Wave absorber and preparation method thereof

Abstract

The present application discloses an absorber, a method for preparing the absorber, and a radio frequency identification system. The absorber includes: at least one metal patch and at least one resistor film, a dielectric layer and a metal base plate; the metal patch includes: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in a ring shape inside the annular metal sheet; the metal patch covers the surface of the dielectric layer, the resistor film is joined with the plurality of petal-shaped metal sheets to form electrical connection, and the back of the dielectric layer is attached to the metal base plate. When the electromagnetic wave in the UHF band is incident obliquely to the absorber at a large angle, it first contacts the metal patch layer, and the outer annular metal sheet and the inner plurality of petal-shaped metal sheets in the pattern layer generate strong electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer and the metal base plate, where most of the electromagnetic wave energy is consumed. Therefore, the absorber has the advantages of a wide UHF band absorbing bandwidth, high absorbing performance at large-angle oblique incidence, and small size.

Description

Technical Field

[0001] The present application relates to the technical field of microwave devices, and in particular to an absorber and a method for preparing the absorber. Background Art

[0002] Radio Frequency Identification (RFID) technology is a key technology for object identification in the Internet of Things. When RFID systems are used in practical applications, especially in indoor environments, problems such as misidentification of tags will arise due to multiple reflection interference in the indoor wireless communication environment. This interference needs to be controlled to improve the wireless communication environment, especially the multipath effect, so as to establish a reliable RFID system. In practical applications, absorbing materials are mainly used to absorb electromagnetic waves reflected in the environment around the RFID system.

[0003] Taking the RFID system working in the US standard frequency band (902-928MHz) as an example, the size and thickness of traditional absorbing materials (such as wedge-shaped sponge absorbing materials) in this frequency band are relatively large and thick compared to the wavelength. At present, a commonly used absorber based on the UHF frequency band is a narrow-band metamaterial absorber, which has a higher absorption rate in the RFID system working frequency band of 865-868MHz.

[0004] However, in the process of implementing the present invention, the inventors found that the above narrowband metamaterial absorber has at least the following problems: 1) The absorber unit size is large; 2) The relative bandwidth is only 0.3%, and the frequency band with high absorption rate is extremely narrow; 3) It is sensitive to large-angle oblique incidence, which limits its practical application in RFID systems. In summary, how to design a smaller absorber to absorb unnecessary electromagnetic waves in the surrounding environment, improve the electromagnetic environment around the RFID system, improve the tag recognition efficiency, and make the RFID system run stably and reliably in an indoor environment has become a problem that technicians in this field need to solve urgently. Summary of the invention

[0005] The present application provides an absorber to solve the problems of narrow UHF band absorption bandwidth, poor absorption performance at large angle incident, and large size in the prior art. The present application also provides a method for preparing the absorber and a radio frequency identification system.

[0006] The present application provides a wave absorber, comprising:

[0007] At least one metal patch and at least one resistor film, a dielectric layer and a metal base plate;

[0008] The metal patch includes: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in an annular shape inside the annular metal sheet;

[0009] The metal patch covers the surface of the dielectric layer, the resistor film is connected with a plurality of petal-shaped metal patches to form electrical communication, and the back side of the dielectric layer is attached to the metal bottom plate.

[0010] Optionally, the pattern of the metal patch is centrally symmetrical.

[0011] Optionally, the metal patch is a metal patch made of a metasurface material.

[0012] Optionally, the annular metal sheet includes: a circular annular metal sheet, or a square annular metal sheet.

[0013] Optionally, the plurality of petal-shaped metal sheets are equidistant and discrete.

[0014] Optionally, the resistor film includes: a square resistor film, or a circular resistor film.

[0015] Optionally, the dielectric layer includes: a dielectric layer whose flame retardant material grade is FR4.

[0016] Optionally, the at least one metal patch is periodically covered on the surface of the dielectric layer.

[0017] The present application also provides a method for preparing an absorber, comprising:

[0018] The metal patch is covered on the surface of the dielectric layer by a metal etching process, wherein the metal patch comprises: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in an annular shape inside the annular metal sheet;

[0019] Joining the resistive film to the plurality of petal-shaped metal sheets to establish electrical communication;

[0020] The back side of the dielectric layer is attached to the metal bottom plate.

[0021] The present application also provides a radio frequency identification system, comprising:

[0022] An absorber according to any of the above.

