Circularly polarized near-field antenna

Abstract

The utility model relates to a circularly polarized near-field antenna, which comprises an upper circuit board, a lower circuit board and a coaxial cable, the center of the top surface of the upper circuit board is a point M, and four oscillator units are formed on the top surface of the upper circuit board in a copper coating manner; each oscillator unit is of a square spiral structure, and the four oscillator units are arranged in an annular array by taking a point M as a center to form a mutually nested structure; the lower circuit board is fixed below the upper circuit board, and a feed circuit is formed on the top surface of the lower circuit board in a copper-clad manner; the feed circuit is provided with an input connecting end and four output connecting ends; the four output connecting ends are in one-to-one correspondence with the four oscillator units, and the corresponding output connecting ends are connected and conducted with the feed connecting ends of the oscillator units; an inner conductor of the coaxial cable is electrically connected with the input connection end of the feed circuit, and an outer conductor of the coaxial cable is connected with the ground. The utility model has the characteristics of simple structure, scientific design, small volume, light weight, low production cost and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of RFID application technology, especially a circular polarization near field antenna. BACKGROUND

[0002] At present, the circular polarization near field antenna on the market is generally like the technical scheme described in patent application number CN2022203648228, named "a near field antenna", the four copper areas on the circuit board are arranged into a rectangular array with 2 rows and 2 columns, such a structure has a larger radiation surface, but it also makes the near field antenna larger in size and heavier in weight, which is not conducive to carrying and transporting. CONTENT OF THE UTILITY MODEL

[0003] The utility model aims at providing a circular polarization near field antenna, which has the advantages of simple structure, scientific design, small size, light weight and low production cost.

[0004] The technical scheme of the utility model is implemented as follows: a circular polarization near field antenna, in particular, comprising an upper circuit board, a lower circuit board and a coaxial cable; wherein:

[0005] The upper circuit board and the lower circuit board are both square plates, the center of the top surface of the upper circuit board is point M, and four vibrator units are formed in a copper manner on the top surface of the upper circuit board; each vibrator unit is a square spiral structure, and the four vibrator units are arranged in a ring array with point M as the center;

[0006] Each vibrator unit comprises six first straight line segments, which are respectively F1, F2, F3, F4, F5 and F6; the line width range of each of F1, F2, F3, F4, F5 and F6 is 3±0.1mm;

[0007] The line length range of F1 is 28±0.2mm; the length direction of F1 is parallel to two side edges of the upper circuit board, and the vertical distance D1 between F1 and point M is 11±0.2mm in size range;

[0008] The line length range of F2 is 38±0.2mm; one end of F2 is connected to one end of F1 in a perpendicular manner, and the vertical distance D2 between F2 and point M is 17.5±0.2mm in size range;

[0009] The line length range of F3 is 51±0.2mm; F3 is opposite to F1, and point M is between F3 and F1, one end of F3 is connected to the other end of F2 in a perpendicular manner;

[0010] The line length range of F4 is 64±0.2mm; F4 is opposite to F2, and one end of F4 is connected to the other end of F3 in a perpendicular manner;

[0011] The line length of F5 ranges from 77±0.2mm; F5 is located on the side of F1 facing away from F3, and one end of F5 is connected in perpendicular to the other end of F4;

[0012] The line length of F6 ranges from 80±0.2mm; F6 is located on the side of F2 facing away from F4, and one end of F6 is connected in perpendicular to the other end of F5, and the other end of F6 is connected with a feeding connection end located at the corner position of the upper circuit board;

[0013] The lower circuit board is fixed below the upper circuit board, and a feeding circuit is formed on the top surface of the lower circuit board in a copper-clad manner; the feeding circuit is provided with an input connection end and four output connection ends; the four output connection ends are respectively a first connection end, a second connection end, a third connection end and a fourth connection end arranged in sequence around the center of the top surface of the lower circuit board, and the signal phases output by the first connection end, the second connection end, the third connection end and the fourth connection end are respectively 0°, 90°, 180° and 270°; the four output connection ends correspond one-to-one to the four vibrator units, and between each corresponding output connection end and vibrator unit: the output connection end is connected in conductive communication with the feeding connection end of the vibrator unit.

