A surface acoustic wave resonator and filter

Abstract

The present application provides a surface acoustic wave resonator and a filter, wherein the interdigital region includes a first section and a second section; the first section includes a first subsection and a second subsection, the first subsection includes a plurality of first short fingers and a plurality of first long fingers; the second subsection includes a plurality of second short fingers and a plurality of second long fingers; the second section includes a third subsection and a fourth subsection, the third subsection includes a plurality of third short fingers and a plurality of third long fingers; the fourth subsection includes a plurality of fourth short fingers and a plurality of fourth long fingers; the first short finger and the second short finger have different lengths extending along the first direction, and the third short finger and the fourth short finger have different lengths extending along the first direction. By adjusting the lengths of the first short finger, the second short finger, the third short finger and the fourth short finger extending along the first direction, a sudden aperture change can be caused, so that the transverse wave propagating along the first direction is reflected back into the surface acoustic wave resonator, thereby reducing the surface acoustic wave leakage, improving the Q value, and improving the performance of the surface acoustic wave resonator.

Description

Technical Field

[0001] The present application relates to the technical field of resonators, and in particular to a surface acoustic wave resonator and a filter. Background Art

[0002] A surface acoustic wave resonator (SAWR) is a resonant device that uses surface acoustic waves (SAW) to propagate in a crystal. SAW is a mechanical wave that propagates through surface vibrations generated on the surface of a crystal. SAWR uses the special structure and material properties of the crystal to cause surface acoustic waves to resonate in the crystal. SAWR is usually made of piezoelectric crystals, such as quartz or lithium tantalate crystals. When voltage is applied to the crystal, the piezoelectric effect causes the crystal to vibrate mechanically, generating surface acoustic waves on the surface of the crystal. These surface acoustic waves propagate in the crystal and resonate at a specific frequency.

[0003] Surface Acoustic Wave Filter (SAW Filter) is a filter device that uses surface acoustic waves to propagate in crystals. SAW filters selectively transmit or suppress signals of specific frequencies by utilizing the propagation characteristics of surface acoustic waves in crystals. The working principle of SAW filters is based on the propagation and interference of surface acoustic waves in crystals. This principle makes SAW filters have important application value in wireless communications and other fields.

[0004] In surface acoustic wave filters, lateral parasitic modes are an unwanted additional mode. It means that in the process of surface acoustic wave propagation, in addition to the main mode of design intent, there are other lateral propagation modes. The existence of lateral parasitic modes may have a negative impact on the performance of SAW filters, such as causing an increase in insertion loss, distortion of frequency response, and increasing the bandwidth of the filter. Therefore, when designing SAW filters, it is necessary to suppress or eliminate the influence of lateral parasitic modes as much as possible. Summary of the invention

[0005] The present application provides a surface acoustic wave resonator and a filter, which are used to solve the problems of increased insertion loss, frequency response distortion, increased bandwidth and cross-coupling that may be caused by lateral parasitic modes.

[0006] In a first aspect, the present application provides a surface acoustic wave resonator, comprising an interdigital region and a bus bar;

[0007] The interdigital region includes a first sub-section and a second sub-section, and along a first direction, the first sub-section and the second sub-section are respectively located at two sides of the interdigital region;

[0008] The first subdivision includes at least one first subdivision and at least one second subdivision, and the first subdivision and the second subdivision are arranged alternately in sequence along the second direction; the first subdivision includes a plurality of first short fingers and a plurality of first long fingers, and the first short fingers and the first long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the second subdivision includes a plurality of second short fingers and a plurality of second long fingers, and the second short fingers and the second long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the first direction intersects with the second direction;

[0009] The second subdivision includes at least one third subdivision and at least one fourth subdivision, and the third subdivision and the fourth subdivision are arranged alternately in sequence along the second direction; the third subdivision includes a plurality of third short fingers and a plurality of third long fingers, and the third short fingers and the third long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the fourth subdivision includes a plurality of fourth short fingers and a plurality of fourth long fingers, and the fourth short fingers and the fourth long fingers extend along the first direction and are arranged alternately in sequence along the second direction;

[0010] The first short finger and the second short finger have different lengths extending along the first direction, and the third short finger and the fourth short finger have different lengths extending along the first direction.

[0011] Preferably, the first division includes a first sub-divisions and b second sub-divisions, and the second division includes c third sub-divisions and d fourth sub-divisions;

[0012] Among them, a, b, c and d are all positive integers, and a=c, b=d.

