Filter circuit topological structure, radio frequency module and electronic equipment

Abstract

The invention discloses a filter circuit topological structure, a radio frequency module and electronic equipment, and relates to the technical field of filters, and the filter circuit topological structure comprises an input end and an output end; the plurality of series resonators are sequentially connected between the input end and the output end; a plurality of parallel resonators, wherein two adjacent series resonators are grounded based on one parallel resonator; wherein the series resonator and the parallel resonator are surface acoustic wave resonators with reflecting gratings; the numbers of finger strips of the interdigital electrodes in the surface acoustic wave resonators are the same; and the number of the fingers of the reflecting grating in the series resonator is smaller than that of the fingers of the reflecting grating in the parallel resonator. According to the invention, the influence of fine ripples below the series resonant frequency in the series resonator on the shape of the filter passband can be effectively weakened, so that the influence of clutters in the series resonator on the filter passband can be reduced or even avoided.

Description

Technical Field

[0001] The present application relates to the technical field of filters, and in particular, to a filter circuit topology, a radio frequency module, and an electronic device. Background Art

[0002] A surface acoustic wave resonator (Surface Acoustic Wave, abbreviated as SAW) is a device widely used in the radio frequency field, which combines low insertion loss and good suppression performance, and has a small volume at the same time. It mainly uses the piezoelectric effect to convert electrical energy and mechanical energy into each other, and can be used to combine to achieve a gating characteristic for signal transmission.

[0003] Multiple surface acoustic wave resonators can be interconnected to form a filter. In the existing filter design, the passband of the filter is affected by the clutter of the surface acoustic wave resonator, resulting in performance deterioration. Summary of the Invention

[0004] In view of the above problems, the present application provides a filter circuit topology, a radio frequency module, and an electronic device to achieve the purpose of reducing the influence of clutter in the surface acoustic wave resonator on the filter performance. The specific solutions are as follows:

[0005] The first aspect of the present application provides a filter circuit topology, including:

[0006] An input end and an output end;

[0007] Multiple series resonators, which are sequentially connected between the input end and the output end;

[0008] Multiple parallel resonators, and each adjacent two series resonators are grounded based on a parallel resonator respectively;

[0009] Wherein, both the series resonator and the parallel resonator are surface acoustic wave resonators with reflection gratings; the number of finger bars of the interdigital electrodes in each surface acoustic wave resonator is the same; the number of finger bars of the reflection grating in the series resonator is less than the number of finger bars of the reflection grating in the parallel resonator.

[0010] Optionally, in the above filter circuit topology, the number of finger bars of the reflection grating in the series resonator does not exceed A, and at least part of the number of finger bars of the reflection grating in the series resonator is less than A;

[0011] Wherein, A is the minimum value of the number of finger bars of the reflection grating in each parallel resonator.

[0012] Optionally, in the above filter circuit topology, the number of finger bars of the reflection grating in each series resonator is less than A.

[0013] Optionally, in the above filter circuit topology, the number of fingers of the reflection grating in each series resonator is B, and B is a positive integer less than A.

[0014] Optionally, in the above filter circuit topology, the number of fingers of the reflection grating in at least two series resonators is different.

[0015] Optionally, in the above filter circuit topology, if the number of fingers of the reflection grating in two series resonators is different, then the number of fingers of the reflection grating in the one closer to the output end is C, and the number of fingers of the reflection grating in the one farther from the output end is D, where both C and D are positive integers not exceeding A, and C is less than D.

[0016] Optionally, in the above filter circuit topology, the number of fingers of the reflection grating in the parallel resonators is the same.

[0017] Optionally, in the above filter circuit topology, the number of fingers of the reflection grating in at least two parallel resonators is different.

[0018] Optionally, in the above filter circuit topology, if the number of fingers of the reflection grating in two parallel resonators is different, then the number of fingers of the reflection grating in the one closer to the output end is E, and the number of fingers of the reflection grating in the one farther from the output end is F, where both E and F are positive integers not less than A, and E is greater than F.

[0019] Optionally, in the above filter circuit topology, it includes at least one of the following methods:

[0020] The input end is grounded based on the first inductor;

[0021] The output end is grounded based on the second inductor;

[0022] At least one parallel resonator is grounded based on the third inductor.

[0023] The second aspect of the present application provides a radio frequency module, including the filter circuit topology of any one of the above.

[0024] The third aspect of the present application provides an electronic device, including the above radio frequency module.

[0025] By means of the above technical solutions, in the filter circuit topology, radio frequency module, and electronic device provided by the present application, the number of fingers of the reflection grating in the series resonator is set to be less than that in the parallel resonator, so that the series resonator has a smaller number of reflection grating fingers relative to the parallel resonator, which can effectively weaken the influence of the small ripples below the series resonance frequency in the series resonator on the passband shape of the filter, thereby reducing or even avoiding the influence of clutter in the series resonator on the filter passband, and improving the reliability and stability of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0027] The structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those who are familiar with this technology to understand and read, and are not used to limit the limiting conditions that the present application can be implemented. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present application can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present application.

