Low-loss high-frequency surface acoustic wave filter

Abstract

The invention relates to a low-loss high-frequency surface acoustic wave filter, which comprises a substrate; the interdigital electrode is positioned on the surface of the substrate; the interdigital electrode comprises a first interdigital module and a second interdigital module which are connected in parallel; the first interdigital module comprises a first left reflecting grating, a first left transducer, a first energy trap, a first right transducer and a first right reflecting grating which are arranged in sequence; the second interdigital module comprises a second left reflecting grating, a second left transducer, a second energy trap, a second right transducer and a second right reflecting grating which are arranged in sequence; the first left transducer is connected with the second left transducer; the first right transducer is connected with the second right transducer; the aperture of the first interdigital module and the aperture of the second interdigital module are both W, W is smaller than 70 wavelengths, and the aperture of the interdigital electrode is W / 2.

Description

Technical Field

[0001] The invention relates to the technical field of filters, and in particular to a low-loss high-frequency surface acoustic wave filter. Background Art

[0002] Some radio stations have extremely high requirements for voice transmission quality, and the surface acoustic wave filters used in communication channels need to develop in the direction of narrow bandwidth, high frequency and low loss. At present, the conventional bandwidth of 1dB of the longitudinal coupling design structure of high-frequency narrowband surface acoustic wave filters is 0.07%, and the higher the frequency, the narrower the bandwidth and the more difficult it is to achieve. Through calculation, it can be seen that if an extremely narrow bandwidth is to be achieved, a small electromechanical coupling coefficient appears in a thinner film thickness range. Using a thinner film thickness will also increase the electrode ohmic loss. Summary of the invention

[0003] In view of the above analysis, an embodiment of the present invention aims to provide a low-loss high-frequency surface acoustic wave filter to at least solve one of the above problems.

[0004] The present invention provides a low-loss high-frequency surface acoustic wave filter, comprising:

[0005] substrate;

[0006] An interdigital electrode is located on the surface of the substrate; the interdigital electrode comprises a first interdigital module and a second interdigital module connected in parallel;

[0007] The first interdigital module comprises a first left reflection grid, a first left transducer, a first energy trap, a first right transducer and a first right reflection grid which are arranged in sequence;

[0008] The second interdigital module includes a second left reflection grid, a second left transducer, a second energy trap, a second right transducer and a second right reflection grid which are arranged in sequence;

[0009] The first left transducer is connected to the second left transducer;

[0010] The first right transducer is connected to the second right transducer;

[0011] The apertures of the first interdigital module and the second interdigital module are both W, W<70 wavelengths, and the aperture of the interdigital electrode is W / 2.

[0012] Further, the substrate is made of 36°AT quartz;

[0013] The material of the interdigital electrodes is aluminum-copper alloy, wherein the copper content is 2%;

[0014] The thickness of the interdigital electrodes is not less than 90 nm.

[0015] Furthermore, the first finger module and the second finger module have the same structure.

[0016] Furthermore, the components of the first interdigital module and the second interdigital module are configured with periods and numbers of interdigits or finger strips in a partitioned manner.

[0017] Furthermore, the left transducer and the right transducer are divided into two or more regions, and the number of fingers in the region far away from the energy trap is less than 20.

[0018] Furthermore, the left transducer is divided into three regions, namely, Nt11 region, Nt12 region and Nt13 region. The number of interdigital roots in Nt12 region is 15, and the number of interdigital roots in Nt13 region is 6.

[0019] The right transducer is divided into three areas, namely, Nt21 area, Nt22 area and Nt23 area. The number of interdigital roots in Nt22 area is 16, and the number of interdigital roots in Nt23 area is 11.

[0020] Furthermore, the number of fingers in the Nt11 region is 116, and the period is 0.6838μm; the number of fingers in the Nt12 region is 15, and the period is 0.6797μm; the number of fingers in the Nt13 region is 6, and the period is 0.6797μm. The number of fingers in the Nt21 region is 22, and the period is 0.679μm; the number of fingers in the Nt22 region is 16, and the period is 0.686μm; the number of fingers in the Nt23 region is 11, and the period is 0.6867μm.

[0021] Furthermore, the left reflection grid, the energy trap, and the right reflection grid are divided into two regions;

[0022] The left reflector is divided into Nr11 and Nr12 regions. The number of fingers in Nr11 region is 69, and the period is 0.695μm. The number of fingers in Nr12 region is 250, and the period is 0.6945μm.

