CN107273967B

CN107273967B - Coreless label and coreless identification system

Info

Publication number: CN107273967B
Application number: CN201710511151.7A
Authority: CN
Inventors: 胡三明; 董国庆; 沈一竹; 孟洪福; 窦文斌
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2017-06-28
Filing date: 2017-06-28
Publication date: 2023-06-09
Anticipated expiration: 2037-06-28
Also published as: CN107273967A

Abstract

The invention relates to a dual circular polarization coreless identification system. The system comprises three innovation points: (1) The card reader adopts a double circularly polarized receiving and transmitting antenna to identify randomly placed tags in a non-line-of-sight range and improve receiving and transmitting isolation; (2) The label does not contain a chip and only consists of a plurality of circles of conductive structures, the label can be directly printed on the surfaces of objects such as paper, cloth, plastics and the like by adopting conductive ink containing graphene, and the coreless label can be made of materials sensitive to the ambient temperature, the humidity and the like so as to be used for monitoring the ambient temperature and the humidity change; such coreless labels may also be placed inside the object to be inspected for security applications; (3) By adding the dummy structure, the information capacity of the coreless tag is improved.

Description

Coreless label and coreless identification system

Technical Field

The invention relates to the field of radio frequency identification, in particular to a coreless label and a double circular polarization coreless identification system.

Background

Radio Frequency Identification (RFID) is a contactless automatic identification communication technology that identifies a target object by a wireless signal and acquires related data. The theory basis of RFID is laid in Harry Stockman in 1948. In the second war, the aircraft is tagged to distinguish between me, and this identity of me is recognized as the precursor of the RFID system. The first commercialized RFID system for electronic toll collection in the world was presented in norway 1987. To date, RFID technology has been widely used in the fields of warehouse logistics, manufacturing, medical treatment, transportation, retail, identification, etc., and is becoming a cornerstone of the internet of things.

Each commercial tag in conventional rfid systems has a chip and is therefore costly. On the other hand, bar codes are low in cost, but only work in a short viewing distance range, are required to be placed regularly, and are not easy to realize full-automatic identification. In order to apply the radio frequency identification technology to more occasions, coreless identification technology has been developed. In coreless identification systems, each tag contains neither a chip nor a battery. The tag is composed of a conductive passive structure, so that the tag is low in cost, long in service life and simple to process. Coreless labels are expected to achieve low cost similar to bar codes and have functions not possessed by bar codes, such as simultaneously identifying multiple objects in a non-line-of-sight range, achieving full-automatic identification, hiding in objects to achieve privacy, and the like.

The coreless identification system currently in the research stage is still immature, and has the following problems: (1) Only a small part of coreless labels placed randomly can be identified, and full-automatic identification is not easy to realize; (2) the information capacity of the existing label is low; (3) Most of the existing labels cannot be directly printed on paper, cloth, plastics and other materials.

Disclosure of Invention

In order to solve the problems, the invention improves the structure of the coreless label and the identification system thereof, and provides a coreless label and a double circular polarization coreless identification system.

In one aspect of the present invention, a coreless tag is provided, which is composed of a plurality of turns of conductive structures, wherein a turn of conductive structure is added to the inner side of the innermost turn of conductive structure, and the added conductive structure has a resonance point only outside the working frequency band. The conductive structure is formed by printing conductive ink or processing by adopting other material processes.

In one aspect of the present invention, a coreless tag reader is provided, the reader is a radiation and reception unit of electromagnetic wave signals, and includes a transmitting and receiving circuit, and further includes a pair of transceiver antennas, which are respectively a left-hand circularly polarized antenna and a right-hand circularly polarized antenna of orthogonal polarization.

In another aspect of the present invention, a coreless identification system is provided, including a card reader and one or more coreless tags, where the card reader is a radiation and receiving unit of electromagnetic wave signals, and includes a transmitting and receiving circuit, and further includes a pair of transceiver antennas, which are respectively a left-hand circularly polarized antenna and a right-hand circularly polarized antenna that are orthogonally polarized.

The system can achieve the following beneficial effects: (1) identifying any placed coreless tags; (2) increasing the information capacity of the coreless tag; (3) increasing the receiving and transmitting isolation of the card reader; (4) implementing a printable coreless label; (5) ambient temperature, humidity, etc. may be monitored.

