TWI795083B - Circularly polarized slot antenna used in outdoor large event rfid system - Google Patents

Abstract

A circularly polarized slot antenna used in a outdoor large event RFID system includes an antenna substrate, an antenna ground plane and a microstrip line. The antenna substrate has a first surface and a second surface opposite to the first surface. The antenna ground plane is formed on the first surface of the antenna substrate, and the antenna ground plane is formed with a spiral slot structure. The microstrip line is formed on the second surface of the antenna substrate and has a first end and a second end. The first end of the microstrip line is electrically connected to a signal feeding end of the second surface of the antenna substrate, and the second end of the microstrip line is located within a projection of the spiral slot structure.

Description

Circularly Polarized Slot Antenna Applied to RFID System for Outdoor Large-scale Events

The present invention relates to a slot antenna, and especially a circularly polarized slot antenna used in outdoor large-scale event RFID systems, which can have a smaller thickness and a smaller reading weak area, so in addition to allowing the floor mat to be stored In addition to reducing the thickness of the post, it can also improve the missed reading caused by polarization orthogonality, and can adapt to the wearing methods of various postures of the radio frequency tag.

For example, outdoor large-scale events such as timing sports events usually use radio frequency identification (RFID) systems to assist the event. The RFID system requires a reader antenna to read the radio frequency tags (usually worn on the uppers of the competitors), To judge whether the contestant passes the position corresponding to the reader antenna. Common RFID UHF readers in race mats use at least one antenna as the reader antenna, which is responsible for radiating energy and receiving signals.

The operation of the RFID system is explained below. Firstly, the reader host provides energy to the reader antenna, and the reader antenna radiates the energy to the outside. When the corresponding radio frequency tag enters the energy radiation range, the radio frequency tag will be activated, and the code inside the radio frequency tag will be transmitted back to the reader antenna through radiation. Finally, the code inside the RFID tag is sent to the reader host, and the reader host will receive the code as the competition result.

Please refer to Fig. 1, Fig. 1 is a side view of a traditional race floor mat after splicing, curling or folding. Since the width of a track in a sports event is usually 6 meters, 10 meters or wider, in order to cover the width of the track, the race floor mat 1 usually must be spliced with multiple single-piece ground mats 11 in design, wherein each single piece There will be a panel antenna 12 in the ground mat 11 . Multiple pieces of single floor mats 11 will be stored by splicing, curling or folding. However, for the stored sports mat 1 , the number and thickness of the flat antennas 12 will greatly affect the convenience of using the sports mat 1 . Taking Figure 1 as an example, the thicknesses of the single-piece floor mat 11 and the flat-panel antenna 12 are 20 cm and 10 cm respectively. If the competition floor mat 1 is composed of eight single-piece floor mats 11, the thickness of the competition floor mat 1 reaches 160 cm. .

Please refer to FIG. 2 . FIG. 2 is a diagram of the antenna pattern when the traditional competition floor mat is unfolded and arranged on the field. Each of the multiple planar antennas 12 in the event floor mat 1 will have an antenna reading range area CR formed by a radiation pattern. Since the planar antenna 12 may adopt a single-polarization or dual-polarization method, it is not a circular polarization , so there is a reading weak area WR where the radio frequency tags cannot be read between two adjacent antenna reading range areas CR.

Further, the read weak region WR can be defined according to the radiation pattern of the panel antenna 12 . Although when using different radio frequency tags to send and receive, the read range will vary according to the sensitivity of the radio frequency tags, but the shape of the read range will be the same as the radiation field of the panel antenna 12, so the radiation field of the panel antenna 12 can be used Type defines the reading range of race mat 1. However, the way the mat 1 is arranged, the way the contestants pass the mat 1 and the way the radio frequency tags are worn will determine how to read the definition of the weak area WR.

When the player wears the radio frequency tag on the upper of the shoe and passes through the mat 1 of the competition, if the player crosses the antenna reading range area CR in the parallel direction of the mat 1 of the competition, it will not have much impact on the missed reading of the radio frequency tag. However, the antenna reading range area CR parallel to the competition floor mat 1 is close to the ground, because the antenna reading range area CR is not covered, so there may be chances for missed reading of the radio frequency tag, and this area is defined as the reading weak area WR. Therefore, it is necessary to find a solution that can reduce the thickness of a single floor mat and reduce the read weak region WR.