[0023] The energy trap is divided into Nrt11 and Nrt12 regions. The number of fingers in Nrt11 region is 4, and the period is 0.6924μm. The number of fingers in Nrt12 region is 16, and the period is 0.6923μm.

[0024] The right reflection grating is divided into Nr21 zone and Nr22 zone. The number of fingers in Nr21 zone is 75 and the period is 0.694μm; the number of fingers in Nr22 zone is 200 and the period is 0.695μm.

[0025] Furthermore, in the first interdigital module and the second interdigital module, the distance between the energy trap and the transducer is less than 0.7 times of the period of the transducing region adjacent to the energy trap.

[0026] Furthermore, the first interdigital module and the second interdigital module can share the same reflective grating.

[0027] Compared with the prior art, the present invention can achieve at least one of the beneficial effects: the low-loss high-frequency surface acoustic wave filter of the present invention has a loss of less than 6dB at a frequency of 1800MHz and has an extremely narrow bandwidth (-1dB relative bandwidth ≤ 0.03%).

[0028] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0030] Figure 1 It is a schematic diagram of the structure of a low-loss high-frequency surface acoustic wave filter in a specific implementation manner;

[0031] Figure 2 It is a structural schematic diagram of a low-loss high-frequency surface acoustic wave filter in a specific implementation manner when two interdigital modules share a reflection deletion;

[0032] Figure 3 It is a partition diagram of the interdigital module in a specific implementation manner;

[0033] Figure 4 It is a schematic diagram of the structure of an asynchronous reflection grid in a specific implementation mode;

[0034] Figure 5 This is the measured frequency response diagram of the high-frequency ultra-narrow-band surface acoustic wave filter implemented in the specific implementation method (test SPAN: 50MHz);

[0035] Figure 6 This is the measured frequency response diagram of the high-frequency ultra-narrow-band surface acoustic wave filter implemented in the specific implementation manner (test SPAN: 200MHz).

[0036] Reference numerals:

[0037] 1-first interdigital module; 11-first left reflection grid; 12-first left transducer; 13-first energy trap; 14-first right transducer; 15-first right reflection grid; 2-second interdigital module; 21-second left reflection grid; 22-second left transducer, 23-second energy trap; 24-second right transducer; 25-second right reflection grid; 3-input line; 4-output line. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0039] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the term "connected" should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or an integral connection, which can be a mechanical connection, or an electrical connection, which can be a direct connection, or can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The terms "top", "bottom", "above", "lower", and "on" used throughout the description are relative to the relative positions of components of a device, such as the relative positions of the top and bottom substrates within a device. It is understood that devices are multifunctional regardless of their orientation in space.

[0041] The common working surface of the present invention can be a plane or a curved surface, can be inclined, or can be horizontal. For the convenience of description, the embodiment of the present invention is placed on a horizontal plane and used on the horizontal plane, and "high and low" and "up and down" are defined in this way.

[0042] A specific embodiment of the present invention discloses a low-loss high-frequency surface acoustic wave filter, such as Figure 1 to Figure 4 As shown, including:

[0043] substrate;

[0044] An interdigital electrode is located on the surface of the substrate; the interdigital electrode comprises a first interdigital module 1 and a second interdigital module 2 connected in parallel;

[0045] The first interdigital module 1 comprises a first left reflection grating 11, a first left transducer 12, a first energy trap 13, a first right transducer 14 and a first right reflection grating 15 which are arranged in sequence;

[0046] The second interdigital module 2 includes a second left reflection grid 21, a second left transducer 22, a second energy trap 23, a second right transducer 24 and a second right reflection grid 25 which are arranged in sequence;

[0047] The first left transducer 12 is connected to the second left transducer 22;

[0048] The first right transducer 14 is connected to the second right transducer 24;

[0049] The apertures of the first interdigital module and the second interdigital module are both W, W≤70 wavelengths, and the aperture of the interdigital electrode is W / 2; the wavelength λ, that is, W≤70λ, λ=v / f, where v is the speed of sound propagation of the surface acoustic wave, f is the center frequency of the realized surface acoustic wave filter, and v and f are preset values ​​before preparing the surface acoustic wave filter.

[0050] The substrate is preferably 36°AT quartz. In the propagation direction of the 36°AT quartz rotated 90°, the first interdigital module and the second interdigital module of the present invention are longitudinally coupled to form a STW acoustic wave propagation mode. This mode is used to clamp the surface-grazing body wave that originally propagates to the inside of the substrate to propagate on the surface, and a high sound velocity of 5100m / s can be obtained, making it easier to prepare high-frequency devices under the same process conditions. At the same time, the electromechanical coupling coefficient of the 36AT quartz substrate is very small, which is suitable for the preparation of extremely narrow-band surface acoustic wave devices.