Drawings

FIG. 1 is a schematic diagram of a dual circularly polarized coreless identification system

FIG. 2 is a dual circularly polarized array antenna implemented with shared interleaved radiating elements

Fig. 3 is a dual circularly polarized transceiver antenna based on a high impedance surface structure

Fig. 4 shows the isolation of the two circularly polarized array antennas shown in fig. 2 and 3

FIG. 5 is a coreless label

FIG. 6 is a radar scattering interface before and after coreless tag introduction of a dummy

FIG. 7 is a coreless label consisting of multiple arrays

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.

FIG. 1 is a schematic diagram of a dual circularly polarized coreless identification system in accordance with the present invention. The system includes a pair of circularly polarized antennas configured in orthogonal polarizations, and one or more coreless tags. The pair of dual circularly polarized antennas comprises a transmitting antenna and a receiving antenna, the transmitting antenna and the receiving antenna adopt orthogonal circular polarization modes, and the equipotential surfaces of the transmitting antenna and the receiving antenna are parallel to the coreless tag, so that the left-hand circularly polarized wave of the transmitting antenna detects the resonance frequency point of the coreless tag, and the coreless tag can rotate randomly in the current plane. Resonance rings with different lengths on the coreless tag can generate resonance with different frequencies after being excited by plane waves of the transmitting antenna, and the corresponding frequency points correspond to binary '1' and '0' when resonance exists or not, so that information can be modulated. Since even harmonics of the resonant ring are not present, odd harmonics are small and the frequency point is out of band. Therefore, the reflected dextrorotation plane wave enters the receiving antenna on the same side as the transmitting antenna, and information carried by the tag can be detected according to the resonance pattern. Since the antenna is a circularly polarized antenna, the randomly placed tags within a non-line-of-sight range can be identified. In addition, the electromagnetic wave of the receiving and transmitting antenna adopts an orthogonal polarization mode, so that the isolation degree of the receiving and transmitting antenna can be improved.

To increase the sensitivity of the coreless identification system, a dual circularly polarized array antenna may be employed. In one embodiment, the present invention proposes a shared interleaved radiating element to implement a dual circularly polarized array antenna. As shown in fig. 2, the array antenna includes a plurality of left-hand circularly polarized antennas 21, a plurality of microstrip patches 22, and a plurality of right-hand circularly polarized antennas 23. Each left/right circular polarized antenna is a 2x2 sub-array, the left and right circular polarized antennas are arranged in an interweaving way, and adjacent left/right circular polarized antennas share adjacent microstrip patches. Each 2x2 subarray consists of antennas positioned at the periphery and a feed structure positioned at the center, and the feed structures between adjacent left-hand circularly polarized antennas or adjacent right-hand circularly polarized antennas are different by 90 degrees.

The advantage of this structure is that: (1) The left circular polarization subarrays and the right circular polarization subarrays of 2x2 are arranged in an interweaving way and share adjacent microstrip patches, so that the unit spacing between the subarrays is reduced, and grating lobes are avoided; (2) The left-handed antenna array and the right-handed antenna array share the microstrip patch, and the number of microstrip radiating units can be reduced from the traditional 4N to 2N+2 (N is the number of 2x2 subarrays), so that the whole structure is more compact; (3) The feed structure adopts a continuous rotating structure to realize broadband impedance matching and axial ratio bandwidth; (4) The whole structure can be realized by adopting two layers of dielectric plates, and is easy to integrate.

In the structure shown in fig. 2, all radiation units are connected in series, and the left and right circular polarization feeding parts are staggered, so that the isolation between the two circular polarizations is low. In order to solve the isolation problem, the invention further provides the dual circularly polarized antenna array based on the high-resistance surface structure shown in fig. 3. In this embodiment, the left-hand circularly polarized antenna array 31 is separated from the right-hand circularly polarized antenna array 33 while the high impedance surface structure 32 is added in the middle to further increase the isolation. The high impedance surface, also known as an Electromagnetic Band Gap (EBG) structure or left-hand material, consists of a periodic mushroom structure. At the resonance point the surface impedance of the high impedance structure will become infinitely large and the tangential magnetic field will be very small, so that it approximates an ideal magnetic conductor, at which point a phase of 0 deg. is created, i.e. in-phase reflection of the incident wave. The high impedance surface also has the ability to suppress surface wave propagation, so it reduces mutual coupling between the left and right hand circularly polarized arrays. The comparison of fig. 4 shows that the isolation of the dual circularly polarized antenna can be increased from 10dB for the structure of fig. 2 to 50dB for the structure of fig. 3.

