. The application can improve the out-of-band rejection level of the filter to the specific frequency band without adopting a mode of improving the order of the filter or improving the capacitance ratio of the parallel arm resonator to the series arm resonator, thereby improving the out-of-band rejection level to the specific frequency band on the basis of not influencing the insertion loss and increasing the volume of the filter.
Description
Technical Field
The application belongs to the technical field of radio frequency filtering, and particularly relates to a filter, a multiplexer and a radio frequency front-end module.
Background
The ladder filter is composed of a plurality of series-arm resonators and a plurality of parallel-arm resonators, and in the existing wireless communication system, the filter is required to suppress signals in a specific frequency band. For a ladder filter, it is generally used to increase the order of the filter or the capacitance ratio of the parallel arm resonator to the series arm resonator in order to increase the out-of-band rejection level of the filter for a specific frequency band, but this leads to an increase in the size of the filter or an increase in the passband insertion loss, which affects the transmission quality of the wireless communication system.
In addition, when the duplexer composed of the filters is operated, the transmitting-side filter and the receiving-side filter need to have a high level of isolation, otherwise, signal leakage can occur, and the wireless communication system is affected. One way to increase the isolation of the transmit and receive filters is to increase the level of out-of-band rejection in the transmit or receive frequency bands.
It is therefore particularly important how to increase the out-of-band rejection level for a particular frequency band without affecting the insertion loss and increasing the filter size.
Disclosure of Invention
The application provides a filter, a multiplexer and a radio frequency front end module, which aim to improve the out-of-band suppression level of a specific frequency band on the basis of not influencing the insertion loss and increasing the volume of the filter.
In order to solve the above-mentioned problems, an embodiment of the present application provides a filter including: a series arm resonator connected between the input terminal and the output terminal; a parallel arm resonator having one end connected to the series arm resonator and the other end connected to a ground terminal; a first resonator; the series arm resonator includes a second resonator, the first resonator being connected in parallel with the second resonator; the anti-resonant frequency of the first resonator is less than the resonant frequency of the parallel arm resonator to produce a transmission zero at the low frequency stop band outside the filter passband.
Optionally, a first target frequency point f on a low-frequency band outside the filter passband 1 Said secondStatic capacitance C of resonator 01 Static capacitance C of the first resonator 0x Dynamic capacitance C of the first resonator mx And a resonant frequency f of the first resonator xr The following relationship is satisfied:
optionally, the first resonator includes at least two subresonators connected in parallel with each other.
Optionally, the structural parameters of each sub-resonator are the same, and the first target frequency point f on the low-frequency band outside the filter passband 1 Static capacitance C of the second resonator 01 The number n of the subresonators, the static capacitance C of the subresonators 1 Equivalent dynamic capacitance C of n said subresonators 2 Resonant frequency f of the sub-resonator 2 The following relationship is satisfied:
optionally, the antiresonance frequency of the first resonator is smaller than the resonant frequency of any one of the parallel arm resonators.
Optionally, the number of the first resonators is N, the number of the second resonators is M, N is less than or equal to M, and N is an integer greater than 1; each of the first resonators is connected in parallel with at least one of the second resonators.
Optionally, a second target frequency point f on the high frequency side outside the filter passband 3 Static capacitance C of the second resonator 01 Dynamic capacitance C of the second resonator m1 Static capacitance C of the first resonator 0x Anti-resonant frequency f of the second resonator 4 The following relationship is satisfied:
optionally, the static capacitance of the first resonator is smaller than the static capacitance of the second resonator.
Optionally, the first resonator and the second resonator are bulk acoustic wave resonators, and an effective area of the first resonator is smaller than an effective area of the second resonator.
Optionally, the static capacitance of the first resonator is greater than or equal to the static capacitance of the parallel arm resonator.
Optionally, the series arm resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator; the parallel arm resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator; the first resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator.
In order to solve the above problems, an embodiment of the present application further provides a multiplexer, including the filter described in any one of the above.
In order to solve the above problems, an embodiment of the present application provides a radio frequency front end module, including the filter described in any one of the above.
