Broadband high-steep-drop filter with embedded piezoelectric acoustic resonator and LC passive circuit

Abstract

The invention discloses a broadband high-steep-drop filter based on embedding of a piezoelectric acoustic resonator and an LC passive circuit, and the filter comprises a stepped filter network and an LC resonant network, the stepped filter network and the LC resonant network are sequentially connected in series, or the stepped filter network and the LC resonant network are sequentially connected in series at intervals; the stepped filter network comprises a filter series trunk and a plurality of filter parallel branches, a first end of the filter series trunk is used as an input end, and two ends of the filter parallel branches are respectively connected to a ground wire and the series trunk; at least one series-connection mixed resonance unit is arranged on the filtering series-connection trunk and is used for forming a pole in a passband to expand the bandwidth of the passband; the filtering parallel branch is provided with at least one acoustic resonator or a parallel hybrid resonance unit. The wave filter can realize relatively high bandwidth, relatively high out-of-band rejection and relatively narrow transition zone.

Description

Technical Field

[0001] The invention belongs to the technical field of filter devices, and in particular relates to a broadband high steep drop filter in which a piezoelectric acoustic resonator and an LC passive circuit are embedded. Background Art

[0002] As wireless communications evolve from 4G to 5G and 6G, the standards define more and more frequency bands. An obvious trend can be observed that 5G, 6G and higher versions are adopting wider bandwidths. For example, band n77 requires 900 MHz bandwidth, while the 4G band only requires 60 MHz bandwidth.

[0003] LC filters based on traditional IPD and LTCC technologies are suitable for large-bandwidth applications, such as 5G sub-6 GHz and millimeter-wave bands, but the low Q of the lumped elements themselves makes it difficult to achieve the narrow transition band requirements required by the rapid increase in the number of communication frequency bands.

[0004] The invention patent application with publication number CN116865714A discloses a filter for the N79 frequency band, including: at least one acoustic resonator and an IPD filter circuit; wherein the acoustic resonator and the IPD filter circuit are connected in series in sequence, or the acoustic resonator and the IPD filter circuit are connected in series at intervals; the IPD filter circuit is used to form a passband in the N79 frequency band. The filter for the N79 frequency band adopts the integration technology of acoustic resonator and IPD filter circuit to achieve the target requirements. Both adopt semiconductor processing technology and can be processed and manufactured on the same wafer. In addition, the circuit and structure of the filter can have the characteristics of large bandwidth and fast roll-off, and can simultaneously achieve low insertion loss in the N79 frequency band and high suppression of WiFi 6E.

[0005] The utility model patent application with publication number CN218570205U discloses a radio frequency filter topology structure, including an input end, an output end, a series branch, a first parallel branch, and a second parallel branch, wherein both ends of the series branch and the first parallel branch are connected to the input end and the output end respectively; the series branch is provided with a first capacitor and a second capacitor in sequence, the first parallel branch is provided with a resonator, and the second parallel branch is provided with an inductor, one end of the inductor is connected between the first capacitor and the second capacitor, and the other end is grounded. The utility model uses a single resonator external circuit to form a filter, which greatly reduces the area of ​​the filter composed of multiple resonators in series and parallel, and its size can be within 1mm*1mm, which greatly reduces the manufacturing cost, can be highly integrated, and meet the miniaturization requirements of radio frequency front-end module components; and can achieve large bandwidth and high suppression requirements, especially the out-of-band zero point position can be flexibly adjusted.

[0006] Although the above-mentioned patent can form an extremely narrow transition band, the passband bandwidth can be further widened to meet the requirements of 5G, 6G and higher versions for high passband bandwidth. Therefore, it is urgent to design a filter that can achieve higher bandwidth, out-of-band suppression and narrower transition band. Summary of the invention

[0007] The invention provides a broadband high steep drop filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit, wherein the filter can achieve higher bandwidth, higher out-of-band suppression and narrower transition band.

