WO2011159037A2 - Broadband antenna using metamaterials, and communication device including same - Google Patents

Abstract

Disclosed are a broadband antenna using metamaterials and a communication device including same. The broadband antenna using metamaterials according to an embodiment of the present invention comprises: a radiating patch which is a transmission line having right-handed (RH) characteristics in a composite right/left handed transmission line (CRLH-TL) structure, and is particularly patterned according to a resonating frequency to act as a radiating element of the antenna; a feed line connected to one end of the radiating path for supplying power to the radiating patch; a ground line connected to the other end of the radiating path for grounding the radiating patch; and a ferritic helical loading unit which is formed on the ground line and acts as a first parallel inductor having left-handed (LH) characteristics in the CRLH-TL structure. Therefore, the bandwidth of the metamaterial antenna can be extended.

Description

Broadband Antenna Using Metamaterial and Communication Device Comprising the Same

Embodiments of the present invention relate to an antenna and a communication device technology including the same that can extend the bandwidth of an antenna using a metamaterial.

With the advance of the electronics industry, communication technologies, in particular, wireless communication technologies have been developed, and various wireless communication terminals capable of performing voice and data communication with anyone, anytime, anywhere, have been developed and are becoming common.

In addition, in order to improve the portability of the wireless communication terminal, various technologies for miniaturizing the wireless communication terminal, for example, the development of a high density integrated circuit device and the miniaturization method of the electronic circuit board have been studied. As the purpose is also diversified, terminals for performing various functions such as navigation terminals and terminals for the Internet are being developed.

Meanwhile, one of the important technologies in the wireless communication technology is an antenna technology, and antennas by various techniques such as a coaxial antenna, a rod antenna, a loop antenna, a beam antenna, and a super gain antenna are currently used.

In particular, with the recent trend toward more portable or miniaturized wireless communication terminals, the technical necessity for miniaturizing antennas is increasing. Accordingly, the conductors of the antennas are in the form of helix or meander line. An antenna constructed is proposed.

However, the proposed antenna does not deviate from the limit of size depending on the resonant frequency, and the smaller the size of the antenna, the more complicated the shape is to form an antenna of fixed length in a narrow space.

In order to solve this problem, the proposed technique is an antenna technology using metamaterial. Here, the metamaterial refers to a material or an electromagnetic structure that is artificially designed to have special electromagnetic properties that are not generally found in nature. When the material of the metamaterial is applied to an antenna, the metamaterial has an advantageous property for miniaturization of the antenna size. .

Metamaterials applied to antennas are typical of the CRLH-TL (Composite Right / Left Handed Transmission Line) structure, which uses double negative (DNG), epsilon negative (ENG) and mu negative (Mu negative). (MNG) zero-order resonator (ZOR) antenna can be implemented.

However, there has been a problem that an antenna using such a metamaterial characteristic is typically a narrow bandwidth. Accordingly, various researches are being conducted to expand the bandwidth of an antenna using metamaterials.

Embodiments of the present invention to provide a technique that can extend the bandwidth of the CRLH-TL zero-order resonator antenna having the characteristics of the metamaterial.

Other technical problems by the embodiments of the present invention can be understood by the following description, which can be realized by the means and combinations thereof shown in the claims.

A broadband antenna using a metamaterial according to an embodiment of the present invention is a transmission line having RH (Right-Handed) characteristics in a CRLH-TL (Composite Right / Left Handed Transmission Line) structure, and has a specific pattern according to a resonance frequency. A radiation patch implemented to act as an antenna radiator; A power supply line connected to one end of the radiation patch to supply power to the radiation patch; A ground line connected to the other end of the radiation patch to ground the radiation patch to ground; And a ferrite helical loading unit formed on the ground line and serving as a first parallel inductor exhibiting left-handed (LH) characteristics in a CRLH-TL structure.

The ferrite helical loading unit, three-dimensional ferrite core; And a helical line wound in a helical shape at a predetermined interval on the ferrite core surface.

The ferrite material of the ferrite helical loading portion is composed of one or more materials selected from the group consisting of a magnetic metal and an amorphous magnetic material, or based on Fe, and in addition to Fe, Ni, Mn, Co, Mg, Zn, Ba, and Sr It may be composed of a magnetic oxide further comprising one or more elements selected from the group consisting of.

