KR20090097577A - Compact broadband rfid tag antenna - Google Patents

Abstract

A compact broadband RFID tag antenna is provided to obtain a resonant frequency by controlling an interval between a feeding unit and a radiating unit, the thickness of the feeding unit, and a radius of the radiating unit. A compact broadband RFID tag antenna includes a feeding unit(110), an RFID tag chip(130), and a radiating unit(120). The feeding unit rectifies the electronic wave transmitted from the reader and obtains the operation power. The feeding unit supplies the operation power to the radiating unit. The feeding unit has a gap for receiving the RFID tag chip. The radiating unit is formed in the same plane as the feeding unit. The radiating unit obtains the electronic wave from the reader. The radiating unit radiates the electronic wave by the operation power received from the feeding unit. The interval of the radiating unit and the feeding unit is thicker 5 to 30 times than the line thickness of the feeding unit.

Description

Compact broadband RFID tag antenna

The present invention relates to an ultra-wideband RFID tag antenna, and more particularly, to an ultra-wideband RFID tag using a split ring resonator structure modified to overcome the limitation of the half-wavelength of the conventional label-type tag antennas. Relates to an antenna.

RFID (Radio Frequency IDentification) system is a system that wirelessly obtains, identifies, classifies, and processes information of arbitrary objects, and is one of the important methods for realizing the future ubiquitous society.

To maximize the performance of an RFID system, a tag antenna that operates efficiently at limited power is essential. Typical requirements for such tag antennas include first omnidirectional radiation pattern, second simple input impedance control, third wide bandwidth, fourth small size, fifth planar type, and sixth cheap manufacturing cost.

First, the omni-directional radiation pattern is necessary because there is no guarantee that the tag antenna and the reader antenna always face each other in the direction of the maximum gain. If null is present in the pattern of the tag antenna, the recognition distance is greatly affected.

The second requirement is the importance of simple input impedance adjustment. RFID tag chips attached to antennas usually have low resistance and high capacitance impedance, which are different for each manufacturer. Therefore, in order to deliver the maximum power to each tag chip, the input impedance of the antenna requires a low resistance and a high inductance component, which are conjugate matching of the tag chip, and simple input impedance control is required for accurate matching to various tag chips.

The third condition, the wide bandwidth, is that the impedance of the tag chip that is actually presented may vary in part due to manufacturing errors and attachment of the tag chip and antenna. The wide bandwidth to compensate for these errors is an essential requirement for stable tag antenna operation.

Other small size, flat type, and cheap manufacturing cost are important requirements for recognition of small objects and a structure that can be easily printed by printing, thereby making it an efficient design that can be easily produced by mass production and cheap production cost. It is a matter.

There are many limitations to satisfying many of these tag antenna requirements. Of the many frequency bands in which the RFID system is used, the 902-928 MHz band is the most widely used frequency range in the world, and RFID tag antennas with wide bandwidths satisfying this have been proposed (HWSon and CSPyu, "Design of RFID tag"). antennas using an inductively coupled feed, "Electronics Letters, Vol. 41, No. 18, 1st, Sept. 2005. and HWSon, GYChoi and CSPyu," Open-Ended Two-Strip Meander-Line Antenna for RFID Tags, '' See ETRI Journal, Vol. 28, No. 3, June 2006.)

However, due to the large size of about λ / 2 of the resonant frequency, there is a great difficulty in attaching to a small object, in particular, an elongated structure, which is not suitable for application to a small object of a circular shape.

According to the request for recognizing small circular objects, a type of antenna attached to a planar CD is proposed. However, the antenna has a very small bandwidth and is suitable for application to an RFID system in North America having a bandwidth of 26 MHz. (Andrey SA, Manabu K, Toru M and Takashi Y. "Compact Printed-On-CD UHF RFID Tag Antennas," 2007 IEEE Antennas and Propagation Society International Symposium, pp. 5455-5458, June 10-15, 2007 . Reference)

In addition, a passive tag antenna using mutual inductive coupling is proposed as a structure consisting of a helical radiator and a loop feeder attached to a plastic stopper to substantially space a predetermined distance from a liquid stored in a container. Tag antennas have been proposed to minimize the effects on liquids. .29 No.2 pp. 367-370, Sept. 2006.)

