KR100688093B1 - Antenna, RFD Tag, and Antenna Impedance Matching Method Using Proximity Coupled Feeding - Google Patents

Abstract

The present invention relates to an antenna using a proximity-coupled feed method, a radio frequency identification (RFID) tag or a transponder using the same, and an antenna impedance matching method.

An antenna according to the present invention comprises a radiation patch for determining a resonance frequency of the antenna, a ground plate positioned in parallel with the radiation patch, and an element connected in parallel between the radiation patch and the ground plate and connected to the antenna. It includes a power supply for providing an RF signal. The feeder may include a dielectric substrate positioned between the radiation patch and the ground plate, and a microstrip line feed line formed on the dielectric substrate to be perpendicular to the resonance length direction of the radiation patch and closely coupled to the radiation patch; And a ground plane positioned to be spaced apart in the direction of the ground plate in parallel with the feed line.

The present invention allows the resistance component and reactance component of the antenna impedance to be freely adjusted independently of each other, and enables efficient broadband matching to an antenna connection element having an arbitrary impedance. In particular, the present invention provides an antenna capable of efficient broadband matching to an RF front-end having a large capacitive reactance compared to a resistance, and an RFID tag using the same.

Description

Antenna Using a Proximity-Coupled Feed Method and RFID Tag Abstract, and Antenna Impedance Matching Method

1 is a block diagram of an RFID system to which the present invention is applied;

2 is a circuit diagram of an equivalent circuit modeling a tag antenna and an RF front end;

3 is a configuration diagram of a tag antenna using a proximity coupled power feeding method according to a first embodiment of the present invention;

4 is a configuration diagram of a tag antenna using a proximity coupled power feeding method according to a second embodiment of the present invention;

5 is a configuration diagram of a tag antenna using a proximity coupled power feeding method according to a third embodiment of the present invention;

6 is a configuration diagram of a tag antenna using a proximity coupled power feeding method according to a fourth embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

110: RFID reader 120: RFID tag

121: RF front end 122: signal processing unit

123: tag antenna 310: radiation patch

320: ground plate 341: feed line

430: shorting plate 530: shorting pin

The present invention relates to an antenna, an RFID tag, and an antenna impedance matching method, and more particularly, an antenna using a proximity-coupled feed method, an RFID tag or a transponder using the same, It relates to an antenna impedance matching method.

RFID tags are used in various fields, such as material management and security, with RFID readers or interrogators. In general, when an object with an RFID tag is placed in a read zone of an RFID reader, the RFID reader modulates an RF signal having a specific carrier frequency to send an interrogation signal to the tag. The RFID tag answers the reader's question. That is, the RFID reader modulates a continuous electromagnetic wave having a specific frequency to send an interrogating signal to the tag, and the RFID tag transmits its information stored in the internal memory to the reader. The electromagnetic wave transmitted from the back-scattering modulation is sent back to the reader. Backscattering modulation is a method of sending information of a tag by modulating the magnitude or phase of the scattered electromagnetic wave when the RFID tag scatters the electromagnetic wave and sends it back to the reader.

The passive RFID tag rectifies the electromagnetic wave transmitted from the reader to use its own power source to obtain its own operating power. In order for the passive tag to operate normally, the intensity of the electromagnetic wave transmitted from the reader at the position where the tag is placed must be greater than or equal to a certain threshold. In other words, the recognition region of the reader is limited by the intensity of the electromagnetic wave transmitted from the reader to the tag. However, the reader's output power is regulated by local regulations, including the US Federal Communication Commission (FCC), so the reader's output power cannot be increased. Therefore, in order to widen the recognition area without increasing the power output of the reader, the RFID tag should efficiently receive the electromagnetic waves transmitted from the reader.

One way to increase the efficiency of RFID tags is to use a separate matching circuit. In general, an RFID tag includes an antenna, an RF front end, and a signal processor, and the RF front end and the signal processor are made of one chip. The matching circuit is a method of maximizing the strength of the signal transmitted from the antenna to the RF front end by conjugate matching the antenna and the RF front end through a separate matching circuit. However, a matching circuit composed of a combination of a capacitor and an inductor requires a large area in a chip, and thus has difficulty in miniaturization and cost.

The present invention has been proposed to solve the above problems, and is formed between the radiation patch and the ground plate perpendicular to the resonant longitudinal direction of the radiation patch microfeed line feed line in the form of a microstrip line (proximity coupled) It is an object of the present invention to provide an antenna having a broadband characteristic that can freely adjust the resistance component and the reactance component of the antenna impedance independently from each other.

