WO2018149248A1

WO2018149248A1 - Ultra-high-frequency near-field rfid antenna and ultra-high-frequency near-field rfid reader

Info

Publication number: WO2018149248A1
Application number: PCT/CN2017/120359
Authority: WO
Inventors: 蔡凌云
Original assignee: 中兴通讯股份有限公司
Priority date: 2017-02-20
Filing date: 2017-12-29
Publication date: 2018-08-23
Also published as: CN108461911A

Abstract

An ultra-high-frequency near-field RFID antenna and an ultra-high-frequency near-field RFID reader. The antenna comprises a first dielectric layer (6A), a second dielectric layer (6B) and a plurality of short-circuiting posts (3A, 3B, 3C and 3D), wherein a floor copper-clad layer (5) is arranged between the first dielectric layer (6A) and the second dielectric layer (6B); the first dielectric layer (6A) is provided with two micro-strip power splitters (1A and 1B); each of the micro-strip power splitters (1A and 1B) comprises two output arms, and orthogonal feeding is carried out between the two output arms; each output arm is respectively connected to one end of one short-circuiting post; the floor copper-clad layer (5) is provided with via holes for the short-circuiting posts (3A, 3B, 3C and 3D) to pass through; and the second dielectric layer (6B) is provided with two first radiation patches (L1 and L2) and at least one second radiation patch (2) coupled to the first radiation patches (L1 and L2), and the other end of each of the short-circuiting posts (3A, 3B, 3C and 3D) is connected to the first radiation patches (L1 and L2).

Description

Ultra-high frequency near field RFID antenna and ultra high frequency near field RFID reader

Technical field

This article relates to but not limited to the field of Radio Frequency Identification (RFID) technology, and in particular relates to an ultra-high frequency near field RFID antenna and an ultra high frequency near field RFID reader.

Background technique

Radio frequency identification is a technology that uses a radio frequency method to perform contactless two-way data communication to identify targets. Radio frequency identification systems generally consist of a reader (Reader) and an electronic tag (Tag). The RFID system transmits and receives electromagnetic waves through an antenna, thereby realizing recognition of the electronic tag by the reader/writer.

RFID systems operate primarily in the low frequency (LF), high frequency (HF), ultra high frequency (UHF) and microwave bands. The low-frequency and high-frequency RFID systems are identified by inductive coupling, and the reading distance is close. The UHF and microwave RFID systems are identified by electromagnetic wave transmission, and the reading distance is far.

Summary of the invention

The following is an overview of the topics detailed in this document. This Summary is not intended to limit the scope of the claims.

Embodiments of the present invention provide an ultra-high frequency near field RFID antenna and an ultra high frequency near field RFID reader/writer.

The embodiment of the invention is implemented as follows:

An embodiment of the present invention provides an ultra-high frequency near field RFID antenna, including a first dielectric layer, a second dielectric layer, and a plurality of shorting columns, and a floor copper layer is disposed between the first dielectric layer and the second dielectric layer. ,among them,

The first dielectric layer is provided with two microstrip power splitters, each microstrip splitter includes two output arms and orthogonal feeds between the two output arms, one for each output arm and one for each output arm One end of the shorting column is connected;

a through hole for passing through the shorting column is disposed on the floor copper layer;

The second dielectric layer is provided with two first radiating patches and at least one second radiating patch coupled to the first radiating patch, and the other end of the shorting post is connected to the first radiating patch.

Optionally, the first radiation patch is an "L"-shaped structure comprising two branches, the two branches being adjustable in length and perpendicular to each other.

Optionally, the length of the two branches is adjusted by adjusting the length of the copper foil of the surface of the two branches.

Optionally, the two output arms of the microstrip power splitter have a symmetrical curved structure.

Optionally, the microstrip power splitter is an "E" type or a "W" type structure.

Optionally, the length difference between the two output arms is adjusted to be 1/4 of the operating wavelength of the antenna by adjusting the length of the copper foil on the surfaces of the two output arms.

Optionally, the second radiation patch is a ring structure.

Optionally, adjusting the impedance characteristic of the antenna exhibits pure resistivity by adjusting a width of a copper foil of the surface of the second radiation patch and a spacing between the first radiation patch and the second radiation patch.

Optionally, the first dielectric layer and the second dielectric layer are polytetrafluoroethylene epoxy dielectric sheets.

An embodiment of the present invention further provides an ultra-high frequency near field RFID reader, comprising the UHF near field RFID antenna of any of the above.

