KR20060045003A - The small planar antenna with enhanced bandwidth and the small rectenna for rfid and wireless sensor transponders - Google Patents

Abstract

A small antenna with improved bandwidth and a small rectenna for use in wireless recognition and wireless sensor transponders are disclosed. According to the present invention, a small antenna having an improved bandwidth includes a dielectric substrate, a metal layer formed on the dielectric substrate, one main slot formed by patterning the metal layer, and a plurality of sub slots connected in one direction of the main slot. It includes, and the plurality of sub-slots are characterized by forming a pair of left and right symmetry around the main slot. According to the planar small antenna according to the present invention, the antenna area substantially involved in the radiation phenomenon is increased, thereby having an improved bandwidth without affecting radiation patterns, efficiency and polarity purity.

Wireless recognition, transponders, antennas, rectennas, matching

Description

The small planar antenna with enhanced bandwidth and the small rectenna for RFID and wireless sensor transponders}

1 is a view of an antenna disclosed in WO 03/094293,

FIG. 2A shows a radiator of a conventional antenna with a straight termination slot, FIG. 2B shows a radiator of a conventional antenna with a rotary termination slot, and FIG. 2C shows a radiator of a conventional antenna with a spiral termination slot. drawing,

3 illustrates conventional transponder antennas.

4 is a perspective view of a planar small antenna according to the present invention;

FIG. 5 is a detailed plan view of a metal layer including a main slot and a plurality of sub slots shown in FIG. 4;

6 shows a magnetic current distribution in the right slot line portion;

7 is a view illustrating radiation patterns of an E plane and an H plane in a conventional antenna;

8 is a view showing radiation patterns of the E plane and the H plane in the planar small antenna according to the present invention;

9 is a graph comparing bandwidth characteristics through a reflection coefficient between an antenna and a conventional antenna according to the present invention;

10 is a view showing a rectenna according to an embodiment of the present invention;

11 is a view illustrating the antenna of FIG. 10 separately;

12 is a diagram illustrating the return loss of an antenna induced by a specific impedance of an actual semiconductor chip.

Brief description of the main parts of the drawing

20: dielectric substrate 30: metal layer

40: main slot 50: feeder

60a, 60b: first subslot 70a, 70b: second subslot

80a, 80b: third subslot 90a, 90b: fourth subslot

61a to 63a: circuit arm area of the first sub slot

71a to 75a: circuit arm area of the second sub slot

81a to 85a: circuit arm area of the third sub slot

91a to 93a: circuit arm area of the fourth sub slot

100: small planar antenna

1000: small rectenna 1110 dielectric substrate

1100: antenna 1120 of FIG. 10: metal layer

1130: main slot

1180a, 1180b: transverse slot

FIELD OF THE INVENTION The present invention relates to planar RF antennas and microwave antennas, and more particularly, to small antennas and / or wireless sensor transponders that are electrically matched to an electronic chip of RFID.

 In the L- and UHF frequencies, even the size of half-wavelength dipoles is excluded from various mobile or RFID applications, requiring a small antenna with a relatively small wavelength. However, the size of the antenna for a given application is not related to the technology used, but is determined by well known physical laws. That is, the size of the antenna associated with the wavelength is a parameter that predominantly affects the radiation characteristics of the antenna.

All antennas are used to convert guided waves into radiated waves or vice versa. Basically, in order to perform this conversion efficiently, the size of the antenna should be about half wavelength or larger. Of course, antennas can be miniaturized if the bandwidth and gain are reduced, or the efficiency and the like are deteriorated.

