A broadband high-steepness filter with a piezoelectric acoustic resonator embedded in an LC passive circuit

Abstract

The present invention discloses a broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit, which includes a ladder-type filtering network and an LC resonance network. The ladder-type filtering network and the LC resonance network are connected in series in sequence, or the ladder-type filtering network and the LC resonance network are connected in series at intervals in sequence. The ladder-type filtering network includes a filtering series main path and a plurality of filtering parallel branches. The first end of the filtering series main path serves as the input end, and both ends of the filtering parallel branches are respectively connected to the ground wire and the series main path. At least one series hybrid resonance unit is arranged on the filtering series main path, and the series hybrid resonance unit is used to form poles 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. This filter can achieve a relatively high bandwidth, a relatively high out-of-band rejection, and a relatively narrow transition band.

Description

Technical Field

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

[0002] As wireless communication evolves from 4G to 5G and 6G, the standards define more and more frequency bands. An obvious trend can be observed, that is, 5G, 6G and higher versions are adopting wider bandwidths. For example, the n77 band 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 applications with large bandwidths, such as 5G sub-6 GHz and millimeter wave bands. However, the low Q of the lumped elements themselves makes it difficult to meet the requirements of narrow transition bands due to the rapid increase in the number of communication frequency bands.

[0004] The patent application for invention with the publication number CN116865714A discloses a filter for the N79 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 band. The filter for the N79 band adopts the integrated technology of acoustic resonator and IPD filter circuit to achieve the target requirements. Both of them adopt semiconductor processing technology and can be processed and manufactured on the same wafer. Moreover, the circuit and structure of this filter can have the characteristics of large bandwidth and fast roll-off, and can simultaneously achieve low insertion loss in the N79 band and high suppression of WiFi 6E.

[0005] The utility model patent application with the 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. Both ends of the series branch and the first parallel branch are respectively connected to the input end and the output end; a first capacitor and a second capacitor are sequentially arranged on the series branch, a resonator is arranged on the first parallel branch, an inductor is arranged on the second parallel branch, and one end of the inductor is connected between the first capacitor and the second capacitor, and the other end is grounded. This utility model uses a single resonator with an external circuit to form a filter, and the area is greatly reduced compared with the filter composed of multiple resonators connected in series and parallel. Its size can be made within 1mm*1mm, greatly reducing the manufacturing cost, being highly integrated, and meeting the miniaturization requirements of radio frequency front-end module components; and it can achieve the requirements of large bandwidth and high suppression, especially the out-of-band zero position can be flexibly adjusted.

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

[0007] The present invention provides a broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit, which can achieve high bandwidth, high out-of-band rejection and narrow transition band.

[0008] A specific embodiment of the present invention provides a broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit, including a ladder-type filter network and an LC resonance network, where the ladder-type filter network and the LC resonance network are connected in series in sequence, or the ladder-type filter network and the LC resonance network are connected in series at intervals in sequence;

[0009] The ladder-type filter network includes a filter series trunk and a plurality of filter parallel branches. The first end of the filter series trunk is used as the input end, and both ends of the filter parallel branches are respectively connected to the ground wire and the series trunk;

[0010] At least one series hybrid resonance unit is arranged on the filter series trunk, and the series hybrid resonance unit is used to form poles in the passband to expand the passband bandwidth;

[0011] At least one acoustic resonator or parallel hybrid resonance unit is arranged on the filter parallel branch.

[0012] Preferably, the series hybrid resonance unit is composed of a capacitor and an inductor in series or composed of an acoustic resonator and an inductor in series;

[0013] The parallel hybrid resonance unit is used to generate zeros outside the passband to achieve out-of-band rejection.

[0014] Compared with the prior art, the present invention proposes to arrange a parallel hybrid resonance unit on the series trunk of the traditional ladder-type filter network. By adjusting the specific parameters of the parallel hybrid resonance unit, such as inductance value, capacitance value or the parameters of the acoustic resonator, the parallel hybrid resonance unit can generate transmission poles in the collapse area of the passband, thereby broadening the passband bandwidth. In particular, the present invention can broaden the passband bandwidth and avoid the deterioration of insertion loss by composing the parallel hybrid resonance unit of an acoustic resonator and an inductor in series.

