CN102035071A

CN102035071A - RFID (Radio Frequency Identification) reader antenna with double-frequency circular polarization features

Info

Publication number: CN102035071A
Application number: CN2010105207861A
Authority: CN
Inventors: 李书芳; 洪卫军; 邓力; 尹斯星
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2010-10-27
Filing date: 2010-10-27
Publication date: 2011-04-27

Abstract

The invention discloses an RFID (Radio Frequency Identification) reader antenna with double-frequency circular polarization features and bandwidth stretching capability, comprising a common earth plate 1, radiation units 2 and 7, coupling units 5 and 8, short circuit ground wires 3 and 9, short circuit ground wires 6 and 10, and feed lines 4 and 11. By designing and optimizing parameters of sizes, heights, feed line positions and the like of the radiation units and the coupling units, two resonant frequency points of the antenna can be respectively tuned to two UHF (Ultra High Frequency) sections (840-845MHz and 920-925MHz) applied to the China RFID technology so as to meet the requirements on research, development and application of the RFID device; by regulating the feed-in positions of the feed lines, the input impedance, the resonance frequency and the bandwidth can be adjusted; in addition, the bandwidth features of the antenna can be achieved by reducing the distance between the radiation units and the coupling units.

Description

A kind of rfid interrogator antenna with double frequency round polarized characteristic

Technical field

The invention belongs to electronic technology field, relate to radio-frequency (RF) identification (RFID) the reading and writing device antenna design of hyperfrequency (UHF) frequency range.

Background technology

In recent years, along with developing rapidly of large scale integrated circuit, microelectric technique, information security and advanced manufacturing field, the cost of electronic product manufacturing is significantly reduced, and pocketization of volume, functional diversities are big characteristics of current electronic product.Under such social background, the commercialization of RFID technology is used and is moved to maturity rapidly.Nowadays the RFID The Application of Technology has been deep into the social life every field, comprises logistics and supply chain management, entrance guard management, asset management and tracking, intelligent transportation, financial transaction or the like.The development of RFID technology is subjected to the driving of application demand on the one hand, and the successful Application of RFID has promoted the expansion of application demand conversely again greatly on the other hand.From technical standpoint, the development of RFID technology is embodied in the breakthrough of some key technologies, and related key technology roughly comprises: chip technology, antenna technology, wireless receiving technology, data conversion and coding techniques etc.Wherein, antenna is the media that the signal of telecommunication and space electromagnetic wave signal are transformed mutually, is the key that RFDC is successfully carried out, and the development of antenna technology is all played crucial effects to the realization and the optimization in Properties of RFID functions of the equipments.

Have higher requirement to Antenna Design to the difference of RFID frequency of utilization in each department.The RFID of uhf band uses and mainly concentrates on 860～960MHz, yet the concrete working frequency range that allows is had nothing in common with each other according to the frequency spectrum behaviour in service of various countries, use 902～928MHz as American States such as the U.S., Canada, European countries such as Belgium, France use 865.6～867.6MHz, Australia uses 920～926MHz, two frequency ranges that some country has then given the RFID traffic assignments, as China is 840～845MHz and 920～925MHz, and Singapore is 866～869MHz and 920～925MHz etc.Traditional antenna can only be operated in single frequency band, only is applicable to the fixed frequency range that certain is regional, can not satisfy single frequency band flexibly and use and the two-band demands of applications, does not have general applicability.

Two antenna polarization modes is meant on antenna greatest irradiation direction, also promptly with the perpendicular plane of antenna greatest irradiation direction on, the movement locus of electric field intensity end points generally is divided into linear polarization, circular polarization and oval plan.Because the electromagnetic wave wave equation is a linear differential equation, it is separated and meets principle of stacking, thus one to separate can be that several separate sum.On physical concept, a kind of polarized wave can be formed by stacking by some kinds of polarized waves.Conversely, also can be decomposed a kind of ripple.And arbitrarily the ripple of polarization type can be decomposed into two circularly polarised waves, as, line polarization wave can be made of two original plan ripples that only direction of rotation is opposite, and elliptically polarised wave can be made of the circularly polarised wave of the different opposite spin of two amplitudes.In order to satisfy the flexibility in position requirement of label in the RFID application, the rfid interrogator antenna of circular polarization seems necessary.

Summary of the invention

The object of the present invention is to provide a kind of working band wide and have the double frequency round polarized antenna of working between certain frequency frequency at interval at two, by simple antenna parameter adjustment, can be applied to the uhf band rfid interrogator equipment of different regions in the world.

In order to be applied to China is two very approaching hyperfrequency frequency ranges that RFID distributes, and reach the circular polarization purpose, the present invention has used a pair of two L antennas of placing about the leading diagonal symmetry, for each two L antenna, according to the electromagnetic coupled principle, on the antenna ground level, connected two L type radiation flat boards, one of them is as the primary radiation unit of signal feed-in, another makes antenna have the ability of two-band work for form the inferior radiation unit of radiation because of the electromagnetic signal coupling; By adjusting the position of two frequency ranges, when making two frequency range positions approaching, can form the one-segment bandwidth and increase effect.Simultaneously, because the orthogonality (about the leading diagonal symmetry) of two two L aerial positions can make this aerial radiation circularly polarised wave.Therefore the present invention has the characteristics of double frequency round polarized and broadened bandwidth ability.

The object of the present invention is achieved like this, and a kind of rfid interrogator antenna with double frequency round polarized characteristic and broadened bandwidth ability comprises:

Common ground plate 1;

Radiating element

2,7 and the

coupling unit

5,8 parallel with described common ground plate 1, radiating element 2 and coupling unit 5, radiating element 7 and coupling unit 8 are arranged side by side respectively.