In the filter, the multiplexer and the radio frequency front end module provided by the embodiment of the application, the anti-resonant frequency of the first resonator connected in parallel with the series arm resonator (namely the second resonator) is set smaller than the resonant frequency of the parallel arm resonator so as to generate a transmission zero point on the low-frequency stop band outside the pass band of the filter, thereby improving the out-of-band rejection level of the filter on the low-frequency side. The application can improve the out-of-band rejection level of the filter to the specific frequency band without adopting a mode of improving the order of the filter or improving the capacitance ratio of the parallel arm resonator to the series arm resonator, thereby improving the out-of-band rejection level to the specific frequency band on the basis of not influencing the insertion loss and increasing the volume of the filter.
Drawings
Fig. 1 is a schematic structural diagram of a filter according to an embodiment of the present application;
FIG. 2 is a diagram showing a transmission characteristic of a filter according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 4 is a schematic diagram of a second filter according to another embodiment of the present application;
fig. 5 is a schematic diagram of an equivalent circuit of a resonator of the filter according to the present application;
fig. 6 is a schematic diagram III of a filter according to another embodiment of the present application;
fig. 7 is a transmission characteristic diagram of a filter according to another embodiment of the present application;
fig. 8 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 9 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 10 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 11 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 12 is a schematic structural diagram of a filter according to another embodiment of the present application;
fig. 13 is a schematic diagram of a filter according to another embodiment of the present application;
fig. 14 is a schematic view showing a structure of a filter according to another embodiment of the present application.
Reference numerals in the specification are as follows:
10. a filter;
1. a series arm resonator; 1a, a second resonator;
2. a parallel arm resonator;
3. a first resonator; 3a, a sub-resonator;
4. an input end;
5. an output end;
6. and a grounding end.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the application more clear, the application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
As shown in fig. 1, in an embodiment, the filter 10 includes a series-arm resonator 1, a parallel-arm resonator 2, and a first resonator 3. The series-arm resonator 1 is connected between an input terminal 4 and an output terminal 5; one end of the parallel arm resonator 2 is connected to the series arm resonator 1, and the other end of the parallel arm resonator 2 is connected to the ground terminal 6; the series-arm resonator 1 includes a second resonator 1a, and the first resonator 3 is connected in parallel with the second resonator 1 a. The input terminal 4 is an input terminal of the filter 10, the output terminal 5 is an output terminal of the filter 10, and the ground terminal 6 is a ground terminal of the filter 10. In addition, the connection between the series arm resonator 1 and the input terminal 4 means that they are electrically connected, the connection between the series arm resonator 1 and the output terminal 5 means that they are electrically connected, the connection between the parallel arm resonator 2 and the series arm resonator 1 means that they are electrically connected, and the connection between the parallel arm resonator 2 and the ground terminal 6 means that they are electrically connected; the connection between the first resonator 3 and the second resonator 1a means that both are electrically connected.
In the embodiment shown in fig. 1, the number of the series-arm resonators 1 and the number of the parallel-arm resonators 2 are plural, each parallel-arm resonator 2 is connected between two series-arm resonators 1, the other end of each parallel-arm resonator 2 is connected to the ground, and one parallel-arm resonator 2 is usually connected between two adjacent series-arm resonators 1. Wherein "a plurality of" means greater than or equal to two.
Note that fig. 1 shows only one configuration of the filter 10 according to the present embodiment, and the filter 10 according to the present embodiment is not limited to the number and connection of the series-arm resonators 1 and the parallel-arm resonators 2, nor to the configuration shown in fig. 1. For example, in other embodiments, the number of parallel arm resonators 2 may be only one. In other embodiments, the parallel-arm resonator 2 may be connected between the input terminal 4 and the series-arm resonator 1 adjacent to the input terminal 4, and the parallel-arm resonator 2 may be connected between the output terminal 5 and the series-arm resonator 1 adjacent to the output terminal 5.
