• 한국군사과학기술학회지
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• 제16권6호
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• pp.811-818
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• 2013

In this paper, we have designed the elliptical dual offset gregorian antenna which can use Ka band earth station antennas in the fixed-satellite service. The structure of antenna is increasing the antenna gain by decreasing blockage areas and decreasing wind effects by shortening height of the antenna. The corrugate horn antenna for this antenna has symmetric radiation patterns and low side lobe levels that can meet ITU-R envelope. The distribution of electric field on a aperture of main reflector is calculated by an ray-tracing method that use the radiation pattern of the feed horn. The final geometric of antena is decided by choosing the distribution that comply with antenna requirement. The FEKO analysed electrical performance of this antenna. The fabricated antenna has 45.0dBi(@30.0GHz)/41.7dBi(@20.2GHz), high efficiency and low side lobe level that meet ITU-R S. 580-6 envelope.

• 한국전자파학회논문지
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• 제11권7호
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• pp.1247-1257
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• 2000

옵셋 안테나 (offset-fed dish antenna)를 분석한다. DBS 수신안테나로서 널리 사용되는 옵셋 안테나는 비대칭, 개방형 구조 때문에 해석이 어렵다. 본 논문에서는 푸리에 변환 방법과 Physical Optics를 이용하여 옵셋 반사판과 피드 혼 개구면으로부터의 방사 전계에 대한 정확한 성공적으로 유도하였다. 또한 반사판의 지경, 촛점거리, 단면 등 모든 다양한 구조적 환경에서 해석할 수 있도록 여러 구조 인자를 가진 해를 도출하였다. 이를 이용하여 한 개의 반사판에 어려 개의 혼을 배치시킨 다중 빔 안테나를 분석하고, 특히 동경 116$^{\circ}$의 무궁화위성 (중계기출력 59dBW)과 동경 139$^{\circ}$로 계획되어 있는 Orion 위성 (중계기출력 54dBW)로부터 동시에 수신할 수 있는 안테나를 고찰한다.

• 대한전자공학회논문지
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• 제27권2호
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• pp.31-38
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• 1990

외삽기법을 시용하여 실내의 소형 안테나 레이지에서 안테나 이득을 측정할 수 있는 시스템을 개발하였다. 외삽기법은 안테나의 절대이득 측정에 보통 사용되는 2-안테나 방법과 유사한데 가까운거리 구간에서 수신되는 신호의 크기를 거리의 함수로 연속적으로 측정한 후 외삽법을 사용한 신호처리로 무한거리에서 수신되는 신호의 크기를 계산함으로써 안테나의 원역장 이득을 구할 수 있다. 또한 원역장 이득과 근역보정인자를 결합하여 근역장 이득을 안테나로부터의 거리의 함수로 구하는 것도 가능하다. 이 외삽기법을 사용하여 측정한 표준이득 혼 안테나와 OEC 안테나의 이득 측정결과를 고찰하였다.

• 한국군사과학기술학회지
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• 제6권2호
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• pp.73-82
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• 2003

For measurements and analysis of dielectric characteristics of planar slabs of microwave absorbing materials, I have applied a free-space method in the frequency range of 8~14 GHz. The measurement system for free-space method consists of transmit and receive antennas, mode transitions, precision coaxal cables, the network analyzer, and a computer Special Spot-focused horn lens antenna was used to eliminate diffraction effects. Diffraction effects at the edges of the sample are minimized by satisfying the condition for minimum transverse dimension of the plate and the beamwidth of the antennas at the focus. The time-domain gating feature of the network analyzer and the thru, reflect, and line(TRL) calibration technique were used to eliminate the effects of undesirable multiple reflections. The complex coefficients of reflection and transmission, $S_{11}$ and $S_{21}$, of planar samples were measured for standard materials such as Teflon, Rexolite$\textregistered$ 2200. The results were compared with existing measurement method. And I applied a free-space method for measurement to measure dielectric constants of some electromagnetic absorbing materials. Dielectric properties for the same samples were also measured with a 7mm coxial transmission line method for purposes of comparison with the free-space method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.229-232
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• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice, brown rife and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The effect of density fluctuation, which is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation and moisture density is proposed for reducing the effects of density fluctuation on the moisture content measurement.

• Journal of Electrical Engineering and information Science
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• 제2권4호
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• pp.72-78
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• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice ,brown rice and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The moisture content of grain varied from 11 to 25% based on this wetted condition. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using he predicted model for estimating dielectric constants of grain. The effect of density fluctuation, high is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation an moisture density is proposed of reducing the effects of density fluctuation on the moisture content measurement.

