CN201383543Y - Tagi electronic lag antenna - Google Patents

Abstract

The utility model discloses a Tagi electronic lag antenna. A Tagi antenna structure is applied to the electronic lag antenna. The Tagi electronic lag antenna comprises a basal plate; an active vibrator and a passive vibrator are arranged on the basal plate; a chip connecting point is arranged on the active vibrator; the active vibrator and the passive vibrator are placed on a same plane; the passive vibrator consists of a director and a reflector; and the passive vibrator is arranged between the director and the reflector. The utility model has the advantages that firstly, the structure is simple; secondly, the impedance of different chips is convenient to be matched and various requirements of RFID antennas at VHF and UHF radio frequency bands can be satisfied; thirdly, the omni-directivity and the sensibility of the RFID antenna are increased, the design difficulty of impedance is reduced, and the applicable scope of RFID is widened; and fourthly, the Tagi electronic lag antenna can be applicable to the etching/stamping antenna process and the conductive ink printing process.

Description

The Yagi spark gap electronic label antenna

Technical field

The utility model relates to a kind of label antenna, relates in particular to a kind of Yagi spark gap electronic label antenna.

Background technology

RFID is the abbreviation of radio RF recognition technology (RadioFrequencyIdentification), RFID is commonly called as electronic tag, the RFID technology is that of rising from nineteen nineties utilizes radiofrequency signal to carry out contactless two-way communication, automatically recognition objective object and obtain the wireless communication technology of relevant information data.Along with progress of science and technology, RFID has related to the various aspects of people's daily life, be widely used in various fields such as industrial automation, business automation, communications and transportation control and management, for example the traffic surveillance and control system of train, Auto Express-way Toll Collector System, Item Management, the streamline production automation, gate control system, financial transaction, warehousing management, livestock management, vehicle anti-theft etc.The RFID technology will become the basic technology that following information-intensive society is built.The most basic rfid system is made up of three parts: label (Tag): be made up of coupling element and chip, each label has unique electronic code, attached to identifying destination object on the object; Reader (Reader): read the equipment of (can also write sometimes) label information, can be designed to hand-hold type or fixed; Antenna (Antenna): between label and reader, transmit radiofrequency signal.Antenna is a key component in the wireless telecommunication system as the equipment of a kind of reception and launching electromagnetic wave, and it is the interface of free space and transmission line.The big line characteristic of label that is operated in UHF and microwave frequency band is influenced by the shape and the physical characteristic of the object that identifies, label is to the distance of the object of labelling, the label dielectric constant of object, the reflection of metal surface, partial structurtes all will influence the performance of antenna to influence of radiation mode etc.Antenna performance also is subjected to the influence of object and environment around the antenna.Barrier can hinder electromagnetic transmission; Metal object produces electromagnetic shielding, can cause correctly reading the electronic tag content; Other broadband signal sources such as engine, water pump, generator and AC/DC changeover switch etc., also can produce electromagnetic interference, influence correctly reading of electronic tag.In the performance parameter of antenna, be affected the maximum impedance matching that antenna is arranged, directivity, anti-interference and read range.

Yagi antenna claims yagi antenna again, and it is a kind of antenna of guiding into, is placed at grade by an active dipole and a plurality of parasitic element, and typical three unit Yagi spark gap symmetry dipole element antennas have three pairs of oscillators, and total is " king " font.The title active dipole that links to each other with feeder line, or main element occupy among three pairs of oscillators centre one horizontal stroke of " king " word.The title reflector more a little longer than active dipole, it is in a side of active dipole, plays a part electric wave that weakening transmits from this direction or the electric wave that goes from the emission of this antenna; Than the slightly short title director of active dipole, it is positioned at the opposite side of active dipole, and it can strengthen the electric wave that transmits from this side direction or launch to this direction.Director can have many, and every length is all a little short than its Na Genlve adjacent and close active dipole.The operation principle of Yagi antenna is such (being received as example with three-element aerial): director slightly is shorter than 1/2nd wavelength, and main element equals 1/2nd wavelength, and reflector slightly is longer than 1/2nd wavelength, two element spacing quarter-waves.At this moment, director is " capacitive " to induced signal, 90 ° of electric current leading voltages; The electromagnetic wave of director induction can be to the main element radiation, radiation signal lags behind from 90 ° of the aerial signals that directly arrives main element it through quarter-wave distance, has offset " in advance " that cause previously just, and both phase places are identical, so the signal superposition is strengthened.Reflector slightly is longer than 1/2nd wavelength, is perception, and after the current hysteresis 90 °, add to be radiated and lag behind again in the main element process 90 °, just in time differed 180 ° with the signal that directly is added on the main element from the reflector direction, played negative function.Individual direction is strengthened, and a direction weakens, and highly directive has just been arranged.The emission state mechanism is as the same.

The utility model content

Technical problem to be solved in the utility model is to provide a kind of strong interference immunity, high, the isotropic Yagi spark gap electronic label antenna of gain at the deficiency of above-mentioned prior art existence.

