Filter and radio frequency front-end module
Through the design of connecting longitudinally coupled surface acoustic wave resonators in parallel and grounded separately, the problem of insufficient isolation of the RF front-end module filter is solved, and higher isolation and performance improvement is achieved.
Patent Information
- Application Number
- CN202420010714.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-02
- Publication Date
- 2025-01-14
- Estimated Expiration
- 2034-01-02
AI Technical Summary
The isolation of existing RF front-end module filters is insufficient, especially between transmission and reception, and it is difficult to meet the need to improve isolation.
A filter is designed to improve the isolation of the filter by connecting a plurality of longitudinally coupled surface acoustic wave resonators in parallel and grounding the ground terminals of these coupled surface acoustic wave resonators separately on a piezoelectric substrate.
Through the separate grounding design, the transmission zero point of the filter is moved to the low frequency, which significantly improves the isolation from RX to TX and enhances the isolation performance of the filter.
Smart Images
Figure CN222356342U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of radio frequency filtering technology, and in particular to a filter and a radio frequency front-end module. Background Art
[0002] The RF front-end module is located between the antenna and the RF transceiver, and is the core component of electronic terminal communications. Among them, the filter is one of the essential key components in the RF front-end module, which is mainly used for frequency selection - allowing the required frequency signal to pass through and reflecting the unnecessary interference frequency signal. The longitudinally coupled surface acoustic wave resonator is widely used in the receiving end filter because of its small size and good out-of-band suppression, but its power capacity is not high.
[0003] With the development of communication technology, higher requirements are placed on the performance of RF front-end filters, especially the isolation between transmit and receive (between TX and RX). Therefore, how to improve the isolation of filters such as receive filters has become a problem that needs to be solved urgently.
[0004] Application Contents
[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a filter and a radio frequency front-end module, which are intended to improve the isolation of the filter.
[0006] In order to solve the above technical problems, an embodiment of the present application provides a filter, which includes:
[0007] Input terminals and output terminals;
[0008] at least two longitudinally coupled surface acoustic wave resonators connected in parallel between the input terminal and the output terminal, the at least two longitudinally coupled surface acoustic wave resonators being formed on the same piezoelectric substrate, each of the longitudinally coupled surface acoustic wave resonators comprising at least two interdigital transducers;
[0009] at least two ground terminals, the at least two ground terminals comprising a first ground terminal and a second ground terminal isolated from each other on the piezoelectric substrate;
[0010] The at least two longitudinally coupled surface acoustic wave resonators include a first longitudinally coupled surface acoustic wave resonator and a second longitudinally coupled surface acoustic wave resonator, the ground end of the first longitudinally coupled surface acoustic wave resonator is connected to the first ground terminal, and the ground end of the second longitudinally coupled surface acoustic wave resonator is connected to the second ground terminal.
[0011] In some embodiments, the filter is a receiving filter, the input terminal is an antenna terminal, and the output terminal is a receiving terminal.
[0012] In some embodiments, the filter further comprises a first filtering module, wherein the first filtering module is connected between the input terminal and the longitudinally coupled surface acoustic wave resonator, or the first filtering module is connected between the longitudinally coupled surface acoustic wave resonator and the output terminal.
[0013] In some embodiments, the first filtering module includes at least one series arm resonator, and the at least one series arm resonator is connected in series between the input terminal and the output terminal; or,
[0014] The first filtering module comprises at least one parallel arm resonator, one end of the at least one parallel arm resonator is connected between the input terminal and the output terminal, and the other end is grounded; or,
[0015] The first filtering module includes at least one single-order resonance unit, each single-order resonance unit includes a series arm resonator and a parallel arm resonator, the series arm resonator is connected between the input terminal and the output terminal, one end of the parallel arm resonator is connected between the input terminal and the output terminal, and the other end of the parallel arm resonator is grounded.
[0016] In some embodiments, the first filtering module includes two series arm resonators and two parallel arm resonators, and the two series arm resonators are connected in series between the input terminal and the longitudinally coupled surface acoustic wave resonator;
[0017] Among the two parallel arm resonators, one end of one of the parallel arm resonators is connected between the two series arm resonators, and the other end is grounded; one end of the other parallel arm resonator is connected between the series arm resonator and the longitudinally coupled surface acoustic wave resonator, and the other end is grounded.
[0018] In some embodiments, among the two parallel arm resonators, the ground end of one of the parallel arm resonators is connected to the first ground terminal, the ground end of the other parallel arm resonator is connected to the second ground terminal, or the ground ends of both parallel arm resonators are connected to the first ground terminal or the second ground terminal; or,
[0019] The filter further includes a third grounding terminal disposed on the piezoelectric substrate, the third grounding terminal is connected to the first grounding terminal or the second grounding terminal on the piezoelectric substrate, and the grounding ends of the two parallel arm resonators are both connected to the third grounding terminal.
[0020] In some embodiments, the filter further includes a first filtering module and a second filtering module, wherein the first filtering module is connected between the input terminal and the longitudinally coupled surface acoustic wave resonator, and the second filtering module is connected between the longitudinally coupled surface acoustic wave resonator and the output terminal.
[0021] In some embodiments, the first filtering module includes a series arm resonator and a parallel arm resonator, and the second filtering module includes a series arm resonator and a parallel arm resonator.
