DMS type filter and filtering device
By designing multiple IDT main spacing regions and adjustable spacing regions in the DMS filter, and varying the interdigital spacing as a quadratic power function, the problem of the limited applicability of traditional DMS filters is solved, achieving the effects of reducing insertion loss, improving VSWR and expanding bandwidth.
Patent Information
- Application Number
- CN202511460984.6
- 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
In traditional DMS filters, the interdigitation spacing of each IDT is the same, which cannot meet the requirements of next-generation communication technologies for high-performance filters and has a limited scope of application.
By designing multiple IDTs in the DMS filter, and setting a main spacing region and an adjustable spacing region for the spacing between each IDT, the interdigital spacing changes in the form of a quadratic power function. The amplitude of the change in the interdigital spacing between adjacent interdigits in the adjustable spacing region is different, thereby increasing the design freedom.
Significantly reduces insertion loss, improves VSWR, expands bandwidth, adapts to diverse communication needs, and enhances the applicability and performance of the filter.
Smart Images
Figure CN121567094A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of filter technology, and in particular to a DMS type filter and a filtering device. Background Technology
[0002] With the rapid development of next-generation communication technologies (such as 5G and 6G), users' demands for communication speed and network capacity continue to grow, leading to even greater strain on limited communication frequency band resources. At the same time, the bandwidth requirements of different application scenarios are showing a trend of diversification and differentiation. Against this backdrop, surface acoustic wave (SAW) filters, as a key component in communication systems, face higher performance requirements and more complex technical challenges.
[0003] The DMS filter is a high-performance filter based on surface acoustic wave (SAW) technology. Its core structure utilizes interdigital transducers (IDTs) to convert electrical signals into sound waves and achieve lateral propagation. The unique feature of the DMS filter is that it designs reflection structures at the IDT boundaries, causing the sound waves to continuously reflect and select frequencies during propagation, thus achieving excellent filtering performance. In traditional DMS filters, the interdigitation spacing in each IDT is the same, and the number of tunable resonators is quite limited, which cannot meet the high requirements of modern SAW filters and limits its applicability. Summary of the Invention
[0004] Therefore, it is necessary to provide a DMS-type filter and filtering device that can improve the applicability of the above-mentioned problems.
[0005] The first aspect of this application provides a DMS-type filter, including a reflector grating and a plurality of IDTs disposed between the reflector gratings, each IDT being arranged along the propagation direction of surface acoustic waves; each IDT including a plurality of spacing intervals, and each spacing interval being provided with interdigitated fingers arranged along the propagation direction of surface acoustic waves and connected end to end in sequence; wherein, each spacing interval of the IDT includes a main spacing region and a plurality of 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 quadratic power function, and the variation amplitude of the spacing of adjacent interdigitated fingers in different adjustable spacing regions is different.
[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 from each other, and the main spacing region is located between the adjustment spacing region 1 and the corresponding reflective grating. 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 quadratic 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 adjustment spacing region decreases monotonically in the form of a quadratic 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 DMS type filter.
[0014] In one embodiment, the filtering device is a B40 band filtering device.