[0023] Compared with the prior art, this application has the following advantages:

[0024] The absorber provided by the embodiment of the present application covers the surface of the dielectric layer with a metal patch of an orange-like pattern, and the resistor film is connected with multiple petal-shaped metal patches in the metal patch to form electrical communication. The back of the dielectric layer is attached to the metal base plate. The array arrangement of the metal patch of the orange-like pattern and the resistor film change the parameters such as the shape and size of the sub-wavelength unit. When the electromagnetic wave is obliquely incident on the absorber, it first contacts the orange-like pattern layer. The outer annular metal sheet and the inner multiple petal-shaped metal sheets in the pattern layer produce strong electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer and the metal base plate. Most of the electromagnetic wave energy is consumed here. At the same time, in the process of the surface electromagnetic resonance induced current flowing through the resistor film, part of the electromagnetic energy flow is converted into heat flow and consumed, and adjacent frequencies are superimposed on each other, thereby realizing the working state of large-angle wave absorption in the UHF band. It can be seen that the absorber provided in this embodiment has excellent absorbing performance at large-angle oblique incidence, and the absorbing bandwidth is wide, such as covering the UHF frequency band of the American standard 902-928MHz, or covering the UHF frequency band of the Chinese standard 920-925MHz. Therefore, it can effectively control the electromagnetic interference of the surrounding environment, thereby improving the wireless communication environment, especially improving the multipath effect problem.

[0025] The absorber preparation method provided in the embodiment of the present application relies on the resonance of the metal patch and the loss of the resistor film, utilizes the low-cost resistor film material and the mature metal etching process, reduces the production cost, and realizes large-scale production. The absorbing frequency band can cover a wider UHF frequency band, such as the UHF frequency band of the American standard 902-928 MHz, laying a solid foundation for the large-scale application of the absorber in radio frequency circuits and the like.

[0026] The radio frequency identification system provided in the embodiment of the present application includes the above-mentioned absorber. Since the absorber can effectively improve the electromagnetic environment around the RFID system, it can effectively improve the tag recognition efficiency, so that the RFID system can operate stably and reliably in an indoor environment.

[0027] The communication system provided in the embodiment of the present application includes the above-mentioned absorber. Since the absorber can effectively improve the electromagnetic environment around the communication system, the reliability of the communication system can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of an embodiment of the absorber provided in the present application;

[0029] Figure 2 A schematic structural diagram of a metal patch of an embodiment of an absorber provided by the present application;

[0030] Figure 3 A schematic diagram of the distribution of the wave absorption rate of the wave absorber according to the embodiment of the present application;

[0031] Figure 4 Schematic diagram of the wave absorption rate characteristics of an embodiment of the wave absorber provided in the present application. DETAILED DESCRIPTION

[0032] Many specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application, so the present application is not limited by the specific implementation disclosed below.

[0033] In the present application, a wave absorber and a preparation method thereof, a radio frequency identification system, and a communication system are provided. In the following embodiments, various schemes are described in detail one by one.

[0034] First embodiment

[0035] Please refer to Figure 1 , which is a schematic diagram of the structure of an embodiment of the absorber of the present application. In this embodiment, the absorber includes: at least one metal patch, the metal patch includes: an annular metal sheet 1 located on the outer layer, and a plurality of petal-shaped metal sheets 2 placed in a ring shape inside the annular metal sheet 1. The absorber also includes: at least one resistor film 3, a dielectric layer 4 and a metal bottom plate 5.

[0036] The metal patch, the resistor film 3, the dielectric layer 4 and the metal bottom plate 5 are arranged in sequence from top to bottom. The metal patch and the resistor film 3 constitute the absorber surface structure. The metal patch covers the surface of the dielectric layer 4, and the resistor film 3 can be placed in the metal patch and connected with the multiple petal-shaped metal patches 2 to form electrical communication. The back of the dielectric layer 4 is attached to the metal bottom plate 5.

[0037] It should be noted that, for the convenience of distinction, Figure 1 There is a certain distance between different hierarchical structures. In fact, the metal patch, the resistor film 3, the dielectric layer 4 and the metal base plate 5 are closely attached to each other.

[0038] The pattern of the metal patch includes an annular pattern with a certain width and a plurality of petal patterns. In specific implementation, the annular pattern of the metal patch can be a circular annular pattern, a square annular pattern, or an irregular annular pattern, such as a wavy annular pattern. The petal pattern of the metal patch can be a triangular pattern similar to the horizontal planing surface of an orange petal, or a petal pattern of other shapes such as a flower petal. The plurality of petal-shaped metal sheets 2 can be composed of a plurality of equidistant and discrete petal-shaped metal sheets.