[0008] A specific embodiment of the present invention provides a broadband high steep drop filter based on an embedded piezoelectric acoustic resonator and an LC passive circuit, comprising a ladder-type filter network and an LC resonance network, wherein the ladder-type filter network and the LC resonance network are sequentially connected in series, or the ladder-type filter network and the LC resonance network are sequentially connected in series and alternately connected in series; The ladder filter network comprises a filter series trunk and a plurality of filter parallel branches, wherein the first end of the filter series trunk serves as an input end, and the two ends of the filter parallel branches are respectively connected to the ground wire and the series trunk; At least one series hybrid resonance unit is arranged on the filter series trunk line, and the series hybrid resonance unit is used to form a pole in the passband to expand the passband bandwidth; At least one acoustic resonator or parallel hybrid resonance unit is arranged on the filtering parallel branch.

[0009] Preferably, the series hybrid resonance unit is composed of a capacitor and an inductor connected in series or an acoustic resonator and an inductor connected in series; The parallel hybrid resonance unit is used to generate a zero point outside the passband to achieve out-of-band suppression.

[0010] Compared with the prior art, the present invention proposes that a parallel hybrid resonance unit is provided on the series trunk line of a traditional ladder-type filter network, and by adjusting specific parameters of the parallel hybrid resonance unit, such as the inductance value, the capacitance value or the parameters of the acoustic resonator, the parallel hybrid resonance unit can generate a transmission pole in the collapsed region of the passband, thereby widening the bandwidth of the passband. In particular, the present invention can achieve widening of the passband bandwidth and avoid degradation of insertion loss by forming a parallel hybrid resonance unit by connecting an acoustic resonator and an inductor in series.

[0011] Preferably, the parallel hybrid resonance unit is composed of a capacitor and an inductor connected in series to achieve out-of-band suppression at one end of the passband.

[0012] Preferably, the parallel hybrid resonance unit is composed of an acoustic resonator and an inductor connected in series to achieve out-of-band suppression at both ends of the passband.

[0013] Compared with the prior art, the parallel hybrid resonance unit provided by the present invention is composed of an acoustic resonator and an inductor connected in series, so that out-of-band suppression can be efficiently achieved at both ends of the passband through a parallel hybrid resonance unit, avoiding a complex circuit structure.

[0014] Preferably, the LC resonant network comprises a resonant series trunk and a plurality of resonant parallel branches, the first end of the resonant series trunk is connected to the second end of the filtering series trunk, the second end of the resonant series trunk serves as an output end, and the two ends of the resonant parallel branches are respectively connected to the ground wire and the resonant trunk; The resonant series trunk circuit is provided with a plurality of series capacitors; The resonant parallel branch is provided with a parallel hybrid resonance unit.

[0015] The present invention realizes generating a zero point at a low frequency to achieve out-of-band suppression and a faster transition band through the parallel hybrid resonance unit of the LC resonance network, and realizes a wider passband at a high frequency in cooperation with the series capacitor on the resonance series trunk line.