In addition, the ferrite material of the ferrite helical loading unit may be made of a Co ₂ Y hexagonal ferrite (Co ₂ Y hexagonal ferrite) (Ba ₂ Co ₁ Zn _0.7 Cu _0.3 Fe ₁₂ O ₂₂ ) material.

Furthermore, the broadband antenna using the metamaterial may further include an inductor formed between the radiation patch and the feed line to serve as a second parallel inductor having left-handed (LH) characteristics in a CRLH-TL structure. have.

In addition, the radiation patch, a portion of the radiation patch may be spaced apart a predetermined interval to serve as a series capacitor showing the Left-Handed (LH) characteristics in the CRLH-TL structure.

According to embodiments of the present invention, the characteristics of bandwidth extension can be obtained by applying a ferrite helical loading portion to a portion corresponding to parallel inductance at the end of the CRLH-TL antenna having the characteristics of the metamaterial.

1 is an equivalent of each of (a) a double negative (DNG) unit cell and (b) an Epsilon negative (ENG) unit cell in a CRLH-TL structure having metamaterial properties according to an embodiment of the present invention. It is a circuit diagram.

FIG. 2 is a diagram illustrating the overall configuration of an ENG unit cell antenna according to the equivalent circuit diagram of FIG. 1B according to one embodiment of the present invention.

3 illustrates an actual implementation of the ENG unit cell antenna of FIG. 2 in accordance with an embodiment of the present invention.

4 is a graph illustrating a return loss S11 measured with respect to the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention.

5 to 7 illustrate radiation patterns of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention with respect to the x-y plane, the x-z plane, and the y-z plane, respectively.

8 illustrates the radiation efficiency and the maximum gain of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention.

9 is a graph comparing the radiation efficiency of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. However, this is only an exemplary embodiment and the present invention is not limited thereto.

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 subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification. The technical spirit of the present invention is determined by the claims, and the following embodiments are merely means for effectively explaining the technical spirit of the present invention to those skilled in the art to which the present invention pertains. Particular shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

Equivalent circuit diagram of CRLH-TL structure with metamaterial characteristics

1 is an equivalent of each of (a) a double negative (DNG) unit cell and (b) an Epsilon negative (ENG) unit cell in a CRLH-TL structure having metamaterial properties according to an embodiment of the present invention. It is a circuit diagram.

First, metamaterial means a material or an electromagnetic structure that is artificially designed to have special electromagnetic properties that are not generally found in nature, and are generally referred to in the art and referred to as metamaterials in the present specification. Means a material or such electromagnetic structure that has a negative permittivity or permeability.

Such materials (or structures) are also called double negative (DGN) materials in the sense of having two negative parameters. In addition, metamaterials have a negative reflection coefficient due to their negative dielectric constant and permeability, and thus are also called NRI (Negative Refractive Index) materials. Metamaterial was first studied by Soviet physicist V.Veselago in 1967, but more than 30 years later, a concrete implementation method has been studied and application has been attempted.

Due to these characteristics, electromagnetic waves in metamaterials are transmitted by the left-hand rule rather than following Fleming's right-hand rule. That is, the phase propagation direction (phase velocity direction) and the energy propagation direction (group velocity direction) of the electromagnetic wave are reversed, and the signal passing through the metamaterial has a negative phase delay. Accordingly, metamaterials are sometimes referred to as left-handed materials (LHMs). In addition, the relationship between β (phase constant) and ω (frequency) is not linear in the metamaterial, and the characteristic curve is also present in the left half of the coordinate plane. Due to such nonlinear characteristics, the metamaterial has a small phase difference according to frequency, so that a wideband circuit can be realized. Since the phase change is not proportional to the length of the transmission line, a small circuit can be realized.

FIG. 1A is an equivalent circuit diagram of a unit cell of a double negative (DNG) CRLH-TL structure. The DNG unit cell of FIG. 1 (a) has two series impedances (C _L ) and two parallel inductors exhibiting two characteristic impedances (Z ₀ ) and left-handed (LH) characteristics. (2L _L ) can be equivalent. Here, two characteristic impedances Z ₀ may be represented by parallel capacitors and series inductor components, respectively, as transmission lines having a general RH structure.