Another object of the present invention is to provide an RFID tag that enables efficient broadband matching to an RF front-end having a large capacitive reactance compared to resistance through the antenna. Another object of the present invention is to provide a method for matching impedance of the antenna.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

An antenna according to the present invention for achieving the above object, the radiation patch for determining the resonant frequency of the antenna, a ground plate positioned in parallel with the radiation patch, and is located in parallel between the radiation patch and the ground plate It includes a power supply for providing an RF signal to the device connected to the antenna. The feeder may include a dielectric substrate positioned between the radiation patch and the ground plate, and a microstrip line feed line formed on the dielectric substrate to be perpendicular to the resonance length direction of the radiation patch and closely coupled to the radiation patch; And a ground plane positioned to be spaced apart in the direction of the ground plate in parallel with the feed line. The ground plane of the power supply unit may use the ground plate. One end of the power supply line may be provided with a terminal to which an element connected to the antenna is connected, and a load may be connected to one end opposite to the end where the terminal is formed. In addition, the feed line may be configured to include a meander structure (meander), the radiating patch and the ground plate may be provided with a short circuit means such as a short plate or a short pin.

In addition, the feeding portion of the antenna according to the present invention, the dielectric substrate positioned between the radiation patch and the ground plate, and formed on the dielectric substrate perpendicular to the resonant longitudinal direction of the radiation patch is micro-coupled to the ground plate It may be configured to include a feed line in the form of a strip line, and a ground plane spaced apart in the radial patch direction in parallel with the feed line. In this case, the radiation patch can be used as the ground plane of the feed section.

An RFID tag or transponder according to the present invention includes an antenna for receiving an RF signal transmitted from an RFID reader, an RF front end for rectifying and detecting the RF signal, and an RF front end. And a signal processor, wherein the antenna comprises: a radiation patch for determining a resonance frequency of the antenna; a ground plate positioned in parallel with the radiation patch; and a resonance length direction of the radiation patch between the radiation patch and the ground plate. And a feeder configured to provide an RF signal to the RF front end through a feedline in the form of a microstrip line that is formed perpendicularly to the radiation patch.

The impedance matching method of the present invention for matching the impedance of the antenna utilizes the property that the equivalent impedance between the radiating patch and the ground plate coupled to the feed line does not change greatly depending on the coupling position on the feed line. The impedance matching method of the present invention as described above utilizes the characteristic that the impedance real part of the antenna changes in accordance with the position of the feed line in the resonance length direction of the radiation patch. In addition, the impedance real part of the antenna is changed according to the magnitude of the coupling capacitance between the ground plate and the feed line to determine the coupling amount of the equivalent impedance between the radiation patch and the ground plate coupled to the feed line. I use it. The impedance imaginary part of the antenna is changed according to the characteristic impedance of the feed line, the impedance of a load connected to one end of the feed line, and the length of the feed line.

The above-described contents of the present invention will become more apparent through the following detailed description with reference to the accompanying drawings, and thus, those skilled in the art to which the present invention pertains may easily implement the technical idea of the present invention. will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a block diagram of an RFID system 100 to which the present invention is applied. The RFID system 100 may include an RFID tag 120 storing unique information, an RFID reader 110 having a reading and decrypting function, and a host computer processing data read from the RFID tag 120 through the RFID reader 110. (Not shown).

The RFID reader 110 includes an RF transmitter 111, an RF receiver 112, and a reader antenna 113, and the reader antenna 113 is electrically connected to the RF transmitter 111 and the RF receiver 112. . The RFID reader 110 transmits an RF signal to the RFID tag 120 through the RF transmitter 111 and the reader antenna 113. In addition, the RFID reader 110 receives an RF signal from the RFID tag 120 through the reader antenna 113 and the RF receiver 112. As shown in US Pat. No. 4,656,463, the configuration of the RFID reader 110 is well known in the art and thus a detailed description thereof will be omitted.

The RFID tag 120 includes an RF front end 121, a signal processor 122, and a tag antenna 123 according to the present invention. In the case of the passive RFID tag, the RF front end 121 converts the received RF signal into a DC voltage to supply power required for the signal processing unit 122 to operate. In addition, the RF front end 121 extracts the baseband signal from the received RF signal. As shown in US Pat. No. 6,028,564, the configuration of the RF front end 121 is well known in the art and thus a detailed description thereof will be omitted. The signal processor 122 may also be in any form known in the art, examples of which are shown in US Pat. No. 5,942,987.

