DMS filter structure for improving high-frequency suppression
By setting a specific interdigital gap variation mode in the DMS filter, the problems of poor high-frequency suppression and skirt characteristics of traditional filters after miniaturization are solved, and better out-of-band suppression and stopband attenuation effects on the high-frequency side are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional DMS filters, after miniaturization, struggle to achieve effective high-frequency suppression and improve skirt characteristics.
By setting several output interdigital transducers and input interdigital transducers in the DMS filter and adjusting the interdigital gap width in different regions, a specific interdigital gap variation pattern is formed, including equidistant regions and adjustment regions, thus optimizing the gradual and symmetrical setting of the interdigital gap width.
It improves the out-of-band suppression effect on the high-frequency side of the filter, enhances the skirt characteristics, and increases the steepness of the stopband attenuation.
Smart Images
Figure CN121749944A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of filter technology, and in particular to a DMS filter structure for improving high-frequency suppression. Background Technology
[0002] Generally, surface acoustic wave (SAW) filters utilize the characteristic of surface acoustic waves propagating along the surface of a piezoelectric material as a frequency selection device. A typical DMS filter mainly consists of a first reflector grating, a second reflector grating, and several interdigital transducers (IDTs) positioned between the first and second reflector gratings. However, in traditional filter structures, the interdigital transducers have equal interdigital spacing, resulting in a limited number of tunable resonators. This is especially problematic when filter sizes are miniaturized, making it difficult to achieve attenuation effects and deteriorating the skirt characteristics on both the high-frequency side of the transmitter and the low-frequency side of the receiver. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a DMS filter structure for improving high-frequency suppression, wherein the filter structure improves the high-frequency suppression performance by adjusting a specific interdigital gap.
[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a DMS filter structure for improving high-frequency suppression, comprising a first reflective grating and a second reflective grating. The DMS filter structure further comprises a plurality of output interdigital transducers and input interdigital transducers. The output interdigital transducers and input interdigital transducers are spaced apart from each other and coupled to each other along the surface acoustic wave propagation direction. Each input interdigital transducer is connected to an input terminal, and each output interdigital transducer is connected to an output terminal. The output interdigital transducers and input interdigital transducers are divided into a first region, a second region, a third region, a fourth region, and a fifth region along the direction from the first reflective grating to the second reflective grating. The first region includes a first equidistant region and a first adjustment region. The second region includes a second equidistant region and a second left adjustment region and a second right adjustment region located on both sides of the second equidistant region. The third region includes a third equidistant region and a third left adjustment region and a third right adjustment region located on both sides of the third equidistant region. The fourth region includes a fourth equidistant region and a fourth left adjustment region and a fourth right adjustment region located on both sides of the fourth equidistant region. The fifth region includes a fifth equidistant region and a fifth adjustment region.
[0005] The system comprises the following: the first adjustment region is connected to the second left adjustment region; the second right adjustment region is connected to the third left adjustment region; the third right adjustment region is connected to the fourth left adjustment region; and the fourth right adjustment region is connected to the fifth adjustment region. The interdigital gap widths in the third left adjustment region gradually decrease and eventually equal to the interdigital gap widths in the third equidistant region. The interdigital gap widths in the third right adjustment region are symmetrically arranged with respect to the interdigital gap widths in the third left adjustment region. The interdigital gap widths in the second right adjustment region gradually increase and eventually equal to the maximum interdigital gap width in the third left adjustment region. The maximum interdigital gap width in the fourth left adjustment region is equal to the maximum interdigital gap width in the third right adjustment region. The interdigital gap widths in the fourth left adjustment region gradually decrease and eventually equal to the interdigital gap widths in the fourth equidistant region.
[0006] As a preferred embodiment, the interdigital gap widths in the first adjustment region gradually decrease and become equal to the smallest interdigital gap width in the second left adjustment region, while the interdigital gap widths in the second left adjustment region gradually increase and eventually become equal to the interdigital gap widths in the second equidistant region.
[0007] As a preferred embodiment, the interdigital gap widths in the fourth right adjustment region gradually decrease and become equal to the smallest interdigital gap width in the fifth left adjustment region, while the interdigital gap widths in the fifth left adjustment region gradually increase and eventually become equal to the interdigital gap widths in the fifth equidistant region.
[0008] As a preferred embodiment, the interdigital gap widths in the first reflective grating are equal and greater than the interdigital gap widths in the first equidistant region, and the interdigital gap widths in the second reflective grating are equal and greater than the interdigital gap widths in the fifth equidistant region.
[0009] As a preferred embodiment, the interdigital gap width of the first reflective grating is equal to the interdigital gap width of the second reflective grating.
[0010] As a preferred embodiment, the maximum interdigital gap width in the third left adjustment region is between 1 and 2 times the interdigital gap width in the third equidistant region.