Specifically, referring to fig. 12, when the number of parallel-arm resonators 2 is plural, some parallel-arm resonators 2 may be connected between adjacent two series-arm resonators 1, some parallel-arm resonators 2 may be connected between the series-arm resonators 1 closest to the input terminal 4 and the adjacent input terminal 4, and some parallel-arm resonators 2 may be connected between the output terminal 5 and the series-arm resonators 1 adjacent to the output terminal 5. Alternatively, referring to fig. 13, when the number of parallel-arm resonators 2 is plural, some parallel-arm resonators 2 may be connected between adjacent two series-arm resonators 1, and other parallel-arm resonators 2 may be connected between the input terminal 4 and the series-arm resonator 1 adjacent to the input terminal 4. Alternatively, referring to fig. 14, when the number of parallel-arm resonators 2 is plural, some parallel-arm resonators 2 may be connected between adjacent two series-arm resonators 1, and other parallel-arm resonators may be connected between the output terminal 5 and the series-arm resonator 1 adjacent to the output terminal 5.
In addition, in the present embodiment, the antiresonant frequency of the first resonator 3 is smaller than the resonant frequency of the parallel arm resonator 2 to generate a transmission zero on the low-frequency stop band outside the pass band of the filter 10, thereby improving the out-band rejection level of the filter 10 on the low-frequency side. The present embodiment can increase the out-of-band rejection level of the filter 10 for a specific frequency band without increasing the order of the filter 10 or the capacitance ratio of the parallel arm resonator 2 to the series arm resonator 1, thereby increasing the out-of-band rejection level for the specific frequency band without affecting the insertion loss and increasing the volume of the filter 10.
As shown in fig. 2, in the figure, the solid line is the signal transmission characteristic curve of the filter 10 of the present embodiment, and the broken line is the signal transmission characteristic curve of the filter of the comparative example, wherein the abscissa in the figure is frequency in HZ, and the ordinate is transmission characteristic in dB. In fig. 2, the range between fa and fb is a pass band, between fa and fc is a low-frequency side transition band, between fb and fd is a high-frequency side transition band, the left side of fc is a low-frequency stop band, and the right side of fd is a high-frequency stop band. In the present embodiment, by setting the antiresonant frequency of the first resonator 3 smaller than the resonant frequency of the parallel arm resonator 2, the transmission zero can be formed on the left side of fc.
In fig. 2, the filter of the comparative example is not provided with the first resonator 3, as compared with the filter 10 of the present embodiment. The present embodiment is equivalent to the filter of this comparative example in that, by connecting the first resonators 3 in parallel to both ends of the corresponding series-arm resonator 1 and setting the antiresonance frequency of the first resonators 3 to be smaller than the resonant frequency of the parallel-arm resonator 2, a transmission zero is formed on the low-frequency stop band outside the passband of the filter, wherein the transmission characteristic at the transmission zero is lowered, so that the out-of-band suppression level can be improved. For example, f in FIG. 2 0 For one transmission zero point shown in the present embodiment, it can be seen from the figure that the arrangement of the present embodiment can reduce f as compared with the comparative example filter 0 Transmission characteristics at that point. It should be understood that f 0 Indicating that a transmission zero is generated at any frequency point on the low-frequency stop band outside the pass band of the filter, the position of the transmission zero is only schematically shown in fig. 2.
Defining the resonant frequency of the series arm resonator 1 as f sr The antiresonant frequency of the series arm resonator 1 is f sa The parallel arm resonator 2 has a resonant frequency f pr The antiresonant frequency of the parallel arm resonator 2 is f pa The first resonator 3 has a resonant frequency f xr The antiresonance frequency of the first resonator 3 is f xa The method comprises the steps of carrying out a first treatment on the surface of the In one possible embodiment, f xr ＜f xa ＜f pr ＜f pa ＜f sr ＜f sa . Of course, in guarantee f xa ＜f pr On the premise of f pr 、f pa 、f sr F sa The size relation may be other settings, and the embodiment is not limited herein.
In an embodiment, when the filter 10 includes a plurality of parallel-arm resonators 2, the antiresonant frequency of the first resonator 3 is smaller than the resonant frequency of any one of the parallel-arm resonators 2. That is, the antiresonant frequency of the first resonator 3 is smaller than the minimum value of the resonant frequency of each parallel-arm resonator 2.
When there are a plurality of first resonators 3, the antiresonant frequency of any one of the first resonators 3 is smaller than the minimum value of the resonant frequency of each of the parallel arm resonators 2.