 For a theoretical review of antenna miniaturization, see the following references in the 1940s and 1960s. H. A. Wheeler, "Fundamental limitations of small antennas," Proceedings of the IRE, vol. 35, pp. 1479-1484, Dec. 1947; L.J. Chu, "Physical limitation on omni-directional antennas," Journal of Applied Physics, vol. 19, pp. 1163-1175, Dec. 1948; R.F. Harrington, "Effect of antenna size on gain, bandwidth and efficiency," Journal of Research of the National Bureau of Standards-D. Radio Propagation, vol. 64D, pp. 1-12, Jan.-Feb. 1960]

Early studies such as these show that small antennas are limited by their fundamental limitations. The smaller the maximum specification of the antenna, the higher the Q factor. In other words, the bandwidth is narrowed. McLean improved the calculation of as little Q as possible for antennas with linear polarity. J.S. McLean, "A re-examination of the fundamental Antenna limits on the radiation Q of electrically small antennas," IEEE Transactions on Antennas and Propagation, vol. 44, pp. 672-676, May 1996]. Therefore, antenna miniaturization techniques always require size, bandwidth, and efficiency (gain) trade-offs. In the case of a planar antenna, a good compromise is obtained when most of a given area of the antenna participates in radiation phenomena, i.e., antenna miniaturization techniques require a compromise of the size, bandwidth and efficiency of the antenna.

The original method of making the size of the antenna smaller than the size of the resonance while maintaining the resonant characteristics with relatively high gain and efficiency is disclosed in WO 03/094293. 1 is a view of the antenna disclosed in WO 03/094293.

Referring to FIG. 1, the antenna 1 includes a main slot 4 and a plurality of sub slots 6a to 6d formed in a pattern in the dielectric substrate 2, the feed line 5, the metal layer 3, and the metal layer 3. ). The metal layer 3 including the main slot 4 and the sub slots 6a to 6d forms a radiating part of the antenna 1.

On the other hand, Figure 2a is a view showing the radiating portion of a conventional antenna having a straight end slot, Figure 2b is a view showing the radiating portion of a conventional antenna having a rotatable termination slot, Figure 2c is a conventional antenna having a spiral termination slot The radiation part of FIG.

2A to 2C, the main slot and the metal layer, which are common components, use the same reference numerals. A plurality of sub slots 8a to 8d, 9a to 9d, and 10a to 10d having various shapes are formed at each end of the main slot 4.

Conventional antennas as described above typically have a narrow bandwidth problem. In addition, the operating frequency bandwidth of the small antenna is an important problem in various applications. Accordingly, it is desirable to provide a small antenna capable of operating at an electrically enhanced bandwidth without affecting radiation patterns, gain and polarization purtiy.

On the other hand, an RFID (Radio Frequency Identification) transponder is a tag device that can respond by transmitting contents of a built-in memory by backscatter communication with an interogator or reader. Passive RFID transponders do not have a battery and instead derive all the required energy from the reader's carrier signal. The passive wireless sensor device includes a semiconductor chip (ex: Application Specific Intergrated Circuit) connected to the antenna. Low cost planar antennas and / or wireless sensor transponders for radio recognition (RFID) having substantially small electrical dimensions are of high interest in recent years. In recent years, even an antenna with a quarter wavelength has been excluded from many applications.

However, implementing a small antenna in a radio recognition and / or wireless sensor transponder design presents another problem. The problem is that the semiconductor chip of the transponder essentially has a complex input impedance with a capacitive reactance. Therefore, in order to operate in the bandwidth of the radio recognition system, the problem of complex conjugate matching between the transponder antenna and the semiconductor chip has to be solved.

Impedance matching between the semiconductor chip and the antenna of the transponder is important for the performance of the first half radio recognition system. In other words, mismatching has a significant effect on the maximum working distance between the interrogator and transponder. Due to certain safety regulations and other legislation, the power radiated at the pager is somewhat limited. The passive RFID transponder rectifies the call signal transmitted from the antenna to obtain driving power.

The rectifier circuit is part of a semiconductor chip, such as an ASIC, with a plurality of diodes (ex: Schottky diodes) and capacitors, which induce a complex input impedance with a substantially capacitive reactance. Typically, the impedance of a semiconductor chip has several to tens of active ohms and hundreds of reactive ohms. Therefore, the ratio of resistance to reactance is very high.

In this situation, the conventional matching technique is implemented with an additional isolated matching circuit based on the inductor. However, this conventional method has a new problem that the manufacturing cost is greatly increased. In addition, isolation matching circuitry introduces additional losses that significantly reduce the performance of the system. Therefore, the impedance of the antenna must be matched directly with the semiconductor chip of the transponder.