The utility model is that the technical scheme that problem adopted of the above-mentioned proposition of solution is: it includes a substrate, active dipole and parasitic element are arranged on the substrate, active dipole is provided with the chip tie point, described parasitic element and active dipole are placed at grade, described parasitic element is made of director and reflector, and active dipole is between director and reflector.

Press such scheme, described parasitic element is one and covers copper by PE or cover the aluminium etch process or metal wire that the electrically conductive ink typography is made that active dipole is asymmetric dipole antenna.

Press such scheme, described director and reflector adopt equidimension, thereby at different directions director and reflector each other.

Press such scheme, the distance of described parasitic element and active dipole is decided by the impedance of antenna.

Press such scheme, each component of the input impedance of described active dipole is:

$R_o=\frac{{\left(2\mathrm{\π}{f}_{o}M\right)}^2}{R_{\mathrm{rbo}}}---\left(1\right)$

X _o＝2πf _oL _loop (2)

R wherein _RboBe near the radiation resistance of radiating principal resonance frequency, M is the coefficient of mutual inductance between radiating principal and the electric feedback ring, L _LoopCoefficient of self-inductance for electric feedback ring.

Press such scheme, the length of described parasitic element is corresponding with the wavelength that receives wideband electromagnetic ripple signal, can be 1/2 wavelength, 1/4 or 1/8 wavelength.

Press such scheme, described substrate can be PE, paper substrate, glass or pottery.

Press such scheme, described active dipole adopts PE to cover copper or covers the aluminium etch process or the making of electrically conductive ink typography.

The beneficial effects of the utility model are: 1, simple in structure.2, convenient at the impedance matching of different chips, can satisfy the requirement of various VHF and UHF radio frequency band RFID antenna.3, increase omni-directional, the sensitivity of RFID antenna, reduced the impedance design difficulty, expanded the scope of application of RFID.4, can be applicable to etching/punching press sky Wiring technology and electrically conductive ink typography.

Description of drawings

Fig. 1 is the structure chart of an embodiment of the present utility model.

Fig. 2 is the equivalent structure figure of Fig. 1.

Fig. 3 is the antenna impedance real part analogous diagram of d=5-10mm.

Fig. 4 is the antenna impedance imaginary part analogous diagram of d=5-10mm.

Fig. 5 is the characteristic impedance of antenna curve chart of 820Mhz-920Mhz frequency range.

Fig. 6 is the antenna performance standing-wave ratio schematic diagram of 820Mhz 920Mhz frequency range.

Fig. 7 is the antenna performance directional diagram of 820Mhz-920Mhz frequency range.

Embodiment

Further specify embodiment of the present utility model below in conjunction with accompanying drawing.

The utility model specifically is to add parasitic element with common RFID antenna periphery to form Yagi antenna, with the gain that improves antenna with improve impedance matching.

The utility model includes a substrate 1, active dipole 2 on the substrate 1 (being E and F) and parasitic element A, B, C and D, and active dipole E and F constitute asymmetrical dipole antenna and F is a helical antenna.Be provided with chip tie point T on the active dipole 2, described parasitic element A and B, C and D and active dipole 2 are placed at grade, and described parasitic element A and B, C and D be director and reflector each other, and active dipole 2 is between director and reflector.The distance of parasitic element A, B, C, D and active dipole is decided according to the impedance of antenna, and the length of parasitic element A, B, C, D is corresponding with the wavelength that receives wideband electromagnetic ripple signal, is 1/2 wavelength, to guarantee frequency characteristic to greatest extent.As can be seen from Figure 2, A and B are isometric, and C and D are isometric.When the electromagnetic wave of read-write antenna during from the A direction, A is a director, and B is a reflector, and when read write line electromagnetic wave during from the B direction, B is a director, and A is a reflector, and in like manner, C and D be director and reflector each other.According to the principle of Yagi antenna, the read-write of any one direction all can have resonance preferably at this antenna, thereby the sensitivity that has improved the RFID label antenna effectively, therefore, the main performance of antenna significantly improves, and the reliability of radio-frequency (RF) identification and distance have also all had raising.Baseplate material of the present utility model is selected according to the manufacture craft of antenna, and print process is selected the paper substrate substrate for use usually, and etching method adopts PE to cover rolled copper foil or aluminium foil.

The impedance of label chip generally presents big condensance and little resistance, and such chip impedance makes the design of coupling antenna become very difficult, and limited the impedance bandwidth of antenna.But because the requirement of cost and manufacturing, label antenna must direct and chip coupling.Chang Yong various distortion dipole label antennas there are differences between the frequency of its resonance frequency and coupling in order to realize the impedance matching with chip in the past, caused impedance bandwidth to be narrow-band characteristic.Electromagnetic coupled feed structure model of the present utility model has solved this problem preferably.At the resonance frequency place, each component of the input impedance of active dipole is:

$\mathrm{Ro}=\frac{\left(2\mathrm{\πfoM}\right)2}{\mathrm{Rrbo}}---\left(1\right)$

Xo＝2πfoL _loop (2)

Wherein Rrbo is near the radiation resistance of radiating principal resonance frequency, and M is the coefficient of mutual inductance between radiating principal and the electric feedback ring, L _LoopCoefficient of self-inductance for electric feedback ring.As seen Ro and Xo can independently adjust, and are convenient to realize the coupling of antenna resistance and any chip impedance.Its impedance transformation characteristic such as Fig. 4-shown in Figure 5.

