A rayleigh wave filter based on a mirror-symmetrical structure

Abstract

The application provides a Rayleigh wave filter based on a mirror symmetry structure, which belongs to the technical field of filters and comprises a flat plate device A with an upper boundary and a lower boundary of the flat plate being set as an anti-symmetrical periodic rectangular ripple arrangement, a flat plate device B obtained by performing 180 mirror mapping on the flat plate device A with a y axis as a central axis, and a rectangular flat plate device C; the structure of the flat plate device A and the structure of the flat plate device B are mirror symmetry arrangement with each other, and the periodic number of the flat plate device A and the flat plate device B can be adjusted according to the filtering effect. The Rayleigh wave filter based on the mirror symmetry structure has the advantages of simple structure, low cost, easy implementation, good filtering performance, strong stability and sustainable effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of filters, and particularly relates to a Rayleigh wave filter based on a mirror-symmetrical structure. BACKGROUND

[0002] Rayleigh waves have the characteristics of slow attenuation, strong stability, reflection and transmission in rock layers, and are often used in geological exploration problems. In the mid-1980s, Rayleigh wave method was used in geological survey technology in China. After decades of research and development, good results have been achieved. Due to the frequency dispersion phenomenon of Rayleigh waves in layered media, Rayleigh waves can also be effectively used in rock integrity evaluation, dam hazard prediction, soil classification and other aspects.

[0003] Rayleigh wave devices are widely used in various scientific fields and engineering applications. In micro-scale acoustic fluidics, Rayleigh waves are used to affect chemical and physical properties present in fluids or particles. Rayleigh waves are also used in intermediate frequency and radio frequency filters, which are called Rayleigh wave filters, and are widely used due to their simplicity, low cost and effectiveness. Rayleigh waves are also used in radio frequency identification (RFID) tags. In particular, passive RFID tags using Rayleigh waves have been proven to be durable, robust and able to return stronger signals compared to other integrated circuit RFID tags.

[0004] Rayleigh waves are also implemented in the field of structural health monitoring (SHM) and non-destructive evaluation (NDE). In structural health monitoring (SHM) and non-destructive evaluation (NDE) applications, Rayleigh waves are used to remotely detect potential structural damage in hard-to-reach locations. The inherent spatial hopping phenomenon of Rayleigh waves is also used to avoid obstacles or investigate surfaces that cannot be normally accessed.

[0005] With the development of technology, the requirements for Rayleigh waves in complex environments in the field of engineering applications are becoming higher and higher. The echo signal of Rayleigh waves itself is weak, and the influence of noise makes it more difficult to identify effective information. Therefore, how to effectively realize signal extraction and filter out noise has become a key problem in current research. SUMMARY

[0006] Based on the problems existing in the prior art, the Rayleigh wave filter based on the mirror-symmetrical structure solves the problem that the existing Rayleigh wave device is deficient in frequency band regulation and bidirectional conduction, and has the characteristics of strong filtering ability, high transmittance, simple structure, no need for packaging, etc. The Rayleigh wave filter based on the mirror-symmetrical structure can realize frequency band adjustment and bidirectional conduction functions.

[0007] According to the technical scheme of the application, the Rayleigh wave filter based on the mirror image symmetry structure comprises a flat plate device A with the upper boundary and the lower boundary of the flat plate being set as the anti-symmetrical periodic rectangular wave arrangement, a flat plate device B obtained by 180° mirror image mapping of the flat plate device A with the y axis as the central axis, and a rectangular flat plate device C.

[0008] Preferably, the flat plate device A structure and the flat plate device B structure are mirror image symmetrical arrangement, and the periodic number of the flat plate device A and the flat plate device B can be adjusted according to the filtering effect.

[0009] Further, the rectangular flat plate device C is inserted in the center of the mirror image symmetry structure, and the length l of the rectangular flat plate device C can be adjusted to control the center frequency of the filter.

[0010] Preferably, the flat plate device A structure and the flat plate device B structure have a groove depth e in the range of 0 < e < d1 / 2, and the maximum value of the groove depth depends on half of the minimum thickness d1 / 2.

[0011] More preferably, the ratio of the periodic length Lambda and the average thickness d of the first periodic structure of the flat plate device A can be changed according to the working performance of the filter.

