KR100636384B1 - PIFA, RFID Tag thereof and Antenna Impedance Adjusting Method thereof - Google Patents

Abstract

The present invention relates to a Planar Inverted-F Antenna (PIFA) antenna and a Radio Frequency IDentificaton (RFID) tag using the same.

The present invention achieves miniaturization of the antenna by adjusting the resonance frequency of the antenna using a meander line extending from the radiating edge of the radiation patch, and achieves impedance matching of the antenna by adjusting the capacitive reactance of the antenna. In addition, the present invention extends from the non-radiative edge of the radiating patch, and in particular, achieves impedance matching of the antenna by adjusting the inductive and capacitive reactance of the antenna using slotted stubs. In addition, the present invention achieves miniaturization of the antenna by adjusting the resonance frequency of the antenna using a plurality of shorting plates that short-circuit the radiation patch and the ground plane, and achieves impedance matching of the antenna by adjusting the capacitive reactance of the antenna. In addition, the present invention provides a low-cost and excellent radiation efficiency PIFA antenna by producing a radiation patch of the antenna in the form of sheet metal to support in the air.

PIFA, RFID, Tag, Antenna

Description

FIFA, RFID Tag and Antenna Impedance Adjusting Method

1 is a perspective view of a typical PIFA antenna;

2 is a perspective view of a conventional PIFA antenna;

3 is a perspective view of a PIFA antenna according to an embodiment of the present invention;

4A is a detail view of portion A of FIG. 3;

4B is a detail view of portions B and C of FIG. 3;

4C is a detail view of portion D of FIG. 3;

4D is a detailed view of the spinning patch of FIG. 3; And

5 is a perspective view of an RFID tag according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: ground plane 200: radiation patch

210a, 210b: short-circuit plate 220: reactance adjustment stub

230: meander line 240: feeder

250a, 250b: Support rod

The present invention relates to a Planar Inverted-F Antenna (PIFA) antenna and a radio frequency identification tag and antenna impedance adjusting method using the same. More specifically, a PIFA antenna having a meander line and a reactance adjusting stub And an RFID tag and antenna impedance adjusting method using the same.

Unlike a reader of an active RFID, a tag is attached to an object made of various materials and shapes, and therefore, a basic design concept of a tag antenna is to minimize deterioration of characteristics of an antenna according to an attachment material. In particular, when the tag antenna is attached to a metallic material, much attention must be paid to the antenna design since the return loss characteristics and the radiation pattern characteristics of the antenna may be seriously affected. When a general dipole antenna is approached to a metal body, electromagnetic waves cannot be radiated due to electromagnetic image effects, so an antenna using a metal body as part of a radiation structure should be considered as a metal tag antenna. Representative antennas of this class are microstrip patch antennas and PIFA antennas.

In general, the microstrip patch antenna is easy to manufacture and has the advantage of being lightweight and thin, but because it has a size of half wavelength at the resonance frequency, it is rather large to be used as an antenna for an RFID tag. On the other hand, the PIFA antenna shortens the size of the microstrip patch antenna without the electric field with a conductor plate, and reduces its size by half. Has a magnitude of / 4 wavelength. Therefore, the PIFA antenna is small and can be attached to a metal body.

1 is a perspective view of a typical PIFA antenna, presented in Kashiwa et al. [T. Kashiwa, N. Yoshida and I. Fukai, "Analysis of Radiation Characteristics of Planar Inverted-F Type Antenna on Conductive Body of Hand-held Transceiver by Spiral Network Method", IEE Electronics Letters 3rd August 1989 , Vol. 25, No. 16, pp. 1044-1045]. As shown in the figure, a typical PIFA antenna consists of a ground plane 1, a radiation patch 2, a feed section 3 and a shorting plate 4. The shorting plate 4 short-circuits the radiation patch 2 and the ground plane 1 to reduce its size in half compared to the micro strip patch antenna. The coaxial line is used to feed the feed section 3 at the point where the antenna impedance is 50 ohms. The field of the PIFA antenna is radiated by the radiation patch and the current formed in the ground plane. This is the same as the radiation mechanism of the microstrip patch antenna.

However, the PIFA antenna presented in the paper cannot adjust the antenna impedance at the feed point, so if the feed point where the antenna impedance is 50 ohms is changed according to the change of environment such as the size of the metal body, the position of the feed part is changed. There is a difficulty to do. In addition, the PIFA antenna of the paper has a size of 1/4 wavelength at the resonance frequency, there is a disadvantage that the antenna size is rather large. In addition, the PIFA antenna of the paper does not provide enough functions to satisfy services such as RFID.

