Narrow-beam low-sidelobe circularly polarized antenna

Abstract

The invention provides a narrow-beam low-sidelobe circularly polarized antenna, the narrow-beam low-sidelobe circularly polarized antenna adopts a multi-layer board structure and comprises a top circuit layer, a middle circuit layer and a bottom circuit layer, the top circuit layer comprises n radiation array subunits, the bottom circuit layer is a feed network and comprises one input end and 2n output ends, the output ends are electrically connected with the radiation array subunits respectively, and the middle line layer is a reference ground of the radiation array subunits and the feed network. The narrow-beam low-sidelobe circularly polarized antenna has high gain and extremely low sidelobe; a broadband structure is adopted, so that the antenna has a relatively wide working bandwidth, and is relatively suitable for the field of RFID access control management and the field of wireless communication with relatively high requirements on antenna beam concentration ratio.

Description

Technical Field

[0001] The invention relates to the technical field of RFID applications, and in particular to a narrow-beam low-side-lobe circular polarization antenna. Background Art

[0002] In recent years, the application of radio frequency identification technology has become increasingly widespread and has received more and more attention, especially the UHF band RFID system, which has attracted much attention due to its long transmission distance and fast recognition rate. A typical RFID system consists of three parts: a reader, an antenna and a tag. The RFID tag relies on the electromagnetic signal emitted by the RFID reader to charge, and communicates with the reader by reverse modulating the electromagnetic signal. Therefore, as the RFID antenna that transmits electromagnetic signals from the RFID reader, its quality has a key impact on the working performance of the entire RFID system. A typical example is the field of access control for RFID intelligent anti-theft. The difficulty of this application has always been to balance missed reading and cross-reading. Wide-beam antennas require a larger display prohibited area to reduce cross-reading, with low space utilization and limited application; narrow-beam antennas can effectively reduce cross-reading, but are limited in size, mostly two-unit array antennas, with large side lobes. In some high-power applications, such as retail, tool management industries, and other applications where the performance of tags varies greatly, cross-reading is still prone to occur.

[0003] In the Chinese patent application with application number: CN201920946632.5, a circularly polarized multilayer board antenna, antenna subarray and array antenna are involved. By setting a monopole antenna on the surface of one side of the first layer, a signal with the same phase and orthogonal polarization is radiated and fed out; a first metal layer, a second metal layer, an interconnecting through hole connecting the first metal layer and the second metal layer, and a monopole feeding terminal connected to other functional modules are set on the second layer; a parasitic patch with a symmetrical central gap is set at the same time, and the vertical projection of the monopole antenna on the parasitic patch covers the central gap. Furthermore, the technical solution of the application rotates the multilayer board antenna by 90 degrees and arranges it in sequence in a positive matrix to form a circularly polarized antenna subarray, and further arranges the circularly polarized antenna subarray in a matrix manner to form an array antenna. This has the technical effect of improving the gain of the circularly polarized antenna, expanding the standing wave bandwidth and axial ratio bandwidth, and miniaturization.

[0004] In the Chinese patent application with application number: CN201611255786.7, a narrow beam RFID circular polarization antenna system is involved, which belongs to the field of radio frequency identification technology and antenna technology. The antenna system includes two transceiver antenna elements, an antenna bracket with adjustable angle, a reader and a logic control alarm circuit. The antenna system uses the logical relationship between the beams of the two antenna elements to control the practical beam. The reader polls the two transceiver antenna elements and uploads the information of the read tag to the logic control alarm circuit. The logic control alarm circuit performs logical judgment on the acquired information. Only when it is judged that the tag comes from the two ports of the reader, the tag is considered valid, that is, the intersection of the radiation beams of the two antenna elements is the practical beam, and the practical beam of the antenna system is controlled by adjusting the radiation angle of the two antenna elements. This invention is very suitable for RFID access control systems. It can not only regulate the practical beam of the RFID antenna system, but also enhance the accuracy of tag recognition and reduce the misjudgment of the RFID access control system.