Radiating element

2,7 and common ground plate 1 are respectively by short-circuit grounding wire 3,9 short circuits,

coupling unit

5,8 and common ground plate 1 are respectively by short-

circuit grounding wire

6,10 short circuits, and feeder line 4,11 is directly given

radiating element

2,7 feeds by the perforate above the common ground plate 1 respectively.

Radiating element 2 and coupling unit 5 and radiating element 7 and coupling unit 8 top metal flat board and short circuit metal plate have formed two inverted "L" shaped on the metal plate of common ground, radiating element 2 and coupling unit 5 and radiating element 7 and coupling unit 8 have produced two resonance points simultaneously by the electromagnetic coupling effect between adjacent slits.This invention can be operated on the frequency range that two frequencies are more or less the same, optimize the design parameter of antenna, can make two resonance frequencys lay respectively at China and distribute in two hyperfrequency frequency ranges of RFID technology use, design of the present invention makes antenna have higher gain.Since the coupling unit broadening bandwidth of planar inverted-F antenna, this antenna also can be operated in 860MHz～960MHz frequency range that ISO/IEC recommends simultaneously.

The width of the paster antenna of radiating

element

2,7 of the present invention and

coupling unit

5,8 and highly be the key factor that influences antenna feed impedance, frequency and bandwidth.By optimizing gap width, the patch length of coupling unit and the position of coupling unit short circuit microstrip line between master unit and coupling unit, make the best performanceization of this antenna performance in China distributes to two frequency ranges that RFID uses, solution is widely used in the planar inverted-F antenna bandwidth of RFID technology and the contradiction between performance at present effectively, and can realize the circular polarization characteristics of aerial radiation ripple.

Below in conjunction with embodiment and accompanying drawing invention is described further.

Description of drawings:

Fig. 1 is a circular polarization RFID antenna assumption diagram;

Fig. 2 is an embodiment of the invention structure schematic top plan view;

Fig. 3 is an embodiment of the invention structure schematic side view, wherein schemes a and be the schematic diagram from the right side side-looking, and figure b is the schematic diagram of (front) side-looking from the front side;

Fig. 4 is the structural representation of one embodiment of the present invention;

Fig. 5 is to use simulation software that the return loss of the preferred embodiment is carried out the result that emulation obtains;

Fig. 6 carries out the stereo directional figure that emulation obtains when the 920MHZ to the preferred embodiment of the present invention.

As a preferred embodiment, the length L 2 of the length L 1 of

radiating element length

2,7,

coupling unit

5,8 and their common width W respectively are 60.5mm, 58.5mm, 25.81mm, radiating element and coupling unit are 12.9mm apart from the height h of common ground plate, be 14.9mm apart from G between distance between radiating element 2 and the coupling unit 5 and radiating element 7 and the coupling unit 8, its structure chart as shown in Figure 4.

Claims

1. rfid interrogator antenna with double frequency round polarized characteristic and broadened bandwidth ability comprises:

Common ground plate 1;

Radiating element 2,7 and the coupling unit 5,8 parallel with described common ground plate 1;

Described radiating element 2,7 passes through short-circuit grounding wire 3,9 short circuits with described common ground plate 1 respectively;

Described coupling unit 5,8 passes through short-circuit grounding wire 6,10 short circuits with described common ground plate 1 respectively;

Feeder line 4,11 is given described radiating element 2,7 feeds respectively by the perforate above the described common ground plate 1.

2. a kind of rfid interrogator antenna as claimed in claim 1 with double frequency round polarized characteristic and broadened bandwidth ability, it is characterized in that: described radiating element 2,7 and described coupling unit 5,8 are parallel to described common ground plate 1 to be placed, and 2 and 5,7 and 8 constitute radiation---coupling unit group is about the leading diagonal symmetry of common ground plate 1.

3. radiating element as claimed in claim 2 and coupling unit is characterized in that: by described short-circuit grounding wire 3,6 and short-circuit grounding wire 9,10 and described common ground plate 1 realization short circuit, form two groups of parallel flutings of dual U-shaped in the same way at homonymy.

4. common ground plate as claimed in claim 1 is characterized in that: its shape can be square, circle, ellipse or other shapes, but must be about its leading diagonal symmetry, and its material is a metal, is generally copper or copper-clad plate.

5. radiating element as claimed in claim 3 is characterized in that: can regulate the bandwidth of upper resonance frequency by adjusting height between itself and the described common ground plate 1.

6. feeder line as claimed in claim 1 is characterized in that: signal is fed into described radiating element 2,7, is generally coaxial line.And can regulate input impedance, resonance frequency and bandwidth by adjusting its feed-in position on described radiating element 2,7.

7. radiating element 2,7 as claimed in claim 5 is characterized in that: because respectively and the intercoupling effect between the described coupling unit 5,8, its size is smaller than the resulting size of independent calculating usually.

8. coupling unit 5,8 as claimed in claim 3 is characterized in that: respectively by with the coupling of described radiating element 2,7, produce the resonant frequency point of lower frequency.

9. coupling unit 5,8 as claimed in claim 8, it is characterized in that: it respectively and have certain distance between the described radiating element 2,7 on the parallel arranged direction, by regulating the position of described coupling unit 5,8, change the resonant frequency point that the distance size can obtain the lower frequency of needs.

10. a kind of rfid interrogator as claimed in claim 1 with double frequency round polarized characteristic and broadened bandwidth ability, it is characterized in that: with described radiating element 2,7 respectively and the distance between the described coupling unit 5,8 when being reduced to a certain degree, will obtain a kind of broad-band antenna performance that on quite wide bandwidth, has low reflection coefficient.