As shown in fig. 1, in one embodiment, the second resonator 1a is the one adjacent to the input end 4, that is, the second resonator 1a is the one closest to the input end 4 in each series-arm resonator 1. Of course, in other embodiments, the second resonator 1a may also be located at other positions, for example, referring to fig. 3, the second resonator 1a is the resonator adjacent to the output end 5, that is, the second resonator 1a is the resonator closest to the output end 5 in each series-arm resonator 1; alternatively, referring to fig. 4, both ends of the second resonator 1a are provided with respective series-arm resonators 1.
As shown in fig. 5, the mechanical model of a single resonator can be equivalent to a circuit model using MBVD models. Wherein R is s Is the wiring loss (namely the resistance of the wiring) of the resonator, R m Is the dynamic resistance of the resonator, L m Dynamic inductance, C, of resonator m Dynamic capacitance, R, of resonator 0 Is the static resistance of the resonator, C 0 Is the static capacitance of the resonator. When the resonant frequency of the resonator is fixed, the antiresonant frequency of the resonator can be changed by changing the capacitance of the resonator. In the present embodiment, on the basis that the antiresonance frequency of the first resonator 3 is smaller than the resonant frequency of the parallel arm resonator 2, the antiresonance frequency of the first resonator 3 can be adjusted by changing the capacitance of the first resonator 3, so that the position of the transmission zero point generated on the low-frequency stop band outside the passband of the filter 10 can be adjusted to a desired frequency point.
In a possible embodiment, the first target frequency point f is on the low frequency band outside the pass band of the filter 10 1 Static capacitance C of the second resonator 1a 01 Static capacitance C of the first resonator 3 0x Dynamic capacitance C of the first resonator 3 mx Resonant frequency f of the first resonator 3 xr The following relationship is satisfied:
wherein the capacitance parameters of the first resonator 3 include parameters of the static capacitance of the first resonator 3 and parameters of the dynamic capacitance of the first resonator 3. In addition, when the antiresonant frequency of the first resonator 3 is smaller than the resonant frequency of the parallel-arm resonator 2 without changing the existing filter structure, the transmission zero point can be formed at a predetermined frequency point (i.e., a first target frequency point) by adjusting the capacitance parameter of the first resonator 3. That is, on the basis that the antiresonance frequency of the first resonator 3 is smaller than the resonance frequency of the parallel arm resonator, the static capacitance and dynamic capacitance parameters of the first resonator 3 are adjusted so that the above-described relationship is satisfied between the capacitance parameter and resonance frequency of the first resonator 3, the static capacitance of the second resonator 1a, and the frequency point f1 at which the transmission zero point needs to be generated (i.e., the frequency point at which the out-of-band suppression needs to be performed), so that the generation of the transmission zero point at the frequency point can be realized, and the out-of-band suppression level at the frequency point can be improved.
In another possible embodiment, as shown in fig. 6, the first resonator 3 comprises at least two sub-resonators 3a connected in parallel with each other, i.e. the first resonator 3 comprises at least two sub-resonators 3a, and each sub-resonator 3a is connected in parallel to both ends of the second resonator 1 a.
Each of the sub-resonators 3a has a resonant frequency and a resonant frequency, the resonant frequency of one first resonator 3 is the equivalent resonant frequency of each sub-resonant frequency 3a included in the first resonator 3, and the anti-resonant frequency of one first resonator 3 is the equivalent anti-resonant frequency of each sub-resonant frequency 3a included in the first resonator 3. The static capacitance of one first resonator 3 is the equivalent static capacitance of each sub-resonator 3a included in the first resonator 3, and the dynamic capacitance of one first resonator 3 is the equivalent dynamic capacitance of each sub-resonator 3a included in the first resonator 3.
In addition, the structural parameters of the sub-resonators 3a included in one first resonator 3 may be the same, or the structural parameters of two sub-resonators 3a in each sub-resonator 3a included in one first resonator 3 may be different. The structural parameters of the two subresonators 3a are different, which means that at least one of the parameters of the resonant frequency, antiresonant frequency, dynamic capacitance, static capacitance, and the like of the two subresonants 3a is different. The same structural parameters of the two subresonators 3a mean that the parameters of the resonant frequency, antiresonant frequency, dynamic capacitance, static capacitance, and the like of the two subresonants 3a are the same.