[0016] Preferably, the plurality of filtering parallel branches include a first filtering parallel branch, a second filtering parallel branch and a third filtering parallel branch; The LC resonant network comprises a resonant series trunk circuit, a first resonant parallel branch circuit and a second resonant parallel branch circuit; The filter series trunk is provided with a first series hybrid resonance unit and a second series hybrid resonance unit; The first filtering parallel branch is provided with a first acoustic resonator and a second acoustic resonator connected in series; A third acoustic resonator is provided on the second filtering parallel branch; The third filtering parallel branch is provided with a fourth acoustic resonator and a fifth acoustic resonator connected in series; The resonant series trunk circuit is provided with a first capacitor, a second capacitor and a third capacitor; The first resonant parallel branch is provided with a first parallel hybrid resonant unit; The second resonant parallel branch is provided with a second parallel hybrid resonant unit; The first parallel hybrid resonance unit and the second parallel hybrid resonance unit are both composed of a capacitor and an inductor connected in series; The first end of the first acoustic resonator is connected to the first end and the input end of the first series hybrid resonance unit respectively, the second end of the first acoustic resonator is connected to the first end of the second acoustic resonator, and the second end of the second acoustic resonator is connected to the ground wire; The first end of the third acoustic resonator is connected to the second end of the first series hybrid resonator unit and the first end of the second series hybrid resonator unit respectively, and the second end of the third acoustic resonator is connected to the ground wire; The first end of the fourth acoustic resonator is connected to the second end of the second series hybrid resonance unit and the first end of the first capacitor respectively, the second end of the fourth acoustic resonator is connected to the first end of the fifth acoustic resonator, and the second end of the fifth acoustic resonator is connected to the ground wire; The first end of the first parallel hybrid resonance unit is connected to the second end of the first capacitor and the first end of the second capacitor respectively, and the second end of the first parallel hybrid resonance unit is connected to the ground line; The first end of the second parallel hybrid resonance unit is connected to the second end of the second capacitor and the first end of the third capacitor respectively, and the second end of the second parallel hybrid resonance unit is connected to the ground line; The second end of the third capacitor is connected to the output end.

[0017] Further preferably, the first, second, third, fourth and fifth acoustic resonators are all used to generate transmission zeros at 4.95-5.05 GHz for forming an extremely fast transition band, and at the same time generate transmission poles at 5.15-5.3 GHz to reduce passband insertion loss; The first and second series hybrid resonant units are used to generate transmission poles at (6.1-6.5 GHz and 5.15-5.3 GHz respectively to widen the passband; The first parallel hybrid resonance unit is used to generate a transmission zero point at 4.05 GHz-4.25 GHz to achieve an out-of-band suppression effect; The second parallel hybrid resonance unit is used to generate a transmission zero point at 4.55 GHz-4.75 GHz to achieve an out-of-band suppression effect.

[0018] Compared with the prior art, the transmission poles generated by the first and second series hybrid resonance units provided by the present invention enable the passband bandwidth to reach a wider range of more than 500 MHz, and multiple stepped transmission zeros are generated through the first, second, third, fourth and fifth acoustic resonators, thereby forming a narrow and rapidly declining transition band, and the passband insertion loss is reduced through the generated transmission poles.

[0019] Preferably, the acoustic resonator comprises a bulk acoustic wave resonator.

[0020] Preferably, the acoustic resonator embedded filter further comprises: an impedance matching unit located between the ladder-type filter network and the LC resonance network.

[0021] Further preferably, the impedance matching unit is a fourth capacitor.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention sets at least one series hybrid resonance unit on the filter series trunk line of the ladder filter network, so that one or more transmission poles can be formed on the passband to support the passband, thereby widening the passband to meet the requirements of 5G, 6G and higher versions for high passband bandwidth. The present invention sets an acoustic resonator on the filter parallel branch, and uses the acoustic resonator to generate a zero point in the transition band to achieve a narrower transition band. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a ladder-type filter network composed of acoustic resonators provided in a specific embodiment of the present invention; Figure 2 A schematic diagram of a traditional LC resonant network provided for a specific embodiment of the present invention; Figure 3 A schematic diagram of a broadband high steep drop filter based on an embedded piezoelectric acoustic resonator and an LC passive circuit provided in a specific embodiment of the present invention; Figure 4 A schematic diagram of an S-parameter curve of a broadband high-steep-drop filter based on an embedded piezoelectric acoustic resonator and an LC passive circuit provided in a specific embodiment of the present invention; Figure 5 A schematic diagram of another broadband high steep drop filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit provided in a specific embodiment of the present invention; Figure 6 A schematic diagram of an S-parameter curve of another broadband high steep drop filter based on an embedded piezoelectric acoustic resonator and an LC passive circuit is provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following is a detailed description in conjunction with specific implementation examples. The following examples are only relevant parts of the present invention, which will help relevant personnel understand the principles of the present invention and do not limit the present invention in any way. It should be noted that corresponding structural adjustments and changes can be made based on the concept of the present invention, and such changes all belong to the protection scope of the present invention.