[0015] Preferably, the parallel hybrid resonance unit is composed of a capacitor and an inductor in series to achieve out-of-band rejection at one end of the passband.

[0016] Preferably, the parallel hybrid resonance unit is composed of an acoustic resonator and an inductor in series to achieve out-of-band rejection at both ends of the passband.

[0017] 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, achieving efficient out-of-band suppression at both ends of the passband through a single parallel hybrid resonance unit and avoiding a complex circuit structure.

[0018] Preferably, the LC resonance network includes a resonance series trunk and a plurality of resonance parallel branches. The first end of the resonance series trunk is connected to the second end of the filtering series trunk, the second end of the resonance series trunk serves as the output end, and both ends of the resonance parallel branches are respectively connected to the ground wire and the resonance trunk;

[0019] A plurality of series capacitors are provided on the resonance series trunk;

[0020] A parallel hybrid resonance unit is provided on the resonance parallel branch.

[0021] The present invention realizes generating a zero point at a low frequency to achieve out-of-band suppression and a relatively fast transition band through the parallel hybrid resonance unit of the LC resonance network, and cooperates with the series capacitors on the resonance series trunk to achieve a relatively wide passband at a high frequency.

[0022] Preferably, the plurality of filtering parallel branches include a first filtering parallel branch, a second filtering parallel branch, and a third filtering parallel branch;

[0023] The LC resonance network includes a resonance series trunk, a first resonance parallel branch, and a second resonance parallel branch;

[0024] A first series hybrid resonance unit and a second series hybrid resonance unit are provided on the filtering series trunk;

[0025] A first acoustic resonator and a second acoustic resonator connected in series are provided on the first filtering parallel branch;

[0026] A third acoustic resonator is provided on the second filtering parallel branch;

[0027] A fourth acoustic resonator and a fifth acoustic resonator connected in series are provided on the third filtering parallel branch;

[0028] A first capacitor, a second capacitor, and a third capacitor are provided on the resonance series trunk;

[0029] A first parallel hybrid resonance unit is provided on the first resonance parallel branch;

[0030] A second parallel hybrid resonance unit is provided on the second resonance parallel branch;

[0031] Both the first parallel hybrid resonance unit and the second parallel hybrid resonance unit are composed of a capacitor and an inductor connected in series;

[0032] The first end of the first acoustic resonator is respectively connected to the first end and the input end of the first series hybrid resonator unit. 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;

[0033] The first end of the third acoustic resonator 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. The second end of the third acoustic resonator is connected to the ground wire;

[0034] The first end of the fourth acoustic resonator is respectively connected to the second end of the second series hybrid resonator unit and the first end of the first capacitor. 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;

[0035] The first end of the first parallel hybrid resonator unit is respectively connected to the second end of the first capacitor and the first end of the second capacitor. The second end of the first parallel hybrid resonator unit is connected to the ground wire;

[0036] The first end of the second parallel hybrid resonator unit is respectively connected to the second end of the second capacitor and the first end of the third capacitor. The second end of the second parallel hybrid resonator unit is connected to the ground wire;

[0037] The second end of the third capacitor is connected to the output end.

[0038] Further preferably, 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 the passband insertion loss;

[0039] The first and second series hybrid resonator units are respectively used to generate transmission poles at (6.1 - 6.5 GHz and 5.15 - 5.3 GHz to broaden the passband;

[0040] The first parallel hybrid resonator unit is used to generate a transmission zero at 4.05 GHz - 4.25 GHz to achieve an out-of-band rejection effect;

[0041] The second parallel hybrid resonator unit is used to generate a transmission zero at 4.55 GHz - 4.75 GHz to achieve an out-of-band rejection effect.