In general, a circuit including an antenna and a rectifier circuit is called a recrenna.

3 is a diagram illustrating conventional transponder antennas. Typical conventional transponder antennas are planar structures formed in a metal strip pattern.

3 (a) shows a conventional half-wavelength dipole antenna. By lowering the radiant resistance of the antenna by parallel metal strips and increasing the reactance by the small loop, the impedance of the half-wave dipole is matched with the impedance of the rectifier. As described above, half-wavelength antennas are excluded in many applications. Another example of a half-wavelength dipole antenna is shown in FIG. The impedance of the antenna shown in FIG. 3 (b) is matched by two separate coils. 3C is a diagram illustrating a folded half-wave dipole antenna having a separated coil. Separate coils can be replaced by planar narrow meander strip patterns with inductive properties. The antennas shown in FIGS. 3B, 3C and 3D may suffer additional losses caused by separate coils or narrow strip meanders.

3 (e) and 3 (f) show a small antenna combining a loop and a dipole configuration. World Intellectual Property Organization publication WO 03/044892 A1 (2003.05.30 Bulletin 2003/43) entitled "MODIFIED LOOP ANTENNA WITH OMNIDIRECTIONAL RADIATION PATTERN AND OPTIMIZED PROPERTIES FOR USE IN AN RFID DEVICE" by Varpula et al. An important disadvantage of the antennas shown in FIGS. 3E and 3F is the relatively small antenna cross section (RCS). The antenna reflection region shows how much the antenna diffuses the electromagnetic energy of the incident field. Since the modulated radar reflector is essential for the transmission of data from the transponder to the reader, the radar reflector of the rectenna is very important for backscatter communication.

Accordingly, it would be desirable to provide a rectenna with a conjugated matched small antenna capable of operating with improved radar reflectivity at enhanced bandwidth without affecting radiation patterns, efficiency, polarity purity, and the like.

Accordingly, an object of the present invention is to provide a planar small antenna having an improved operating frequency bandwidth without affecting radiation patterns, radiation efficiency, polarization purity, and the like.

It is also an object of the present invention to have a small antenna that is conjugately matched with a transponder semiconductor chip, having an improved laser reflection area and an operating frequency bandwidth, without affecting radiation patterns, radiation efficiency, polarization purity, etc. It is to provide a rectenna that can operate.

In accordance with an aspect of the present invention, there is provided a planar small antenna having an improved bandwidth including a dielectric substrate; A metal layer formed on the dielectric substrate; A main slot formed in a patterned metal layer, and connected to one end of the main slot, and including a plurality of sub slots connected in a predetermined direction, wherein the plurality of sub slots form a pair of left-right symmetry around the main slot It is preferable.

Here, it is preferable that the predetermined direction is any one of a clockwise direction and a counterclockwise direction.

Here, it is preferable that a plurality of sub slots each having a pair around the main slot have opposite line directions.

Here, the length of the circuit arm of the sub slot is preferably smaller than 1/4 wavelength at the operating frequency of the antenna.

Here, the plurality of sub-slots include a right first sub-slot connected in a clockwise direction from the upper right end of the main slot, and a right second sub-circuit connected in a direction opposite to the right first sub-slot from the inside of the right first sub-slot. Slot, right right sub-slot connecting in the direction opposite to right first sub-slot from the lower right end of the main slot, and right third sub-slot connecting in the opposite direction to the right fourth sub-slot from inside the right fourth sub-slot. It is preferable to include.

In addition, the plurality of sub slots form a pair symmetrically with each of the right first to fourth sub slots around the main slot, and the left first to the first lines that are connected in opposite directions to each of the right first to fourth sub slots. It is preferred to further include 4 subslots.

Here, the length of the line arms of the right first subslot and the right fourth subslot is preferably larger than the length of the line arms of the right second subslot and the right third subslot.

Here, the length of the main slot is preferably smaller than half the wavelength at the operating frequency of the antenna.

 Here, the width of the sub slot and the width of the main slot is preferably the same.

Here, the width of the sub slot is preferably narrower than the width of the main slot.

Here, the width of the sub slot is preferably wider than the width of the main slot.