[0025] In order to achieve a large passband, a narrow transition band and the required out-of-band suppression, the present invention embeds a series hybrid resonance unit in a ladder-type filter network composed of acoustic resonators to widen the passband, and embeds a parallel hybrid resonance unit on the basis of a traditional LC resonance network to achieve out-of-band suppression.

[0026] like Figure 1As shown, a specific embodiment of the present invention provides a ladder-type filter network composed of acoustic resonators, which consists of two series resonators AS and a parallel resonator AP, wherein one end of the parallel resonator is connected between two adjacent series resonators, and one end includes but is not limited to grounding. The resonant network can obtain a bandpass filtering effect with a very deep and steep skirt through the transmission zeros and transmission poles generated by the acoustic resonator.

[0027] like Figure 2 As shown, the traditional LC resonant network consists of a series branch (several series capacitors C S ) and several parallel branches (C P With L P ) is composed of a high-pass, band-pass, and low-pass filter with good insertion loss effect and zero points at different positions can be obtained by increasing the order and optimizing the parameter values ​​of each component.

[0028] A broadband high steep drop filter based on an embedded piezoelectric acoustic resonator and an LC passive circuit provided in a specific embodiment of the present invention comprises a ladder-type filter network and an LC resonance network, wherein the ladder-type filter network and the LC resonance network are sequentially connected in series, or the ladder-type filter network and the LC resonance network are sequentially connected in series with an interval.

[0029] The ladder-type filter network provided in the specific embodiment of the present invention is obtained by replacing some acoustic resonators with series hybrid resonance units or parallel hybrid resonance units in the ladder-type filter network composed of acoustic resonators.

[0030] The LC resonant network provided in the specific embodiment of the present invention is a conventional LC resonant network with some parallel branches (C P With L P ) is replaced by a parallel hybrid resonant unit.

[0031] The series hybrid resonance unit provided in the specific embodiment of the present invention is composed of a capacitor and an inductor connected in series or an acoustic resonator and an inductor connected in series, and is used to generate a transmission pole at the collapse of the passband to support the passband and thus widen the passband.

[0032] The parallel hybrid resonance unit provided in the specific embodiment of the present invention is composed of a capacitor and an inductor connected in series to achieve out-of-band suppression at one end of the passband.

[0033] In a specific embodiment, if Figure 3 As shown, a broadband high steep drop filter based on a piezoelectric acoustic resonator and an embedded LC passive circuit provided in a specific embodiment of the present invention includes a ladder-type filter network and an LC resonance network. The ladder-type filter network includes a filter series main circuit, a first filter parallel branch, a second filter parallel branch and a third filter parallel branch.

[0034] The specific embodiment of the present invention provides a first series hybrid resonance unit and a second series hybrid resonance unit on the filter series main circuit. The specific embodiment of the present invention provides a first filter parallel branch with a first acoustic resonator Res1 and a second acoustic resonator Res2 connected in series, a third acoustic resonator Res3 on the second filter parallel branch, and a fourth acoustic resonator Res4 and a fifth acoustic resonator Res5 connected in series on the third filter parallel branch.

[0035] The LC resonant network provided in a specific embodiment of the present invention includes a resonant series main circuit, a first resonant parallel branch and a second resonant parallel branch. The resonant series main circuit is provided with a first capacitor C1, a second capacitor C2 and a third capacitor C3. The first resonant parallel branch is provided with a first parallel hybrid resonant unit, and the second resonant parallel branch is provided with a second parallel hybrid resonant unit. The first parallel hybrid resonant unit and the second parallel hybrid resonant unit are both composed of a capacitor and an inductor in series.