However, due to the small bandwidth, this also has limitations for use in RFID systems in North America.

The present invention has been made to solve the problems of the prior art, the feed portion and the radiating portion is located in the same plane structure is easy to manufacture and can reduce the manufacturing cost, miniaturized and has a wide bandwidth, ultra-wideband It is an object to provide an RFID tag antenna.

The ultra-small clown RFID tag antenna according to the present invention for solving as described above,

A power supply unit configured to obtain an operating power by rectifying electromagnetic waves transmitted from a reader, supply the operating power to a radiation unit, and a ring formed with a gap for accommodating an RFID tag chip; An RFID tag chip located in a gap formed in the feed section; It is formed on the outer concentric plane and spaced apart from the feeder, obtains the electromagnetic wave transmitted from the reader and receives the operating power from the feeder to emit electromagnetic waves, the electric half-wave length of the RFID frequency band to be used Characterized in that it comprises a radiating portion having.

The radiating part and the feeding part may be spaced apart at a distance of 5 to 30 times the thickness of the feeding part line.

In addition, the ring shape of the feed portion and the radiating portion is characterized in that any one of polygonal, oval, circular, corrugated oval and corrugated circle.

The ring shape of the feeder and the radiator is square, and the ratio of the length of one side of the feeder and the radiator is 1: 2 to 6, and the feeder and the radiator are 5 to 30 times the thickness of the feeder line. Spaced apart from each other, and the ratio of the thickness of the feeder and the radiator is characterized in that 1: 1 to 3.

In addition, a ring shape of the feed portion and the radiating portion is circular, the ratio of the radius of the feed portion and the radiating portion is 1: 2 to 6, the feed portion and the radiating portion is a distance of 5 to 30 times the thickness of the feed portion line Is spaced apart, the ratio of the thickness of the feed portion and the radiating portion is characterized in that 1: 1 to 3.

In addition, the ring shape of the feed portion and the radiating portion is a corrugated circle, the ratio of the radius of the feed portion and the radiating portion is 1: 2 to 6, the width formed by the wrinkles of the feed portion and the wrinkles formed in the radiating portion The ratio of the width is characterized in that 1: 1 to 3.

According to the ultra-wideband RFID tag antenna according to the present invention as described above,

Depending on the radius of the radiator, the thickness of the feeder, and the spacing between the feeder and the radiator, it has the advantage that it can be easily adjusted to the desired resonance frequency and impedance for conjugate matching of various tag chips, and has a wide half-power bandwidth (102MHz). It can be used in North America, Europe, and Japan, and it can be used in many applications where it is attached to small objects of circular shape with low manufacturing cost because it can be mass-produced in print form because the feeder and radiator are arranged in one plane. There is an advantage.

RFID (Radio Frequency IDentification) technology attaches an electronic tag to each object, wirelessly recognizes a unique ID of the object, and is a technology for identifying the object. RFID systems use a variety of frequency bands, ranging from low frequency bands of 125kHz to microwave bands of 5.8GHz.

Recently, as the demand for remote recognition increases in the distribution and logistics field, the operating frequency of the RFID system has increased beyond the UHF band. As the frequency increases, the design of the RFID tag antenna becomes a very important factor to maximize the performance of the system such as the recognition distance.

In particular, passive RFID tag antennas that do not have a separate battery and rectify the electromagnetic wave transmitted from the reader to obtain their own operating power must deliver the maximum possible power to the tag chip without loss. The perfect match should be made.

The ultra-small clown RFID tag antenna according to the present invention, which can be perfectly matched with a tag chip, is largely comprised of a feeder, a tag chip, and a radiator.

