Dual-mode acoustic wave filter based on surface acoustic wave and filtering device
By introducing a cubic power function-varying interdigitated spacing into the DMS filter, the problem of insufficient performance of traditional DMS filters in the high-frequency band is solved, achieving bandwidth expansion and insertion loss reduction, and enhancing the tuning freedom and applicability of the filter.
Patent Information
- Application Number
- CN202511460996.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-14
- Publication Date
- 2026-02-24
AI Technical Summary
Traditional DMS filters have a simple IDT structure and fixed interdigitation spacing, which makes it difficult to meet the multiple performance balance requirements of high-performance RF filters in the high-frequency band, such as low insertion loss, wide bandwidth and high rejection ratio.
A dual-mode acoustic wave filter based on surface acoustic waves is adopted. By setting a main spacing region and an adjustable spacing region in the spacing range of the IDT, the interdigital spacing changes monotonically in the form of a cubic power function, which enhances the degree of freedom of adjustment, constructs multiple resonant modes, and optimizes the insertion loss and standing wave ratio.
It achieves bandwidth expansion, reduces insertion loss, enhances device tuning freedom, and improves the applicability and performance of the filter, especially showing better in-passband insertion loss and out-of-band rejection performance in the B40 band.
Smart Images
Figure CN121567095A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of filter technology, and in particular to a dual-mode acoustic wave (DAW, DMS) filter and filtering device based on surface acoustic waves. Background Technology
[0002] With the evolution from 5G to 6G mobile communication technology, spectrum resources are becoming increasingly scarce, leading to a significant increase in the demand for diverse bandwidth filters in high-frequency bands. Traditional RF filters struggle to achieve a balance between low insertion loss, wide bandwidth, and high rejection ratio at high frequencies. As a filter based on surface acoustic wave (SAW) technology, the DMS filter, with its dual-mode resonant characteristics, has become a key component for improving filtering performance. Its basic structure consists of multiple interdigital transducers (IDTs) and reflectors. However, existing DMS filters generally suffer from problems such as a single IDT structure and fixed interdigital spacing, making it difficult to meet the requirements of high-performance RF filters. Summary of the Invention
[0003] Therefore, it is necessary to provide a surface acoustic wave-based dual-mode acoustic wave filter and filtering device that can improve the applicability of the above problems, so as to enhance the bandwidth expansion capability, reduce insertion loss, and enhance the tuning freedom of the device.
[0004] The first aspect of this application provides a dual-mode acoustic wave filter based on surface acoustic waves (SAWs), including reflectors and multiple independent traditional acoustic layers (IDTs) disposed between the reflectors, each IDT arranged along the propagation direction of the SAWs; each IDT includes multiple spacing intervals, and each spacing interval is provided with interdigitated fingers arranged along the propagation direction of the SAWs and connected end to end in sequence; wherein, each spacing interval of the IDT includes a main spacing region and several adjustable spacing regions, the spacing of the interdigitated fingers in the main spacing region is consistent, and the spacing of adjacent interdigitated fingers in each of the adjustable spacing regions varies monotonically in the direction away from the main spacing region in the form of a cubic power function, and the variation amplitude of the spacing of adjacent interdigitated fingers in different adjustable spacing regions is different.
[0005] In one embodiment, each of the adjustment spacing zones decreases monotonically with a spacing variation of a power of three, the variation of which satisfies a nonlinear function, and the nonlinear function is a cubic function with continuous first derivative.
[0006] In one embodiment, the IDT includes a first IDT, a second IDT, a third IDT, a fourth IDT, and a fifth IDT arranged along the propagation direction of the surface acoustic wave. The first IDT, the third IDT, and the fifth IDT are all connected to the input terminal, and the second IDT and the fourth IDT are both connected to the output terminal.
[0007] In one embodiment, the second IDT, the third IDT, and the fourth IDT all include a main spacing region, an adjustment spacing region one, and an adjustment spacing region two. In the second IDT, the third IDT, and the fourth IDT, the main spacing region is located between the adjustment spacing region one and the adjustment spacing region two. The spacing variation range of each adjacent interdigitated finger within the adjustment spacing region one and the adjustment spacing region two is different from each other, and the entire IDT is centrally symmetrical with respect to the main spacing region. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region one and the adjustment spacing region two are the same or different in different IDTs.