[0015] The aforementioned DMS-type filter and filtering device each includes multiple spacing intervals in each IDT, and each spacing interval is equipped with interdigitated fingers arranged sequentially end-to-end along the propagation direction of the surface acoustic wave. 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, while the spacing between adjacent interdigitated fingers in each adjustable spacing region changes monotonically away from the main spacing region in the form of a quadratic 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, thereby achieving goals such as reducing insertion loss, improving VSWR, and expanding bandwidth to adapt to different application scenarios and broaden the applicability range. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of a DMS type filter in one embodiment;
[0017] Figure 2 This is a schematic diagram of the IDT structure distribution in one embodiment;
[0018] Figure 3 This is a schematic diagram of the interdigitated structure of the fourth IDT in one embodiment;
[0019] Figure 4 This is a schematic diagram of the interdigitated structure of the first IDT in one embodiment;
[0020] Figure 5 This is a diagram showing the overall interdigital spacing distribution of the IDT in one embodiment;
[0021] Figure 6 This is a diagram showing the interdigital spacing distribution of the fourth IDT in one embodiment;
[0022] Figure 7 This is a diagram showing the interdigitation spacing of the first IDT in one embodiment;
[0023] Figures 8 to 16 The figure shows a comparison of the simulation results of this application and S21 with linear weighted interdigital spacing adjustment for in-band and out-of-band, S1, and VSWR. Detailed Implementation
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] To adapt to higher performance requirements and more complex technical challenges, surface acoustic wave (SAW) filters need technological innovation and optimization in the following aspects: First, the filters need to support wider bandwidths to meet the demands of next-generation communication standards for high frequencies and large bandwidths; second, with the increase in communication frequency bands and the scarcity of spectrum resources, the filters need to have higher frequency selectivity to reduce signal interference and improve communication quality; furthermore, to improve the overall efficiency of the communication system, the filters need to further reduce insertion loss and energy loss during signal transmission; simultaneously, as communication equipment develops towards miniaturization and multi-functionality, the filters need to maintain high performance while further reducing size and supporting integration with other RF components; finally, for different application scenarios (such as high-frequency bands, low-frequency bands, narrowband, broadband, etc.), the filters need to have stronger customization capabilities to meet diverse needs. In practical applications, trapezoidal filters are the most commonly used type of SAW filter due to their good overall performance and low cost, while DMS (Double-mode Surface Acoustic Waves) filters are more often used in high-end applications with extremely high performance requirements.
[0029] However, due to periodic discontinuities at the gaps between different IDTs, some acoustic energy leaks into the substrate material as bulk acoustic waves, leading to increased energy loss and insertion loss. To suppress this energy leakage, DMS filters adjust the periodic structure by controlling the operating frequency below the bulk wave frequency and optimizing the interdigital spacing at the edges of different IDTs, thereby effectively reducing bulk acoustic wave leakage. In traditional DMS filters, the interdigital spacing in each IDT is the same, and the number of tunable resonators is quite limited, which cannot meet the high requirements of modern SAW filters and limits their application range. Based on this, this application proposes a filter design based on dual-mode surface acoustic wave (DMS). By adjusting the interdigital spacing within each interdigital transducer (IDT), the design freedom is significantly improved, thereby achieving the goals of reducing insertion loss, improving VSWR, and expanding bandwidth.
[0030] In one embodiment, such as Figure 1 As shown, a DMS-type filter is provided, including a reflector grating 110 and multiple IDTs 120 disposed between the reflector gratings 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. Among them, the spacing interval of each IDT 120 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 of adjacent interdigitated fingers in each adjustable spacing interval changes monotonically in the direction away from the main spacing interval in the form of a quadratic power function, and the change amplitude of the spacing of 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 2 As 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 a, while the Second IDT and Fourth IDT are both connected to output terminal b. 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. Figure 2 As shown, the purple part is the reflective grating 110, the yellow part is the main spacing area, and the green part is the adjustable spacing area.
[0032] In the adjustment spacing region, the spacing between adjacent interdigitates is not equal, but decreases with the same weighting coefficient. Both the number of interdigitates adjusted and the magnitude of the weighting coefficients affect the final filter performance. Since it uses a monotonically changing quadratic power function, in the adjustment spacing region, the spacing between adjacent interdigitates decreases exponentially starting from the main spacing region. The number of interdigitates in each adjustment 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 adjustment spacing region is the same, for example, 5, to facilitate spacing design.
[0033] In one embodiment, such as Figure 2 As 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 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, 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. 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 each adjacent interdigitated finger within the adjustment spacing region one is different, and the main spacing region is located between the adjustment spacing region one and the corresponding reflective grating 110. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region one are the same or different in different IDTs.
[0034] like Figure 3 As shown, taking the fourth IDT as an example, the interdigital spacing in the main spacing region remains constant. An adjustment spacing region is defined at each end, namely Adjustment Spacing Region 1 and Adjustment Spacing Region 2. Each adjustment spacing region adjusts five interdigits. The overall structure of the fourth 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, varying exponentially along the direction away from the main spacing region. In the second and third IDTs, the overall structure is also centrally symmetrical. The variation pattern of the spacing between adjacent interdigits in Adjustment Spacing Region 1 and Adjustment Spacing Region 2 may be the same as or different from that of the fourth IDT.
