Same-circular-polarization same-frequency full-duplex antenna pair based on cavity back-to-slot antenna

Abstract

The invention discloses a co-circularly-polarized co-frequency full-duplex antenna pair based on a cavity back-to-slot antenna, and belongs to the technical field of cavity back slot antennas, the co-circularly-polarized co-frequency full-duplex antenna pair comprises three dielectric substrates and metal frames fixed between every two of the three dielectric substrates, the two adjacent dielectric substrates and the metal frames are fixedly connected to form a cavity, and the cavity back-to-slot antenna is arranged in the cavity back-to-slot antenna. Two cross-shaped radiation slots are formed in the uppermost first dielectric substrate in the three dielectric substrates side by side, a metal patch is fixedly mounted in the middle of the middle second dielectric substrate in the three dielectric substrates, and slots are formed in the two opposite side walls of the metal patch in the width direction of the dielectric substrates; the dielectric substrates are provided with two feed columns, and the two feed columns penetrate through the lowermost third dielectric substrate in the three dielectric substrates and are fixedly connected with the inner wall of the first dielectric substrate. According to the invention, high isolation between receiving and transmitting ports is realized in a mode of mode superposition, introduction of a complex decoupling network is avoided, and design complexity and energy loss are effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cavity-backed slot antennas, in particular to a cavity-backed slot antenna pair with common cavity, common circular polarization and in-band full-duplex, which is suitable for antenna design of radio frequency identification readers. Background Art

[0002] With the rapid development of the Internet of Things, miniaturized and high-performance IoT devices have received increasing attention. As one of the key technologies, radio frequency identification technology plays an important role in scenarios such as logistics management, large-scale warehousing, port and container management, and airline baggage tracking. Radio frequency identification reader antennas are usually designed to be circularly polarized to meet the needs of various tag identification, while requiring compact size, consistent transmission and reception performance, and high-precision recognition capabilities. To meet the requirements of transmission and reception consistency, the designed radio frequency identification reader antenna needs to achieve miniaturization, high gain, and self-packaging characteristics, while maintaining consistent radiation patterns and polarization characteristics. In addition, in order to improve recognition accuracy, the recently studied in-band full-duplex technology can achieve simultaneous transmission and reception of signals, thereby avoiding data loss during the transmission and reception switching and improving reading and writing accuracy. Therefore, the study of in-band full-duplex co-polarized circularly polarized radio frequency identification reader antennas that meet the above application requirements has great industrial appeal.

[0003] The main challenge facing the technology is to achieve high isolation between the transmitter and the receiver. Existing methods include using polarization diversity, space diversity, and introducing decoupling structures or circuits to solve this problem. Polarization diversity reduces coupling by placing the transmitting and receiving antennas in orthogonal polarization states, but is not conducive to maintaining the consistency of transmission and reception; space diversity improves isolation by increasing the distance between the transmitting and receiving antennas, but causes the antenna to increase in size, which is not conducive to system integration. In addition, although the introduction of decoupling structures (such as electromagnetic bandgap structures, defective ground structures, absorbers, and decoupling networks) can reduce coupling, it will increase antenna complexity and loss, reducing the overall system efficiency.

[0004] To address the above issues, existing studies have proposed methods such as loading metasurface ribs, mode superposition, path cancellation, and common-mode-differential mode cancellation for in-band full-duplex antennas with shared radiators. However, most of the research focuses on the design of linearly polarized antennas and is difficult to apply to circularly polarized antennas. In addition, although there are also circularly polarized in-band full-duplex antennas based on shared radiators, most of them are implemented through complex feeding networks, which significantly increases the antenna size, design complexity, loss, and cost.

