CN115313060A - Adjustable circularly polarized RFID reader-writer antenna - Google Patents
Adjustable circularly polarized RFID reader-writer antenna Download PDFInfo
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- CN115313060A CN115313060A CN202211243922.6A CN202211243922A CN115313060A CN 115313060 A CN115313060 A CN 115313060A CN 202211243922 A CN202211243922 A CN 202211243922A CN 115313060 A CN115313060 A CN 115313060A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
- H01Q1/2216—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in interrogator/reader equipment
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
- H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/24—Polarising devices; Polarisation filters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
- H01Q5/10—Resonant antennas
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
- H01Q5/30—Arrangements for providing operation on different wavebands
- H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
- H01Q5/314—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors
Abstract
The invention relates to an adjustable circularly polarized RFID reader-writer antenna, which is based on a metal layer (1), a PCB substrate (2), a metal bottom plate (3), a feed probe (4) and at least three metal support rods (5), introduces an electromagnetic metamaterial technology, a cavity mode theory and a frequency reconfigurable design into the design of a circularly polarized antenna, firstly provides an electromagnetic metamaterial resonator of a quasi-air substrate based on an electromagnetic metamaterial and the cavity mode theory, reduces the dielectric loss and obtains high radiation efficiency while realizing miniaturization and low cost; then the electromagnetic metamaterial resonator is used in a low-cost circularly polarized reader-writer antenna to realize high-performance read-write service; finally, by introducing reconfigurable design, the circularly polarized frequency adjustable antenna is realized, the application requirements of different scenes and dynamic variable scenes are met, and the high-stability and reliable wireless identification function is realized.
Description
Technical Field
The invention relates to an adjustable circularly polarized RFID reader-writer antenna, and belongs to the technical field of radio frequency antennas.
Background
With the development of wireless communication and artificial intelligence technologies, the technology of internet of things has been deeply involved in daily life and various production activities. As an important component of the internet of things, the Radio Frequency Identification (RFID) technology is widely applied to access control systems, warehouse management systems, and various industrial automation production lines, and assists people in promoting smart life and digital industry. The antenna in the RFID technology mainly comprises a tag antenna and a reader-writer antenna, wherein the reader-writer antenna can be divided into a near-field reader-writer antenna and a circularly polarized reader-writer antenna according to different application scenes and functions. The circularly polarized reader-writer antenna has the characteristics of polarization adaptation resistance, multipath effect improvement and angle insensitivity because the circularly polarized reader-writer antenna receives and transmits circularly polarized wave radio frequency signals, and can ensure that the antenna does not leak reading, is not invalid in communication and the like.
Currently, circular polarization reader/writer antennas can be roughly classified into four types: a circularly polarized patch antenna, a slot circularly polarized antenna, an orthogonal oscillator pair circularly polarized antenna, a multi-feed circularly polarized antenna and the like; the circularly polarized patch antenna is usually slotted on the patch antenna, frequency perturbation is introduced, and circularly polarized wave radiation is realized. The slot circular polarization antenna obtains two orthogonal magnetic field components by arranging orthogonal half-wavelength slots on the metal surface, thereby realizing circular polarization radiation. Because the slot antenna generally radiates in all directions at two sides, and a metal reflecting plate needs to be additionally arranged for directional radiation, the problems of limited use scenes and high integral section of the antenna exist, and the application in various different scenes is difficult to meet. The orthogonal oscillator pair circularly polarized antenna generally consists of two oscillators with frequency perturbation orthogonally arranged on a plane, and as a dual form of the slot circularly polarized antenna, the orthogonal oscillator pair circularly polarized antenna also has the defect of high antenna section, and is difficult to use in a scene with limited space. The multi-feed circularly polarized antenna sequentially arranges two, three and four equal feed points on the antenna, and sequentially excites each port by using the power division phase-shift feed network, thereby obtaining broadband circularly polarized waves. Due to the adoption of the multiport and the feed network, the system has the defects of complex structure and high cost, and is difficult to popularize and apply at low cost on a large scale.