[0012] Further, the filtering frequency band of the filter can be adjusted by scaling up or down according to the entire filter structure.

[0013] Further, the flat plate device A, the flat plate device B and the flat plate device C are seamless and made of the same material.

[0014] Preferably, the filter has no directional difference, that is, the Rayleigh wave can be incident from the left end and received from the right end, and the Rayleigh wave can be incident from the right end and received from the left end, and the filtering effect is the same.

[0015] More preferably, the ratio of the periodic length Lambda and the average thickness d is 3:2. Increasing or decreasing the ratio of the periodic length Lambda and the average thickness d can increase the bandwidth of the filter passband, but the transmittance will also decrease

[0016] Compared with the prior art, the Rayleigh wave filter based on the mirror image symmetry structure has the following beneficial technical effects:

[0017] 1. The Rayleigh wave filter based on the mirror image symmetry structure has simple structure, low cost and easy implementation.

[0018] 2. The Rayleigh wave filter based on the mirror image symmetry structure has good filtering performance, strong stability and sustainable effect.

[0019] 3. The Rayleigh wave filter based on the mirror image symmetry structure has controllable center frequency.

[0020] 4、The Rayleigh wave filter based on the mirror symmetry structure can adjust and control the filtering frequency band.

[0021] 5、The Rayleigh wave filter based on the mirror symmetry structure has bidirectional conduction property, and there is no difference between the use directions. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural plane analysis diagram of the Rayleigh wave filter based on the mirror symmetry structure;

[0023] The period length of the flat device A and the flat device B is Λ, the minimum thickness is d1, the maximum thickness is d2, l is the length of the rectangular flat device C, and e is the groove depth of the period rectangular ripple arrangement.

[0024] A represents the flat device A, B represents the flat device B, and C represents the flat device C.

[0025] Figure 2 is Figure 1 When the period number of the flat device A and the flat device B in the filter is 5, the length l of the flat device C is changed to adjust and control the center frequency of the filter.

[0026] Figure 3 is Figure 1 When the length l of the flat device C in the filter is 0 mm, the period number of the flat device A and the flat device B is adjusted to control the bandwidth of the filter. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] In addition, it should be further noted that only the parts related to the present application are shown in the drawings for convenience of description. In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0029] It should be noted that the concepts of "first", "second" and the like mentioned in the present application are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0030] It should be noted that the modification of "one" and "multiple" mentioned in the present application is illustrative rather than restrictive, and those skilled in the art should understand that "one or more" should be understood unless otherwise explicitly indicated in the context.

[0031] The present application provides a Rayleigh wave filter based on mirror-symmetry structure, which comprises a mirror-symmetry structure filter composed of a flat plate device A with its upper boundary and lower boundary set as anti-symmetry periodic rectangular wave arrangement, a flat plate device B obtained by 180° mirror mapping of the flat plate device A with y-axis as the central axis, and a rectangular flat plate device C, and the mirror-symmetry structure filter realizes signal filtering of Rayleigh wave at a specific center frequency.

[0032] The flat plate device A structure and the flat plate device B structure are arranged in mirror symmetry with each other, and the number of periods of the flat plate device A and the flat plate device B can be adjusted according to the filtering effect. The rectangular flat plate device C is inserted in the center of the mirror-symmetry structure, and the length l of the rectangular flat plate device C can be adjusted to achieve the purpose of controlling the center frequency of the filter.

[0033] More preferably, the flat plate device A structure and the flat plate device B structure have a groove depth e in the range of 0 < e < d1 / 2, and the maximum value of the groove depth depends on half of the minimum thickness of the structure d1 / 2. The ratio of the period length Λ to the average thickness d can be adjusted to adjust the working performance of the filter. The working frequency band of the filter can be adjusted according to the proportional scaling of the entire filter structure. In the preferred embodiment of the present application, the ratio of the period length Λ to the average thickness d is 3:2, and the working frequency band of the filter is 0.633MHz-0.896MHz. Increasing or decreasing the ratio of the period length Λ to the average thickness d can increase the bandwidth of the passband of the filter, but at the same time the transmittance will also be smaller; when the entire filter structure is scaled up, the working frequency band will be proportionally reduced accordingly.