[0022] The series arm resonator of the first filter module is connected in series between the input terminal and the longitudinally coupled surface acoustic wave resonator, one end of the parallel arm resonator of the first filter module is connected between the series arm resonator of the first filter module and the longitudinally coupled surface acoustic wave resonator, and the other end is connected to the first ground terminal or the second ground terminal;
[0023] The series arm resonator of the second filter module is connected in series between the longitudinally coupled surface acoustic wave resonator and the output terminal, one end of the parallel arm resonator of the second filter module is connected between the series arm resonator of the second filter module and the output terminal, and the other end is connected to the first ground terminal or the second ground terminal.
[0024] In some embodiments, the piezoelectric substrate includes a substrate and a piezoelectric layer, the piezoelectric layer is disposed on the substrate, and the longitudinally coupled surface acoustic wave resonator is formed on the piezoelectric layer;
[0025] The temperature coefficient of the substrate is smaller than the temperature coefficient of the piezoelectric layer, and / or the thickness of the substrate is larger than the thickness of the piezoelectric layer.
[0026] In some embodiments, the piezoelectric substrate further comprises an intermediate layer, wherein the intermediate layer is disposed between the piezoelectric layer and the substrate;
[0027] The intermediate layer includes at least one low acoustic velocity layer or a low acoustic impedance layer, and the acoustic velocity of the intermediate layer is lower than the acoustic velocity of the piezoelectric layer.
[0028] In some embodiments, the filter further comprises a temperature compensation layer, wherein the temperature compensation layer is disposed on the piezoelectric substrate and at least covers the resonance region of the longitudinally coupled surface acoustic wave resonator; and / or,
[0029] The filter further comprises a passivation layer, which is arranged on the piezoelectric substrate and at least covers the longitudinally coupled surface acoustic wave resonator.
[0030] An embodiment of the present application also provides a radio frequency front-end module, comprising the above-mentioned filter.
[0031] The filter provided in this application has the following beneficial effects:
[0032] In this embodiment, among multiple ground terminals and multiple longitudinally coupled surface acoustic wave resonators connected in parallel, the ground end of the first longitudinally coupled surface acoustic wave resonator is connected to the first ground terminal, and the ground end of the second longitudinally coupled surface acoustic wave resonator is connected to the second ground terminal. The first ground terminal and the second ground terminal are isolated from each other on the piezoelectric substrate, which means that the first ground terminal is not connected to the second ground terminal on the piezoelectric substrate, so that the ground end of the first longitudinally coupled surface acoustic wave resonator and the ground end of the second longitudinally coupled surface acoustic wave resonator can be grounded separately on the piezoelectric substrate. Compared with connecting the ground ends of multiple longitudinally coupled surface acoustic wave resonators connected in parallel to the same ground terminal, the transmission zero point of the filter can be moved to a low frequency, thereby improving the isolation of the filter from RX to TX. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.
[0034] Figure 1 This is the first topological diagram of the filter provided in the embodiment of the present application;
[0035] Figure 2 This is the second topology diagram of the filter provided in the embodiment of the present application;
[0036] Figure 3 This is the third topological diagram of the filter provided in the embodiment of the present application;
[0037] Figure 4 This is the fourth topology diagram of the filter provided in the embodiment of the present application;
[0038] Figure 5 This is the fifth topology diagram of the filter provided in the embodiment of the present application;
[0039] Figure 6 This is a first circuit diagram of a first filter module and a second filter module in a filter provided in an embodiment of the present application;
[0040] Figure 7 This is a second circuit diagram of the first filtering module and the second filtering module in the filter provided in an embodiment of the present application;
[0041] Figure 8 This is a third circuit diagram of the first filter module and the second filter module in the filter provided in the embodiment of the present application;
[0042] Fig. 9 This is a first circuit diagram of the filter provided in the embodiment of the present application;
[0043] Fig.10 is a second circuit diagram of the filter provided in the embodiment of the present application;
[0044] Fig.11 is a topological diagram of the radio frequency front-end module provided in an embodiment of the present application;
[0045] Fig.12 This is a first circuit diagram of the RF front-end module provided in an embodiment of the present application;
[0046] Fig.13 This is a second circuit diagram of the RF front-end module provided in an embodiment of the present application;
[0047] Fig.14 is a topological diagram of a comparative example provided in an embodiment of the present application;
[0048] Fig.15 It is a comparison chart of the isolation between Example 1 and the comparative example provided in the embodiments of the present application.
[0049] Description of Figure Numbers:
[0050] 1. Filter; 2. RF front-end module;
[0051] 10. Input terminal; 20. Output terminal; 30. Ground terminal; 30a. First ground terminal; 30b. Second ground terminal; 40. Longitudinal coupled surface acoustic wave resonator; 40a. First longitudinal coupled surface acoustic wave resonator; 40b. Second longitudinal coupled surface acoustic wave resonator; 41. Interdigital transducer; ANT. Antenna terminal; RX. Receiving terminal; S. Series arm resonator; P. Parallel arm resonator. DETAILED DESCRIPTION
[0052] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0053] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.
[0054] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.
[0055] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.
[0056] In the related art, higher requirements are placed on the performance of the filter of the RF front-end module, especially the transmit-receive isolation. Therefore, how to improve the isolation of the filter has become a problem that needs to be solved urgently.
[0057] So, if Figure 1 As shown, an embodiment of the present application provides a filter 1, which respectively connects a first ground terminal 30a and a second ground terminal 30b by arranging a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b connected in parallel, and the first ground terminal 30a is not connected to the second ground terminal 30b on the piezoelectric substrate, thereby improving the isolation of the filter 1RX to TX.