[0014] The inner conductor of the coaxial cable is electrically connected to the input connection end of the feeding circuit, and the outer conductor of the coaxial cable is connected to the ground.

[0015] Each vibrator unit of the present scheme is a square spiral structure, and after specific size setting is performed on the six first straight line segments of the vibrator unit and the relative position between the vibrator unit and point M is set, the four vibrator units arranged in a ring array with point M as the center are nested with each other; compared with the existing circularly polarized near-field antenna, the volume of the present scheme is greatly reduced, the weight is lighter, and the production cost is reduced and transportation is facilitated; in addition, the following electrical indicators can be obtained when the present scheme is used: frequency range: 902-928MHz, gain: -5dBi, beam width: Hor: 91°, Ver: 93°, polarization mode: circular polarization, voltage standing wave ratio ≤1.8, front-to-back ratio ≥12, impedance: 50Ω, maximum input power: 100W.

[0016] Further, a reflecting surface is formed on the bottom surface of the lower circuit board in a copper-clad manner, and the orthographic projection of each vibrator unit on the bottom surface of the lower circuit board is located in the reflecting surface.

[0017] Further, the feeding circuit includes a first circuit, a second circuit and a third circuit.

[0018] The first circuit includes eight second straight line segments, which are respectively K1, K2, K3, K4, K5, K6, K7 and K8.

[0019] The line length of K1 ranges from 30.5±0.5mm, the line width of K1 ranges from 3.3±0.1mm, the length direction of K1 is parallel to two sides of the lower circuit board, and one end of K1 is connected to the input connection end for conduction;

[0020] The line length of K2 ranges from 14.5±0.5mm, the line width of K2 ranges from 3.3±0.1mm, one end of K2 is connected to the other end of K1 perpendicularly for conduction;

[0021] The line length of K3 ranges from 11.6±0.5mm, the line width of K3 ranges from 1.9±0.1mm, K3 is on the side of K2 facing K1, and one end of K3 is connected to the other end of K2 perpendicularly for conduction;

[0022] The line length of K4 ranges from 12±0.5mm, the line width of K4 ranges from 1.9±0.1mm, K4 is on the side of K2 facing away from K3, and one end of K4 is connected to the end of K2 connected to K3 perpendicularly for conduction;

[0023] The line length of K5 ranges from 11.8±0.5mm, the line width of K5 ranges from 1.9±0.1mm, K5 is on the side of K4 facing away from K2, and one end of K5 is connected to the other end of K4 perpendicularly for conduction;

[0024] The line length of K6 ranges from 29.7±0.5mm, the line width of K6 ranges from 1.9±0.1mm, K6 is on the side of K5 facing away from K4, and one end of K6 is connected to the other end of K5 perpendicularly for conduction;

[0025] The line length of K7 ranges from 42.1±0.5mm, the line width of K7 ranges from 1.9±0.1mm, K7 is on the side of K6 facing K5, and one end of K7 is connected to the other end of K6 perpendicularly for conduction;

[0026] The line length of K8 ranges from 11.1±0.5mm, the line width of K8 ranges from 1.9±0.1mm, K8 is on the side of K7 facing K6, and one end of K8 is connected to the other end of K7 perpendicularly for conduction;

[0027] The second circuit and the third circuit each include an isolation resistor and 11 third straight line segments, which are respectively referred to as H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, and H11;

[0028] The line length of H1 ranges from 7.9±0.3mm, and the line width of H1 ranges from 1.9±0.1mm;

[0029] The line length of H2 ranges from 18±0.5mm, the line width of H2 ranges from 0.9±0.1mm, and one end of H2 is connected to one end of H1 perpendicularly for conduction;

[0030] The line length of H3 is 12±0.5mm, the line width of H3 is 0.9±0.1mm, H3 is on the side of H2 facing away from H1, and one end of H3 is connected in perpendicular to the other end of H2;

[0031] The line length of H4 is 17.2±0.5mm, the line width of H4 is 0.9±0.1mm, H4 is on the side of H3 facing H2, and one end of H4 is connected in perpendicular to the other end of H3;

[0032] The line length of H5 is 10±0.5mm, the line width of H5 is 1.9±0.1mm, H5 is on the side of H4 facing away from H3, and one end of H5 is connected in perpendicular to the other end of H4;