[0036] The first end of the first acoustic resonator Res1 provided in the specific embodiment of the present invention is respectively connected to the first end and the input end of the first series hybrid resonance unit, the second end of the first acoustic resonator Res1 is connected to the first end of the second acoustic resonator Res2, and the second end of the second acoustic resonator Res2 is connected to the ground wire.

[0037] The first end of the third acoustic resonator Res3 provided in the specific embodiment of the present invention is respectively connected to the second end of the first series hybrid resonator unit and the first end of the second series hybrid resonator unit, and the second end of the third acoustic resonator Res3 is connected to the ground wire.

[0038] The first end of the fourth acoustic resonator Res4 provided in the specific embodiment of the present invention is respectively connected to the second end of the second series hybrid resonance unit and the first end of the first capacitor, the second end of the fourth acoustic resonator Res4 is connected to the first end of the fifth acoustic resonator Res5, and the second end of the fifth acoustic resonator Res5 is connected to the ground wire.

[0039] The first end of the first parallel hybrid resonance unit provided in the specific embodiment of the present invention is respectively connected to the second end of the first capacitor C1 and the first end of the second capacitor C2, the second end of the first parallel hybrid resonance unit is connected to the ground wire, the first end of the second parallel hybrid resonance unit is respectively connected to the second end of the second capacitor C2 and the first end of the third capacitor C3, the second end of the second parallel hybrid resonance unit is connected to the ground wire; the second end of the third capacitor C3 is connected to the output end.

[0040] like Figure 4 As shown, the series resonance frequency f of the first, second, third, fourth and fifth acoustic resonators provided by the specific embodiment of the present invention is sLocated at vertical line 4 (4.98GHz), f s The deep transmission zero point and high Q value of the bulk acoustic resonator make Figure 4 The curve has a very fast transition band, and its parallel resonant frequency f P Located at 5.1GHz, the transmission pole formed provides suitable insertion loss for the passband.

[0041] The first series hybrid resonance unit and the second series hybrid resonance unit provided in the specific embodiment of the present invention are both composed of a series acoustic resonator and an inductor. By adjusting the parameters of the first series hybrid resonance unit, a transmission pole is generated at 6.15 GHz (circle 6) to widen the passband, and a transmission zero is provided at 4.1 GHz (vertical line 1) to contribute to the out-of-band suppression at the far end on the left.

[0042] The specific embodiment of the present invention adjusts the parameters of the second series hybrid resonant unit to generate a transmission pole at 5.2 GHz (circle 5) to widen the passband, and at the same time provides a transmission zero at 4.4 GHz (the frequency corresponding to the vertical line 2) to contribute to the out-of-band suppression at the far left end.

[0043] The first capacitor C1, the second capacitor C2 and the third capacitor C3 provided in the specific embodiment of the present invention form a high-pass filter with the first parallel hybrid resonance unit and the second parallel hybrid resonance unit, thereby obtaining deeper out-of-band suppression farther to the left, and simultaneously co-optimizing impedance with the network at the left end to obtain lower in-band insertion loss, wherein the first parallel hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission zero point at 4.05GHz-4.25GHz (the frequency corresponding to the vertical line 1) to achieve an out-of-band suppression effect, and the second parallel hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission zero point at 4.55GHz-4.75GHz (the frequency corresponding to the vertical line 3) to achieve an out-of-band suppression effect.

[0044] like Figure 4 As shown, the circuit aims to have a passband of 5.15GHz-7.12GHz, with a fast steep drop on the left, and out-of-band suppression can reach below -20dB. As can be seen from the figure, the circuit can obtain a steep drop of about 400M on the left, and obtain the first zero point, which is provided by an acoustic resonator with a high Q value, and produces a suppression effect outside the band near the passband; the far-end zero point below 4.5GHz is achieved through LC elements and hybrid resonance units; at the same time, the additional transmission pole formed by the hybrid resonance unit maintains an ultra-large bandwidth of 1970MHz, and the minimum insertion loss in the passband is -1.35dB, and the insertion loss in the band is within -2.8dB.