Through the above overview and analysis of the prior art, the existing circularly polarized reader-writer antenna has the disadvantages and problems of limited working bandwidth, large size, complex structure, high cost and the like, so that the existing circularly polarized reader-writer antenna is difficult to meet the performance requirements of a high-performance RFID reader-writer and the application of different scenes.
Disclosure of Invention
The invention aims to provide an adjustable circularly polarized RFID reader-writer antenna, which adopts a brand new structure innovation, realizes high-performance circularly polarized radiation, and has the advantages of miniaturization, low cost, wide working bandwidth and simplified structure.
The invention adopts the following technical scheme for solving the technical problems: the invention designs an adjustable circular polarization RFID reader-writer antenna, which comprises a metal layer, a PCB substrate, a metal bottom plate, a feed probe and at least three metal support rods, wherein the metal layer is arranged on the metal bottom plate;
the metal layer covers one surface of the PCB substrate, four sub-areas divided by two mutually orthogonal capacitor gaps are constructed on the metal layer, the metal bottom plate is positioned on one side of the PCB substrate, which is back to the metal layer, and a preset distance interval is kept between the metal bottom plate and the PCB substrate; the feed probe corresponds to one of the subregions on the metal layer, the feed probe is positioned between the metal bottom plate and the PCB substrate, one end of the feed probe is electrically connected with the corresponding subregion, and the other end of the feed probe is connected with an RF feed signal;
all the metal supporting rods are divided into three supporting sets, each supporting set comprises a set of at least one metal supporting rod, and the three supporting sets are respectively in one-to-one correspondence with the metal layer sub-region connected with the feed probe and two sub-regions adjacent to the sub-region on the metal layer; each metal support rod in each support set is respectively positioned between the metal base plate and the PCB substrate, one end of each metal support rod is electrically connected with the metal base plate, and the other end of each metal support rod respectively penetrates through the PCB substrate and is electrically connected with the corresponding sub-area on the metal layer.
As a preferred technical scheme of the invention: the metal layer covers one surface of the PCB substrate; two mutually orthogonal linear capacitor gaps are arranged on the metal layer, the preset gap width is kept in each capacitor gap, and two ends of each capacitor gap extend to the edge of the metal layer respectively, so that the metal layer is divided into four sub-regions by the two mutually orthogonal capacitor gaps; the metal base plate is positioned on one side of the PCB substrate, which is back to the metal layer, a preset distance is kept between the metal base plate and the PCB substrate, and the projection of the metal layer is positioned in the projection of the metal base plate along the direction vertical to the surface of the metal base plate;
the feed probe corresponds to one of the subregions on the metal layer, an angular bisector of an orthogonal included angle between two capacitance gaps corresponding to the subregions is defined as a first reference line, the feed probe is positioned between the metal bottom plate and the PCB substrate, one end of the feed probe penetrates through the PCB substrate and is electrically connected with the corresponding subregion on the metal layer, the distance between the electrical connection position and the first reference line is not more than a preset first distance threshold, a straight line where the distance is located is defined as a second reference line, and the other end of the feed probe penetrates through the metal bottom plate and is connected with an RF feed signal.
As a preferred technical scheme of the invention: and regarding each electric connection position of each metal support rod and the sub-region in the support set corresponding to the sub-region of the feed probe connection metal layer, the distance between each electric connection position and the first reference line does not exceed a preset second distance threshold, each electric connection position is positioned on one side of the second reference line back to the orthogonal position of the two capacitance gaps, and each first closed-loop gap surrounding each electric connection position in a one-to-one correspondence manner is arranged on the metal layer.
As a preferred technical scheme of the invention: the metal layer is provided with two capacitor gaps, the metal layer is provided with two bias circuits, each bias circuit corresponds to the two capacitor gaps on the metal layer one by one, the structure of each bias circuit is the same, each bias circuit comprises a direct current control circuit and a variable capacitor which are connected with each other through a lead, the variable capacitors in each bias circuit are respectively arranged on two sides of the corresponding capacitor gaps on the metal layer, and the direct current control circuits in each bias circuit are insulated from any devices except the variable capacitors connected with the bias circuits.