[0058] The following is combined with Figures 1 to 13 , some embodiments of the present application are described in detail. In the absence of conflict, the following embodiments and features of the embodiments can be combined with each other.
[0059] It should be noted that in the accompanying drawings, Figures 1 to 13 For illustrative purposes only, Figures 1 to 5 Each exemplary shows a topological diagram of the filter 1 of this embodiment, Figures 6 to 8 Each exemplarily shows a circuit diagram of the first filtering module and the second filtering module in this embodiment, Fig. 9 and Fig.10 Each exemplarily shows a circuit diagram of the filter 1 of this embodiment, Fig.11 A topology diagram of the RF front-end module 2 of this embodiment is exemplarily shown. Fig.12 and Fig.13Each exemplarily shows a circuit diagram of the RF front-end module 2 of this embodiment. The above drawings do not limit the structure of the filter 1 and the RF front-end module 2 of this embodiment, and the drawings can be combined with each other without conflict.
[0060] like Figure 1 As shown, the filter 1 of the embodiment of the application includes an input terminal 10, an output terminal 20, at least two grounding terminals 30, and at least two longitudinally coupled surface acoustic wave resonators 40 connected in parallel between the input terminal 10 and the output terminal 20, the at least two longitudinally coupled surface acoustic wave resonators 40 are formed on the same piezoelectric substrate, and each longitudinally coupled surface acoustic wave resonator 40 includes at least two interdigital transducers 41; the at least two grounding terminals 30 include a first grounding terminal 30a and a second grounding terminal 30b isolated from each other on the piezoelectric substrate; wherein the at least two longitudinally coupled surface acoustic wave resonators 40 include a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b, the grounding end of the first longitudinally coupled surface acoustic wave resonator 40a is connected to the first grounding terminal 30a, and the grounding end of the second longitudinally coupled surface acoustic wave resonator 40b is connected to the second grounding terminal 30b.
[0061] In this embodiment, among the multiple grounding terminals 30 and the multiple longitudinally coupled surface acoustic wave resonators 40 connected in parallel, the grounding end of the first longitudinally coupled surface acoustic wave resonator 40a is connected to the first grounding terminal 30a, and the grounding end of the second longitudinally coupled surface acoustic wave resonator 40b is connected to the second grounding terminal 30b. The first grounding terminal 30a and the second grounding terminal 30b are isolated from each other on the piezoelectric substrate, which means that the first grounding terminal 30a is not connected to the second grounding terminal 30b on the piezoelectric substrate, so that the grounding end of the first longitudinally coupled surface acoustic wave resonator 40a and the grounding end of the second longitudinally coupled surface acoustic wave resonator 40b can be grounded separately on the piezoelectric substrate. Compared with connecting the grounding ends of the multiple longitudinally coupled surface acoustic wave resonators 40 connected in parallel to the same grounding terminal 30, the transmission zero point of the filter 1 can be moved to a low frequency, thereby improving the isolation from RX to TX of the filter 1.
[0062] Among them, the number of interdigital transducers 41 included in each longitudinally coupled surface acoustic wave resonator 40 can be two, three, four or five, etc., and the number of interdigital transducers 41 in the longitudinally coupled surface acoustic wave resonator 40 is not specifically limited. The structural parameters (such as the number of interdigital transducers 41, the resonant frequency, aperture, duty cycle, etc. of the interdigital transducers 41) of the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b can be the same or different, and this embodiment does not specifically limit it. Preferably, the structural parameters of the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b are the same, the structure is simple, and it is easier to implement. The first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b can share a reflection grating or not share a reflection grating. Preferably, they share a reflection grating, which can reduce the size of the filter 1.
[0063] like Figure 1 and Figure 2 As shown, it can be understood that in each longitudinally coupled surface acoustic wave resonator 40, the signal end of the same interdigital transducer 41 is used for inputting signals or outputting signals, and the ground end is used for grounding. In the same longitudinally coupled resonator 40, the ground ends of the interdigital transducers 41 are connected to each other, the signal ends used for inputting signals are connected to each other, and the signal ends used for outputting signals are connected to each other. Exemplarily, in two longitudinally coupled surface acoustic wave resonators 40 (a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b), each longitudinally coupled surface acoustic wave resonator 40 includes an embodiment of three interdigital transducers 41, each longitudinally coupled surface acoustic wave resonator 40 has an input side and an output side, and two ground ends and a signal end located between the two ground ends can be provided on the input side, and two signal ends and a ground end located between the two signal ends can be provided on the output side; or two signal ends and a ground end located between the two signal ends can be provided on the input side, and two ground ends and a signal end located between the two ground ends can be provided on the output side. Specifically, between the input terminal 10 and the output terminal 20, the signal connection mode of the longitudinally coupled surface acoustic wave resonator 40 can be: Figure 1 As shown, it can also be Figure 2 No matter which signal connection method is adopted by the longitudinally coupled surface acoustic wave resonator 40 , the signal input end of the longitudinally coupled surface acoustic wave resonator 40 is connected to the input terminal 10 , and the signal output end of the longitudinally coupled surface acoustic wave resonator 40 is connected to the output terminal 20 .