[0045] In a specific embodiment, if Figure 5As shown, a broadband high steep drop filter based on a piezoelectric acoustic resonator and an embedded LC passive circuit provided in a specific embodiment of the present invention includes a ladder-type filter network and an LC resonance network. The ladder-type filter network and the LC resonance network provided in the specific embodiment of the present invention are connected in series in sequence with intervals, and a fourth capacitor is connected between the ladder-type filter network and the LC resonance network for impedance matching. The ladder-type filter network includes a filter series main circuit, a fourth filter parallel branch, and a fifth filter parallel branch.

[0046] The filter series trunk provided in the specific embodiment of the present invention is provided with a third series hybrid resonance unit, and the third series hybrid resonance unit is constructed by connecting an acoustic resonator and an inductor in series. The fourth filter parallel branch provided in the specific embodiment of the present invention is provided with a third parallel hybrid resonance unit, and the fifth filter parallel branch is provided with a sixth acoustic resonator Res6.

[0047] The LC resonant network provided in a specific embodiment of the present invention includes a resonant series main circuit, a third resonant parallel branch, a fourth resonant parallel branch and a fifth resonant parallel branch. The resonant series main circuit is provided with a fifth capacitor C5 and a sixth capacitor C6, the third resonant parallel branch is provided with a fourth parallel hybrid resonance unit, the fourth resonant parallel branch is provided with a fifth parallel hybrid resonance unit, the fifth resonant parallel branch is provided with a sixth parallel hybrid resonance unit, the fourth parallel hybrid resonance unit is constructed by a series acoustic resonator and an inductor, and the fifth parallel hybrid resonance unit and the sixth parallel hybrid resonance unit are both constructed by a capacitor and an inductor in series.

[0048] Figure 5 The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit shown uses an acoustic resonance network 1 and an LC resonance network 2 to form a basic ladder-type filter network. Through the replacement embedding of the hybrid resonance unit, the effect of large bandwidth, fast transition, and high out-of-band suppression is achieved. The acoustic resonator on the left has a high Q value, providing a very deep zero point and a very narrow transition skirt. The hybrid resonance unit ensures that there is no collapse in the band. The LC network on the right provides high-pass filtering performance to provide a more distant zero point to ensure out-of-band suppression.

[0049] like Figure 6 As shown, the third series hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission pole at 5.48 GHz (circle 5) to widen the passband and reduce the insertion loss, and together with the sixth acoustic resonator Res6 forms a large passband of the filter.

[0050] The resonant series trunk provided in the specific embodiment of the present invention is provided with a fifth capacitor C5 and a sixth capacitor C6 which together with the fourth parallel hybrid resonance unit, the fifth parallel hybrid resonance unit and the sixth parallel hybrid resonance unit form a high-pass filter and form good out-of-band suppression at low frequencies.

[0051] Among them, the fourth parallel hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission zero point at the near end of the right side of the passband (at the frequency corresponding to the vertical line 6), thereby forming a good suppression effect; the fifth parallel hybrid resonance unit and the sixth parallel hybrid resonance unit provided in the specific embodiment of the present invention generate transmission zero points at 3.25GHz and 4.5GHz on the left side of the passband (at the frequencies corresponding to the vertical lines 1 and 2), thereby forming a good suppression effect on the left side of the filter and achieving the target performance.

[0052] The sixth acoustic resonator Res6 provided in the specific embodiment of the present invention generates a transmission zero at 4.94 GHz (the frequency corresponding to the vertical line 4 ) to form a faster transition band.

[0053] The third parallel hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission zero at 4.85 GHz (the frequency corresponding to the vertical line 3), which has a good suppression effect on the near-end out-of-band on the left side of the filter, and simultaneously generates a transmission zero at the frequency corresponding to the vertical line 7 (8.25 GHz), which has a good suppression effect on the far-end on the right side of the filter.