As a preferred technical scheme of the invention: the direct current control circuits in the bias circuits are respectively arranged on the surface of the PCB substrate, which is opposite to the metal layer, and the conducting wires between the direct current control circuits and the corresponding variable capacitors in the bias circuits penetrate through the PCB substrate and the metal layer.
As a preferred technical scheme of the invention: and a second closed-loop gap surrounding the electric connection position of the feed probe and the metal layer is arranged on the metal layer.
As a preferred technical scheme of the invention: each first closed-loop slit and each second closed-loop slit are respectively circular, oval or polygonal.
As a preferred technical scheme of the invention: the metal layer is a polygon comprising two adjacent vertical edges, two capacitor gaps arranged on the metal layer are respectively parallel to the two adjacent vertical edges in the polygonal structure of the metal layer, and the distance between each capacitor gap and the edge of the polygonal structure parallel to the capacitor gap does not exceed a preset first distance threshold.
As a preferred technical scheme of the invention: and the distances between each capacitor gap and the sides of the polygonal structure parallel to the capacitor gap are equal to each other.
As a preferred technical scheme of the invention: the feed probe is an SMA probe connector or a coaxial feed line.
Compared with the prior art, the adjustable circularly polarized RFID reader-writer antenna adopting the technical scheme has the following technical effects:
(1) The invention designs an adjustable circularly polarized RFID reader-writer antenna, which is based on a metal layer, a PCB (printed Circuit Board) substrate, a metal bottom plate, a feed probe and at least three metal supporting rods, introduces an electromagnetic metamaterial technology, a cavity mode theory and a frequency reconfigurable design into the design of a circularly polarized antenna, and firstly provides an electromagnetic metamaterial resonator of a quasi-air substrate based on the electromagnetic metamaterial and the cavity mode theory, so that the dielectric loss is reduced and the high radiation efficiency is obtained while the miniaturization and the low cost are realized; then the electromagnetic metamaterial resonator is used in a low-cost circularly polarized reader-writer antenna to realize high-performance read-write service; finally, a reconfigurable design is introduced to realize a circularly polarized frequency adjustable antenna, compared with the traditional miniaturized reader-writer antenna, the circularly polarized frequency adjustable antenna has the advantages that the wider working bandwidth and the more stable circularly polarized radiation performance are realized, the defects of narrow bandwidth, unstable radiation and poor robustness of the traditional antenna are overcome, and the application of RFID systems and devices of different types is met;
(2) The adjustable circularly polarized RFID reader antenna has the advantages of miniaturization (low profile), simple structure, wide working bandwidth, low cost, high radiation performance, flexible and adjustable radiation performance and the like, and is suitable for various RFID application scenes and equipment communication application; the novel electromagnetic metamaterial resonator radiator structure is provided based on an electromagnetic metamaterial radiation technology, and the size of an antenna is compressed, namely the antenna is miniaturized; based on a cavity mode theory, the structure of the electromagnetic metamaterial radiator and the cavity loading are combined, so that the radiation aperture is improved, and stable radiation gain and high radiation performance are realized; the novel electromagnetic metamaterial radiator adopts a three-dimensional space configuration, effectively utilizes an aperture surface, obtains impedance bandwidth as large as possible, further expands the bandwidth by adopting a perturbation dual-mode, and realizes wide working bandwidth; the whole antenna is manufactured by adopting the metal bottom plate, the metal supporting rod and the PCB substrate, the structural form is simplified, the cost is reduced, and the antenna is more suitable for large-scale application; in addition, a reconfigurable design is introduced in the design, the two radiation gaps are respectively loaded with variable capacitors to be regulated and controlled, two frequency-adjustable electric field components are obtained, and then the frequency-adjustable circularly polarized antenna is realized, namely, the high-efficiency radiation performance is flexibly adjustable through voltage signals, the self-adaption capability of the antenna is improved, the frequency deviation phenomenon occurring in different scenes can be corrected, different wireless communication system applications can be met through frequency adjustment, namely, the flexible and adjustable radiation characteristics and good universality are realized.
