CN101299486A - RFID reader-writer antenna capable of overlapping high-frequency and ultrahigh frequency as well as microwave frequency band - Google Patents

Abstract

A three frequency band RFID reader-writer antenna used for a high frequency (HF) and a ultra high frequency (UHF) and a microwave (MW) is provided, specially relates to an antenna used in the laminated flat technology, composed of dielectric plates 1 and 2, a radiating element, an air layer, a ground plate, a coupling and feeding unit. The radiating element is arranged above the dielectric plate 1 grooving along the edge. The ground plate is arranged on one side of the dielectric plate 2 with a gap arranged at the middle, which is fed with the power to the radiating element through the gap. The air layer is arranged between the dielectric plates 1 and 2, adjusting the working bandwidth of the antenna through adjusting the thickness of the air layer and the size of the gap. The electromagnetic coupling and feeding unit is arranged on the other side of the dielectric plate 2 composed of a circle loop and a bicomponent microstrip line, wherein the circle loop provides the HF working performance to the antenna, and the bicomponent microstrip line controls the matching performance of the UHF and the MW. The invention has the characteristics of wider working bandwidth and the high gain, which is suitable for the antenna application of the three frequency band RFID reader-writer.

Description

A kind of rfid interrogator antenna that covers high frequency and hyperfrequency and microwave frequency band

Technical field

The invention belongs to electronic technology field, relate to covering three frequency ranges, high frequency (HF), the rfid interrogator antenna technology of hyperfrequency (UHF) and microwave (MW) frequency range.The present invention relates more specifically to be used for the antenna of laminated flat (stacked patch) technology.

Background technology

Along with being showing improvement or progress day by day and the great demand of field of information management of modern society, the RFID technology progressively has been applied to numerous industries, as logistics and supply chain management, false proof and security control, traffic administration and control, production management etc.In rfid system, antenna plays a crucial role in realizing process of data communication, so Antenna Design is the key of entire RF ID system applies.The Modern wireless communication technical development gets very fast, requirement to antenna technology is also more and more higher, the micro-strip paster antenna of broadband or multiband has all obtained using widely in fields such as cell phone, global positioning system (GPS), synthetic aperture radar (SAR), personal mobile communication, satellite communications because its light weight, low profile, manufacturing are simple, low-cost, easy advantage such as conformal.

Technology related to the present invention can be referring to the United States Patent (USP) the 7th of bulletin on January 1st, 2008,315, No. 283, the dual-band antenna that this prior art disclosed is to utilize additional a plurality of parasitic patch technology to realize UHF from 860MHz to 930MHz and the work of microwave frequency band from 2.45GHz to 2.55GHz, has only 4% frequency bandwidth at microwave frequency band.Rfid system has a plurality of operating frequencies simultaneously, as 13.56MHz, and 915MHz, 2.45GHz etc.Traditional antenna can only be operated in single frequency band, the read write line of using this kind antenna can only read the label of special frequency channel, then need a plurality of read write lines if will read the label that works in different frequency range, bring inconvenience to application, use the antenna of above-mentioned micro-band technique and realize that the reading and writing device antenna of two-frequency operation is still rare so far, and it is just more rare to work in the reading and writing device antenna of three frequency ranges.

Summary of the invention

The object of the present invention is to provide a kind of antenna working band wide, be easy to regulate the RFID three frequency range reading and writing device antennas of coupling.

The technical scheme that the present invention adopts edge fluting technology to combine with stacked patch and cutler feed broadening bandwidth of operation technology.

