CN213366793U

CN213366793U - Near-mid field radio frequency identification reader antenna

Info

Publication number: CN213366793U
Application number: CN202022874014.XU
Authority: CN
Inventors: 刘学观; 方艳茹
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-06-04
Anticipated expiration: 2030-12-03

Abstract

The utility model relates to a near-midfield radio frequency identification reader antenna. The near-mid field radio frequency identification reader antenna comprises: medium base plate, antenna radiation unit, aluminum plate and feed unit, the antenna radiation unit lay in the upper surface of medium base plate, the feed unit lay in the lower surface of medium base plate, just the feed unit comprises the microstrip line of taking the bending, aluminum plate is located under the medium base plate, the antenna radiation unit includes three radiation portion, and first radiation portion is located the centre, and second radiation portion is located with the form of symmetry with the third radiation portion the both sides of first radiation portion and respectively with first radiation portion connects. The reader antenna can realize the detection of the linear polarization tags in any peripheral angle direction, has lower far field gain, and can avoid the misreading of the tags outside a limited area.

Description

Near-mid field radio frequency identification reader antenna

Technical Field

The utility model relates to a read ware antenna technology, especially, relate to an ultra high frequency (UHF, ultra high frequency) radio frequency identification (RFID, radio frequency identification) reader antenna suitable for near midfield.

Background

The RFID (Radio Frequency Identification) technology is a non-contact automatic Identification technology. Reader antennas play a key role in RFID systems. The operating frequency of the reader antenna may be low frequency (below 135 kHz), high frequency (13.56MHz), ultra high frequency (860 and 960MHz), microwave frequency (above 2.4 GHz), etc. After the electronic tag enters the antenna magnetic field, if a special radio frequency signal sent by the reader-writer is received, product information (a passive tag) stored in a chip can be sent out by means of energy obtained by induced current, or a signal with a certain frequency (an active tag) is actively sent out, and the reader-writer reads and decodes the information and sends the information to a central information system for related data processing. The reader antenna is divided according to the action distance and can be divided into a near-field antenna and a far-field antenna. The near-field antenna has a strong electromagnetic field only at a short distance, the strength of the electromagnetic field is sharply weakened along with the elongation of the distance, the far-field gain of the antenna is very low, and therefore large-area metal around the antenna does not affect the performance of the antenna.

With the successful application of the RFID technology to intelligent logistics, the logistics cold chain management realizes automation and intellectualization, and the accuracy and the efficiency of the whole supply chain are greatly improved. By additionally arranging the RFID reader and the reader antenna in the main channel and the auxiliary channel of the article cabinet, when an article attached with a passive tag is placed in the article cabinet (namely, enters an interrogation magnetic field area of the reader antenna), the tag antenna obtains enough driving energy to send tag information of the tag, the reader antenna receives a carrier signal sent from the tag and then transmits the carrier signal to the reader, an RF modulator carried in the reader demodulates and decodes the received signal, and then the information is transmitted to a computer system to be processed, so that the application of information inquiry, statistics, management and the like related to the article is completed.