[0028] Figure 1 It is a top view of a surface acoustic wave resonator;

[0029] Figure 2 It is Figure 1 a sectional view of the shown surface acoustic wave resonator along the P-P' direction;

[0030] Figure 3 It is a top view of another surface acoustic wave resonator;

[0031] Figure 4 It is a top view of yet another surface acoustic wave resonator;

[0032] Figure 5 It is a sectional view of a surface acoustic wave resonator;

[0033] Figure 6 It is a sectional view of another surface acoustic wave resonator;

[0034] Figure 7 It is an equivalent circuit diagram of a filter circuit topology;

[0035] Figure 8 It is based on Figure 7 the passband curve graph of a filter based on the shown filter circuit topology;

[0036] Figure 9 It is an equivalent circuit diagram of a filter circuit topology provided by an embodiment of the present application;

[0037] Figure 10 It is Figure 7 the real part of the admittance curve graph when the number of finger bars in the reflection grating of each series resonator in the shown filter circuit topology is not optimized;

[0038] Figure 11 For Figure 7 The real part of the admittance curve of the first series resonator s1 in the filter circuit topology shown;

[0039] Figure 12 For Figure 11 The enlarged local view of the real part of the admittance curve shown;

[0040] Figure 13 For Figure 7 The real part of the admittance curve of the second series resonator s2 in the filter circuit topology shown;

[0041] Figure 14 For Figure 13 The enlarged local view of the real part of the admittance curve shown;

[0042] Figure 15 For Figure 7 The real part of the admittance curve of the third series resonator s3 in the filter circuit topology shown;

[0043] Figure 16 For Figure 15 The enlarged local view of the real part of the admittance curve shown;

[0044] Figure 17 For Figure 7 The real part of the admittance curve of the fourth series resonator s4 in the filter circuit topology shown;

[0045] Figure 18 For Figure 17 The enlarged local view of the real part of the admittance curve shown;

[0046] Figure 19 For Figure 7 The real part of the admittance curve of the fifth series resonator s5 in the filter circuit topology shown;

[0047] Figure 20 For Figure 19 The enlarged local view of the real part of the admittance curve shown;

[0048] Figure 21 For Figure 7 The real part of the admittance curve of the first parallel resonator p1 in the filter circuit topology shown;

[0049] Figure 22 For Figure 7 The real part of the admittance curve of the second parallel resonator p2 in the filter circuit topology shown;

[0050] Figure 23 For Figure 7 The real part of the admittance curve of the third parallel resonator p3 in the filter circuit topology shown;

[0051] Figure 24 For Figure 7 The real part of the admittance curve of the fourth parallel resonator p4 in the filter circuit topology shown;

[0052] Figure 25 The passband curve of the filter circuit topology;

[0053] Figure 26 For Figure 25 The out-of-band rejection and steepness curve comparison diagram of two filter circuit topologies in;

[0054] Reference numerals:

[0055] 100 - Interdigital transducer; 101 - Interdigital electrode; 102 - First finger bar; 103 - Second finger bar; 104 - Bus bar; 105 - Piezoelectric substrate; 1051 - Substrate; 1052 - Piezoelectric thin film; 1053 - Functional layer; 106 - False finger; 107 - Reflection grating; 108 - Third finger bar; 109 - Temperature compensation layer; 110 - Series resonator; 111 - Parallel resonator; 112 - First curve; 113 - Second curve; In - Input terminal; Out - Output terminal; X - First direction; Y - Second direction; A_Lp - First inductor; L1_Lp - Second inductor; L1_L1 - Third inductor. Detailed implementation manners

[0056] Next, the embodiments in the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Those of ordinary skill in the art can know that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0057] Refer to Figure 1 and Figure 2 , Figure 1 is a top view of a surface acoustic wave resonator, Figure 2 For Figure 1 The sectional view of the surface acoustic wave resonator shown along the P - P' direction. The surface acoustic wave resonator includes a piezoelectric substrate 105 and an interdigital transducer 100 located on the surface of the piezoelectric substrate 105. The interdigital transducer 100 includes two mutually nested interdigital electrodes 101. In the same interdigital transducer 100, the finger bars of one interdigital electrode 101 are the first finger bars 102, and the finger bars of the other interdigital electrode 101 are the second finger bars 103. The first finger bars 102 and the second finger bars 103 are alternately arranged in the first direction X so that the two interdigital electrodes 101 are mutually nested. Among them, the first direction X is parallel to the plane where the piezoelectric substrate 105 is located.

[0058] As Figure 1 and Figure 2As shown, in the surface acoustic wave resonator, each finger of the interdigital electrode 101 is parallel to the second direction Y. The second direction Y is parallel to the plane where the piezoelectric substrate 105 is located and perpendicular to the first direction X. The first finger 102 and the second finger 103 are respectively connected to different bus bars 104. The upper ends of the first fingers 102 are all connected to one bus bar 104, and the lower ends of the second fingers 103 are all connected to another bus bar 104. Each finger of the interdigital electrode 101 is located between the two bus bars.

[0059] The extending direction of the bus bar 104 is parallel to the main acoustic mode propagation direction. The extending directions of the first finger 102 and the second finger 103 can be perpendicular to the extending direction of the bus bar 104. In other ways, it can also be set that the first finger 102 and the second finger 103 are not perpendicular to the bus bar.