[0039] The metal patch can be made of general metal materials, such as copper, iron and other metal materials. The metal patch can also be made of flexible materials such as metasurfaces, such as graphene metamaterials. As a two-dimensional metamaterial, the metasurface has lightweight and convenient physical properties. By changing the shape, size and other parameters of the subwavelength unit, the expected reflection or transmission value can be obtained, and then various functional devices can be formed through different array arrangements. This embodiment realizes a UHF band and wide-angle absorber through the array arrangement of the orange-like pattern adopted by the metal patch.

[0040] In one example, the absorber is laid in the surrounding environment of the radio frequency identification system, and a metal patch of a metasurface material is used, so that the absorber can be changed from rigid to flexible, which is more conducive to on-site laying. In specific implementation, a metal etching process can be used to evenly etch a copper metal patch with a thickness of 35 μm on the surface of the dielectric layer 4. In addition, since the thickness of the metasurface is less than the wavelength and the metasurface has lightweight and convenient physical properties, the absorber is small in size and simple in structure.

[0041] The resistor film 3 can be placed at any position in the metal patch, as long as it is electrically connected with the plurality of petal-shaped metal sheets. For example, the resistor film 3 is placed at the center of the metal patch, and the edge of the resistor film 3 is electrically connected with the plurality of petal-shaped metal sheets 2. The resistor film 3 can be a square resistor film, a circular resistor film, or a resistor film of other shapes.

[0042] In one example, the pattern of the metal patch is centrally symmetrical, and the resistor film is centrally symmetrically distributed along the periodic structure of the multiple metal patches, and is evenly attached to the surface of the dielectric layer 4. This can achieve insensitivity to the polarization of the incident electromagnetic wave, absorb unnecessary electromagnetic waves scattered on various paths, and ensure that the absorber is insensitive to polarization.

[0043] The back of the dielectric layer 4 can be evenly covered with a metal base plate 5. In specific implementation, a plurality of metal patches can be covered on the dielectric layer 4, and the period of the metal patches is P. The dielectric layer 4 can be made of FR4 heat-resistant grade dielectric material, such as glass fiber epoxy resin, and its thickness can be millisecond level.

[0044] Figure 2 It is a structural diagram of the metal patch in the absorber provided in this embodiment. In this embodiment, the number of petal-shaped metal patches 2 is 12, the square resistance of the square resistor film 3 is 5Ω / sq, the period of the metal patch is P (such as the period P is in milliseconds), the radius of the petal-shaped metal patch 2 is R1, the inner ring radius of the annular metal patch 1 is R2, the outer ring radius of the annular metal patch 1 is R3, and the side length of the square resistor film 3 is R4. They are symmetrically distributed along the center of the metal patch periodic structure and are evenly attached to the surface center of the dielectric layer 4.

[0045] The absorber provided by the embodiment of the present application covers the surface of the dielectric layer 4 with a metal patch of an orange-like pattern, the resistor film 3 is joined with a plurality of petal-shaped metal sheets 2 to form electrical communication, and the dielectric layer 4 is attached to the metal base plate 5. The array arrangement of the metal patch of the orange-like pattern and the combination of the resistor film change the parameters such as the shape and size of the subwavelength unit. When the electromagnetic wave is obliquely incident on the absorber, it first contacts the orange-like pattern layer. The outer annular metal sheet 1 and the inner petal-shaped metal sheet 2 in the pattern layer produce strong electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer 4 and the metal base plate 5, where most of the electromagnetic wave energy is consumed. At the same time, in the process of the surface electromagnetic resonance induced current flowing through the resistor film 3, part of the electromagnetic energy flow is converted into heat flow and consumed, and adjacent frequencies are superimposed on each other, thereby realizing the working state of large-angle wave absorption in the 902-928MHz frequency band.