The sub-resonator 3a may be composed of a plurality of cascaded resonators, for example, the sub-resonator 3a is composed of a plurality of resonators (the resonator is defined as a third resonator) connected in series, or the sub-resonator 3a includes a fourth resonator in addition to the plurality of third resonators connected in series, and the fourth resonator is connected in parallel with at least one third resonator. In this embodiment, the resonance frequency of one sub-resonator 3a is the equivalent resonance frequency of each level resonator included in the sub-resonator 3a, the antiresonance frequency of one sub-resonator 3a is the equivalent antiresonance frequency of each level resonator included in the sub-resonator 3a, the static capacitance of one sub-resonator 3a is the equivalent static capacitance of each level resonator included in the sub-resonator 3a, and the dynamic capacitance of one sub-resonator 3a is the equivalent dynamic capacitance of each level resonator included in the sub-resonator 3 a.
In addition, when the number of the sub-resonators 3a is plural, each of the sub-resonators 3a may be composed of plural cascaded resonators; alternatively, when there are a plurality of sub-resonators 3a, each sub-resonator 3a is not composed of a plurality of cascaded resonators, i.e., each sub-resonator 3a is only an independent resonator; alternatively, when the number of the sub-resonators 3a is plural, a part of each sub-resonator 3a is composed of plural resonators in cascade, and the other part is only one independent resonator.
In a further possible embodiment, the structural parameters of the sub-resonators 3a are identical, a first target frequency point f on the low-frequency band outside the pass band of the filter 10 1 Static capacitance C of the second resonator 1a 01 The number n of the subresonators 3a, n.gtoreq.2, the static capacitance C of the subresonators 3a 1 Equivalent dynamic capacitance C of n subresonators 3a 2 Resonant frequency f of sub-resonator 3a 2 Satisfy therebetween toThe following relationship:
the capacitance parameters of the subresonator 3a include parameters of the static capacitance of the subresonator 3a and parameters of the dynamic capacitance of the subresonator 3 a. Equivalent dynamic capacitance C of n subresonators 3a 2 It is understood that the n sub-resonators 3a are equivalent in parallel to one resonator, which equivalent is the dynamic capacitance of the resonator.
In an embodiment, the number of the first resonators 3 is N, the number of the second resonators 1a is M, and N is less than or equal to M; each first resonator 3 is connected in parallel with at least one second resonator 1 a. This may create N transmission zeroes at the low frequency stop band outside the pass band of the filter 10. Wherein N and M are integers greater than 1. When N is greater than 1, if the structural parameters of the two first resonators 3 are the same, the transmission zeros generated by the two first resonators 3 are coincident; when N is greater than 1, if the structural parameters of the two first resonators 3 are different, the transmission zeros generated by the two first resonators 3 do not coincide (refer to fig. 7, where the abscissa and ordinate parameters in fig. 7 are the same as those in fig. 2). When the structural parameters of the first resonators 3 are identical, the transmission zeros formed by the first resonators 3 are all coincident.
The structural parameters of the two first resonators 3 are the same, which means that the resonant frequency, anti-resonant frequency, dynamic capacitance, static capacitance, and the number of the sub-resonators 3a of the two first resonators 3 are the same. The structural parameters of the two first resonators 3 are different, which means that at least one parameter of the resonant frequency, antiresonance frequency, dynamic capacitance, static capacitance, and the number of the sub-resonators 3a of the two first resonators 3 is different.
For example, in the embodiment shown in fig. 2, the number of first resonators 3 is 1, and in this embodiment, 1 transmission zero may be generated on the low-frequency stop band outside the pass band of the filter 10; in the embodiment shown in fig. 7, the number of first resonators 3 is 2, and the structural parameters of the two first resonators 3 are different, in this embodiment, 2 transmission zeros may be generated on the low-frequency stop band outside the pass band of the filter 10, and the two transmission zeros do not coincide.