[0035] like Figure 4As shown, taking the first IDT as an example, the interdigital spacing in the main spacing region remains constant. The main spacing region is located between the adjustment spacing region one and the corresponding reflective grating 110. The adjustment spacing region one adjusts the five interdigits. The spacing between adjacent interdigits in the adjustment spacing region one, as well as the magnitude of the spacing change, are not equal, changing exponentially along the direction away from the main spacing region. In the fifth IDT, the spacing change pattern of adjacent interdigits in the adjustment spacing region one may be the same as that in the first IDT, or it may be different.
[0036] Specifically, such as Figure 5 As 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 quadratic 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 the form of a quadratic 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 from each other.
[0038] Figure 6 In the fourth 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 interdigital fingers. Each interdigital finger decreases monotonically with the same weighting coefficient, changing in the form of a quadratic power function. This means that the interdigital spacing decreases in the form of a power function starting from the main spacing region, and the amplitude of the spacing change gradually increases. Figure 7 In the first IDT shown, the interdigital spacing in the main spacing region remains constant, while the right-side adjustment spacing region has 5 interdigits. Each interdigit decreases with the same weighting coefficient, changing in the form of a quadratic power function. This manifests as the interdigital spacing decreasing in the form of a power function starting from the main spacing region, with the spacing change amplitude gradually increasing.
[0039] It is understood that in other embodiments, the second IDT, the third IDT, and the fourth IDT may also be designed as Figure 5Other variations only require that the interdigital spacing of the two adjustable spacing zones in each IDT varies exponentially, and that the overall structure is centrally symmetrical. The first and fifth IDTs can also be designed as follows: Figure 5 Other variations only require that the interdigitation distance in the adjustment spacing region of each IDT changes in a power-law manner. 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.
[0040] The DMS-type filter provided in this application divides the IDT of the DMS-type filter into multiple interdigital spacings by using a power-law variation. The period variation introduces more resonant points, giving more freedom to optimize the results. At the same time, the uniform and regular variation avoids the problem of excessive optimization time caused by too many optimization parameters.
[0041] Current linear weighted interdigitation spacing adjustment methods result in each interdigitator in the spacing region decreasing monotonically and uniformly with the same spacing variation amplitude, Delta. Compared to the linear weighted method, the DMS-type filter provided in this application offers better degrees of freedom for optimization and yields better results. The comparison results are as follows: Figures 8 to 16 The blue line represents the simulation results of the DMS-type filter of this application, and the red line represents the simulation results of the linear weighted adjustment method. Figure 8 This is a comparison chart of insertion loss within the passband. Figure 9 This is a comparison chart of local insertion loss within the passband. Figure 10 VSWR1 comparison chart in the range of 2.25GHz to 2.44GHz Figure 11 The chart shows a comparison of VSWR2 in the range of 2.25GHz to 2.44GHz. Figure 12 This is a comparison chart showing the out-of-band suppression on the left side when S21 is less than 2.3 GHz. Figure 13 This is a comparison chart showing the out-of-band suppression on the right side when S21 is greater than 2.4 GHz. Figure 14 This is a comparison image of the overall S21. Figure 15 This is a comparison image of the overall S11. Figure 16 This is a comparison image of the overall S22.
[0042] like Figure 8As shown, the parameters for m7 are: freg = 2.400 GHz, dB(S(2,1)) = -1.083; the parameters for m8 are: freg = 2.400 GHz, dB(secondepowerfinaldelta 45..S(2,1)) = -1.092; the parameters for m6 are: freg = 2.300 GHz, dB(S(2,1)) = -1.229; and the parameters for m5 are: freg = 2.300 GHz, dB(secondepowerfinaldelta 45..S(2,1)) = -1.070. Points m6 and m5 represent the values for exponential and linear weighting at 2.3 GHz, respectively. It is evident that the overall insertion loss within the passband is improved by approximately 0.159 dB, and the overall image within the passband is smoother. Lower insertion loss ensures that signals can be transmitted over long distances while maintaining high quality. For measuring instruments and radar systems, this significantly improves measurement accuracy and target detection capabilities, while reducing the system's noise figure and increasing the signal-to-noise ratio (SNR). Furthermore, low insertion loss also improves system efficiency, reducing the need for additional amplifiers, thereby lowering power consumption and cost.