In recent years, many articles about near field RFID reader antennas have been published at home and abroad. The documents t.lin, y.lin, h.chen and j.c.hsu, "Compact UHF near-field RFID reader antenna,"2014International Symposium on Antennas and Propagation requirements, Kaohsiung,2014, pp.629-630 propose a bandwidth enhanced Compact dual open-loop antenna for the UHF near-field, which is capable of generating a strong and uniform magnetic field in a small open-loop near-field region. Two open loops of different half-wavelength perimeters were etched on both sides of the FR4 printed circuit board to widen the bandwidth. The antenna has good impedance matching and uniform magnetic field distribution on 888-932MHz bandwidth, and the reading distance measured by the antenna can reach 130 mm. The document [ B.Shrestha, A.Elsherbeni and L.Ukkonen, "UHF RFID Reader Antenna for Near-Field and Far-Field Operations," in IEEE Antennas and Wireless processing Letters, vol.10, pp.1274-1277,2011] describes an RFID Reader Antenna suitable for Near Field and Far Field operation in the Ultra High Frequency (UHF) band. And performing near field operation by adopting a segmented ring technology, and performing far field operation by adopting a patch antenna. The working range of the antenna is 864-873 MHz, the reflection coefficient is less than-10 dB, and the UHF RFID frequency band is covered. Its linearly polarized radiation mode provides a 4-dBi gain. The antenna has a read capability up to 9 cm and 6m for near field and far field applications. The document [ J.Kizhekkekkathllam and M.Kanagasabai, "A Novel UHF Near-Field RFID Reader Antenna deployment CSRR Elements," in IEEE Transactions on Antennas and deployment, vol.65, No.4, pp.2047-2050, April 2017] proposes a ultrahigh frequency Near Field RFID Reader Antenna based on CSRR Elements. The antenna consists of a power divider and two arms. The two arms end with two 50 Ω terminals. The first arm is the front arm and is a microstrip transmission line. The second arm is the rear arm, which carries the CSRR element, facilitating backward wave propagation. The reverse current generated by the structure generates a strong and uniform magnetic field on the plane of the antenna for ultrahigh frequency near field RFID operation, and the near field read distance of the antenna is 100 mm. The document [ C.Cho, C.Lee, J.Ryoo and H.Choo, "Planar Near-Field RFID Reader Antenna for Item-Level Tagging," in IEEE Antennas and Wireless Propagation readers, vol.10, pp.1100-1103,2011] shows a novel UHF Planar Near-Field Antenna for the application of RFID Item-Level tags. The proposed antenna is designed to have a strong and uniform field over a wide aperture antenna to identify various tags having stable reading performance. In order to obtain a strong near field, two coupling blocks and one microstrip line feed are used. The document [ X.Wei, B.Hu and H.Zhang, "Novel UHF Near-Field RFID Reader Antenna Based on Double-Sided Parallel-Strip Line," in IEEE Antennas and Wireless amplification readers, vol.13, pp.419-422,2014] proposes a Reader Antenna Based on Double-Sided Parallel Strip lines (DSPSL) for an ultrahigh frequency Near Field RFID system. The antenna consists of an inverter, a DSPSL structure and four dipoles. The antenna works at 887 MHz-938 MHz, and the reflection coefficient is less than-10 dB. The maximum read distances were 200mm and 70mm, respectively, when the input power was 30dBm and 17 dBm. The document [ Y.Yao, Y.Liang, J.Yu and X.Chen "," Design of a Multipolarized RFID Reader Antenna for UHF Near-Field Applications "," in IEEE Transactions on Antennas and Propagation, vol.65, No.7, pp.3344-3351, July 2017] studies a novel UHF Radio Frequency Identification (RFID) multi-polar read Antenna based on a pair of symmetrically curved open microstrip lines for Near Field Applications. Near field and multi-polarization operation is achieved by introducing a 90 ° phase shift between the currents flowing along opposite sides of the two branches. The antenna can generate a uniform strong electric field in a near field area, and the reading range is as follows: 450mm x450mm x350mm (width x length x height). The analog and measured impedance bandwidths (-10dB) are very compatible, ranging from 825 to 965 MHz. In addition, the far field gain is low, and the situation that the label outside a near field area is misread is avoided.

However, the above techniques do not show how to ensure the accuracy of detecting the linearly polarized tags at any peripheral angle direction, and at the same time, the antenna structure is too complex, and the installation is not very convenient.

Therefore, improvements to existing antenna structures are needed.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present application provides a near-mid field RFID reader antenna capable of operating in a near-mid field ultra high frequency RFID reader antenna. The reader antenna can realize the detection of the linear polarization tags in any peripheral angle direction, and has lower far field gain, so that the tag misreading outside a limited area can be avoided. In addition, the reader antenna has the advantages of simple structure, low profile abrasion and convenience in installation. Meanwhile, the reader antenna is applicable to application scenes of the intelligent article cabinet, and is used for reading tag information carried on articles placed in the article cabinet and uploading the tag information to a background server.