[0008] In one embodiment, both the first IDT and the fifth IDT include a main spacing region and an adjustment spacing region 1. In the first IDT and the fifth IDT, the spacing variation range of each adjacent interdigitated finger in the adjustment spacing region 1 is different, and the main spacing region is located between the adjustment spacing region 1 and the corresponding reflector. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region 1 are the same or different in different IDTs.
[0009] In one embodiment, in the second IDT, the third IDT, or the fourth IDT, the spacing between adjacent interdigitates in the first and second adjustment spacing regions decreases monotonically in the form of a cubic power function along the direction away from the main spacing region, and the amplitude of the interdigitate spacing change gradually increases.
[0010] In one embodiment, in the first IDT or the fifth IDT, the spacing between adjacent interdigitates in the first adjustment spacing region decreases monotonically in the form of a cubic power function along the direction away from the main spacing region, and the change amplitude of the interdigitate spacing gradually increases.
[0011] In one embodiment, the number of interdigitated fingers is the same in each of the said adjustment spacing regions.
[0012] In one embodiment, the spacing between adjacent interdigitated fingers and the magnitude of spacing change in each of the adjustable spacing zones are different.
[0013] A second aspect of this application provides a filtering device, including a trapezoidal filter and the aforementioned filter.
[0014] The aforementioned dual-mode acoustic wave filter and filtering device based on surface acoustic waves (SAWs) includes multiple spacing intervals in each individual independent transducer (IDT). Each spacing interval is equipped with interdigitated fingers arranged sequentially end-to-end along the propagation direction of SAWs. Each IDT spacing interval includes a main spacing region and several adjustable spacing regions. The spacing of the interdigitated fingers in the main spacing region is consistent. In each adjustable spacing region, the spacing between adjacent interdigitated fingers changes monotonically away from the main spacing region in the form of a cubic power function, and the magnitude of the change in spacing between adjacent interdigitated fingers differs in different adjustable spacing regions. By adjusting the spacing of each interdigitated finger individually, the design freedom is significantly improved, multiple resonant modes are constructed within the passband, enhancing bandwidth expansion capability, reducing insertion loss, and increasing the tuning freedom of the device to adapt to different application scenarios, thus expanding its applicability. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure of a dual-mode acoustic filter based on surface acoustic waves in one embodiment;
[0016] Figure 2 This is a schematic diagram of the IDT structure distribution in one embodiment;
[0017] Figure 3 This is a schematic diagram of the interdigitated structure of the third IDT in one embodiment;
[0018] Figure 4 This is a schematic diagram of the interdigitated structure of the fifth IDT in one embodiment;
[0019] Figure 5 This is a diagram showing the overall interdigital spacing distribution of the IDT in one embodiment;
[0020] Figure 6 This is a diagram showing the interdigital spacing distribution of the third IDT in one embodiment;
[0021] Figure 7 This is a diagram showing the interdigital spacing distribution of the fifth IDT in one embodiment;
[0022] Figures 8 to 15 This is a comparison chart of the effects of this application and linear weighted adjustment of interdigital spacing. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0025] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.
[0026] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, operations, components, parts, or combinations thereof.
[0027] In traditional designs, the core structure of a DMS filter consists of multiple interdigital transducers (IDTs), with the interdigital spacing (i.e., the distance between adjacent electrodes, called the pitch size) of these IDTs typically constant. The interdigital spacing directly determines the resonant frequency of the IDT, which is determined by the physical characteristics of matching the wavelength of the surface acoustic wave (SAW) with the electrode spacing. The spacing between two adjacent IDTs affects the coupling strength and mode distribution of the SAW, thereby adjusting the frequency response characteristics within the passband. However, this traditional design is limited in its degree of freedom. Since the pitch of each IDT is fixed, a single IDT can only produce a specific resonant frequency, and the adjustment range of the gap between adjacent IDTs is limited. The limited number of independently adjustable parameters (such as pitch and gap) restricts the number of achievable resonant modes. This limitation makes it difficult for traditional DMS filters to meet the stringent requirements of high out-of-band rejection, low insertion loss, and wide bandwidth in high-performance applications.