[0042] 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 bandwidth of the passband to reach a relatively wide range greater than 500 MHz, and multiple stepped transmission zeros are generated by the first, second, third, fourth, and fifth acoustic resonators, thereby forming a narrow and rapidly decreasing transition band, and the passband insertion loss is reduced by the generated transmission poles.

[0043] Preferably, the acoustic resonator includes a bulk acoustic wave resonator.

[0044] Preferably, the acoustic resonator embedded filter further includes an impedance matching unit located between the stepped filter network and the LC resonance network.

[0045] More preferably, the impedance matching unit is a fourth capacitor.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] By arranging at least one series hybrid resonance unit on the filtering series main path of the stepped filter network, the present invention enables one or more transmission poles to be formed on the passband, thereby realizing the support for the passband, and further broadening the passband to meet the requirements of 5G, 6G and higher versions for high passband bandwidth. By arranging acoustic resonators on the filtering parallel branches, the present invention utilizes the acoustic resonators to generate zeros in the transition band to achieve a narrower transition band. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of a stepped filter network composed of acoustic resonators provided by a specific embodiment of the present invention;

[0049] Figure 2 Schematic diagram of a traditional LC resonance network provided by a specific embodiment of the present invention;

[0050] Figure 3 Schematic diagram of a broadband high-steepness filter based on the embedding of piezoelectric acoustic resonators and LC passive circuits provided by a specific embodiment of the present invention;

[0051] Figure 4 Schematic diagram of the S-parameter curve of a broadband high-steepness filter based on the embedding of piezoelectric acoustic resonators and LC passive circuits provided by a specific embodiment of the present invention;

[0052] Figure 5 Schematic diagram of another broadband high-steepness filter based on the embedding of piezoelectric acoustic resonators and LC passive circuits provided by a specific embodiment of the present invention;

[0053] Figure 6Schematic diagram of S-parameters of another broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit provided by a specific embodiment of the present invention. Detailed implementation manners

[0054] The following is a detailed description in combination with specific implementation examples. The following examples are only related parts of the present invention. These examples will help relevant personnel understand the principle of the present invention and do not impose any limitations on the present invention. It should be noted that, based on the concept of the present invention, corresponding structural adjustments and changes can be made, and all such belong to the protection scope of the present invention.

[0055] In order to achieve a large passband, a narrow transition band, and the required out-of-band rejection, the present invention embeds a series hybrid resonance unit in a ladder-type filter network composed of acoustic resonators to broaden the passband, and embeds a parallel hybrid resonance unit on the basis of a traditional LC resonance network to achieve out-of-band rejection.

[0056] As Figure 1 shown, a specific embodiment of the present invention provides a ladder-type filter network composed of acoustic resonators. This network is composed of two series resonators AS and a parallel resonator AP. One end of the parallel resonator is connected in the middle of two adjacent series resonators, and one end includes but is not limited to being grounded. Through the transmission zeros and transmission poles generated by the acoustic resonators, a band-pass filtering effect with a very deep and steep skirt pole can be obtained.

[0057] As Figure 2 shown, a traditional LC resonance network is composed of a series branch (several series capacitors C S ), and several parallel branches (C P and L P ). By increasing the order and optimizing the parameter values of each component, high-pass, band-pass, and low-pass filters with good insertion loss effects and zeros at different positions can be obtained.

[0058] The broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit provided by 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 are connected in series in sequence, or the ladder-type filter network and the LC resonance network are connected in series at intervals in sequence.

[0059] The ladder-type filter network provided by a specific embodiment of the present invention is obtained by replacing some acoustic resonators with series hybrid resonance units or parallel hybrid resonance units in a ladder-type filter network composed of acoustic resonators.

[0060] The LC resonance network provided by a specific embodiment of the present invention is to make part of the parallel branches of the traditional LC resonance network (C P and L P) It is obtained by replacing it with a parallel hybrid resonant unit.

[0061] The series hybrid resonant unit provided by the specific embodiment of the present invention is composed of a capacitor and an inductor in series or composed of an acoustic resonator and an inductor in series, and is used to generate a transmission pole at the collapse of the passband to support the passband so as to widen the passband.