The object of the present invention is achieved like this, and the rfid interrogator antenna of a kind of covering high frequency (HF) and hyperfrequency (UHF) and microwave (MW) frequency range comprises:

One radiating element, this radiating element is made of the metal on the single face metal medium plate 1, and its shape can be square, rectangle, circle or Else Rule shape, and its size is less than dielectric-slab 1, and the position is in the center of this dielectric-slab.Open two groups of symmetrical grooves at described radiating element, the hyperfrequency (UHF) of the position of groove and size Control antenna and microwave (MW) operating frequency;

One ground plate, this ground plate is positioned at the one side of double-sided metal dielectric-slab 2, opens a slit at center position;

One air layer, this air layer are adjusted the antenna bandwidth of operation by adjusting air layer thickness and gap size between dielectric- slab 1 and 2;

One electromagnetic coupled and feed element, this electromagnetic coupled and feed element are positioned at the another side of double-sided metal dielectric-slab 2, are made up of a loop checking installation and one section two branches microstrip line.This loop checking installation can be square, rectangle, circle, ellipse or other shape, relies on induced field that the service behaviour of antenna high band (HF) is provided.And utilize 1/4th impedance transformer principles, make it be in open-circuit condition at hyperfrequency (UHF) and microwave (MW) frequency range, antenna keeps good matching performance at hyperfrequency (UHF) and microwave (MW) frequency range respectively.The characteristic impedance of every microstrip line all is 100 Ω, by changing pair length controlled system hyperfrequency (UHF) of branches' microstrip line and the matching performance of microwave (MW) frequency range.This electromagnetic coupled and feed element are as the feed side of the electric wave signal of this three band RFIDs reading and writing device antenna;

Dielectric- slab 1 and 2 can be respectively is that 4.5 FR4 and 2.5 Teflon material constitute with dielectric constant, but be not limited to this two media plate, can pass through appropriate change antenna radiation unit size after the parameter of change dielectric-slab, air layer thickness, ground plate gap size and coupling and feed element size obtain the available antenna performance.

The present invention has designed a kind of high frequency (HF) and hyperfrequency (UHF) and microwave (MW) frequency range of working in, and is used for the novel three-frequency paster antenna of rfid system read write line.Mainly by the radiating element of bilateral fluting, the slit of air layer and ground plate is coupled this antenna and the loop checking installation of feed element is realized three work frequently.Wherein the slit of ground plate is to be made of microstrip line, plays the coupling feed.Radiating element is printed on one deck dielectric-slab.Air layer is between the two layer medium plate.The slit of ground plate and following coupling and feed element are printed on another layer dielectric-slab.In order to obtain the service behaviour of hyperfrequency (UHF) and microwave (MW) frequency range, open a pair of symmetrical grooves control hyperfrequency (UHF) resonance frequency at radiating element, the groove of opening a pair of symmetry along its edge other direction is with controlled microwave (MW) resonance frequency.The size that changes fluting can be controlled the frequency ratio of hyperfrequency (UHF) and microwave (MW) resonance frequency.The present invention needs suitably to select the gap size and the air layer thickness of ground plate to adjust the antenna bandwidth of operation.Its advantage be on radiating element suitably fluting can design the paster antenna that works in hyperfrequency (UHF) and microwave (MW) frequency range, and utilize the bandwidth of operation that coupling effect between radiating element and the loading slit can the broadening antenna.In order to obtain the service behaviour of high frequency (HF), introduce a loop checking installation in coupling and feed element, rely on induced field that the service behaviour of antenna high band (HF) is provided.

According to transmission line theory, when terminal connects the transmission line of length-specific, such as quarter-wave the time, can realize that impedance is inverted, i.e. 1/4th impedance transformers.As described in following formula:

Order $l=\frac{\mathrm{\&lambda;}}{4},$ $Z_{\mathrm{in}-\mathrm{\&lambda;}/4}=\underset{\mathrm{\&beta;}.l\&RightArrow;\frac{\mathrm{\&pi;}}{2}}{\lim }({\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="A20081011511200141.png"\; state="\{\{state\}\}">R</figure-callout>}}_0\&CenterDot;\frac{Z_L+\mathrm{<figure-callout\; id="0"\; label="j\; R"\; filenames="A20081011511200141.png"\; state="\{\{state\}\}">j</figure-callout>}{R}_{}{}_0.\mathrm{tg}(\mathrm{\&beta;}.l)}{R_0+j{Z}_L.\mathrm{tg}(\mathrm{\&beta;}.l)})={\left(R_0\right)}^2\&CenterDot;\left(\frac{1}{Z_L}\right)$

