• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.265-277
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• 1998

In this paper, to investigate the possibility of fading reduction effect and high transmission rate in indoor multipath propagation environment, we measured and analyzed broadband signal conducting by frequency sweeping method in LOS(Line-of-Sight) environment. In measuring, we used vertically polarized, horizonatally polarized and circularly polarized and circularly polarized antenna to compare the fading reduction effect and the characteristic of bandwidth amplitude fluctuation between each broadband signals. As a result, it can be seen that the circularly polarized antenna can reduce the amplitude deviation of the broadband signal because it can remove the odd-times reflected wave in LOS environment. And also, It was found that the best effective diversity reception method is to use polarization branches, which install a circularly polarized antenna at the transmitting end and compose the vertical and horizontal antenna at the receiving end.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.78-84
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• 2008

In this paper, the reconfigurable annular ring slot antenna with circular polarization diversity is proposed for SDMB(Satellite Digital Multimedia Broadcasting) system. The proposed antenna consists of a ring slot with four tuning stubs. Four PIN diodes are attached to switch circular polarization diversity. By switching the diodes ON or OFF, the proposed antenna can be operated either RHCP mode or LHCP mode. The experimental result shows that the proposed antenna has an impedance bandwidth(VSWR${\leq}$2) of 570MHz(2.47-3.04GHz) at LHCP mode, an impedance bandwidth (VSWR${\leq}$2) of 560MHz(2.45-3.01GHz) at RHCP mode, a maximum gai of 3.1dBi at RHCP mode, 4.76dBi at LHCP mode. The 3dB CP bandwidth of about 100MHz at both RHCP and LHCP mode is achieved at the center frequency 2.63GHz. The proposed antenna is suitable for application such as mobile satellite communications, WLAN(Wireless Local Area Networks), and broadband wireless communication systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.651-654
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• 2008

협대역 다중접속 방식의 한계를 벗어난 Ultra-wide band(UWB) 기술이 고속 데이터 전송을 위해 많이 개발되어지고 있다. UWB 시스템은 방사전력 제한을 두고 있어서 근거리 실내 무선통신 분야에서 활용 범위가 확대되고 있다. 하지만 실내 무선 환경에서는 벽, 천장, 바닥 그리고 실내에 위치한 장애물 등에 의한 다중경로 페이딩 영향으로 초고속 실내 무선통신 서비스를 제공하는데 어려움이 있다. 이러한 실내 다중경로 성분에 의한 페이딩을 경감시키는 여러 가지 방법 중에서 원형편파를 이용하면, 상대적으로 긴 지연을 갖는 강한 다중경로 성분을 효과적으로 제거할 수가 있기 때문에 수신신호의 RMS 지연 감소, 페이딩 경감 및 신호강도 개선효과 등을 얻을 수 있다. 본 논문에서는 원형편파를 고려한 수정된 UWB 채널의 파라미터를 수정 정립하였고, 수정된 채널모델을 UWB 시스템에 적용하여 성능 개선을 시도하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.642-648
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• 2000

We introduce a new application of the genetic algorithm for design of the coaxial fed circularly polarized rectangular microstrip antenna. The GA shows excellent results for the design of the microstrip antenna which have a very complex objective function including the input impedance, the effective loss tangent and the axial ratio. The objective function is derived from the cavity model, and the size and the feeding point are optimized by the genetic algorithm. The experimental results show good agreement with the simulated results.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.217.1-217.1
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• 2012

현존하는 저궤도위성의 S-Band 관제채널은 대부분 RH 또는 LH 편파를 사용한다. 그러나 다목적실용위성 3호와 같이 RH와 LH 편파를 동시에 사용하는 위성의 경우 위성추적을 위해 사용되어지는 지상안테나는 RH와 LH 편파를 동시에 수신하여야할 뿐만 아니라 편파변경시점에 따라 송신출력의 편파가 변경되어야하기 때문에 지상에서 위성으로 명령을 전송할 수 있는 송신가능시간(Command Window)에 영향을 미친다. 이러한 저궤도위성의 RH와 LH 편파의 신호세기는 위성체의 자세 및 운영방법에 따라 결정되어지기 때문에 다양한 형태의 편파수신경향성을 나타낸다. 따라서 이러한 영향을 최소화하기 위하여 지상안테나는 RH 및 LH 편파에 대하여 자동추적기능을 수행하여 위성을 추적하게 된다. 지상안테나의 자동추적기능은 수신되는 신호세기를 순간적으로 비교하여 가장 큰 세기의 신호가 수신될 수 있도록 제어하는 기술로서 수신신호의 형태에 따라 영향을 받으며 이 때 발생하는 오차는 위성추적에 지대한 영향을 미친다. 또한 편파가 변경되는 시점에서는 자동추적오차가 증가하게 되는 경향을 나타나게 된다. 따라서 본 논문에서는 다양한 형태로 동시 수신되는 RH 및 LH 편파의 자동추적오차를 분석하여 송신가능시간(Command Window) 및 수신신호에 어느 정도 영향을 미치는지에 대하여 분석하였으며 본 영향을 최소화할 수 있는 방법에 대하여 기술하였다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.546-549
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• 2003