[0005] Therefore, it is very necessary to develop a simple, miniaturized, efficient and low-cost in-band full-duplex co-circularly polarized RFID reader antenna technology. Summary of the invention

[0006] In view of this, an object of the present invention is to provide a co-circularly polarized co-frequency full-duplex antenna pair based on a cavity-backed slot antenna, so as to solve the problems in the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a co-circularly polarized co-frequency full-duplex antenna pair based on a cavity-backed slot antenna, which is used for a radio frequency identification reader antenna and comprises three dielectric substrates and a metal frame fixed between the three dielectric substrates in pairs, wherein two adjacent machine-made substrates are fixedly connected to the metal frame to form a cavity, wherein a first dielectric substrate located at the top of the three dielectric substrates is provided with two cross-shaped radiation slots arranged side by side along the length direction of the dielectric substrate, a second dielectric substrate located in the middle of the three dielectric substrates is fixedly installed with a metal patch in the middle, slots are provided on both side walls of the metal patch that are opposite to each other along the width direction of the dielectric substrate, and two feeding posts are provided on the dielectric substrate, wherein the two feeding posts penetrate through a third dielectric substrate located at the bottom of the three dielectric substrates and are fixedly connected to the inner wall of the first dielectric substrate.

[0009] Furthermore, the third dielectric substrate is provided with a third through hole for the feeding column to pass through, the diameter of the third through hole is larger than the diameter of the feeding column, and the second dielectric substrate is provided with a second through hole for the feeding column to pass through, and the second through hole is gap-matched with the feeding column.

[0010] Furthermore, two feeding poles are arranged between two radiation slots, the first feeding pole of the two feeding poles is arranged close to the bottom wall of the metal patch, and the top of the first feeding pole is close to the vertical edge of the radiation slot on the left; the second feeding pole of the two feeding poles is arranged close to the top wall of the metal patch, and the top of the second feeding pole is close to the vertical edge of the radiation slot on the right.

[0011] Furthermore, a through hole is provided on the metal frame along the second dielectric substrate in the middle of the three dielectric substrates, a conductive column is fixedly connected in the through hole, and two ends of the conductive column are respectively abutted against the two metal frames.

[0012] Furthermore, the two slots are symmetrically arranged and located between the two radiation slots.

[0013] Furthermore, the dielectric substrates are all made of F4BM220 material, having a relative dielectric constant of 2.2 and a loss tangent of 0.003.

[0014] Furthermore, the bottom surface of the first dielectric substrate is copper-plated, and both the second dielectric substrate and the third dielectric substrate are copper-plated on both sides.

[0015] The beneficial effects of the present invention are:

[0016] 1. High isolation performance: Through the mode superposition method, high isolation performance is achieved without a complex decoupling network. The isolation bandwidth between the two ports is 916.5-925.4MHz, and the maximum isolation can reach 27.4dB;

[0017] 2. Circular polarization performance: In the frequency range of 916.5–929.5MHz, the antenna axial ratio is less than 3dB, meeting the requirements of RFID reader antennas in the ultra-high frequency band;

[0018] 3. Consistent radiation pattern performance: The antenna maintains good radiation direction within the bandwidth Figure 1 The two ports show stable left-hand circularly polarized radiation characteristics.

[0019] 4. Miniaturization design: Miniaturization and high gain design: The antenna has a compact structure and the overall electrical size is 0.88×0.7×0.1λ 3 , while achieving a high gain of 7.7dBic, which is suitable for space-constrained RFID application scenarios;

[0020] 5. Simple and efficient: By loading metal patches and cross-radiation slots in the cavity, the introduction of complex decoupling networks is avoided, effectively reducing the design complexity while ensuring high efficiency and low loss.

[0021] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0023] Figure 1 It is a structural schematic diagram of the present invention;

[0024] Figure 2 It is an axonometric view of the overall structure of the present invention;

[0025] Figure 3 This is a diagram of the upper gap structure of the cavity in the present invention;

[0026] Figure 4 This is a structural diagram of a patch loaded in the middle layer of the cavity in the present invention;

[0027] Figure 5 This is a schematic diagram of the feeding position of the lower layer in the present invention;

[0028] Figure 6 Reflection coefficient and isolation coefficient curve graph of the present invention;

[0029] Figure 7 The present invention can realize the gain and axis ratio curve diagram;

[0030] Figure 8 When the excitation port 1 is in the present invention, Direction diagram of the surface;

[0031] Fig. 9 When the excitation port 1 is in the present invention, Direction diagram of the surface;

[0032] Fig.10 When the excitation port 1 is in the present invention, Direction diagram of the surface;