[0064] In some embodiments, among the multiple longitudinally coupled surface acoustic wave resonators 40 connected in parallel, on the one hand, only the ground ends of two longitudinally coupled surface acoustic wave resonators 40 may be connected to two different ground terminals 30 respectively, and the two ground terminals 30 are not connected on the piezoelectric substrate, and the ground ends of the other longitudinally coupled surface acoustic wave resonators 40 may be connected to a ground terminal 30 different from the two ground terminals 30, or the ground ends of the other longitudinally coupled surface acoustic wave resonators 40 are all connected to one of the two ground terminals 30, and the ground ends of some of the other longitudinally coupled surface acoustic wave resonators 40 may be connected to one of the ground terminals 30, and the ground ends of the other longitudinally coupled surface acoustic wave resonators 40 may be connected to the other ground terminal 30; on the other hand, each longitudinally coupled surface acoustic wave resonator 40 is connected to a different ground terminal 30, which can improve the isolation of the filter 1. In one embodiment, multiple (for example, 3, 4, 5, etc.) longitudinally coupled surface acoustic wave resonators 40 connected in parallel are respectively connected to multiple ground terminals 30 one by one, and the multiple ground terminals 30 are respectively grounded. The multiple ground terminals 30 are not connected on the piezoelectric substrate, which can improve the isolation of the filter 1RX to TX.
[0065] like Figure 1 and Figure 2 As shown, in some embodiments, the filter 1 is a receiving filter, the input terminal 10 is an antenna terminal ANT, and the output terminal 20 is a receiving terminal RX. In this embodiment, the input terminal 10 can be used to connect the antenna, so that the signal can be transmitted from the input terminal 10, and then pass through the plurality of longitudinally coupled surface acoustic wave resonators 40 connected in parallel, and finally reach the receiving terminal RX to complete the signal reception.
[0066] like Figure 1 , Figure 3 and Figure 4 As shown, in some embodiments, the filter 1 further includes a first filtering module, which is connected between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, or the first filtering module is connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20. It can be understood that the transmission (Tx) frequency band and the reception (Rx) frequency band are relatively close, and the filter 1 requires the Rx frequency band. In this embodiment, the longitudinally coupled surface acoustic wave resonator 40 is provided in combination with the first filtering module to improve the out-of-band suppression level and improve the overall isolation.
[0067] like Figure 1 , Figure 3 , Figure 4 and Figure 6As shown, in some embodiments, the first filtering module includes at least one series arm resonator S, and at least one series arm resonator S is connected in series between the input terminal 10 and the output terminal 20, which can improve the out-of-band suppression level and improve the overall isolation. In an embodiment in which two longitudinally coupled surface acoustic wave resonators 40 are provided, and they are respectively the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b, the two longitudinally coupled surface acoustic wave resonators 40 have limited suppression in the Tx frequency band, and at least one series arm resonator S is present between the input terminal 10 and the output terminal 20, which can improve the suppression in the Tx frequency band. In one embodiment, at least one series arm resonator S is connected in series between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and in another embodiment, at least one series arm resonator S is connected in series between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20.
[0068] like Figure 1 , Figure 3 , Figure 4 and Figure 7 As shown, in some embodiments, the first filtering module includes at least one parallel arm resonator P, one end of at least one parallel arm resonator P is connected between the input terminal 10 and the output terminal 20, and the other end is grounded, which can improve the out-of-band suppression level and improve the overall isolation. In an embodiment where two longitudinally coupled surface acoustic wave resonators 40 are provided, and they are respectively the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b, the two longitudinally coupled surface acoustic wave resonators 40 have limited suppression in the Tx frequency band, and the longitudinally coupled surface acoustic wave resonator 40 needs to be used with a ladder structure. There is at least one parallel arm resonator P between the input terminal 10 and the output terminal 20, which can improve the suppression in the Tx frequency band. In one embodiment, one end of at least one parallel arm resonator P is connected between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and the other end is grounded. In another embodiment, one end of at least one parallel arm resonator P is connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, and the other end is grounded.
[0069] like Figure 1 , Figure 3 , Figure 4 and Figure 8 As shown, in some embodiments, the first filtering module includes at least one single-order resonance unit, each single-order resonance unit includes a series arm resonator S and a parallel arm resonator P, the series arm resonator S is connected between the input terminal 10 and the output terminal 20, one end of the parallel arm resonator P is connected between the input terminal 10 and the output terminal 20, and the other end of the parallel arm resonator P is grounded, which can improve the out-of-band suppression level and improve the overall isolation.
[0070] In an embodiment where two longitudinally coupled surface acoustic wave resonators 40 are provided, and they are respectively a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b, the two longitudinally coupled surface acoustic wave resonators 40 have limited suppression in the Tx frequency band, and the longitudinally coupled surface acoustic wave resonator 40 needs to be used with a ladder structure, and there is at least one single-order resonance unit between the input terminal 10 and the output terminal 20. The single-order resonance unit can be regarded as a ladder filter, which can improve the suppression in the Tx frequency band. Among them, for a single single-order resonance unit, between the input terminal 10 and the output terminal 20, the series arm resonator S can be connected first and then the parallel arm resonator P, or the parallel arm resonator P can be connected first and then the series arm resonator S, that is, along the input to the output, the series arm resonator S can be in front of the parallel arm resonator P, or the parallel arm resonator P can be in front of the series arm resonator S, which is not limited in this embodiment.
[0071] like Figure 1 , Figure 3 , Figure 4 and Figure 8 As shown, in some embodiments, in each single-stage resonance unit, the series arm resonator S is connected in series to the series arm between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, one end of the parallel arm resonator P is connected between the input terminal 10 and the series arm resonator S or between the series arm resonator S and the longitudinally coupled surface acoustic wave resonator 40, and the other end of the parallel arm resonator P is grounded. In other embodiments, in each single-stage resonance unit, the series arm resonator S is connected in series to the series arm between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, one end of the parallel arm resonator P is connected between the series arm resonator S and the output terminal 20 or between the longitudinally coupled surface acoustic wave resonator 40 and the series arm resonator S, and the other end of the parallel arm resonator P is grounded.