[0046] Figure 3 This is the distribution of the absorption rate with frequency when electromagnetic waves of different polarization modes are incident obliquely on the absorber. As can be seen from the figure, in the transverse electric polarization mode (E polarization wave, also called TE wave), when the incident angle is 0-50°, the absorption rate is above 90% in the 902-928MHz frequency band, and the absorption performance is excellent; in the transverse magnetic polarization mode (H polarization wave, also called TM wave), when the incident angle is 0-50°, the absorption rate is above 90% in the 902-928MHz frequency band, and the absorption performance is excellent, covering the American standard UHF frequency band. In summary, when electromagnetic waves of different polarization modes are incident obliquely on the absorber, when the incident angle does not exceed 50°, the absorption rate is above 90% in the 902-928MHz frequency band, thereby realizing a UHF band, wide angle, and polarization-insensitive absorber.

[0047] Figure 4 is the wave absorption rate characteristic of the metal patch when the wave absorber provided by this embodiment absorbs vertically incident and large-angle incident electromagnetic waves. Figure 4 a and Figure 4 b It can be seen that: 1. When the electromagnetic wave is incident vertically, the reflection coefficient S11 of the absorber is lower than 10dB in the frequency range of 892MHz-916MHz, and the corresponding absorption rate A(f) exceeds 90%, realizing good absorption of electromagnetic waves by the absorber in the frequency band of 902MHz-928MHz; 2. When the electromagnetic wave is incident obliquely at a large angle, the reflection coefficient S11 of the absorber is lower than 10dB in the frequency range of 904MHz-926MHz, and the corresponding absorption rate A(f) exceeds 90%, thus realizing a UHF band, wide-angle, polarization-insensitive absorber.

[0048] It can be seen from the above embodiments that the absorber provided by the embodiment of the present application covers the metal patch with an orange-like pattern on the surface of the dielectric layer, and the resistor film is connected to the multiple petal-shaped metal patches in the metal patch to form an electrical connection. The back of the dielectric layer is attached to the metal base plate. The array arrangement of the metal patch with an orange-like pattern and the resistor film change the shape, size and other parameters of the sub-wavelength unit. When the electromagnetic wave is obliquely incident on the absorber, it first contacts the orange-like pattern layer. The outer annular metal sheet and the inner multiple petal-shaped metal sheets in the pattern layer produce strong electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer and the metal base plate. Most of the electromagnetic wave energy is consumed here. At the same time, in the process of the surface electromagnetic resonance induced current flowing through the resistor film, part of the electromagnetic energy flow is converted into heat flow and consumed, and adjacent frequencies are superimposed on each other, thereby realizing the working state of large-angle absorption in the UHF band. It can be seen that the absorber provided in this embodiment has excellent absorbing performance at large-angle oblique incidence, and the absorbing bandwidth is wide, such as covering the UHF frequency band of the American standard 902-928MHz, or covering the UHF frequency band of the Chinese standard 920-925MHz. Therefore, it can effectively control the electromagnetic interference of the surrounding environment, thereby improving the wireless communication environment, especially improving the multipath effect problem.

[0049] Second embodiment

[0050] In the above-mentioned embodiment, an absorber is provided, and correspondingly, the present application also provides a method for preparing the absorber. The method corresponds to the embodiment of the above-mentioned product. Since the method embodiment is basically similar to the product embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the product embodiment. The method embodiment described below is only illustrative.

[0051] The present application further provides a method for preparing an absorber, comprising:

[0052] Step 1: Covering the surface of the dielectric layer with a metal patch by a metal etching process, wherein the metal patch includes: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in an annular shape inside the annular metal sheet;

[0053] Step 2: Joining the resistive film and the plurality of petal-shaped metal sheets to form electrical communication;

[0054] Step 3: Lay the back side of the dielectric layer on the metal base plate.

[0055] It can be seen from the above embodiments that the absorber preparation method provided in the embodiments of the present application relies on the resonance of the metal patch and the loss of the resistor film, utilizes the low-cost resistor film material and the mature metal etching process, reduces the production cost, and realizes large-scale production. The absorbing frequency band can cover a wider UHF frequency band, such as the UHF frequency band of the American standard 902-928MHz, laying a solid foundation for the large-scale application of absorbers in radio frequency circuits, etc.

[0056] Third embodiment

[0057] In the above-mentioned embodiment, an absorber is provided, and correspondingly, the present application also provides a radio frequency identification system. The radio frequency identification system corresponds to the above-mentioned absorber embodiment. Since the system embodiment is basically similar to the product embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the product embodiment. The system embodiment described below is only illustrative.