[0062] The parallel hybrid resonant unit provided by the specific embodiment of the present invention is composed of a capacitor and an inductor in series to achieve out-of-band suppression at one end of the passband.

[0063] In a specific embodiment, as Figure 3 shown, the broadband high-steepness filter based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit provided by the specific embodiment of the present invention includes a ladder-type filter network and an LC resonant network. The ladder-type filter network includes a filter series main path, a first filter parallel branch, a second filter parallel branch, and a third filter parallel branch.

[0064] The first series hybrid resonant unit and the second series hybrid resonant unit are arranged on the filter series main path provided by the specific embodiment of the present invention. The first acoustic resonator Res1 and the second acoustic resonator Res2 in series are arranged on the first filter parallel branch provided by the specific embodiment of the present invention. The third acoustic resonator Res3 is arranged on the second filter parallel branch. The fourth acoustic resonator Res4 and the fifth acoustic resonator Res5 in series are arranged on the third filter parallel branch.

[0065] The LC resonant network provided by the specific embodiment of the present invention includes a resonant series main path, a first resonant parallel branch, and a second resonant parallel branch. The first capacitor C1, the second capacitor C2, and the third capacitor C3 are arranged on the resonant series main path. The first parallel hybrid resonant unit is arranged on the first resonant parallel branch. The second parallel hybrid resonant unit is arranged on the second resonant parallel branch. Both the first parallel hybrid resonant unit and the second parallel hybrid resonant unit are composed of a capacitor and an inductor in series.

[0066] The first end of the first acoustic resonator Res1 provided by the specific embodiment of the present invention is respectively connected to the first end of the first series hybrid resonant unit and the input end. The second end of the first acoustic resonator Res1 is connected to the first end of the second acoustic resonator Res2. The second end of the second acoustic resonator Res2 is connected to the ground wire.

[0067] The first end of the third acoustic resonator Res3 provided by the specific embodiment of the present invention is respectively connected to the second end of the first series hybrid resonant unit and the first end of the second series hybrid resonator unit. The second end of the third acoustic resonator Res3 is connected to the ground wire.

[0068] In a specific embodiment of the present invention, the first end of the fourth acoustic resonator Res4 is connected to the second end of the second series hybrid resonator and the first end of the first capacitor respectively. 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.

[0069] In a specific embodiment of the present invention, the first end of the first parallel hybrid resonator is connected to the second end of the first capacitor C1 and the first end of the second capacitor C2 respectively. The second end of the first parallel hybrid resonator is connected to the ground wire. The first end of the second parallel hybrid resonator is connected to the second end of the second capacitor C2 and the first end of the third capacitor C3 respectively. The second end of the second parallel hybrid resonator is connected to the ground wire. The second end of the third capacitor C3 is connected to the output terminal.

[0070] As Figure 4 shown, the series resonance frequencies f of the first, second, third, fourth, and fifth acoustic resonators provided in a specific embodiment of the present invention s are located at the vertical line 4 (4.98 GHz). The deep transmission zero formed by f s and the characteristic of the high Q value of the bulk acoustic resonator make Figure 4 the curve of P have an extremely fast transition band. Its parallel resonance frequency f

[0071] In a specific embodiment of the present invention, both the first series hybrid resonator and the second series hybrid resonator are composed of a series-connected acoustic resonator and an inductor. By adjusting the parameters of the first series hybrid resonator, a transmission pole is generated at 6.15 GHz (circle 6) to broaden the passband, and at the same time, a transmission zero is provided at 4.1 GHz (vertical line 1) to contribute to the out-of-band rejection of the left far end.

[0072] In a specific embodiment of the present invention, by adjusting the parameters of the second series hybrid resonator, a transmission pole is generated at 5.2 GHz (circle 5) to broaden the passband, and at the same time, a transmission zero is provided at 4.4 GHz (the frequency corresponding to the vertical line 2) to contribute to the out-of-band rejection of the left far end.