[0011] After adopting the above technical solution, the effect of the present invention is as follows: Since the first adjustment region and the second left adjustment region are connected, the second right adjustment region is connected to the third left adjustment region, the third right adjustment region is connected to the fourth left adjustment region, and the fourth right adjustment region is connected to the fifth adjustment region; the interdigital gap widths of the third left adjustment region gradually decrease and eventually equal to the interdigital gap widths of the third equidistant region; the interdigital gap widths of the third right adjustment region and the interdigital gap widths of the third left adjustment region are symmetrically set; the interdigital gap widths of the second right adjustment region gradually increase and eventually equal to the maximum interdigital gap width of the third left adjustment region; the maximum interdigital gap width of the fourth left adjustment region is equal to the maximum interdigital gap width of the third right adjustment region; and the interdigital gap widths of the fourth left adjustment region gradually decrease and eventually equal to the interdigital gap widths of the fourth equidistant region, therefore, by improving the variation of the interdigital gap widths in the third region, the skirt characteristics of the high-frequency side of the filter are improved, the steepness of the stopband attenuation is increased, and the out-of-band suppression on the high-frequency side is better. Attached Figure Description
[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0013] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;
[0014] Figure 2 This is a diagram showing the interdigital spacing distribution according to an embodiment of the present invention;
[0015] Figure 3 This is a performance comparison chart in an embodiment of the present invention;
[0016] In the attached diagram: 1. First reflective grating 1; 2. Input terminal; 3. Second reflective grating 3; 4. Output terminal; 5. Input interdigital transducer; 6. Output interdigital transducer; A. First reflection region; B. First region; B1. First equidistant region; B2. First adjustment region; C. Second region; C1. Second left adjustment region; C2. Second equidistant region; C3. Second right adjustment region; D. Third region; D1. Third left adjustment region; D2. Third equidistant region; D3. Third right adjustment region; E. Fourth region; E1. Fourth left adjustment region; E2. Fourth equidistant region; E3. Fourth right adjustment region; F. Fifth region; F1. Fifth equidistant region; F2. Fifth adjustment region; G. Second reflection region. Detailed Implementation
[0017] The present invention will be further described in detail below through specific embodiments.
[0018] like Figure 1 and Figure 2As shown, a DMS filter structure for improving high-frequency suppression includes a first reflective grating 1 and a second reflective grating 3. The DMS filter structure also includes several output interdigital transducers 6 and input interdigital transducers 5. The output interdigital transducers 6 and input interdigital transducers 5 are spaced apart and coupled to each other along the surface acoustic wave propagation direction. Each input interdigital transducer 5 is connected to an input terminal 2, and each output interdigital transducer 6 is connected to an output terminal 4. Along the direction from the first reflective grating 1 to the second reflective grating 3, both the output interdigital transducers 6 and the input interdigital transducers 5 are divided into a first region B, a second region C, a third region D, a fourth region E, and a fifth region F. In this embodiment, since the interdigital transducers have multiple interdigital electrodes, each interdigital transducer includes the above five regions. The regions where the first reflective grating 1 and the second reflective grating 3 are located are the first reflection region A and the second reflection region G, respectively.
[0019] like Figure 2 As shown, the first region B includes a first equidistant region B1 and a first adjustment region B2; the second region C includes a second equidistant region C2 and a second left adjustment region C1 and a second right adjustment region C3 located on both sides of the second equidistant region C2; the third region D includes a third equidistant region D2 and a third left adjustment region D1 and a third right adjustment region D3 located on both sides of the third equidistant region D2; the fourth region E includes a fourth equidistant region E2 and a fourth left adjustment region E1 and a fourth right adjustment region E3 located on both sides of the fourth equidistant region E2; and the fifth region F includes a fifth equidistant region F1 and a fifth adjustment region F2.
[0020] The first adjustment region B2 is connected to the second left adjustment region C1. The interdigital gap width of each finger in the first adjustment region B2 gradually decreases and becomes equal to the smallest interdigital gap width in the second left adjustment region C1. The interdigital gap width of each finger in the second left adjustment region C1 gradually increases and eventually becomes equal to the interdigital gap width of the second equidistant region C2. Therefore, the minimum interdigital gap width is formed at the junction of the first adjustment region B2 and the second left adjustment region C1.
[0021] The second right adjustment region C3 connects with the third left adjustment region D1, the third right adjustment region D3 connects with the fourth left adjustment region E1, and the fourth right adjustment region E3 connects with the fifth adjustment region F2.
[0022] The interdigitation widths of the third left adjustment region D1 gradually decrease and eventually equal the interdigitation widths of the third equidistant region D2; the interdigitation widths of the third right adjustment region D3 are symmetrically set to the left and right of the interdigitation widths of the third left adjustment region D1; the interdigitation widths of the second right adjustment region C3 gradually increase and eventually equal the maximum interdigitation width of the third left adjustment region D1; the maximum interdigitation width of the fourth left adjustment region E1 is equal to the maximum interdigitation width of the third right adjustment region D3; and the interdigitation widths of the fourth left adjustment region E1 gradually decrease and eventually equal the interdigitation width of the fourth equidistant region E2.
[0023] Therefore, the maximum interdigital gap width is formed at the junction of the third left adjustment region D1 and the second right adjustment region C3, and at the junction of the third right adjustment region D3 and the fourth left adjustment region E1.