[0005] In the Chinese patent application with application number: CN201420191290.8, a miniaturized narrow beam circularly polarized antenna is involved, including an insulating dielectric plate, a feeding network, a metal base plate and eight metal radiating arrays; wherein the feeding network is arranged on the insulating dielectric plate; the metal base plate is arranged on the back of the insulating dielectric plate; the eight metal radiating arrays are evenly divided into two groups; both groups of arrays are installed on the front of the insulating dielectric plate; each group forms a square in a clockwise or counterclockwise direction and is connected to the feeding network. The miniaturized narrow beam antenna provided by the utility model can convert electromagnetic waves with concentrated beam, wide axial ratio bandwidth and circular polarization; it has the advantages of miniaturization, simple structure, stable performance, low cost, and is suitable for large-scale industrial production. The utility model not only overcomes the defects of narrow bandwidth and large volume of single-port feeding, but also simplifies the complex shortcomings of multi-port feeding system, improves performance, and is more suitable for the application of RFID industry access control system.

[0006] In the Chinese patent application with application number: CN201410591356.7, a high-gain narrow-beam array antenna that can be used for access control is involved. The array antenna is composed of four unit antennas. The unit antenna adopts a double-layer PCB structure. The unit antenna gain is about 7.5db. The measured antenna gain is greater than 12db at 902MHz~928MHz. The standing wave ratio is less than 1.3, the E-plane width is 18 degrees, and the H-plane width is 88 degrees. The antenna is connected to a power divider and can be regarded as a whole. The array antenna of this invention is placed at the access control as a whole. The commonly used access control antenna is two antennas erected at the entrance and exit. The present invention can be hung above the entrance and exit or buried underground, which effectively saves space.

[0007] The above existing technologies are all significantly different from the present invention and fail to solve the technical problem we want to solve. For this reason, we have invented a new narrow beam low sidelobe circularly polarized antenna. Summary of the invention

[0008] The object of the present invention is to provide a narrow beam low side lobe circular polarization antenna which is easy to process, has a low profile, a simple and compact structure, and is light in weight.

[0009] The object of the present invention can be achieved through the following technical measures: a narrow beam low sidelobe circularly polarized antenna, which adopts a multi-layer board structure, including a top circuit layer, an intermediate circuit layer and a bottom circuit layer, the top circuit layer includes n radiating array units, the bottom circuit layer is a feeding network, including 1 input end and 2n output ends, the output ends are electrically connected to the corresponding radiating array units, and the intermediate circuit layer is the reference ground of the radiating array units and the feeding network.

[0010] The purpose of the present invention can also be achieved by the following technical measures:

[0011] The radiation array unit is a microstrip patch array unit, which is square or circular in shape. Square small patch units are arranged around the radiation array unit and between the radiation array units. The radiation array units are arranged in a straight line with equal distances.

[0012] The square small patch unit is connected to the middle circuit layer through a metallized via to form an electromagnetic bandgap structure, so as to reduce the size of the antenna and the coupling between the radiation array sub-units, and reduce the antenna radiation side lobe.

[0013] The feeding network includes a T-type cross junction, a primary microstrip power division phase shift network and a secondary microstrip power division phase shift network. The T-type cross junction divides the radio frequency signal into two signals with a power division ratio of a certain proportion. The primary microstrip power division phase shift network plus the T-type cross junction form n radio frequency signals with a power division ratio of a certain proportion. The secondary microstrip power division phase shift network divides the n radio frequency signals of the previous level into n groups of radio frequency signals with equal amplitude and a phase difference of 90°.

[0014] The top circuit layer includes three radiation array units, and the feeding network of the bottom circuit layer includes one input end and six output ends.

[0015] The T-junction splits the RF signal into two signals with a power ratio of 2:3.

[0016] The first-level microstrip power division and phase shifting network divides one output signal of the T-type cross junction into two equal-phase and equal-amplitude radio frequency signals, and adds the other output signal of the T-type cross junction to form three signals with a power division ratio of 3:4:3.

[0017] The power division ratio between the middle radiation array unit and the radiation array units on both sides of the three radiation array units is 4:3:3.

[0018] The narrow beam low side lobe circular polarization antenna is made of a multi-layer high frequency circuit board or a laminated board of other materials and PCB board.

[0019] The feeding network is placed on the upper layer of the double-sided board of the PCB board, and the lower layer is the reference ground of the feeding network.

[0020] The radiation array unit is made of good electrical conductors such as metal aluminum or metal copper.