(3) The invention provides two schemes of a miniaturized high-performance circularly polarized antenna and a miniaturized frequency-adjustable circularly polarized antenna in specific implementation in an adjustable circularly polarized RFID reader-writer antenna, and the provided electromagnetic metamaterial radiator and circularly polarized frequency reconfigurable design can flexibly adjust the size structure and frequency of the antenna according to different application scenes and has the advantage of flexible design.
Drawings
FIG. 1 is a schematic diagram of a 3D structure according to a first embodiment of the present invention;
FIG. 2a, FIG. 2b and FIG. 2c are a top view, a left side view and a front view, respectively, of a first embodiment of the present invention;
FIG. 3 is a diagram of the bandwidth of the impedance of the antenna according to the first embodiment of the present invention;
fig. 4 is a diagram of the radiation performance of the antenna according to the first embodiment of the present invention;
FIG. 5 is a schematic 3D structure of a second embodiment of the present invention;
FIG. 6a, FIG. 6b, and FIG. 6c are top, left, and front views, respectively, of a second embodiment of the present invention;
FIG. 7 is a graph of the impedance bandwidth of the antenna according to the second embodiment of the present invention;
fig. 8 is a radiation performance diagram of an antenna according to a second embodiment of the present invention.
The circuit comprises a metal layer 1, a PCB substrate 2, a metal bottom plate 3, a feed probe 4, a metal support rod 5, a capacitor gap 6, a first closed-loop gap 7, a direct current control circuit 8, a variable capacitor 9 and a second closed-loop gap 10.
Detailed Description
The following description will explain embodiments of the present invention in further detail with reference to the accompanying drawings.
The invention designs an adjustable circularly polarized RFID reader-writer antenna for realizing circularly polarized radiation with low cost and high performance, and in practical application, two embodiments are specifically designed, wherein the first embodiment is designed to form a miniaturized high-performance circularly polarized antenna, and as shown in fig. 1, fig. 2a, fig. 2b and fig. 2c, the specific structure comprises a metal layer 1, a PCB substrate 2, a metal bottom plate 3, a feed probe 4 and at least three metal support rods 5.
The PCB substrate 2 is a thin dielectric substrate with low dielectric constant and low loss, and the metal layer 1 covers one surface of the PCB substrate 2; two mutually orthogonal linear capacitor gaps 6 are arranged on the metal layer 1, the capacitor gaps 6 are usually rectangular long and thin grooves, the preset gap width of each capacitor gap 6 is kept, and two ends of each capacitor gap 6 extend to the edge of the metal layer 1 respectively, so that the metal layer 1 is divided into four sub-regions by the two mutually orthogonal capacitor gaps 6; the metal base plate 3 is located on one side of the PCB substrate 2 back to the metal layer 1, a preset distance is kept between the metal base plate 3 and the PCB substrate 2, the projection of the metal layer 1 is located in the projection of the metal base plate 3 along the direction perpendicular to the surface of the metal base plate 3, and a gap capacitance component is introduced through the capacitance gap 6 and serves as an equivalent resonance capacitor in design.
The feed probe 4 corresponds to one of the sub-regions on the metal layer 1, an angular bisector of an orthogonal included angle between two capacitance gaps 6 corresponding to the sub-region is defined as a first reference line, the feed probe 4 is located between the metal base plate 3 and the PCB substrate 2, one end of the feed probe 4 penetrates through the PCB substrate 2 and is electrically connected with the corresponding sub-region on the metal layer 1, the distance between the electrical connection position and the first reference line is not more than a preset first distance threshold, a straight line where the distance is located is defined as a second reference line, the other end of the feed probe 4 penetrates through the metal base plate 3 and is connected with an RF feed signal, and the feed probe 4 is used for connecting a radio frequency signal of an antenna to form circular polarization excitation and radiation.