[0033] The line length of H6 is 18.3±0.5mm, the line width of H6 is 1.9±0.1mm, H6 is on the side of H5 facing H4, and one end of H6 is connected in perpendicular to the other end of H5;

[0034] The line length of H7 is 18±0.5mm, the line width of H7 is 0.9±0.1mm, H7 is on the side of H1 facing away from H2, and one end of H7 is connected in perpendicular to the end of H1 connected with H2;

[0035] The line length of H8 is 12±0.5mm, the line width of H8 is 0.9±0.1mm, H8 is opposite to H3, and one end of H8 is connected in perpendicular to the other end of H7;

[0036] The line length of H9 is 17.2±0.5mm, the line width of H9 is 0.9±0.1mm, H9 is on the side of H8 facing H7, and one end of H9 is connected in perpendicular to the other end of H8;

[0037] The line length of H10 is 10±0.5mm, the line width of H10 is 1.9±0.1mm, H10 is arranged side by side with H5, one end of H10 is connected in perpendicular to the other end of H9, and the isolation resistor is electrically connected between H10 and H5;

[0038] The line length of H11 is 62±0.5mm, the line width of H11 is 1.9±0.1mm, H11 is on the side of H10 facing away from H5, and one end of H11 is connected in perpendicular to the other end of H10;

[0039] The other end of H1 of the second circuit is connected in conduction with the other end of K3 vertically, K3 and H7 of the second circuit are on the same side of H1 of the second circuit, the other end of H6 of the second circuit is connected in conduction with the first connecting end, and the other end of H11 of the second circuit is connected in conduction with the second connecting end.

[0040] The other end of H1 of the third circuit is connected in conduction with the other end of K8 vertically, K8 and H2 of the third circuit are on the same side of H1 of the third circuit, the other end of H6 of the third circuit is connected in conduction with the third connecting end, and the other end of H11 of the third circuit is connected in conduction with the fourth connecting end.

[0041] Further, the upper circuit board and the lower circuit board are both FR-4 boards with a dielectric coefficient in the range of 4.2-4.7.

[0042] Further, the size range of the length A of each of the upper circuit board and the lower circuit board is 110±5mm, the size range of the thickness T1 of each of the upper circuit board and the lower circuit board is 1±0.1mm, and the size range of the spacing D3 between the upper circuit board and the lower circuit board is 3±0.2mm.

[0043] Further, mounting holes are formed at the four corners of the lower circuit board, and notches for exposing the mounting holes are formed at the four corners of the upper circuit board.

[0044] Further, each corresponding output connecting end and the feed connecting end of the vibrator unit are connected in conduction by metal posts.

[0045] Further, four EVA cotton pads are clamped between the upper circuit board and the lower circuit board, and the four EVA cotton pads are arranged along the four sides of the upper circuit board respectively.

[0046] The utility model discloses the beneficial effects of simple structure, scientific design, small size, light weight and low production cost. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is the three-dimensional structure schematic diagram of example.

[0048] Figure 2 It is the dismounting structure schematic diagram of example.

[0049] Figure 3 It is the main view structure schematic diagram of example.

[0050] Figure 4 It is the main view structure schematic diagram of lower circuit board of example.

[0051] Figure 5A schematic view of the back structure of the lower circuit board of the embodiment.

[0052] Figure 6 A horizontal plane radiation pattern of the embodiment in use.

[0053] Figure 7 A vertical plane radiation pattern of the embodiment in use.

[0054] BRIEF DESCRIPTION OF REFERENCE NUMERALS: 1 - upper circuit board; 11 - notch; 2 - lower circuit board; 21 - reflecting surface; 22 - mounting hole; 3 - coaxial cable; 4 - vibrator unit; 41 - feed connection end; 5 - feed circuit; 51 - input connection end; 52 - first connection end; 53 - second connection end; 54 - third connection end; 55 - fourth connection end; 56 - first circuit; 57 - second circuit; 58 - third circuit; 59 - isolation resistor; 6 - metal guide post; 7 - EVA cotton pad. DETAILED DESCRIPTION

[0055] As shown in Figure 1 , Figure 2 , Figure 3 , Figure 4 , a circularly polarized near-field antenna of the embodiment comprises an upper circuit board 1, a lower circuit board 2 and a coaxial cable 3; wherein:

[0056] The upper circuit board 1 and the lower circuit board 2 are both square plates; the center of the top surface of the upper circuit board 1 is point M, and four vibrator units 4 are formed on the top surface of the upper circuit board 1 in a copper-clad manner; each vibrator unit 4 is a square spiral structure, and the four vibrator units 4 are arranged in a ring array with point M as the center;

[0057] Each vibrator unit 4 comprises six first straight line segments, which are respectively F1, F2, F3, F4, F5 and F6; the line width of each of F1, F2, F3, F4, F5 and F6 is 3 mm;

[0058] The line length of F1 is 28 mm; the length direction of F1 is parallel to two side edges of the upper circuit board 1, and the vertical spacing D1 between F1 and point M is 11 mm in size;

[0059] The line length of F2 is 38 mm; one end of F2 is connected in vertical communication with one end of F1, and the vertical spacing D2 between F2 and point M is 17.5 mm in size;

[0060] The line length of F3 is 51 mm; F3 is opposite to F1, and point M is between F3 and F1, one end of F3 is connected in vertical communication with the other end of F2;

[0061] The line length of F4 is 64 mm; F4 is opposite to F2, and one end of F4 is connected in vertical communication with the other end of F3;

[0062] The line length of F5 is 77mm; F5 is located on the side of F1 facing away from F3, and one end of F5 is connected in parallel to the other end of F4;

[0063] The line length of F6 is 80mm; F6 is located on the side of F2 facing away from F4, and one end of F6 is connected in parallel to the other end of F5, and the other end of F6 is connected to the feeding connection end 41 located at the corner of the upper circuit board 1;

[0064] The lower circuit board 2 is fixed below the upper circuit board 1, and the feeding circuit 5 is formed on the top surface of the lower circuit board 2 in a copper-clad manner; the feeding circuit 5 is provided with an input connection end 51 and four output connection ends; the four output connection ends are respectively a first connection end 52, a second connection end 53, a third connection end 54 and a fourth connection end 55 arranged in turn around the center of the top surface of the lower circuit board 2, and the signal phases output by the first connection end 52, the second connection end 53, the third connection end 54 and the fourth connection end 55 are respectively 0°, 90°, 180° and 270°; the four output connection ends correspond one-to-one to the four vibrator units 4, and between each corresponding output connection end and the vibrator unit 4: the output connection end is connected in parallel to the feeding connection end 41 of the vibrator unit 4;

[0065] The inner conductor of the coaxial cable 3 is electrically connected to the input connection end 51 of the feeding circuit 5, and the outer conductor of the coaxial cable 3 is connected to the ground. Such a design arranges the four vibrator units 4 in a ring array centered on the point M, so that compared with the existing circularly polarized near-field antenna, the volume is greatly reduced, the weight is lighter, and it is beneficial to reduce production costs and facilitate transportation.

[0066] In order to further optimize the circularly polarized near-field antenna, in order to enhance the radiation intensity of the circularly polarized near-field antenna in the specified direction, as shown in Figure 4 , Figure 5 The bottom surface of the lower circuit board 2 is formed in a copper-clad manner with a reflecting surface 21, and the orthographic projection of each vibrator unit 4 on the bottom surface of the lower circuit board 2 is located within the reflecting surface 21.

[0067] In order to make the structure of the feeding circuit 5 more reasonable, as shown in Figure 2 , Figure 4 The feeding circuit 5 includes a first circuit 56, a second circuit 57 and a third circuit 58;

[0068] The first circuit 56 includes eight second straight line segments, which are respectively K1, K2, K3, K4, K5, K6, K7 and K8;

[0069] The line length of K1 is 30.5mm, the line width of K1 is 3.3mm, the length direction of K1 is parallel to two sides of the lower circuit board 2, and one end of K1 is connected to the input connection end 51 for conduction;

[0070] The line length of K2 is 14.5mm, the line width of K2 is 3.3mm, one end of K2 is connected to the other end of K1 perpendicularly for conduction, and the angle formed by K2 and K1 is chamfered at the outer corner;

[0071] The line length of K3 is 11.6mm, the line width of K3 is 1.9mm, K3 is on the side of K2 facing K1, one end of K3 is connected to the other end of K2 perpendicularly for conduction, and the angle formed by K3 and K2 is chamfered at the outer corner;