[0060] Reference Figure 3 , Figure 3 is a top view of another surface acoustic wave resonator. Based on the surface acoustic wave resonators with other structures, Figure 3 As shown in the surface acoustic wave resonator, the surface acoustic wave resonator further includes dummy fingers 106. Specifically, the bus bar 104 connected to the first finger 102 is connected with a plurality of dummy fingers 106 that are opposite to the second finger 103 one by one, and the bus bar 104 connected to the second finger 103 is connected with a plurality of dummy fingers 106 that are opposite to the first finger 102 one by one. In this way, dummy fingers 106 corresponding to the fingers in the other interdigital electrode 101 are arranged in the bus bar 104 of one interdigital electrode 101 to form better resonator performance through the dummy fingers 106.

[0061] Reference Figure 4 , Figure 4 is a top view of yet another surface acoustic wave resonator. Based on the surface acoustic wave resonators with other structures, Figure 4 As shown in the surface acoustic wave resonator, reflection gratings 107 are respectively arranged on both sides of the interdigital electrode 101 to reflect acoustic waves through the reflection gratings 107, thereby helping to form better resonance and improving the transmission performance of the resonator. Among them, the reflection grating 107 includes a plurality of parallel arranged fingers. It is assumed that the fingers in the reflection grating 107 are the third fingers 108. The fingers in the reflection grating 107 can be arranged parallel to the fingers in the interdigital electrode 101.

[0062] Reference Figure 5 , Figure 5 is a sectional view of a surface acoustic wave resonator. Based on the surface acoustic wave resonators with other structures, Figure 5 As shown, the surface acoustic wave resonator further includes a temperature compensation layer 109. Figure 5The surface acoustic wave resonator shown is a temperature-compensated surface acoustic wave resonator (TC-SWA). A temperature compensation layer 109 is further covered on the surface of the interdigital electrode 101 to solve the temperature drift problem through the temperature compensation layer 109. Optionally, the temperature compensation layer 109 can be a silicon dioxide layer.

[0063] Reference Figure 6 , Figure 6 is a cross-sectional view of another surface acoustic wave resonator. Based on the surface acoustic wave resonator of other structures, Figure 6 the surface acoustic wave resonator shown is a thin film surface acoustic wave resonator (TF-SAW). The piezoelectric substrate 105 includes a substrate 1051, a functional layer 1053, and a piezoelectric thin film 1052 stacked in sequence. The interdigital electrode 101 is located on the surface of the piezoelectric thin film 1052 facing away from the substrate 1051. Among them, the functional layer 1053 can include a silicon dioxide layer.

[0064] As described in the background art, multiple surface acoustic wave resonators can be interconnected to form a filter. In current conventional filters, the passband of the filter is easily affected by clutter in the surface acoustic wave resonator, resulting in deterioration of the filter performance.

[0065] When the filter has high requirements for both steepness and out-of-band rejection, the setting of filter parameters will tend to give priority to meeting indicators such as in-band loss, out-of-band rejection, and steepness; in addition, the frequency positions of some surface acoustic wave resonators in the filter will be relatively fixed, and the influence of clutter on the passband cannot be improved by moving the resonant frequency. In the above design process, fine ripples or collapses often appear in the filter passband, which will cause problems such as increased insertion loss of the filter.

[0066] Reference Figure 7 and Figure 8 , FIG. 7 is an equivalent circuit diagram of a filter circuit topology, Figure 8 is based on Figure 7 the passband curve diagram of the filter of the filter circuit topology shown. Figure 7 is an equivalent circuit diagram of a GPS L1 filter, which is a filter specifically designed to process L1 band signals in GPS signals. Figure 8 In, the horizontal axis is frequency, the unit is GHz, and the vertical axis is signal power, the unit is dB.

[0067] As Figure 7 shown, the filter circuit topology includes a plurality of series resonators 110 connected in sequence between the input terminal In and the output terminal Out. On the series path from the input terminal In to the output terminal Out, the plurality of series resonators 110 are successively the first series resonator s1 to the n + 1 series resonator s n+1 , where n is a positive integer. Figure 7In the illustrated manner, n = 4 is taken as an example for illustration. A grounded parallel resonator 111 is connected between every two adjacent series resonators 110. Therefore, when a grounded parallel resonator 111 is connected between every two of the n + 1 series resonators 110, there are a total of n parallel resonators 111 in the filter. On the series path from the input terminal In to the output terminal Out, these n parallel resonators 111 are the 1st parallel resonator p1 to the nth parallel resonator p n . Among them, the input terminal In is grounded through the first inductor A_Lp, the output terminal Out is grounded through the second inductor L1_Lp, and at least some of the parallel resonators 111 are grounded through the third inductor L1_L1.

[0068] In the embodiments of the present application, the value of n can be set based on the filter design parameters. n can be any positive integer, and the embodiments of the present application do not limit the value of n, not limited to Figure 7 the illustrated n = 4.

[0069] As Figure 8 shown by the passband curve between the two vertical lines on the left side in, there is a large amplitude collapse in the area shown between the two vertical lines of the passband curve, and this collapse will cause problems such as an increase in the insertion loss of the filter. The inventor's research found that the small ripples below the series resonance frequency in the series resonator 110 cause the Figure 8 shown passband left-side collapse problem in the filter.

[0070] To solve the above problems, the embodiments of the present application provide a filter circuit topology, including:

[0071] An input terminal and an output terminal;

[0072] Multiple series resonators, which are sequentially connected between the input terminal and the output terminal;

[0073] Multiple parallel resonators, with a parallel resonator grounded between every two adjacent series resonators respectively;

[0074] Among them, both the series resonator and the parallel resonator are surface acoustic wave resonators with reflection gratings; the number of finger bars of the interdigital electrodes in each surface acoustic wave resonator is the same; the number of finger bars of the reflection grating in the series resonator is less than the number of finger bars of the reflection grating in the parallel resonator.