[0028] The core performance indicators of surface acoustic wave (SAW) filters mainly focus on three key factors: insertion loss (IL), voltage standing wave ratio (VSWR), and out-of-band rejection (ROR). Insertion loss is a crucial parameter measuring the power loss of a signal passing through the filter. It is typically defined as the difference in decibels of the received power at the load before and after the filter insertion. Its value directly affects the signal transmission efficiency of the system and therefore needs to be strictly controlled within the filter's operating bandwidth. VSWR reflects the impedance matching degree between the filter and the transmission system, characterized as the ratio of the voltage at the antinode to the voltage at the node in the transmission line. In engineering, a VSWR of less than 1.5 is usually required to reduce the impact of signal reflection on system stability. ROR reflects the filter's ability to attenuate interference signals outside the operating frequency band. Its performance is in conflict with insertion loss; excessively high ROR may exacerbate insertion loss, while low ROR may reduce anti-interference capability. Therefore, a balance must be achieved by optimizing the transducer structure, material properties, and electrode design. These three indicators together determine the filter's frequency selectivity, signal integrity, and adaptability to practical application scenarios.
[0029] Based on this, this application proposes an improved scheme for a double-mode surface acoustic wave (DMS) filter. By breaking through traditional design constraints, the DMS filter topology optimization method based on the gradually varying interdigitated spacing is adopted. Through innovative structural design, the performance limitations of the traditional DMS filter are overcome, effectively improving the degree of design freedom. Multiple resonant modes are constructed in the passband, achieving core performance improvements such as reduced insertion loss, optimized standing wave ratio, and expanded bandwidth.
[0030] In one embodiment, such as Figure 1 As shown, a dual-mode acoustic wave filter based on surface acoustic waves is provided, including reflectors 110 and multiple independent traditional acoustic transformers (IDTs) 120 disposed between the reflectors 110. Each IDT 120 is arranged along the propagation direction of the surface acoustic wave. Each IDT 120 includes multiple spacing intervals, and each spacing interval is provided with interdigitated fingers arranged along the propagation direction of the surface acoustic wave and connected end to end in sequence. The spacing interval of each IDT includes a main spacing interval and several adjustable spacing intervals. The spacing of the interdigitated fingers in the main spacing interval is consistent. The spacing between adjacent interdigitated fingers in each adjustable spacing interval changes monotonically in the direction away from the main spacing interval in the form of a cubic power function, and the change amplitude of the spacing between adjacent interdigitated fingers in different adjustable spacing intervals is different.
[0031] In the main spacing region, the spacing between the interdigitated fingers is consistent, specifically meaning the spacing between the interdigitated fingers is the same. The number of IDT 120s is not unique; in this embodiment, for example... Figure 1 and Figure 2As shown, there are five IDTs 120, arranged between a pair of reflectors 110 along the propagation direction of the surface acoustic wave. They are named sequentially from one reflector 110 to the other: First IDT, Second IDT, Third IDT, Fourth IDT, and Fifth IDT. The First IDT, Third IDT, and Fifth IDT are all connected to input terminal 1, while the Second IDT and Fourth IDT are both connected to output terminal 2. In each IDT 120, interdigitated fingers are arranged along the propagation direction of the surface acoustic wave and connected end-to-end. The spacing between some interdigitated fingers remains constant, defined as the main spacing region. Adjustable spacing regions are provided on either side or one side of the main spacing region. The two outer IDTs (First IDT and Fifth IDT) have two spacing intervals, including one main spacing region and one adjustable spacing region. The three middle IDTs (Second IDT, Third IDT, and Fourth IDT) have three spacing intervals, including one main spacing region and two adjustable spacing regions, with the two adjustable spacing regions symmetrically arranged relative to the main spacing interval. The reflector 110 can be constructed using a reflective grating, such as... Figure 1 As shown, the black part is the reflective grating, the red part is the main spacing area, and the blue part is the adjustable spacing area.