In addition, when N is greater than 1, each first resonator 3 may have only one sub-resonator 3a (refer to fig. 8); alternatively, when N is greater than 1, each of the first resonators 3 may be a resonator having at least two subresonators 3a (refer to fig. 9); alternatively, when N is greater than 1, a part of the first resonators 3 has only one sub-resonator 3a, and another part of the first resonators 3 has at least two sub-resonators 3a (refer to fig. 10).
Further, when N is greater than 1, the relationship between the resonance frequency of each first resonator 3 and the capacitance parameter of the first resonator 3, the capacitance parameter of the second resonator 1a connected in parallel with the first resonator 3, and the transmission zero point generated by the first resonator 3 satisfies the formula of the above embodiment.
A first resonator 3 is connected in parallel with at least two second resonators 1a, meaning that the second resonators 1a are connected in series and then connected in parallel with the first resonator 3 as a whole. For example, in the embodiment shown in fig. 11, the first resonator 3 is connected in parallel with two second resonances. When one first resonator 3 is connected in parallel with a plurality of second resonators 1a, the above-mentioned sum f 1 C in the related formula 01 Is the equivalent static capacitance of each second resonator 1a connected in parallel with the first resonator 3. For example, the first resonator 3 is connected in parallel with two second resonators 1a, and the static capacitances of the two second resonators 1a are respectively C 02 And C 03 The equivalent static capacitance of the two second resonators 1a is 1/C 01 ＝1/C 02 +1/C 03 。
In addition, when N is greater than 1, each first resonator 3 is connected in parallel with one second resonance; alternatively, when N is greater than 1, each first resonator 3 is connected in parallel with at least two second resonances; alternatively, when N is greater than 1, some of the first resonators 3 are connected in parallel with one second resonance, and other of the first resonators 3 are connected in parallel with at least two second resonances.
In yet another possible embodiment, the second target is the high frequency side outside the pass band of the filter 10Frequency point f 3 Static capacitance C of the second resonator 1a 01 Dynamic capacitance C of the second resonator 1a m1 Static capacitance C of the first resonator 3 0x And an antiresonance frequency f of the second resonator 1a 4 The following relationship is satisfied:
in this embodiment, the high-frequency side outside the pass band of the filter 10 is actually a transition band on the high-frequency side.
On the basis that the anti-resonance frequency of the first resonator 3 is smaller than the resonance frequency of the parallel arm resonator 2, a transmission zero point can be generated at a first target frequency point on a low-frequency resistance band on the left side of a pass band by adjusting the capacitance parameter of the first resonator 3, and the capacitance parameter of the first resonator 3 also affects the anti-resonance frequency of the second resonator 1a, so that the transmission zero point can be generated on a high-frequency transition band on the right side of the pass band, the steepness of the right side of the pass band is improved, and the communication performance is improved. Referring to fig. 2, the high-frequency transition band on the right side of the pass band can be made steeper with the arrangement of the present embodiment as compared with the comparative example filter. In fig. 2, only the position of one second target frequency point is shown in this embodiment, and in different embodiments, the position of the second target frequency point may be different.
When the number of the first resonators 3 is plural, plural transmission zeroes may be formed on the high-frequency transition band outside the passband. When there are a plurality of second resonators 1a connected in parallel with one first resonator 3, that is, when a plurality of second resonators 1a are connected in series and then connected in parallel with one first resonator 3, the above-mentioned sum f 3 In the related formula, C 01 C is the equivalent static capacitance of each second resonator 1a connected in parallel with the first resonator 3 m1 Is the equivalent dynamic capacitance of each second resonator 1a connected in parallel with the first resonator 3.
In an embodiment, the series arm resonator 1 is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator; the parallel arm resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator; the first resonator 3 is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator.
Wherein, when the series-arm resonators 1 have a plurality, each series-arm resonator 1 may be a bulk acoustic wave resonator; alternatively, when the series-arm resonators 1 have a plurality, each series-arm resonator 1 may be a surface acoustic wave resonator; alternatively, when the series-arm resonators 1 have a plurality, some of the series-arm resonators 1 are bulk acoustic wave resonators and some of the series-arm resonators 1 are surface acoustic wave resonators.