Based on at least one object of the present invention, the present invention provides a circularly polarized slot antenna for outdoor large-scale event RFID systems, which includes an antenna substrate, an antenna ground plane, and a microstrip line. The antenna substrate has a first surface and a second surface opposite to the first surface. The antenna ground plane is formed on the first surface of the antenna substrate, and the antenna ground plane is formed with a spiral slot structure. The microstrip line is formed on the second surface of the antenna substrate, and has a first end and a second end, wherein the first end of the microstrip line is electrically connected to the signal feeding end of the second surface of the antenna substrate, and the second end of the microstrip line The two ends are located within the projection of the spiral slot structure.

In an embodiment of the present invention, the circularly polarized slot antenna further includes an impedance converter, and the impedance converter is electrically connected between the signal feeding end and the first end of the microstrip line.

In an embodiment of the present invention, the circularly polarized slot antenna further includes a coaxial connector, and the coaxial connector includes a signal terminal and a ground terminal, wherein the signal terminal is electrically connected to the signal feeding terminal, and the ground terminal is electrically connected to the antenna Ground connection for the ground plane.

In an embodiment of the present invention, the coaxial cable connector is a SMA (Sub-Miniature-A) connector, the antenna substrate is an FR4 glass fiber printed circuit board, and the thickness of the antenna substrate is 1.6 cm.

In an embodiment of the present invention, wherein the spiral groove structure includes a first spiral groove and a second spiral groove, the first spiral groove is an open spiral groove, and the second spiral groove is a closed spiral groove groove.

In an embodiment of the present invention, wherein the first end of the first spiral groove is an opening on one side of the ground plane of the antenna, and the second end of the first spiral groove is located at the first internal end point of the ground plane of the antenna, And the two ends of the second spiral groove are located at the second inner end point and the third inner end point of the ground plane of the antenna.

In an embodiment of the present invention, the second end of the microstrip line is located within a projection of the second spiral groove.

In an embodiment of the present invention, the signal feed-in terminal and the ground connection terminal are located on one side of the antenna substrate.

Based on at least one object of the present invention, the present invention also provides a race mat for outdoor large-scale events, which includes a plurality of single-piece mats and a plurality of circularly polarized slot antennas. Multiple single-piece mats are used to form race mats. A plurality of circularly polarized slot antennas are respectively arranged in a plurality of single ground mats, wherein each circularly polarized slot antenna is any one of the aforementioned circularly polarized slot antennas.

In an embodiment of the present invention, the thickness of a single floor mat is 11.6 cm, and the thickness of the competition floor mat after storage is 92.8 cm.

According to the above, the above-mentioned circularly polarized slot antenna and the sensing system using the same have lower miss rate, smaller antenna size and wider reading range.

In order for the examiner to understand the technical characteristics, content and advantages of the present invention and the effects it can achieve, the present invention is described in detail below in the form of an embodiment with the accompanying drawings, and the purpose of the drawings used therein is only for illustration It is not necessarily the true proportion and precise configuration of the present invention after implementation, so it should not be interpreted or limited to the scope of rights of the present invention in actual implementation based on the proportion and configuration relationship of the attached drawings. .

Generally speaking, the polarization type of the antenna and the radio frequency tag set in the floor mat has a great influence on the reading of the radio frequency tag. Usually, the polarization type is roughly divided into linear polarization, elliptical polarization, and circular polarization. For example, when the antennas at the transmitting end and the receiving end are both linearly polarized, the antennas must be placed in the same polarization direction so that the antenna at the receiving end can receive the signal from the transmitting end. Since the antennas used in commercially available race mats with readers usually use linearly polarized antennas, when a linearly polarized radio frequency tag passes through the race mat, if the attitude of the radio frequency tag is not fixed, it may be damaged due to the positive polarization. Alternately, missed readings occur, which in turn affects the reading quality of the RFID system.

In order to improve the missed reading caused by polarization orthogonality, the present invention uses an angled spiral slot structure for design, realizes a circularly polarized slot antenna, and sets the circularly polarized slot antenna in the race mat, Wearing styles in various postures to strain radio frequency tags. Furthermore, the present invention uses the thinness of the slot antenna structure to make the overall structure of the race floor mat lighter and thinner. At the same time, the thin structure is conducive to the design of folding, so that the overall thickness of the race floor mat after storage is reduced. more convenient.