[0075] In the embodiments of the present application, the number of fingers of the reflection grating in the series resonator is set to be less than the number of fingers of the reflection grating in the parallel resonator, so that the series resonator has a smaller number of reflection grating fingers relative to the parallel resonator, which can effectively reduce the influence of the small ripples below the series resonance frequency in the series resonator on the passband shape of the filter, thereby reducing or even avoiding the influence of clutter in the series resonator on the filter passband, and improving the reliability and stability of the filter.

[0076] In the embodiments of the present application, both the series resonator and the parallel resonator are surface acoustic wave resonators with reflection gratings, and the structure of the surface acoustic wave resonator can be Figure 4 as shown, or Figure 4 the combined structure of the shown surface acoustic wave resonator and other surface acoustic wave resonators. The embodiments of the present application do not limit the specific structure of the surface acoustic wave resonator.

[0077] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0078] Refer to Figure 9 , Figure 9 which is an equivalent circuit diagram of a filter circuit topology provided by an embodiment of the present application. The shown filter circuit topology includes:

[0079] An input terminal In and an output terminal Out;

[0080] A plurality of series resonators 110, which are sequentially connected between the input terminal In and the output terminal Out;

[0081] A plurality of parallel resonators 111, and adjacent two series resonators 110 are respectively grounded based on one parallel resonator 111;

[0082] Among them, both the series resonator 110 and the parallel resonator 111 are surface acoustic wave resonators with reflection gratings; the number of fingers of the interdigital electrodes in each surface acoustic wave resonator is the same; the number of fingers of the reflection grating in the series resonator 110 is less than the number of fingers of the reflection grating in the parallel resonator 111.

[0083] In the embodiments of the present application, the number of series resonators 110 is n + 1, and the corresponding number of parallel resonators 111 is n. As Figure 9 shown, on the series path from the input terminal In to the output terminal Out, the n + 1 series resonators 110 are sequentially the first series resonator s1 to the n + 1th series resonator s n+1 , where n is a positive integer; the n parallel resonators 111 are sequentially the first parallel resonator p1 to the nth parallel resonator p n . The i-th series resonator s iwith the (i + 1)-th series resonator s i+1 is grounded through the i-th parallel resonator p i , where i is a positive integer not greater than n.

[0084] Figure 9 In the manner shown, taking n = 4 as an example for illustration. Between the first series resonator s1 and the second series resonator s2, it is grounded through the first parallel resonator p1. Between the second series resonator s2 and the third series resonator s3, it is grounded through the second parallel resonator p2. Between the third series resonator s3 and the fourth series resonator s4, it is grounded through the third parallel resonator p3. Between the fourth series resonator s4 and the fifth series resonator s5, it is grounded through the fourth parallel resonator p4. In the embodiments of the present application, the value of n can be set based on the filter design parameters, and n can be any positive integer. The embodiments of the present application do not limit the value of n and are not limited to Figure 9 the n = 4 shown.

[0085] In the embodiments of the present application, the number of fingers of the reflection grating in the series resonator 110 is set to be less than the number of fingers of the reflection grating in the parallel resonator 111, so that the series resonator 110 has a smaller number of reflection grating fingers relative to the parallel resonator 111, which can effectively weaken the influence of the fine ripples below the series resonance frequency in the series resonator 110 on the passband shape of the filter, thereby reducing or even avoiding the influence of clutter in the series resonator 110 on the passband of the filter, and improving the reliability and stability of the filter.

[0086] In the filter circuit topology, both the series resonator 110 and the parallel resonator 111 are surface acoustic wave resonators with reflection gratings. Based on the reflection of acoustic waves by the reflection gratings, good resonance can be formed in each resonator to improve the transmission performance of the resonator. In addition, since the reflection gratings in the series resonator 110 and the parallel resonator 111 have different numbers of fingers, a coupling that can broaden the stopband suppression range can be formed based on the differential design of the reflection gratings of the series resonator 110 and the parallel resonator 111 to improve the performance of the filter.

[0087] In the filter circuit topology, the minimum value of the number of fingers of the reflection grating in each parallel resonator 111 is A. That is to say, n at least one of the reflection gratings of the first parallel resonator p1 to the n-th parallel resonator p has the number of fingers A, and the number of fingers of the reflection gratings in each parallel resonator 111 is not less than A. A is a set positive integer.

[0088] The value of A is related to the design parameters of the parallel resonator 111 in the filter. For example, A can be set to 50. Optionally, A can be not less than 40. Further, A can be not greater than 100. In the embodiments of the present application, A is not limited to 50, and can also be any one of 40, 45, 60, 66, and 90. The embodiments of the present application do not limit the value of A.

[0089] In the embodiments of the present application, the number of fingers of the reflection grating in the series resonator 110 does not exceed A, and the number of fingers of the reflection grating in at least part of the series resonators 110 is less than A. For example, when A = 50, the number of fingers of the reflection grating in at least part of the series resonators can be set to 10. For the series resonator 110 in which the number of fingers of the reflection grating is less than A, the number of fingers of the reflection grating is not limited to 10. Based on different values of A, the number of fingers of the reflection grating can be any one of 13, 20, 25, 30, and 35.