Preferably, the planar small antenna having the improved operating frequency bandwidth according to the present invention further includes a feed line having a microstripline composed of an open-ended capacitive probe on the back of the dielectric substrate.

Here, the width of the probe is preferably equal to the strip width of the microstripline.

Here, the width of the probe is preferably smaller than the strip width of the microstripline.

Here, the width of the probe is preferably larger than the strip width of the microstripline.

The planar small antenna according to the present invention preferably further includes a feed line having a transmission line located at the rear of the dielectric substrate.

The small lenten according to the present invention comprises a dielectric substrate; A metal layer formed on the dielectric substrate; One main slot patterned in the metal layer; A plurality of sub slots connected to one end of the main slot and connected in a predetermined direction; A plurality of first transverse slots formed perpendicularly to the main slot above the main slots and a plurality of second transverse slots formed perpendicularly to the main slots below the main slots; And an inlet of the semiconductor chip formed inside the main slot.

Here, the main slot, the plurality of sub slots, and the plurality of first and second transverse slots perform conjugate impedance matching with the small rectenna without an external matching element, such that the small rectenna has improved radar reflection in the operating bandwidth of the transponder. It is desirable to have an area.

Here, it is preferable that the some 1st, 2nd crossing slot is symmetrically divided by a main slot.

Here, it is preferable that the predetermined direction is any one of a clockwise direction and a counterclockwise direction.

Here, it is preferable that a plurality of sub slots each having a pair around the main slot have opposite line directions.

Here, the plurality of sub-slots include a right first sub-slot connected in a clockwise direction from the upper right end of the main slot, and a right second sub-circuit connected in a direction opposite to the right first sub-slot from the inside of the right first sub-slot. Slot, right right sub-slot connecting in the direction opposite to right first sub-slot from the lower right end of the main slot, and right third sub-slot connecting in the opposite direction to the right fourth sub-slot from inside the right fourth sub-slot. It is preferable to include.

Also, a pair of symmetrical pairs with each of the right first through fourth subslots of the main slot and a left first through fourth subslots connected in a direction opposite to each of the right first through fourth subslots; It is preferable to further include.

Here, the dielectric substrate and the metal layer are preferably planar.

Here, it is preferable that the semiconductor chip further includes a rectifier circuit.

Hereinafter, with reference to the accompanying drawings illustrating the present invention.

4 is a perspective view of a planar small antenna according to the present invention. Referring to FIG. 4, the planar small antenna 100 includes a dielectric substrate 20, a metal layer 30 formed on the dielectric substrate 20, and a main slot 40 formed in a patterned manner in the metal layer 30. Subslots 60a, 60b, 70a, 70b, 80a, 80b, 90a, 90b, and a feed line 50 formed under the dielectric substrate 20. The metal layer 40 including the main slot 40 and the plurality of sub slots 60a, 60b, 70a, 70b, 80a, and 80b forms a radiating part of the antenna 100.

FIG. 5 is a detailed plan view of a metal layer including a main slot and a plurality of sub slots shown in FIG. 4. Hereinafter, the main slot, the plurality of sub slots, and the metal layer will be collectively referred to as a 'radiation part'.

Referring to FIG. 5, the radiating part includes a metal layer 30, one main slot 40, and a plurality of sub slots 60a, 60b, 70a, 70b, 80a, 80b, 90a, and 90b located at both ends of the main slot 40. ).

Each of the sub slots 60a, 60b, 70a, 70b, 80a, 80b, 90a, and 90b forms a pair around the main slot 40 and is connected to one end of the main slot 40. Each of the sub slots 60a, 60b, 70a, 70b, 80a, 80b, 90a, 90b is bent in a clockwise or counterclockwise shape. Each of the sub slots 60a, 60b, 70a, 70b, 80a, 80b, 90a, 90b has a symmetrical shape with respect to the main slot 40.

That is, the right first sub slot 60a and the right third sub slot 80a have a bent clockwise direction, and the right second sub slot 70a and the right fourth sub slot 90a are counterclockwise. It has a curved shape.