All the metal support rods 5 are divided into three support sets, each support set comprises a set of at least one metal support rod 5, and the three support sets correspond to the sub-region of the metal layer 1 connected with the feed probe 4 and two sub-regions adjacent to the sub-region on the metal layer 1 one by one; each metal support rod 5 in each support set is respectively positioned between the metal base plate 3 and the PCB substrate 2, one end of each metal support rod 5 is electrically connected with the metal base plate 3, and the other end of each metal support rod 5 respectively penetrates through the PCB substrate 2 and is electrically connected with the corresponding sub-area on the metal layer 1; through the design, a current loop with an opening is formed by electrically connecting the metal support rod 5 between the metal layer 1 and the metal bottom plate 3, and the magnetic field effect of the current loop is equivalent to the equivalent resonance inductance in the design structure; and about the introduction of metal bottom plate 3, combine metal support rod 5 to make and form the cavity structure between PCB base plate 2 and the metal bottom plate 3, promote the radiation performance of antenna to can form a directional radiation of 3 directions of back to the metal bottom plate, and in the application, further through the value that increases equivalent resonance inductance in the design, and equivalent resonance electric capacity, thereby reduce the resonant frequency of antenna, realize the miniaturization of antenna.
The feed probe 4 is connected with each electric connection position of each metal support rod 5 and each subarea in the support set corresponding to the subarea of the metal layer 1, the distance between each electric connection position and the first reference line does not exceed a preset second distance threshold, each electric connection position is positioned on one side of the second reference line back to the orthogonal position of the two capacitor gaps 6, and each first closed-loop gap 7 which respectively surrounds each electric connection position in a one-to-one correspondence manner is arranged on the metal layer 1; the first closed-loop slits 7 are used for adjusting equivalent capacitance values in the structure of the electromagnetic metamaterial resonator, controlling the resonant frequency of the antenna, and meanwhile, the loading of the annular slits is used for adjusting the distribution of a radiation electric field on the surface of the antenna, so that high-performance radiation is obtained.
In the design structure, two orthogonal electromagnetic metamaterial resonator structures are formed by the design of the two capacitance gaps 6 and the corresponding metal support rods 5 in two adjacent sub-regions of the metal layer 1 sub-region connected with the feed probe 4, and meanwhile, the electromagnetic metamaterial resonator can be equivalent to a magnetic dipole due to the uniform and in-phase circulating current characteristic of the electromagnetic metamaterial resonator, namely, orthogonal magnetic dipole components respectively facing to two orthogonal directions are obtained; in application, the width of the two orthogonal capacitor gaps 6 is adjusted, so that the resonance frequency of the two orthogonal magnetic dipoles generates perturbation; feeding by using a feeding probe 4 close to the first reference line so as to obtain a 90-degree phase difference caused by impedance perturbation; by arranging two electromagnetic metamaterial resonators in an orthogonal mode, introducing frequency perturbation and exciting diagonal line feed, two magnetic dipole components with equal amplitude and 90-degree phase difference are obtained, and therefore circular polarized radiation is generated in a far field. In practical applications, as for the metal support rod 5, a specific design uses an elongated metal column, such as a metal screw; and as for the feed probe 4, an SMA probe joint or a coaxial feed line is designed.
In practical application of the structure, as shown in fig. 3, the-10 dB impedance bandwidth of the antenna is 880-940MHz (6.6%), the antenna completely covers 902-928MHz UHF frequency band, the antenna realizes wide impedance bandwidth on the premise of miniaturization, and can meet RFID read-write application under different scenes; as shown in fig. 4, the antenna realizes the side radiation of circular polarization, the directional diagram is similar to the classical half-wavelength patch antenna and the cavity backed antenna, the circular polarization performance is good, and the width of a circular polarization beam is wide, so that the antenna has good read-write capability and communication coverage capability, and is beneficial to the realization of high-stability and high-quality RFID identification application.
The above structure constitutes the miniaturized high-performance circularly polarized antenna of the first embodiment, as shown in fig. 5, fig. 6a, fig. 6b, and fig. 6c, two bias circuits are further introduced on the basis of the design, that is, the miniaturized frequency-adjustable circularly polarized antenna of the second embodiment is constituted, specifically, each bias circuit is designed to correspond to two capacitor gaps 6 on the metal layer 1 one by one, the structure of each bias circuit is the same, each bias circuit includes a dc control circuit 8 and a variable capacitor 9 connected with each other through a conducting wire, the variable capacitor 9 in each bias circuit is a tunable capacitor element, such as a varactor, a variable capacitor chip, etc., each variable capacitor 9 is installed on the metal layer 1 on two sides corresponding to the capacitor gaps 6, and the dc control circuit 8 in each bias circuit is insulated from any device except the variable capacitor 9 connected thereto.