[0033] Fig.11 When the excitation port 1 is in the present invention, Direction diagram of the surface;

[0034] In the figure: 1-radiation gap; 2-first dielectric substrate; 3-first metal frame; 4-conductive column; 5-second dielectric substrate; 6-second metal frame; 7-third dielectric substrate; 8-first feeding column; 9-second feeding column; 10-metal patch. DETAILED DESCRIPTION

[0035] like Figures 1 to 11As shown, the present invention provides a co-circularly polarized co-frequency full-duplex antenna pair based on a cavity-backed slot antenna, which is used for a radio frequency identification reader antenna, comprising: three dielectric substrates and a metal frame fixed between the three dielectric substrates, two adjacent dielectric substrates are fixedly connected to the metal frame to form a cavity, and the three dielectric substrates are all made of F4BM220 material, with a relative dielectric constant of 2.2 and a loss tangent of 0.003; the overall size of the antenna pair is 0.88×0.7×0.1λ3, and broadband circular polarization is achieved, and the axial ratio bandwidth covers a frequency range of 916.5-929.5MHz; on the first dielectric substrate 2 located at the top of the three dielectric substrates, two cross-shaped radiation slots 1 are arranged side by side along the length direction of the dielectric substrate, and on the second dielectric substrate 5 located in the middle of the three dielectric substrates, a through hole is arranged along the metal frame, and a conductive column 4 is fixedly connected in the through hole, so that The two ends of the conductive column 4 are respectively abutted against the two metal frames, wherein the top end of the conductive column 4 is abutted against the bottom wall of the first metal frame 3, and the bottom end of the conductive column 4 is abutted against the top wall of the second metal frame 6. A metal patch 10 is fixedly installed in the middle of the second dielectric substrate 5, and the two side walls opposite to each other along the width direction of the dielectric substrate are provided with gaps on the metal patch 10, and the two gaps are symmetrically arranged and located between the two radiation gaps 1. Two feeding columns are arranged on the dielectric substrate, and the two feeding columns penetrate the third dielectric substrate 7 located at the bottom of the three dielectric substrates and are fixedly connected to the inner wall of the first dielectric substrate 2. A third through hole for the feeding column to pass through is arranged on the third dielectric substrate 7, and the diameter of the third through hole is greater than the diameter of the feeding column. A second through hole for the feeding column to pass through is arranged on the second dielectric substrate 5, wherein the first dielectric substrate 2 is provided with a first through hole for fixing with the feeding column.

[0036] In this scheme, if Figure 2-5 , the height between the first dielectric substrate 2 and the third dielectric substrate 7 is h, wherein the height between the first dielectric substrate 2 and the second dielectric substrate 5 is h1, the height between the second dielectric substrate 5 and the third dielectric substrate 7 is h2, the vertical side length of the radiation slot 1 is l3, the vertical side width is w3, the horizontal side length of the radiation slot 1 is l4, the horizontal side width is w4, the vertical side spacing between the two radiation slots 1 is l5, the length of the metal frame is l sub , the width of the metal frame is w sub , the length of the cavity is l, the width of the cavity is w, the length of the metal patch 10 is l1, the width of the metal patch 10 is w1, the length of the gap is l2, the width of the gap is w2, the diameter of the conductive column 4 is d2, the spacing between two adjacent conductive columns 4 in the same extension direction is S, the diameter of the third through hole is d4, the distance between the third through hole and the wide side of the third dielectric substrate 7 is l4, the distance between the third through hole and the long side of the third dielectric substrate 7 is w4, the diameter of the second through hole is d1, and the diameter of the first through hole is d3.

[0037] Table 1 Optimal size table of various parameters of the present invention

[0038]

[0039]

[0040] According to the above structure and parameters, the performance of the designed antenna is simulated using HFSS software. The simulation results are as follows:

[0041] Reflection coefficient and isolation performance: such as Figure 6 As shown, the antenna meets |S in the frequency range 916.5–925.4MHz. 11 |(reflection coefficient)≤-10dB matching performance, while achieving |S 21 |(Coupling coefficient)<-20dB high isolation bandwidth, maximum isolation can reach 27.4dB.