The power supply unit rectifies the electromagnetic wave transmitted from the reader to obtain operating power, and supplies the operating power to the radiation unit. The feeding part is formed of a ring with a gap for accommodating an RFID tag chip. At this time, the shape of the ring forming the feed unit is formed in various forms such as polygon, circle, oval, corrugated circle, corrugated oval, depending on the shape of the object to which the tag antenna is attached.

In this case, a passive RFID tag chip is located in the gap.

The radiating portion is formed on the outer concentric plane spaced apart from the feeding portion by a predetermined distance, and has a length corresponding to about 1/2 of the desired wavelength length electrically. Preferably, the radiating part and the feeding part are spaced apart at a distance of 5 to 30 times the thickness of the feeding part line. Since the distance between the feed portion and the radiating portion is much larger than the metal thickness of the feed portion and the radiating portion, the amount of capacitance coupling generated between the feed portion and the radiating portion is negligible.

The radiation unit acquires electromagnetic waves transmitted from the reader, receives the operating power from the power supply unit, and radiates the electromagnetic waves, and has an electrical half-wave length of an RFID frequency band to be used.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; First, it should be noted that the same components or parts in the drawings represent the same reference numerals as much as possible. In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the gist of the present invention.

1 is a diagram illustrating a micro broadband RFID tag antenna according to a first embodiment of the present invention, and FIG. 2 is a change in input reactance according to the size of a feeder of a micro broadband RFID tag antenna according to a first embodiment of the present invention. 3 is a graph illustrating a change in resonant frequency according to the size of a radiating part of the ultra-wideband RFID tag antenna according to the first embodiment of the present invention, and FIG. 4 is a miniature according to the first embodiment of the present invention. 5 is a graph illustrating a change in input resistance according to a distance between a feeding part and a radiating part of a broadband RFID tag antenna, and FIG. 5 is a simulation and measurement of reflection coefficient and radiation efficiency of a micro broadband RFID tag antenna according to a first embodiment of the present invention. It is a graph showing the results.

As shown in FIG. 1, in the ultra-small wide RFID tag antenna according to the first embodiment of the present invention, the power supply unit 110 and the radiation unit 120 are formed in a ring having a rectangular shape, particularly a square shape. In this case, a ratio (in_x: out_x) of the length of one side of the power supply unit 110 and the radiation unit 120 is 1: 2 to 6, the power supply unit 110 and the radiation unit 120 is the power supply unit It is preferably spaced at a distance of 5 to 30 times the line thickness (in_w), the ratio of the thickness (in_w: out_w) of the feed section 110 and the radiating section 120 is preferably 1: 1 to 3.

The power supply unit 110 is an internal rectangular split ring in which a gap (in_gap) for accommodating an RFID tag chip is formed. An RFID tag chip 130 is connected to the gap. In this case, the power supply unit 110 may adjust the size to generate an input inductance component required for tag antenna matching. At this time, there is no change in the resonant frequency of the antenna, so it can be easily matched.

The radiator 120 is spaced apart from the power supply unit 110 and is formed on an outer concentric plane, and acquires electromagnetic waves transmitted from a reader, and radiates electromagnetic waves by receiving operating power from the power supply unit. An external rectangular split ring having an electrical half-wave length of an RFID frequency band to be desired. The resonance frequency may be adjusted by adjusting the size of the radiator 120, and the input resistance component of the tag antenna may be adjusted by adjusting the interval between the inner and outer rectangular split rings (that is, the gap between the feeder and the radiator). .

In general, when a split ring is applied with an external magnetic field in a direction perpendicular to the split ring, current is induced in the split ring and resonance occurs at 1/8 wavelength. In order to use this, when the tag chip is attached to an internal rectangular split ring, a current is formed in a loop and a magnetic field is formed vertically, thereby resonating the split ring.

In passive RFID tags, tag antennas receive electromagnetic fields from readers to induce current and use them to power tag chips. Therefore, the supply of power that the tag chip can operate limits the recognition distance of the tag.