[0072] like Figure 1 and Fig. 9 As shown, in some embodiments, the first filtering module includes two series arm resonators S and two parallel arm resonators P, and the two series arm resonators S are connected in series between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40; among the two parallel arm resonators P, one end of one parallel arm resonator P is connected between the two series arm resonators S, and the other end is grounded; one end of the other parallel arm resonator P is connected between the series arm resonator S and the longitudinally coupled surface acoustic wave resonator 40, and the other end is grounded.
[0073] Of course, in some embodiments, the second-order resonance unit may also be connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20 .
[0074] In this embodiment, the first filtering module uses two single-order resonant units in combination, which can achieve better out-of-band suppression and will not greatly reduce the passband insertion loss due to the excessive increase of resonators. In actual application, among the two parallel arm resonators P, the position of one parallel arm resonator P is set between the two series-connected series arm resonators S, and the position of the other parallel arm resonator P can be set between the series arm resonator S and the two parallel longitudinally coupled surface acoustic wave resonators 40 (the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b connected in parallel), or can be set between the input terminal 10 and the series arm resonator S.
[0075] Combination Fig. 9 In some embodiments, of the two parallel arm resonators P, the ground end of one parallel arm resonator P is connected to the first ground terminal 30a, the ground end of the other parallel arm resonator P is connected to the second ground terminal 30b, or the ground ends of both parallel arm resonators P are connected to the first ground terminal 30a or the second ground terminal 30b. In this embodiment, the grounding method of the two parallel arm resonators P can reduce the grounding bump, and at the same time can reduce unnecessary parasitic coupling of the filter 1 caused by excessive grounding dispersion. In an embodiment in which the first filtering module only includes the parallel arm resonator P, the ground end of the parallel arm resonator P can be connected to the first ground terminal 30a or the second ground terminal 30b, so that the ground end of the parallel arm resonator P and the first ground terminal 30a or the second ground terminal 30b are grounded on the piezoelectric substrate.
[0076] In some embodiments, in combination Fig. 9 In the two-order resonance unit, the ground ends of the two parallel arm resonators P can also be respectively connected to two ground terminals 30 different from the first ground terminal 30a and the second ground terminal 30b, and the two ground terminals 30 can be grounded together with the first ground terminal 30a or the second ground terminal 30b on the piezoelectric substrate, or they can be grounded not together with the first ground terminal 30a and the second ground terminal 30b.
[0077] Combination Fig. 9 In some embodiments, the filter 1 further includes a third grounding terminal disposed on the piezoelectric substrate, the third grounding terminal is connected to the first grounding terminal 30a or the second grounding terminal 30b on the piezoelectric substrate, and the grounding ends of the two parallel arm resonators P are both connected to the third grounding terminal. In this embodiment, the third grounding terminal may share a ground with the first grounding terminal 30a or the second grounding terminal 30b on the piezoelectric substrate, or may not share a ground with the first grounding terminal 30a or the second grounding terminal 30b on the piezoelectric substrate. Preferably, the third grounding terminal shares a ground with the first grounding terminal 30a or the second grounding terminal 30b on the piezoelectric substrate, which can reduce the ground bump.
[0078] like Figure 1 and Figure 5 As shown, in some embodiments, the filter 1 further includes a first filtering module and a second filtering module, the first filtering module is connected between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and the second filtering module is connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20. In this embodiment, the longitudinally coupled surface acoustic wave resonator 40 is provided in combination with the first filtering module and the second filtering module to improve the out-of-band suppression level and improve the overall isolation.
[0079] Combination Figure 1 , Figure 5 , Figure 6 and Figure 7 In some embodiments, the first filtering module includes at least one series arm resonator S, and at least one series arm resonator S is connected in series with the series arm between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, or the first filtering module includes at least one parallel arm resonator P, and one end of each parallel arm resonator P is connected between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and the other end is grounded.
[0080] Combination Figure 1 , Figure 5 and Figure 8 In other embodiments, the first filter module includes at least one series arm resonator S and at least one parallel arm resonator P. The number of series arm resonators S and the number of parallel arm resonators P may be equal or unequal. At least one series arm resonator S is connected in series to the series arm between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40. One end of each parallel arm resonator P is connected between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and the other end is grounded. Among them, the parallel arm resonator P may be arranged between two adjacent series arm resonators S, or between the input terminal 10 and the series arm resonator S, or between the series arm resonator S and the longitudinally coupled surface acoustic wave resonator 40. This embodiment does not specifically limit the arrangement position of the parallel arm resonator P in the first filter module.
[0081] Combination Figure 1 , Figure 5 , Figure 6 and Figure 7 In some embodiments, the second filtering module includes at least one series arm resonator S, and at least one series arm resonator S is connected in series with the series arm between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, or the first filtering module includes at least one parallel arm resonator P, and one end of each parallel arm resonator P is connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, and the other end is grounded.
[0082] Combination Figure 1 , Figure 5 and Figure 8 In other embodiments, the second filter module includes at least one series arm resonator S and at least one parallel arm resonator P. The number of series arm resonators S and the number of parallel arm resonators P may be equal or unequal. At least one series arm resonator S is connected in series to the series arm between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20. One end of each parallel arm resonator P is connected between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, and the other end is grounded. Among them, the parallel arm resonator P may be arranged between two adjacent series arm resonators S, or between the series arm resonator S and the output terminal 20, or between the longitudinally coupled surface acoustic wave resonator 40 and the series arm resonator S. This embodiment does not specifically limit the arrangement position of the parallel arm resonator P in the second filter module.