[0034] In addition, the flat plate device A, the flat plate device B and the flat plate device C are seamless and made of the same material, which can be designed as aluminum, copper or alloy materials according to needs. Since the present application is designed as a mirror-symmetry structure, the filter has a bidirectional conduction property, and there is no difference in use direction, i.e. Rayleigh wave can be incident from the left end and received at the right end, and Rayleigh wave can be incident from the right end and received at the left end, and the filtering effect is the same.

[0035] This invention provides a Rayleigh wave filter based on a mirror-symmetric structure, utilizing a mode resonance phenomenon with Rayleigh wave physical characteristics. When a Rayleigh wave passes through a structure with a periodic rippled boundary condition, resonance between different transverse modes or between the same transverse modes creates a bandgap. When the periodic planar devices A and B are used individually, they only generate a bandgap. However, when they are connected, a very narrow passband is generated within their overlapping bandgap, thus achieving the function of a filter. This passband is generated because the integrity of the periodic structure of the two periodically arranged waveguides is disrupted by composing them with opposite periodic arrangements, causing local resonance at the center of the structure and producing a very narrow passband.

[0036] The Rayleigh wave filter based on a mirror-symmetric structure of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, the Rayleigh wave filter based on a mirror-symmetric structure includes three planar devices (planar device A, planar device B, and planar device C), which are connected together to form a mirror-symmetric structure device.

[0038] In this design, the upper and lower boundaries of the flat plate device A are arranged in an anti-symmetric, periodic rectangular ripple pattern. The flat plate device A consists of multiple flat plate components, each with an irregular rectangular shape. The left and right boundaries of each flat plate component are parallel and perpendicular to each other. The upper and lower boundaries of each flat plate component are also arranged in an anti-symmetric, periodic rectangular ripple pattern. It is a zigzag shape, where the groove depth (height difference) between the upper and lower horizontal lines is e; the lengths of the upper and lower boundaries are the period length Λ.

[0039] Flat panel device A and flat panel device B are connected to form a mirror-symmetric structure. That is, flat panel device B is a structure obtained by mirroring flat panel device A 180° with the y-axis as the central axis. Flat panel device B is also composed of multiple flat panel components. The number of flat panel components constituting flat panel device B is the same as the number of flat panel components constituting flat panel device A. However, the shapes of the flat panel components constituting flat panel device B are axially symmetric to the shapes of the flat panel components constituting flat panel device A.

[0040] A plate device C is provided between plate device A and plate device B. Plate device C is rectangular in shape. The long sides (left and right boundaries) of plate device C are the same length as the left and right boundaries of plate device A and plate device B. The left boundary of plate device C is at the same horizontal level as the right boundary of plate device A and is closely connected. The right boundary of plate device C is at the same horizontal level as the left boundary of plate device B and is closely connected.

[0041] When the Rayleigh wave is incident along the x-axis into the mirror-symmetry structure-based Rayleigh wave filter, the mirror-symmetry structure-based Rayleigh wave filter produces a filtering effect. By inserting a rectangular plate device C in the center of the mirror-symmetry device structure, the length l of the rectangular plate device C can be adjusted to achieve the purpose of regulating the center frequency of the filter.

[0042] Further, in the preferred embodiment of the present application, the number of periods of the two periodically undulating plate devices A and B is 5, the period length of the plate device A is Λ = 2 mm, the minimum thickness of the plate device A is d1 = 3 mm, the maximum thickness of the plate device A is d2 = 3.3 mm, and the groove depth of the periodic rectangular wave arrangement of the plate device A is e = 0.3 mm (e is the maximum thickness minus the minimum thickness, i.e., d2 - d1); the plate device B has the same period length, thickness, and groove depth as the plate device A. The overall structure of the plate device A and the plate device B is made of pure aluminum or aluminum alloy by integral molding. For the plate device C, it is a rectangular structure with the same minimum height as the plate device A connected to the plate device A, and the lateral length l is 0.2 mm and 0.4 mm in the preferred embodiment, respectively.