[0073] 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 together with the first parallel hybrid resonance unit and the second parallel hybrid resonance unit, achieving deeper out-of-band suppression further to the left, and simultaneously performing impedance co-optimization with the network at the left end to obtain lower in-band insertion loss. Among them, the first parallel hybrid resonance unit provided in the specific embodiment of the present invention generates a transmission zero (the frequency corresponding to vertical line 1) at 4.05 GHz - 4.25 GHz to achieve the 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 (the frequency corresponding to vertical line 3) at 4.55 GHz - 4.75 GHz to achieve the out-of-band suppression effect.

[0074] As Figure 4 shown, the target of this circuit is that the passband is at 5.15 GHz - 7.12 GHz, with a rapid steep drop on the left side, and the out-of-band suppression can reach below -20 dB. It can be seen from the figure that this circuit can obtain a steep drop of about 400 M on the left side and obtain the first zero point, which is provided by a high-Q acoustic resonator and generates an out-of-band suppression effect near the proximal end of the passband; the far-end zero point below 4.5 GHz is realized by LC elements and a hybrid resonance unit; at the same time, the additional transmission poles formed by the hybrid resonance unit maintain an ultra-wide bandwidth of 1970 MHz, and the lowest insertion loss in the passband is -1.35 dB, and the in-band insertion loss is within -2.8 dB.

[0075] In a specific embodiment, as Figure 5 shown, the broadband high-steep-drop filter provided in the specific embodiment of the present invention, which is based on the embedding of a piezoelectric acoustic resonator and an LC passive circuit, 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 at intervals in sequence, 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 trunk, a fourth filter parallel branch, and a fifth filter parallel branch.

[0076] A third series hybrid resonance unit is provided on the filter series trunk provided in the specific embodiment of the present invention, and the third series hybrid resonance unit is constructed by connecting an acoustic resonator and an inductor in series. A third parallel hybrid resonance unit is provided on the fourth filter parallel branch provided in the specific embodiment of the present invention, and a sixth acoustic resonator Res6 is provided on the fifth filter parallel branch.

[0077] The LC resonant network provided by the specific embodiment of the present invention includes a resonant series trunk, a third resonant parallel branch, a fourth resonant parallel branch, and a fifth resonant parallel branch. A fifth capacitor C5 and a sixth capacitor C6 are arranged on the resonant series trunk. A fourth parallel hybrid resonant unit is arranged on the third resonant parallel branch. A fifth parallel hybrid resonant unit is arranged on the fourth resonant parallel branch. A sixth parallel hybrid resonant unit is arranged on the fifth resonant parallel branch. The fourth parallel hybrid resonant unit is constructed by a series-connected acoustic resonator and an inductor. The fifth parallel hybrid resonant unit and the sixth parallel hybrid resonant unit are both composed of a series-connected capacitor and an inductor.

[0078] Figure 5 The shown acoustic resonant network 1 for a broadband high-steepness filter and the LC resonant network 2 based on the embedding of piezoelectric acoustic resonators and LC passive circuits form a basic ladder-type filter network. Through the substitution and embedding of hybrid resonant units, the effects of large bandwidth, fast transition, and high out-of-band rejection are achieved. The left acoustic resonator has a high Q value, providing extremely deep zeros and an extremely narrow transition skirt. The hybrid resonant unit ensures that there is no collapse in the passband. The right LC network provides high-pass filtering performance to provide more distal zeros and ensure out-of-band rejection.

[0079] As Figure 6 shown, the third series hybrid resonant unit provided by the specific embodiment of the present invention generates a transmission pole at 5.48 GHz (at the position of circle 5) to broaden the passband and reduce the insertion loss, and jointly forms a large passband of the filter with the sixth acoustic resonator Res6.

[0080] The fifth capacitor C5 and the sixth capacitor C6 arranged on the resonant series trunk provided by the specific embodiment of the present invention, together with the fourth parallel hybrid resonant unit, the fifth parallel hybrid resonant unit, and the sixth parallel hybrid resonant unit, constitute a high-pass filter and form good out-of-band rejection at low frequencies.

