CN112491384A - FBAR filter circuit - Google Patents
FBAR filter circuit Download PDFInfo
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- CN112491384A CN112491384A CN202011359313.8A CN202011359313A CN112491384A CN 112491384 A CN112491384 A CN 112491384A CN 202011359313 A CN202011359313 A CN 202011359313A CN 112491384 A CN112491384 A CN 112491384A
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- 238000001914 filtration Methods 0.000 claims abstract description 45
- 238000006880 cross-coupling reaction Methods 0.000 claims abstract description 41
- 230000005540 biological transmission Effects 0.000 claims abstract description 13
- 239000010408 film Substances 0.000 claims description 50
- 239000003990 capacitor Substances 0.000 claims description 43
- 239000010409 thin film Substances 0.000 claims description 20
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 239000000758 substrate Substances 0.000 claims description 3
- 238000003780 insertion Methods 0.000 abstract description 5
- 230000037431 insertion Effects 0.000 abstract description 5
- 238000010586 diagram Methods 0.000 description 9
- 238000004891 communication Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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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
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
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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
- H03H9/25—Constructional features of resonators using surface acoustic waves
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Abstract
The invention is suitable for the technical field of filters, and provides an FBAR filter circuit, which comprises: one end of the cross coupling module is connected with the first end of the filtering module and then used as the input end of the FBAR filter circuit, the other end of the cross coupling module is connected with the third end of the filtering module, and the third end of the filtering module is used as the output end of the FBAR filter circuit; or one end of the cross coupling module is connected with the third end of the filtering module and then serves as the output end of the FBAR filter circuit, and the other end of the cross coupling module is connected with the fourth end of the filtering module; the cross coupling module is used for forming a transmission zero point at a high frequency band outside a pass band of the FBAR filter circuit, so that out-of-band rejection can be improved, the size of a chip of the original FBAR filter cannot be greatly increased due to components in the cross coupling module, the introduction of an inductor can be reduced, and more loss and in-band insertion loss cannot be introduced and deteriorated.
Description
Technical Field
The invention belongs to the technical field of filters, and particularly relates to a Film Bulk Acoustic Resonator (FBAR) filter circuit.
Background
With the rapid development of wireless communication technology, many rf devices are widely used in the communication field, for example, a large number of filters are used in personal mobile terminals such as mobile phones. The filter is mainly used for filtering out unwanted radio frequency signals and improving the performance of a transmitting path or a receiving path. At present, a communication system develops towards a multi-band, multi-system and multi-mode direction, the used frequency bands are more and more dense, in order to improve the communication quality and reduce the interference between the frequency bands, a higher requirement is bound to be put forward on the out-of-band rejection of a filter, the prior art generally adopts the increase of the number of stages of the filter to improve the out-of-band rejection, and more loss and in-band insertion loss are introduced.
Disclosure of Invention
In view of the above, embodiments of the present invention provide an FBAR filter circuit, which aims to solve the problems of more loss and deterioration of in-band insertion loss when high suppression is implemented in the prior art.
To achieve the above object, a first aspect of an embodiment of the present invention provides an FBAR filter circuit, including: the device comprises a cross coupling module and a filtering module;
one end of the cross coupling module is connected with the first end of the filtering module and then used as the input end of the FBAR filter circuit, the other end of the cross coupling module is connected with the second end of the filtering module, and the third end of the filtering module is used as the output end of the FBAR filter circuit;
or, one end of the cross-coupling module is connected to the third end of the filtering module and then serves as the output end of the FBAR filter circuit, the other end of the cross-coupling module is connected to the fourth end of the filtering module, and the first end of the filtering module serves as the input end of the FBAR filter circuit;
the cross coupling module is used for forming transmission zero at a high frequency band outside the passband of the FBAR filter circuit.
As another embodiment of the present application, the filtering module includes: a series circuit and a plurality of parallel circuits;
the series circuit is formed by connecting a plurality of resonators in series, one end of the series circuit is a first end of the filter module, and the other end of the series circuit is a third end of the filter module;
each parallel circuit is formed by connecting resonators and grounding inductors in series, one end of each resonator in each parallel circuit is connected between adjacent resonators in the series circuit or between any end in the series circuit and the adjacent resonators, and one end of each grounding inductor in each parallel circuit is grounded.
As another embodiment of the present application, the resonator is a thin film bulk acoustic resonator, and the thin film bulk acoustic resonator adopts an air cavity structure or a solid state fabricated structure.