[0013] The difference between the lengths of the first short finger and the second short finger extending along the first direction is a first difference, and the difference between the lengths of the third short finger and the fourth short finger extending along the first direction is a second difference. The first difference and the second difference may be positive or negative.

[0014] Preferably, the first short finger and the third long finger are arranged opposite to each other, and there is a first gap between the first short finger and the third long finger;

[0015] The first long finger and the third short finger are arranged opposite to each other, and a second gap is formed between the first long finger and the third short finger;

[0016] The second short finger and the fourth long finger are arranged opposite to each other, and a third gap is formed between the second short finger and the fourth long finger;

[0017] The second long finger and the fourth short finger are arranged opposite to each other, and a fourth gap is formed between the second long finger and the fourth short finger.

[0018] Preferably, the first gap, the second gap, the third gap and the fourth gap are equal in length;

[0019] The length of the first gap is 0.2 μm to 0.8 μm.

[0020] Preferably, the length of the first short finger extending along the first direction is 0.5 to 4 times the wavelength of the surface acoustic wave.

[0021] Preferably, the aperture length of the interdigital region is 10 to 50 times the wavelength of the surface acoustic wave.

[0022] Preferably, the widths of the first short finger, the first long finger, the second short finger, the second long finger, the third short finger, the third long finger, the fourth short finger and the fourth long finger are equal; there is a first spacing between the first short finger and the first adjacent long finger, and the ratio of the width of the first short finger to the first spacing is 0.8~2.

[0023] Preferably, the width of the first short finger is equal to the first spacing; the sum of the width of the first short finger and the first spacing is 0.5 times the wavelength of the surface acoustic wave.

[0024] Preferably, the surface acoustic wave resonator further comprises a reflection grating structure, and the reflection grating structure is arranged on both sides of the interdigital region.

[0025] In a second aspect, the present application further provides a filter, comprising the surface acoustic wave resonator described in the first aspect.

[0026] The surface acoustic wave resonator and filter provided by the present application, the interdigital region includes a first section and a second section, and along the first direction, the first section and the second section are respectively located on both sides of the interdigital region; the first section includes at least one first sub-section and at least one second sub-section, the first sub-section includes a plurality of first short fingers and a plurality of first long fingers; the second sub-section includes a plurality of second short fingers and a plurality of second long fingers; the second section includes at least one third sub-section and at least one fourth sub-section, the third sub-section includes a plurality of third short fingers and a plurality of third long fingers; the fourth sub-section includes a plurality of fourth short fingers and a plurality of fourth long fingers; the first short fingers and the second short fingers have different lengths extending along the first direction, and the third short fingers and the fourth short fingers have different lengths extending along the first direction.

[0027] The size of the aperture also affects the insertion loss of the filter, and adjusting the aperture can also affect the filter's ability to suppress out-of-band signals. Larger apertures generally provide better out-of-band suppression, but may increase insertion loss.

[0028] By adjusting the lengths of the first short finger, the second short finger, the third short finger and the fourth short finger extending along the first direction, a sudden aperture change can be caused, so that the transverse wave propagating along the first direction is reflected back into the surface acoustic wave resonator, thereby reducing surface acoustic wave leakage, increasing the Q value, and improving the performance of the surface acoustic wave resonator.

[0029] By adjusting the aperture size of the fingers in the surface acoustic wave filter, the filter's performance indicators such as frequency response, bandwidth, insertion loss and temperature stability can be precisely controlled to meet different application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave resonator provided in Example 1 of the present application. Figure 1 ;

[0032] Figure 2 A schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of the present application Figure 2 ;

[0033] Figure 3 A schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of the present application Figure 3 ;

[0034] Figure 4 A schematic diagram of the structure of another surface acoustic wave resonator provided in an embodiment of the present application;

[0035] Figure 5 A schematic diagram of the structure of another surface acoustic wave resonator provided in an embodiment of the present application;

[0036] Figure 6 A schematic diagram of the structure of another surface acoustic wave resonator provided in an embodiment of the present application;

[0037] Figure 7 A graph showing test results of the surface acoustic wave resonator provided in an embodiment of the present invention and a surface acoustic wave resonator in the prior art. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0040] The present application provides a surface acoustic wave resonator, comprising an interdigital region 1 and a bus bar 2;

[0041] The interdigital region 1 includes a first sub-portion 11 and a second sub-portion 12. Along a first direction Y, the first sub-portion 11 and the second sub-portion 12 are respectively located at two sides of the interdigital region 1;