In general, tag chips have low resistance and high capacitance, and must be conjugated to provide maximum power. Therefore, there must be an inductance component that can cancel out the capacitance component. It has an inductance component because the inner rectangular split ring (feeder) 110 forms a loop.

Since the chip's input impedance is usually different for different chip manufacturers, it is possible to adjust the size of the inner loop to create inductances that can cancel out different capacitances for different chips. A change in the size of the tag antenna input reactance component according to the size of the inner rectangular split ring (feeder 110) is shown in FIG. 2.

In addition, the external rectangular split ring (radiator) 120 determines the size of the entire antenna and can adjust the resonance frequency by adjusting the size of the external rectangular split ring. This is illustrated in FIG. 3.

This split ring structure is similar to the mutual inductive coupling feeding structure, which is a method of designing a wideband tag antenna. The tag antenna of the mutual inductive coupling feed structure can adjust the input impedance by the amount coupled to the radiator. The tag antenna of the structure proposed as the first embodiment of the present invention can also adjust the input impedance of the tag antenna by an amount coupled to an external rectangular split ring (radiator) 120. The amount of coupling is adjustable by the spacing d of the two rectangular split rings 110, 120. As the distance between the two rectangular split rings gets closer, the amount of coupling to the external rectangular split rings increases, and on the Smith chart, the resonance loop increases, so the input impedance increases. The change in input impedance according to the spacing of two rectangular split rings is shown in FIG. 4.

The spacing d between the two rectangular split rings 110 and 120 determines the size of the split ring. Since the resonant frequency is changed according to the size, it is necessary to adjust the resonant frequency a little in order to match the desired reflection coefficient during design, but the tag antenna of the present invention exhibits a wide band characteristic to cover this disadvantage, so that the performance as a tag antenna is sufficient. I can guarantee it.

Simulation experiment of the ultra-wideband RFID tag antenna according to the first embodiment of the present invention was performed to be conjugate matched to the impedance (6.2-j127Ω) of a commercial tag chip manufactured by Alien Technology. In order to match the reflection coefficient of 10dB, the resonance frequency was set to 915MHz, and the detailed split ring parameters are shown in Table 1.

TABLE 1

Parameter Size (mm) out_x 42.5 out_y 42.5 out_w 2 out_gap 2 in_x 10 in_y 10 in_w 0.8 in_gap 2 d 14.25

The results of the reflection coefficient and the radiation efficiency are shown in FIG. 5. The simulation results show that the 10dB bandwidth is 62MHz and is similar to the actual measurement results. Emission efficiency is over 70% in -10dB bandwidth and over 80% in 902MHz ~ 928MHz, the North American RFID frequency band. The overall size is about 43mm × 43mm, so it is suitable for use as a commercial tag.

FIG. 6 is a view illustrating an ultra-wideband RFID tag antenna according to a second embodiment of the present invention. FIG. 7 is a change in input reactance according to the size of a feeder of the ultra-wideband RFID tag antenna according to a second embodiment of the present invention. 8 is a graph illustrating a change in resonant frequency according to the size of a radiating part of the ultra-wideband RFID tag antenna according to the second embodiment of the present invention, and FIG. 9 is a miniature according to the second embodiment of the present invention. 10 is a graph illustrating a change in input resistance according to a distance between a feeding part and a radiating part of a broadband RFID tag antenna. FIG. 10 is a simulation result of reflection coefficient and radiation efficiency of an ultra-wideband RFID tag antenna according to a second embodiment of the present invention. Is a graph.

As shown in FIG. 6, in the ultra-small wide RFID tag antenna according to the second embodiment of the present invention, the feeder 210 and the radiator 220 are formed in a circular ring. At this time, the ratio of the radius (in_r: out_r) of the feeding portion 210 and the radiating portion 220 is 1: 2 to 6, the feeding portion and the radiating portion 5 to 30 of the feed line thickness (in_w) It is spaced at a distance of twice, and the ratio (in_w: out_w) of the thickness of the feed portion and the radiating portion is preferably 1: 1 to 3.

