WO2016127595A1

WO2016127595A1 - Radio frequency identification (rfid) tag antenna

Info

Publication number: WO2016127595A1
Application number: PCT/CN2015/086048
Authority: WO
Inventors: 蔡凌云
Original assignee: 中兴通讯股份有限公司
Priority date: 2015-02-13
Filing date: 2015-08-04
Publication date: 2016-08-18
Also published as: CN204497366U

Abstract

Provided is a radio frequency identification (RFID) tag antenna. The antenna comprises: a first dielectric substrate; a second dielectric substrate; a feeding structure for generating a circularly polarised wave, wherein a first structure of the feeding structure is located on the second dielectric substrate, a second structure of the feeding structure is located between the first dielectric substrate and the second dielectric substrate and is in contact with the first dielectric substrate and the second dielectric substrate, and the first structure and the second structure perform coupled feeding; and a slot formed by a radiation chip encircling the first dielectric substrate. The antenna further comprises: an excitation structure for re-generating a circularly polarised wave on the circularly polarised wave, provided on the surface of the first dielectric substrate, and located in the slot. By means of the present invention, the circularly polarised wave generated by the feeding structure is re-excited using the excitation structure, such that the working bandwidth of the circularly polarised wave is wider, identification distance is longer, an ultra-high frequency band can be covered, and the problem in the related art that a circularly polarised antenna is narrow in bandwidth is solved.

Description

Radio frequency identification RFID tag antenna

Technical field

The present invention relates to the field of communications, and in particular to a radio frequency identification (RFID) tag antenna.

Background technique

Radio Frequency Identification (RFID) technology is a non-contact automatic identification technology that transmits RF signals through reading and writing devices. RFID tags transmit information stored in the chip by the energy obtained by the induced current. And identify specific targets without identifying the system to establish mechanical or optical connections with specific targets; RFID technology has great application potential in the field of intelligent control, and is widely used in logistics, management and non-contact payment, improving management efficiency, Saving labor costs.

The RFID application system is such that the antenna obtains the energy obtained from the induced current through the RF front-end circuit and sends the digital signal to the logic control circuit for information processing, and sends the information to be recovered back to the reader from the RF front-end circuit. It can be seen that the RFID tag antenna is crucial in the process of data communication between the RFID card and the reader. The RFID card chip is passive, and needs to obtain sufficient energy in the electromagnetic field generated by the tag antenna to start its circuit operation; on the other hand, the tag antenna determines the communication channel and communication mode between the RFID card and the reader. According to the needs of different application fields and actual environments, RFID electronic tags are divided into frequency bands, including low-frequency high-frequency and ultra-high frequency. Different frequency bands work in different fields. The difference is in the sensing distance, and the low-frequency sensing distance is the shortest. Applications such as access control cards, Ultra-high frequency sensing distance is the farthest, but it is affected by the environment.

In the RFID system, the installation position and direction of the electronic tag are specified, but since the article has the possibility of continuous movement, the radiation direction of the electronic tag antenna also changes with the movement of the article, and the reading and writing device is easy to read data. A missed read condition requires the antenna to have polarization characteristics. Therefore, in the RFID system, a circularly polarized antenna is needed, which can effectively receive the changed signal and reduce the missed reading phenomenon. There are several methods for implementing circularly polarized antennas in the related art: (1) chamfering on the vibrator; (2) feeding the vibrator diagonally; (3) feeding with a phase shift of 90°. The circular polarization performance and port performance of the above-mentioned methods for realizing circularly polarized antennas are relatively weak, so that signal differences often occur; the transmission distance is short and the coverage is small when used; in addition, the antennas are bulky in these ways. The circularly polarized antenna has problems such as difficulty in control of the shaft ratio, narrow bandwidth, high cost, and difficulty in mounting the antenna.

In view of the narrow bandwidth of the circularly polarized antenna in the related art, an effective solution has not been proposed yet.

Summary of the invention

It is an object of the present invention to provide an RFID tag antenna to at least solve the problem of narrow bandwidth of a circularly polarized antenna in the related art.