Research into realizing multi-band, broadband and miniaturization by combining slots and stubs with such a typical PIFA antenna is being actively conducted. US Patent No. 6,741,214, "Planar Inverted-F Antenna (PIFA) Having a Slotted Radiating Element Providing Global Cellular and GPS-Bluetooth Frequency Response" is one such example. 2 is a perspective view of a PIFA antenna shown in US Pat. No. 6,741,214.

In the conventional PIFA antenna illustrated in FIG. 2, a C-shaped slot is formed in the radiation patch 16 to realize the dual resonance mode, and the capacitive reactance between the radiation patch 16 and the ground plane 11 is adjusted. For this purpose, the impedance adjusting stub 13 is in contact with the radiation patch 16 at a right angle. In addition, the short-circuit metal plate 12 short-circuits the radiation patch 16 and the ground plane 11. The metal structures 12, 13, 14 and 16 are made of sheet metal and coated on dielectric material 17 to maintain physical stability.

However, the PIFA antenna of the patent is difficult to adjust the inductive reactance and the capacitive reactance in a variety of impedance adjustment stub, the feed point for 50 ohms may vary depending on the use environment. In addition, the PIFA antenna of the patent is limited in miniaturization. In addition, the PIFA antenna of the patent has a problem that the bandwidth and radiation efficiency of the antenna is lowered due to the dielectric material used for mechanical stability.

The present invention aims at miniaturization of the antenna by adjusting the resonance frequency of the antenna by using a meander line extending from the radiating edge of the radiating patch in antenna design, and matching the impedance of the antenna by adjusting the capacitive reactance of the antenna. To facilitate the purpose.

In addition, the present invention aims at facilitating impedance matching of the antenna by adjusting the inductive reactance and the capacitive reactance of the antenna by using a slotted stub, which extends from the non-radiating edge of the radiating patch, in antenna design. It is done.

In addition, an object of the present invention is to provide a PIFA antenna having a low cost and excellent radiation efficiency by producing a radiation patch of the antenna in the form of sheet metal and supporting it in the air.

The present invention relates to a radiation patch having a radiating edge and a non-radiating edge, a ground plane, at least one shorting plate to short the radiation patch and the ground plane, and the radiation patch. Provided is a Planar Inverted-F Antenna (PIFA) antenna including a feeding part for providing RF power to the radiating edge and extending from the radiating edge toward the ground plane, and a meander line spaced apart from the ground plane.

The present invention also provides a radiation patch having a radiation edge and a non-radiation edge, a ground plane, at least one shorting plate for shorting the radiation patch and the ground plane, a feeder for providing RF power to the radiation patch, the non-radiation It provides a PIFA antenna comprising a stub extending from an edge to adjust the reactance of the antenna. The stub includes a stub connection portion formed of a plurality of metal plates extending in the direction of the ground plane from the non-radiative edge, a stub body connected to the stub connection portion and spaced apart from the ground plane, and a slot formed in the stub body.

In addition, the present invention provides an RFID tag including the aforementioned PIFA antenna.

In addition, the present invention provides various impedance adjustment methods using the aforementioned PIFA antenna.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a perspective view of a PIFA antenna according to an embodiment of the present invention. PIFA antenna has a ground plane 100 at the bottom, there is a radiation patch 200 at a predetermined distance from the ground plane. The radiation patch 200 and the ground plane 100 are shorted by the shorting plates 210a and 210b. The radiation patch 200 has a radiating edge and a non-radiating edge where radiation is mainly generated. In Fig. 3, A, B and C around the shorting plates 210a and 210b correspond to the non-radiating edges, and D opposite to the shorting plates 210a and 210b corresponds to the radiating edges.

Reactance adjustment stubs 250 extend vertically downward (ie, in the direction of the ground plane 100) from the radiation patch 200 on the non-radiating edges B and C of the antenna. The reactance adjusting stub 250 adjusts the capacitive reactance and the inductive reactance of the antenna. Meander line 230 extends downward from radiating patch 200 at D, the radiating edge of the antenna. Meander line 230 adjusts the resonant frequency of the antenna to contribute to the miniaturization of the antenna. Meander line 230 may also adjust the capacitive reactance of the antenna. Slots formed in the radiation patch 200 affect the resonance frequency of the antenna to contribute to the miniaturization of the antenna.