[0090] For the series resonator 110 in which the number of fingers of the reflection grating is less than A, reducing the number of fingers in the reflection grating can suppress multiple reflections, optimize impedance matching, and weaken parasitic modes, effectively reducing the fine ripples in the low frequency band.

[0091] In one implementation, the number of fingers of the reflection grating in each series resonator is less than A. In this way, setting the number of fingers of the reflection grating in all the series resonators 110 to be less than A can enable each series resonator 110 to suppress multiple reflections, optimize impedance matching, and weaken parasitic modes by reducing the number of fingers in the reflection grating, effectively reducing the fine ripples in the low frequency band.

[0092] If the number of fingers of the reflection grating in each series resonator is less than A, the number of fingers of the reflection grating in each series resonator 110 can be set to B, where B is a positive integer less than A. The interdigital transducer has a reflection grating on each of the two opposite sides in the first direction. B is the number of fingers in a single-sided reflection grating (i.e., Figure 4 the number of the third finger 108 in the single-sided reflection grating 107). In this way, the reflection gratings in each series resonator 110 can have the same number of fingers. While enabling each series resonator 110 to reduce the fine ripples in the low frequency band by reducing the number of fingers in the reflection grating, it can also make the reflection gratings in each series resonator 110 have the same number of fingers, facilitating the process preparation of the reflection gratings in each series resonator 110 based on the same number of fingers.

[0093] Based on other implementation manners of the embodiments of the present application, in one implementation manner, the number of finger bars of the reflection grating in at least two series resonators 110 can also be different. In this way, by differentiating the number of finger bars of the reflection grating in the series resonator 110, the resonant frequencies of each series resonator 110 can be differentially designed to further optimize the performance of the filter.

[0094] If the number of finger bars of the reflection grating in at least two series resonators 110 is different, for two series resonators 110 with different numbers of finger bars of the reflection grating, the number of finger bars of the reflection grating of at least one of them is less than A. It can be that the number of finger bars of the reflection gratings of both is less than A, or the number of finger bars of the reflection grating of one is less than A, and the number of finger bars of the reflection grating of the other is not less than A.

[0095] Optionally, if the number of finger bars of the reflection grating in at least two series resonators 110 is different, the number of finger bars of the reflection gratings of both can be made less than A. In this way, while the series resonator 110 reduces the fine ripples by reducing the number of finger bars in the reflection grating, it can also differentially modulate the fine ripples in each series resonator 110 by differentiating the number of finger bars of the reflection grating in different series resonators 110, so as to better optimize the fine ripples in each series resonator 110 and improve the performance of the filter.

[0096] In one implementation manner, if the number of finger bars of the reflection grating in two series resonators 110 is different, then the number of finger bars of the reflection grating in the one closer to the output terminal Out is C, and the number of finger bars of the reflection grating in the one farther from the output terminal is D, where both C and D are positive integers not exceeding A, and C is less than D. In the filter, the interference of the fine ripples in the series resonator 110 closer to the output terminal Out to the output terminal Out is more obvious. Based on this, in this way, setting the reflection grating in the series resonator 110 closer to the output terminal Out to have a smaller number of finger bars can further reduce the influence of the fine ripples in the series resonator 110 on the performance of the filter.

[0097] Optionally, the number of finger bars of the reflection gratings in each series resonator 110 can be set to be different from each other, and on the series path from the input terminal In to the output terminal Out, the number of finger bars of the reflection gratings in each series resonator decreases in sequence. In this way, the number of finger bars of the reflection grating in the series resonator 110 closer to the input terminal In can be more, which can provide a higher reflection coefficient and is convenient for impedance matching with the source impedance. It can also make the number of finger bars of the reflection grating in the series resonator 110 closer to the output terminal Out less and the reflection coefficient lower. Among them, the source impedance matching is the impedance matching at the input terminal In of the filter. Good source impedance matching can ensure that the signal will not be reflected due to impedance discontinuity during transmission, thereby reducing signal loss and interference.

[0098] In addition, this structure with a gradually decreasing number of reflective grating fingers on the series path can achieve a gradual matching with the load impedance, reduce signal reflection loss, and improve transmission efficiency. It can also avoid impedance mismatch caused by sudden changes by gradually adjusting the reflection intensity, thereby reducing the insertion loss within the passband. Moreover, it can enable the reflective grating of the front-stage series resonator 110 to have a high reflection ability to form a steep out-of-band suppression, and the reflective grating of the rear-stage series resonator 110 to have a lower reflection ability, so that the reflective grating with lower reflection ability in the rear stage can smooth the passband ripple and ensure uniform transmission of signals within the passband. The front-stage series resonator 110 can enhance the frequency selection characteristic through a larger number of reflective grating fingers, and the rear-stage series resonator can balance the bandwidth and selectivity through a smaller number of reflective grating fingers.

[0099] Specifically, this structure with a gradually decreasing number of reflective grating fingers on the series path can make the number of fingers of the reflective grating in each series resonator 110 form a gradually decreasing gradient change, disrupt the periodic reflective grating path of parasitic acoustic waves, and suppress spurious resonance and out-of-band noise.

[0100] Based on other embodiments of the present application, in one embodiment, the number of fingers of the reflective grating in the parallel resonator 111 can be set to be the same. For example, the number of fingers of the reflective grating in each parallel resonator 111 can be set to A. This method can make the reflective gratings in each parallel resonator 111 have the same number of fingers, facilitate the preparation of the parallel resonator 111 based on the same process parameters, and simplify the preparation process of each parallel resonator 111 in the filter.