[0081] Among them, the fourth parallel hybrid resonant unit provided by the specific embodiment of the present invention generates a transmission zero (at the frequency corresponding to vertical line 6) at the right proximal end of the passband, thereby forming a good suppression effect; the fifth parallel hybrid resonant unit and the sixth parallel hybrid resonant unit provided by the specific embodiment of the present invention generate transmission zeros (at the frequencies corresponding to vertical lines 1 and 2) at 3.25 GHz and 4.5 GHz on the left side of the passband, thereby forming a good suppression effect on the left side of the filter and achieving the target performance.

[0082] The sixth acoustic resonator Res6 provided by the specific embodiment of the present invention generates a transmission zero at 4.94 GHz (the frequency corresponding to vertical line 4) to form a faster transition band.

[0083] The third parallel hybrid resonance unit provided by the specific embodiment of the present invention generates a transmission zero at 4.85 GHz (the frequency corresponding to vertical line 3), which has a good suppression effect on the left proximal out-of-band of the filter, and simultaneously generates a transmission zero at the frequency corresponding to vertical line 7 (8.25 GHz), which has a good suppression effect on the right distal end of the filter.

[0084] Figure 6 The shown circuit is the S-parameter simulation curve of the large broadband hybrid filter. Wherein the abscissa is the frequency, the unit is GHz, and the ordinate is the insertion loss, the unit is dB. The target passband frequency of this circuit is 5.15 - 6 GHz, the passband is an ultra-wide bandwidth of 850 MHz, and it has a rapid steep drop on the left. It can be found from the curve that this hybrid filter circuit realizes a steep drop characteristic of 350 MHz, and at the same time the in-band insertion loss is above -2.9 dB, and the minimum value of the in-band insertion loss is -1.5 dB.

[0085] By organically coordinating the acoustic resonator and the LC resonator in the specific embodiment of the present invention, the defect of the low Q value of the lumped element is skillfully avoided by using the high Q value of the acoustic resonator, and the deficiency of the low electromechanical coupling coefficient of the acoustic resonator is resolved by using the characteristics of the large bandwidth of the LC filter and the ability of the LC element to generate additional transmission zeros (poles) with the acoustic resonator. Thus, a hybrid filter with an ultra-wide bandwidth and capable of realizing a rapid steep drop is designed, and the bandwidth can be flexibly adjusted by adjusting parameters such as LC element parameters and the effective area of the acoustic resonator. This provides a good solution to the challenges brought by the development of 4G, 5G, and 6G communication technologies, such as the ultra-wide bandwidth WIFI 6E frequency band.

[0086] Compared with traditional LC filters and acoustic filters, the present invention has more excellent performance:

[0087] (1) By cascading the acoustic resonance network 1 and the LC resonance network 2 in the present invention, a filtering performance with a large bandwidth and a high steep drop can be obtained.

[0088] (2) By taking the resonator and the inductor as parallel branches in the present invention, additional zeros can be obtained, and the out-of-band performance of the filter can be optimized; in addition, by replacing the resonator with a capacitor and optimizing the capacitor parameters, the out-of-band performance at a farther distance can be optimized.

[0089] (3) The present invention can improve the passband performance and out-of-band suppression by changing the number of the acoustic resonance network and the LC resonance network.

[0090] (4) The present invention can easily obtain deep out-of-band suppression at different frequencies and a filter with more excellent performance by adjusting the parameter values of the lumped elements.

[0091] (5) By replacing the capacitance and inductance in the resonant unit with acoustic resonators, the present invention can obtain a resonant unit with a higher Q value and achieve a rapid steep drop.

[0092] (6) The present invention can obtain different target performances by replacing different capacitance and inductance elements in the LC basic circuit with acoustic resonators and hybrid resonant units.

[0093] (7) The present invention can flexibly adjust the bandwidth filtering network by adjusting the number of hybrid resonant units, the parameters of the LC elements in the hybrid resonant unit, the effective area of the acoustic resonator, etc.