Furthermore, due to the low directivity of the antenna pattern of the circularly polarized slot antenna, compared with the flat-panel antenna type used on the commercially available race mat, the circularly polarized slot antenna can achieve reading weak areas when used on the race mat shrinking effect. On the other hand, with the spiral slot design of the angled spiral slot structure, the antenna can have circular polarization characteristics, which can avoid missed readings caused by the orthogonal polarization of the linearly polarized antenna and the linearly polarized tag. situation. Due to the design of the spiral slot angle in the spiral slot structure, not only can the spiral slot structure be standardized, but also the spiral slot structure can be changed according to the needs of the spiral slot structure conditions (such as linear width, Angle, spacing, symmetry and number of spiral grooves), with variability to achieve the effect of customization. Even, due to the characteristic of standardization, the effect of a modular spiral slot structure can be further produced, so that the overall consistency of the spiral slot structure can be improved, which is helpful to process efficiency and improve quality.

First, please refer to FIG. 3 . FIG. 3 is a top perspective view of the race floor mat according to the embodiment of the present invention when it is unfolded and arranged on the race field. In this embodiment, the width of the competition ground mat 3 is approximately 8 meters after being deployed, and the competition ground mat 3 is composed of eight single-block ground mats 31 with a width of 1 meter, wherein each single-block ground mat 31 A circularly polarized slot antenna 32 is provided in it.

Please refer to FIG. 4 . FIG. 4 is a side view of the race floor mat according to the embodiment of the present invention after splicing, curling or folding. Multiple pieces of single floor mats 31 will be stored by splicing, curling or folding. For the event ground mat 3 after being accommodated, since the circularly polarized slot antenna 32 is adopted, the thickness of the circularly polarized slot antenna 32 can be changed to 1.6 cm, and the thickness of the single ground mat 31 can be changed to 1.6 cm. It is 11.6 centimeters, and the thickness of the race mat 3 after storage is 92.8 centimeters, so compared with the race mats currently available on the market, the present invention can greatly reduce the thickness of the race mat 3 after storage.

Please refer to Figure 5 and Figure 6 at the same time, Figure 5 is a top perspective view of a circularly polarized slot antenna applied to an outdoor large-scale event RFID system according to an embodiment of the present invention, and Figure 6 is a top perspective view of an embodiment of the present invention applied to an outdoor large-scale event Bottom view of circularly polarized slot antenna for RFID system. The circularly polarized slot antenna 32 includes an antenna substrate 321 , an antenna ground plane 322 and a microstrip line 325 . The antenna substrate 321 has a first surface and a second surface opposite to the first surface. The antenna ground surface 322 is formed on the first surface of the antenna substrate 321 , and the antenna ground surface 322 is formed with a spiral slot structure 323 . The microstrip line 325 is formed on the second surface of the antenna substrate 321, and has a first end and a second end, wherein the first end of the microstrip line 325 is electrically connected to the signal feeding end of the second surface of the antenna substrate 321, and the microstrip line 325 is electrically connected to the second surface of the antenna substrate 321. The second end of the strip wire 325 is located within the projection of the spiral slot structure 323 .

Preferably, the circularly polarized slot antenna 32 further includes an impedance converter 326 and a coaxial connector (not shown), and the impedance converter 326 is electrically connected between the signal feed end and the first end of the microstrip line 325 between. The coaxial connector includes a signal terminal and a ground terminal, wherein the signal terminal is electrically connected to the signal feed-in terminal, and the ground terminal is electrically connected to the ground connection terminal 324 of the antenna ground plane 322 . The coaxial connector is, for example, an SMA (Sub-Miniature-A) connector, and the antenna substrate 321 is an FR4 glass fiber printed circuit board, and the thickness of the antenna substrate 321 is 1.6 cm. The thickness of the antenna substrate 321 is only 1.6 cm, so the thin structure is very convenient for designing the race floor mat 3 , and can make the overall thickness of the house race floor mat 3 quite light and thin.

In this embodiment, the signal feed-in terminal and the ground connection terminal 324 are located on one side (left side) of the antenna substrate 321 , but the present invention is not limited by the positions of the signal feed-in terminal and the ground connection terminal 324 . In addition, the spiral slot structure 323 may be formed by using the antenna substrate 321 as a base, first forming the antenna ground plane 322 , and then undergoing exposure, development and etching. However, it should be noted that the method of forming the antenna ground plane 322 with the spiral slot structure 323 is not intended to limit the present invention.

The above antenna design is to slot the angled spiral slot structure 323 into the ground plane 322 of the antenna, and use a microstrip line 325 with an impedance converter 326 to feed the signal. The spiral slot structure 323 can make the circularly polarized slot antenna 32 generate currents in different directions at different current phases to achieve a circularly polarized effect. The structure of the impedance converter 326 is designed to allow better impedance matching between the circularly polarized slot antenna 32 and the coaxial connector of the fed signal, allowing the circularly polarized slot antenna 32 to be more stable in actual use. The converter 326 is designed in a conical shape, for example, but the invention is not limited thereto.