[0101] Based on other embodiments of the present application, in one embodiment, the number of fingers of the reflective grating in at least two parallel resonators 111 can be set to be different. In this method, the performance of the filter can be further improved by optimizing the Q value and bandwidth through the differential design of the number of fingers of the reflective grating in the parallel resonator 111.

[0102] In the embodiment of the present application, if the number of fingers of the reflective grating in two parallel resonators 111 is different, then the number of fingers of the reflective grating in the one closer to the output end Out is E, and the number of fingers of the reflective grating in the one farther from the output end is F, where both E and F are positive integers not less than A, and E is greater than F.

[0103] In the filter, using a larger number of fingers for the reflection grating in the parallel resonator 111 can enhance the stopband suppression depth, improve frequency selectivity, reduce frequency deviation, optimize impedance matching, and suppress parasitic modes. Moreover, the parallel resonator 111 closer to the output terminal Out has a more significant effect on the output terminal Out. Based on this, setting E greater than F enables the parallel resonator 111 with a larger number of reflection grating fingers to better act on the output terminal Out, thereby better improving frequency selectivity, reducing frequency deviation, optimizing impedance matching, and suppressing parasitic modes.

[0104] Optionally, the number of fingers of the reflection grating in each parallel resonator 111 can be set to be different from each other, and along the series path from the input terminal In to the output terminal Out, the number of fingers of the reflection grating in each parallel resonator 111 increases sequentially. In this way, the reflection intensity and impedance distribution can be regulated by spatial gradient, and various effects such as enhanced out-of-band suppression, optimized passband ripple, and suppressed parasitic effects can be achieved. Further, along the series path, the sequential increase in the number of fingers of the reflection grating in each parallel resonator 111 can form a complement with the sequential decrease in the number of fingers of the reflection grating in each series resonator 110, enabling higher suppression, lower insertion loss, and a wider frequency band.

[0105] Based on the above embodiments, in another embodiment of the present application, it can also be as Figure 7 shown, setting the filter circuit topology includes at least one of the following ways: the input terminal In is grounded based on the first inductor A_Lp; the output terminal Out is grounded based on the second inductor L1_Lp; at least one parallel resonator 111 is grounded based on the third inductor L1_L1.

[0106] If the input terminal In is grounded through the first inductor A_Lp, a zero potential can be provided at the input terminal In through the first inductor A_Lp, enabling optimization of the impedance matching at the input terminal In, reducing signal reflection, and improving signal transmission efficiency.

[0107] If the output terminal Out is grounded through the second inductor L1_Lp, a zero potential can be provided at the output terminal Out through the second inductor L1_Lp, enabling load-end impedance matching at the output terminal Out, reducing insertion loss, and suppressing out-of-band spurious signals at the output terminal Out to prevent their radiation or interference with other RF links.

[0108] If the parallel resonator 111 is grounded through the third inductor L1_L1, one end of the parallel resonator 111 is connected between two adjacent series resonators 110, and the other end is grounded through the third inductor L1_L1. In this way, precise frequency control and spurious suppression of the parallel resonator 111 can be achieved.

[0109] In one implementation, a part of the parallel resonators 111 can be grounded based on the third inductor L1_L1, and another part of the parallel resonators 111 can be directly grounded.

[0110] When multiple parallel resonators 111 are grounded based on the third inductor L1_L1, in order to save the number of inductors and versions, as Figure 7 shown, it can be set that these multiple parallel resonators 111 are grounded using the same third inductor L1_L1.

[0111] In other ways, it can also be set that each parallel resonator 111 is grounded through a separate third inductor L1_L1 respectively.

[0112] From the above description, it can be seen that in the embodiments of the present application, by optimizing the number of fingers of the reflection grating in the series resonator 110, the influence of the small ripples below the series resonance frequency in the series resonator 110 on the passband shape of the filter can be effectively weakened.

[0113] Next, taking the Figure 7 shown GPS L1 filter as an example, through specific experimental data, the effect that the embodiments of the present application can optimize the number of fingers of the reflection grating in the series resonator 110 to improve the shape and loss on the left side of the passband in the filter will be further described.

[0114] Referring to Figure 10 , Figure 10 is Figure 7 the real part of the admittance curve graph when the number of fingers of the reflection grating in each series resonator in the shown filter circuit topology is not optimized. Figure 10 In it, the horizontal axis is frequency / GHz, and the vertical axis is the real part of the admittance / dB. Figure 10 The five curves in it respectively correspond to Figure 7 the real part of the admittance curve of a series resonator 110 in

[0115] Based on Figure 10 it can be known that within the area shown by the dotted box, the real parts of the admittances of the first series resonator s1 to the fifth series resonator s5 all have more or less small ripples near the left sideband 1.559Ghz shown by the vertical line m27, resulting in a collapse on the left side of the passband of the filter, thereby deteriorating the shape and loss on the left side of the filter passband. And because the coverage range of the small ripples of each series resonator 110 is relatively wide, it is impossible to move this area out of the passband by moving the frequencies of all series resonators.