Claims

1. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that It includes a ladder-type filter network and an LC resonance network, where the ladder-type filter network and the LC resonance network are connected in series in sequence, or the ladder-type filter network and the LC resonance network are connected in series at intervals in sequence; The ladder-type filter network includes a filter series trunk and multiple filter parallel branches. The first end of the filter series trunk serves as the input end, and both 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, and the series hybrid resonance unit is used to form poles in the passband to expand the passband bandwidth and contribute to out-of-band suppression at the far left end; First, second, third, fourth, and fifth acoustic resonators are arranged on the filter parallel branches. 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 the passband insertion loss; the series hybrid resonance unit is composed of an acoustic resonator and an inductor connected in series; The multiple filter parallel branches include a first filter parallel branch, a second filter parallel branch, and a third filter parallel branch; A first acoustic resonator and a second acoustic resonator connected in series are arranged on the first filter parallel branch; A third acoustic resonator is arranged on the second filter parallel branch; A fourth acoustic resonator and a fifth acoustic resonator connected in series are arranged on the third filter parallel branch.

2. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that A parallel hybrid resonance unit can also be arranged on the filter parallel branch, and the parallel hybrid resonance unit is used to generate zeros outside the passband to achieve out-of-band suppression.

3. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, 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. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, 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. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that, The LC resonance network includes a resonance series trunk and multiple resonance parallel branches. The first end of the resonance series trunk is connected to the second end of the filter series trunk, the second end of the resonance series trunk serves as the output end, and both ends of the resonance parallel branches are respectively connected to the ground wire and the resonance trunk; Multiple series capacitors are arranged on the resonance series trunk; A first parallel hybrid resonance unit and a second parallel hybrid resonance unit are arranged on the resonance parallel branch.

6. The broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit according to claim 2, characterized in that ； The LC resonance network includes a resonance series trunk, a first resonance parallel branch, and a second resonance parallel branch; A first series hybrid resonance unit and a second series hybrid resonance unit are arranged on the filter series trunk; A first capacitor, a second capacitor, and a third capacitor are arranged on the resonance series trunk; A first parallel hybrid resonance unit is arranged on the first resonance parallel branch; A second parallel hybrid resonance unit is arranged on the second resonance parallel branch; Both the first parallel hybrid resonance unit and the second parallel hybrid resonance unit are composed of a capacitor and an inductor connected in series; The first end of the first acoustic resonator is respectively connected to the first end of the first series hybrid resonance unit and the input end. 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 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 is connected to the ground wire; The first end of the fourth acoustic resonator is respectively connected to the second end of the second series hybrid resonator unit and the first end of the first capacitor, 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 resonator unit is respectively connected to the second end of the first capacitor and the first end of the second capacitor, and the second end of the first parallel hybrid resonator unit is connected to the ground wire; The first end of the second parallel hybrid resonator unit is respectively connected to the second end of the second capacitor and the first end of the third capacitor, and the second end of the second parallel hybrid resonator unit is connected to the ground wire; The second end of the third capacitor is connected to the output terminal.

7. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that, The first and second series hybrid resonator units are respectively used to generate transmission poles at 6.1 - 6.5 GHz and 5.15 - 5.3 GHz to broaden the passband; The first parallel hybrid resonator unit is used to generate a transmission zero at 4.05 GHz - 4.25 GHz to achieve an out-of-band rejection effect; The second parallel hybrid resonator unit is used to generate a transmission zero at 4.55 GHz - 4.75 GHz to achieve an out-of-band rejection effect.

8. The broadband high-steepness filter with a piezoelectric acoustic resonator embedded in an LC passive circuit according to claim 1, characterized in that The acoustic resonator includes a bulk acoustic wave resonator.

9. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that, Further included is: An impedance matching unit located between the ladder-type filter network and the LC resonator network.

10. A broadband high-steepness filter in which a piezoelectric acoustic resonator is embedded with an LC passive circuit, characterized in that, The impedance matching unit is a fourth capacitor.

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