According to an aspect of the present invention, an RFID tag antenna is provided, the antenna comprising: a first dielectric substrate; a second dielectric substrate; a feed structure configured to generate a circularly polarized wave, wherein the feed structure The first structure is located on the second dielectric substrate, and the second structure of the feed structure is located between the first dielectric substrate and the second dielectric substrate, and is connected to the first medium The first substrate and the second structure are coupled to each other; the slot formed by the radiation patch surrounding the first dielectric substrate further includes: being disposed in the circle An excitation structure for generating a circularly polarized wave on the polarized wave is disposed on the surface of the first dielectric substrate and located in the slot.

Optionally, the feed structure consists of a feed line and a floor coupled to the feed line.

Optionally, the excitation structure comprises: a branch of two curved structures, the convex surface of the branch is oppositely disposed in the slot, connected to the radiation patch, and the diameter extension line of the branch is The extension lines of the feeders are orthogonal.

Optionally, the size of the branches is adjustable.

Optionally, the slot is annular.

Optionally, the slot is a square, and the two curved branches are oppositely disposed at opposite corners of the square.

Optionally, the first structure is a feed line, and the second structure is a cross-coupling slot.

Optionally, the size of the cross coupling slot is adjustable.

Optionally, the size of the branch or the cross coupling groove is adjusted according to the circular polarization axis ratio.

Optionally, the first dielectric substrate and the second dielectric substrate are made of polytetrafluoroethylene.

In the present invention, by providing an excitation structure on the surface of the first dielectric substrate, the excitation structure re-energizes the circularly polarized wave generated by the feeding structure, so that the working bandwidth of the circularly polarized wave is wider, and the recognition distance is further. It can cover the UHF frequency band and solve the problem of narrow bandwidth of the circularly polarized antenna in the related art.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

1 is a schematic diagram of an RFID tag antenna in accordance with an embodiment of the present invention;

2 is a top plan view of an RFID tag antenna in accordance with an alternative embodiment of the present invention;

3 is a side elevational view of an RFID tag antenna in accordance with an alternative embodiment of the present invention;

4 is a schematic diagram of a middle layer of an RFID tag antenna in accordance with an alternative embodiment of the present invention;

5 is a bottom diagram of the RFID tag antenna in accordance with an alternative embodiment of the present invention;

6 is a schematic diagram of a surface layer of an RFID tag antenna in accordance with an alternative embodiment of the present invention.

detailed description

It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments.

The present embodiment provides an RFID tag antenna. FIG. 1 is a schematic diagram of an RFID tag antenna according to an embodiment of the present invention. As shown in FIG. 1 , the RFID tag antenna includes: a first dielectric substrate 101; a second dielectric substrate 102; a feed structure 103 configured to generate a circularly polarized wave, wherein the first structure of the feed structure is located on the second dielectric substrate, and the second structure of the feed structure is located between the first dielectric substrate 101 and the second dielectric substrate 102 And contacting the first dielectric substrate 101 and the second dielectric substrate 102, the first structure and the second structure are coupled to feed; the slot 104 formed by the radiation patch surrounding the first dielectric substrate 101 further includes:

The excitation structure 105, which is disposed to generate a circularly polarized wave again on the circularly polarized wave, is disposed on the surface of the first dielectric substrate 101 and is located in the opening 104.

In the embodiment, by providing an excitation structure 105 on the surface of the first dielectric substrate 101, the excitation structure 105 re-energizes the circularly polarized wave generated by the feeding structure 103, so that the working bandwidth of the circularly polarized wave is wider, and further The recognition distance is farther, and the UHF frequency band can be covered, which solves the problem of narrow bandwidth of the circularly polarized antenna in the related art.

It should be noted that FIG. 1 is a schematic diagram of the embodiment, and the position and shape of the above-mentioned excitation structure 105 in the actual RFID tag antenna can be adjusted according to actual conditions; the following embodiment will be used in the optional embodiment of this embodiment. The excitation structure 105 is exemplified.