[0072] The line length of K4 is 12mm, the line width of K4 is 1.9mm, K4 is on the side of K2 facing away from K3, one end of K4 is connected to the end of K2 connected to K3 perpendicularly for conduction, and the angle formed by K4 and K3 is chamfered at the outer corner;

[0073] The line length of K5 is 11.8mm, the line width of K5 is 1.9mm, K5 is on the side of K4 facing away from K2, one end of K5 is connected to the other end of K4 perpendicularly for conduction, and the angle formed by K5 and K4 is chamfered at the outer corner;

[0074] The line length of K6 is 29.7mm, the line width of K6 is 1.9mm, K6 is on the side of K5 facing away from K4, one end of K6 is connected to the other end of K5 perpendicularly for conduction, and the angle formed by K6 and K5 is chamfered at the outer corner;

[0075] The line length of K7 is 42.1mm, the line width of K7 is 1.9mm, K7 is on the side of K6 facing K5, one end of K7 is connected to the other end of K6 perpendicularly for conduction, and the angle formed by K7 and K6 is chamfered at the outer corner;

[0076] The line length of K8 is 11.1mm, the line width of K8 is 1.9mm, K8 is on the side of K7 facing K6, one end of K8 is connected to the other end of K7 perpendicularly for conduction, and the angle formed by K8 and K7 is chamfered at the outer corner;

[0077] The second circuit 57 and the third circuit 58 each include an isolation resistor 59 and 11 third straight line segments, which are respectively H1, H2, H3, H4, H5, H6, H7, H8, H9, H10 and H11;

[0078] The line length of H1 is 7.9mm, and the line width of H1 is 1.9mm;

[0079] The line length of H2 is 18 mm, the line width of H2 is 0.9 mm, and one end of H2 is connected in vertical conduction with one end of H1;

[0080] The line length of H3 is 12 mm, the line width of H3 is 0.9 mm, H3 is located on the side of H2 away from H1, one end of H3 is connected in vertical conduction with the other end of H2, and the angle formed by the connection of H3 and H2 is chamfered at the outer corner;

[0081] The line length of H4 is 17.2 mm, the line width of H4 is 0.9 mm, H4 is located on the side of H3 facing H2, one end of H4 is connected in vertical conduction with the other end of H3, and the angle formed by the connection of H4 and H3 is chamfered at the outer corner;

[0082] The line length of H5 is 10 mm, the line width of H5 is 1.9 mm, H5 is located on the side of H4 away from H3, one end of H5 is connected in vertical conduction with the other end of H4, and the angle formed by the connection of H5 and H4 is chamfered at the outer corner;

[0083] The line length of H6 is 18.3 mm, the line width of H6 is 1.9 mm, H6 is located on the side of H5 facing H4, one end of H6 is connected in vertical conduction with the other end of H5, and the angle formed by the connection of H6 and H5 is chamfered at the outer corner;

[0084] The line length of H7 is 18 mm, the line width of H7 is 0.9 mm, H7 is located on the side of H1 away from H2, one end of H7 is connected in vertical conduction with the end of H1 connected with H2;

[0085] The line length of H8 is 12 mm, the line width of H8 is 0.9 mm, H8 is opposite to H3, one end of H8 is connected in vertical conduction with the other end of H7, and the angle formed by the connection of H8 and H7 is chamfered at the outer corner;

[0086] The line length of H9 is 17.2 mm, the line width of H9 is 0.9 mm, H9 is located on the side of H8 facing H7, one end of H9 is connected in vertical conduction with the other end of H8, and the angle formed by the connection of H9 and H8 is chamfered at the outer corner;

[0087] The line length of H10 is 10 mm, the line width of H10 is 1.9 mm, H10 is arranged side by side with H5, one end of H10 is connected in vertical conduction with the other end of H9, and the angle formed by the connection of H10 and H9 is chamfered at the outer corner, and the isolation resistor 59 is electrically connected between H10 and H5, the resistance value range of the isolation resistor 59 is 1000±10Ω, and the resistance value of the isolation resistor 59 in the embodiment is 1000Ω;