Looking at the operation of the RFID system 100, the RFID reader 110 modulates an RF signal having a specific carrier frequency and sends an interrogation to the RFID tag 120. The RF signal generated by the RF transmitter 111 of the RFID reader 110 is transmitted to the outside in the form of electromagnetic waves through the reader antenna 113. The electromagnetic wave 130 transmitted to the outside is transmitted to the tag antenna 123, and the tag antenna 123 transmits the received electromagnetic wave to the RF front end 121. If the size of the RF signal transmitted to the RF front end 121 is greater than or equal to the minimum power required for the RFID tag 120 to operate, the RFID tag 120 scatters back the electromagnetic wave 130 transmitted from the RFID reader 110. Modulate to answer questions from the RFID reader 110.

Here, in order to widen the read zone of the RFID reader 110, the intensity of the electromagnetic wave 130 transmitted from the RFID reader 110 should be large enough to provide an operating power required by the RFID tag 120. . In addition, the high-efficiency tag antenna 123 should be capable of transmitting the electromagnetic wave 130 transmitted from the reader to the RF front end 121 with little loss. As a result, in order for the tag antenna 123 to have high efficiency, the tag antenna 123 must have resonance characteristics at the carrier frequency of the RFID reader 110 and be conjugated with the RF front end 121.

), 안테나 임피던스(

), RF 프런트 엔드 임피던스(

)로 구성되어 있다. 전압원(

)과 안테나 임피던스(

)는 태그 안테나(123)의 등가 회로이며, RF 프런트 엔드 임피던스(

)는 RF 프런트 엔드(121)의 등가 회로이다. 안테나 임피던스(

)는 실수부(

)와 허수부(

)를 가진다. 실수부(

)는 태그 안테나(123)의 등가 저항을 의미하고, 허수부(

)는 태그 안테나(123)의 등가 리액턴스를 의미한다. RF 프런트 엔드 임피던스 역시, 실수부(

)와 허수부(

)를 가진다. 실수부(

)는 RF 프런트 엔드(121)의 등가 저항을 의미하고, 허수부(

)는 RF 프런트 엔드(121)의 등가 리액턴스를 의미한다. 2 is an equivalent circuit diagram modeling the tag antenna 123 and the RF front end 121. The circuit is a voltage source (

), Antenna impedance (

), RF front end impedance (

It consists of). Voltage source

) And antenna impedance (

) Is the equivalent circuit of the tag antenna 123, and the RF front end impedance (

) Is an equivalent circuit of the RF front end 121. Antenna impedance (

) Is the real part (

) And imaginary part

) Real part (

Denotes an equivalent resistance of the tag antenna 123, and an imaginary part (

Denotes an equivalent reactance of the tag antenna 123. The RF front end impedance is also a real part

) And imaginary part

) Real part (

) Denotes an equivalent resistance of the RF front end 121, and an imaginary part (

Denotes the equivalent reactance of the RF front end 121.

)와 RF 프런트 엔드의 임피던스(

)를 공액 정합시키면, 태그 안테나(123)로부터 RF 프런트 엔드(121)에 최대 전력이 전달된다. 공액 정합이란 두 복소(complex) 임피던스에 대해, 임피던스의 절대값의 크기가 같고, 위상이 서로 반대 부호를 가지도록 하는 것이다. 즉, '

'이고, '

'가 되도록 태그 안테나(123)의 임피던스 또는 RF 프런트 엔드(121)의 임피던스를 조정하면 태그 안테나(123)로부터 RF 프런트 엔드(121)에 최대 전력이 전달된다.In general, the antenna impedance (

) And the impedance of the RF front end (

) Conjugate transfers the maximum power from the tag antenna 123 to the RF front end 121. Conjugated matching is such that, for two complex impedances, the magnitude of the absolute value of the impedance is the same and the phases have opposite signs. In other words, '

'ego, '

When the impedance of the tag antenna 123 or the impedance of the RF front end 121 is adjusted to be ', the maximum power is transmitted from the tag antenna 123 to the RF front end 121.

)과 큰 용량성(capacitive) 리액턴스 성분(

)를 가진다. 따라서 공액 정합을 위한 안테나 임피던스(

)는 작은 저항 성분(

)과 큰 유도성(inductive) 리액턴스 성분(

)를 가져야 하며, 동시에 리더에서 송출되는 전자파의 주파수에 공진하여야 한다. In general, the RF front end 121 of the passive and semi-passive RFID tags is composed of a rectification and detection circuit using a diode, and does not include a separate matching circuit to reduce the area of the chip. Therefore, the impedance of the RF front end 121 has a complex impedance different from that of a typical 50Ω, and due to the characteristics of the rectifying and detecting circuit, a small resistance component in the ultra high frequency (UHF) band (

) And a large capacitive reactance component (

) Therefore, the antenna impedance for conjugate matching (

) Is a small resistance component (

) And large inductive reactance components (

) And at the same time resonate with the frequency of electromagnetic waves emitted from the reader.