The ultra-small clown RFID tag antenna according to the second embodiment of the present invention also differs in shape, and exhibits the same characteristics as the tag antenna according to the first embodiment described above. It is as described in Table 2]. In addition, the features of the tag antenna structure according to the second embodiment are as shown in Figs.

TABLE 2

Parameter Size (mm) out_r 25.4 out_gap 2 out_w 2 in_r 6 in_gap 0.6 in_w One d 17.4

FIG. 11 is a diagram illustrating an ultra-wideband RFID tag antenna according to a third embodiment of the present invention, and FIG. 12 is a change in input reactance according to the size of a feeder of the ultra-wideband RFID tag antenna according to a third embodiment of the present invention. FIG. 13 is a graph showing a change in resonance frequency according to the size of a radiating part of the ultra-wideband RFID tag antenna according to the third embodiment of the present invention, and FIG. 14 is a miniature according to the third embodiment of the present invention A graph showing a change in input resistance according to a distance between a feeding part and a radiating part of a broadband RFID tag antenna, and FIG. 15 shows simulation and measurement results of reflection coefficients of a micro broadband RFID tag antenna according to a third embodiment of the present invention One graph.

As shown in FIG. 11, the ultra-small wide RFID tag antenna according to the third embodiment of the present invention includes a circular ring in which the feeding part 310 and the radiating part 320 are corrugated. At this time, the ratio of the radius of the feeding portion and the radiating portion (in_r: out_r) is 1: 2 to 6, the ratio of the width formed by the wrinkles of the feed portion and the width formed by the wrinkles of the radiating portion (in_w: out_w) It is preferable that it is 1: 1-3.

The ultra-small wide RFID tag antenna according to the third embodiment of the present invention also differs in shape, and exhibits the same characteristics as those of the tag antennas according to the first and second embodiments described above. The numerical values are as described in [Table 3]. The tag antenna according to the third embodiment is suitable to be designed for the purpose of attachment to places such as plastic plugs or casino chips, which are considerably smaller than the wavelength used (e.g., 900 MHz). Features of the tag antenna structure according to the third embodiment are as shown in FIGS. 12 to 15.

TABLE 3

Parameter Size (mm) out_r 13.2 out_gap 0.5 out_w 4.8 in_r 4.2 in_gap 0.3 in_w 2 tag One d 4.2

The ultra-wideband RFID tag antenna according to the present invention as described above has a structure consisting of two split rings inside and outside by copper foil etching on a PET film, and an inside split ring (feeding unit: 110, 210, 310). ), A tag chip is connected. The impedance characteristics and the resonant frequency can be adjusted by adjusting the distance from the external split ring (radiator: 120, 220, 320), and the miniaturization is possible due to the characteristics of the split ring resonator. In addition, the structure of the internal and external split ring can be designed to fit the object to be attached in a square or circular.

In addition, the ultra-wideband RFID tag antenna according to the third embodiment has a small structure having a radius of about 13 mm by extending the electrical length of the radiator by using a corrugated structure at 902-928 MHz, which is an RFID frequency band in North America. Operation is possible. There are many parasitic capacitances and inductances that occur at the intervals of each corrugated radiator and feeder, but this can be expressed as one equivalent capacitance and equivalent inductance, and it is reflected in the design to effect by parasitic capacitance and parasitic inductance Can be removed.

As described above with reference to the drawings illustrating a micro broadband RFID tag antenna according to the present invention, the present invention is not limited by the embodiments and drawings disclosed herein, those skilled in the art within the scope of the present invention Of course, various modifications may be made.

