CN111416194A

CN111416194A - Ultrahigh frequency anti-metal RFID (radio frequency identification) tag antenna

Info

Publication number: CN111416194A
Application number: CN201910014301.2A
Authority: CN
Inventors: 何赛灵; 李来军
Original assignee: Shaoxing Tuju Photoelectric Technology Co ltd
Current assignee: Shaoxing Tuju Photoelectric Technology Co ltd
Priority date: 2019-01-08
Filing date: 2019-01-08
Publication date: 2020-07-14

Abstract

The invention discloses an ultrahigh frequency anti-metal RFID tag antenna which comprises a medium substrate layer, a top radiation surface, an interdigital capacitor and a single-layer double-sided structure of a bottom radiation surface. Two sides of the medium substrate layer are respectively provided with a short-circuit through hole for short-circuit of the top radiation surface and the bottom radiation surface; the middle part of the surface where the top radiation surface and the interdigital capacitor are located is provided with a gap for welding a tag chip, and the two interdigital capacitors are connected between the gap and the top radiation surface in series, so that the width of the tag antenna is greatly reduced; the bottom radiating surface is a metal surface short-circuited with the top radiating surface. The ultrahigh frequency anti-metal radio frequency identification tag antenna has the advantages of simple structure, easy processing, convenient installation, high radiation efficiency and stable application.

Description

Ultrahigh frequency anti-metal RFID (radio frequency identification) tag antenna

Technical Field

The invention relates to the technical field of antennas, in particular to an ultrahigh frequency anti-metal RFID (radio frequency identification) tag antenna.

Background

Radio Frequency Identification (RFID) technology is a non-contact automatic Identification technology that has emerged in the 90 s of the 20 th century, and is another automatic Identification technology following barcode technology, optical character Identification technology, magnetic stripe technology, IC card Identification technology, voice Identification technology, and visual Identification technology. The technology is applied earlier abroad and starts later in China, but has already been applied to engineering relatively, is more and more extensive, is almost visible everywhere in life, and increasingly attracts people's attention. The RFID system refers to an electronic system designed and manufactured by applying the RFID technology and used in a specific situation, such as an electronic commerce anti-theft system, an entrance guard system, a traffic payment and a unit meal payment system.

A complete RFID system comprises a control terminal, a reader-writer and a label, wherein information is transmitted between the reader-writer and the label through an antenna, so that automatic identification is realized, and subsequent reading and writing operations are performed. The tag antenna is an important component of the rfid system. With the emergence of the internet of things, a great number of traditional industries are gradually moving to intelligent roads, wherein a lot of metal goods are not lacked, and the radio frequency identification of the metal goods has the difficulty in the design of tag antennas.

Most of the traditional tag antenna designs design the tag antenna in a mode of designing a folded dipole on a flexible substrate, but when the tag antenna is arranged on a metal surface, the tag antenna cannot normally work due to the reflection effect of the metal surface on electromagnetic waves and the electromagnetic induction between the metal and the tag.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a strip-shaped ultrahigh frequency metal-resistant RFID tag antenna which is simple in structure, easy to process and install, high in radiation efficiency and stable in application.

In order to realize the purpose, the invention adopts the following technical scheme:

an ultrahigh frequency anti-metal RFID tag antenna comprises a dielectric base layer, a top radiation layer and a bottom grounding layer; the top radiation layer is of a symmetrical structure; the top radiation layer and the bottom grounding layer are conductive metal layers; the top radiating layer, the bottom ground layer and the dielectric base layer have the same size; the top radiation layer is communicated with the bottom grounding layer through holes at two ends of the antenna; the top radiation layer is provided with a gap in the middle, and interdigital capacitor structures are respectively arranged on two sides of the gap.

Furthermore, the ultrahigh frequency anti-metal RFID tag antenna adopts a strip-shaped design, the sizes of the top radiation layer, the bottom grounding layer and the medium substrate are the same, the length of the top radiation layer, the bottom grounding layer and the medium substrate is about one half of the wavelength of a medium in a working frequency band, and the relatively high radiation efficiency is realized.