[0088] The line length of the H11 is 62mm, the line width of the H11 is 1.9mm, the H11 is on the side of the H10 facing away from the H5, one end of the H11 is connected in perpendicular to the other end of the H10 to conduct, and the angle formed by the H11 and the H10 is chamfered at the outer corner;

[0089] The other end of the H1 of the second circuit 57 is connected in perpendicular to the other end of the K3 to conduct, and the angle formed by the H1 of the second circuit 57 and the K3 is chamfered at the outer corner; the H7 of the K3 and the second circuit 57 are on the same side of the H1 of the second circuit 57, the other end of the H6 of the second circuit 57 is connected to the first connecting end 52 to conduct, and the other end of the H11 of the second circuit 57 is connected to the second connecting end 53 to conduct.

[0090] The other end of the H1 of the third circuit 58 is connected in perpendicular to the other end of the K8 to conduct, and the angle formed by the H1 of the third circuit 58 and the K8 is chamfered at the outer corner; the H2 of the K8 and the third circuit 58 are on the same side of the H1 of the third circuit 58, the other end of the H6 of the third circuit 58 is connected to the third connecting end 54 to conduct, and the other end of the H11 of the third circuit 58 is connected to the fourth connecting end 55 to conduct.

[0091] As shown in Figure 1 , Figure 2 , the upper circuit board 1 and the lower circuit board 2 are both FR-4 board materials with a dielectric coefficient of 4.5. The FR-4 board material has stable electrical insulation performance and good flatness, which facilitates copper production on the surfaces of the upper circuit board 1 and the lower circuit board 2, making the production of the circular polarization near-field antenna easier.

[0092] As shown in Figure 1 , Figure 3 , Figure 4 , the size of the side length A of each of the upper circuit board 1 and the lower circuit board 2 is 110mm, the size of the thickness T1 of each of the upper circuit board 1 and the lower circuit board 2 is 1mm, and the spacing D3 between the upper circuit board 1 and the lower circuit board 2 is 3mm. Such a design makes the structure of the circular polarization near-field antenna more reasonable, and makes the circular polarization near-field antenna achieve the preset electrical indicators when in use.

[0093] In order to facilitate the installation of the circular polarization near-field antenna, as shown in Figure 1 , Figure 2 , Figure 3 , Figure 4 , mounting holes 22 are formed at the four corner portions of the lower circuit board 2, and notches 11 for exposing the mounting holes 22 are formed at the four corner portions of the upper circuit board 1.

[0094] As shown in Figure 2As shown, each corresponding output connecting end and the feed connecting end 41 of the vibrator unit 4 are welded and conducted through the metal column 6. In addition to conducting the output connecting end and the feed connecting end 41 of the vibrator unit 4, the metal column 6 also serves to fixedly connect the upper circuit board 1 and the lower circuit board 2, making it very convenient to assemble the upper circuit board 1 and the lower circuit board 2.

[0095] In order to further improve the structural strength of the circularly polarized near-field antenna, as shown in the drawings, four EVA cotton pads 7 are clamped between the upper circuit board 1 and the lower circuit board 2. Figure 2

[0096] The circularly polarized near-field antenna has the following electrical indicators when in use: frequency range: 902-928 MHz, gain: -5 dBi, beam width: Hor: 91°, Ver: 93°, polarization mode: circular polarization, voltage standing wave ratio: ≤1.8, front-to-back ratio: ≥12, impedance: 50 Ω, maximum input power: 100 W. The circularly polarized near-field antenna can obtain the horizontal plane radiation pattern as shown in the drawings and the vertical plane radiation pattern as shown in the drawings when in use. Figure 6 Figure 7 The circularly polarized near-field antenna has the following electrical indicators when in use: frequency range: 902-928 MHz, gain: -5 dBi, beam width: Hor: 91°, Ver: 93°, polarization mode: circular polarization, voltage standing wave ratio: ≤1.8, front-to-back ratio: ≥12, impedance: 50 Ω, maximum input power: 100 W. The circularly polarized near-field antenna can obtain the horizontal plane radiation pattern as shown in the drawings and the vertical plane radiation pattern as shown in the drawings when in use.​​