[0083] like Figure 1 and Fig.10 As shown, in some embodiments, the first filter module includes a series arm resonator S and a parallel arm resonator P, and the second filter module includes a series arm resonator S and a parallel arm resonator P. The series arm resonator S of the first filter module is connected in series between the input terminal 10 and the longitudinally coupled surface acoustic wave resonator 40, and one end of the parallel arm resonator P of the first filter module is connected between the series arm resonator S of the first filter module and the longitudinally coupled surface acoustic wave resonator 40, and the other end is connected to the first ground terminal 30a or the second ground terminal 30b;
[0084] The series arm resonator S of the second filter module is connected in series between the longitudinally coupled surface acoustic wave resonator 40 and the output terminal 20, one end of the parallel arm resonator P of the second filter module is connected between the series arm resonator S of the second filter module and the output terminal 20, and the other end is connected to the first ground terminal 30a or the second ground terminal 30b.
[0085] In this embodiment, the first filter module and the second filter module both use a ladder-type structure filter 1, which can improve the out-of-band suppression level and improve the overall isolation. Moreover, the parallel arm resonator P of the first filter module and the parallel arm resonator P of the second filter module respectively share the ground terminal 30 with two longitudinally coupled surface acoustic wave resonators 40 (the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b), or both share the ground terminal 30 with the first longitudinally coupled surface acoustic wave resonator 40a or the second longitudinally coupled surface acoustic wave resonator 40b, which can reduce the ground bump, and can also reduce the unnecessary parasitic coupling of the filter 1 caused by the excessive dispersion of the ground, thereby improving the isolation.
[0086] Combination Figure 1 In some embodiments, the piezoelectric substrate includes a substrate and a piezoelectric layer, the piezoelectric layer is disposed on the substrate, and the longitudinally coupled surface acoustic wave resonator 40 is formed in the piezoelectric layer; the temperature coefficient of the substrate is smaller than the temperature coefficient of the piezoelectric layer, so that the performance and stability of the filter 1 can be improved.
[0087] In some embodiments, the substrate may be single crystal silicon, polycrystalline silicon, quartz, glass, or the like.
[0088] In some embodiments, the thickness of the substrate is greater than the thickness of the piezoelectric layer to help improve the stability of the piezoelectric substrate. The acoustic velocity or acoustic impedance of the substrate is higher than the acoustic velocity or acoustic impedance of the piezoelectric layer to reduce longitudinal leakage of acoustic wave energy.
[0089] In other embodiments, the piezoelectric substrate may be a piezoelectric layer (piezoelectric substrate), the piezoelectric layer may be a single-layer or multi-layer piezoelectric material, specifically aluminum nitride, zinc oxide, lead zirconate titanate (PZT) or a rare earth element doped material with a certain atomic ratio of the above materials, the piezoelectric layer may also be a single crystal piezoelectric material, for example, single crystal aluminum nitride, lithium niobate, lithium tantalate, quartz, etc., and this embodiment does not impose any specific restrictions on this.
[0090] In some embodiments, the piezoelectric substrate further includes an intermediate layer disposed between the piezoelectric layer and the substrate; the intermediate layer includes at least one low acoustic velocity layer or a low acoustic impedance layer, and the acoustic velocity of the intermediate layer is lower than the acoustic velocity of the piezoelectric layer.
[0091] In this embodiment, an intermediate layer is provided between the piezoelectric layer and the substrate, the intermediate layer includes at least one low acoustic velocity layer or low acoustic impedance layer, the acoustic velocity or acoustic impedance of the intermediate layer is lower than the acoustic velocity or acoustic impedance of the piezoelectric layer, the acoustic velocity or acoustic impedance of the substrate is higher than the acoustic velocity or acoustic impedance of the piezoelectric layer, the arrangement of the substrate and the intermediate layer can not only play a role in temperature compensation for the piezoelectric layer, but also form an acoustic reflection structure under the piezoelectric layer to reduce the longitudinal leakage of acoustic wave energy. The longitudinal direction is the thickness direction of the piezoelectric layer.
[0092] Combination Figure 1In some embodiments, the filter 1 further includes a temperature compensation layer, which is disposed on the piezoelectric substrate and at least covers the resonance region of the longitudinally coupled surface acoustic wave resonator 40, which can reduce the frequency shift caused by temperature changes and effectively improve the temperature stability of the filter 1. The temperature compensation layer at least covers the resonance region of the longitudinally coupled surface acoustic wave resonator 40. It can be understood that the temperature compensation layer can be an interdigital transducer 41 that completely covers the longitudinally coupled surface acoustic wave resonator 40, or even completely covers the longitudinally coupled surface acoustic wave resonator 40, or can be an interdigital transducer 41 that does not completely cover the longitudinally coupled surface acoustic wave resonator 40, for example, only covers the resonance region of the longitudinally coupled surface acoustic wave resonator 40, and does not cover the area outside the resonance region of the longitudinally coupled surface acoustic wave resonator 40.