Typically, coreless tags are comprised of a set of square conductor loops, the outermost square loop producing a resonant frequency under the irradiation of an incident electromagnetic wave, the frequency being at the lowest end of the operating frequency band. Correspondingly, other adjacent square rings sequentially correspond to higher resonance frequency points, wherein the eighth ring corresponds to the highest frequency point in the working frequency band. Thus, a square ring of a typical coreless tag may carry 8 bits of information, and increasing the number of rings of the square ring may correspondingly increase the number of bits of information. As shown in fig. 5, the present invention proposes to add a dummy, i.e. a ninth square ring, on the innermost side of the square ring. The dummy has a resonance point only outside the operating frequency band and thus does not carry useful information, only playing a coupling role. The results shown in fig. 6 demonstrate that the dummy limits the resonance frequency point of the resonance loop to be within the operating band.

Of course, the square ring can also have different structures such as triangle, circle, ellipse, etc. and combinations thereof. The material of the conductive structure of the tag may be conductive ink including graphene. The substrate of the tag is a dielectric material including paper, cloth, plastic, and the like. The coreless label can be made of materials sensitive to ambient temperature, humidity and the like, and is used for monitoring ambient temperature and humidity changes; the coreless tag may also be placed inside the object to be inspected for security applications.

The coreless labels of the present invention may also be combined in an array, as shown in fig. 7. When it is desired to increase the readable distance of the coreless labels, a plurality of coreless labels containing the same information may be arranged in an array. When it is desired to provide the information capacity of the coreless tag, a plurality of coreless tags containing different information may be arranged in an array. Of course, the coreless tag array can be divided into a plurality of groups, each group of coreless tags contains the same information, and the coreless tags in different groups have different information, so that the readable distance and the information capacity can be considered.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims

1. A coreless tag is composed of a group of conductive structures with a plurality of circles, and is characterized in that a circle of conductive structure is additionally arranged on the inner side of the conductive structure with the innermost circle, and the added conductive structure only has resonance points outside an operating frequency band, does not carry useful information and only has a coupling effect.

2. The coreless tag of claim 1, wherein the conductive structure is a conductive ink, and the substrate of the coreless tag is a material sensitive to ambient temperature and humidity for monitoring changes in ambient temperature and humidity; the coreless tag is placed inside the object to be inspected for security applications.

3. A coreless tag array comprising a plurality of coreless tags as claimed in claim 1 or claim 2, the plurality of coreless tags forming an array.

4. A coreless tag array as claimed in claim 3, wherein at least two coreless tags contain the same information.

5. A coreless tag array as claimed in claim 3, wherein at least two coreless tags contain different information.

6. A dual-rounded coreless tag identification system, comprising a transmitting circuit and a receiving circuit, one or more coreless tags as claimed in claim 1 or 2, and more than one pair of transceiver antennas, i.e. a left-hand circularly polarized antenna and a right-hand circularly polarized antenna, respectively, of orthogonal polarization.

7. The dual-circular coreless tag identification system of claim 6, comprising a plurality of left-hand circularly polarized antennas (21), a plurality of microstrip patches (22), and a plurality of right-hand circularly polarized antennas (23), wherein each of the left-hand circularly polarized antennas or right-hand circularly polarized antennas is a 2x2 sub-array, the left-hand circularly polarized antennas are interleaved with the right-hand circularly polarized antennas, and adjacent ones of the left-hand circularly polarized antennas and right-hand circularly polarized antennas share adjacent microstrip patches.

8. The dual-circular coreless tag identification system of claim 6, comprising a left-hand circularly polarized antenna array (31) comprised of a plurality of 2x2 left-hand circularly polarized antenna subarrays, a right-hand circularly polarized antenna array (33) comprised of a plurality of 2x2 right-hand circularly polarized antenna subarrays, the left-hand circularly polarized antenna array and the right-hand circularly polarized antenna array being disposed on both sides with a high impedance surface structure (32) disposed therebetween.

9. The dual-rounded coreless tag identification system of claim 8, wherein the high impedance surface structure is an Electromagnetic Band Gap (EBG) structure or a left-handed material.