Claims

1. A circularly polarized near-field antenna, characterized by: It comprises an upper circuit board, a lower circuit board and a coaxial cable; wherein: The upper circuit board and the lower circuit board are square plates, and the center of the top surface of the upper circuit board is point M, and four vibrator units are formed in a copper-clad manner on the top surface of the upper circuit board; each vibrator unit is a square spiral structure, and the four vibrator units are arranged in a ring array with point M as the center; Each vibrator unit comprises six first straight line segments, which are respectively F1, F2, F3, F4, F5 and F6; the line width range of each of F1, F2, F3, F4, F5 and F6 is 3±0.1mm; The line length range of F1 is 28±0.2mm; the length direction of F1 is parallel to two side edges of the upper circuit board, and the vertical distance D1 between F1 and point M is 11±0.2mm; The line length range of F2 is 38±0.2mm; one end of F2 is connected to one end of F1 in a vertical and conductive manner, and the vertical distance D2 between F2 and point M is 17.5±0.2mm; The line length range of F3 is 51±0.2mm; F3 is opposite to F1, and point M is between F3 and F1, and one end of F3 is connected to the other end of F2 in a vertical and conductive manner; The line length range of F4 is 64±0.2mm; F4 is opposite to F2, and one end of F4 is connected to the other end of F3 in a vertical and conductive manner; The line length range of F5 is 77±0.2mm; F5 is on the side of F1 away from F3, and one end of F5 is connected to the other end of F4 in a vertical and conductive manner; The line length range of F6 is 80±0.2mm; F6 is on the side of F2 away from F4, one end of F6 is connected to the other end of F5 in a vertical and conductive manner, and the other end of F6 is connected to a feed connection end at the corner of the upper circuit board; The lower circuit board is fixed below the upper circuit board, and a feed circuit is formed in a copper-clad manner on the top surface of the lower circuit board; the feed circuit is provided with an input connection end and four output connection ends; the four output connection ends are respectively a first connection end, a second connection end, a third connection end and a fourth connection end arranged in turn around the center of the top surface of the lower circuit board, and the signal phases output by the first connection end, the second connection end, the third connection end and the fourth connection end are respectively 0°, 90°, 180° and 270°; the four output connection ends correspond one-to-one to the four vibrator units, and between each corresponding output connection end and vibrator unit: the output connection end is connected to the feed connection end of the vibrator unit in a vertical and conductive manner; The inner conductor of the coaxial cable is electrically connected to the input connection end of the feed circuit, and the outer conductor of the coaxial cable is connected to the ground.

2. A circularly polarized near-field antenna according to claim 1, characterized in that: A reflecting surface is formed in a copper-clad manner on the bottom surface of the lower circuit board, and the orthographic projection of each vibrator unit on the bottom surface of the lower circuit board is in the reflecting surface.