The feeder 240 is connected to the radiating patch 200 using a coaxial cable to provide RF (Radio Frequency) power at a point where the antenna has an impedance of 50 ohms. Support rods (250a, 250b) is a non-metallic material to ensure the mechanical stability of the antenna. PIFA antenna of the present invention has a structure in which the radiation patch 200 in the air to increase the radiation efficiency. That is, the gap between the radiation patch 200 and the ground plane 100 is empty. In this case, mechanical stability of the antenna may be a problem.

In order to solve this problem, support rods 250a and 250b are positioned between the radiation patch 200 and the ground plane 100 and are connected to the radiation patch 200 and the ground plane 100, respectively. The support rods 250a and 250b use a non-metallic material so as not to affect the electromagnetic waves radiated from the antenna, and are preferably positioned at a weak current distribution on the antenna. Using two supporting rods 250a and 250b and two shorting plates 250a and 250b, the PIFA antenna ensures mechanical stability.

The PIFA antenna according to Fig. 3 will be described in more detail with reference to Figs. 4A, B, C, and D. FIG. 4A shows part A of FIG. 3. The shorting plates 210a and 210b physically short the radiation patch 200 and the ground plane 100 so that an antenna impedance of 50 ohms may be formed around the shorting plates 210a and 210b. The two shorting plates 210a and 210b are spaced apart by a predetermined distance Dp.

By changing the distance Dp of the short-circuit plates 210a and 210b, the position of 50 ohms of the antenna impedance can be changed to various points as necessary. In addition, changing the distance Dp between the shorting plates 210a and 210b may change the capacitive reactance between the two shorting plates 210a and 210b, and thus may be used for antenna impedance matching. Increasing the spacing Dp of the shorting plates 210a and 210b increases the capacitive reactance between the two shorting plates 210a and 210b. On the contrary, if the gap Dp of the shorting plates 210a and 210b is reduced, the capacitive reactance between the two shorting plates 210a and 210b is reduced.

On the other hand, the resonant frequency of the antenna is changed according to the width Wp of the short-circuit plates 210a and 210b. That is, when the width Wp of the shorting plates 210a and 210b increases, the resonance frequency increases. When the width Wp decreases, the resonance frequency decreases. Therefore, when the widths of the two shorting plates Wp are set differently, the resonance frequency of the antenna may be variously changed.

Those skilled in the art will appreciate that the shorting plate may consist of three or more.

4B illustrates portions B and C of FIG. 3. The reactance adjusting stub 220 extends vertically downward (ie in the direction of the ground plane 100) from the radiation patch 200. Since the reactance adjusting stub 220 is located at the non-radiating edge of the antenna, it does not significantly affect the antenna radiation pattern. The reactance adjusting stub 220 includes a stub body 222 and stub connecting portions 224a and 224b. The stub connections 224a and 224b are two metal plates that extend vertically downward at the non-radiative edge of the spinning patch 200 and are connected to the stub body 222. The stub body 222 has a slot 260 is formed.

By adjusting the spacing Dc of the stub connectors 224a and 224b, the capacitive reactance between the two stub connectors 224a and 224b can be adjusted. Increasing the spacing Dc of the stub connectors 224a and 224b increases the capacitive reactance between the two stub connectors 224a and 224b. Conversely, reducing the distance Dc between the stub connections 224a and 224b reduces the capacitive reactance between the two stub connections 224a and 224b.

In addition, by adjusting the length Hc of the stub connection portions 224a and 224b, the capacitive reactance between the stub body 222 and the ground plane 100 may be adjusted. Adjusting the length Hc of the stub connections 224a and 224b changes the distance between the stub body 222 and the ground plane 100 so that the capacitive reactance between the stub body 222 and the ground plane 100 also changes. do. Increasing the length Hc of the stub connections 224a and 224b reduces the capacitive reactance between the stub body 222 and the ground plane 100. Conversely, reducing the length Hc of the stub connections 224a and 224b increases the capacitive reactance between the stub body 222 and the ground plane 100. That is, the capacitive reactance formed between the reactance adjustment stub 220 and the ground plane 100 may be implemented at various values by the length Hc of the stub connection portions 224a and 224b.

On the other hand, by forming a slot 226 in the stub body 222 to rotate the current flowing through the stub body 222, it is possible to change the inductive reactance. Various inductive reactances can be obtained by adjusting the width Ws and length Hs of the slot 226. That is, the current flowing through the stub body 222 by the slot 226 has a component that rotates, the amount of rotation is determined by the width (Ws) and the length (Hs) of the slot 226, various inductive reactance You can get the value. Increasing the width Ws or length Hs of the slot 226 increases the inductive reactance. Conversely, reducing the width Ws or length Hs of the slot 226 reduces the inductive reactance.