The feed structure involved in this embodiment is composed of a feed line and a floor coupled to the feed line; optionally, the first structure is a feed line, and the second structure is a cross-coupling slot, and the cross-coupling slot is disposed on On the floor, the dimensions of the cross-coupling groove, such as length and/or width, can be adjusted according to the circular polarization axis ratio.

In addition, in an optional embodiment of the embodiment, the excitation structure 105 includes: two branches of the curved branches, the convex surfaces of the branches are oppositely disposed in the slot, connected with the radiation patch, and the diameter extension line and the feeder of the branch The extension lines are orthogonal. It should be noted that the size of the branch can also be adjusted according to the circular polarization axis ratio.

Alternatively, the spacing between the cross coupling slot and the branch can be adjusted as needed.

In still another alternative embodiment of the present embodiment, the slot 104 involved in this embodiment may be circular or square, but the shapes of the above two slots do not constitute a limitation of the present invention, and may be based on actual conditions. Need to adjust to the corresponding shape. When the slots are square, the two curved structures are oppositely disposed at opposite corners of the square.

For the first dielectric substrate 101 and the second dielectric substrate 102 involved in the embodiment, the square FR-4 may be polytetrafluoroethylene. Through the first dielectric substrate 101 and the second dielectric substrate 102, the RFID tag antenna of the embodiment may be a Printed Circuit Board (PCB) structure to facilitate integration with the circuit board.

The embodiment is described below in conjunction with an optional embodiment of the present invention;

The optional embodiment provides an RFID tag antenna with a circular polarization theory. In the alternative embodiment, the feed structure adopts a cross-coupling structure, which can generate a circularly polarized wave when the circularly polarized wave reaches the surface layer. When radiating the patch, the radiation patch is square-grooved and excited by the added additional annular branch (excitation structure), which disturbs the surface electric field distribution of the square groove, and the two near-end resonant modes have a phase difference of 90 degrees. Thus, the circularly polarized wave is excited again on the circularly polarized wave, so that the work The bandwidth is wider and the circular polarization axis ratio is better. With this new structure of the RFID tag antenna, the circular polarization axis ratio can be effectively controlled, the bandwidth can be broadened, and the antenna size can be reduced.

The shape of the surface radiation patch may be other shapes, such as a circular shape, in addition to the square described above; in addition, the size of the additional annular branch (excitation structure) of the surface layer and the length and width of the cross coupling groove of the middle layer, It can be adjusted according to the circular polarization axis ratio; the spacing between the additional ring branch and the cross coupling groove can be adjusted to produce different circular polarization effects;

After adopting the above structure, compared with the conventional RFID antenna, the RFID tag antenna of the alternative embodiment has a long reading distance and a large coverage range; the reliability of reading the tag is higher than that of the conventional UHF RFID antenna; The antenna is small in size, the axis ratio of the antenna is controllable, the cost is low, and the installation is simple.

The optional embodiment will be described in detail below with reference to the accompanying drawings;

2 is a top plan view of an RFID tag antenna in accordance with an alternative embodiment of the present invention, and FIG. 3 is a side elevational view of an RFID tag antenna in accordance with an alternative embodiment of the present invention, as shown in FIGS. 2 and 3, the RFID tag antenna includes The radiation patch 201, the additional annular branch 202, the cross-shaped coupling groove 203, the floor 204, the feed line 205, and the dielectric substrate 206. Wherein, the dielectric substrate 206 is a square FR-4 epoxy resin copper clad laminate

4 is a schematic diagram of a middle layer of an RFID tag antenna according to an alternative embodiment of the present invention, and FIG. 5 is a schematic diagram of a bottom layer of the RFID tag antenna according to an alternative embodiment of the present invention, as shown in FIGS. 4 and 5, the optional implementation In the example, the feed structure adopts a cross-coupling structure, and the feed line 205 from the bottom layer is coupled and fed through a middle cross-coupling groove 203 at one corner of the square to generate a circularly polarized wave, and the length and the width of the cross-coupling groove are adjusted. Thereby, the axial ratio of the circular polarization is adjustable.