3 is a block diagram of a tag antenna 300 using a proximity coupled power feeding method according to a first embodiment of the present invention. The tag antenna 300 according to the present invention has a rectangular radiating patch 310 and a ground plate 320 parallel thereto, and the radiating patch 310 has a microstrip line. Proximity coupling with a feed line 341 in the form of a line. The direction 346 of the feed line 341 is perpendicular to the resonant length direction 311 of the spinning patch 310. That is, as shown in FIG. 3, when the resonance length direction of the radiation patch 310 is in the x direction, the direction 346 of the feed line 341 is in the y direction. The radiation patch 310 and ground plate 320 are placed in parallel at regular intervals 351, all or part of which is filled with any dielectric 350, including air. The resonant frequency of the tag antenna 300 according to the present invention is mainly determined by the length 313 of the radiation patch 310, the width 314 of the radiation patch 310 has a relatively small influence on the resonance frequency. . In general, as the width 314 of the radiation patch 310 increases, the resonance frequency of the antenna becomes slightly smaller.

)과 리액턴스 성분(

)을 서로 독립적으로 자유롭게 조절할 수 없다는 문제점이 있다. 또한, 상기와 같은 종래의 근접 결합 급전 방식으로는 RFID 태그 안테나에 필요한 수 옴(Ω) 정도의 작은 저항 성분(

)을 만들기가 매우 어렵다는 문제점이 있다.In the conventional close coupling power feeding system, the direction of the power feeding line is formed to be the same as the resonance length direction of the spinning patch. A detailed description of this conventional feed coupled feed scheme is presented in DMPozar's article "Increasing the bandwidth of a microstrip antenna by proximity coupling" (Electronics Letters, vol. 23, No. 8, April 1987). However, such a conventional close coupling feeding method has a resistance component of the antenna impedance since the equivalent impedance between the radiating patch and the ground plate coupled to the feeding line varies greatly depending on the coupling position on the feeding line.

) And reactance component (

) Can not be freely adjusted independently of each other. In addition, in the conventional close coupling power supply method as described above, a small resistance component (about a few ohms) required for the RFID tag antenna (

There is a problem that it is very difficult to make.

)과 리액턴스 성분(

)을 서로 독 립적으로 자유롭게 조절할 수 있다. 또한, RFID 태그 안테나에 필요한 수 옴(Ω) 정도의 작은 저항 성분(

)을 쉽게 만들 수 있다. 예를 들어, 방사 패치(310)가 공진 길이 방향(311)에 대한 중심면(330)을 기준으로 대칭 구조를 가지는 경우, 중심면(330)에서 방사 패치(310)와 접지판(320) 사이의 등가 임피던스는 0 [Ω]이 된다. 따라서, 급전 라인(341)을 상기 중심면(330)에 가까이 위치시킬수록 급전 라인(341)에 결합되는 등가 임피던스를 작게 할 수 있으며, 이와 같이 급전 라인(341)의 위치를 조정함으로써 수 옴(Ω) 정도의 작은 저항 성분(

)을 가지는 안테나를 쉽게 제작할 수 있다. 또한, 본 발명에 따른 안테나는, 종래의 근접 결합 급전 방법을 사용하는 안테나와 마찬가지로, 광대역 특성을 가진다.In the antenna according to the invention, the direction 346 of the feed line is perpendicular to the resonant longitudinal direction 311 of the radiation patch. In this case, the equivalent impedance between the radiating patch and the ground plate coupled to the feed line does not vary significantly depending on the coupling position on the feed line. Therefore, the resistance component of the antenna impedance (

) And reactance component (

) Can be freely adjusted independently of each other. In addition, small resistive components, such as a few ohms, required for RFID tag antennas (

) Is easy to create. For example, when the radiation patch 310 has a symmetrical structure with respect to the center plane 330 with respect to the resonance length direction 311, the radiation patch 310 and the ground plate 320 are disposed at the center plane 330. The equivalent impedance of becomes 0 [Ω]. Therefore, as the feed line 341 is positioned closer to the center plane 330, the equivalent impedance coupled to the feed line 341 can be reduced. Thus, by adjusting the position of the feed line 341, several ohms ( Small resistance component (Ω)

It is easy to manufacture the antenna with). In addition, the antenna according to the present invention has a wideband characteristic similarly to the antenna using the conventional close coupling power feeding method.