1 is a view showing a micro broadband RFID tag antenna according to a first embodiment of the present invention;

FIG. 2 is a graph illustrating a change in input reactance according to a size of a feeder of a micro broadband RFID tag antenna according to a first embodiment of the present invention;

3 is a graph showing a change in the resonance frequency according to the size of the radiating part of the ultra-wideband RFID tag antenna according to the first embodiment of the present invention;

4 is a graph illustrating a change in input resistance according to a distance between a feeding part and a radiating part of a micro broadband RFID tag antenna according to a first embodiment of the present invention;

5 is a graph showing the reflection coefficient and the radiation efficiency simulation and measurement results of the ultra-wideband RFID tag antenna according to the first embodiment of the present invention;

6 is a view showing a micro broadband RFID tag antenna according to a second embodiment of the present invention;

FIG. 7 is a graph illustrating a change in input reactance according to a size of a power supply unit of a micro broadband RFID tag antenna according to a second embodiment of the present invention;

8 is a graph illustrating a change in resonance frequency according to a size of a radiating part of a micro broadband RFID tag antenna according to a second embodiment of the present invention;

FIG. 9 is a graph illustrating a change in input resistance according to a distance between a feeding part and a radiating part of a micro broadband RFID tag antenna according to a second embodiment of the present invention;

10 is a graph showing the reflection coefficient and the radiation efficiency simulation and measurement results of the ultra-wideband RFID tag antenna according to the second embodiment of the present invention;

11 is a view showing an ultra-wideband RFID tag antenna according to a third embodiment of the present invention;

12 is a graph illustrating a change in input reactance according to a size of a feeder of a micro broadband RFID tag antenna according to a third embodiment of the present invention;

FIG. 13 is a graph showing a change in resonance frequency according to the size of a radiating part of a micro broadband RFID tag antenna according to a third embodiment of the present invention;

14 is a graph illustrating a change in input resistance according to a distance between a power supply unit and a radiation unit of the ultra-wideband RFID tag antenna according to the third embodiment of the present invention;

FIG. 15 is a graph illustrating reflection coefficient simulation and measurement results of the ultra-wideband RFID tag antenna according to the third embodiment of the present invention.

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

110, 210, 310: Feeding part

120, 220, 320: radiator

130, 230, 330: Tag Chip

in_gap: gap

out_gap: second gap

Claims (6)

A power supply unit configured to obtain an operating power by rectifying electromagnetic waves transmitted from a reader, supply the operating power to a radiation unit, and a ring formed with a gap for accommodating an RFID tag chip; An RFID tag chip located in a gap formed in the feed section; Is formed on the outer concentric plane and spaced apart from the feeder, obtains the electromagnetic wave transmitted from the reader, receives the operating power from the feeder to radiate electromagnetic waves, electrical half-wave of the RFID frequency band to be used Radiator with a length Miniature broadband RFID tag antenna comprising a. The method according to claim 1, The ultra-wideband RFID tag antenna, wherein the radiating portion and the feeding portion are spaced at a distance of 5 to 30 times the thickness of the feeding portion line. The method according to claim 1, The feed portion and the radiating portion has a ring shape of the ultra-small broadband RFID tag antenna, characterized in that any one of polygonal, oval, circular, corrugated oval and corrugated circle. The method according to claim 1, The feed shape of the feeder and the radiator is square, and the ratio of the length of one side of the feeder and the radiator is 1 to 2 to 6, and the feeder and the radiator have a distance of 5 to 30 times the thickness of the feeder line. Spaced apart from each other, wherein the ratio of the thickness of the feeder and the radiator is 1: 1 to 3 ultra wideband RFID tag antenna. The method according to claim 1, The ring shape of the feeder and the radiator is circular, and the ratio of the radius of the feeder and the radiator is 1: 2 to 6, and the feeder and the radiator are spaced at a distance of 5 to 30 times the thickness of the feeder line. The ratio of the thickness of the feed portion and the radiating portion is ultra-small wideband RFID tag antenna, characterized in that 1: 1. The method according to claim 1, The ring shape of the feeder and the radiator is a corrugated circle, and the ratio of the radius of the feeder and the radiator is 1: 2 to 6, the width formed by the wrinkles of the feeder and the width formed by the wrinkles of the radiator. The ratio of 1: 1 to 3 ultra-wideband broadband RFID tag antenna.

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