3. A circularly polarized near-field antenna according to claim 1, characterized in that: The feed circuit comprises a first circuit, a second circuit and a third circuit; The first circuit comprises eight second straight line segments, which are respectively K1, K2, K3, K4, K5, K6, K7 and K8; The line length of K1 is 30.5±0.5mm, the line width of K1 is 3.3±0.1mm, the length direction of K1 is parallel to two sides of the lower circuit board, and one end of K1 is connected to the input connection end; The line length of K2 is 14.5±0.5mm, the line width of K2 is 3.3±0.1mm, and one end of K2 is connected to the other end of K1; The line length of K3 is 11.6±0.5mm, the line width of K3 is 1.9±0.1mm, K3 is on the side of K2 facing K1, and one end of K3 is connected to the other end of K2; The line length of K4 is 12±0.5mm, the line width of K4 is 1.9±0.1mm, K4 is on the side of K2 away from K3, and one end of K4 is connected to the other end of K2 connected to K3; The line length of K5 is 11.8±0.5mm, the line width of K5 is 1.9±0.1mm, K5 is on the side of K4 away from K2, and one end of K5 is connected to the other end of K4; The line length of K6 is 29.7±0.5mm, the line width of K6 is 1.9±0.1mm, K6 is on the side of K5 away from K4, and one end of K6 is connected to the other end of K5; The line length of K7 is 42.1±0.5mm, the line width of K7 is 1.9±0.1mm, K7 is on the side of K6 facing K5, and one end of K7 is connected to the other end of K6; The line length of K8 is 11.1±0.5mm, the line width of K8 is 1.9±0.1mm, K8 is on the side of K7 facing K6, and one end of K8 is connected to the other end of K7; The second circuit and the third circuit each include an isolation resistor and 11 third straight line segments, which are respectively H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, and H11; The line length of H1 is 7.9±0.3mm, and the line width of H1 is 1.9±0.1mm; The line length of H2 is 18±0.5mm, the line width of H2 is 0.9±0.1mm, and one end of H2 is connected to one end of H1; The line length of H3 is 12±0.5mm, the line width of H3 is 0.9±0.1mm, H3 is on the side of H2 away from H1, and one end of H3 is connected to the other end of H2; The line length of H4 is 17.2±0.5mm, the line width of H4 is 0.9±0.1mm, H4 is on the side of H3 facing H2, and one end of H4 is connected to the other end of H3; The line length of H5 is 10±0.5mm, the line width of H5 is 1.9±0.1mm, H5 is on the side of H4 away from H3, and one end of H5 is connected to the other end of H4; The line length of the H6 ranges from 18.3±0.5mm, the line width of the H6 ranges from 1.9±0.1mm, the H6 is on the side of the H5 facing the H4, and one end of the H6 is connected in perpendicular to the other end of the H5; The line length of the H7 ranges from 18±0.5mm, the line width of the H7 ranges from 0.9±0.1mm, the H7 is on the side of the H1 facing away from the H2, and one end of the H7 is connected in perpendicular to the end of the H1 connected with the H2; The line length of the H8 ranges from 12±0.5mm, the line width of the H8 ranges from 0.9±0.1mm, the H8 is opposite to the H3, and one end of the H8 is connected in perpendicular to the other end of the H7; The line length of the H9 ranges from 17.2±0.5mm, the line width of the H9 ranges from 0.9±0.1mm, the H9 is on the side of the H8 facing the H7, and one end of the H9 is connected in perpendicular to the other end of the H8; The line length of the H10 ranges from 10±0.5mm, the line width of the H10 ranges from 1.9±0.1mm, the H10 is arranged side by side with the H5, one end of the H10 is connected in perpendicular to the other end of the H9, and the isolation resistor is electrically connected between the H10 and the H5; The line length of the H11 ranges from 62±0.5mm, the line width of the H11 ranges from 1.9±0.1mm, the H11 is on the side of the H10 facing away from the H5, and one end of the H11 is connected in perpendicular to the other end of the H10; The second circuit is on the side of the K3 facing away from the K1, the other end of the H1 of the second circuit is connected in perpendicular to the other end of the K3, the H7 of the K3 and the second circuit is on the same side of the H1 of the second circuit, the other end of the H6 of the second circuit is connected in conductive to the first connecting end, and the other end of the H11 of the second circuit is connected in conductive to the second connecting end; The third circuit is on the side of the K8 facing away from the K7, the other end of the H1 of the third circuit is connected in perpendicular to the other end of the K8, the H2 of the K8 and the third circuit is on the same side of the H1 of the third circuit, the other end of the H6 of the third circuit is connected in conductive to the third connecting end, and the other end of the H11 of the third circuit is connected in conductive to the fourth connecting end.

4. A circularly polarized near-field antenna according to claim 1, characterized in that: Both the upper and lower circuit boards are FR-4 boards with a dielectric coefficient ranging from 4.2 to 4.

7.

5. A circularly polarized near-field antenna according to claim 1, characterized in that: The size of the length A of each of the upper and lower circuit boards ranges from 110±5mm, the thickness T1 of each of the upper and lower circuit boards ranges from 1±0.1mm, and the distance D3 between the upper and lower circuit boards ranges from 3±0.2mm.

6. A circularly polarized near-field antenna according to claim 1, characterized in that: Mounting holes are formed at the four corners of the lower circuit board, and notches for exposing the mounting holes are formed at the four corners of the upper circuit board.

7. A circularly polarized near-field antenna according to claim 1, characterized in that: Each of the corresponding output connecting ends and the feed connecting end of the vibrator unit is connected in conductive by metal column welding.

8. A circularly polarized near-field antenna according to claim 1, characterized in that: Four EVA cotton pads are clamped between the upper and lower circuit boards, and the four EVA cotton pads are arranged along the four sides of the upper circuit board.

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