4C illustrates part D of FIG. 3. The meander line 230 extends vertically downward from the radiation patch 200 and is spaced apart from the ground plane 100 by a predetermined distance Hm. Meander line 240 serves to extend the resonant length of radiation patch 230. That is, since the current excited by the feeder 240 flows to the end of the radiation patch 200 and flows to the meander line 230, the resonance length of the antenna is increased by the meander line length. Therefore, the antenna size can be miniaturized.

In FIG. 4C, the overall length of the meander line 230 may be adjusted by adjusting the width Wm of the meander line 230, and various resonance frequencies may be realized through such length adjustment. For example, when the width Wm of the meander line 230 is reduced, the overall length of the meander line 230 may be increased, thereby reducing the resonance frequency. Therefore, it is possible to implement a small antenna that resonates at a specific frequency.

In addition, the distance Hm between the lower end of the meander line 230 and the ground plane 100 may be adjusted to adjust the capacitive reactance value formed between the meander line 230 and the ground plane 100.

4D shows the spin patch 200 of FIG. The radiation patch 200 is formed with "T" type slots 202a, 202b, 206a and 206b, "I" type slot 204 and "c" type slot 208 for miniaturization of the PIFA antenna. The slots formed on the patch 200 reduce the resonance frequency by lengthening the resonance length of the current flowing in the PIFA antenna, so that a compact antenna can be realized. Also, those skilled in the art will appreciate that various slots in addition to the "T", "I" and "c" slots can be formed to reduce the resonant frequency of the antenna. will be.

5 illustrates a Radio Frequency IDentification (RFID) tag to which a PIFA antenna of the present invention is applied. The RFID tag includes a PIFA antenna, an RF transmission / reception board 310, and a digital processing board 320. Since it is the same as that used in the conventional active RFID tag of the RF transceiver board 310 and the digital processing board 320, a detailed description thereof will be omitted and briefly described.

The RF transmission / reception board 310 demodulates an RF signal received through a PIFA antenna according to the present invention, converts the RF signal into a baseband signal, converts the signal into a digital signal, and transmits the digital signal to the digital processing board 320 or the digital processing board 320. Modulates the signal received from the RF signal to the RFID reader (not shown) through the PIFA antenna.

The digital processing board 320 analyzes a digital signal (for example, wake-up, command, etc.) received from the RF transmission / reception board 310 to perform a command, and also transmits the information of the RFID tag to the RFID reader. A digital signal is generated and transmitted to the RF transceiver board 310.

The RF transceiver board 310 and the feeder 210 of the PIFA antenna are connected by a coaxial cable. More specifically, the outer conductor of the coaxial cable is connected to the ground plane 200, the inner conductor is connected to the feed section 210.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

The present invention enables small antennas by increasing the resonant length of the antenna through the various slots formed in the radiation patch. In addition, the present invention facilitates impedance matching of the antenna by placing various types of stubs on the non-radiating edge.

In addition, the present invention makes it possible to change the resonant frequency of the antenna by changing the width and spacing of the shorting plate, and facilitates impedance matching of the antenna. In addition, the present invention forms a meander line at the non-radiated edge to enable miniaturization by changing the resonance frequency of the antenna, and facilitates impedance matching.

In addition, the present invention can be used as a metal-attached active RFID tag antenna that is being actively studied recently, greatly improves the communication performance between the active RFID reader and the tag even in a metal structure environment where the electromagnetic environment is very unstable.

Claims (28)