As shown in FIG. 3, the feeding part 340 of the antenna according to the present invention includes a dielectric substrate 342, a feeding line 341 formed on one side of the dielectric substrate in the form of a microstrip line, and feeding from the dielectric substrate. A ground plane 343 fabricated on the opposite side of the line. The feed part 340 is inserted and positioned between the radiation patch 310 and the ground plate 320, and the ground plane 343 and the ground plate 320 of the feed part are short-circuited by DC. Or AC (Alternating Current) short-circuit through capacitive coupling. In addition, the ground plate 320 may be shared by the ground plane 343 of the power feeding unit 340. That is, one metal plate may be used simultaneously as the ground plate and the ground plane.

In addition, a terminal 344 is formed at one end of the feed line 341 to connect to the RF front end 121, and a load 345 having an arbitrary value is connected to the other end. The load 345 may include an open or shorted case, and is well known to those skilled in the art, including a lumped element and a distributed element. Various shapes of loads can be applied.

)을 결정하는 주요한 요소이다. 일반적으로 상기 중심면(330)과 급전 라인(341) 사이의 거리(331)가 멀수록 안테나 임피던스의 저항 성분(

)이 커진다. 또한, 급전 라인(341)과 방사 패치(310) 사이의 결합 커패시턴스가 클수록 안테나 임피던스의 저항 성분(

)이 커지며, 상기 결합 커패시턴스는 상기 급전 라인의 선폭(347) 및 상기 급전 라인과 상기 방사 패치와의 거리(348)에 의하여 결정된다. 한편, 도 3에서 안테나 임피던스의 리액턴스 성분(

)은 상기 급전 라인(341)의 특성 임피던스(characteristic impedance)와 부하(345)의 값 및 상기 부하(345)로부터 급전 터미널(344)까지의 급전 라인(341)의 전체 길이에 의하여 주로 결정된다.When the antenna 300 according to the present invention resonates, the equivalent impedance between the radiation patch 310 and the ground plate 320 where the feed line 341 is located mainly has a resistance component, and the resistance component has a capacitance. It is coupled to the feed line 341 via sex coupling. The amount of such capacitive coupling is primarily determined by the coupling capacitance between feed line 341 and spinning patch 310. In FIG. 3, the magnitude of the coupling capacitance and the distance 331 from the center plane 330 of the radiation patch 310 to the feed line 341 are determined by the resistance component (the total antenna impedance).

) Is a major factor in determining In general, the farther the distance 331 between the center plane 330 and the feed line 341 is, the resistance component of the antenna impedance (

) Becomes large. In addition, as the coupling capacitance between the feed line 341 and the radiation patch 310 increases, the resistance component of the antenna impedance (

), And the coupling capacitance is determined by the line width 347 of the feed line and the distance 348 of the feed line and the spinning patch. Meanwhile, in FIG. 3, the reactance component of the antenna impedance (

) Is mainly determined by the characteristic impedance of the feed line 341 and the value of the load 345 and the total length of the feed line 341 from the load 345 to the feed terminal 344.

)을 조정하고, 방사 패치의 공진 길이 방향에서의 급전 라인의 위치 및 상기 급전 라인과 방사 패치 사이의 결합 커패시턴스를 조절함으로써 안테나 임피던스의 저항 성분(

)을 조정할 수 있다. 즉, 본 발명은 안테나 임피던스의 저항 성분(

)과 리액턴스 성분(

)을 서로 독립적으로 자유롭게 조정할 수 있으므로, 임의의 임피던스를 가지는 RF 프런트 엔드(121)에 효율적인 정합이 가능하다.Therefore, in the case of the antenna structure according to the present invention, the reactance component of the antenna impedance is adjusted by adjusting the characteristic impedance of the feed line 341, the length of the feed line, and the load 345.

) And the resistive component of the antenna impedance by adjusting the position of the feed line in the resonant length direction of the radiation patch and the coupling capacitance between the feed line and the radiation patch.

) Can be adjusted. That is, the present invention provides a resistance component of the antenna impedance (

) And reactance component (

) Can be freely adjusted independently of each other, enabling efficient matching to the RF front end 121 having any impedance.

Meanwhile, in FIG. 3, the length 313 of the radiation patch is determined so that the radiation patch 310 may have a resonance characteristic at an operating frequency. Those skilled in the art can install a shorting plate or a series of shorting pins between the radiation patch 310 and the ground plate 320 to adjust the length of the radiation patch 313 while maintaining the same resonance frequency. It will be appreciated that it can be reduced to about 1/2.