In addition, the left side sub slots 60b, 70b, 80b, and 90b paired with the right side sub slots 60a, 70a, 80a, and 90a have left and right symmetry with the right side subslots 60a, 70a, 80a, and 90a. Since it has a form, the line direction is opposite to the line direction of the right subslots 60a, 70a, 80a, and 90a.

That is, the left first sub slot 60b and the left third sub slot 80b have a counterclockwise line shape, and the left second sub slot 70b and the left fourth sub slot 90b are clockwise. It has a line shape.

In general, the radiation dominates the electromagnetic properties of all antennas. Most areas of the radiator must be used for radiation phenomena to improve the operating bandwidth without affecting the radiation pattern, efficiency, polarization purity, etc. for the miniaturization of the antenna 100.

Unlike the slot pattern in the conventional antenna, the radiator according to the embodiment of the present invention includes four sub-slots formed at one end of the main slot 40, each sub slot has a symmetrical structure around the main slot Have As such, the reason why the present planar small antenna has a very complicated slot structure is as follows.

For the most part, the maximum length of the antenna is less than half the wavelength and even less than 1/4 wavelength, so the length of the main slot is shorter. At the same time, the radiating part of the antenna must maintain the half-wave resonant characteristic. Therefore, in order to reduce the size of the antenna, a specific limit voltage value must be imposed on both ends of the main slot. This produces the desired resonant electromagnetic field distribution on the shortened main slot. To provide the desired voltage discontinuity across the main slot, both ends of the subslot must have inductive characteristics.

If the length of the sub slot is smaller than 1/4 wavelength, inductive loading is ensured. The conventional induction stage is provided by a plurality of sub slots 8a to 8d, 9a to 9d, and 10a to 10d (see Figs. 2, 3 and 4). In the conventional antenna, unlike the induction end of the main slot 4, the induction end of the main slot 40 according to the embodiment of the present invention is the four sub-slots (60a to 60b, 70a to 70b, 80a) of the left and right symmetry type ~ 80b, 90a ~ 90b).

6 is a diagram illustrating a magnetic current distribution in the slot line portion of the present invention. Referring to FIG. 6, the distribution of magnetic current is shown schematically along the arrow. Unique electromagnetic properties are realized by the combination of subslots 60a, 70a, 80a, 90a wound clockwise and counterclockwise. That is, there are six circuit arm regions with the same magnetic current flow as the main slot 40. These six circuit arm regions are shown by reference numerals 62a, 71a, 75a, 81a, 85a, 92a in FIG.

In addition, there are two circuit arm regions with flows opposite to the magnetic current flow in the main slot 40. These two circuit arm regions are shown by reference numerals 73a and 83a in Fig. 6, in which the magnetic current has a small amplitude.

On the other hand, due to the mirror symmetry with respect to the main slot line, the undesirable field coupling effect occurring in the circuit arm regions 72a and 74a, 82a and 84a, 61a and 63a, 91a and 93a is suppressed. do.

Thus, the undesirable consequences of inductive subslots as in the prior art are substantially reduced. Moreover, the portion using magnetic current in the subslot is successfully improved, thereby increasing the antenna area substantially involved in the radiation phenomenon. Accordingly, according to the present invention, there is provided a planar small antenna capable of operating at an improved bandwidth without affecting radiation patterns, radiation efficiency, polarity purity, and the like.

In order to compare the resulting characteristics of the antenna according to the invention with the conventional antenna, both antennas are designed with the same size standard in UHF. That is, the size of the metal layer 30 is 0.21λ ₀ × 0.15λ ₀ , and the size of the slot is 0.17λ ₀ × 0.08λ ₀ . Here, λ ₀ refers to a wavelength in free space. The dielectric substrate 20 is preferably selected from materials having a low dielectric constant of about 2.2.

The feeding of the antenna is realized through an open-ended microstrip line or other type of transmission line in which a probe is installed on the back surface of the dielectric substrate as in the prior art.