FIG. 1B is an equivalent circuit diagram of a unit cell of an epsilon negative CRLH-TL structure. The ENG unit cell of FIG. 1 (b) may be equivalent to include one characteristic impedance Z ₀ representing the RH characteristic and two parallel inductors 2L _L representing the LH characteristic. Here, the characteristic impedance Z ₀ is a transmission line having a general RH structure and may be represented by a parallel capacitor and a series inductor component.

In particular, in the case of the antenna to which the ENG unit cell is applied, since the parallel capacitor C _R corresponding to the characteristic impedance Z ₀ having the RH characteristic has a fixed value, the two parallel inductors 2L _L having the LH characteristic have a fixed value. By adjusting the value, the resonant frequency control and bandwidth may be extended.

Hereinafter, an ENG unit cell antenna designed according to the equivalent circuit diagram of FIG. 1 (b) will be described in detail as an embodiment of the present invention.

Configuration of the ENG Unit Cell Antenna

FIG. 2 is a diagram illustrating the overall configuration of an ENG unit cell antenna according to the equivalent circuit diagram of FIG. 1B according to one embodiment of the present invention. Here, the ENG unit cell may be applied as a zero order resonator (ZOR) using metamaterials.

2, an ENG unit cell antenna 200 according to an embodiment of the present invention may include a radiation patch 210, a feed line 220, a ground line 230, an inductor 240, and a ferrite helical loading unit 250. It is configured to include).

The radiation patch 210 is a transmission line having a right-handed (RH) characteristic on a substrate, and is implemented as a specific pattern according to a resonance frequency to serve as an antenna radiator. In addition, the radiation patch 210 may be formed on a three-dimensional carrier, not on a substrate. The substrate or carrier may be a material having a predetermined permittivity (ρ), a predetermined permeability (μ), or both a predetermined permittivity and permeability. For example, FR4 (Flame Retardant Type4) having a dielectric constant of about 4.5 may be a substrate or carrier. It may be used as, but not limited to, various dielectric materials or magnetic materials may be used. The radiation patch 210 corresponds to a characteristic impedance Z ₀ of FIG. 1B as a transmission line showing general RH characteristics, and may be represented by a series inductor L _R and a parallel capacitor C _R. In detail, the series inductor L _R may be an inductance value formed in the longitudinal direction of the radiation patch 210, and the parallel capacitor C _R may be equivalent to a capacitance component generated between the radiation patch and the ground.

The feed line 220 is connected to one end of the radiation patch 210 to supply power to the radiation patch 210 to function as an antenna radiator.

The ground line 230 is connected to the other end of the radiation patch 210 serves to ground the radiation patch 210 to the ground.

An inductor 240 is formed between the radiation patch 210 and the feed line 220 so that the ENG unit cell antenna 200 exhibits LH characteristics. The first parallel inductor 2L _{L of} FIG. Plays a role.

A ferrite helical loading unit 250 is formed on a ground line 230 connected between the radiation patch 210 and the ground so that the ENG unit cell antenna 200 exhibits LH characteristics. It serves as the second parallel inductor 2L _L of b). The ferrite helical loading unit 250 may be formed such that a line is wound in a helical shape on a rectangular ferrite core. The shape of the ferrite core is not only a rectangular column, but also a variety of shapes such as a cylinder, a cube, and the like, but is not limited to any particular shape. Here, the ferrite may not only use a Co ₂ Y hexagonal ferrite (Co ₂ Y hexagonal ferrite (Ba ₂ Co ₁ Zn _0.7 Cu _0.3 Fe ₁₂ O ₂₂ )) material as an experimental example as shown in FIG. The materials representing are all possible and may be made of one or more materials selected from the group consisting of ferrite, magnetic metal and amorphous magnetic material. In addition, the ferrite material includes Fe as a base, and may be made of a magnetic oxide further comprising at least one element selected from the group consisting of Ni, Mn, Co, Mg, Zn, Ba, and Sr in addition to Fe. However, the ferrite material is not limited thereto, and various other materials may be used.