The embodiments of the present invention have the following beneficial effects:

The ultra-high frequency near-field RFID antenna and the ultra-high frequency near-field RFID reader provided by the embodiments of the present invention perform orthogonal feeding through two output arms of the microstrip power splitter, and the electromagnetic wave after passing through the short-circuited column reaches the first The first radiation patch of the two dielectric layers generates a circularly polarized wave, and then is coupled to the second radiation patch for radiation, extending the diameter of the antenna, thereby effectively reducing the size of the antenna;

Further, the first radiating patch is an "L"-shaped structure in which two branches are adjustable in length and perpendicular to each other. By adjusting the length of the two branches, the electromagnetic waves reaching the two branches generate a 90-degree phase shift, first. The circularly polarized wave is excited again on the radiation patch, which makes the working bandwidth of the antenna wider and the circular polarization axis ratio better.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF abstract

1 is a top plan view of an ultra-high frequency near field RFID antenna according to an embodiment of the present invention;

2 is a side view of an ultra high frequency near field RFID antenna according to an embodiment of the present invention;

3 is a schematic structural diagram of a first dielectric layer according to an embodiment of the present invention;

4 is a schematic structural view of a floor copper layer according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a second dielectric layer according to an embodiment of the present invention.

Wherein: L1, L2 are the first radiation patch; 1A, 1B are the microstrip power divider; 2 is the second radiation patch; 3A, 3B, 3C, 3D are short circuit columns; 4 is the feed port; 5 is the floor A copper layer is applied; 6A is a first dielectric layer; and 6B is a second dielectric layer.

Embodiments of the invention

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Usually near-field RFID antennas operate in the HF band. Such antennas activate tags by near-field coupling. However, due to their operating frequency limitations, the size of such antennas is relatively large compared to higher frequency bands such as UHF band antennas, and antennas. The read range is also not too far away due to the limited read mode of near field coupling. The common far-field antennas generally work in the UHF band, and the antennas are small in size, but such antennas use radiant energy to activate the tags, which are suitable for long-distance reading and writing; the gain is generally small in the near-field radiation region of the antenna. Cannot be applied to near-field read and write applications.

In recent years, UHF near-field RFID antennas have been studied a lot, and various loop antennas based on segmented coupled loop antenna, left-hand material loaded loop antenna, lumped capacitor loading phase compensation, and so on have been designed. The common feature of these antennas is that the currents on the ring remain in phase, which can induce a stronger and more uniform magnetic field in the annular region, but these antennas are now bulky and difficult to use for low-power mobile portable handheld devices. in.

The first dielectric layer is provided with two microstrip power splitters, each microstrip splitter includes two output arms and orthogonal feeds between the two output arms, each output arm and a short circuit One end of the column is connected;

a through hole for passing the short-circuited column is disposed on the floor copper-clad layer;

Optionally, the length of the two branches is adjusted by adjusting the length of the copper foil of the surface of the two branches. When the two branches of the first radiation patch are of equal length and perpendicular to each other, the electromagnetic waves reaching the two branches produce a 90 degree phase shift, producing a circularly polarized wave.

It should be noted that the structure of the microstrip power divider of the embodiment of the present invention may be any structure including two output arms, and the two output arms may be straight lines or symmetric curves.

Optionally, the length difference between the two output arms is adjusted to be 1/4 of the operating wavelength of the antenna by adjusting the length of the copper foil on the surfaces of the two output arms. When the length difference between the two output arms of the microstrip power splitter is 1/4 of the operating wavelength of the antenna, the electromagnetic waves reaching the two shorted posts on the output arm produce a 90 degree phase shift, thereby generating a circularly polarized wave.

Optionally, the second radiation patch is a ring structure. By setting the second radiating patch to a ring structure, the diameter of the antenna is extended, thereby reducing the size of the antenna.

Optionally, the impedance characteristic of the antenna is achieved by adjusting a width of a copper foil on a surface of the second radiation patch and a distance between the first radiation patch and the second radiation patch, when their pitch reaches a certain value, The impedance characteristics of the antenna are purely resistive, thereby broadening the bandwidth of the antenna.

Optionally, the first dielectric layer and the second dielectric layer may be made of a polytetrafluoroethylene (FR-4) epoxy resin dielectric plate.

The UHF near field RFID antenna of the embodiment of the invention combines circular polarization and wide frequency band, completely covers the UHF near field, and the axis ratio is easy to control, and the antenna structure is simple, and has low profile, light weight and volume. Small and other characteristics.

An embodiment of the present invention further provides an ultra high frequency near field RFID reader, comprising the UHF near field RFID antenna of any of the above.