[0024] In this region, the interdigital gap widths of the fourth right adjustment region E3 gradually decrease and become equal to the minimum interdigital gap width in the fifth left adjustment region. Conversely, the interdigital gap widths of the fifth left adjustment region gradually increase and eventually become equal to the interdigital gap width of the fifth equidistant region F1. Therefore, the minimum interdigital gap is formed at the junction of the fourth right adjustment region E3 and the fifth left adjustment region. Furthermore, the rate of change of the interdigital gap widths of the first right adjustment region and the fourth right adjustment region E3 is equal, as are the rates of change of the interdigital gap widths of the third left adjustment region D1 and the fifth left adjustment region.
[0025] The interdigitated gaps in the first reflective grating 1 are all equal in width and greater than the interdigitated gap width in the first equidistant region B1. The interdigitated gaps in the second reflective grating 3 are all equal in width and greater than the interdigitated gap width in the fifth equidistant region F1. The interdigitated gap width of the first reflective grating 1 is equal to the interdigitated gap width of the second reflective grating 3.
[0026] The maximum interdigital gap width in the third left adjustment region D1 is between 1 and 2 times the interdigital gap width in the third equidistant region D2. For example... Figure 2 As shown, the preferred ratio in this embodiment is 1.05 times.
[0027] like Figure 3 As shown, Figure 3 The solid line curve in the figure represents the performance curve of a conventional filter with an equal interdigital gap width; the dashed line represents the performance curve of this embodiment. From the curve of this embodiment, it can be seen that there is a steep downward drop on the right side of the passband (that is, the high-frequency side), which better reflects the out-of-band suppression on the high-frequency side.
[0028] Similarly, the left low-frequency side in this embodiment also outperforms the performance of existing filters.
[0029] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications and alterations made to the technical solutions of the present invention without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.
Claims
1. A DMS filter structure for improving high-frequency suppression, comprising a first reflective grating and a second reflective grating, characterized in that: The DMS filter structure further includes several output interdigital transducers and input interdigital transducers. The output interdigital transducers and input interdigital transducers are spaced apart from each other and coupled to each other along the surface acoustic wave propagation direction. Each input interdigital transducer is connected to the input terminal, and each output interdigital transducer is connected to the output terminal. The output interdigital transducers and input interdigital transducers are divided into a first region, a second region, a third region, a fourth region, and a fifth region along the direction from the first reflector to the second reflector. The first region includes a first equidistant region and a first adjustment region; the second region includes a second equidistant region and a second left adjustment region and a second right adjustment region located on both sides of the second equidistant region; the third region includes a third equidistant region and a third left adjustment region and a third right adjustment region located on both sides of the third equidistant region; the fourth region includes a fourth equidistant region and a fourth left adjustment region and a fourth right adjustment region located on both sides of the fourth equidistant region; and the fifth region includes a fifth equidistant region and a fifth adjustment region. The system comprises the following: the first adjustment region is connected to the second left adjustment region; the second right adjustment region is connected to the third left adjustment region; the third right adjustment region is connected to the fourth left adjustment region; and the fourth right adjustment region is connected to the fifth adjustment region. The interdigital gap widths in the third left adjustment region gradually decrease and eventually equal to the interdigital gap widths in the third equidistant region. The interdigital gap widths in the third right adjustment region are symmetrically arranged with respect to the interdigital gap widths in the third left adjustment region. The interdigital gap widths in the second right adjustment region gradually increase and eventually equal to the maximum interdigital gap width in the third left adjustment region. The maximum interdigital gap width in the fourth left adjustment region is equal to the maximum interdigital gap width in the third right adjustment region. The interdigital gap widths in the fourth left adjustment region gradually decrease and eventually equal to the interdigital gap widths in the fourth equidistant region.
2. The DMS filter structure for improving high-frequency suppression as described in claim 1, characterized in that: The interdigital gap width in the first adjustment region gradually decreases and becomes equal to the smallest interdigital gap width in the second left adjustment region. The interdigital gap width in the second left adjustment region gradually increases and eventually becomes equal to the interdigital gap width in the second equidistant region.
3. The DMS filter structure for improving high-frequency suppression as described in claim 2, characterized in that: The interdigital gap widths in the fourth right adjustment region gradually decrease and become equal to the smallest interdigital gap width in the fifth left adjustment region. The interdigital gap widths in the fifth left adjustment region gradually increase and eventually become equal to the interdigital gap widths in the fifth equidistant region.
4. The DMS filter structure for improving high-frequency suppression as described in claim 3, characterized in that: The interdigitation gaps in the first reflective grating are of equal width and are greater than the interdigitation gap width in the first equidistant region, and the interdigitation gaps in the second reflective grating are of equal width and are greater than the interdigitation gap width in the fifth equidistant region.
5. The DMS filter structure for improved high-frequency suppression as described in claim 4, characterized in that: The interdigitation gap width of the first reflective grating is equal to the interdigitation gap width of the second reflective grating.
6. The DMS filter structure for improving high-frequency suppression as described in claim 1, characterized in that: The maximum interdigital gap width in the third left adjustment region is between 1 and 2 times the interdigital gap width in the third equidistant region.