Through this variation, can obtain: work as Z _L=0 o'clock, Z _In=∞.Promptly during the terminal short circuit of 1/4th impedance transformers, it is infinitely great that sending-end impedance is seen over, realize open-circuit condition, this point can help to realize the mode of operation of high frequency (HF) coil electromagnetism coupling and not influence the matching performance of hyperfrequency (UHF) and microwave (MW) frequency range, thereby realizes three frequency range working conditions of a antenna.

Loop checking installation one end links to each other with the antenna feed end, and other end shorted to earth forms the loop of a closure.The operation wavelength of design hyperfrequency (UHF) frequency range is λ ₁, the operation wavelength of microwave (MW) frequency range is λ ₂, total electrical length of loop checking installation is l, then works as $l=m\&CenterDot;\frac{{\mathrm{\&lambda;}}_1}{2}+\frac{{\mathrm{\&lambda;}}_1}{4}=n\&CenterDot;\frac{{\mathrm{\&lambda;}}_2}{2}+\frac{{\mathrm{\&lambda;}}_2}{4},$ M, n is a nonnegative integer, during establishment, for the central task frequency of hyperfrequency (UHF) and microwave (MW) frequency range, has seen decyclization shape loop be in open-circuit condition from input, thereby has not influenced the matching performance of antenna in these two frequency ranges.For m, n gets the minimum nonnegative integer that following formula is set up.Here, the actual physical size of loop checking installation is not a definite value, along with the dielectric constant difference of substrate can change.The loop checking installation of high frequency (HF) is near ground plate, in order to make antenna respond well in high frequency (HF) frequency band resonance, and the size that suitably dwindle ground plate.

(HF) loop checking installation important index is exactly a quality factor q, electric current when quality factor have been expressed resonance is the multiple of the electric current when not having resonance, therefore wish that Q is the bigger the better, but resonant circuit has the frequency-selecting characteristics simultaneously, filter just, Q is big more, mean that bandwidth BW is more little, and the transmission data generally are the data of modulation, therefore have certain bandwidth, require the Q value can not be too big again, comprehensive top 2 points, general Q value is for being less than or equal to 20, in applying in radio frequency identification generally employing be about 10 Q value.

For series resonance, Q value computing formula is: $Q=\frac{2\mathrm{\&pi;fL}}{R}$

For parallel resonance, Q value computing formula is: $Q=\frac{R}{2\mathrm{\&pi;fC}}$

The relation of bandwidth and Q: $\mathrm{BW}=\frac{f_0}{Q}$

In the microstrip antenna that general slit loads, the common method of controlling microstrip-fed line coupling is the size that changes the slit.Yet in this slit loaded antenna, the slit is as the coupled radiation body and function, and its size can not change separately, therefore must use other method to control the coupling of feed line.A kind of alternative method is to use two branches feed microstrip line, and the impedance phase of every microstrip line is the coupling of may command feed line by the length that changes two branches microstrip line together.

To with narrow branch's microstrip feed line, its characteristic impedance can be drawn by following empirical equation:

${\mathrm{<figure-callout\; id="0"\; label="Z"\; filenames="A20081011511200141.png"\; state="\{\{state\}\}">Z</figure-callout>}}_0=\frac{{\mathrm{<figure-callout\; id="2"\; label="Z\; f"\; filenames="A20081011511200131.png,A20081011511200141.png"\; state="\{\{state\}\}">Z</figure-callout>}}_f}{2\mathrm{\&pi;}\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{eff}}}}\ln (8\frac{H_f}{w}+\frac{w_s}{4H_f})$