[0042] The first subdivision 11 includes at least one first subdivision 111 and at least one second subdivision 112, the first subdivision 111 and the second subdivision 112 are arranged alternately in sequence along the second direction X; the first subdivision 111 includes a plurality of first short fingers 1111 and a plurality of first long fingers 1112, the first short fingers 1111 and the first long fingers 1112 extend along the first direction Y and are arranged alternately in sequence along the second direction X; the second subdivision 112 includes a plurality of second short fingers 1121 and a plurality of second long fingers 1122, the second short fingers 1121 and the second long fingers 1122 extend along the first direction Y and are arranged alternately in sequence along the second direction X; the first direction Y intersects with the second direction X;

[0043] The second subdivision 12 includes at least one third subdivision 121 and at least one fourth subdivision 122, and the third subdivision 121 and the fourth subdivision 122 are alternately arranged in sequence along the second direction X; the third subdivision 121 includes a plurality of third short fingers 1211 and a plurality of third long fingers 1212, and the third short fingers 1211 and the third long fingers 1212 extend along the first direction Y and are alternately arranged in sequence along the second direction X; the fourth subdivision 122 includes a plurality of fourth short fingers 1221 and a plurality of fourth long fingers 1222, and the The fourth short fingers 1221 and the fourth long fingers 1222 extend along the first direction Y and are alternately arranged in sequence along the second direction X; that is, the plurality of first short fingers 1111 and the plurality of first long fingers 1112 form a comb-like structure, the plurality of second short fingers 1121 and the plurality of second long fingers 1122 form a comb-like structure, the plurality of second short fingers 1121 and the plurality of second long fingers 1122 form a comb-like structure, the plurality of third short fingers 1211 and the plurality of third long fingers 1212 form a comb-like structure, and the plurality of fourth short fingers 1221 and the plurality of fourth long fingers 1222 form a comb-like structure. In addition, along the first direction Y, the first short fingers 1111 and the third long fingers 1212 are arranged in one-to-one correspondence, the first long fingers 112 and the third short fingers 1211 are arranged in one-to-one correspondence, the second short fingers 1121 and the fourth long fingers 1222 are arranged in one-to-one correspondence, and the second long fingers 1122 and the fourth short fingers 1221 are arranged in one-to-one correspondence.

[0044] The size of the aperture also affects the insertion loss of the filter. Adjusting the aperture can also affect the filter's ability to reject out-of-band signals. Larger apertures generally provide better out-of-band rejection but may increase insertion loss.

[0045] By adjusting the lengths of the first short finger 1111, the second short finger 1121, the third short finger 1211 and the fourth short finger 1221 extending along the first direction Y, a sudden aperture change can be caused so that the transverse waves propagating along the first direction Y are reflected back into the surface acoustic wave resonator, thereby reducing surface acoustic wave leakage, increasing the Q value, and improving the performance of the surface acoustic wave resonator.

[0046] By adjusting the aperture size of the fingers in the surface acoustic wave filter, the filter's performance indicators such as frequency response, bandwidth, insertion loss and temperature stability can be precisely controlled to meet different application requirements.

[0047] The first short finger 1111 and the second short finger 1121 have different lengths extending along the first direction Y, and the third short finger 1211 and the fourth short finger 1221 have different lengths extending along the first direction Y. The above arrangement can achieve a sudden change in aperture, thereby suppressing shear waves, and can achieve a diversified design of surface acoustic wave resonators.

[0048] The first short finger 1111, the first long finger 1112, the second short finger 1121, the second long finger 1122, the third short finger 1211, the third long finger 1212, the fourth short finger 1221 and the fourth long finger 1222 are all IDT electrodes, and the IDT electrode can be used for acoustic-electric energy conversion. Exemplarily, the IDT electrode can be arranged on a piezoelectric wafer. The material of the IDT electrode and the reflector can be metals such as Cu, Al, Pt, Ti and Cr, or alloys composed of the above metals, or a laminated composite structure can be used. The piezoelectric wafer can include piezoelectric materials such as LiTaO3, LiNbO3 or quartz, as well as a composite multilayer wafer formed by bonding the above piezoelectric materials with SiO2, SiC, Si or AlN. Exemplarily, the busbar and the long finger can be formed by one-time photolithography, and the material is generally Al or its alloy, wherein the material Cu is generally used in the temperature-compensated surface acoustic wave filter.

[0049] Preferably, the first division 11 includes a first sub-division 111 and b second sub-division 112, and the second division 12 includes c third sub-division 121 and d fourth sub-division 122;

[0050] Among them, a, b, c and d are all positive integers, and a=c, b=d.

