Se-gyoon Mok

A wide band metamaterial ZOR antenna of a patch coupled to a ring mushroom

We present a new low-profile composite right- and left-handed metamaterial zeroth order resonance (ZOR) antenna of the simulated and measured fractional bandwidth 30 and 57%, respectively, for a center frequency 2.5 GHz and gain over 3 dBi, while other ZOR antennas have narrow bandwidths much less than 10% with low antenna gain below or around 0 dBi. The proposed antenna shows the monopolar radiation pattern over the entire band. The design approach is verified by the circuit and 3D EM simulations, and measurement.

A novel metamaterial CRLH ZOR circular patch antenna capacitively coupled to a circular ring

In this paper, a novel circular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Composite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a ordinary microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding circular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low-cost low-profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

Design of the Open- Loop Combined Meandered- Line 1 - Layer Radiator for Diversity Antennas with Size- Reduction and Improved Isolation

Abstract - This paper proposes a new diversity antenna which is the base of MIMO, tunable and reconfigurable antennas. The antenna has a small size and high inter-antenna isolation resulting from the compact radiating element comprising a meandered line and an open-loop combined in one limited uniplanar space and a modified T-shaped decoupling structure, respectively. In a WiMAX band, the radiating element and the entire antenna are  and  in size, which shows effective size-reduction and the gain and efficiency of the proposed antenna attached to the ground of a handheld device are 3.7dBi and 56% acceptable to the industrial standardKey Words : Diversity antenna, Antenna size-reduction, Isolation*준 회 원 : 인천대학교 정보통신공학과 석사과정**정 회 원 : 인천공업전문대학 전기정보과 조교수†교신저자, 정회원 : 인천대학교 정보통신공학과 교수E-mail : s-kahng@incheon.ac.kr접수일자 : 2011년 12월 16일 최종완료 : 2011년 12월 26일 1. 서 론 무선통신과 휴대용 단말기에 대한 필요성과 활용도가 날로 커져가는 가운데, 기술 발전에 대한 사용자의 요구가 증가하고 있다. 한 기기에서 여러 가지 서비스를 제공해야하는 스마트 기기들이 대거 출시되면서 소비자들은 더 작고 성능이 좋은 것을 추구하게 되었다. 이러한 추세는 휴대용 기기 뿐 아니라, 휴대용기기를 사용하기 위한 통신환경을 제공하는 기기들도 마찬가지이다. 특히 큰 출력이 필요 없는 가정용 중계기 같은 경우는 원활한 통신이 가능하면서 크기가 작고, 외관상으로도 보기 좋고, 공간적으로도 절약이 되는 형태가 각광받고 있다. 따라서 중계기용으로 사용되는 안테나의 경우도 그 크기가 작아져야 한다. 그런데 중계기의 경우는 하나의 안테나만을 사용하지 않고 다수의 안테나를 사용해서, 송수신율을 높이게 된다. 이것이 다이버시티 안테나(Diversity Antenna) 사용목적이다. 하지만 다중 안테나를 사용하기위해서는 안테나 간 거리가 반파장 이상 되어야만 만족할만한 격리도를 얻을 수 있기 때문에 안테나만을 소형화해서는 전체적인 소형화를 이룰 수 없다. 이에 따라 다수의 안테나 사이에서 높은 격리도를 갖는, 소형 구조는 활발히 연구되고 있다. Murch는 격리도 확보를 위해 하나의 안테나에서 다른 안테나로 넘어오는 근역장(near field)를 제어하는 구조를 가지는 안테나를 소개하고 있다[1, 2]. 안테나의 방사패턴과 격리도는 향상되었으나 크기에 있어서는 방사체와 격리도 구조가 단말기 접지의 상층부와 양 측면을 사용하여 소형화되지는 않았다. K. Payandehjoo는 두 안테나 사이의 커플링을 억제를 통한 Diversity 이득향상을 위해 EBG 구조를 사용하였다[3]. 그러나 크기는 시장 표준을 초과하는 것을 알 수 있다. X. Wang은 두 개의 Microstrip 급전 안테나를 단말기 크기에 맞도록 방사체를 수직으로 접어 층을 이루는 구조를 소개하였다. 또한 격리도 개선을 위해 미앤더 결합제거 구조를 설계하였다[4]. 이를 통해 12dB 이상의 격리도를 확보하였지만 안테나의 전체적인 체적은 증가하고 이종 안테나의 결합의 모양을 띄게 되었다. 이들을 통해, 산업적 요구에 부합하는 안테나의 성능을 가지면서 결합제거가 포함된 전체구조의 소형화가 절실함을 알 수 있다. 따라서 본 논문에서는 위상차를 이용한 결합제거구조를 삽입하여 안테나의 거리를 최소화 하면서도 격리도를 크게 향상시키는 것을 목표로 하였다. 안테나의 경우는 소형화를 위하여 급전이 되는 부분분에 접지를 시키고 미앤더 라인으로 길게 꺾어서 설계하여 전류 경로를 길어지게 하는 효과를 얻어 작게 설계를 하였다. 이렇게 설계된 안테나를 가깝게 위치시킨 뒤 결합제거구조를 삽입하여 그 격리도를 모의실험 결과를 기준으로 9dB에서 20dB로 향상시켰다. 또한 측정치에서도 17dB이상으로 높은 격리도를 가지는 특성을 확인하였다.