[0043] like Figure 9 The diagram shows a comparison of local insertion loss within the passband. The data at the two end points of the passband at 2.4GHz and 2.3GHz are as follows: m1: freq = 2.300GHz, dB(secondepowerfinal delta 45..S(2,1)) = -1.070; m3: freq = 2.300GHz, dB(S(2,1)) = -1.229; m2: freq = 2.400GHz, dB(secondepowerfinal delta 45..S(2,1)) = -1.092; m4: freq = 2.400GHz, dB(S(2,1)) = -1.083. The advantages of the DMS filter in this application within the passband are more clearly and intuitively demonstrated by the comparison of the two methods.
[0044] Figure 10 These are two methods for VSWR1 in the range of 2.25GHz to 2.44GHz. The parameters for m9 are: freq = 2.300GHz, VSWR1 = 1.433; the parameters for m10 are: freq = 2.300GHz, secondepowerfinal delta45..VSWR1 = 1.128; and the parameters for m11 are: freg = 2.348GHz, secondepowerfinal delta 45..VSWR1 = 1.459. Figure 11The two methods show VSWR2 in the range of 2.25GHz to 2.44GHz. It can be clearly seen that the VSWR of the DMS filter in this application is reduced to below 1.5 in the passband, which greatly expands the bandwidth.
[0045] Figure 12 The two methods demonstrate left-side out-of-band suppression at S21 less than 2.3 GHz. It is evident that the DMS-type filter of this application exhibits better suppression than the linearly weighted filter, with overall suppression levels below -35 dB. This effectively suppresses low-frequency interference signals, thereby improving the system's anti-interference capability and signal quality, ensuring the purity of the signal within the passband. Furthermore, for multi-band communication or spectrum-sharing systems, stronger left-side suppression can better isolate low-frequency signals, avoid crosstalk between different frequency bands, and improve the overall system's spectrum utilization efficiency. Figure 13 This section describes the out-of-band suppression on the right side of the band at S21 greater than 2.4 GHz using two different methods. A comparison of the out-of-band suppression on the right side reveals that the changes in suppression between the two methods are not very significant. Figure 14 These are two different ways of viewing the overall S21 image.
[0046] Figure 15 These are the overall S11 images for both methods. Within the passband, the blue S11 values are generally lower, indicating that the filter has better impedance matching characteristics within the passband. Therefore, the input signal can be transmitted to the filter more effectively, rather than being reflected back to the source. This efficient signal transmission reduces energy loss, improves the overall system efficiency, and can significantly increase the signal transmission distance and quality. Figure 16 These are the overall S22 values for both methods. The blue line shows a lower overall S22 value, indicating better impedance matching between the filter output port and the load, which minimizes signal reflection at the output port.
[0047] In one embodiment, a filtering device is also provided, including a ladder-type filter and the aforementioned DMS-type filter. In this embodiment, the circuit structure of the filtering device includes a ladder-type filter and a DMS filter containing five IDTs. Simulation design is performed by adjusting the physical parameters of the DMS filter. During the design process, the parameters of the ladder-type structure remain unchanged; only the interdigitation spacing of the IDTs in the DMS filter is adjusted. Specifically, the number of interdigits in each adjustment spacing region of the DMS-type filter is five.
[0048] The main design parameters of surface acoustic wave (SAW) filters include insertion loss, standing wave ratio (VSWR), and out-of-band rejection (OIR). Insertion loss refers to the amount of signal attenuation after passing through the filter; lower insertion loss means less signal loss, thus improving system efficiency. VSWR reflects the impedance matching of the filter within the passband; typically, an OIR below 1.5 is required in the passband to ensure efficient and stable signal transmission. OIR reflects the filter's ability to suppress signals outside the passband; higher OIR means stronger suppression of interference signals. However, OIR and insertion loss are usually mutually restrictive design parameters, requiring a trade-off and optimization between them.