In order to achieve the purpose, the following technical scheme is adopted in the application:

an embodiment of the present application provides a near-field radio frequency identification reader antenna, including: the antenna comprises a dielectric substrate, an antenna radiation unit, an aluminum plate and a feed unit, wherein the dielectric substrate is made of an FR4 plate with high dielectric constant, the relative dielectric constant of the FR4 plate is 4.4, the loss tangent of the FR4 plate is 0.02, and the thickness h of the FR4 plate is 0.8 mm. The antenna radiation unit is laid on the upper surface of the dielectric substrate, the feed unit is laid on the lower surface of the dielectric substrate and composed of a microstrip line with a bend, and the aluminum plate is located under the dielectric substrate. The antenna radiation unit comprises three radiation parts, wherein a first radiation part is positioned in the middle, and a second radiation part and a third radiation part are positioned on two sides of the first radiation part in a symmetrical mode and are respectively connected with the first radiation part.

An embodiment of the present application provides a near-mid field rfid reader antenna, which is characterized in that,

the method comprises the following steps: a dielectric substrate, an antenna radiation unit, an aluminum plate and a feed unit,

the antenna radiation unit is laid on the upper surface of the dielectric substrate, the feed unit is laid on the lower surface of the dielectric substrate and consists of a micro-strip line with a bend, the aluminum plate is positioned under the dielectric substrate,

the antenna radiation unit comprises three radiation parts, wherein a first radiation part is positioned in the middle, and a second radiation part and a third radiation part are positioned on two sides of the first radiation part in a symmetrical mode and are respectively connected with the first radiation part. The reader antenna can realize the detection of the linear polarization tags in any peripheral angle direction, has lower far field gain, and can avoid the misreading of the tags outside a limited area.

In one embodiment, the microstrip line forming the power feeding unit is laid on the lower surface of the dielectric substrate in a shape in which a head portion is a sector with a radius R and a body portion is a combination of two rectangles having different lengths and widths.

In one embodiment, the angle of the fan is 140 degrees and the radius is 27 mm.

In one embodiment, the shape of the torso portion includes:

a first rectangle having a length of 10.5mm and a width of 3.5mm,

the second rectangle, its length is 11.5mm, wide 1.53mm, just the long limit direction's of first rectangle one end with the sectorial straight fringe line of head links to each other, the other end with the long limit direction's of second rectangle one end links to each other to and the coincidence of the long limit direction's of first rectangle and second rectangle central line.

In one embodiment, the aluminum plate is connected to the dielectric substrate by a plurality of copper pillars at an edge portion and an odd number of plastic pillars at a middle portion.

In one embodiment, the number of the plastic posts is 5.

In one embodiment, the copper and plastic pillars are configured as cylinders having a diameter of 3mm and a height of 12 mm.

In one embodiment, the first radiating portion, the second radiating portion and the third radiating portion are integrally formed and have a width of 21 mm.

In one embodiment, the outermost edge of the first radiating portion is a straight line parallel to the first long edge line of the dielectric substrate, and the distance between the straight line and the first long edge line of the dielectric substrate is 19.5 mm.

In one embodiment, the dielectric substrate has a groove formed on an upper surface thereof, and the shape of the groove matches with a shape formed by a combination of the first radiation portion, the second radiation portion, the third radiation portion, and the connection portion thereof.

Advantageous effects

By adopting the near-mid field radio frequency identification reader antenna, the resonance points can be increased on the radiation unit on the upper surface of the dielectric substrate of the antenna, and the width of the gap is adjusted to enable the resonance points to approach, so that the bandwidth is expanded; the transmission line with the top-loaded fan-shaped structure is arranged on the lower surface of the dielectric substrate, so that the bandwidth is expanded; the microstrip line realizes 50 ohm impedance matching by adjusting the microstrip line width of the antenna in a lumped port excitation mode. The linearly polarized slot antenna has the characteristics of low section, far field, low gain, wide bandwidth and the like.

Drawings

FIG. 1 is an overall state diagram of an RFID reader antenna according to an embodiment of the present application;

FIG. 2 is a front view of an RFID reader antenna according to an embodiment of the present application;

FIG. 3 is a bottom surface view of a dielectric substrate of an RFID reader antenna according to an embodiment of the present disclosure;

FIG. 4 is a side view of an RFID reader antenna according to an embodiment of the present application;

FIG. 5 is a return loss simulation diagram of an RFID reader antenna according to an embodiment of the present application;

FIG. 6 is a far field simulated pattern of an RFID reader antenna according to an embodiment of the present application;

fig. 7 is a diagram of a measured state of an rfid reader antenna according to an embodiment of the present application.