)은 방사 패치(410)와 급전 라인(441) 사이의 결합 커패시턴스 및 단락판(430)과 급전 라인(441) 사이의 거리(431)에 의하여 결정된다.4 is a block diagram of a tag antenna 400 using a proximity coupled power feeding method according to a second embodiment of the present invention. As shown in FIG. 4, in the tag antenna according to the second exemplary embodiment of the present invention, a shorting plate 430 is installed between the radiation patch 410 and the ground plate 420 to provide the radiation patch 410 with the radiation antenna. Shortening the ground plate 420 shortens the length of the radiation patch 413. The shorting plate 430 is installed at one edge of the radiation patch 410 at a right angle (y direction) to the resonance length direction 411 of the radiation patch 410. The width 431 of the shorting plate may be different from the width 414 of the spinning patch. In the case of FIG. 4, the equivalent impedance between the radiation patch 410 and the ground plate 420 in the shorting plate 430 becomes 0 [Ω]. Thus, in Figure 4, the resistive component of the antenna impedance (

) Is determined by the coupling capacitance between the spin patch 410 and the feed line 441 and the distance 431 between the shorting plate 430 and the feed line 441.

)은 방사 패치(510)와 급전 라인(541) 사이의 결합 커패시턴스 및 단락핀이 위치한 곳에서 급전 라인(541)까지의 거리에 의하여 결정된다.5 is a block diagram of a tag antenna 500 using a proximity coupled power feeding method according to a third embodiment of the present invention. As shown in FIG. 5, in the tag antenna according to the third exemplary embodiment of the present invention, a series of shorting pins 530 is installed between the radiation patch 510 and the ground plate 520 so that the radiation patch 510 is connected to the tag antenna. Shortening the ground plate 520 reduces the length of the radiation patch 513. The shorting pins 530 are installed at one edge of the radiation patch 510 at a right angle (y direction) with the resonance length direction 511 of the radiation patch 510. In the case of Figure 5, the equivalent impedance between the radiation patch 510 and the ground plate 520 at the portion where the short pin is located is 0 [Ω]. Thus, in Figure 5, the resistive component of the antenna impedance (

) Is determined by the coupling capacitance between the spin patch 510 and the feed line 541 and the distance from the feed line 541 to where the shorting pin is located.

In addition, the feed line 541 in FIG. 5 includes a meander structure. In FIGS. 3 and 4, the feed lines 341 and 441 have a straight line extending straight, but those skilled in the art include a meander structure in the feed line as shown in FIG. It will be appreciated that feed lines of various structures, which are well known in the art, can be produced.

In addition, in the antenna according to the present invention, in order to reduce the length of the radiation patch while keeping the resonance frequency of the radiation patch constant, the analogy of the dielectric forming a slot in the radiation patch or filling the space between the radiation patch and the ground plate. Various methods well known to those skilled in the art to which the present invention pertains, such as increasing the electrical conductivity, may be applied.

6 is a block diagram of a tag antenna 600 using a proximity coupled power feeding method according to a fourth embodiment of the present invention. In the tag antenna of FIG. 6, unlike the FIGS. 3 to 5, the ground plane of the power supply unit 640 is short-circuited DC to the radiation patch 610 or AC-shorted through capacitive coupling. In addition, the radiation patch 610 may be shared by the ground plane of the feeder. In the case of FIG. 6, the ground plate 620 is closely coupled to the power supply line 641, and the operation contents and effects of the present invention described with reference to FIGS. 3 to 5 are equally applied to the case of FIG. 6.

As described above, although the present invention has been described by means of a limited embodiment and drawings, the present invention is not limited by this and the technical spirit of the present invention and the following by those skilled in the art to which the present invention pertains. Various modifications and variations are possible without departing from the scope of the claims to be described in the following.

The present invention as described above, by placing a feed line in the form of a microstrip line is formed perpendicular to the resonant longitudinal direction of the radiation patch between the radiation patch and the ground plate and proximity coupled to the radiation patch, antenna impedance It is effective to freely adjust the resistance component and reactance component of each other independently. Accordingly, the present invention provides an inexpensive planar antenna capable of efficiently wideband matching to an antenna connection element having any impedance by using a proximity-coupled feed method. In particular, the present invention provides an antenna capable of efficient broadband matching to an RF front-end having a large capacitive reactance compared to a resistance, and an RFID tag using the same.

The antenna and the RFID tag of the close-coupled feeding method of the present invention have a resonance characteristic and a broadband characteristic, and provide excellent characteristics even when attached to a metal surface or an object having a high dielectric constant.

In addition, the present invention provides an impedance matching method of an antenna using the proximity coupling feeding method as described above.