Z wherein _fBe the wave impedance of free space, H _fBe dielectric-slab (dielectric constant ξ _r) thickness, w _sFor microstrip line wide, ε _EffBe that effective dielectric constant is provided by following formula:

${\mathrm{\&epsiv;}}_{\mathrm{eff}}=\frac{{\mathrm{\&epsiv;}}_r+1}{2}+\frac{{\mathrm{\&epsiv;}}_r-1}{2}[{(1+12\frac{H_f}{w_s})}^{-1/2}+0.04{(1-\frac{w_s}{H_f})}^2]$

Since the eighties in 20th century, multiple electromagnetic coupled type feeding classification has appearred, and the common ground of its structure is contactless feed, can form electromagnetic coupled between feeder line and antenna by a slit.For on-chip radiating element, its input admittance is Yp, and the input admittance in the slit of ground plate is Y _aAntenna is by the slit feed that is coupled, and its coupling transform is than being n ₁, the coupling transform between the slit of two branches microstrip line and ground plate is than being n ₂, (the equivalent characteristic impedance is β for the ZO velocity of wave to count the two microstrip line Ls of branch of open circuit _m) reactance, so can obtain total input impedance as shown in the formula:

$Z_{\mathrm{in}}=\frac{{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20081011511200131.png,A20081011511200141.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}^2}{({{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A20081011511200131.png,A20081011511200141.png"\; state="\{\{state\}\}">n</figure-callout>}}_1}^2{Y}_p+Y_a)}-\mathrm{<figure-callout\; id="0"\; label="j\; Z"\; filenames="A20081011511200141.png"\; state="\{\{state\}\}">j</figure-callout>}{Z}_{}{}_0\cot \left({\mathrm{\&beta;}}_m{L}_s\right)$

Wherein resonance frequency is mainly by n ₁ ²Y _p+ Y _aDecide, promptly work as n ₁ ²B _p+ B _a≈ 0 (B _pAnd B _aBe respectively Y _pAnd Y _aImaginary part) time resonance takes place.

Embodiment

The invention will be further described below in conjunction with embodiment and accompanying drawing thereof.

Fig. 1 is an embodiment of the invention structure schematic top plan view;

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

Fig. 3 is an embodiment of the invention coupling equivalent circuit diagram;

Fig. 4 is the return loss simulation result figure of embodiment of the invention correspondence;

Fig. 5 is the simulated gain schematic diagram of embodiment of the invention correspondence;

Fig. 6 is the Q value curve chart of the high band antenna of embodiment of the invention correspondence.

Among the figure:

1-radiating element 2-ground plate 3-coupling and feed element 4-dielectric-slab 15-double-sided metal dielectric-slab 2 6-air layers

Referring to Fig. 1 and Fig. 2, Fig. 1 is embodiment of the invention structure schematic top plan view, and Fig. 2 is the invention process Example structure schematic side view. The present invention is by radiating element 1, earth plate 2, and coupling and feed element 3 are situated between Scutum 14, double-sided metal dielectric-slab 25 and air layer 6 form.

The technology modes such as radiating element 1 employing etching are arranged on the upper surface of dielectric-slab 14, comprise the width branch Be not 111,121 and the degree of depth be respectively two groups of grooves of 112,122. The length of radiating element and width branch Wei 1a and 1b, wherein the width of one group of groove and the degree of depth are respectively 111 and 112, this symmetrical grooves control The microwave of antenna (MW) resonant frequency; Wherein width and the degree of depth of another group groove are respectively 121 and 122, should Hyperfrequency (UHF) resonant frequency of symmetrical groove control antenna.

As a preferred embodiment, the size of 1a and 1b is respectively 95mm and 140mm as shown in Figure 1; Wherein the width 111 of one group of groove and the degree of depth 112 are respectively 35mm and 13mm, and the control resonance frequency is 2.4GHz, are operated in microwave (MW) wave band; Wherein the width 121 and the degree of depth 122 of another group groove are respectively 80mm and 20mm, and the control resonance frequency is 915MHz, is operated in hyperfrequency (UHF) frequency range.