[0093] Combination Figure 1 In some embodiments, the temperature compensation layer may be a material having a positive temperature compensation coefficient, such as silicon oxide, silicon oxide doped with other elements, etc., to adjust the frequency temperature coefficient of the filter 1. For example, the material of the temperature compensation layer may be at least one of dielectric materials having a positive temperature compensation coefficient, such as silicon oxide, silicon nitride, silicon oxynitride, tellurium dioxide, silicon oxyfluoride, etc. Among them, the material of the temperature compensation layer is usually one of the above materials, that is, the material of the temperature compensation layer is a single material. Of course, in some feasible implementations, the material of the temperature compensation layer may also be a mixed material, in which case the material of the temperature compensation layer may be a mixture of any of the above materials, or a mixture of one or more of the above materials with other materials.
[0094] Combination Figure 1 In some embodiments, the filter 1 further includes a passivation layer, which is disposed on the piezoelectric substrate and covers at least the longitudinally coupled surface acoustic wave resonator 40. In this embodiment, the passivation layer can protect the longitudinally coupled surface acoustic wave resonator 40. It should be understood that the passivation layer can only cover the longitudinally coupled surface acoustic wave resonator 40, or can cover the piezoelectric substrate and all components on the piezoelectric substrate to protect the filter 1 and prevent the filter 1 from being affected by water vapor or the like.
[0095] In a specific embodiment, the material of the passivation layer may be silicon nitride (SiN), silicon oxynitride (SiON) or other materials, so that the passivation layer can both adjust the frequency and protect the filter 1 .
[0096] It should be noted that the filter 1 of the embodiment of the present application can be applicable to a duplexer or a multiplexer, and the present application does not limit this.
[0097] like Figure 1 and Fig.11As shown, this embodiment also provides a radio frequency front-end module 2, characterized in that it includes a filter 1 in any of the above-mentioned embodiments, which can move the transmission zero point of the filter 1 in the radio frequency front-end module 2 to a low frequency, thereby improving the isolation of the filter 1.
[0098] like Figure 1 and Fig.11 As shown, in some embodiments, the filter 1 is a receiving filter, and the RF front-end module 2 also includes a transmitting filter constructed on a piezoelectric substrate, wherein the transmitting filter includes a transmitting terminal TX and a circuit module connected between the transmitting terminal TX and the antenna terminal ANT. The circuit module can be set according to actual needs. For example, the circuit module is set to include a ladder filter so that it has a filtering and frequency selection function. For the transmitting filter, the signal is transmitted from the transmitting terminal TX to the antenna terminal ANT and finally emitted outward.
[0099] like Fig.12 As shown, in some embodiments, the receiving filter of the RF front-end module 2 includes a first filtering module, which is connected between the antenna terminal ANT and the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b connected in parallel. The first filtering module adopts a two-order resonance unit, that is, two single-order resonance units, which can achieve better out-of-band suppression and will not greatly reduce the passband insertion loss due to the excessive addition of resonators.
[0100] like Fig.11 and Fig.13 As shown, in some embodiments, the receiving filter of the RF front-end module 2 includes a first filtering module and a second filtering module. The first filtering module is connected between the antenna terminal ANT and the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b connected in parallel. The second filtering module is connected between the first longitudinally coupled surface acoustic wave resonator 40a and the second longitudinally coupled surface acoustic wave resonator 40b connected in parallel and the receiving terminal RX. The first filtering module and the second filtering module both adopt single-order resonant units, which can achieve better out-of-band suppression and will not greatly reduce the passband insertion loss due to the excessive increase of resonators.
[0101] Based on the above filter 1, this embodiment also provides embodiment 1 and comparative example, and compares embodiment 1 and comparative example. Figure 2In the first embodiment, an antenna terminal ANT, a receiving terminal RX, a first grounding terminal 30a, a second grounding terminal 30b, and a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b connected in parallel between the antenna terminal ANT and the receiving terminal RX are formed on the piezoelectric substrate. The first grounding terminal 30a is not connected to the second grounding terminal 30b on the piezoelectric substrate. The grounding end of the first longitudinally coupled surface acoustic wave resonator 40a and the grounding end of the second longitudinally coupled surface acoustic wave resonator 40b are connected to the first grounding terminal 30a and the second grounding terminal 30b, respectively.
[0102] In the comparative example, Fig.14 An antenna terminal ANT, a receiving terminal RX, a ground terminal 30, and a first longitudinally coupled surface acoustic wave resonator 40a and a second longitudinally coupled surface acoustic wave resonator 40b connected in parallel between the antenna terminal ANT and the receiving terminal RX are formed on the piezoelectric substrate. The ground end of the first longitudinally coupled surface acoustic wave resonator 40a and the ground end of the second longitudinally coupled surface acoustic wave resonator 40b are both connected to the same ground terminal 30.
[0103] Combination Figure 1 , Figure 2 and Fig.14 It can be seen that in the first embodiment, the two longitudinally coupled surface acoustic wave resonators 40 connected in parallel are grounded separately on the piezoelectric substrate, while in the comparative example, the two longitudinally coupled surface acoustic wave resonators 40 connected in parallel are grounded in common on the piezoelectric substrate. Fig.15 1 is a comparison diagram of the isolation between the parallel longitudinally coupled surface acoustic wave resonators 40 with separate grounding and common grounding. In the figure, the solid line is the embodiment of the present application, i.e., the effect of the parallel longitudinally coupled surface acoustic wave resonators 40 with separate grounding, and the dotted line is the comparative example of the present application, i.e., the effect of the parallel longitudinally coupled surface acoustic wave resonators 40 with common grounding. The horizontal axis is the frequency in MHz, and the vertical axis is the transmission coefficient in dB. Fig.15 It can be seen that in the Tx frequency band, the transmission zero point of the first embodiment moves toward the low frequency, the solid line is below the dotted line, and the transmission coefficient of the embodiment is smaller than the transmission coefficient of the comparative example, indicating that the isolation from RX to TX of the first embodiment is better than that of the comparative example.