Claims (57)

As an antenna, A radiation patch for determining a resonant frequency of the antenna; A ground plate positioned parallel to the spinning patch; And A feed part disposed in parallel between the radiation patch and the ground plate to provide an RF signal to a device connected to the antenna, The feeding part may include a feeding line in the form of a microstrip line which is formed perpendicular to the resonance length direction of the spinning patch and closely coupled to the spinning patch. Antenna characterized in that. The method of claim 1, The feed section, A dielectric substrate positioned between the radiation patch and the ground plate; A feed line in the form of a microstrip line formed perpendicular to the resonance length direction of the radiation patch on the dielectric substrate and closely coupled to the radiation patch; And And a ground plane positioned to be spaced apart in the direction of the ground plane parallel to the feed line. Antenna characterized in that. The method of claim 2, The ground plane of the power supply unit is characterized in that the short circuit with the ground plate (DC). The method of claim 2, The ground plane of the power supply unit is characterized in that the AC (Alternating Current) short-circuited through the capacitive coupling with the ground plate. The method of claim 2, And the ground plane of the power supply part uses the ground plate. The method of claim 1, An antenna having a terminal to which one element connected to the antenna is connected to one end of the feed line. The method of claim 6, And one end of which is opposite to the end where the terminal is formed in the feed line is open or shorted. The method of claim 6, And an antenna having a load connected to one end of the power supply line, which is located opposite the terminal where the terminal is formed. The method of claim 8, And the load is a lumped element or a distributed element. The method of claim 1, Shorting means for shorting the radiating patch and the ground plate. The method of claim 10, The shorting means is a shorting plate or a shorting pin. The method of claim 1, And said feed line comprises a meander structure. The method of claim 1, And a slot is formed in the radiation patch. The method of claim 1, An antenna filled with a dielectric between the radiating patch and the ground plate. The method of claim 1, Take advantage of the characteristic that the impedance real part of the antenna varies according to the magnitude of the coupling capacitance between the radiation patch and the feed line, which determines the amount of coupling that the equivalent impedance between the radiation patch and the ground plate is coupled to the feed line. Impedance controlled antenna. The method of claim 15, The impedance is adjusted by using the characteristic that the impedance real part of the antenna increases as the coupling capacitance increases. The method of claim 15, The impedance is adjusted by using the characteristic that the coupling capacitance increases as the line width of the feed line increases. The method of claim 15, Impedance-adjusted antenna using the characteristic that the coupling capacitance increases as the distance between the radiation patch and the feed line is reduced. The method of claim 1, Impedance is adjusted by using the characteristic that the impedance real part of the antenna changes in accordance with the distance from the center of the resonant longitudinal direction of the radiation patch to the feed line. The method of claim 19, Impedance is adjusted by using the characteristic that the impedance real part of the antenna increases as the distance from the center of the resonance length direction of the radiation patch to the feed line increases. The method of claim 10 The impedance is adjusted by using the characteristic that the impedance real part of the antenna changes in accordance with the distance from the short circuit means to the feed line. The method of claim 21, The impedance is adjusted by using the characteristic that the impedance real part of the antenna increases as the distance from the short circuit means to the feed line increases. The method of claim 1, The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes according to the characteristic impedance of the feed line. The method of claim 8, The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes in accordance with the impedance of the load. The method of claim 1, The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes according to the length of the feed line. As an antenna, A radiation patch for determining a resonant frequency of the antenna; A ground plate positioned parallel to the spinning patch; And A feed part disposed in parallel between the radiation patch and the ground plate to provide an RF signal to a device connected to the antenna, The feeder, the antenna characterized in that it comprises a feed line in the form of a microstrip line is formed perpendicular to the resonant longitudinal direction of the radiation patch and closely coupled to the ground plate. The method of claim 26, The feed section, A dielectric substrate positioned between the radiation patch and the ground plate; A feed line in the form of a microstrip line formed perpendicular to the resonant longitudinal direction of the radiation patch on the dielectric substrate and closely coupled to the ground plate; And And a ground plane positioned spaced apart in the radial patch direction in parallel with the feed line Antenna characterized in that. The method of claim 27, And the ground plane of the power supply unit is short-circuited with the radiation patch in direct current. The method of claim 27, And the ground plane of the feeding part is AC (Alternating Current) short-circuited through the capacitive coupling with the radiation patch. The method of claim 27, And the radiation patch uses the radiation patch. The method of claim 26, And a terminal to which an element connected to the antenna is connected at one end of the power supply line, and an end to which a load is connected to one end opposite to the end where the terminal is formed. The method of claim 26, Shorting means for shorting the radiating patch and the ground plate. The method of claim 26, And said feed line comprises a meander structure. The method of claim 26, An antenna filled with a dielectric between the radiating patch