In a Planar Inverted-F Antenna (PIFA) antenna, A spinning patch having a radiating edge and a non-radiating edge; Ground plane; At least one shorting plate for shorting the radiation patch and the ground plane; A power supply unit providing RF power to the radiation patch; And And a meander line extending from the radiating edge toward the ground plane and spaced apart from the ground plane. The method of claim 1, PIFA antenna having a characteristic that the resonant frequency of the antenna is adjusted according to the width of the meander line. The method according to claim 1 or 2, And a capacitive reactance of the antenna according to a distance between the lower end of the meander line and the ground plane. The method of claim 1, Further comprising a stub extending from the non-radiating edge, The stub is, A stub connection portion formed of a plurality of metal plates extending from the non-radiating edge toward the ground plane; A stub body connected to the stub connection part and spaced apart from the ground plane; And PIFA antenna comprising a slot formed in the stub body. The method of claim 4, wherein PIFA antenna having a characteristic that the capacitive reactance of the antenna is adjusted according to the spacing of the metal plate of the stub connection portion. The method of claim 4, wherein PIFA antenna having a characteristic that the capacitive reactance of the antenna is adjusted according to the length of the stub connection. The method of claim 4, wherein PIFA antenna having a characteristic that the inductive reactance of the antenna is adjusted according to the width or length of the slot. The method according to claim 1 or 4, The PIFA antenna comprises a plurality of short-circuit plate. The method of claim 8, PIFA antenna having a characteristic that the impedance of the antenna is adjusted according to the interval of the short-circuit plate. The method of claim 8, PIFA antenna having a characteristic that the resonance frequency of the antenna is adjusted according to the width of the short-circuit plate. The method of claim 8, PIFA antenna having a different width for each of the short-circuit plates. The method of claim 1, PIFA antenna is formed with a variety of slots in the radiation patch. The method of claim 12, The slot is a PIFA antenna comprising an "I" type, "T" type, "c" type slot. The method of claim 1, PIFA antenna further comprising a non-metallic support rod connecting the radiation patch and the ground plane. In a Planar Inverted-F Antenna (PIFA) antenna, A spinning patch having a radiating edge and a non-radiating edge; Ground plane; At least one shorting plate for shorting the radiation patch and the ground plane; A power supply unit providing RF power to the radiation patch; A stub extending from the non-radiating edge to adjust the reactance of the antenna, The stub is, A stub connection portion formed of a plurality of metal plates extending from the non-radiating edge toward the ground plane; A stub body connected to the stub connection part and spaced apart from the ground plane; And PIFA antenna comprising a slot formed in the stub body. The method of claim 15, And a capacitive reactance of the antenna is adjusted according to the spacing of the metal plate of the stub connector or the length of the stub connector. The method of claim 15, PIFA antenna having a characteristic that the inductive reactance of the antenna is adjusted according to the width or length of the slot. The method of claim 15, The PIFA antenna comprises a plurality of short-circuit plate. The method of claim 18, The impedance of the antenna is adjusted according to the interval of the short-circuit plate, PIFA antenna having a characteristic that the resonance frequency of the antenna is adjusted according to the width of the short-circuit plate. The method of claim 18, PIFA antennas having different widths for each of the shorting plates. The method of claim 15, PIFA antenna is formed with a variety of slots in the radiation patch. The method of claim 15, PIFA antenna further comprising a non-metallic support rod connecting the radiation patch and the ground plane. RFID (Radio Frequency IDentification) tag, PIFA antennas; A digital processor for generating a digital signal for the information of the RFID tag; And An RF transmitter for modulating the digital signal into an RF signal and transmitting through the PIFA antenna, The PIFA antenna, A spinning patch having a radiating edge and a non-radiating edge; Ground plane; At least one shorting plate for shorting the radiation patch and the ground plane; A power supply unit providing RF power to the radiation patch; And A meander line extending from the radiating edge in the direction of the ground plane and spaced apart from the ground plane; RFID tag. RFID (Radio Frequency IDentification) tag, PIFA antennas; A digital processor for generating a digital signal for the information of the RFID tag; And An RF transmitter for modulating the digital signal into an RF signal and transmitting through the PIFA antenna, The PIFA antenna, A radiation patch having a radiation edge and a non-radiation edge; Ground plane; At least one shorting plate for shorting the radiation patch and the ground plane; A power supply unit providing RF power to the radiation patch; A stub connection portion formed of a plurality of metal plates extending from the non-radiating edge toward the ground plane; A stub body connected to the stub connection part and spaced apart from the ground plane; And RFID tag including a slot formed in the stub body In the impedance adjustment method of the PIFA antenna of claim 4, The capacitive reactance of the antenna is adjusted according to the distance between the lower end of the meander line and the ground plane. How to adjust impedance of PIFA antenna The method of claim 25, Capacitive reactance of the antenna is adjusted according to the spacing of the metal plate of the stub connector or the length of the stub connector. How to adjust the impedance of a PIFA antenna. The method of claim 26, By using the characteristic that the inductive reactance of the antenna is adjusted according to the width or length of the slot How to adjust the impedance of a PIFA antenna. The method of claim 27, If there are a plurality of shorting plates, Using the characteristic that the impedance of the antenna is adjusted in accordance with the interval of the short-circuit plate How to adjust the impedance of a PIFA antenna.

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