[0043] Further, when the Rayleigh wave passes through a structure with a periodic wave arrangement boundary condition, resonance occurs between different transverse modes of the wave, resulting in a forbidden band. When the periodic plate device A and the plate device B are used alone, only a forbidden band can be produced, but the combination of the two periodic arrangement opposite devices destroys the integrity of the two periodic structures, causing local resonance at the center of the structure, resulting in a very narrow passband in the center of the forbidden band. By inserting the rectangular plate device C at the connection between the plate device A and the plate device B, the purpose is to regulate the center frequency of the passband.

[0044] As shown in Figure 2 When the Rayleigh wave acts alone in the mirror-symmetry structure composed of the plate device A and the plate device B (i.e., the waveguide C length l = 0 mm), the center frequency of the passband is 0.762 MHz, and the transmittance is 95.9%; when the length l of the plate device C is increased from 0.2 mm to 0.4 mm, the center frequency of the passband moves from 0.745 MHz to 0.729 MHz, and the transmittance is always higher than 92.5%.

[0045] As shown in Figure 3As shown, by changing the period number N of the flat device A and the flat device B, the bandwidth of the filter passband can be adjusted, and the period number from right to left is 3, 4, 5, respectively, the -3dB bandwidth of the passband is 0.744MHz-0.780MHz, 0.754MHz-0.768MHz, 0.758MHz-0.764MHz, the center frequency is always at 0.762MHz, and the transmittance is higher than 92.5%. By increasing the period number of the flat device A and the flat device B, the bandwidth of the filter passband can be narrowed, thereby achieving the purpose of adjustable bandwidth.

[0046] In the implementation process of the Rayleigh wave filter based on the mirror-symmetry structure, the period length, the overall structure ratio, the period number and other parameters can be designed according to the resonance principle and the actual filtering effect.

[0047] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A Rayleigh wave filter based on a mirror-symmetrical structure, characterized in that, It includes a flat plate device A with its upper and lower boundaries arranged in a periodic rectangular wave pattern in an anti-symmetrical manner, a flat plate device B obtained by 180° mirror mapping of the flat plate device A with the y-axis as the central axis, and a rectangular flat plate device C, which are connected together to form a mirror-symmetrical structure device; The flat plate device A structure and the flat plate device B structure are arranged in a mirror-symmetrical manner, and the number of periods of the flat plate device A and the flat plate device B can be adjusted according to the filtering effect; The rectangular flat plate device C is inserted in the center of the mirror-symmetrical structure, and the length l of the rectangular flat plate device C can be adjusted to control the center frequency of the filter; The flat plate device A is composed of a plurality of flat plate pieces, each of which is irregularly rectangular in shape, the left side boundary of the flat plate piece is parallel to the right side boundary of the flat plate piece and is arranged vertically, the upper boundary of the flat plate piece and the lower boundary of the flat plate piece are both arranged in a zigzag shape Zigzag shape The filter has a bidirectional conduction property, and there is no difference between the use directions, i.e., the Rayleigh wave can be incident from the left end and received from the right end, or the Rayleigh wave can be incident from the right end and received from the left end, and the filtering effects are equivalent.

2. The Rayleigh wave filter based on the mirror-symmetrical structure according to claim 1, characterized in that, The groove depth e of the flat plate device A structure and the flat plate device B structure is in the range of 0<e<d1 / 2, and the maximum value of the groove depth depends on half of the minimum thickness d1 / 2.

3. The Rayleigh wave filter based on the mirror-symmetrical structure according to claim 2, characterized in that, The ratio of the period length Λ to the average thickness d of the first period structure of the flat plate device A can be changed according to the working performance of the filter.

4. The Rayleigh wave filter based on the mirror-symmetrical structure according to claim 1, characterized in that, The filtering frequency band of the filter can be adjusted by scaling up or down the entire filter structure.

5. The Rayleigh wave filter based on the mirror-symmetrical structure according to claim 4, characterized in that, The flat plate device A, the flat plate device B and the flat plate device C are seamless and made of the same material.

6. The Rayleigh wave filter based on the mirror-symmetrical structure according to claim 3, characterized in that, The ratio of the period length Λ to the average thickness d is 3:

2.

7. The Rayleigh wave filter based on a mirror-symmetrical structure according to claim 6, characterized in that, Increasing or decreasing the ratio of the period length Λ to the average thickness d can increase the bandwidth of the filter passband, but at the same time, the transmittance will also decrease.

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