Here a conventional antenna of containing 840～845MHz and two frequency ranges of 920～925MHz has been carried out emulation with IE3D software, simulation result shows that the resonance frequency of this structural antenna is mainly determined by effective electrical length of radiating principal.By Fig. 3 and Fig. 5 as seen, the size of radiating principal and coupling loop is all constant, and when d increased (from 5mm to 10mm), the real part of input impedance reduced between the two, and imaginary part negative slope part weakens disappearance gradually, and coupling weakens, but resonance frequency is constant substantially.Other values remain unchanged, the antenna feed impedance Changing Pattern was similar with Fig. 5 to Fig. 4 when W1 changed, visible radiation main body size is constant, radiating principal and coupling loop spacing are also constant, when the length L 1 of coupling loop or width W 1 increase, the real part and the imaginary part of input impedance all increase, and stiffness of coupling is constant, and resonance frequency slightly reduces.

As seen the adjustment of the antenna feed impedance of this structure and resonance frequency is very convenient, can design label antenna bandwidth and impedance by regulating, and its size is as shown in table 1.

Table 1 coupling feed RFID antenna size

L	W	L1	W1	W2	d
							60	44	21.4	18	1	7

Fig. 6-Fig. 8 is the antenna performance curve for the 820Mhz-920Mhz frequency range.The imaginary part of antenna feed impedance is more smooth near resonance frequency as seen from Figure 6, make antenna and chip impedance conjugate impedance match in the frequency range of a broad, impedance bandwidth reach 77MHz (S11＜-10dB).Two resonance peaks are arranged near 867MHz and 915MHz, and antenna pattern satisfies omni-directional.

The characteristic of this label antenna is as shown in table 2.And the antenna sample of this paper design and a few money antenna on probation at the effective area at 867MHz and 915MHz place more than 1300cm2, TPMF also reaches about 0.8, as seen antenna performance is all more satisfactory.

Table 2 label antenna characteristic value

fx	Ro[Zin](Ω)	Im[Zin](Ω)	PG(db)	G(db)	VSWR	TPMF
							867MHz	19.47	409	-15.38	9.4422	1.1046	0.8064
915MHz	23.27	426.6	-14.8	9.6816	1.2793	0.88946

We also make does not unidimensionally have the antenna of director and reflector to contrast measurement, in radiant power is 4W, under the label antenna measuring condition parallel with the reader antenna face, not having conventional antenna reading distance when centre frequency is 867MHz of director and reflector is 201m; Reading distance can reach 2.6m when centre frequency is 915MHz, reaches application requirements substantially, and antenna reading distance when centre frequency is 867MHz of using the design is 2.79m; Reading distance can reach 3.5m when centre frequency is 915MHz, and performance is better.

Claims (8)

1, a kind of Yagi spark gap electronic label antenna, include a substrate, active dipole and parasitic element are arranged on the substrate, active dipole is provided with the chip tie point, described parasitic element and active dipole are placed at grade, it is characterized in that: described parasitic element is made of director and reflector, and active dipole is between director and reflector.

2, Yagi spark gap electronic label antenna as claimed in claim 1 is characterized in that: described parasitic element is one and covers copper by PE or cover the aluminium etch process or metal wire that the electrically conductive ink typography is made that active dipole is asymmetric dipole antenna.

3, Yagi spark gap electronic label antenna as claimed in claim 2 is characterized in that: described director and reflector adopt equidimension, thereby at different directions director and reflector each other.

4, Yagi spark gap electronic label antenna as claimed in claim 3 is characterized in that: the distance of described parasitic element and active dipole is decided by the sun of antenna is anti-.

5, Yagi spark gap electronic label antenna as claimed in claim 4 is characterized in that: each component of the input impedance of described active dipole is: $R_o=\frac{{\left(2\mathrm{\π}{f}_{o}M\right)}^2}{R_{\mathrm{rbo}}}---\left(1\right)$

X _o＝2πf _oL _loop (2)

R wherein _RboBe near the radiation resistance of radiating principal resonance frequency, M is the coefficient of mutual inductance between radiating principal and the electric feedback ring, L _LoopCoefficient of self-inductance for electric feedback ring.

6, Yagi spark gap electronic label antenna as claimed in claim 5 is characterized in that: the length of described parasitic element is corresponding with the wavelength that receives wideband electromagnetic ripple signal, can be 1/2 wavelength, 1/4 or 1/8 wavelength.

7, as arbitrary described Yagi spark gap electronic label antenna among the claim 1-6, it is characterized in that: described substrate can be PE, paper substrate, glass or pottery.

8, Yagi spark gap electronic label antenna as claimed in claim 7 is characterized in that: described active dipole adopts PE to cover copper or covers the aluminium etch process or the making of electrically conductive ink typography.

Images