본 논문에서는 GPS용 안테나의 소형화를 위해 패치 길이 방향으로 T자형 슬릿 구조를 이용하여 GPS 중심 주파수인 1.575 GHz로 안테나를 설계, 제작하였다. 선형편파의 경우, 설계 주파수에서 패치 높이 3 mm 일 때, 패치 길이 $48 mm{\times}$폭 90 mm로 평면형($84 mm{\times}90 mm$)에 비해 42.9 %의 길이 단축 효과를 얻었으며, 반사손실 -20.3 dB, -10dB 대역폭 9 MHz (0.5 %), E-면 -3dB 빔폭 $77.7^{\circ}$, H-면 -3dB 빔폭 $66.2^{\circ}$, 이득 5.3 dBd의 특성을 나타내었다. 원형편파의 경우, 설계 주파수에서 패치 크기는 $57 mm{\times}57 mm$의 정방형으로서 T자형 슬릿 길이만을 조절하여 $90^{\circ}$의 위상차를 야기시켰으며 평면형 원형편파($82 mm{\times}86.5 mm$)에 비해 54.2 %의 면적 축소 효과 및 이득 3.89 dBd, 반사손실 -28.9 dB, 축비 1.96 dB, 2dB 축비 유지 대역폭 18 MHz로 양호한 원형편파 특성을 얻었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.32-38
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• 2014

In this paper, we design a secant pattern antenna combined with a septum circular polarizer to be used in the satellite data communications. To generate a radiation pattern with secant type, Fourier relationship between current distribution and space factor is applied and the circular symmetric structure of the aperture simplifies the design. The optimization process is performed by combining the radiator with the septum circular polarizer, and it is confirmed that the designed radiation pattern, axial ratio, and return loss characteristics satisfies the required performance of the antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.113-121
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• 2013

In this paper, quadruple polarized antenna system with a reconfigurable feeding network is presented. The proposed antenna system consists of the reconfigurable feeding network for fourth polarization such as vertical/horizontal linear polarization and right-handed/left-handed circular polarizations or 45 degree tilted vertical/horizontal linear polarization and patch antenna to receive the signals with various polarizations. In order to receive a signal in any direction, the proposed antenna is designed by electrical switches for reconfigurable polarization. The insertion loss of the designed feeding network in the proposed antenna system is approximately 1.2 dB. The measured 3 dB axial bandwidth and gain of the proposed antenna are about 2 % and 4 dBi(c).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.302-311
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• 1999

In this paper, in order to suggest an optimal polarization diversity composition method in indoor radio wave propagation environments, the variation of the cross polarization discrimination(XPD) was theoretically analyzed by a computer simulation and compared to the actual measured data. From the results, it can be seen that the cross polarization discrimination of the case, a circularly polarized antenna was used at the transmitting end as well as the vertical and horizontal polarized antenna branches were used at receiving end (CV-CH), is lower than that of the case, horizontal polarized antenna at the transmitting end as well as the horizontal and vertical polarized antenna branches at the receiving end(HH-HV), and that of the case, vertical polarized antenna at the transmitting end as well as the vertical and horizontal polarized antenna branches at the receiving end(VV-VH). In this paper, to get more effective CV-CH polarization diversity composition, the amount of cross polarization discrimination values at the signals received by horizontal polarized antenna is compensated and the polarization diversity effect through the cumulative probability distribution is estimated. From the evaluation results, it was found that the polarization diversity effect was better at the compensated case than at the uncompensated case. On the other hand, it can be known that the polarization diversity effect is getting better as the cross polarization discrimination values are getting lower, and also be known that the effect can be improved if a transmitting antenna is composed of the ellipse polarized antenna by adjusting the axial ratio of the circularly polarized antenna and, a receiving antenna is made up of the vertical and horizontal polarized antenna branches.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1034-1041
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• 2012

In this paper, a compact circularly polarized metamaterial patch antenna using the -1 mode that is induced by the composit right-left handed(CRLH) transmission line is proposed. Basically, since the -1 mode is the same properties with the +1 mode of the conventional patch antenna, the circular polarization(CP) is realized. If two orthogonal -1 modes are excited with $90^{\circ}$ phase difference, the CP property can be obtained. In order to obtain two orthogonal modes and $90^{\circ}$ phase difference, 4 mushroom structures having the shape of triangle are employed and the inter-digital gaps are optimized, respectively. The fabricated antenna is based on RT/duroid5880 substrate and the total area of the 4 mushrooms is $0.161{\lambda}_0{\times}0.161{\lambda}_0$. It is confirmed that the center frequency of the proposed antenna is measured as 2.845 GHz and it operates from 2.830 GHz to 2.850 GHz. In addition, the antenna maintains the CP property from 2.842 GHz to 2.847 GHz at the peak gain and the measured radiation efficiency is 46 %.