The medium wavelength can be calculated by the following formula:

wherein λ is the medium wavelength, λ₀Which is the wavelength in the vacuum, is,_ris the relative dielectric constant of the dielectric substrate.

Further, the distance between the two through holes is about one half of the wavelength of the dielectric waveguide.

Furthermore, the ultrahigh frequency anti-metal RFID tag antenna is made of Fr-4 with copper-clad double surfaces, the Fr-4 is a dielectric base layer, one copper-clad surface is used as a top radiation layer, and the other copper-clad surface is used as a bottom grounding layer.

Furthermore, a gap is arranged in the middle of the copper-clad surface serving as the top radiation layer, and two bent gaps are arranged on two sides of the gap respectively to form two interdigital capacitor structures which play a role in series connection of capacitors, so that the capacitance can be increased, and the width of the antenna can be reduced.

Furthermore, the middle gap is used for welding a chip and feeding power, the width of the middle gap is determined according to the width of a pin of the used label chip, for example, the width of a SOT packaging pin of an Alien Higgs-4 chip is 1.2mm-1.4mm, and the width of the gap is designed to be 1mm

Furthermore, the antenna is symmetrical about the long side mirror surface, belongs to a symmetrical structure, and the radiation direction of the antenna is vertical to the top and the bottom, namely vertical to the surface of an installation object, so that the antenna is convenient to read.

Compared with the prior art, the invention has the following advantages and effects:

1. the invention adopts a long strip design, has small area and low section, is easy to install, for example, the curved metal surface of the pop can be vertically arranged on the side surface, and the surface of the tin foil paper box can be adhered with the straw by using hot melt adhesive.

2. The invention has the radiation efficiency higher than 30%, obviously higher than the label antenna with the same size, and high radiation efficiency.

3. The invention can be directly processed by adopting the Fr-4 substrate, has low manufacturing cost and is easy to be used commercially.

4. The invention can work well under the optimal design configuration, and can work normally in other application scenes such as metal surfaces, liquid container surfaces, non-conductive object surfaces and the like, and the application scenes are wide.

In conclusion, the antenna of the invention has the advantages of simple structure, easy processing, convenient installation, high radiation efficiency and stable application, and is mainly applied to metal resistance but not only metal resistance.

Drawings

FIG. 1 is a side view of the structure of an embodiment of an UHF anti-metal RFID tag antenna of the present invention;

FIG. 2 is a top view of the structure of an embodiment of the UHF RFID tag antenna of the present invention;

FIG. 3 is a reflection coefficient diagram of an embodiment of the UHF anti-metal RFID tag antenna of the present invention in an optimal design;

fig. 4 shows the radiation pattern of the uhf metal-resistant rfid tag antenna embodiment of the present invention in an optimal design, Phi 270(90) (YOZ plane).

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.

Fig. 1 is a side view of the structure of an embodiment of the present invention, and as shown in fig. 1, an uhf metal-resistant RFID tag antenna includes a dielectric base layer 1, a top radiation layer 2 and a bottom ground layer 3; the top radiation layer 2 and the bottom grounding layer are conductive metal layers; the top radiation layer 2, the bottom ground layer 3 and the medium base layer 1 have the same size, and the length is about one half of the wavelength of the medium in the working frequency band; the top radiation layer 2 and the bottom ground layer 3 are communicated through via holes 4 at two ends of the antenna, and the distance between the two via holes 4 is about one half of the wavelength of the working frequency band medium.

Fig. 2 is a top view of the structure of the embodiment of the present invention, and as shown in fig. 2, the top radiation layer is a symmetrical structure, and the top radiation layer is provided with a bending gap 7 and a gap 6. Bending the gap 7 to form the interdigital capacitor structure 5 by the metal layers on the two sides; the gap 6 is positioned in the middle, the label chip 9 is welded in the middle of the gap 6, and the width of the gap 6 is determined according to the width of the pin of the label chip 9; the interdigital capacitor structure 5 plays a role of series capacitor, and can effectively increase capacitive reactance to reduce the width of the tag antenna; the via holes 8 at both ends of the antenna communicate the top radiating layer and the bottom ground plane.