Further, in this embodiment, the spiral groove structure 323 includes a first spiral groove 3231 and a second spiral groove 3232, the first spiral groove 3231 is an open spiral groove, and the second spiral groove 3232 is Close the screw groove. A first end of the first spiral groove 3231 is an opening on one side (upper side) of the antenna ground plane 322 , and a second end of the first spiral groove 3231 is located at a first inner end of the antenna ground plane 322 . Both ends of the second spiral slot 3232 are located at the second inner end point and the third inner end point of the antenna ground plane 322 , and the second end of the microstrip line 325 is located within a projection of the second spiral slot 3232 . In addition, it should be noted that the structural design of the above-mentioned spiral slot structure 323 is not intended to limit the present invention, and the linear width, angle, spacing, symmetry and number of spiral slots of the spiral slot structure 323 can be adjusted according to actual needs. design.

Please refer to FIG. 7 . FIG. 7 is a YZ plane field diagram of a circularly polarized slot antenna and a linearly polarized panel antenna applied to an outdoor large-scale event RFID system according to an embodiment of the present invention operating at 910 megahertz. By observing the horizontal polarization gain curve C11, vertical polarization gain curve C12 of the linearly polarized panel antenna and the horizontal polarization gain curve C13 and vertical polarization gain curve C14 of the circularly polarized slot antenna, one can know the circularly polarized slot The antenna has a definite improvement in reading weak areas.

Next, please refer to Tables 1 to 3, which are respectively the vertical distances of the circularly polarized slot antenna and the linearly polarized panel antenna applied to the outdoor large-scale event RFID system in the embodiment of the present invention at a vertical distance of 10 cm, 50 cm, and 100 cm. YZ reading range measurement results under conditions. It can be known from Table 1 that at a vertical distance of 10 cm, the circularly polarized slot antenna and the linearly polarized panel antenna can generate induction in both horizontal and vertical polarization directions, but if you look at the data in detail, The overall read range of the circularly polarized slot antenna is slightly greater than that of the linearly polarized panel antenna.

Comparing Table 2 and Table 3, when the vertical distance is 50 cm and 100 cm, the circularly polarized slot antenna still maintains good sensing effect no matter in the direction of horizontal polarization or vertical polarization, and the reading range is wider It is obviously larger than the measurement result when the vertical distance is 10 cm. In contrast, the linearly polarized panel antenna cannot produce sensing effect in some directions, and even loses the reading ability of vertical polarization when the vertical distance is 100 cm. Table 1. Height (Z) 10 (cm) type Circular Polarization Slot Antenna Linearly Polarized Panel Antenna direction horizontal polarization vertical polarization horizontal polarization vertical polarization x 61 109 27 71 Y 35 61 44 26 -X 56 70 14 53 -Y 62 112 twenty three 13 Table 2. Height (Z) 50 (cm) type Circular Polarization Slot Antenna Linearly Polarized Panel Antenna direction horizontal polarization vertical polarization horizontal polarization vertical polarization x 110 133 Unable to read 91 Y 111 93 76 Unable to read -X 71 84 Unable to read 67 -Y 120 177 75 Unable to read table 3. Height (Z) 100 (cm) type Circular Polarization Slot Antenna Linearly Polarized Panel Antenna direction horizontal polarization vertical polarization horizontal polarization vertical polarization x 181 115 Unable to read Unable to read Y 64 122 85 Unable to read -X 142 87 Unable to read Unable to read -Y 133 215 80 Unable to read

From the YZ plane field diagram and the measurement results of the YZ reading range, it can be known that the circularly polarized slot antenna provided by the present invention cannot achieve small size and convenient application, and can significantly improve the reading weak area, and even increase the overall read range.

Based on the above, the present invention uses the light and thin structure of the circularly polarized slot antenna, and applies it to the mat for outdoor large-scale events, and has the following technical effects: (1) Using the circularly polarized slot antenna The characteristic of the low directivity of the radiation field pattern reduces the reading weak area; (2) The angled helical slot structure of the circularly polarized slot antenna is used to achieve the circular polarization characteristics, so as to avoid the linear antenna pole in the past (3) The design of the angle of the spiral slot in the spiral slot structure enables the spiral slot structure to change the conditions of the spiral slot (such as linear width, angle, spacing, symmetry, and number of spiral slots), so overall, the circularly polarized slot antenna has variability and can maintain consistency, which helps process efficiency and improves quality.