[0058] The present application further provides a radio frequency identification system, including: the above-mentioned absorber, in addition to an RFID reader, and an electronic tag. RFID reader, that is, radio frequency identification technology, this technology is usually used for wireless transceiver. RFID readers are widely used in various fields, such as: manufacturing, logistics, ports, docks, vehicle and personnel management, etc. The RFID reader consists of several parts: a real-time processor, an operating system, a virtual mobile memory and a small built-in module (containing a transceiver). The electronic tag, that is, the RFID tag, is a contactless automatic identification technology that uses radio frequency signals to identify the target object and obtain relevant data.

[0059] In this embodiment, multiple absorbers can be set in the surrounding environment of the radio frequency identification system, and each absorber can be covered with multiple metal patches. This can effectively absorb unnecessary electromagnetic waves in the surrounding environment, improve the electromagnetic environment around the RFID system, improve the tag recognition efficiency, and enable the RFID system to operate stably and reliably in an indoor environment.

[0060] Fourth embodiment

[0061] In the above-mentioned embodiment, an absorber is provided, and correspondingly, the present application also provides a communication system. The communication system corresponds to the embodiment of the absorber. Since the system embodiment is basically similar to the product embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the product embodiment. The system embodiment described below is only illustrative.

[0062] The present application further provides a communication system, including: the above-mentioned absorber, and also includes equipment such as an antenna.

[0063] In this embodiment, multiple absorbers can be set in the environment around the communication system, and each absorber can be covered with multiple metal patches, which can effectively absorb unnecessary electromagnetic waves in the surrounding environment, improve the electromagnetic environment around the communication system, and enhance the reliability of the communication system.

[0064] Although the present application is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present application. Any technical personnel in this field may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A wave absorber, characterized in that: include: At least one metal patch and at least one resistor film, a dielectric layer and a metal base plate, each metal patch corresponds to a resistor film; The metal patch includes: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in an annular shape inside the annular metal sheet; The metal patch covers the surface of the dielectric layer, the resistor film corresponding to the metal patch is joined with a plurality of petal-shaped metal sheets to form electrical communication, the back side of the dielectric layer is attached to the metal base plate, so that the shape and size parameters of the subwavelength unit can be changed, and when the electromagnetic wave is obliquely incident on the absorber, the annular metal sheet and the plurality of petal-shaped metal sheets generate electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer and the metal base plate to consume most of the electromagnetic wave energy; in the process of the surface electromagnetic resonance induced current flowing through the resistor film, part of the electromagnetic energy flow is converted into heat flow for consumption, and adjacent frequencies are superimposed on each other to achieve UHF band and wide-angle absorption.

2. The absorber according to claim 1, characterized in that: The pattern of the metal patch is centrally symmetrical.

3. The absorber according to claim 1, characterized in that: The metal patch is a metal patch of a super surface material.

4. The absorber according to claim 1, characterized in that: The annular metal sheet includes: a circular annular metal sheet or a square annular metal sheet.

5. The absorber according to claim 1, characterized in that: The plurality of petal-shaped metal sheets are equidistant and discrete from each other.

6. The absorber according to claim 1, characterized in that: The resistor film includes: a square resistor film or a circular resistor film.

7. The absorber according to claim 1, characterized in that: The dielectric layer includes: a dielectric layer whose flame retardant material grade is FR4.

8. The absorber according to claim 1, characterized in that: The at least one metal patch is periodically covered on the surface of the dielectric layer.

9. A method for preparing an absorber, characterized in that: include: The metal patch is covered on the surface of the dielectric layer by a metal etching process, wherein the metal patch comprises: an annular metal sheet, and a plurality of petal-shaped metal sheets placed in an annular shape inside the annular metal sheet; Joining a resistive film to the plurality of petal-shaped metal sheets to establish electrical communication; The back side of the dielectric layer is bonded to the metal base plate, so that the shape and size parameters of the subwavelength unit can be changed. When the electromagnetic wave is incident obliquely on the absorber, the annular metal sheet and the plurality of petal-shaped metal sheets generate electromagnetic resonance at adjacent frequencies, and form a cavity in combination with the dielectric layer and the metal base plate to consume most of the electromagnetic wave energy. In the process of the surface electromagnetic resonance induced current flowing through the resistor film, part of the electromagnetic energy flow is converted into heat flow for consumption, and adjacent frequencies are superimposed on each other to achieve UHF band and wide-angle wave absorption.

10. A radio frequency identification system, characterized in that: include: The absorber according to any one of claims 1 to 8.

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