[0051] The material of the interdigital electrodes is preferably aluminum-copper alloy, wherein the copper content is 2%. The ratio of the thickness to the width of the interdigital electrodes is greater than or equal to 3.5%. To reduce the ohmic loss of the electrodes, the absolute thickness should be no less than 90 nm.

[0052] Preferably, the first interdigital module 1 and the second interdigital module 2 have the same structure, that is, the first left reflection grating and the second left reflection grating have at least the same number of fingers (or number of strips) and period, the first left transducer and the second left transducer have at least the same number of fingers (or number of strips) and period, the second energy trap of the first energy trap has at least the same number of fingers (or number of strips) and period, the first right transducer and the second right transducer have at least the same number of fingers (or number of strips) and period, and the first right reflection grating and the second right reflection grating have at least the same number of fingers (or number of strips) and period.

[0053] The first left reflection grating 11 and the second left reflection grating 21 are collectively referred to as the left reflection grating, that is, the left reflection grating mentioned below includes the first left reflection grating 11 and the second left reflection grating 21, and the same applies to the interdigital module, left transducer, energy trap, right transducer, and right reflection grating.

[0054] The components of the first interdigital module 1 and the second interdigital module 2 are divided into zones to set the number of interdigital roots (or the number of finger strips) and the period, that is, the number of interdigital roots (or the number of finger strips) and the period in different areas of the same component are different, which can effectively reduce the loss of the surface acoustic wave filter.

[0055] The left transducer and the right transducer are divided into two or more regions, and the number of fingers in the region far away from the energy trap (ie, the region not adjacent to the energy trap) is less than 20.

[0056] Exemplarily, the left transducer is divided into three regions, namely, Nt11 region, Nt12 region and Nt13 region, the number of interdigital roots in Nt12 region is 15, and the number of interdigital roots in Nt13 region is 6. The right transducer is divided into three regions, namely, Nt21 region, Nt22 region and Nt23 region, the number of interdigital roots in Nt22 region is 16, and the number of interdigital roots in Nt23 region is 11.

[0057] Specifically, the number of fingers in the Nt11 region is 116, and the period is 0.6838μm; the number of fingers in the Nt12 region is 15, and the period is 0.6797μm; the number of fingers in the Nt13 region is 6, and the period is 0.6797μm. The number of fingers in the Nt21 region is 22, and the period is 0.679μm; the number of fingers in the Nt22 region is 16, and the period is 0.686μm; the number of fingers in the Nt23 region is 11, and the period is 0.6867μm.

[0058] The left reflector, energy trap and right reflector are divided into two regions. Specifically, the left reflector is divided into Nr11 region and Nr12 region. The number of fingers in Nr11 region is 69 and the period is 0.695μm; the number of fingers in Nr12 region is 250 and the period is 0.6945μm. The energy trap is divided into Nrt11 region and Nrt12 region. The number of fingers in Nrt11 region is 4 and the period is 0.6924μm; the number of fingers in Nrt12 region is 16 and the period is 0.6923μm. The right reflector is divided into Nr21 region and Nr22 region. The number of fingers in Nr21 region is 75 and the period is 0.694μm; the number of fingers in Nr22 region is 200 and the period is 0.695μm.

[0059] In the first interdigital module and the second interdigital module, the distance between the energy trap and the transducer is less than 0.7 times the period of the transducer adjacent energy trap area, that is, the distance between the energy trap 13 and the left transducer 12 is less than 0.7 times the period of the Nt13 area, and the distance between the energy trap 13 and the right transducer 14 is less than 0.7 times the period of the right Nt21 area.

[0060] In order to improve the utilization rate of the substrate, reduce the chip area of ​​the surface acoustic wave filter, and further reduce the size, the first interdigital module and the second interdigital module can share the same reflector. When designing the interdigital electrodes, only one of the first right reflector and the second left reflector needs to be retained, and the other one can be directly discarded. Figure 2As shown. Specifically, the first interdigital module includes a first left reflection grid, a first left transducer, a first energy trap, a first right transducer and a first right reflection grid arranged in sequence; the second interdigital module includes a second left transducer, a second energy trap, a second right transducer and a second right reflection grid arranged in sequence; the first left transducer is connected to the second left transducer; the first right transducer is connected to the second right transducer. Alternatively, the first interdigital module includes a first left reflection grid, a first left transducer, a first energy trap and a first right transducer arranged in sequence; the second interdigital module includes a second left reflection grid, a second left transducer, a second energy trap, a second right transducer and a second right reflection grid arranged in sequence; the first left transducer is connected to the second left transducer; the first right transducer is connected to the second right transducer.