and the ground plate. The method of claim 26, By using the characteristic that the impedance real part of the antenna changes according to the magnitude of the coupling capacitance between the ground plate and the feed line to determine the amount of coupling that the equivalent impedance between the radiation patch and the ground plate is coupled to the feed line Impedance-Adjusted Antenna. The method of claim 26, Impedance is adjusted by using the characteristic that the impedance real part of the antenna changes in accordance with the distance from the center of the resonant longitudinal direction of the radiation patch to the feed line. 33. The method according to claim 32 The impedance is adjusted by using the characteristic that the impedance real part of the antenna changes in accordance with the distance from the short circuit means to the feed line. The method of claim 26, The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes according to the characteristic impedance of the feed line. The method of claim 31, wherein The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes in accordance with the impedance of the load. The method of claim 26, The impedance is adjusted by using the characteristic that the impedance imaginary part of the antenna changes according to the length of the feed line. In a Radio Frequency Identification (RFID) tag, An antenna for receiving an RF signal transmitted from the RFID reader; An RF front end for rectifying and detecting the RF signal; And A signal processor connected to the RF front end; The antenna, A radiation patch for determining a resonant frequency of the antenna; A ground plate positioned parallel to the spinning patch; And A feeder configured to provide an RF signal to the RF front end through a feed line in the form of a microstrip line which is formed perpendicularly to the resonant longitudinal direction of the radiation patch between the radiation patch and the ground plate and closely coupled to the radiation patch. Comprising RFID tag, characterized in that. 42. The method of claim 41 wherein The feed section, A dielectric substrate positioned between the radiation patch and the ground plate; A feed line in the form of a microstrip line formed on the dielectric substrate in a direction perpendicular to the resonance length direction of the radiation patch and closely coupled to the radiation patch; And And a ground plane positioned to be spaced apart in the direction of the ground plane parallel to the feed line. RFID tag, characterized in that. 42. The method of claim 41 wherein An RFID tag having a terminal connected to the front end at one end of the feed line, and having a load connected to one end opposite to the end where the terminal is formed. 42. The method of claim 41 wherein And shorting means for shorting the radiation patch and the ground plate. 42. The method of claim 41 wherein And the feed line comprises a meander structure. 42. The method of claim 41 wherein According to the magnitude of the coupling capacitance to determine the amount of coupling that the equivalent impedance between the radiation patch and the ground plate is coupled to the feed line, and the distance from the center of the resonance length direction of the radiation patch to the feed line RFID tag whose impedance of the antenna is adjusted by using the characteristic that the impedance real part changes. The method of claim 44, The impedance real part of the antenna varies according to the magnitude of the coupling capacitance which determines the amount of coupling that the equivalent impedance between the radiation patch and the ground plate is coupled to the feed line, and the distance from the shorting means to the feed line. The RFID tag of which the impedance of the antenna is adjusted by using a. 42. The method of claim 41 wherein The impedance of the antenna is adjusted by using the characteristic impedance of the feed line, and the characteristic that the impedance imaginary part of the antenna changes in accordance with the length of the feed line. The method of claim 43, RFID impedance of which the impedance of the antenna is adjusted by using the characteristic that the impedance imaginary part of the antenna changes according to the impedance of the load. A radiation patch for determining a resonant frequency of the antenna, a ground plate positioned in parallel with the radiation patch, and formed between the radiation patch and the ground plate perpendicular to the resonance length direction of the radiation patch and closely coupled to the radiation patch. An impedance matching method of an antenna including a feed line in the form of a microstrip line, And an impedance real part of the antenna varies in accordance with a position of the feed line in a resonance length direction of the radiation patch. 51. The method of claim 50, Impedance using the characteristic that the impedance real part of the antenna varies according to the magnitude of the coupling capacitance between the ground plate and the feed line, which determines the amount of coupling that the equivalent impedance between the radiating patch and the ground plate is coupled to the feed line. Matching method. The method of claim 51, wherein And the coupling capacitance varies according to a line width of the feed line and a distance between the radiation patch and the feed line. 51. The method of claim 50, And an impedance real part of the antenna decreases as the distance from the center of the resonance length direction of the radiation patch to the feed line decreases. 51. The method of claim 50 And the impedance real part of the antenna decreases as the distance from the shorting means for shorting the radiating patch and the ground plate becomes smaller. 51. The method of claim 50, Impedance matching method using the characteristic that the impedance imaginary part of the antenna changes in accordance with the characteristic impedance of the feed line. 51. The method of claim 50, Impedance matching method using the characteristic that the impedance imaginary part of the antenna changes according to the impedance of the load connected to one end of the feed line. 51. The method of claim 50, Impedance matching method using a characteristic that the impedance imaginary part of the antenna changes in accordance with the length of the feed line.

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