Detailed Description

The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present invention. The conditions employed in the examples may be further adjusted as determined by the particular manufacturer, and the conditions not specified are typically those used in routine experimentation.

In the present application, the terms "upper", "lower", "inside", "middle", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.

The application provides a near-midfield radio frequency identification reader antenna (antenna for short below), it includes: the antenna radiation unit is laid on the upper surface of the dielectric substrate, the feed unit is laid on the lower surface of the dielectric substrate and consists of a microstrip line with a bend, the aluminum plate is positioned right below the dielectric substrate, the antenna radiation unit comprises three radiation parts, the first radiation part is positioned in the middle, and the second radiation part and the third radiation part are positioned on two sides of the first radiation part in a symmetrical mode and are respectively connected with the first radiation part. The reader antenna can realize the detection of the linear polarization tags in any peripheral angle direction, has lower far field gain, and can avoid the misreading of the tags outside a limited area. The reader antenna with the structure has unique structural design, and the effective path of current is prolonged by slotting on the rectangular patch, so that the increase of resonance points is realized, and the bandwidth can be expanded. In addition, the reader antenna adopts a microstrip transmission line with a top loading sector structure as a feed end of the antenna, the microstrip transmission line is used for expanding the bandwidth, the input impedance of the antenna working at 915MHz is 50 omega, and in the actual design, the sector feed part is arranged in the approximate middle area of the dielectric substrate, so that the return loss is reduced, and the processing technologies such as welding and the like can be simplified.

The antenna proposed by the present application is described in detail below with reference to the accompanying drawings.

As shown in fig. 1 and 4, the near-mid field rfid reader antenna 10 includes: the antenna comprises a dielectric substrate 1, an antenna radiation unit 2, an aluminum plate 3 and a feed unit 4, wherein the dielectric substrate adopts an FR4 plate material with high dielectric constant, the relative dielectric constant is 4.4, the loss tangent is 0.02 and the thickness is 0.8 mm. The antenna radiation unit 2 is laid on the upper surface of the dielectric substrate 1, the feed unit 4 is laid on the lower surface of the dielectric substrate 1, the feed unit 4 is composed of a microstrip line with a bend, and the aluminum plate 3 is positioned under the dielectric substrate 1. The antenna radiation unit 2 comprises three radiation parts (21, 22, 23), wherein the first radiation part 21 is positioned in the middle, and the second radiation part 22 and the third radiation part 23 are positioned at two sides of the first radiation part 21 in a symmetrical mode and are respectively connected with the first radiation part 21.

In a preferred embodiment, the microstrip line of the power feeding unit 4 is laid on the lower surface of the dielectric substrate in a special shape, the head part is a sector 41 with a radius R, and the body part is a combination of two rectangles with different lengths and widths.

In a preferred embodiment, the aluminum plate 3 is connected to the dielectric substrate 1 by 8 copper pillars 5 at the edge portion and 5 plastic pillars 6 at the middle portion, and the copper pillars 5 and the plastic pillars 6 are cylinders having a diameter of 3mm and a height of 12 mm. The preferred distance between the aluminum plate 3 and the dielectric substrate 1 is 12 mm.

In particular, the widths of the first, second and

third radiation portions

21, 22, 23 are all the same, and w1 is preferably 21 mm.

In a preferred embodiment, as shown in fig. 2, the outermost edge of the first radiation portion 21 is a straight line 211 parallel to the first long edge line 11 of the dielectric substrate, and the distance L6 between the straight line 211 and the first long edge line 11 of the dielectric substrate 1 is 19.5 mm. The innermost edge of the first radiating portion 21 is a straight line 212 parallel to said outermost edge with a length m 0-105 mm; the length of the straight line 211 is L5 ═ 215 mm. The outermost edge of the second/third radiating portion (22/23) is a straight line (221/231) parallel to the second long edge line 12 of the dielectric substrate with a length L4-185 mm, and the distance L1 of the straight line (221/231) from the second long edge line 12 of the dielectric substrate is 10.5 mm. The innermost edge of the second/third radiating portion is a straight line (222/232) parallel to the outermost edge, having a length L3-126 mm. In the present embodiment, the size of the dielectric substrate is L0-17 mm, L1-10.5 mm, L2-8 mm, L3-126 mm, L4-185 mm, L5-215 mm, L6-19.5 mm, L7-100 mm, a-450 mm, b-98 mm, w-215 mm₁＝21mm。m₀＝105mm。

In a preferred embodiment, the upper surface of the dielectric substrate is provided with a groove, and the shape of the groove is consistent with the shape of the antenna radiation unit, that is, the shape of the groove is the shape formed by combining the first radiation part 21, the second radiation part 22, the third radiation part 23 and the connection parts (24, 25) thereof.