[0054] Figure 6 The circuit shown is the S parameter simulation curve of the large broadband hybrid filter. The horizontal axis is the frequency in GHz, and the vertical axis is the insertion loss in dB. The target passband frequency of this circuit is 5.15-6GHz, the passband is an ultra-large bandwidth of 850MHz, and there is a fast steep drop on the left. From the curve, it can be found that the hybrid filter circuit achieves a steep drop characteristic of 350MHz, while the in-band insertion loss is more than -2.9dB, and the minimum in-band insertion loss is -1.5dB.

[0055] The specific embodiment of the present invention organically cooperates the acoustic resonator with the LC resonator, cleverly utilizes the high Q value of the acoustic resonator to avoid the defect of the low Q value of the lumped element, and utilizes the large bandwidth of the LC filter and the characteristics of the LC element and the acoustic resonator that can generate additional transmission zeros (poles) to resolve the deficiency of the low electromechanical coupling coefficient of the acoustic resonator, thereby designing a hybrid filter with ultra-large bandwidth and rapid steep drop, and the bandwidth can be flexibly adjusted by adjusting the LC element parameters, the effective area of ​​the acoustic resonator, etc., which provides a good solution to the challenges brought by the development of 4, 5, and 6G communication technologies, such as the WIFI 6E band with ultra-large bandwidth.

[0056] Compared with traditional LC filters and acoustic filters, the present invention has more excellent performance: (1) The present invention can obtain filtering performance with a large bandwidth and a high steep drop by cascading the acoustic resonance network 1 and the LC resonance network 2.

[0057] (2) The present invention optimizes the out-of-band performance of the filter by using the resonator and the inductor as a parallel branch to obtain an additional zero point. In addition, the resonator can be replaced with a capacitor and the capacitor parameters can be optimized to optimize the out-of-band performance further away.

[0058] (3) The present invention can improve the passband performance and out-of-band suppression by changing the number of acoustic resonant networks and LC resonant networks.

[0059] (4) The present invention can easily obtain deep out-of-band suppression of different frequencies and filters with better performance by adjusting the parameter values ​​of the lumped elements.

[0060] (5) The present invention replaces the capacitor and inductor in the resonance unit with an acoustic resonator to obtain a resonance unit with a higher Q value and achieve a fast and steep drop.

[0061] (6) The present invention can achieve different target performances by replacing different capacitor and inductor components with acoustic resonators and hybrid resonance units through an LC basic circuit.

[0062] (7) The present invention can flexibly adjust the bandwidth filter network by adjusting the number of hybrid resonance units, the parameters of the LC elements in the hybrid resonance units, the effective area of ​​the acoustic resonator, etc.

Claims

1. A broadband high steep drop filter in which a piezoelectric acoustic resonator and an LC passive circuit are embedded, characterized in that: It comprises a ladder-type filter network and an LC resonant network, wherein the ladder-type filter network and the LC resonant network are sequentially connected in series, or the ladder-type filter network and the LC resonant network are sequentially connected in series with an interval; The ladder filter network comprises a filter series trunk and a plurality of filter parallel branches, wherein the first end of the filter series trunk serves as an input end, and the two ends of the filter parallel branches are respectively connected to the ground wire and the series trunk; At least one series hybrid resonance unit is arranged on the filter series trunk line, and the series hybrid resonance unit is used to form a pole in the passband to expand the passband bandwidth; At least one acoustic resonator or parallel hybrid resonance unit is arranged on the filtering parallel branch.

2. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 1, characterized in that: The series hybrid resonance unit is composed of a capacitor and an inductor connected in series or an acoustic resonator and an inductor connected in series; The parallel hybrid resonance unit is used to generate a zero point outside the passband to achieve out-of-band suppression.

3. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 2, characterized in that: The parallel hybrid resonance unit is composed of a capacitor and an inductor connected in series to achieve out-of-band suppression at one end of the passband.

4. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 2, characterized in that: The parallel hybrid resonance unit is composed of an acoustic resonator and an inductor connected in series to achieve out-of-band suppression at both ends of the passband.

5. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 1, characterized in that: The LC resonant network comprises a resonant series trunk and a plurality of resonant parallel branches, wherein a first end of the resonant series trunk is connected to a second end of the filtering series trunk, the second end of the resonant series trunk serves as an output end, and two ends of the resonant parallel branches are respectively connected to a ground line and the resonant trunk; The resonant series trunk circuit is provided with a plurality of series capacitors; The resonant parallel branch is provided with a parallel hybrid resonance unit.

6. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 1, characterized in that: The plurality of filter parallel branches include a first filter parallel branch, a second filter parallel branch and a third filter parallel branch; The LC resonant network comprises a resonant series trunk circuit, a first resonant parallel branch circuit and a second resonant parallel branch circuit; The filter series trunk is provided with a first series hybrid resonance unit and a second series hybrid resonance unit; The first filtering parallel branch is provided with a first acoustic resonator and a second acoustic resonator connected in series; A third acoustic resonator is provided on the second filtering parallel branch; The third filtering parallel branch is provided with a fourth acoustic resonator and a fifth acoustic resonator connected in series; The resonant series trunk circuit is provided with a first capacitor, a second capacitor and a third capacitor; The first resonant parallel branch is provided with a first parallel hybrid resonant unit; The second resonant parallel branch is provided with a second parallel hybrid resonant unit; The first parallel hybrid resonance unit and the second parallel hybrid resonance unit are both composed of a capacitor and an inductor connected in series; The first end of the first acoustic resonator is connected to the first end and the input end of the first series hybrid resonance unit respectively, the second end of the first acoustic resonator is connected to the first end of the second acoustic resonator, and the second end of the second acoustic resonator is connected to the ground wire; The first end of the third acoustic resonator is connected to the second end of the first series hybrid resonator unit and the first end of the second series hybrid resonator unit respectively, and the second end of the third acoustic resonator is connected to the ground wire; The first end of the fourth acoustic resonator is connected to the second end of the second series hybrid resonance unit and the first end of the first capacitor respectively, the second end of the fourth acoustic resonator is connected to the first end of the fifth acoustic resonator, and the second end of the fifth acoustic resonator is connected to the ground wire; The first end of the first parallel hybrid resonance unit is connected to the second end of the first capacitor and the first end of the second capacitor respectively, and the second end of the first parallel hybrid resonance unit is connected to the ground line; The first end of the second parallel hybrid resonance unit is connected to the second end of the second capacitor and the first end of the third capacitor respectively, and the second end of the second parallel hybrid resonance unit is connected to the ground line; The second end of the third capacitor is connected to the output end.

7. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 6, characterized in that: The first, second, third, fourth and fifth acoustic resonators are all used to generate transmission zeros at 4.95-5.05 GHz to form an extremely fast transition band, and at the same time generate transmission poles at 5.15-5.3 GHz to reduce passband insertion loss; The first and second series hybrid resonant units are used to generate transmission poles at 6.1-6.5 GHz and 5.15-5.3 GHz respectively to widen the passband; The first parallel hybrid resonance unit is used to generate a transmission zero point at 4.05 GHz-4.25 GHz to achieve an out-of-band suppression effect; The second parallel hybrid resonance unit is used to generate a transmission zero point at 4.55 GHz-4.75 GHz to achieve an out-of-band suppression effect.

8. The broadband high steep drop filter in which the piezoelectric acoustic resonator and the LC passive circuit are embedded according to claim 1, characterized in that: The acoustic resonator comprises a bulk acoustic wave resonator.

9. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 1, characterized in that: The acoustic resonator embedded filter also includes: An impedance matching unit is located between the ladder-type filtering network and the LC resonant network.

10. The broadband high steep drop filter based on the embedded piezoelectric acoustic resonator and LC passive circuit according to claim 9, characterized in that: The impedance matching unit is a fourth capacitor.

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