In practical application, regarding the design of the insulation purpose of the dc control circuit 8 in each bias circuit, the dc control circuit 8 in each bias circuit may be specifically designed to be respectively disposed on the surface of the PCB substrate 2 opposite to the metal layer 1, and a conducting wire between the dc control circuit 8 and the corresponding variable capacitor 9 in each bias circuit passes through the PCB substrate 2 and the metal layer 1.
In practical application of the structure, the variable capacitor 9 is used for changing the equivalent resonant capacitor, and the capacitance value of the capacitor gap 6 is changed, so that the resonant frequencies of the two magnetic dipoles synchronously move, and the circular polarization frequency of the antenna can be tuned; a direct current control circuit 8 of the variable capacitor 9, which is used for controlling the capacitance value of the variable capacitor and changing the series capacitance value through the adjustment of an electric signal; in specific implementation and application, the two paths of bias circuits are controlled simultaneously, so that the two equivalent resonant capacitors are respectively connected with different capacitors in parallel, and then the resonant frequencies of the two orthogonal electromagnetic metamaterial resonators are moved simultaneously, so that the working frequency of the circularly polarized antenna is regulated and controlled, and the impedance response of the antenna and the corresponding continuous adjustability of the circular polarization performance are realized. In specific implementation, as shown in fig. 7, the impedance bandwidth of the antenna can be continuously tuned to 960MHz from 860MHz by using a variable capacitor, the continuous adjustable range is large, the antenna can well cover the RFID frequency band, and the antenna has good adaptive adjustability; as shown in fig. 8, the antenna can adjust the impedance bandwidth, and maintain good circular polarization radiation performance and circular polarization broadband coverage by fine tuning of the two variable capacitors.
The miniaturized high-performance circularly polarized antenna of the first embodiment or the miniaturized frequency-adjustable circularly polarized antenna of the second embodiment is applied to practice, and a second closed-loop gap 10 surrounding the electric connection position of the feed probe 4 and the metal layer 1 is further designed to be arranged on the metal layer 1; with regard to the structure of the feed probe 4, the introduction of the second closed-loop slot 10 realizes the series connection of capacitance in the feed probe 4, improves impedance matching, and simultaneously, the feed probe 4 is properly deviated from the first reference line for changing the value of the series connection inductance, thereby obtaining good impedance and high-efficiency radiation performance. And for each of the first closed-loop slit 7 and the second closed-loop slit 10 involved in the design, a circle, an ellipse or a polygon may be adopted in practical application.
In addition, in the application, the metal layer 1 is specifically designed to be a polygon including two adjacent vertical sides, two capacitor gaps 6 arranged on the metal layer 1 are respectively parallel to the two adjacent vertical sides in the polygonal structure of the metal layer 1, and the distance between each capacitor gap 6 and the side of the polygonal structure parallel to the capacitor gap does not exceed a preset first distance threshold; and in concrete actual design, can also further design each electric capacity gap 6 respectively rather than the parallel polygon structure between the limit apart from equal each other, so make two subregions adjacent with the metal level 1 subregion that feed probe 4 links, be located the border of metal level 1 respectively, cooperate the design of the corresponding metal support rod 5 of these two adjacent subregions, namely the electric field that originally was opened in metal level 1 border is closed, then utilize electric capacity gap 6 on the metal level 1 to carry out revealing of space electric field, the radiation field that has formed the similar cavity mould the same, and then improved the bore distribution, realized high-efficient electromagnetic radiation.