An embodiment of the present application is described below with reference to the accompanying drawings. As shown in FIG. 1 and FIG. 2, an ultra-high frequency near field RFID antenna according to an embodiment of the present invention includes a first dielectric layer 6A and a second dielectric layer 6B. One side of the first dielectric layer 6A is provided with a feeding port 4 and two "E" type

microstrip power splitters

1A and 1B, and two shorting columns are respectively arranged at the ends of the output arms of the

microstrip power splitters

1A and 1B. 3A, 3B, 3C and 3D; a copper-clad layer 5 is disposed between the first dielectric layer 6A and the second dielectric layer 6B, and four through-holes for straight-through short-circuiting columns are provided on the floor copper-clad layer 5 to avoid short circuit The column is directly grounded; the other side of the second dielectric layer 6B is provided with two "L" shaped first radiating patches L1, L2 and a second radiating patch 2 of the annular structure. The structures of the first and second dielectric layers can be referred to FIG. 3 and FIG. 5, respectively. Refer to Figure 4 for the structure of the floor copper layer.

Wherein, the feeding port 4 can be fed with an impedance of 100 ohms, and each output arm of the

microstrip power splitters

1A and 1B can be a micro-belt transmission line of 50 ohms, the surface of the output arm is coated with copper foil, and each The length of the output arm is adjusted by adjusting the copper foil on the surface of the output arm. When the length difference between the two output arms of each microstrip power splitter is a quarter wavelength, the electromagnetic waves reaching the short-circuited

columns

3A, 3C produce a 90-degree phase shift, and the electromagnetic waves reaching the short-circuited

columns

3B, 3D also produce 90 degrees. The phase shifts to generate a circularly polarized wave; in addition, the two branches of the first radiation patch L1, L2 are vertically distributed, and a 90 degree phase shift is generated again, and the circularly polarized wave is excited again, the first radiation patch L1. The surface of the two branches of L2 is coated with copper foil, which is adjusted by adjusting the copper foil on the surface of the two branches to adjust the axial ratio of the circularly polarized wave, thereby achieving a 3 dB axial ratio; the first radiating patch couples the electromagnetic wave to the second Radiation is applied to the radiation patch 2. The length of the microstrip power splitter, the first radiating patch, and the second radiating patch is equal to a quarter of a working wavelength corresponding to the operating frequency of the UHF near field RFID antenna, and when the operating frequency of the antenna is determined After that, the lengths of the microstrip power splitter, the first radiating patch and the second radiating patch of the antenna can be calculated according to the working wavelength of the antenna, and the optimal result is obtained through optimized debugging. The surface of the second radiation patch is coated with a copper foil. When the second radiation patch is fixed, the impedance characteristic of the antenna can be adjusted by increasing or decreasing the copper foil on the surface of the second radiation patch, thereby adjusting the first radiation patch and the second radiation patch. The spacing between the two is adjusted. The smaller the pitch is, the stronger the capacitance characteristic is. When the coupling capacitance obtained by adjusting the spacing is equivalent to the inductance generated by the second radiation patch and the first radiation patch, the impedance characteristic of the antenna is a pure resistance. , thus widening the bandwidth of the antenna. When the impedance of the antenna is constant, the imaginary part of the antenna changes with the length and width of the first radiating patch. The longer the first radiating patch is, the wider the imaginary part of the antenna is.

The structure of the antenna is simulated by the existing microwave simulation software, and the values of the dimensions of each part of the antenna are calculated, and processed according to the calculated values. After the processing is completed, the two output arms of the microstrip power splitter are respectively adjusted. The length of the two branches of the first radiation patch and the length of the copper foil on the surface of the second radiation patch and the spacing between the first radiation patch and the second radiation patch.

Referring to FIG. 1 and FIG. 2, according to an ultra-high frequency near field RFID antenna disclosed in the embodiment of the present invention, the material of the first dielectric layer 6A and the second dielectric layer 6B substrate may be FR-4 epoxy resin, dielectric constant. 4.4, the thickness of each dielectric layer substrate is 1.2mm, the overall size of the antenna is 15mm*10mm, the length of the "E" type microstrip power divider is 12mm, and the length of the "L" type first radiation patch is 5mm. The second radiation patch has a length of 22 mm and a width of 2.2 mm. The feeding port of the antenna is a 100 ohm resistor, and the feeding line width is 0.5 mm. The antenna of the embodiment has a small size, and the antenna is miniaturized without reducing the performance of the antenna. By adjusting the spacing between the second radiating patch and the first radiating patch to be 0.2 mm, the impedance characteristic of the antenna is purely resistive, thereby widening the bandwidth of the antenna, and the working frequency band of the antenna can be from 860 MHz to 960 MHz, and the impedance bandwidth is 100MHz, completely covering the international ultra-high frequency band (866 ~ 956MHz); respectively adjusting the two arm lengths of the first radiation patch L1 and L2, when the two arms are 2.5mm long, the antenna is a circularly polarized antenna, The axial ratio is 3 dB.