In summary, the circularly polarized slot antenna applied to the outdoor large-scale event RFID system provided by the embodiment of the present invention can accurately achieve the expected use effect, and the present invention has not been disclosed before the application, and it is fully in line with The provisions and requirements of patent law. ￠It is really convenient to file an application for an invention patent in accordance with the law and ask for the review and approval of the patent. However, the illustrations and descriptions disclosed above are only preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention; those who are familiar with this technology generally make other works according to the characteristic scope of the present invention. Equivalent changes or modifications shall be regarded as not departing from the design scope of the present invention.

1: Race floor mat 11: Single floor mat 12: Panel Antenna CR: Antenna Read Range Area WR: read weak area 3: Race floor mat 31: Single floor mat 32: Circular Polarization Slot Antenna 321: Antenna substrate 322: Antenna ground plane 323: spiral slot structure 3231: The first spiral groove 3232: Second spiral groove 324: Ground connection terminal 325: microstrip line 326: Impedance converter C11: Horizontal polarization gain curve C12: Vertical polarization gain curve C13: Horizontal polarization gain curve C14: Vertical polarization gain curve

Fig. 1 is a side view of a traditional racing floor mat after splicing, curling or folding. Fig. 2 is a diagram of the antenna pattern when the traditional competition floor mat is unfolded and arranged on the field. Fig. 3 is a top perspective view of the race floor mat according to the embodiment of the present invention when it is unfolded and arranged on the playing field. Fig. 4 is a side view of the race floor mat according to the embodiment of the present invention after splicing, curling or folding. Fig. 5 is a top perspective view of a circularly polarized slot antenna applied to an outdoor large-scale event RFID system according to an embodiment of the present invention. Fig. 6 is a bottom view of a circularly polarized slot antenna applied to an outdoor large-scale event RFID system according to an embodiment of the present invention. Fig. 7 is a YZ plane field diagram of a circularly polarized slot antenna and a linearly polarized panel antenna applied to an outdoor large-scale event RFID system according to an embodiment of the present invention operating at 910 megahertz.

32: Circular Polarization Slot Antenna

321: Antenna substrate

322: Antenna ground plane

323: spiral slot structure

3231: the first spiral groove

3232: Second spiral groove

324: Ground connection terminal

325: microstrip line

326: Impedance converter

Claims (9)

A circularly polarized slot antenna for outdoor large-scale event RFID systems, comprising: an antenna substrate having a first surface and a second surface opposite to the first surface; an antenna ground plane formed on the antenna substrate The first surface of the antenna ground plane is formed with a spiral slot structure, wherein the spiral slot structure includes a first spiral slot and a second spiral slot, the first spiral slot is an opening a spiral groove, the second spiral groove is a closed spiral groove; and a microstrip line is formed on the second surface of the antenna substrate and has a first end and a second end, wherein the microstrip The first end of the line is electrically connected to a signal feeding end of the second surface of the antenna substrate, and the second end of the microstrip line is located within a projection of the spiral slot structure. The circularly polarized slot antenna according to claim 1 further includes: an impedance converter electrically connected between the signal feeding end and the first end of the microstrip line. The circularly polarized slot antenna according to claim 2, further comprising: a coaxial connector, including a signal terminal and a ground terminal, wherein the signal terminal is electrically connected to the signal feed-in terminal, and the ground terminal is electrically connected to the antenna A ground connection terminal of the ground plane. Circularly polarized slot antenna as described in claim 3, wherein the coaxial cable connector is a SMA (Sub-Miniature-A) connector, the antenna substrate is a FR4 glass fiber printed circuit board, and a thickness of the antenna substrate is 1.6 cm. The circularly polarized slot antenna as claimed in item 4, wherein a first end of the first helical slot is an opening on one side of the ground plane of the antenna, and a second end of the first helical slot is located at the A first internal terminal of the antenna ground plane and two ends of the second spiral groove are located at a second internal terminal and a third internal terminal of the antenna ground plane. The circularly polarized slot antenna as claimed in claim 5, wherein the second end of the microstrip line is located within a projection of the second spiral slot. The circularly polarized slot antenna according to claim 5, wherein the signal feed-in terminal and the ground connection terminal are located on one side of the antenna substrate. A race mat, comprising: a plurality of single-piece mats, used to form the race mat; and a plurality of circularly polarized slot antennas, respectively arranged in the plurality of single-piece mats, wherein the circularly polarized Each of the slot antennas is a circularly polarized slot antenna according to one of claims 1 to 7. The race mat as described in Claim 8, wherein a thickness of the single mat is 11.6 cm, and a thickness of the race mat after storage is 92.8 cm.

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