[0032] In the adjustable spacing region, the spacing between adjacent interdigitates is not equal, but changes monotonically with a power-of-cubic-degree variation. The number of interdigitates adjusted and the magnitude of the weighting coefficients both affect the final filter performance. Specifically, in the adjustable spacing region, the spacing between adjacent interdigitates decreases monotonically with a power-of-cubic-degree variation starting from the main spacing region. The variation amplitude in each adjustable spacing region satisfies a nonlinear function, and the nonlinear function is a cubic function with continuous first derivatives, which significantly accelerates the spacing change rate in the high-frequency band. The number of interdigitates in each adjustable spacing region can be the same or different, and the specific value is not unique. For example, the number can be 3 to 5, which can be set according to actual needs. In this embodiment, the number of interdigitates in each adjustable spacing region is the same, for example, 5, to facilitate spacing design.
[0033] In one embodiment, such as Figure 2As shown, the second, third, and fourth IDTs all include a main spacing region, an adjustment spacing region one, and an adjustment spacing region two. In the second, third, and fourth IDTs, the main spacing region is located between adjustment spacing region one and adjustment spacing region two. The spacing variation range of adjacent interdigitated fingers within adjustment spacing region one and adjustment spacing region two is different from each other, and the entire IDT is centrally symmetrical with respect to the main spacing region. The spacing variation patterns of adjacent interdigitated fingers in adjustment spacing region one and adjustment spacing region two are the same or different in different IDTs. Furthermore, the first and fifth IDTs both include a main spacing region and an adjustment spacing region one. In the first and fifth IDTs, the spacing variation range of adjacent interdigitated fingers within adjustment spacing region one is different from each other, and the main spacing region is located between adjustment spacing region one and the corresponding reflector. The spacing variation patterns of adjacent interdigitated fingers in adjustment spacing region one are the same or different in different IDTs.
[0034] like Figure 3 As shown, taking the third IDT as an example, the interdigital spacing in the main spacing region remains constant. Two adjustment spacing regions are defined at each end: Adjustment Spacing Region 1 and Adjustment Spacing Region 2. Each adjustment spacing region adjusts five interdigits. The overall structure of the third IDT is centrally symmetrical. The spacing between adjacent interdigits and the magnitude of their variation in Adjustment Spacing Region 1 and Adjustment Spacing Region 2 are not equal. The spacing variation is monotonically reduced along the direction away from the main spacing region in cubic increments. The variation magnitude of the adjustment spacing region satisfies a nonlinear function, and its first derivative is continuous, significantly accelerating the rate of spacing change in the high-frequency band. The second and fourth IDTs use the same processing method, and their overall structures are also centrally symmetrical. The spacing variation patterns of adjacent interdigits in Adjustment Spacing Region 1 and Adjustment Spacing Region 2 can be the same as or different from those in the third IDT. The number of interdigits adjusted and the magnitude of their variation both affect the final filter performance.
[0035] like Figure 4 As shown, taking the fifth IDT as an example, the interdigital spacing in the main spacing region remains constant, and the main spacing region is located between the first adjustment spacing region and the corresponding reflector. The first adjustment spacing region adjusts five interdigits. The spacing between adjacent interdigits in the first adjustment spacing region and the magnitude of the spacing change are not equal. The spacing change magnitude decreases monotonically in a cubic power direction away from the main spacing region. The magnitude of the spacing change in the adjustment spacing region satisfies a nonlinear function, and its first derivative is continuous, significantly accelerating the spacing change rate in the high-frequency band. The first IDT uses the same processing method. The spacing change pattern of adjacent interdigits in the first adjustment spacing region can be the same as or different from that of the fifth IDT. The number of interdigits adjusted and the magnitude of the change will affect the final filter performance.