[0049] To optimize the above indicators, this application combines a DMS surface acoustic wave filter and a trapezoidal filter, which can further improve the overall filter performance while meeting the requirements of modern high-performance communication. Figure 2 As shown, the structure of the DMS-type filter consists of five IDTs placed between a pair of reflector gratings 110. These IDTs are arranged sequentially along the propagation direction of the surface acoustic wave and named as the first IDT, second IDT, third IDT, fourth IDT, and fifth IDT from one reflector grating 110 to the other. The DMS-type filter is characterized by its unique dual-mode resonator structure. This filter significantly extends the bandwidth and maintains high frequency selectivity by simultaneously exciting two different acoustic modes in the same device. Its core advantage lies in achieving a steep roll-off characteristic within the passband, effectively suppressing out-of-band interference signals, while maintaining low insertion loss, which helps improve the overall efficiency of the communication system. Furthermore, the DMS-type filter supports a wider bandwidth, and its compact design makes it easy to miniaturize and integrate.
[0050] Furthermore, the filtering device is a B40 band (2300–2400 MHz) filter. The B40 band is a crucial frequency band used in time-division multiplexing (TDD) technology in mobile communications, playing a key role, especially in indoor coverage and high-capacity scenarios. Due to its high-frequency characteristics, the B40 band is widely used in indoor distribution systems and small base stations, effectively alleviating traffic pressure in high-density areas. In this band, the filter, as a core component of the communication system, directly affects signal transmission efficiency and quality. For commercial filters, insertion loss is a critical indicator, typically required to be between -0.5 dB and -1.5 dB. A 0.1 dB reduction in insertion loss can significantly enhance the filter's competitiveness, not only improving signal transmission efficiency and reducing power consumption but also providing designers with more design margin when optimizing out-of-band rejection performance. Out-of-band rejection capability is equally important; the filter needs to provide sufficient rejection outside the B40 band (typically 30 dB–40 dB) to avoid interference from adjacent frequency bands. However, insertion loss and out-of-band rejection are often contradictory metrics, requiring designers to find a balance between them. By employing low-loss dielectric materials, optimizing filter structure, improving fabrication processes, and utilizing advanced simulation tools, the overall performance of filters can be effectively enhanced. With the advancement of 5G networks, the B40 band may continue to be used as a supplementary band, and the development trend of filters will move towards integration, miniaturization, and intelligence to meet the high performance and high reliability requirements of future communication networks.
[0051] 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.
[0052] 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 DMS type filter, characterized in that, The system includes a reflective grating and multiple independent acoustic transducers (IDTs) disposed between the reflective gratings. Each IDT is 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. The spacing between 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 quadratic power function, and the change in the spacing between adjacent interdigitated fingers in different adjustable spacing regions is different.
2. The DMS type filter according to claim 1, 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.
3. The DMS type filter according to claim 2, 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.
4. The DMS type filter according to claim 3, 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 reflective grating. The spacing variation patterns of adjacent interdigitated fingers in the adjustment spacing region 1 are the same or different in different IDTs.
5. The DMS type filter according to claim 4, 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 quadratic power function along the direction away from the main spacing region, and the amplitude of the interdigitate spacing change gradually increases.
6. The DMS type filter according to claim 4, 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 quadratic power function along the direction away from the main spacing region, and the change amplitude of the interdigitate spacing gradually increases.
7. The DMS type filter according to any one of claims 1 to 6, characterized in that, The number of interdigitated fingers is the same in each of the aforementioned adjustment spacing zones.
8. The DMS type filter according to any one of claims 1 to 6, 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.
9. A filtering device, characterized in that, Includes a trapezoidal filter and a DMS-type filter as described in any one of claims 1-8.
10. The filtering device according to claim 9, characterized in that, The filtering device is a B40 frequency band filtering device.