As a preferred embodiment, it is 1.6mm that dielectric-slab 14 adopts thickness, and dielectric constant is ε _r=4.4 polytetrafluoroethylene glass fibre FR4 dielectric-slab, the loss angle tangent of FR4 dielectric-slab is tan δ=0.02, for the size that makes antenna is unlikely to too big, and guarantee enough resonance frequencys, the length a width b of the dielectric-slab 14 of preferred embodiment is respectively 230mm and 155mm, and is bigger than the size of radiating element 1.

Air layer 6 is characterized in that selecting for use thick air layer can increase the bandwidth of operation of antenna between dielectric-slab 14 and double-sided metal dielectric-slab 25, and as a preferred embodiment, the thickness of thick as shown in Figure 2 air layer 6 is 26mm.

The size of ground plate 2 is equal to the length a and the width b of dielectric-slab 14 and double-sided metal dielectric-slab 25.A slit is opened at ground plate 2 centers, mainly plays a part radiating element 1 coupling feed is suitably adjusted, and can make the coupled resonance effect reach best, and the broadening bandwidth of operation is characterized by a big center slot greatly.As a preferred embodiment, referring to Fig. 1, open a slit in the center of ground plate 2, its length 21 and width 22 are respectively 86mm and 12mm.

As a preferred embodiment, it is 1.6mm that double-sided metal dielectric-slab 25 adopts thickness, and dielectric constant is ε _r=2.5 Teflon Teflon dielectric-slab.The size of double-sided metal dielectric-slab 25 is equal to the size of dielectric-slab 14, length a and width b.

Coupling and feed element 3 comprise that length is 311, the degree of depth be 312 and live width be two branches microstrip line of 313, length is 321 to be 322 the microstrip line that is connected with width, and length and width are equal to the length a and the width b on the periphery sides edge of dielectric-slab, the length that the end is one section is 331, and live width is 332 loop checking installation.Invent in the loaded antenna of described slit at this, the slit of ground plate 2 is as the coupled radiation body and function, adjusted and afterwards just can not change separately, therefore adopt this pair branch microstrip line in coupling and feed element 3, the impedance of every microstrip line all is 100 Ω, can coupling of control antenna feed and matching performance by the length 311 that changes branch's microstrip line.The total length of high frequency (HF) frequency range work loop checking installation will suitably be adjusted to satisfy and makes in the antenna match of hyperfrequency (UHF) and microwave (MW) frequency range in order.In order to make ground plate not influence the service behaviour of high frequency (HF) frequency range, suitably dwindle its size, simultaneously so that the edge of the edge of ground plate and loop checking installation maintains a certain distance.

As a preferred embodiment, the length 311 of two branches microstrip line, the degree of depth 312 and live width 313 are respectively 34mm, 25.5mm and 1.2mm, the length 321 that connects microstrip line is 58mm, width 322 is 4.5mm.

In hyperfrequency (UHF) and microwave (MW) frequency range, its center operating frequency is 900MHz and 2.45GHz, and corresponding quarter-wave is respectively 83mm and 31mm, a suitable dimension 750mm of a selected loop checking installation, being approximately nine times of 83mm, is 25 times of 31mm, meets Design Theory.Loop checking installation provides the function of the reading and writing device antenna of 13.56MHz, relies on loop checking installation to provide induced field to make read write line be operated in high frequency (HF) frequency range.Its length is 230mm, and width is 155mm, and line segment 311 length are 104.5mm.

Figure 3 shows that the coupling equivalent circuit diagram of antenna.As a preferred embodiment, the input impedance Z of antenna _InBe designed to 50 Ω.