The adjustable circularly polarized RFID reader-writer antenna designed by the technical scheme is based on the metal layer 1, the PCB substrate 2, the metal bottom plate 3, the feed probe 4 and at least three metal support rods 5, the electromagnetic metamaterial technology, the cavity mode theory and the frequency reconfigurable design are introduced into the design of the circularly polarized antenna, firstly, the electromagnetic metamaterial resonator of the quasi-air substrate is provided based on the electromagnetic metamaterial and the cavity mode theory, the dielectric loss is reduced while the miniaturization and the low cost are realized, and the high radiation efficiency is obtained; then the electromagnetic metamaterial resonator is used in a low-cost circularly polarized reader-writer antenna to realize high-performance read-write service; finally, a reconfigurable design is introduced, so that a circularly polarized frequency adjustable antenna is realized, compared with the traditional miniaturized reader-writer antenna, the circularly polarized antenna has wider working bandwidth and more stable circularly polarized radiation performance, the defects of narrow bandwidth, unstable radiation and poor robustness of the traditional antenna are overcome, and the application of RFID systems and equipment of different types is met.
In design and implementation, the structure has the advantages of miniaturization (low profile), simple structure, wide working bandwidth, low cost, high radiation performance, flexible and adjustable radiation performance and the like, and is suitable for various RFID application scenes and equipment communication applications; based on the electromagnetic metamaterial radiation technology, a novel electromagnetic metamaterial resonator radiator structure is provided, and the size of an antenna is compressed, namely the antenna is miniaturized; based on a cavity mode theory, the structure of the electromagnetic metamaterial radiator and the cavity loading are combined, so that the radiation aperture is improved, and stable radiation gain and high radiation performance are realized; the novel electromagnetic metamaterial radiator adopts a three-dimensional space configuration, effectively utilizes an aperture surface, obtains impedance bandwidth as large as possible, further expands the bandwidth by adopting a perturbation dual-mode, and realizes wide working bandwidth; the whole antenna is manufactured by adopting the metal bottom plate, the metal supporting rod and the PCB substrate, the structural form is simplified, the cost is reduced, and the antenna is more suitable for large-scale application; in addition, a reconfigurable design is introduced in the design, the two radiation gaps are respectively loaded with variable capacitors to be regulated, two frequency-adjustable electric field components are obtained, and then the frequency-adjustable circularly polarized antenna is realized, namely, the efficient radiation performance is flexibly adjustable through voltage signals, the self-adaption capability of the antenna is improved, frequency deviation phenomena occurring in different scenes can be corrected, different wireless communication system applications can be met through frequency adjustment, namely, the flexible adjustable radiation characteristics and good universality are realized.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (10)
1. An adjustable circular polarization RFID read write line antenna which characterized in that: the PCB comprises a metal layer (1), a PCB substrate (2), a metal bottom plate (3), a feed probe (4) and at least three metal supporting rods (5);
the metal layer (1) covers one surface of the PCB substrate (2), four sub-regions divided by two mutually orthogonal capacitor gaps (6) are constructed on the metal layer (1), the metal bottom plate (3) is positioned on one side of the PCB substrate (2) back to the metal layer (1), and a preset distance interval is kept between the metal bottom plate (3) and the PCB substrate (2); the feed probe (4) corresponds to one of the subregions on the metal layer (1), the feed probe (4) is positioned between the metal bottom plate (3) and the PCB substrate (2), one end of the feed probe (4) is electrically connected with the corresponding subregion, and the other end of the feed probe (4) is connected with an RF feed signal;
all the metal supporting rods (5) are divided into three supporting sets, each supporting set comprises a set of at least one metal supporting rod (5), and the three supporting sets correspond to sub-regions of the metal layer (1) connected with the feed probe (4) and two sub-regions adjacent to the sub-regions on the metal layer (1) one by one; each metal support rod (5) in each support set is respectively positioned between the metal base plate (3) and the PCB (printed circuit board) substrate (2), one end of each metal support rod (5) is electrically connected with the metal base plate (3), and the other end of each metal support rod (5) respectively penetrates through the PCB substrate (2) and is electrically connected with the corresponding sub-region on the metal layer (1).