7 is a view showing a radiation pattern of the E plane and the H plane in the conventional antenna, Figure 8 is a view showing a radiation pattern of the E plane and H plane in the antenna according to the present invention. Referring to Figures 7 and 8, it is observed that the omnidirectional patterns of both antennas are nearly identical. The gain of this planar small antenna is -1.9 dBi, and the gain of the conventional antenna is -1.8 dBi. Therefore, in terms of gain and efficiency, the advantage of the present antenna is weak.

9 is a graph comparing bandwidth characteristics through reflection coefficients between an antenna according to the present invention and a conventional antenna. In FIG. 9, the portion indicated by the dotted line represents the reflection loss characteristic of the conventional antenna, and the portion indicated by the solid line represents the reflection loss characteristic of the present antenna.

At a return loss level of -10 dB, the operating bandwidth of the present antenna is 38 MHz, whereas the operating bandwidth of a conventional antenna is only 29 MHz. Therefore, without being affected by radiation patterns, radiation efficiency, polarity purity, etc., the bandwidth of the antenna is about 30 percent wider than that of the conventional antenna.

10 is a view showing a rectenna according to an embodiment of the present invention. Referring to FIG. 10, the rectenna 1000 includes a rectifier circuit and an antenna 1100 embedded in a semiconductor chip 1010 of a transponder.

FIG. 11 is a diagram illustrating the antenna of FIG. 10 separated from each other. The electrically small antenna 1100 includes a dielectric substrate 1110, a thin metal layer 1120 formed on an upper surface of the dielectric substrate 1110, and slot patterns inside the metal layer 1120. The metal layer 1120 having the slot pattern becomes a radiating part of the antenna 1100.

The slot pattern includes a plurality of sub slots 1140a, 1140b, 1150a, 1150b, 1160a, 1160b, 1170a, 1170b, 1180a, and 1180b connected to one end of the main slot 1130 and the main slot. The first transverse slot pattern 1180a is formed to be perpendicular to the main slot 1130, and the second transverse slot pattern 1180b is formed to be perpendicular to the main slot 1130 below the main slot 1130. The transverse slot patterns 1180a and 1180b are symmetrically divided by the main slot 1130. At the feed point 1190, the antenna 1100 is fed into the slot pattern through the inlet of the semiconductor chip.

Since the overall required size of the antenna is substantially less than half wavelength, the length of the main slot will be shorter and shorter. Therefore, in order to reduce the size of the antenna, a specific limit voltage value must be applied at both ends of the main slot. This produces the desired resonant electromagnetic field distribution on the shortened main slot. In order to provide the desired voltage discontinuity across the main slot, the plurality of sub slots must have inductive characteristics.

Unlike the conventional structure, the slot pattern includes four sub slots terminated at both ends of the main slot 1130. Each of the sub slots 1140a, 1140b, 1150a, 1150b, 1160a, 1160b, 1170a, 1170b, 1180a, and 1180b forms a pair around the main slot 1130 and is connected to one end of the main slot 1130. Each of the sub slots 1140a, 1140b, 1150a, 1150b, 1160a, 1160b, 1170a, 1170b, 1180a, and 1180b has a curved shape in a clockwise or counterclockwise shape. Each of the sub slots 1140a, 1140b, 1150a, 1150b, 1160a, 1160b, 1170a, 1170b, 1180a, and 1180b has a symmetrical shape with respect to the main slot 1130.

That is, the right first subslot 1140a and the right third subslot 1160a have a bent clockwise direction, and the right second subslot 1150a and the right fourth subslot 11700a are counterclockwise. It has a curved shape.

In addition, the left side subslots 1140b, 1150b, 1160b, and 1170b, which are paired with the right side subslots 1140a, 1150a, 1160a, and 1170a, have left and right subslots 1140a, 1150a, 1160a, and 1170a. Since the shape is symmetrical, the line direction is opposite to the line direction of the right subslots 1140a, 1150a, 1160a, and 1170a.

That is, the left first subslot 1140b and the left third subslot 1160b have a counterclockwise line shape, and the left second subslot 1150b and the left fourth subslot 1170b are clockwise. It has a line shape. As described above, the sub-slots 1140a, 1140b, 1150a, 1150b, 1160a, 1160b, 1170a, 1170b, 1180a, 1180b for clock and counterclockwise echoing do not affect the radiation pattern, efficiency, polarity purity, etc. of the antenna. It provides unique electromagnetic characteristics to operate at increased bandwidths.