• ETRI Journal
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• 제33권6호
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• pp.965-968
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• 2011

A 1.485-Gbit/s video signal transmission system at carrier frequencies of 240 GHz and 300 GHz was implemented and demonstrated. The radio frequency front-ends are composed of Schottky barrier diode subharmonic mixers (SHMs), frequency triplers, and diagonal horn antennas for the transmitter and receiver. Amplitude shift keying with an intermediate frequency of 5.94 GHz was utilized as the modulation scheme. A 1.485-Gbit/s video signal with a high-definition serial digital interface format was successfully transmitted over a wireless link distance of 4.2 m and displayed on an HDTV with a transmitted average output power of 20 ${\mu}W$ at a 300-GHz system.

• 천문학논총
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• 제11권1호
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• pp.221-229
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• 1996

We have developed a measurement system with which harmful radio noise can be detected. It was designed to cover 1GHz band width centered at l.5GHz and 22.2GHz ($H_2O$ line).The system consists of pyramid horn antennas, receivers, equatorial tracking system, spectrum analyzer, and PC for the control of the servo and data taking. As a test of the system, the site of Taeduk Radio Astronomy Observatory (TRAO) was investigated to see if there is any harmful radio interference. It is found that in 22GHz band there is no significant radio noise, but there are identified and unidentified artificial radio signals in 1-2GHz range. However a simple calculation of radiation power shows that it is week enough not to affect the observations in TRAO.

• 한국전자파학회논문지
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• 제11권5호
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• pp.806-812
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• 2000

본 논문에서는 한 파장보다 큰 배열안테나에 대하여 이론적으로 고찰하였고, 실험을 통하여 이를 검증하였다. 이러한 배열안테나의 그레이팅 로브를 이용하여 예리한 반-전력빔폭(HPBW)을 갖도록 하였다. 배열안테나의 배열간격을 적절히 설정함으로써 반-전력빔폭 뿐만 아니라 사이드로브레벨(SLL)까지도 조절할수 있었다. 이를 위해 4개의 혼 안테나로 배열안테나를 구현하였으며, 방사패턴은 9GHz에서 측정하여 제시한 방법의 타당성을 입증하였다. 이때 배열안테나를 구성하는 각각의 혼은 64.3$\times$82.5$\textrm{mm}^2$의 크기와 27$^{\circ}$의 반-전력빔폭을 갖는 것을 사용하였다. 그레이팅 로브를 이용하기 위해 안테나 사이의 배열간격을 1파장보다 크게 하므로서 가시영역에서 그레이팅 로브가 발생하게 하였다. 배열간격을 2.5λ, 2.7λ와 3.0λ로 변화시켜가면서 반-전력빔폭을 측정한 결과 각각 4.3$^{\circ}$, 3.3$^{\circ}$그리고 1.7$^{\circ}$를 얻을 수 있었으므로 반-전력빔폭이 확연히 줄어들었으며 예리한 반-전력빔폭을 얻을수 있었다. 그러므로 좁은 반-전력빔폭을 갖는 안테나를 설계하는데 유용하게 이용할 수 있을 것이다.

• Journal of electromagnetic engineering and science
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• 제18권1호
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• pp.63-69
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• 2018

This work demonstrates attenuation effects of plasma on waves propagating in the 26.5-40 GHz range. The effect is investigated via experiments measuring the transmission between two Ka-band horn antennas set 30 cm apart. A dielectric-barrier-discharge (DBD) plasma generator with a size of $200mm{\times}100mm{\times}70mm$ and consisting of 20 layers of electrodes is placed between the two antennas. The DBD generator is placed in a $400mm{\times}300mm{\times}400mm$ acrylic chamber so that the experiments can be performed for plasma generated under various conditions of gas and pressure, for instance, in air, Ar, and He environments at 0.001, 0.05, and 1 atm of pressure. Attenuation is calculated by the difference in the transmission level, with and without plasma, which is generated with a bias voltage of 20 kV in the 0.1-1.4 kHz range. Results show that the attenuation varies from 0.05 dB/m to 9.0 dB/m depending on the environment. Noble gas environments show higher levels of attenuation than air, and He is lossier than Ar. In all gas environments, attenuation increases as pressure increases. Finally, electromagnetic models of plasmas generated in various conditions are provided.