[0051] For example, Figure 1~Figure 5 The first division 11 shown in FIG. 1 includes three first subdivisions 111 and two second subdivisions 112, and the second division 12 includes three third subdivisions 121 and two fourth subdivisions 122, that is, a=c=3, b=d=2. It can be understood that Figure 1~Figure 5 Only the technical solution in which the number of the first sub-divisions 111 is not equal to the number of the second sub-divisions 112 is shown.

[0052] For example, Figure 6 The first division 11 shown in FIG. 1 includes two first subdivisions 111 and two second subdivisions 112, and the second division 12 includes two third subdivisions 121 and two fourth subdivisions 122, that is, a=c=b=d=2. It can be understood that Figure 6 Only the technical solution in which the number of the first sub-divisions 111 is equal to the number of the second sub-divisions 112 is shown.

[0053] The embodiment of the present invention does not specifically limit the number of the first sub-divisions 111 and the second sub-divisions 112 .

[0054] The difference in length between the first short finger 1111 and the second short finger 1121 extending along the first direction Y is a first difference m, and the difference in length between the third short finger 1211 and the fourth short finger 1221 extending along the first direction Y is a second difference n. The first difference m and the second difference n may be positive or negative.

[0055] For example, Figure 1 and Figure 4 The first difference m>0 and the second difference n>0 shown in FIG. 1 , that is, the first subsection 11 and the second subsection 12 have the same change trend along the second direction X; Figure 5 and Figure 6 The first difference m shown in the figure is greater than 0, and the second difference n is less than 0, that is, the first sub-portion 11 and the second sub-portion 12 have opposite changing trends along the second direction X. It can be understood that Figure 1 to Figure 6 Only the technical solution of m≠n is shown, but in some embodiments m=n, that is, the first sub-portion 11 and the second sub-portion 12 are arranged in an axisymmetric manner.

[0056] Preferably, the first short finger 1111 and the third long finger 1212 are arranged opposite to each other, and there is a first gap between the first short finger 1111 and the third long finger 1212;

[0057] The first long finger 1112 and the third short finger 1211 are arranged opposite to each other, and a second gap is formed between the first long finger 1112 and the third short finger 1211;

[0058] The second short finger 1121 and the fourth long finger 1222 are arranged opposite to each other, and a third gap is formed between the second short finger 1121 and the fourth long finger 1222;

[0059] The second long finger 1122 and the fourth short finger 1221 are arranged opposite to each other, and a fourth gap is defined between the second long finger 1122 and the fourth short finger 1221 .

[0060] It is understandable that the lengths of the first gap, the second gap, the third gap and the fourth gap may be all equal, all unequal or partially equal. Figure 1 to Figure 6 The lengths of the first gap, the second gap, the third gap and the fourth gap shown in the figure are all equal. The embodiment of the present invention does not specifically limit the lengths of the first gap, the second gap, the third gap and the fourth gap.

[0061] Preferably, the lengths of the first gap, the second gap, the third gap and the fourth gap are equal, so that the overall structure is consistent and easy to design and maintain;

[0062] The length of the first gap is 0.2 μm to 0.8 μm, which can better suppress the lateral mode and improve the Q value of the surface acoustic wave resonator.

[0063] Preferably, the length of the first short finger 1111 extending along the first direction Y is 0.5 to 4 times the wavelength of the surface acoustic wave, which can better suppress the lateral mode and improve the Q value of the surface acoustic wave resonator.

[0064] Preferably, the aperture length of the interdigital region 1 is 10 to 50 times the wavelength of the surface acoustic wave, which can better suppress the lateral mode and improve the Q value of the surface acoustic wave resonator.

[0065] Preferably, the first short finger 1111, the first long finger 1112, the second short finger 1121, the second long finger 1122, the third short finger 1211, the third long finger 1212, the fourth short finger 1221 and the fourth long finger 1222 have the same width; there is a first spacing between the first short finger 1111 and the first long finger 1112 adjacent thereto, and the ratio of the width of the first short finger 1111 to the first spacing is 0.8 to 2. In this way, the lateral mode can be better suppressed and the Q value of the surface acoustic wave resonator can be improved.

[0066] Preferably, the width of the first short finger 1111 is equal to the first spacing; the sum of the width of the first short finger 1111 and the first spacing is 0.5 times the wavelength of the surface acoustic wave, which can better suppress the lateral mode and improve the Q value of the surface acoustic wave resonator.