In a preferred embodiment, as shown in fig. 3, the microstrip line is laid in a shape that the sector 41 of the head portion is: the angle is 140 degrees, and the radius is 27 mm; the trunk part has the shape: the first rectangle 42 has a length w5 of 10.5mm and a width w2 of 3.5mm, the second rectangle 43 has a length w6 of 11.5mm and a width h4 of 1.53mm, one end of the first rectangle 42 in the longitudinal direction is connected to a straight edge line (411, 412) of the head in a fan shape, the other end is connected to one end of the second rectangle 43 in the longitudinal direction, and the center lines of the first rectangle 42 and the second rectangle 43 in the longitudinal direction coincide with each other.

FIG. 5 is the simulation result of the S11 parameter of the antenna, and it can be seen that the designed antenna realizes | S11| < -10dB in the range of 902MHz-928 MHz.

Fig. 6 and 7 are gain diagrams of the antenna on the E-plane and the H-plane, and the gain of the antenna at 0 degree is about 2dB under the condition of 915MHz, which illustrates that the antenna designed by the implementation of the present application is suitable for near field applications.

The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above description, and although the present invention has been disclosed by the preferred embodiment, it is not limited to the present invention, and any person skilled in the art can make modifications or changes equivalent to the equivalent embodiments by utilizing the above disclosed technical contents without departing from the technical scope of the present invention, but all the modifications, changes and changes of the technical spirit of the present invention made to the above embodiments are also within the scope of the technical solution of the present invention.

Claims

1. A near-mid field radio frequency identification reader antenna, comprising: a dielectric substrate, an antenna radiation unit, an aluminum plate and a feed unit,

the antenna radiation unit comprises three radiation parts, wherein a first radiation part is positioned in the middle, and a second radiation part and a third radiation part are positioned on two sides of the first radiation part in a symmetrical mode and are respectively connected with the first radiation part.

2. The near-mid radio frequency identification reader antenna of claim 1, wherein: the microstrip line forming the power feeding unit is laid on the lower surface of the dielectric substrate, the head part of the microstrip line is in a sector shape with the radius of R, and the body part of the microstrip line is formed by combining two rectangles with different lengths and widths.

3. The near-mid radio frequency identification reader antenna of claim 2, wherein: the angle of the fan shape is 140 degrees, and the radius is 27 mm.

4. The near-mid radio frequency identification reader antenna of claim 2, wherein:

the shape of the trunk section includes:

a first rectangle having a length of 10.5mm and a width of 3.5mm,

5. The near-mid radio frequency identification reader antenna of claim 1, wherein: the aluminum plate is connected to the medium substrate through a plurality of copper columns at the edge part and an odd number of plastic columns at the middle part.

6. The near-mid radio frequency identification reader antenna of claim 5, wherein: the number of the plastic columns is 5.

7. The near-mid radio frequency identification reader antenna of claim 5, wherein: the copper column and the plastic column are both configured into cylinders, and the diameter of each cylinder is 3mm, and the height of each cylinder is 12 mm.

8. The near-mid radio frequency identification reader antenna of claim 1, wherein: the first radiation part, the second radiation part and the third radiation part are integrally formed and are 21mm in width.

9. The near-mid radio frequency identification reader antenna of claim 8, wherein: the outermost edge of the first radiation part is a straight line parallel to the first long edge line of the dielectric substrate, and the distance between the straight line and the first long edge line of the dielectric substrate is 19.5 mm.

10. The near-mid radio frequency identification reader antenna of claim 1, wherein: the upper surface of the dielectric substrate is provided with a groove, and the shape of the groove is matched with the shape formed by the combination of the first radiation part, the second radiation part, the third radiation part and the connecting part thereof.