The top radiation layer, the bottom ground layer and the dielectric substrate are the same in size, the length is about one half of the wavelength of the working frequency band dielectric, in the embodiment, the length of the antenna is preferably 75mm, the width of the antenna is preferably 4mm, and the size of the antenna is similar to that of a common drink straw, so that the antenna is extremely small in size and easy to install. The interdigital capacitor has the width of 0.2mm, the distance between fingers is 0.2mm, the finger length is 6mm, capacitive reactance can be effectively added to reduce the width of the tag antenna, and the width of the embodiment is only 4 mm.

In this embodiment, Fr-4 and Fr-4 with two copper-clad surfaces are used as dielectric base layers, the thickness is 2mm, one copper-clad surface is used as a top radiation layer, a bending gap and a middle gap are formed to form a symmetrical radiation structure, the other copper-clad surface is used as a bottom ground layer, and the copper-clad surfaces are all reserved and are low in cost and convenient to use commercially due to the adoption of a Fr-4 substrate.

The width of the middle gap is determined according to the width of the pin of the tag chip, in this embodiment, the SOT package of the alien higgs-4 chip is adopted, the width of the pin is 1.2-1.4mm, and the width of the gap is preferably 1mm, so that the soldering is facilitated.

Fig. 3 is a 915MHz far-field radiation gain diagram (YOZ plane) of the present embodiment, the maximum gain can reach-1.5 dB, which is better than most metal-resistant tag antennas, and it can be known from the radiation gain diagram that the present embodiment is similar to dipole radiation performance in air, and when located above metal, it will be affected by metal and radiate away from the metal.

The reflection coefficient was measured by attaching the new embodiment to the space above a 45mm x 120mm metal sheet with a 2mm double-sided tape, and the results are shown in fig. 4, which shows that the-10 dB bandwidth of this embodiment reaches 10MHz, and the reflection coefficient at the 915MHz center frequency is less than-20 dB, which is well matched. According to the test results, the embodiment of the invention can work normally in the air directly and when a double-sided adhesive tape with the thickness of 1mm or thermosol is used for being directly attached to a metal surface or the surface of a container containing liquid.

The above embodiments are the best mode for carrying out the invention, but the embodiments of the invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the invention should be regarded as equivalent substitutions, and are included in the scope of the invention.

Claims

1. An anti metal RFID label antenna of hyperfrequency, its characterized in that: comprises a medium base layer, a top radiation layer and a bottom grounding layer; the top radiation layer, the bottom grounding layer and the dielectric base layer are the same in size, the top radiation layer and the bottom grounding layer are made of conductive metal materials, and the top radiation layer and the bottom grounding layer are communicated through holes at two ends of the antenna; the middle of the top radiation layer is provided with a gap, and two sides of the gap are respectively provided with an interdigital capacitor structure.

2. The UHF anti-metal RFID tag antenna of claim 1, further characterized in that the UHF anti-metal RFID tag antenna is designed in a strip shape, the length of the UHF anti-metal RFID tag antenna is about one half of the wavelength of the medium in the working frequency band, and a larger radiation efficiency is realized.

3. The UHF anti-metal RFID tag antenna of claim 1, wherein the slot is used for feeding a solder tag chip, and the slot width is determined according to the pin width of the solder tag chip.

4. The UHF anti-metal RFID tag antenna of claim 1, wherein: the top radiating layer, the bottom ground layer and the dielectric substrate are the same size and have a length of about one-half of the wavelength of the dielectric waveguide.

5. The UHF anti-metal RFID tag antenna of claim 1, wherein: the distance between the two through holes is about one half of the wavelength of the dielectric waveguide.

6. The UHF anti-metal RFID tag antenna of claim 1, wherein the material of the UHF anti-metal RFID tag antenna is Fr-4 with copper on both sides, Fr-4 is a dielectric base layer, one copper-clad surface is used as a top radiation layer, and the other copper-clad surface is used as a bottom ground layer.

7. The UHF anti-metal RFID tag antenna of claim 1, wherein the copper-clad surface as the top radiation layer has a gap in the middle, and two bent gaps are respectively arranged on both sides of the gap to form two interdigital capacitor structures.