[0036] Specifically, such as Figure 5As shown, in the second, third, or fourth IDT, the spacing between adjacent interdigitated fingers in adjustment spacing zone one and adjustment spacing zone two decreases monotonically in the form of a cubic power function along the direction away from the main spacing zone, and the amplitude of the interdigitated finger spacing change gradually increases. In this embodiment, for the second, third, and fourth IDT, the spacing between adjacent interdigitated fingers in adjustment spacing zone one and adjustment spacing zone two is designed such that, along the direction away from the main spacing zone, the amplitude of the spacing change gradually increases from the first interdigitated finger to the last interdigitated finger, and the amplitudes of the spacing change in the second, third, and fourth IDTs are different from each other.
[0037] In either the first IDT or the fifth IDT, the spacing between adjacent interdigitates in the first adjustment spacing region decreases monotonically in a cubic power function along the direction away from the main spacing region, and the amplitude of the interdigitate spacing change gradually increases. In this embodiment, for both the first and fifth IDTs, the spacing between adjacent interdigitates in the first adjustment spacing region is designed such that, along the direction away from the main spacing region, the amplitude of the interdigitate spacing change gradually increases from the first interdigitate to the last interdigitate, and the amplitudes of the spacing change in the first and fifth IDTs are different.
[0038] In conclusion, Figure 5 In the DMS filter shown, each IDT has 5 interdigitated fingers in the adjustment spacing region. All interdigitated fingers in the adjustment spacing region are adjusted using non-uniform cubic power transform Delta adjustment, replacing the traditional uniform Delta adjustment.
[0039] Figure 6 In the third IDT shown, the entire structure is centrally symmetrical. The interdigital spacing in the main spacing region remains constant. The first and second adjustment spacing regions on the left and right sides each have 5 interdigits. Each interdigit decreases monotonically with a power-law Delta, which means that the interdigital spacing decreases rapidly from the main spacing region in the form of a power-law function. Figure 7 In the fifth IDT shown, the interdigital spacing in the main spacing region remains constant, while the adjustment spacing region on the left has 5 interdigits. Each interdigit decreases monotonically with a power-law Delta, which means that the interdigital spacing decreases rapidly from the main spacing region in the form of a power-law function.
[0040] It is understood that in other embodiments, the second IDT, the third IDT, and the fourth IDT may also be designed as Figure 5 Other variations only require that the interdigitation distance between the two sides of the adjustment spacing zone in each IDT varies in a cubic power form, and that the overall structure is centrally symmetrical. The first and fifth IDTs can also be designed as follows: Figure 5Other variations only require that the interdigitation distance in the adjustment spacing region of each IDT changes in a cubic power form. To further improve the optimization freedom, the interdigitation distance between adjacent interdigitations and the magnitude of the distance change in each adjustment spacing region of the five IDTs can be different.
[0041] The DMS filter provided in this application introduces a Delta variable representing the magnitude of the cubic spacing variation, dividing the IDT of the DMS filter into multiple interdigital spacings. The variation of the period introduces more resonant points, giving more freedom to optimize the results. At the same time, the nonlinear cubic variation avoids the problem of excessive optimization time caused by too many optimization parameters.
[0042] Current linear weighted interdigitation methods adjust the interdigitation spacing by monotonically and uniformly decreasing the spacing amplitude Delta of each interdigitation in the adjustment region. Compared with the linear weighted method, the DMS filter provided in this application achieves a smoother overall image with cubic transform Delta adjustment, offering greater optimization freedom and better optimization results. The comparison results are as follows: Figures 8 to 15 The blue line represents the result of the cubic power function spacing transformation adjustment in this application, and the red line represents the result of the single linear weighted adjustment. Figure 8 This is a comparison chart of insertion loss. Figure 9 This is a comparison chart of local insertion loss within the passband. Figure 10 This is a comparison image of out-of-band suppression on the left side. Figure 11 This is a comparison image of out-of-band suppression on the right side. Figure 12 This is a comparison chart of return loss. Figure 13 This is a comparison chart of VSWR1. Figure 14 This is a comparison chart of VSWR2. Figure 15 This is a comparison diagram of ripple within the passband.