[0116] To solve Figure 10Regarding the problems existing in the shown manner, the technical solution of the embodiment of the present application can be used to optimize the number of fingers of the reflection grating in some or all of the series resonators 110. By reducing the number of fingers of the reflection grating in the series resonator 110, the reflection grating in the series resonator 110 uses a smaller number of fingers to weaken the ripple intensity of the series resonator 110 below the series resonance frequency, thereby improving the shape and loss on the left side of the filter passband.

[0117] In the filter, when the number of fingers of the reflection grating in the same series resonator 110 is successively B = 10, B = 20, B = 30, B = 40, and B = 50, the real part of the admittance curves of the first series resonator s1 to the fifth series resonator s5 are as follows Figures 11 - 20 shown. Figures 11 - 20 In it, the horizontal axis is the frequency / GHz, and the vertical axis is the real part of the admittance / dB.

[0118] Refer to Figure 11 and Figure 12 , Figure 11 is Figure 7 the real part of the admittance curve of the first series resonator s1 in the filter circuit topology shown, Figure 12 is Figure 11 the partial enlarged view of the real part of the admittance curve shown. Based on Figure 11 and Figure 12 shown, it can be seen that when B = 10, the ripple amplitude of the first series resonator s1 below the series resonance frequency is the smallest.

[0119] Refer to Figure 13 and Figure 14 , Figure 13 is Figure 7 the real part of the admittance curve of the second series resonator s2 in the filter circuit topology shown, Figure 14 is Figure 13 the partial enlarged view of the real part of the admittance curve shown. Based on Figure 13 and Figure 14 shown, it can be seen that when B = 10, the ripple amplitude of the second series resonator s2 below the series resonance frequency is the smallest.

[0120] Refer to Figure 15 and Figure 16 , Figure 15 is Figure 7 the real part of the admittance curve of the third series resonator s3 in the filter circuit topology shown, Figure 16 is Figure 15 the partial enlarged view of the real part of the admittance curve shown. Based on Figure 15 and Figure 16 shown, it can be seen that when B = 10, the ripple amplitude of the third series resonator s3 below the series resonance frequency is the smallest.

[0121] Reference Figure 17 and Figure 18 , Figure 17 is Figure 7 the real part curve graph of the admittance of the 4th series resonator s4 in the filter circuit topology shown, Figure 18 is Figure 17 a partial enlarged view of the real part curve graph shown. Based on Figure 17 and Figure 18 shown, when B = 10, the ripple amplitude of the 4th series resonator s4 below the series resonance frequency is the smallest.

[0122] Reference Figure 19 and Figure 20 , Figure 19 is Figure 7 the real part curve graph of the admittance of the 5th series resonator s5 in the filter circuit topology shown, Figure 20 is Figure 19 a partial enlarged view of the real part curve graph shown. Based on Figure 19 and Figure 20 shown, when B = 10, the ripple amplitude of the 5th series resonator s5 below the series resonance frequency is the smallest.

[0123] Experimental data shows that when the number of fingers of the reflection grating in each series resonator 110 is reduced to 10, it does not significantly deteriorate the Q value Qs of the resonator at the series resonance frequency, and slightly reduces the Q value Qp of the resonator at the parallel resonance frequency. Since the Qs of the series resonator 110 affects the passband insertion loss of the filter, and Qp affects the out-of-band rejection of the filter, and at the same time, the Qp of the parallel resonator 111 also affects the passband insertion loss of the filter. Based on this, in the embodiments of the present application, by making the series resonator 110 have a smaller number of reflection grating fingers and making the parallel resonator 111 have a larger number of reflection grating fingers, the series resonator 110 and the parallel resonator 111 can form a complementary effect.

[0124] In the filter, when the number of fingers of the reflection grating in the same parallel resonator 111 is successively A = 10 and A = 50, the real part curve graphs of the admittance of the 1st parallel resonator p1 to the 4th parallel resonator p4 are as Figures 21 - 24 shown. Figures 21 - 24 Among them, the horizontal axis is frequency / GHz, and the vertical axis is the real part of admittance / dB.

[0125] Reference Figures 21 - 24 , Figure 21 is Figure 7 the real part curve graph of the admittance of the 1st parallel resonator p1 in the filter circuit topology shown, Figure 22 is Figure 7 the real part curve graph of the admittance of the 2nd parallel resonator p2 in the filter circuit topology shown,Figure 23 The Figure 7 real part of the admittance curve of the third parallel resonator p3 in the filter circuit topology shown Figure 24 is Figure 7 the real part of the admittance curve of the fourth parallel resonator p4 in the filter circuit topology shown

[0126] Based on Figures 21 - 24 it can be seen that for the same parallel resonator 110, as shown in the real part of the admittance curves corresponding to A = 10 and A = 50 respectively, when the number of fingers of the reflection grating in the series resonator 110 is 10, setting the number of fingers of the reflection grating in the parallel resonator 111 to 50 can increase the Qp of the parallel resonator 111 and weaken the deterioration of the right side of the filter passband due to the series resonator 110

[0127] Based on the above experimental data, in the embodiments of the present application, when the series resonator 110 uses a smaller number of fingers of the reflection grating (such as the number of fingers in the reflection grating is 10) and the parallel resonator 111 uses a larger number of fingers of the reflection grating (such as the number of fingers in the reflection grating is 50), the filter has better performance

[0128] Refer to Figure 25 , Figure 25 which is the passband curve of the filter circuit topology Figure 25 In Figure 25 the horizontal axis is frequency, with the unit of GHz, and the vertical axis is signal power, with the unit of dB. The first curve 112 in