As another embodiment of the present application, the number of thin film bulk acoustic resonators connected in series in the series circuit is any one of 1 to 5;
the number of the parallel circuits is any one of 1 to 5.
As another embodiment of the present application, the series circuit further comprises an input lead inductance and an output lead inductance;
one end of the input lead inductor is a first end of the filtering module, the other end of the input lead inductor is connected with four film bulk acoustic resonators connected in series and then is connected with one end of the output lead inductor, and the other end of the output lead inductor is a third end of the filtering module.
As another embodiment of the present application, the input lead inductance and the output lead inductance are any one of a bonding wire, an inductance implemented by using a GaAs substrate, an inductance implemented by using a ceramic sheet, and a surface mount inductance.
As another embodiment of the present application, the cross-coupling module includes: a capacitance C1;
one end of the capacitor C1 is connected between the input lead inductance and the adjacent first film bulk acoustic resonator, and the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the grounding inductance in the parallel circuit closest to the first film bulk acoustic resonator;
or one end of the capacitor C1 is connected between the output lead inductance and the adjacent fourth film bulk acoustic resonator; the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the ground inductor in the parallel circuit closest to the fourth film bulk acoustic resonator.
As another embodiment of the present application, the capacitance value of the capacitor C1 is obtained according to the frequency value of the transmission zero point position, the grounding inductance connected in series with the capacitor C1, and the equivalent circuit corresponding to the two fbw resonators connected in parallel with the capacitor C1.
As another embodiment of the present application, an equivalent circuit of the two film bulk acoustic resonators corresponding to the resonant frequency includes: a capacitor C2 and a capacitor C3 connected in series.
As another embodiment of the present application, the capacitance value of the capacitor C1 is 0.5 pF.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: compared with the prior art, the cross-coupling module can form a transmission zero outside the passband of the FBAR filter circuit in a high-frequency band, so that out-of-band rejection can be improved. And the components in the cross-coupling module cannot cause the chip volume of the filtering module to be greatly increased, and the introduction of an inductor can be reduced, so that the FBAR filter circuit has smaller volume, and cannot introduce more loss and deteriorate in-band insertion loss.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1(1) is a schematic diagram of an FBAR filter circuit according to an embodiment of the present invention;
FIG. 1(2) is a schematic diagram of another FBAR filter circuit according to an embodiment of the present invention;
FIG. 2 is a circuit diagram of a filter module according to an embodiment of the present invention;
fig. 3 is a schematic diagram of an amplitude-frequency characteristic curve corresponding to a filtering module according to an embodiment of the present invention;
FIG. 4 is a circuit diagram of an exemplary FBAR filter circuit provided by an embodiment of the invention;
FIG. 5 is a circuit diagram of another FBAR filter circuit according to an embodiment of the present invention;
fig. 6 is a schematic diagram of amplitude-frequency characteristic curves of an FBAR filter circuit according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a circuit for calculating the capacitance C1 according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Fig. 1(1) and fig. 1(2) are schematic diagrams of an FBAR filter circuit according to an embodiment of the present invention, including: a cross coupling module 10 and a filtering module 20;
as shown in fig. 1(1), one end of the cross-coupling module 10 is connected to the first end of the filtering module 20 and then serves as an input end of the FBAR filter circuit, the other end of the cross-coupling module 10 is connected to the second end of the filtering module 20, and the third end of the filtering module 20 serves as an output end of the FBAR filter circuit;
or, as shown in fig. 1(2), one end of the cross-coupling module 10 is connected to the third end of the filtering module 20 and then serves as an output end of the FBAR filter circuit, the other end of the cross-coupling module 10 is connected to the fourth end of the filtering module 20, and the first end of the filtering module 20 serves as an input end of the FBAR filter circuit;
the cross-coupling module 10 is used for forming a transmission zero point at a high frequency band outside the passband of the FBAR filter circuit, thereby improving out-of-band rejection.
Optionally, as shown in fig. 2, the filtering module 20 includes: a series circuit and a plurality of parallel circuits;
the series circuit is formed by connecting a plurality of resonators in series, one end of the series circuit is a first end of the filter module 20, and the other end of the series circuit is a third end of the filter module 20;
each parallel circuit is formed by connecting resonators and grounding inductors in series, one end of each resonator in each parallel circuit is connected between adjacent resonators in the series circuit or between any end in the series circuit and the adjacent resonators, and one end of each grounding inductor in each parallel circuit is grounded.