[0067] Preferably, the surface acoustic wave resonator further comprises a reflection grating structure, which is arranged on both sides of the interdigital region 1. Adding the reflection grating can enhance the selectivity of the filter, expand the bandwidth of the filter, reduce the size of the filter and improve the stability of the filter.

[0068] Figure 7 The test results of the surface acoustic wave resonator provided by the embodiment of the present invention and the surface acoustic wave resonator in the prior art are shown in FIG. Figure 7 , Figure 7 The horizontal axis in represents the frequency, Figure 7 The ordinate in the figure represents the admittance. The red curve represents the admittance curve of the surface acoustic wave resonator in the prior art, and the blue curve represents the admittance curve of the surface acoustic wave resonator provided in this embodiment. The left peak of the red curve and the blue curve is the resonance point, and the right peak is the anti-resonance point. Figure 7 It can be seen that the admittance curve of the surface acoustic wave resonator provided by the prior art has obvious lateral mode noise between the resonance point and the anti-resonance point, while the admittance curve obtained by using the surface acoustic wave resonator provided by this embodiment is very smooth between the resonance point and the anti-resonance point, and the lateral mode suppression effect is obvious.

[0069] Based on the same inventive concept, an embodiment of the present invention further provides a filter, including the surface acoustic wave resonator in the above embodiment. Therefore, the filter provided by the embodiment of the present invention also has the beneficial effects described in the above embodiment, which will not be repeated here.

[0070] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A surface acoustic wave resonator, characterized in that: including interdigital areas and bus bars; The interdigital region includes a first sub-section and a second sub-section, and along a first direction, the first sub-section and the second sub-section are respectively located at two sides of the interdigital region; The first subdivision includes at least one first subdivision and at least one second subdivision, and the first subdivision and the second subdivision are arranged alternately in sequence along the second direction; the first subdivision includes a plurality of first short fingers and a plurality of first long fingers, and the first short fingers and the first long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the second subdivision includes a plurality of second short fingers and a plurality of second long fingers, and the second short fingers and the second long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the first direction intersects with the second direction; The second subdivision includes at least one third subdivision and at least one fourth subdivision, and the third subdivision and the fourth subdivision are arranged alternately in sequence along the second direction; the third subdivision includes a plurality of third short fingers and a plurality of third long fingers, and the third short fingers and the third long fingers extend along the first direction and are arranged alternately in sequence along the second direction; the fourth subdivision includes a plurality of fourth short fingers and a plurality of fourth long fingers, and the fourth short fingers and the fourth long fingers extend along the first direction and are arranged alternately in sequence along the second direction; The first short finger and the second short finger have different lengths extending along the first direction, and the third short finger and the fourth short finger have different lengths extending along the first direction; The first division includes a first sub-divisions and b second sub-divisions, and the second division includes c third sub-divisions and d fourth sub-divisions; wherein a, b, c and d are all positive integers, and a=c, b=d; The first short finger and the third long finger are arranged opposite to each other, with a first gap between them; the first long finger and the third short finger are arranged opposite to each other, with a second gap between them; the second short finger and the fourth long finger are arranged opposite to each other, with a third gap between them; the second long finger and the fourth short finger are arranged opposite to each other, with a fourth gap between them.

2. The surface acoustic wave resonator according to claim 1, characterized in that: The lengths of the first gap, the second gap, the third gap and the fourth gap are equal; The length of the first gap is 0.2 μm to 0.8 μm.

3. The surface acoustic wave resonator according to claim 1, characterized in that: The length of the first short finger extending along the first direction is 0.5 to 4 times the wavelength of the surface acoustic wave.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The aperture length of the interdigital region is 10 to 50 times the wavelength of the surface acoustic wave.

5. The surface acoustic wave resonator according to claim 1, characterized in that: The first short finger, the first long finger, the second short finger, the second long finger, the third short finger, the third long finger, the fourth short finger and the fourth long finger are equal in width; There is a first distance between the first short finger and the first long finger adjacent to it, and a ratio of a width of the first short finger to the first distance is 0.8-2.

6. The surface acoustic wave resonator according to claim 5, characterized in that: The width of the first short finger is equal to the first spacing; the sum of the width of the first short finger and the first spacing is 0.5 times the wavelength of the surface acoustic wave.

7. The surface acoustic wave resonator according to claim 1, characterized in that: It also includes a reflective gate structure, which is arranged on both sides of the interdigital region.

8. A filter, characterized in that: The invention comprises the surface acoustic wave resonator according to any one of claims 1 to 7.

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