[0021] The narrow beam low side lobe circular polarization antenna in the present invention feeds different amplitudes of power to each radiating element, so that the antenna has high gain and extremely low side lobes; at the same time, electromagnetic band gap structures are added between and around the antenna elements to reduce the coupling between the elements, suppress surface waves, and miniaturize the antenna size, and further reduce the side lobes; to ensure better transmission performance, the feeding network adopts a wide-band structure, so that the antenna has a wider working bandwidth, which is more suitable for the RFID access control management field and the wireless communication field with high requirements for antenna beam concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a front view of a narrow beam low side lobe circularly polarized antenna in a specific embodiment 1 of the present invention;

[0023] Figure 2 It is a feeding network diagram of a narrow beam low side lobe circular polarization antenna in a specific embodiment 1 of the present invention;

[0024] Figure 3 It is a layer structure diagram of the narrow beam low side lobe circular polarization antenna in specific embodiments 1 and 3 of the present invention;

[0025] Figure 4 It is a feeding principle block diagram of the narrow beam low side lobe circular polarization antenna in specific embodiments 1 and 2 of the present invention;

[0026] Figure 5 It is a front view of a narrow beam low side lobe circularly polarized antenna in a specific embodiment 2 of the present invention;

[0027] Figure 6 It is a front view of a narrow beam low side lobe circularly polarized antenna in specific embodiment 3 of the present invention;

[0028] Figure 7 This is a feeding network diagram of a narrow beam low side lobe circularly polarized antenna in specific embodiment 3 of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0031] A narrow beam low sidelobe circular polarization antenna adopts a multilayer board structure, including a top circuit layer, a middle circuit layer and a bottom circuit layer, wherein the top layer is a radiating array, the middle layer is a reference ground, and the bottom layer is a feeding network. The n (for example, 3) radiating array units of the top layer are in the form of microstrip patches and are arranged equidistantly in a line; the feeding network of the bottom layer includes 1 input terminal and 2n output terminals (for example, n is 3, i.e., 6 output terminals), and the output terminals are electrically connected to the radiating array units through metallized vias; the middle layer is the reference ground of the radiating array units and the feeding network.

[0032] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above has a radiating array that is a 3-unit microstrip patch array unit in a square shape, with square small patch units arranged around the radiating array and between the units; further, the square small patch units are connected to the reference ground layer in the middle through metallized vias to form an electromagnetic bandgap structure, so as to reduce the antenna size and the coupling between the array units, while reducing the antenna radiation side lobes.

[0033] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above, the feeding network includes a T-type cross junction and a two-stage microstrip power division phase shift network, the T-type cross junction divides the RF signal into two signals with a certain power ratio, the first-stage microstrip power division phase shift network plus the T-type cross junction forms n signals with a certain power ratio, the second-stage microstrip power division phase shift network divides the n RF signals of the previous stage into n groups of RF signals with equal amplitude and phase difference of 90°; the two output ports form a group, one group feeds a radiating array unit, and the purpose of the phase difference of 90° is to allow a single radiating array unit to form a circularly polarized wave.

[0034] Furthermore, in the above narrow beam low side lobe circular polarization antenna, the power division ratio between the middle array unit and the array units on both sides is 4:3:3.

[0035] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above is made of a multi-layer high frequency circuit board or other materials and a PCB board laminated board;

[0036] The narrow beam low sidelobe circular polarization antenna described above has a radiation signal frequency range of 902Mhz-928Mhz or 865Mhz-868Mhz. The frequency of the radiation signal can be adjusted by adjusting the size of the microstrip patch.

[0037] The following are several specific embodiments of the present invention.

[0038] Example 1

[0039] In a specific embodiment 1 of the present invention, the structure and principle of the narrow beam low side lobe circular polarization antenna of the present invention are as follows: Figures 1 to 4 As shown, it includes a top circuit layer, a middle circuit layer and a bottom circuit layer, wherein the top layer is a radiation array layer 10, the middle layer is a reference ground 20, and the bottom layer is a feeding network 30. The three radiation array units 11A, 11B, and 11C of the top layer are in the form of microstrip patches and are arranged equidistantly in a line; the feeding network 30 of the bottom layer includes an input terminal 34 and six output terminals 35A, 35B, 36A, 36B, 37A, and 37B, and the output terminals are electrically connected to the radiation array units 11A, 11B, and 11C through metallized vias, wherein 35A and 35B are connected to the radiation array unit 11A with a phase difference of 90°, 36A and 36B are connected to the radiation array unit 11B with a phase difference of 90°, and 37A and 37B are connected to the radiation array unit 11C with a phase difference of 90°; the middle layer is the radiation array unit 11 and the reference ground 20 of the feeding network 30.