Optionally, in this embodiment, the resonator is a film bulk acoustic resonator, and the film bulk acoustic resonator adopts an Air cavity (Air gap) structure or a Solid state assembled resonator (SMR) structure.
The number of the film bulk acoustic resonators connected in series in the series circuit is any one of 1 to 5, that is, the series circuit is formed by connecting 1 film bulk acoustic resonator, or the series circuit is formed by connecting 2 film bulk acoustic resonators in series, or the series circuit is formed by connecting 3 film bulk acoustic resonators in series, or the series circuit is formed by connecting 4 film bulk acoustic resonators in series, or the series circuit is formed by connecting 5 film bulk acoustic resonators in series.
The following description will be made taking an example in which 4 thin film bulk acoustic resonators are connected in series to form a series circuit, and as shown in fig. 2, the series circuit is composed of a thin film bulk acoustic resonator X1, a thin film bulk acoustic resonator X2, a thin film bulk acoustic resonator X3, and a thin film bulk acoustic resonator X4, which are connected in series in this order.
Optionally, the series circuit further comprises an input lead inductance L1 and an output lead inductance L2;
one end of the input lead inductor L1 is the first end of the filter module, the other end of the input lead inductor L1 is connected to four film bulk acoustic resonators connected in series and then connected to one end of the output lead inductor L2, and the other end of the output lead inductor L2 is the third end of the filter module 20. As shown in fig. 2, an input lead inductor L1 is connected between the thin film bulk acoustic resonator X1 and the first end of the filter module 20, and an input lead inductor L2 is connected between the thin film bulk acoustic resonator X4 and the third end of the filter module 20.
Optionally, the number of parallel circuits is any one of 1 to 5. When the number of the parallel circuits is three, as shown in fig. 2, one end of the film bulk acoustic resonator X5 is connected between the film bulk acoustic resonator X1 and the film bulk acoustic resonator X2, and the other end of the film bulk acoustic resonator X5 is grounded after being connected in series with the grounding inductor L3;
one end of the film bulk acoustic resonator X6 is connected between the film bulk acoustic resonator X2 and the film bulk acoustic resonator X3, and the other end of the film bulk acoustic resonator X6 is grounded after being connected with a grounding inductor L4 in series;
one end of the film bulk acoustic resonator X7 is connected between the film bulk acoustic resonator X3 and the film bulk acoustic resonator X4, and the other end of the film bulk acoustic resonator X7 is grounded after being connected in series with a grounding inductor L5.
Note that when only one thin film bulk acoustic resonator X1 is present in the series circuit, the parallel circuit may be connected between the input lead inductance L1 and the thin film bulk acoustic resonator X1, and/or between the output lead inductance L2 and the thin film bulk acoustic resonator X1.
Optionally, the input lead inductor L1 and the output lead inductor L2 may be any one of a bonding wire, an inductor implemented by using a GaAs substrate, an inductor implemented by using a ceramic chip, and a surface-mounted inductor.
Corresponding to the amplitude-frequency characteristic curve of the filter module shown in fig. 2, as shown in fig. 3, the abscissa represents frequency in GHz and the ordinate represents attenuation in dB.
Optionally, the cross-coupling module 10 includes: a capacitance C1;
one end of the capacitor C1 is connected between the input lead inductor L1 and the immediately adjacent first film bulk acoustic resonator, and the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the grounding inductor in the parallel circuit closest to the first film bulk acoustic resonator.
As shown in fig. 4, one end of the capacitor C1 is connected between the input lead inductance L1 and the thin film bulk acoustic resonator X1, and the other end of the capacitor C1 is connected between the thin film bulk acoustic resonator X5 and the ground inductance L3.
Or one end of the capacitor C1 is connected between the output lead inductance and the adjacent fourth film bulk acoustic resonator; the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the ground inductor in the parallel circuit closest to the fourth film bulk acoustic resonator.
As shown in fig. 5, one end of the capacitor C1 is connected between the output lead inductor L2 and the film bulk acoustic resonator X4, and the other end of the capacitor C1 is connected between the film bulk acoustic resonator X7 and the ground inductor L5.
By adopting the structure of the cross coupling module and the filtering module, the grounding inductor L3 or L5 in the filtering module is part of the cross coupling module at the same time, so that one inductor is reduced in the circuit of the FBAR filter circuit, and the chip volume of the FBAR filter circuit can be reduced.
The amplitude-frequency characteristic of the FBAR filter circuit shown in fig. 6 provides a transmission zero at a frequency of about 5.5 GHz.