[0061] It should be noted that the number of fingers in the drawings does not represent the actual number of fingers of the component, but is only used to illustrate the number of fingers in the simplified structure.

[0062] The same ends of adjacent fingers of the left reflector, right reflector and energy trap are connected by a bus bar, that is, the left reflector, right reflector and energy trap each include two bus bars, and all fingers are located between the two bus bars, that is, both ends of the fingers are connected to the two bus bars respectively.

[0063] The left transducer and the right transducer also include two bus bars, and one end of the forked finger is connected to one of the bus bars at intervals, that is, one end of the odd-numbered forked finger is connected to one bus bar, and the other end of the even-numbered forked finger (away from the end of the bus bar connected to the odd-numbered forked finger) is connected to another bus bar, that is, the forked fingers are staggered between the two bus bars, and the length of the forked fingers is less than the distance between the two bus bars.

[0064] All the bus bars of the left reflection grid, the right reflection grid, the energy trap, the left transducer and the right transducer are provided with grounding wires.

[0065] The first left transducer 12 is connected to the second left transducer 22 via an input line 3 , and the first right transducer 24 is connected to the second right transducer via an output line 4 .

[0066] To further reduce the loss, the input line 3 and the output line 4 are plated with thick gold, that is, the metal thickness is above 2 μm, that is, the input line 3 and the output line 4 are composed of metal with a thickness of above 2 μm, and the width of the input line 3 and the output line 4 is greater than 50 μm.

[0067] Preferably, the left and right reflection gratings are processed asynchronously, that is, the closer the reflection grating fingers are to the transducer, the smaller the period is, and the farther away from the transducer, the larger the period is. The maximum period of the reflection grating fingers is 1.0003 times the period of the adjacent transducer.

[0068] Furthermore, let the reflection grating finger closest to the transducer be the first finger, and define the number of reflection grating fingers from the inside to the outside as the nth finger. If the total number of reflection grating fingers is N, and the period of the first finger is P, then the period of the i-th finger is y=0.01*P*i 2 / N 2 .

[0069] [Example] A low-loss high-frequency surface acoustic wave filter, comprising:

[0070] Substrate: the material of the substrate is AT36° quartz substrate, the thickness is 0.35 mm, and the size is 4 inches;

[0071] An interdigital electrode is located on the surface of the substrate, the material of the interdigital electrode is aluminum copper (containing 2% copper), and the thickness is 89nm; the interdigital electrode includes a first interdigital module and a second interdigital module connected in parallel;

[0072] The first interdigital module comprises a first left reflection grid, a first left transducer, a first energy trap, a first right transducer and a first right reflection grid which are arranged in sequence;

[0073] The second interdigital module includes a second left reflection grid, a second left transducer, a second energy trap, a second right transducer and a second right reflection grid which are arranged in sequence;

[0074] The first left transducer is connected to the second left transducer;

[0075] The first right transducer is connected to the second right transducer;

[0076] The apertures of the first interdigital module and the second interdigital module are both W, W is 190.554 μm (i.e., W = 69.8λ, λ = 2.73 μm), and the aperture of the interdigital electrode is W / 2;

[0077] In the first interdigital module and the second interdigital module, the distance between the energy trap and the left transducer is 0.4787 μm, and the distance between the energy trap and the right transducer is 0.4753 μm;

[0078] The left reflector is divided into Nr11 and Nr12 regions. The number of fingers in Nr11 is 69, and the period is 0.695μm. The number of fingers in Nr12 is 250, and the period is 0.6945μm. The left transducer is divided into Nt11, Nt12 and Nt13 regions. The number of fingers in Nt11 is 116, and the period is 0.6838μm. The number of fingers in Nt12 is 15, and the period is 0.6797μm. The number of fingers in Nt13 is 6, and the period is 0.6797μm. The energy trap is divided into Nrt11 and Nrt12 regions. The number of fingers in Nrt11 is 4, and the period is 0.6924μm. The number of fingers in Nrt12 is 16, and the period is 0.6923μm. The right transducer is divided into Nt21, Nt22 and Nt23 areas. The number of fingers in Nt21 is 22 and the period is 0.679μm. The number of fingers in Nt22 is 16 and the period is 0.686μm. The number of fingers in Nt23 is 11 and the period is 0.6867μm. The right reflector is divided into Nr21 and Nr22 areas. The number of fingers in Nr21 is 75 and the period is 0.694μm. The number of fingers in Nr22 is 200 and the period is 0.695μm.