Figure 4 shows that the simulation result schematic diagram of embodiment of the present invention, as seen from the figure, the central task frequency of the hyperfrequency of antenna (UHF) part is 900MHz, return loss s ₁₁=-19.95dB, standing-wave ratio less than the bandwidth of operation of 2.0 o'clock antennas be about 100MHz (840～940MHz), 11.1% bandwidth is arranged.The central task frequency of the microwave of antenna (MW) frequency range is 2.45GHz, return loss s ₁₁=-27.65dB, standing-wave ratio less than the bandwidth of operation of 2.0 o'clock antennas be about 300MHz (2.12～2.79GHz), reached 27.3% bandwidth.

Shown in Figure 5 at center frequency points 900MHz and 2.4GHz place, the gain of antenna reaches the high-gain values of 6.57dBi and 4.74dBi respectively.

Q value at high frequency (HF) band antenna shown in Figure 6 is approximately 7.5 in the Q value of 13.56MHZ place antenna, and the bandwidth of operation of antenna is approximately 1.8MHz.

Above reference example has been described the present invention, but only is clear in order to understand, and provides foregoing detailed description and example.Should not understand unnecessary restriction thus.All patents described herein and patent application are incorporated herein for your guidance, for a person skilled in the art, under the situation that does not deviate from scope of the present invention, can make many changes in described embodiment.Therefore scope of the present invention does not should be limited to detail described herein and structure, but is limited by the equivalence of the described structure of the language of claim and these structures.

Claims (9)

1, the rfid interrogator antenna of a kind of covering high frequency (HF) and hyperfrequency (UHF) and microwave (MW) frequency range, it is characterized in that: comprise a radiating element that is positioned on the single face metal medium plate 1, one air layer, one is positioned at the ground plate on double-sided metal dielectric-slab 2 one sides, and is positioned at electromagnetic coupled and feed element on double-sided metal dielectric-slab 2 another sides.

2, radiating element as claimed in claim 1 is characterized in that: this radiating element is made of the metal on the dielectric-slab 1, and its shape can be square, rectangle, circle or Else Rule shape.Open two groups of symmetrical grooves at described radiating element, the hyperfrequency (UHF) of the position of groove and size Control antenna and microwave (MW) operating frequency.

3, ground plate as claimed in claim 1 is characterized in that: this ground plate is positioned at the one side of dielectric-slab 2, opens a slit at center position.

4, air layer as claimed in claim 1 is characterized in that: this air layer is adjusted the antenna bandwidth of operation by adjusting air layer thickness and gap size between dielectric-slab 1 and 2.

5, electromagnetic coupled as claimed in claim 1 and feed element is characterized in that: be positioned at the another side of dielectric-slab 2, be made up of a ground connection loop checking installation and one section two branches microstrip line.

6, loop checking installation as claimed in claim 5 is characterized in that: this loop checking installation can be square, rectangle, circle, ellipse or other shape, relies on induced field that the service behaviour of antenna high band (HF) is provided.

7, loop checking installation as claimed in claim 5, it is characterized in that: this loop checking installation utilizes 1/4th impedance transformer principles, make it be in open-circuit condition at hyperfrequency (UHF) and microwave (MW) frequency range, antenna keeps good matching performance at hyperfrequency (UHF) and microwave (MW) frequency range respectively.

8, as claimed in claim 5 pair of branch's microstrip line is characterized in that: the characteristic impedance of every microstrip line all is 100 Ω, by changing pair length controlled system hyperfrequency (UHF) of branches' microstrip line and the matching performance of microwave (MW) frequency range.

9, the rfid interrogator antenna of a kind of covering high frequency as claimed in claim 1 (HF) and hyperfrequency (UHF) and microwave (MW) frequency range, it is characterized in that: dielectric-slab 1 and 2 can be respectively is that 4.5 FR4 and 2.5 Teflon material constitute with dielectric constant, but be not limited to this two media plate, can pass through appropriate change antenna radiation unit size after the parameter of change dielectric-slab, air layer thickness, ground plate gap size and coupling and feed element size obtain the available antenna performance.

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