6 is a schematic diagram of a surface layer of an RFID tag antenna according to an alternative embodiment of the present invention. As shown in FIG. 6, the surface electric field of the square slot can be disturbed due to the additional annular branches 202 at two opposite corners of the square radiating groove 201 of the surface layer. Distribution, the two near-end resonant modes have a phase difference of 90 degrees, so that the circularly polarized waves are excited again on the arriving circularly polarized waves, so that the working bandwidth is wider, and the radius of the additional branches can be adjusted. Thereby achieving a 3dB axial ratio.

According to the manner of the foregoing optional embodiment, in an application scenario of the optional embodiment, the material of the RFID tag antenna may be a polytetrafluoroethylene material, and the dielectric substrate has a dielectric constant of 4.4. The overall size of the antenna is 90mm*90mm. The frequency band of the RFID tag antenna can be from 850MHz to 990MHz, and the impedance bandwidth is 140MHz. It is improved from the traditional 100MHz to 140MHz, completely covering the Chinese UHF band (920MHz ~ 925MHz), the antenna The axial ratio is 3dB, which in turn achieves the stable effect of the RFID wide-band tag reading distance.

In addition, the feeding in the alternative embodiment is a 50 ohm feed, the feed line width is 1.52 mm, the length of the cross-shaped groove is 40 mm, the width is 5 mm, the outer radius of the additional branch is 30 mm, and the inner radius is 27 mm. The values of the units in the foregoing embodiment are only used for example, and the sizes of the foregoing units may be adjusted according to different application scenarios. It can be seen that the optional implementation has a small size, a long recognition distance, and a stable Full coverage of China's UHF frequency band, simple production, low cost, etc., has a good market prospects.

In this alternative embodiment, for a circularly polarized RFID tag antenna, the size of the cross coupling slot is adjusted, and the additional branch is used. The size of the radius of the section, and the spacing between them, can get the required working frequency band and the required circular polarization axis ratio.

Industrial Applicability: With the antenna provided by the present invention, an excitation structure is disposed on the surface of the first dielectric substrate, and the excitation structure re-energizes the circularly polarized wave generated by the feeding structure, so that the working bandwidth of the circularly polarized wave is wider, and further The recognition distance is farther, and the UHF frequency band can be covered, which solves the problem of narrow bandwidth of the circularly polarized antenna in the related art.

The above is only an alternative embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A radio frequency identification RFID tag antenna, the antenna comprising: a first dielectric substrate; a second dielectric substrate; a feeding structure for generating a circularly polarized wave, wherein the first structure of the feeding structure is located at the a second dielectric substrate, the second structure of the feed structure is located between the first dielectric substrate and the second dielectric substrate, and is in contact with the first dielectric substrate and the second dielectric substrate, the first structure and the second The structure is coupled to feed; the slot formed by the radiation patch surrounding the first dielectric substrate further includes:

An excitation structure for generating a circularly polarized wave on the circularly polarized wave is disposed on a surface of the first dielectric substrate and located in the groove.
The RFID tag antenna of claim 1 wherein said feed structure is comprised of a feed line and a floor coupled to said feed line.
The RFID tag antenna of claim 2, wherein the excitation structure comprises: two arcuately structured branches, the convex surfaces of the branches being oppositely disposed in the slot, connected to the radiation patch, The diameter extension line of the branch is orthogonal to the extension of the feed line.
The RFID tag antenna of claim 3 wherein the size of the branches is adjustable.
The RFID tag antenna according to any one of claims 1 to 4, wherein the slot is annular.
The RFID tag antenna according to claim 4, wherein said slit is square, and said two curved branch convex surfaces are oppositely disposed at opposite corners of said square.
The RFID tag antenna according to any one of claims 2 to 4, wherein the first structure is a feed line and the second structure is a cross-coupling slot.
The RFID tag antenna of claim 7, wherein the size of the cross coupling slot is adjustable.
The RFID tag antenna according to claim 4 or 6 or 8, wherein a size of the branch or the cross coupling groove is adjusted in accordance with the circular polarization axis ratio.
The RFID tag antenna according to any one of claims 1 to 4, 6 or 8, wherein the first dielectric substrate and the second dielectric substrate are made of polytetrafluoroethylene.