[0079] The electrical performance test results of the low-loss high-frequency surface acoustic wave filter provided in the example are as follows: Figure 5 and Figure 6 As shown, the electrical performance test was carried out using a vector network analyzer under SPAN: 50MHz and 200MHz conditions. The results showed that when the center frequency of the low-loss high-frequency surface acoustic wave filter was 1.8GHz, the -1dB bandwidth was 486KHz and the insertion loss was 5.66dB.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A low-loss high-frequency surface acoustic wave filter, characterized in that: include: substrate; An interdigital electrode is located on the surface of the substrate; the interdigital electrode comprises a first interdigital module and a second interdigital module connected in parallel; The first interdigital module comprises a first left reflection grid, a first left transducer, a first energy trap, a first right transducer and a first right reflection grid which are arranged in sequence; The second interdigital module includes a second left reflection grid, a second left transducer, a second energy trap, a second right transducer and a second right reflection grid which are arranged in sequence; The first left transducer is connected to the second left transducer; The first right transducer is connected to the second right transducer; The apertures of the first interdigital module and the second interdigital module are both W, W<70 wavelengths, and the aperture of the interdigital electrode is W / 2.

2. The low-loss high-frequency surface acoustic wave filter according to claim 1, characterized in that: The material of the substrate is 36°AT quartz; The material of the interdigital electrodes is aluminum-copper alloy, wherein the copper content is 2%; The thickness of the interdigital electrodes is not less than 90 nm.

3. The low-loss high-frequency surface acoustic wave filter according to claim 1, characterized in that: The first interdigital module and the second interdigital module have the same structure.

4. The low-loss high-frequency surface acoustic wave filter according to claim 3, characterized in that: The components of the first interdigital module and the second interdigital module are configured with periods and numbers of interdigits or fingers in a partitioned manner.

5. The low-loss high-frequency surface acoustic wave filter according to claim 4, characterized in that: The left transducer and the right transducer are divided into two or more regions, and the number of fingers in the region far away from the energy trap is less than 20.

6. The low-loss high-frequency surface acoustic wave filter according to claim 5, characterized in that: The left transducer is divided into three areas, namely Nt11 area, Nt12 area and Nt13 area. The number of interdigital roots in Nt12 area is 15, and the number of interdigital roots in Nt13 area is 6. The right transducer is divided into three areas, namely, Nt21 area, Nt22 area and Nt23 area. The number of interdigital roots in Nt22 area is 16, and the number of interdigital roots in Nt23 area is 11.

7. The low-loss high-frequency surface acoustic wave filter according to claim 6, characterized in that: The number of fingers in the Nt11 region is 116, and the period is 0.6838μm; the number of fingers in the Nt12 region is 15, and the period is 0.6797μm; the number of fingers in the Nt13 region is 6, and the period is 0.6797μm. The number of fingers in the Nt21 region is 22, and the period is 0.679μm; the number of fingers in the Nt22 region is 16, and the period is 0.686μm; the number of fingers in the Nt23 region is 11, and the period is 0.6867μm.

8. The low-loss high-frequency surface acoustic wave filter according to claim 4, characterized in that: The left reflective grid, energy trap, and right reflective grid are divided into two areas; The left reflector is divided into Nr11 and Nr12 regions. The number of fingers in Nr11 region is 69, and the period is 0.695μm. The number of fingers in Nr12 region is 250, and the period is 0.6945μm. The energy trap is divided into Nrt11 and Nrt12 regions. The number of fingers in Nrt11 region is 4, and the period is 0.6924μm. The number of fingers in Nrt12 region is 16, and the period is 0.6923μm. The right reflection grating is divided into Nr21 zone and Nr22 zone. The number of fingers in Nr21 zone is 75 and the period is 0.694μm; the number of fingers in Nr22 zone is 200 and the period is 0.695μm.

9. The low-loss high-frequency surface acoustic wave filter according to claim 4, characterized in that: In the first interdigital module and the second interdigital module, the distance between the energy trap and the transducer is less than 0.7 times of the period of the transducer region adjacent to the energy trap.

10. The low-loss high-frequency surface acoustic wave filter according to any one of claims 1 to 9, characterized in that: The first interdigital module and the second interdigital module can share the same reflective grating.

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