[0040] Furthermore, in the narrow beam low sidelobe circularly polarized antenna described above, the radiating array 11 is a 3-unit microstrip patch array unit, which is square in shape, and square small patch units 12 are arranged around the radiating array 11 and between each unit; further, the square small patch unit 12 is connected to the middle reference ground 20 layer through a metallized via to form an electromagnetic bandgap structure, so as to reduce the antenna size and the coupling between each array unit, while reducing the antenna radiation sidelobe.

[0041] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above, the feeding network 30 includes a T-type cross junction 31 and a two-stage microstrip power division phase shift network, the T-type cross junction 31 divides the radio frequency signal into two signals with a power ratio of 2:3, the first-stage microstrip power division phase shift network 32 divides one output signal of the T-type cross junction 31 into two equal-phase and equal-amplitude radio frequency signals, plus the other output signal of the T-type cross junction 31 to form three signals with a power ratio of 3:4:3, the second-stage microstrip power division phase shift network 33 (including 33A, 33B and 33C) divides the three radio frequency signals of the previous stage into three groups of equal-amplitude radio frequency signals with a phase difference of 90°;

[0042] Furthermore, in the above narrow beam low side lobe circular polarization antenna, the power division ratio between the middle array unit and the array units on both sides is 4:3:3.

[0043] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above is made of a multi-layer high frequency circuit board or other materials and a PCB board laminated board;

[0044] Example 2

[0045] In another specific embodiment 2 of the present invention, the structure and principle of the antenna are as follows: Figures 3 to 5 As shown, in this embodiment, the three radiation array units 11A, 11B, and 11C are arranged in a straight line with equal spacing using air as the medium. In order to facilitate processing, the electromagnetic band gap structure is removed; the feeding network 30 is placed directly below the three radiation array units 11A, 11B, and 11C, including an input terminal 34 and six output terminals 35A, 35B, 36A, 36B, 37A, and 37B. The output terminals are electrically connected to the radiation array units 11A, 11B, and 11C through metal rods 40, wherein 35A and 35B are connected to the radiation array unit 11A with a phase difference of 90°, 36A and 36B are connected to the radiation array unit 11B with a phase difference of 90°, and 37A and 37B are connected to the radiation array unit 11C with a phase difference of 90°;

[0046] Furthermore, the three radiation array units 11A, 11B, and 11C are made of good electrical conductors such as metal aluminum or metal copper.

[0047] Furthermore, the feeding network 30 is placed on the upper layer of the double-sided board of the PCB board, and the lower layer is the reference ground of the feeding network.

[0048] Example 3

[0049] In a specific embodiment 3 of the present invention, the structure and principle of the narrow beam low side lobe circular polarization antenna of the present invention are as follows: Figure 3 , Figure 6 and Figure 7As shown, it includes a top circuit layer, a middle circuit layer and a bottom circuit layer, wherein the top layer is a radiation array layer 10, the middle layer is a reference ground 20, and the bottom layer is a feed network 30. The four radiation array units 11A, 11B, 11C, and 11D of the top layer are in the form of microstrip patches and are arranged equidistantly in a straight line; the feed network 30 of the bottom layer includes an input terminal 34 and eight output terminals 35A, 35B, 36A, 36B, 37A, 37B, 38A, and 38B, and the output terminals are connected through metallized vias. They are electrically connected to the radiation array units 11A, 11B, 11C, and 11D respectively, among which 35A and 35B are connected to the radiation array unit 11A with a phase difference of 90°, 36A and 36B are connected to the radiation array unit 11B with a phase difference of 90°, 37A and 37B are connected to the radiation array unit 11C with a phase difference of 90°, and 38A and 38B are connected to the radiation array unit 11D with a phase difference of 90°; the middle layer is the reference ground 20 of the radiation array unit 11 and the feeding network 30.

[0050] Furthermore, in the narrow beam low sidelobe circularly polarized antenna described above, the radiating array 11 is a 4-unit microstrip patch array unit, which is square in shape, and square small patch units 12 are arranged around the radiating array 11 and between each unit; further, the square small patch unit 12 is connected to the middle reference ground 20 layer through a metallized via to form an electromagnetic bandgap structure, so as to reduce the antenna size and the coupling between each array unit, and at the same time reduce the antenna radiation sidelobe.