Optionally, in fig. 4 or 5, the capacitance value of the capacitor C1 is obtained according to the frequency value of the transmission zero position, the grounding inductor connected in series with the capacitor C1, and the equivalent circuit corresponding to the two film bulk acoustic wave resonators connected in parallel with the capacitor C1.
Alternatively, when the frequency is higher than the anti-resonator frequency of the film bulk acoustic resonator, the resonator is capacitive and can be equivalent to a capacitor, so that an equivalent circuit of two film bulk acoustic resonators X1 and X5 connected in parallel with the capacitor C1 at a position far from the resonance frequency includes: a capacitor C2 and a capacitor C3 connected in series. Therefore, as shown in fig. 7, one end of the capacitor C2 is connected to one end of the capacitor C1, the other end of the capacitor C2 is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the other end of the capacitor C1 and one end of the grounding inductor L3, and the other end of the grounding inductor L3 is grounded.
The capacitance values of the equivalent capacitors C2 and C3 can be determined by C in the corresponding MBVD equivalent circuit0Equivalently, the calculation formula is: c0ε A/d. Where ε is the dielectric constant of the piezoelectric material, A is the area of the acoustic wave resonator, and d is the thickness of the piezoelectric material. Therefore, the transmission zero at 5.5GHz in fig. 6 is provided by the thin film bulk acoustic resonators X1 and X5 (equivalent to capacitances C2 and C3), capacitance C1, and ground inductance L3, so that the circuit shown in fig. 7 can well exhibit the position of the transmission zero after the cross-coupling is introduced, all at 5.5 GHz. Therefore, the value of the capacitance C1 introduced into the cross coupling can be determined by the frequency value of the transmission zero position, the grounding inductance L3, and the MBVD equivalent circuit capacitance values C2 and C3 of the film bulk acoustic resonator. Optionally, the capacitance value of the capacitor C1 is 0.5pF, and the capacitance value is moderate, which does not cause a large increase in chip volume. Similarly, when the capacitor C1 is connected in parallel with the film bulk acoustic resonators X4 and X7, the capacitance value is calculated in the same manner as described above.
In this embodiment, comparing fig. 6 with fig. 3, the out-of-band attenuation corresponding to the frequency of about 5.5GHz before the introduction of the cross-coupling module in fig. 3 is about 31dB, and the out-of-band attenuation at this point after the introduction of the cross-coupling module in fig. 6 is about 51dB, which is about 20dB better.
One end of the cross coupling module is connected with the first end of the filtering module and then used as the input end of the FBAR filter circuit, the other end of the cross coupling module is connected with the second end of the filtering module, and the third end of the filtering module is used as the output end of the FBAR filter circuit; or one end of the cross coupling module is connected with the third end of the filtering module and then used as the output end of the FBAR filter circuit, the other end of the cross coupling module is connected with the fourth end of the filtering module, and the first end of the filtering module is used as the input end of the FBAR filter circuit; the cross coupling module is used for forming a transmission zero point at a high frequency band outside the passband of the FBAR filter circuit, so that out-of-band rejection can be improved. And the components in the cross-coupling module cannot cause the chip volume of the filtering module to be greatly increased, and the introduction of an inductor can be reduced, so that the FBAR filter circuit has smaller volume, and cannot introduce more loss and deteriorate in-band insertion loss.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
Claims (10)
1. An FBAR filter circuit, comprising: the device comprises a cross coupling module and a filtering module;
one end of the cross coupling module is connected with the first end of the filtering module and then used as the input end of the FBAR filter circuit, the other end of the cross coupling module is connected with the second end of the filtering module, and the third end of the filtering module is used as the output end of the FBAR filter circuit;
or, one end of the cross-coupling module is connected to the third end of the filtering module and then serves as the output end of the FBAR filter circuit, the other end of the cross-coupling module is connected to the fourth end of the filtering module, and the first end of the filtering module serves as the input end of the FBAR filter circuit;
the cross coupling module is used for forming transmission zero at a high frequency band outside the passband of the FBAR filter circuit.
2. The FBAR filter circuit of claim 1, wherein the filtering module comprises: a series circuit and a plurality of parallel circuits;
the series circuit is formed by connecting a plurality of resonators in series, one end of the series circuit is a first end of the filter module, and the other end of the series circuit is a third end of the filter module;
each parallel circuit is formed by connecting resonators and grounding inductors in series, one end of each resonator in each parallel circuit is connected between adjacent resonators in the series circuit or between any end in the series circuit and the adjacent resonators, and one end of each grounding inductor in each parallel circuit is grounded.