[0043] like Figure 8 As shown, the blue line represents the result of adjusting the spacing using a cubic power function, while the red line represents the result of adjusting using the existing single-linear weighted method. The comparison reveals that the blue line shows a smoother overall image, with a significant improvement in out-of-band suppression on the left side. This indicates that the filter effectively suppresses unwanted frequency components, thus enhancing its selectivity for the passband signal. While the out-of-band suppression on the right side shows no significant improvement, it still meets the design requirements. Figure 9As shown, the blue line represents the result of the cubic power function spacing transformation adjustment, and the red line represents the result of the existing single-linear weighted adjustment. The parameters for m7 are: freg = 2.300 GHz, dB(S(2,1)) = -1.180, dB(Cube_delta_4_5..S(2,1)) = -1.072; the parameters for m8 are: freg = 2.400 GHz, dB(S(2,1)) = -1.062, dB(Cube_delta_4_5..S(2,1)) = -1.064. The comparison shows that using the cubic power function Delta adjustment significantly improves the overall insertion loss on the left side of the passband, by approximately 0.1 dB, while the insertion loss on the right side of the passband remains relatively unchanged. This improvement in insertion loss within the passband means that the filter attenuates the signal less within the passband, allowing more signal to be transmitted effectively.
[0044] like Figure 10 As shown, the blue line represents the result of adjusting the spacing using a cubic power function, while the red line represents the result of adjusting using the existing linear weighting method. The comparison reveals that the left-side out-of-band rejection (OBS) achieved using the cubic power function spacing adjustment is significantly better than that achieved using the existing linear weighting method, with an improvement of approximately 5-7 dB. This improved left-side OBS means the filter can more effectively suppress low-frequency interference signals. Figure 11 As shown, the blue line represents the result of the cubic power function spacing transformation adjustment, and the red line represents the result of the existing single linear weighted adjustment. By comparison, it can be seen that the out-of-band suppression on the right side has no significant change, and the results of the two methods are not much different. Although there is no significant improvement, it still meets the design requirements.
[0045] like Figure 12 As shown, the blue line represents the result of cubic power function spacing transformation adjustment, while the red line represents the result of the existing single-linear weighted adjustment. The comparison reveals that cubic power function spacing transformation adjustment significantly improves overall return loss within the passband, especially in the 2300-2330MHz range. Higher return loss indicates better impedance matching, enabling effective signal transmission without reflection, reducing power loss, and improving transmission efficiency. Figure 13 , Figure 14 As shown, the blue line represents the result of the cubic power function spacing transformation adjustment, while the red line represents the result of the existing single linear weighted adjustment. The cubic power function spacing transformation adjustment reduces the VSWR in the passband to below 1.5dB, especially in the 2300 to 320MHz range, showing a significant improvement compared to the result of single linear weighted adjustment. When the VSWR drops below 1.5, it means that the impedance matching of the RF system is good, the signal transmission efficiency is high, the energy loss is small, and the equipment is more stable and reliable.
[0046] Depend on Figure 15As shown, the blue line represents the result of the cubic power function spacing transformation adjustment, and the red line represents the result of the existing single linear weighted adjustment. The parameters of m9 are: freq = 2.300 GHz, dB(S(2.1)) = -1.180, optlter = 143; the parameters of m10 are: freg = 2.300 GHz, dB(Cube_delta_4_5..S(2.1)) = -1.072, optlter = 136; the parameters of m12 are: freq = 2.371 GHz, dB(Cube_delta_4_5..S(2.1)) = -0.675, optlter = 136Peak; the parameters of m13 are: freg = 2.370 GHz1, dB(S(2.1)) = -0.661, optlter = 143Peak. By using a cubic power function spacing transformation to adjust the passband ripple, the signal amplitude within the passband becomes more stable, the filter gain response becomes flatter, and the signal quality becomes higher.
[0047] As can be seen from the above comparison, this application achieves the goal of reducing insertion loss without reducing out-of-band suppression.