Also, when there are a plurality of parallel arm resonators 2, each parallel arm resonator 2 may be a bulk acoustic wave resonator; alternatively, when the parallel arm resonators 2 have a plurality, each of the parallel arm resonators 2 may be a surface acoustic wave resonator; alternatively, when the parallel arm resonators 2 have a plurality, some of the parallel arm resonators 2 are bulk acoustic wave resonators and some of the parallel arm resonators 2 are surface acoustic wave resonators.
Also, when the first resonators 3 have a plurality, each of the first resonators 3 may be a bulk acoustic wave resonator; alternatively, when the first resonators 3 have a plurality, each of the first resonators 3 may be a surface acoustic wave resonator; alternatively, when the first resonator 3 has a plurality of resonators, a part of the first resonator 3 is a bulk acoustic wave resonator and a part of the first resonator 3 is a surface acoustic wave resonator.
In addition, when the first resonator 3 includes at least two sub-resonators 3a, each of the sub-resonators 3a may be a bulk acoustic wave resonator, or each of the sub-resonators 3a may be a surface acoustic wave resonator, or a part of the sub-resonators 3a may be a bulk acoustic wave resonator, and a part of the sub-resonators 3a may be a surface acoustic wave resonator.
When the first resonator 3 is a bulk acoustic wave resonator and the first resonator 3 comprises at least two sub-resonators, each sub-resonator is a bulk acoustic wave resonator. When the first resonator 3 is a surface acoustic wave resonator and the first resonator 3 includes at least two sub-resonators, each sub-resonator is a surface acoustic wave resonator.
In an embodiment, the static capacitance of the first resonator 3 is smaller than the static capacitance of the second resonator 1 a. If the static capacitance of the first resonator 3 is greater than or equal to the static capacitance of the second resonator 1a, it may have a detrimental effect on the right side of the passband and reduce the overall out-of-band rejection level of the filter 10. Therefore, in the present embodiment, the static capacitance of the first resonator 3 is smaller than the static capacitance of the second resonator 1a, so that the overall out-of-band rejection level of the filter 10 can be improved, and adverse effects on the right side of the passband can be avoided.
When the first resonator 3 and the second resonator 1a are plural, the "the static capacitance of the first resonator 3 is smaller than the static capacitance of the second resonator 1 a" means that the static capacitance of the first resonator 3 is smaller than the static capacitance of the second resonator 1a connected in parallel thereto. In addition, when one first resonator 3 is connected in parallel with the plurality of second resonators 1a, the "the static capacitance of the first resonator 3 is smaller than the static capacitance of the second resonators 1 a" means that the static capacitance of the first resonator 3 is smaller than the equivalent static capacitance of each of the second resonators 1a connected in parallel therewith.
In an embodiment, when the first resonator 3 and the second resonator 1a are both bulk acoustic wave resonators, the effective area of the first resonator 3 is smaller than the effective area of the second resonator 1 a. The bulk acoustic wave resonator comprises an upper electrode, a piezoelectric film, a lower electrode, an acoustic mirror and a substrate which are sequentially overlapped, wherein the orthographic projection area of the overlapped part of the upper electrode, the piezoelectric film, the lower electrode and the acoustic mirror on the substrate is the effective area of the bulk acoustic wave resonator.
In the embodiment of the present application, the static capacitance of the first resonator 3 may be greater than, less than or equal to the static capacitance of the parallel arm resonator 2.
In a possible embodiment, the static capacitance of the first resonator 3 is greater than or equal to the static capacitance of the parallel arm resonator 2. Compared with the static capacitance of the first resonator 3 being smaller than the static capacitance of the parallel arm resonator 2, the static capacitance of the first resonator 3 is larger than or equal to the static capacitance of the parallel arm resonator 2, the zero depth of the first target frequency point can be improved, and the out-of-band rejection effect of the filter 10 is further improved.