In the case of the ENG unit cell antenna 200 according to the embodiment of the present invention having such a configuration, since the radiation patch 210, the power supply line 220 and the ground line 230 is fixed to the above using the material properties By adjusting the values of the inductor 240 and the ferrite helical loading unit 250, it is possible to adjust the resonant frequency to implement a miniaturized antenna that does not depend on the length d of the entire antenna.

In addition, the use of a ferrite material can exhibit a high inductance value even with a small number of turns of the helical line, further miniaturizing the antenna.

In addition, according to an embodiment of the present invention, by forming a ferrite helical loading portion 250 wound on a ferrite core in a helical shape on the ground line 230, the ENG unit having a narrow bandwidth has been a problem in the prior art The bandwidth of the cell antenna 200 can be extended. This will be demonstrated by various measurements such as bandwidth, described below.

In FIG. 2, the antenna is configured according to the ENG unit cell equivalent circuit of FIG. 1 (b) as an embodiment. However, the present invention is not limited to the ENG unit cell antenna. The antenna may be configured according to the DNG unit cell equivalent circuit or the MNG unit cell equivalent circuit as shown in a). If the antenna is implemented according to the DNG unit cell equivalent circuit, a portion of the radiation patch 210 of FIG. 2 may be spaced apart to represent the series capacitor C _L. In this case, the resonant frequency may be adjusted by adjusting the spacing of the separation space that functions as the series capacitor C _L as well as the adjustment of the parallel inductor 2L _L.

Actual antenna implementation and return loss (S11) comparison graph

3 illustrates an actual implementation of the ENG unit cell antenna of FIG. 2 in accordance with an embodiment of the present invention.

Referring to Figure 3, the antenna is fabricated on the FR4 substrate, the substrate size is 50mm x 100mm x 0.8mm, the ground portion is 50mm x 90mm. The SMT chip inductor used as the parallel inductor 240 has a value of 27nH. The ferrite helical loading unit 250 is a Co2 Y hexagonal ferrite core (Co ₂ Y hexagonal ferrite (Ba ₂ Co ₁ Zn _0.7 Cu _0.3 Fe ₁₂ O ₂₂ ) core) was formed of a rectangular column of 3mm × 6mm × 3mm size, A 0.5 mm thick helical line is wound 0.5 mm apart on top of the ferrite core and is 60 mm long. Specific implementation sizes of the other components are shown in detail in FIG. 2, and description thereof will be omitted. In addition, the reference numerals for the respective components are the same as those in FIG. 2, and thus the display is omitted for simplicity of the drawings.

4 is a graph illustrating a return loss S11 measured with respect to the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention. In the graph of FIG. 4, an antenna having a ceramic helical loading unit is compared to determine the characteristics of the antenna according to an exemplary embodiment of the present invention having a ferrite helical loading unit, and a curve indicated by a vacant circle (○) is an antenna having a ceramic helical loading unit. The curve indicated by the filled circle (●) represents the actual measurement result of the antenna having a ferrite helical loading unit according to an embodiment of the present invention.

Referring to FIG. 4, an antenna having a ferrite helical loading unit according to an embodiment of the present invention has a resonance frequency at about 0.8 GHz, and a bandwidth (6 dB return loss) has 140 MHz (740 to 880 MHz). This corresponds to about 17.5% at resonance frequency. On the other hand, the antenna with ceramic helical loading has a resonant frequency at about 0.8 GHz, and the bandwidth (6 dB return loss) has 90 MHz (760-850 MHz). This corresponds to about 11.2% at resonance frequency.

It can be seen that the antenna having the ferrite helical loading part according to the measured return loss (S11) has an increased bandwidth compared to the antenna having the ceramic helical loading part according to the embodiment of the present invention.

Radiation pattern measurement result

5 to 7 illustrate radiation patterns of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention with respect to the x-y plane, the x-z plane, and the y-z plane, respectively.

5 to 7, it can be seen that the antenna according to the embodiment of the present invention exhibits a radiation pattern having an omnidirectional direction. Therefore, the antenna according to the embodiment of the present invention is sufficient to be applied to the mobile terminal.