Further, additional cross slot patterns 1180a and 1180b are formed to provide specific inductive properties of the antenna appearing at feed point 1190. The transverse slot patterns 1180a and 1180b in accordance with an embodiment of the present invention induce electromagnetic fields near the antenna 1100 in a unique manner. The configuration of the transverse slot patterns 1180a and 1180b provides the antenna with the required ratio of reactance to resistance in the antenna's impedance. At the same time, the cross slot patterns 1180a and 1180b allow the antenna to maintain improved radar cross section characteristics.

Radiation phenomena, along with losses in the metals and dielectrics that make up the antenna, induce a resistive component of the antenna impedance. The reactance component of the antenna impedance represents the power stored around the field of the antenna. The transverse slot patterns formed along the main slot disturb the electromagnetic field around the antenna. However, since the main slot divides the cross slot pattern into the first cross slot pattern 1180a and the second cross slot pattern 1180b, the fields radiated from the cross slot pattern of any one of the divided cross slot patterns are separated from each other. Canceled by radiated fields in the transverse slot pattern. The unique change in the field distribution near the antenna substantially affects the complex impedance of the antenna. This results in a desired ratio of resistance to reactance of the antenna by including a rectenna's radiation pattern and a recurring slot pattern that does not affect polarization purity.

An example of a UHF electrical compact rectenna for a passive RFID transponder has been designed and constructed in accordance with the present invention. In this embodiment, the antenna has a size of 7 cm x 5 cm. This size corresponds to 0.21λ ₀ × 0.15λ _0, where, λ ₀ is a wavelength having a center frequency of 912MHz in the free space.

12 is a diagram illustrating the return loss of an antenna induced by a specific impedance of an actual semiconductor chip. The complex impedance of the transponder semiconductor chip is assumed to have a value of 34.5-j815. Referring to FIG. 12, the bandwidth of the antenna at the return loss level of −10 dB is 10 MHz (1.1%). This increased operating bandwidth can be fully applied to the actual RFID system. The radiation efficiency of the simulated antenna is 75 percent, and both metal and dielectric losses must be considered. The radiation pattern is omni-directional. The polarity is linearly proportional to the negligible level of cross polarization. In the case of common polarity (co-polarized) incident wave with a common, at 912 MHz radar reflection region it is reached 6.5cm to 38.4cm ² in ^2, short circuit termination in the conjugate matching.

By varying the number, length, width, spacing, etc. of the transverse slots, the desired ratio of reactance to resistance can be obtained.

The Radar Cross Section (RCS) is a measure of how well an object can reflect electromagnetic waves. At a given wavelength and polarity, the radar reflecting region varies with a range of design parameters such as the size, shape, material, and surface structure of the object. For example, metal surfaces are more reflective than dielectric materials.

In the case of a planar antenna as a scatterer object, if the other conditions are the same, the more the metal occupies the area, the more radar reflection area the antenna has. Thus, when compared with a typical conventional antenna having a shape such as a narrow metal strip pattern, the proposed rectenna possesses an improved radar reflecting area under the same size constraints.

As a result, the preferred embodiment of the present invention includes an electric miniature antenna conjugated with the semiconductor chip of the transponder and can be improved radar capable of operating at increased bandwidth without affecting radiation pattern, efficiency and polarity purity. It provides a rectenna having a reflective area.

As described above, according to the planar small antenna according to the present invention, the antenna area substantially involved in the radiation phenomenon is increased, so that the advantage of having an improved bandwidth without affecting radiation patterns, efficiency, polarity purity, etc. have.