When the number of the first resonators 1 is one and the number of the parallel-arm resonators 2 is plural, the "the static capacitance of the first resonator 3 is greater than or equal to the static capacitance of the parallel-arm resonator 2" means that the static capacitance of the first resonator 3 is greater than the static capacitance of any one of the parallel-arm resonators 2. When the number of the first resonators 3 is plural and the number of the parallel-arm resonators 2 is one, the "the static capacitance of the first resonator 3 is greater than or equal to the static capacitance of the parallel-arm resonator 2" means that the static capacitance of any one of the first resonators 3 is greater than the static capacitance of the parallel-arm resonator 2. When the number of the first resonators 3 and the number of the parallel-arm resonators 2 are plural, the "the static capacitance of the first resonator 3 is greater than or equal to the static capacitance of the parallel-arm resonator 2" means that the static capacitance of any one of the first resonators 3 is greater than the static capacitance of any one of the parallel-arm resonators 2.
In addition, when the first resonator 3 is a bulk acoustic wave resonator, the zero point depth of the first target frequency point is also related to the effective area of the bulk acoustic wave resonator, and when the effective area of the first resonator 3 is larger, the deeper the zero point depth, the larger the quality factor Qa of the anti-resonance point of the first resonator 3.
The embodiment of the present application further provides a multiplexer, which includes the filter 10 according to any one of the embodiments, wherein the multiplexer may be a duplexer, a triplexer, or the like. The transmitting end filter of the multiplexer and the receiving end filter of the multiplexer can both adopt the filters described in the above embodiments, so that the transmitting end filter of the multiplexer and the receiving end filter of the multiplexer have higher level isolation, thereby effectively avoiding signal leakage and improving wireless communication quality.
The embodiment of the present application further provides a radio frequency front end module, which includes the filter 10 described in any one of the embodiments.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.
Claims (13)
1. A filter, comprising:
a series arm resonator connected between the input terminal and the output terminal;
a parallel arm resonator having one end connected to the series arm resonator and the other end connected to a ground terminal; the method comprises the steps of,
a first resonator;
the series arm resonator includes a second resonator, the first resonator being connected in parallel with the second resonator; the anti-resonant frequency of the first resonator is less than the resonant frequency of the parallel arm resonator to produce a transmission zero at the low frequency stop band outside the filter passband.
2. The filter of claim 1, wherein the first target frequency point f is on a low frequency band of resistance outside the filter passband 1 Static capacitance C of the second resonator 01 Static capacitance C of the first resonator 0x Dynamic capacitance C of the first resonator mx And a resonant frequency f of the first resonator xr The following relationship is satisfied:
3. the filter of claim 1, wherein the first resonator comprises at least two subresonators connected in parallel with each other.
4. A filter according to claim 3, wherein each of the subresonators has the same structural parameters, the filter passbandA first target frequency point f on the outer low-frequency band 1 Static capacitance C of the second resonator 01 The number n of the subresonators, the static capacitance C of the subresonators 1 Equivalent dynamic capacitance C of n said subresonators 2 Resonant frequency f of the sub-resonator 2 The following relationship is satisfied:
5. the filter of claim 1, wherein an anti-resonant frequency of the first resonator is less than a resonant frequency of any one of the parallel arm resonators.
6. A filter according to claim 1 or 3, wherein the number of first resonators is N, the number of second resonators is M, N is less than or equal to M, and N and M are integers greater than 1;
each of the first resonators is connected in parallel with at least one of the second resonators.
7. The filter according to any of claims 1-5, characterized in that the second target frequency point f on the high frequency side outside the filter passband 3 Static capacitance C of the second resonator 01 Dynamic capacitance C of the second resonator m1 Static capacitance C of the first resonator 0x And an anti-resonant frequency f of the second resonator 4 The following relationship is satisfied:
8. the filter of any of claims 1-5, wherein a static capacitance of the first resonator is less than a static capacitance of the second resonator.
9. The filter of any of claims 1-5, wherein the first resonator and the second resonator are bulk acoustic wave resonators, and wherein an effective area of the first resonator is smaller than an effective area of the second resonator.
10. The filter of any of claims 1-5, wherein a static capacitance of the first resonator is greater than or equal to a static capacitance of the parallel arm resonator.
11. The filter of any of claims 1-5, wherein the series-arm resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator;
the parallel arm resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator;
the first resonator is at least one of a bulk acoustic wave resonator and a surface acoustic wave resonator.
12. A multiplexer comprising a filter as claimed in any one of claims 1 to 11.
13. A radio frequency front end module comprising the filter of any of claims 1-11.
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