3. The FBAR filter circuit of claim 2 wherein the resonator is a thin film bulk acoustic resonator, the thin film bulk acoustic resonator being in an air cavity configuration or a solid state fabricated configuration.
4. The FBAR filter circuit according to claim 2 or 3, wherein the number of thin film bulk acoustic resonators connected in series in the series circuit is any one of 1 to 5;
the number of the parallel circuits is any one of 1 to 5.
5. The FBAR filter circuit of claim 4, wherein the series circuit further includes an input lead inductance and an output lead inductance;
one end of the input lead inductor is a first end of the filtering module, the other end of the input lead inductor is connected with four film bulk acoustic resonators connected in series and then is connected with one end of the output lead inductor, and the other end of the output lead inductor is a third end of the filtering module.
6. The FBAR filter circuit of claim 5,
the input lead inductance and the output lead inductance are any one of a bonding wire, an inductance realized by adopting a GaAs substrate, an inductance realized by adopting a ceramic chip and a surface-mounted inductance.
7. The FBAR filter circuit of claim 5, wherein the cross-coupling module comprises: a capacitance C1;
one end of the capacitor C1 is connected between the input lead inductance and the adjacent first film bulk acoustic resonator, and the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the grounding inductance in the parallel circuit closest to the first film bulk acoustic resonator;
or one end of the capacitor C1 is connected between the output lead inductance and the adjacent fourth film bulk acoustic resonator; the other end of the capacitor C1 is connected between the film bulk acoustic resonator and the ground inductor in the parallel circuit closest to the fourth film bulk acoustic resonator.
8. The FBAR filter circuit as claimed in claim 7, wherein the capacitance value of the capacitor C1 is obtained from a frequency value of a transmission zero position, a ground inductance connected in series with the capacitor C1, and an equivalent circuit corresponding to two fbw resonators connected in parallel with the capacitor C1.
9. The FBAR filter circuit of claim 8 wherein the equivalent circuit for the two thin film bulk acoustic resonators at frequencies away from resonance comprises: a capacitor C2 and a capacitor C3 connected in series.
10. The FBAR filter circuit of claim 9 wherein the capacitance C1 has a capacitance of 0.5 pF.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011359313.8A CN112491384A (en) | 2020-11-27 | 2020-11-27 | FBAR filter circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011359313.8A CN112491384A (en) | 2020-11-27 | 2020-11-27 | FBAR filter circuit |
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| CN112491384A true CN112491384A (en) | 2021-03-12 |
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| CN202011359313.8A Pending CN112491384A (en) | 2020-11-27 | 2020-11-27 | FBAR filter circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113556095A (en) * | 2021-07-23 | 2021-10-26 | 北京中科汉天下电子技术有限公司 | Cross-coupled acoustic filter |
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| US20110018654A1 (en) * | 2009-07-27 | 2011-01-27 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Resonator filter with multiple cross-couplings |
| US20110018653A1 (en) * | 2009-07-27 | 2011-01-27 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Duplexer having resonator filters |
| CN111162752A (en) * | 2020-01-14 | 2020-05-15 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave filter |
| CN111313862A (en) * | 2020-02-26 | 2020-06-19 | 诺思(天津)微系统有限责任公司 | Method for adjusting filter circuit, filter, multiplexer and communication equipment |
| CN111342793A (en) * | 2018-12-18 | 2020-06-26 | 天津大学 | Band-pass filter, method for improving suppression level of band-pass filter, duplexer, and electronic apparatus |
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2020
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Patent Citations (5)
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| US20110018654A1 (en) * | 2009-07-27 | 2011-01-27 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Resonator filter with multiple cross-couplings |
| US20110018653A1 (en) * | 2009-07-27 | 2011-01-27 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Duplexer having resonator filters |
| CN111342793A (en) * | 2018-12-18 | 2020-06-26 | 天津大学 | Band-pass filter, method for improving suppression level of band-pass filter, duplexer, and electronic apparatus |
| CN111162752A (en) * | 2020-01-14 | 2020-05-15 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113556095A (en) * | 2021-07-23 | 2021-10-26 | 北京中科汉天下电子技术有限公司 | Cross-coupled acoustic filter |
| CN113556095B (en) * | 2021-07-23 | 2024-04-19 | 北京中科汉天下电子技术有限公司 | Cross-coupled acoustic filter |
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Application publication date: 20210312 |