The UHF near field RFID antenna of the embodiment of the present invention can be used in the fields of retail industry, pharmaceutical industry, library rack management, file cabinet management, shelf management, and valuables tracking.

For example, when applied to the management of the library shelf, the UHF near-field RFID antenna is combined with the RF interface module and the logic control module to form a reader/writer, and the library's collection of documents is tagged for tracking documents. Status and positioning information, etc., so that no manual operation is required, and information can be automatically sent to the reader/writer under the sensing of the reader to read the information stored in the tag.

The UHF near field RFID antenna of the embodiment of the invention can identify objects moving at high speed and can simultaneously identify multiple RFID tags, and the reading distance is longer, the security is higher, and the anti-interference ability is stronger.

The UHF near field RFID antenna adopting the embodiment of the invention has the following remarkable features:

1) The RFID antenna has a long reading distance and a large coverage range when used;

2) The antenna completely covers the UHF near field;

3) The antenna has a wide bandwidth and is less subject to interference;

4) The antenna is more uniform than the magnetic field of the conventional near-field antenna, and the reading effect is better;

5) The antenna has a flat structure, a small volume, a controllable axial ratio of the antenna, low cost, and simple installation.

One of ordinary skill in the art will appreciate that all or part of the steps in the above methods can be accomplished by software optimization. Optionally, all or part of the steps of the foregoing embodiments may also be implemented by using one or more integrated circuits. Accordingly, each module/unit in the foregoing embodiment may be implemented in the form of hardware. The invention is not limited to any specific form of combination of hardware and software.

The above description is only the preferred 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.

Industrial applicability

The embodiment of the invention extends the aperture of the antenna, effectively reduces the size of the antenna; widens the working bandwidth of the antenna, and the circular polarization axis ratio is better.

Claims

An ultra-high frequency near field RFID antenna comprising a first dielectric layer (6A), a second dielectric layer (6B) and a plurality of shorting columns (3A, 3B, 3C, 3D), the first dielectric layer (6A) And a floor copper layer (5) is disposed between the second dielectric layer (6B), wherein

Two microstrip power splitters (1A, 1B) are disposed on the first dielectric layer (6A), and each microstrip splitter (1A, 1B) includes two output arms and between the two output arms Orthogonal feeding, each output arm being connected to one end of a shorting column;

The floor copper layer (5) is provided with a through hole for passing through the shorting column (3A, 3B, 3C, 3D);

The second dielectric layer (6B) is provided with two first radiation patches (L1, L2) and at least one second radiation patch (2) coupled to the first radiation patches (L1, L2). The other ends of the shorting columns (3A, 3B, 3C, 3D) are connected to the first radiation patches (L1, L2).
The antenna of claim 1 wherein said first radiating patch (L1, L2) is an "L" shaped structure comprising two branches, said two branches being adjustable in length and perpendicular to each other.
The antenna according to claim 2, wherein the length of the two branches is adjusted by adjusting the length of the copper foil of the surface of the two branches.
The antenna according to claim 1, wherein the two output arms of the microstrip splitter (1A, 1B) are symmetrical curved structures.
The antenna according to claim 1, wherein said microstrip power divider (1A, 1B) is of an "E" type or "W" type structure.
The antenna according to claim 1, wherein a length difference between said two output arms is adjusted to be 1/4 of an operating wavelength of the antenna by adjusting a length of a copper foil of said two output arm surfaces.
The antenna of claim 1 wherein said second radiating patch (2) is a ring structure.
The antenna according to claim 1, wherein the width of the copper foil of the surface of the second radiation patch (2) and the first radiation patch (L1, L2) and the second radiation patch (2) are adjusted The spacing between the antennas is adjusted to exhibit pure impedance.
The antenna according to claim 1, wherein the first dielectric layer (6A) and the second dielectric layer (6B) are polytetrafluoroethylene epoxy dielectric sheets.
An ultra-high frequency near field RFID reader comprising the ultra high frequency near field RFID antenna of any one of claims 1 to 9.