A novel metamaterial CRLH ZOR microstrip patch antenna capacitively coupled to a rectangular ring

In this paper, a novel rectangular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Complosite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a standard microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding rectangular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

Widened bandwidth of a metamaterial ZOR patch antenna with a short-circuited ring

In this paper, we present a new low-profile composite right and left-handedness(CRLH) metamaterial zeroth order resonance(ZOR) antenna which originally has the bandwidth of 80MHz and is treated further to have 1428 MHz as an improved bandwidth for center frequency 2.5GHz as the ZOR frequency, by merging the −1st, zeroth, and +lst resonance modes to the ZOR. We have experienced nearly 50% fractional bandwidth(FBW) and the monopolar radiation patterns are maintained in the entire band, which outdoes other ZOR antennas [1–5] suffering from FBW far less than 10%. This design method is verified by 3D EM simulations and measurement.

A metamaterial-inspired handset antenna with the SAR reduction

A method to reduce the specific absorption rate(SAR) of the antenna for WiMAX mobile communication is proposed in this paper. The SAR reduction is achieved by miniaturizing the physical size of the antenna for the given resonance frequency by devising a metamaterial-inspired radiator much smaller than the quarter-guided wavelength appearing in the conventional planar inverted F antenna(PIFA) or modified monopole antenna. The proposed antenna is placed near the head-phantom and its SAR is evaluated by the full-wave simulations(SEMCAD X), where the metamaterial-inspired antenna is shown to have the lower value than a modified monopole as the reference in terms of the SAR.

Compact MIMO antenna of the open-loop and meandered-line 1-layer radiators with improved isolation

We propose a compact MIMO antenna with high inter-antenna isolation. It is featured by small radiating elements each of which comprises a meandered line and an open-loop, and a modified T-shaped decoupling structure to lower the interaction between the radiators. For a WiMAX band, the size of the entire MIMO antenna is 0.22λg showing effective miniaturization. And the gain, efficiency and isolation are 3.7dBi, 56% and 17dB, acceptable to the industrial standard.

Design of a Compact Bandstop Filter-combined UHF-band CRLH Bandpass Filter to Suppress the Spurious in L-band

In this paper, we propose a way to improve the quality of L-band wireless communication from unfriendly influential factors lying in the neighboring RF bands. The UHF-band system has resonator components and they generate harmonics as the spurious in the L-band. Therefore, a metamaterial CRLH bandpass filter is designed for the purpose of system miniaturization and smaller insertion loss, and its spurious phenomenon is observed in the frequency domain. And its harmonics in the L-band are suppressed by a compact bandstop filter whose equivalent circuit is newly developed. The design methodology is validated by the equivalent circuit to be compared with commercial full-wave EM software simulations, where the spurious is dropped by 20dB. Also, the advantage of the proposed design is presented by the comparison where our filter is much smaller than the conventional parallel edge coupled filter by over 50%, with excellent harmonic suppression.

Switchable beam pattern antenna for wireless communication devices

In this paper, a switchable beam pattern antenna design with a combination of electric-magnetic radiators for wireless communication is presented. To generate a switchable antenna radiation pattern, a structure combining with a dipole and a loop antenna is proposed. The frequency bandwidth defined by S11<−10 dB is approximately from 1.814–2.078GHz (256MHz) with maximum gain of 3.35dBi. Maximum beam direction can be steered by changing switch on/off configurations with maximum tilted beam of 90 degree.

Flat metamaterial antenna with dual-circular-polarization at the −1st-order-resonance mode, applicable to reconfigurable RF systems

In this paper, a novel compact and dual-circular-polarized antenna is proposed. To be physically small, the electromagnetic wave is radiated at the -1st-order resonance mode of a planar composite right- and left-handed(CRLH) antenna, instead of the +1st resonance mode. To enable two circular polarizations in one structure, the orthogonal coaxial feed points for the 90°-angular difference are decided at the -1st resonance mode, and connected to the output ports of a hybrid branch-line coupler for 90°-phase difference. The functional block diagram is given, and is followed by the steps of full-wave simulations for design and the performance is verified by the measurement of the fabricated antenna with the test frequency of the 2.37-2.40 GHz band. The LHCP and RHCP will be observed with good inter-polarization isolation and axial ratio, and the applicability to a compact reconfigurable RF device will be considered.