[0048] In one embodiment, a filtering device is also provided, including a trapezoidal filter and the aforementioned dual-mode acoustic wave filter based on surface acoustic waves. The dual-mode acoustic wave filter has five interdigitated fingers in each adjustment interval region.
[0049] Furthermore, the filtering device is a B40 band (2300–2400 MHz) filter. The B40 band, as a supplementary indoor band in operator applications, is an important band used in time-division multiplexing (TDD) technology in mobile communications. For commercial filters, the B40 band offers an improvement of nearly 0.1 dB in left-side insertion loss within the passband and a 0.1 dB reduction in ripple within the passband, resulting in better overall performance. This significantly enhances the competitiveness of commercial filters and provides more design margin when considering out-of-band rejection and insertion loss in subsequent designs.
[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0051] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A dual-mode acoustic wave filter based on surface acoustic waves, characterized in that, The system includes reflectors and multiple independent acoustic transducers (IDTs) disposed between the reflectors, each IDT arranged along the propagation direction of the surface acoustic wave. Each IDT includes multiple spacing intervals, and each spacing interval is provided with interdigitated fingers arranged along the propagation direction of the surface acoustic wave and connected end to end in sequence. The spacing interval of each IDT includes a main spacing region and several adjustable spacing regions. The spacing of the interdigitated fingers in the main spacing region is consistent, and the spacing of adjacent interdigitated fingers in each of the adjustable spacing regions changes monotonically in the direction away from the main spacing region in the form of a cubic power function. The change in the spacing of adjacent interdigitated fingers in different adjustable spacing regions has different amplitudes.
2. The filter according to claim 1, characterized in that, Each of the adjustment intervals decreases monotonically with a spacing variation of a power of three, the variation of which satisfies a nonlinear function, and the nonlinear function is a cubic function with continuous first derivative.
3. The filter according to claim 2, characterized in that, The IDT includes a first IDT, a second IDT, a third IDT, a fourth IDT, and a fifth IDT arranged along the propagation direction of the surface acoustic wave. The first IDT, the third IDT, and the fifth IDT are all connected to the input terminal, and the second IDT and the fourth IDT are all connected to the output terminal.
4. The filter according to claim 3, characterized in that, The second IDT, the third IDT, and the fourth IDT all include a main spacing region, an adjustment spacing region one, and an adjustment spacing region two. In the second IDT, the third IDT, and the fourth IDT, the main spacing region is located between the adjustment spacing region one and the adjustment spacing region two. The spacing variation range of each adjacent interdigitated finger within the adjustment spacing region one and the adjustment spacing region two is different from each other, and the entire IDT is centrally symmetrical with respect to the main spacing region. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region one and the adjustment spacing region two are the same or different in different IDTs.
5. The filter according to claim 4, characterized in that, Both the first IDT and the fifth IDT include a main spacing region and an adjustment spacing region 1. In the first IDT and the fifth IDT, the spacing variation range of each adjacent interdigitated finger in the adjustment spacing region 1 is different from each other, and the main spacing region is located between the adjustment spacing region 1 and the corresponding reflector. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region 1 are the same or different in different IDTs.
6. The filter according to claim 5, characterized in that, In the second IDT, the third IDT, or the fourth IDT, the spacing between adjacent interdigitates in the first and second adjustment spacing regions decreases monotonically in the form of a cubic power function along the direction away from the main spacing region, and the amplitude of the change in interdigitate spacing gradually increases.
7. The filter according to claim 5, characterized in that, In the first IDT or the fifth IDT, the spacing between adjacent interdigitates in the first adjustment spacing region decreases monotonically in the form of a cubic power function along the direction away from the main spacing region, and the change amplitude of the interdigitate spacing gradually increases.
8. The filter according to any one of claims 1 to 7, characterized in that, The number of interdigitated fingers is the same in each of the aforementioned adjustment spacing zones.
9. The filter according to any one of claims 1 to 7, characterized in that, The spacing between adjacent interdigitated fingers and the magnitude of spacing change in each of the aforementioned adjustment spacing zones are different.
10. A filtering device, characterized in that, Includes a trapezoidal filter and the filter described in any one of claims 1-9.