[0042] Axis ratio performance: Figure 7 As shown, under the condition that the axial ratio (AR) ≤ 3, the circular polarization bandwidth of the antenna covers a frequency range of 916.5–929.5 MHz.

[0043] Directional pattern performance: Figure 8-Figure 11 As shown, when the antenna is excited at two ports, it exhibits a consistent left-hand circularly polarized radiation pattern, and the direction Figure 1 Good consistency.

[0044] The present invention achieves high isolation, co-circular polarization and miniaturized high-gain performance through optimized cavity design and radiator structure, and is particularly suitable for high-efficiency and high-performance radio frequency identification reader antennas.

[0045] The two radiation slots 1 are used to realize orthogonal electric field components and a 90° phase difference, thereby realizing left-hand circularly polarized radiation, and the two symmetrical slots are used to adjust the electric field distribution inside the cavity; by loading the metal patch 10 in the cavity, high isolation between the transmitting and receiving ports is achieved through mode superposition, avoiding the introduction of a complex decoupling network, thereby effectively reducing the design complexity and energy loss.

[0046] In one embodiment of the present invention, two feeding poles are arranged between two radiation slots 1, and the first feeding pole 8 of the two feeding poles is arranged close to the bottom wall of the metal patch 10, and the top of the first feeding pole 8 is close to the vertical edge of the radiation slot 1 on the left; the second feeding pole 9 of the two feeding poles is arranged close to the top wall of the metal patch 10, and the top of the second feeding pole 9 is close to the vertical edge of the radiation slot 1 on the right.

[0047] In this solution, through the design of the above structure, by adding a patch in the cavity, the antenna pair achieves mode superposition and creates a symmetrical weak field area in the cavity. By placing the feed post in the weak field area, the isolation performance between the two ports is improved.

[0048] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0049] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A co-circularly polarized co-frequency full-duplex antenna pair based on a cavity-backed slot antenna, used as a radio frequency identification reader antenna, characterized in that: The invention comprises three dielectric substrates and a metal frame fixed between the three dielectric substrates in pairs, wherein two adjacent mechanical substrates are fixedly connected to the metal frame to form a cavity, wherein a first dielectric substrate located at the top among the three dielectric substrates is provided with two cross-shaped radiation slots arranged side by side along the length direction of the dielectric substrate, a second dielectric substrate located in the middle among the three dielectric substrates is fixedly installed with a metal patch in the middle, and slots are arranged on both side walls opposite to each other along the width direction of the dielectric substrate on the metal patch, and two feeding posts are arranged on the dielectric substrate, and the two feeding posts penetrate through the third dielectric substrate located at the bottom among the three dielectric substrates and are fixedly connected to the inner wall of the first dielectric substrate.

2. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 1, characterized in that: The third dielectric substrate is provided with a third through hole for the feeding column to pass through, and the diameter of the third through hole is larger than the diameter of the feeding column. The second dielectric substrate is provided with a second through hole for the feeding column to pass through, and the second through hole is gap-matched with the feeding column.

3. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 2, characterized in that: Two feeding poles are arranged between two radiation slots, the first feeding pole of the two feeding poles is arranged close to the bottom wall of the metal patch, and the top of the first feeding pole is close to the vertical edge of the radiation slot on the left; the second feeding pole of the two feeding poles is arranged close to the top wall of the metal patch, and the top of the second feeding pole is close to the vertical edge of the radiation slot on the right.

4. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 3, characterized in that: A through hole is arranged on the metal frame of the second dielectric substrate in the middle of the three dielectric substrates. A conductive column is fixedly connected in the through hole. Two ends of the conductive column are respectively against the two metal frames.

5. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 4, characterized in that: The two slots are symmetrically arranged and located between the two radiation slots.

6. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 5, characterized in that: The dielectric substrates are all made of F4BM220 material, with a relative dielectric constant of 2.2 and a loss tangent of 0.

003.

7. The same circular polarization same frequency full duplex antenna pair based on cavity backed slot antenna according to claim 6, characterized in that: The bottom surface of the first dielectric substrate is copper plated, and both the second dielectric substrate and the third dielectric substrate are copper plated on both sides.

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