Antenna Radiation Efficiency and Gain

8 illustrates the radiation efficiency and the maximum gain of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention.

Referring to Figure 8, the radiation efficiency of the antenna according to an embodiment of the present invention is 29.6% ~ 39.3%, the gain has a -1.04dBi ~ 0.18 dBi, the maximum radiation efficiency and the maximum gain is 38.5 at 0.8GHz resonant frequency % And 0.05 dBi.

9 is a graph comparing the radiation efficiency of the ENG unit cell antenna of FIG. 3 according to an embodiment of the present invention.

In the graph of FIG. 9, an antenna having a ceramic helical loading unit was compared to identify an antenna according to an embodiment of the present invention having a ferrite helical loading unit, and a curve indicated by a vacant circle (○) is an antenna having a ceramic helical loading unit. The curve indicated by the filled circle (●) represents the actual measurement result of the antenna having a ferrite helical loading unit according to an embodiment of the present invention.

Referring to FIG. 9, it can be seen that an antenna having a ferrite helical loading unit according to an embodiment of the present invention has improved radiation efficiency at a wider bandwidth than an antenna having a ceramic helical loading unit.

As described above, as a result of examining the measurement graph in FIGS. 4 to 9, it can be seen that the broadband characteristics are exhibited through the metamaterial antenna having the ferrite helical loading unit according to the embodiment of the present invention.

As described above, the metamaterial antenna according to the embodiment of the present invention is a method of arranging unit cells, the number of unit cells, the size of the radiation patch, the permittivity and size of the substrate, the size of the ferrite helical loading unit, the permittivity and permeability of the ferrite used, the helical line By adjusting the width and spacing of the feeder, the shape of the feeder (the position of the feeder, the width of the feeder, the length of the feeder), and the type of grounding (the position of the grounding line, the width of the grounding line, the length of the grounding line) Will be able to adjust the characteristics of the desired wideband antenna.

Although the present invention has been described in detail with reference to exemplary embodiments above, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. Will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

Claims (8)

1. A radiation line having a right-handed (RH) characteristic in a composite right / left handed transmission line (CRLH-TL) structure, the radiation patch being implemented in a specific pattern according to a resonance frequency to serve as an antenna radiator;

   A power supply line connected to one end of the radiation patch to supply power to the radiation patch;

   A ground line connected to the other end of the radiation patch to ground the radiation patch to ground; And

   And a ferrite helical loading unit formed on the ground line and serving as a first parallel inductor exhibiting left-handed (LH) characteristics in a CRLH-TL structure.
2. The method of claim 1,

   The ferrite helical loading unit,

   Three-dimensional ferrite core; And

   And a helical line wound in a helical shape at a predetermined interval on the surface of the ferrite core.
3. The method of claim 1,

   Ferrite material of the ferrite helical loading portion,

   A wideband antenna using metamaterials, consisting of one or more materials selected from the group consisting of magnetic metals and amorphous magnetic materials.
4. The method of claim 1,

   Ferrite material of the ferrite helical loading portion,

   A broadband antenna using a metamaterial including Fe as a base and comprising a magnetic oxide further comprising at least one element selected from the group consisting of Ni, Mn, Co, Mg, Zn, Ba, and Sr in addition to Fe.
5. The method of claim 1,

   Ferrite material of the ferrite helical loading portion,

   A broadband antenna using a metamaterial composed of a Co ₂ Y hexagonal ferrite (Ba ₂ Co ₁ Zn _0.7 Cu _0.3 Fe ₁₂ O ₂₂ ) material.
6. The method of claim 1,

   And a inductor formed between the radiation patch and the feed line to serve as a second parallel inductor exhibiting left-handed (LH) characteristics in a CRLH-TL structure.
7. The method of claim 1,

   The radiation patch,

   In the CRLH-TL structure, a part of the radiation patch is spaced apart by a certain distance so as to act as a series capacitor exhibiting the Left-Handed (LH) characteristics, broadband antenna using a metamaterial.
8. A communication apparatus comprising a wideband antenna using the metamaterial according to any one of claims 1 to 7.

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