[0051] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above, the feeding network 30 includes a T-type cross junction 31 and a two-stage microstrip power division phase shift network, the T-type cross junction 31 divides the radio frequency signal into two signals with a power ratio of 2:1, the first-stage microstrip power division phase shift network 32A, 32B divides the two output signals of the T-type cross junction 31 into two groups of equal-phase and equal-amplitude radio frequency signals, forming four signals with a power ratio of 1:2:2:1, and the second-stage microstrip power division phase shift network 33 (including 33A, 33B, 33C and 33D) divides the four radio frequency signals of the previous stage into four groups of equal-amplitude radio frequency signals with a phase difference of 90°;

[0052] Furthermore, in the above-mentioned narrow beam low sidelobe circularly polarized antenna, the power division ratio between the two middle array units and the two array units on both sides is 2:2:1:1.

[0053] Furthermore, the narrow beam low sidelobe circularly polarized antenna described above is made of a multi-layer high frequency circuit board or other materials and a PCB board laminated board;

[0054] The application frequency band of the above embodiment of the present invention is 902Mhz-928Mhz. It should be noted that the frequency band of the embodiment can be adjusted to 865Mhz-868Mhz by adjusting the length and width of the radiation array 11.

[0055] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0056] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. Narrow beam low sidelobe circular polarization antenna, characterized in that: The narrow beam low sidelobe circularly polarized antenna adopts a multi-layer board structure, including a top circuit layer, an intermediate circuit layer and a bottom circuit layer. The top circuit layer includes n radiating array units. The bottom circuit layer is a feeding network, including 1 input end and 2n output ends. The output ends are electrically connected to the corresponding radiating array units respectively. The intermediate circuit layer is the reference ground of the radiating array units and the feeding network.

2. The narrow beam low sidelobe circular polarization antenna according to claim 1, characterized in that: The radiation array unit is a microstrip patch array unit, which is square or circular in shape. Square small patch units are arranged around the radiation array unit and between the radiation array units. The radiation array units are arranged in a straight line with equal distances.

3. The narrow beam low sidelobe circular polarization antenna according to claim 2, characterized in that: The square small patch unit is connected to the middle circuit layer through a metallized via to form an electromagnetic bandgap structure, so as to reduce the size of the antenna and the coupling between the radiation array sub-units, and reduce the antenna radiation side lobe.

4. The narrow beam low sidelobe circular polarization antenna according to claim 1, characterized in that: The feeding network includes a T-type cross junction, a primary microstrip power division phase shift network and a secondary microstrip power division phase shift network. The T-type cross junction divides the radio frequency signal into two signals with a power division ratio of a certain proportion. The primary microstrip power division phase shift network plus the T-type cross junction form n radio frequency signals with a power division ratio of a certain proportion. The secondary microstrip power division phase shift network divides the n radio frequency signals of the previous level into n groups of radio frequency signals with equal amplitude and a phase difference of 90°.

5. The narrow beam low sidelobe circular polarization antenna according to claim 4, characterized in that: The top circuit layer includes three radiation array units, and the feeding network of the bottom circuit layer includes one input end and six output ends.

6. The narrow beam low sidelobe circular polarization antenna according to claim 5, characterized in that: The T-junction splits the RF signal into two signals with a power ratio of 2:

3.

7. The narrow beam low sidelobe circular polarization antenna according to claim 6, characterized in that: The first-level microstrip power division and phase shifting network divides one output signal of the T-type cross junction into two equal-phase and equal-amplitude radio frequency signals, and adds the other output signal of the T-type cross junction to form three signals with a power division ratio of 3:4:

3.

8. The narrow beam low sidelobe circular polarization antenna according to claim 7, characterized in that: The power division ratio between the middle radiation array unit and the radiation array units on both sides of the three radiation array units is 4:3:

3.

9. The narrow beam low sidelobe circular polarization antenna according to claim 1, characterized in that: The narrow beam low side lobe circular polarization antenna is made of a multi-layer high frequency circuit board or a laminated board of other materials and PCB board.

10. The narrow beam low sidelobe circular polarization antenna according to claim 9, characterized in that: The feeding network is placed on the upper layer of the double-sided board of the PCB board, and the lower layer is the reference ground of the feeding network.

11. The narrow beam low sidelobe circular polarization antenna according to claim 1, characterized in that: The radiation array unit is made of good electrical conductors such as metal aluminum or metal copper.

Images