[0129] is the passband curve of the filter circuit topology after optimizing the number of fingers of the reflection grating based on the embodiments of the present application, and the second curve 113 is the passband curve of the conventional filter circuit topology without optimizing the number of fingers of the reflection grating Figure 25 In the manner shown

[0130] Based on Figure 25As shown by the passband curve between the two vertical lines on the left side in [reference], there is a significant collapse in the second curve 113 within the area shown between the two vertical lines, while the first curve 112 is relatively smooth and full within the area shown between the two vertical lines. Therefore, based on the technical solution of the embodiment of the present application, the problem of passband curve collapse of the conventional filter in this area can be solved, the loss can be increased by about 0.3 dB, and at the same time, the loss of the right sideband of the passband hardly deteriorates.

[0131] Reference Figure 26 , Figure 26 is Figure 25 the comparison chart of out-of-band rejection and steepness curves of two filter circuit topologies in [reference]. Figure 26 In [reference], the horizontal axis is frequency / GHz, and the vertical axis is signal power / dB. Based on Figure 26 it can be known that the test curves of the filter circuit topology with optimized number of reflection fingers based on the embodiment of the present application and the conventional filter circuit topology without optimizing the number of reflection gate fingers are approximately completely coincident. Therefore, while improving the shape and loss of the left side of the filter passband through the technical solution of the embodiment of the present application, the out-of-band rejection will not deteriorate.

[0132] Based on the above embodiments, another embodiment of the present application further provides a radio frequency module, and the radio frequency module includes the filter circuit topology provided by any one of the above embodiments.

[0133] Based on the above embodiments, another embodiment of the present application further provides an electronic device, and the electronic device includes the above radio frequency module.

[0134] The radio frequency module and the electronic device disclosed in the embodiments of the present application have the same or corresponding beneficial effects as the filter circuit topology disclosed in the above embodiments. To avoid repetition, they will not be described in detail here.

[0135] The various embodiments in the specification of the present application are described in a progressive, or parallel, or a combination of progressive and parallel manners. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. The embodiments provided by the embodiments of the present application can be combined with each other without conflict.

[0136] It should be noted that in the description of the present application, it should be understood that the descriptions of the drawings and embodiments are illustrative rather than restrictive. The same reference numerals throughout the embodiments of the specification identify the same structures. Additionally, for the sake of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. At the same time, it can be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element can be directly on the other element or there may be intermediate elements. Additionally, "on" means positioning the element on or below another element, but does not inherently mean positioning on the upper side of another element according to the direction of gravity.

[0137] The orientation or positional relationship indicated by terms such as "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be intermediate components present at the same time.

[0138] It should also be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including", or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the article or device including the above elements.

[0139] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A filter circuit topology, characterized in that, Comprising: An input end and an output end; A plurality of series resonators, which are sequentially connected between the input end and the output end; A plurality of parallel resonators, and adjacent two of the series resonators are grounded respectively based on one of the parallel resonators; Wherein, the series resonators and the parallel resonators are both surface acoustic wave resonators with reflection gratings; the number of finger bars of the interdigital electrodes in each of the surface acoustic wave resonators is the same; the number of finger bars of the reflection grating in the series resonator is less than the number of finger bars of the reflection grating in the parallel resonator.

2. The filter circuit topology according to claim 1, wherein, The number of finger bars of the reflection grating in the series resonator does not exceed A, and the number of finger bars of the reflection grating in at least part of the series resonators is less than A; Wherein, A is the minimum value of the number of finger bars of the reflection grating in each of the parallel resonators.

3. The filter circuit topology according to claim 2, wherein The number of finger bars of the reflection grating in each of the series resonators is less than A.

4. The filter circuit topology according to claim 3, characterized in that, The number of finger bars of the reflection grating in each of the series resonators is B, and B is a positive integer less than A.

5. The filter circuit topology according to claim 1, characterized in that, The number of finger bars of the reflection grating in at least two of the series resonators is different.

6. The filter circuit topology according to claim 5, wherein, If the number of finger bars of the reflection grating in two of the series resonators is different, then the number of finger bars of the reflection grating in the one closer to the output end is C, and the number of finger bars of the reflection grating in the one farther from the output end is D, wherein, both C and D are positive integers not exceeding A, and C is less than D.

7. The filter circuit topology according to any one of claims 2-6, characterized in that, The number of finger bars of the reflection grating in the parallel resonator is the same.

8. The filter circuit topology according to any one of claims 2-6, characterized in that, The number of finger bars of the reflection grating in at least two of the parallel resonators is different.

9. The filter circuit topology according to claim 8, wherein, If the number of finger bars of the reflection grating in two of the parallel resonators is different, then the number of finger bars of the reflection grating in the one closer to the output end is E, and the number of finger bars of the reflection grating in the one farther from the output end is F, wherein, both E and F are positive integers not less than A, and E is greater than F.

10. The filter circuit topology according to any one of claims 1-6, characterized in that, At least including one of the following ways: The input end is grounded based on a first inductor; The output end is grounded based on a second inductor; At least one of the parallel resonators is grounded based on a third inductor.

11. A radio frequency module, characterized in that, Including the filter circuit topology structure according to any one of claims 1-10.

12. An electronic device, characterized in that, Including the radio frequency module according to claim 11.

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