2. The adjustable circularly polarized RFID reader antenna of claim 1, wherein: the metal layer (1) covers one surface of the PCB substrate (2); two mutually orthogonal linear capacitor gaps (6) are arranged on the metal layer (1), the preset gap width of each capacitor gap (6) is kept, and two ends of each capacitor gap (6) extend to the edge of the metal layer (1) respectively, so that the metal layer (1) is divided into four sub-regions by the two mutually orthogonal capacitor gaps (6); the metal base plate (3) is positioned on one side of the PCB substrate (2) back to the metal layer (1), a preset distance is kept between the metal base plate (3) and the PCB substrate (2), and the projection of the metal layer (1) is positioned in the projection of the metal base plate (3) along the direction vertical to the surface of the metal base plate (3);
the feed probe (4) corresponds to one of the sub-regions on the metal layer (1), an angular bisector of an orthogonal included angle between two capacitance gaps (6) corresponding to the sub-region is defined as a first reference line, the feed probe (4) is located between the metal base plate (3) and the PCB substrate (2), one end of the feed probe (4) penetrates through the PCB substrate (2) and is electrically connected with the corresponding sub-region on the metal layer (1), the distance between the electrically connected position and the first reference line is not more than a preset first distance threshold, a straight line where the distance is located is defined as a second reference line, and the other end of the feed probe (4) penetrates through the metal base plate (3) and is connected with an RF feed signal.
3. The adjustable circularly polarized RFID reader antenna of claim 2, wherein: and the feed probe (4) is connected with each electric connection position of each metal support rod (5) and the subarea in the support set corresponding to the subarea of the metal layer (1), the distance between each electric connection position and the first reference line does not exceed a preset second distance threshold, each electric connection position is positioned on one side of the second reference line back to the orthogonal position of the two capacitance gaps (6), and each first closed-loop gap (7) which respectively surrounds each electric connection position in a one-to-one correspondence manner is arranged on the metal layer (1).
4. The adjustable circularly polarized RFID reader antenna of claim 3, wherein: the circuit comprises a metal layer (1), and is characterized by further comprising two bias circuits, wherein each bias circuit corresponds to two capacitor gaps (6) in the metal layer (1) one by one, the structures of the bias circuits are the same, each bias circuit comprises a direct current control circuit (8) and a variable capacitor (9) which are connected through a lead, the variable capacitors (9) in the bias circuits are installed on the metal layer (1) and correspond to the two sides of the capacitor gaps (6), and the direct current control circuits (8) in the bias circuits are insulated from any devices except the variable capacitors (9) connected with the bias circuits.
5. The adjustable circularly polarized RFID reader antenna of claim 4, wherein: the direct current control circuits (8) in each path of bias circuit are respectively arranged on the surface of the PCB substrate (2) back to the metal layer (1), and a lead between the direct current control circuit (8) in each path of bias circuit and the corresponding variable capacitor (9) penetrates through the PCB substrate (2) and the metal layer (1).
6. The adjustable circularly polarized RFID reader antenna of any one of claims 1 to 5, wherein: and a second closed-loop gap (10) surrounding the electric connection position of the feed probe (4) and the metal layer (1) is arranged on the metal layer (1).
7. The adjustable circularly polarized RFID reader antenna of claim 6, wherein: the first closed-loop gaps (7) and the second closed-loop gaps (10) are respectively circular, oval or polygonal.
8. The adjustable circularly polarized RFID reader antenna of claim 6, wherein: the metal layer (1) is a polygon comprising two adjacent vertical edges, two capacitor gaps (6) arranged on the metal layer (1) are respectively parallel to the two adjacent vertical edges in the polygonal structure of the metal layer (1), and the distance between each capacitor gap (6) and the edge of the polygonal structure parallel to the capacitor gap does not exceed a preset first distance threshold.
9. The adjustable circularly polarized RFID reader antenna of claim 8, wherein: the distances between each capacitor gap (6) and the sides of the polygonal structure parallel to the capacitor gaps are equal to each other.
10. The adjustable circularly polarized RFID reader antenna of any one of claims 1 to 3, wherein: the feed probe (4) is an SMA probe connector or a coaxial feed line.
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| CN115313060B (en) | 2023-03-24 |
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