In addition, according to the small lentenna according to the present invention, it is provided with an electrically small antenna conjugated with the semiconductor chip of the transponder, and can operate at increased bandwidth without affecting the radiation pattern, efficiency, polarity purity There is an advantage with improved radar reflecting area.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (24)

Dielectric substrates; A metal layer formed on the dielectric substrate; One main slot patterned in the metal layer; And a plurality of sub slots connected to one end of the main slot and connected in a predetermined direction. And the plurality of sub-slots form a pair of left-right symmetry with respect to the main slot. The method of claim 1, wherein the predetermined direction is Planar miniature antenna, characterized in that any one of the clockwise and counterclockwise direction. The method of claim 1, A plurality of sub slots each forming a pair around the main slot, Planar compact antenna, characterized in that the line direction is opposite to each other. The length of the circuit arm of the sub slot, And a planar small antenna, characterized in that less than a quarter wavelength at an operating frequency of the antenna. The method of claim 1, wherein the plurality of sub slots, A right first sub-slot connected in a clockwise direction from the upper right end of the main slot, a right second sub-slot connected in a direction opposite to the right first sub-slot from inside the right first sub-slot, and the main slot A right fourth subslot which is connected in a direction opposite to the right first subslot at a lower right end of the right side, and a right third subslot which is connected in the opposite direction to the right fourth subslot from inside the right fourth subslot. Planar miniature antenna comprising a. The method of claim 5, A pair of symmetrical pairs with each of the right first through fourth subslots and a left first through fourth subslot connected in a direction opposite to each of the right first through fourth subslots are further formed around the main slot. Planar miniature antenna comprising a. The method of claim 5, The length of the circuit arm of the right first subslot and the right fourth subslot is, And a planar miniature antenna which is larger than a length of the line arms of the right second sub slot and the right third sub slot. The method of claim 1, wherein the length of the main slot, And a planar compact antenna, characterized in that less than half wavelength at an operating frequency of the antenna. The method of claim 1, And a width of the sub slot and a width of the main slot are the same. The method of claim 1, And the width of the sub slot is narrower than the width of the main slot. The method of claim 1, And the width of the sub slot is wider than the width of the main slot. The method of claim 1. And a feed line having a microstripline composed of a terminal open-ended capacitive probe on a back surface of the dielectric substrate.  The method of claim 12, And the width of the probe is equal to the strip width of the microstripline.  The method of claim 12, The flat antenna is characterized in that the width of the probe is smaller than the strip width of the microstrip line  The method of claim 12,  And the width of the probe is larger than the strip width of the microstripline. Dielectric substrates; A metal layer formed on the dielectric substrate; One main slot patterned in the metal layer; A plurality of sub slots connected to one end of the main slot and connected in a predetermined direction; A plurality of first crossing slots formed perpendicularly to the main slots above the main slots and a plurality of second crossing slots formed perpendicularly to the main slots below the main slots; And Small inlet comprises a; inlet of the semiconductor chip formed in the main slot. The method of claim 16, The main slot, the plurality of sub slots and the plurality of first and second transverse slots, And a small rectenna to perform conjugated impedance matching with the small rectenna without an external matching element, such that the small rectenna has an improved radar reflecting area in the operating bandwidth of the transponder. The method of claim 16, wherein the plurality of first and second transverse slots, Small rectenna characterized in that divided by the main slot symmetrically. The method of claim 16, wherein the predetermined direction, The compact rectenna, characterized in that the direction of any one of clockwise and counterclockwise. The method of claim 16, A plurality of sub slots each forming a pair around the main slot, Small rectenna, characterized in that the line direction is opposite to each other. The method of claim 16, wherein the plurality of sub slots, A right first sub-slot connected in a clockwise direction from the upper right end of the main slot, a right second sub-slot connected in a direction opposite to the right first sub-slot from inside the right first sub-slot, and the main slot A right fourth subslot which is connected in a direction opposite to the right first subslot at a lower right end of the right side, and a right third subslot which is connected in the opposite direction to the right fourth subslot from inside the right fourth subslot. Compact rectenna, characterized in that it comprises. The method of claim 21, A pair of symmetrical pairs with each of the right first through fourth subslots, the left first through fourth subslots connected in a direction opposite to each of the right first through fourth subslots; Planar compact rectenna, characterized in that it further comprises. The method of claim 16, wherein the dielectric substrate and the metal layer, A small rectenna characterized by being flat. The method of claim 1, wherein the semiconductor chip, Small rectifier further comprising a rectifier circuit.

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