[0104] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the application concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.
Claims
1. A filter, characterized in that: include: Input terminals and output terminals; at least two longitudinally coupled surface acoustic wave resonators connected in parallel between the input terminal and the output terminal, the at least two longitudinally coupled surface acoustic wave resonators being formed on the same piezoelectric substrate, each of the longitudinally coupled surface acoustic wave resonators comprising at least two interdigital transducers; at least two ground terminals, the at least two ground terminals comprising a first ground terminal and a second ground terminal isolated from each other on the piezoelectric substrate; The at least two longitudinally coupled surface acoustic wave resonators include a first longitudinally coupled surface acoustic wave resonator and a second longitudinally coupled surface acoustic wave resonator, the ground end of the first longitudinally coupled surface acoustic wave resonator is connected to the first ground terminal, and the ground end of the second longitudinally coupled surface acoustic wave resonator is connected to the second ground terminal.
2. The filter according to claim 1, characterized in that The filter is a receiving filter, the input terminal is an antenna terminal, and the output terminal is a receiving terminal.
3. The filter according to claim 1, characterized in that The filter further includes a first filtering module, which is connected between the input terminal and the longitudinally coupled surface acoustic wave resonator, or between the longitudinally coupled surface acoustic wave resonator and the output terminal.
4. The filter according to claim 3, characterized in that The first filtering module includes at least one series arm resonator, and the at least one series arm resonator is connected in series between the input terminal and the output terminal; or, The first filtering module comprises at least one parallel arm resonator, one end of the at least one parallel arm resonator is connected between the input terminal and the output terminal, and the other end is grounded; or, The first filtering module includes at least one single-order resonance unit, each single-order resonance unit includes a series arm resonator and a parallel arm resonator, the series arm resonator is connected between the input terminal and the output terminal, one end of the parallel arm resonator is connected between the input terminal and the output terminal, and the other end of the parallel arm resonator is grounded.
5. The filter according to claim 3, characterized in that The first filtering module comprises two series arm resonators and two parallel arm resonators, and the two series arm resonators are connected in series between the input terminal and the longitudinally coupled surface acoustic wave resonator; Among the two parallel arm resonators, one end of one of the parallel arm resonators is connected between the two series arm resonators, and the other end is grounded; one end of the other parallel arm resonator is connected between the series arm resonator and the longitudinally coupled surface acoustic wave resonator, and the other end is grounded.
6. The filter according to claim 5, characterized in that Among the two parallel arm resonators, the ground end of one of the parallel arm resonators is connected to the first ground terminal, and the ground end of the other parallel arm resonator is connected to the second ground terminal, or the ground ends of both parallel arm resonators are connected to the first ground terminal or the second ground terminal; or, The filter further includes a third grounding terminal disposed on the piezoelectric substrate, the third grounding terminal is connected to the first grounding terminal or the second grounding terminal on the piezoelectric substrate, and the grounding ends of the two parallel arm resonators are both connected to the third grounding terminal.
7. The filter according to claim 1, characterized in that The filter further comprises a first filtering module and a second filtering module, wherein the first filtering module is connected between the input terminal and the longitudinally coupled surface acoustic wave resonator, and the second filtering module is connected between the longitudinally coupled surface acoustic wave resonator and the output terminal.
8. The filter according to claim 7, characterized in that The first filtering module includes a series arm resonator and a parallel arm resonator, and the second filtering module includes a series arm resonator and a parallel arm resonator. The series arm resonator of the first filter module is connected in series between the input terminal and the longitudinally coupled surface acoustic wave resonator, one end of the parallel arm resonator of the first filter module is connected between the series arm resonator of the first filter module and the longitudinally coupled surface acoustic wave resonator, and the other end is connected to the first ground terminal or the second ground terminal; The series arm resonator of the second filter module is connected in series between the longitudinally coupled surface acoustic wave resonator and the output terminal, one end of the parallel arm resonator of the second filter module is connected between the series arm resonator of the second filter module and the output terminal, and the other end is connected to the first ground terminal or the second ground terminal.
9. The filter according to any one of claims 1 to 8, characterized in that: The piezoelectric substrate comprises a substrate and a piezoelectric layer, the piezoelectric layer is arranged on the substrate, and the longitudinally coupled surface acoustic wave resonator is formed on the piezoelectric layer; The temperature coefficient of the substrate is smaller than the temperature coefficient of the piezoelectric layer, and / or the thickness of the substrate is larger than the thickness of the piezoelectric layer.
10. The filter according to claim 9, characterized in that The piezoelectric substrate further comprises an intermediate layer, wherein the intermediate layer is arranged between the piezoelectric layer and the substrate; The intermediate layer includes at least one low acoustic velocity layer or a low acoustic impedance layer, and the acoustic velocity of the intermediate layer is lower than the acoustic velocity of the piezoelectric layer.
11. The filter according to any one of claims 1 to 8, characterized in that: The filter further comprises a temperature compensation layer, which is disposed on the piezoelectric substrate and at least covers the resonance region of the longitudinally coupled surface acoustic wave resonator; and / or, The filter further comprises a passivation layer, which is arranged on the piezoelectric substrate and at least covers the longitudinally coupled surface acoustic wave resonator.
12. A radio frequency front-end module, characterized in that: Comprising a filter as described in any one of claims 1-11.