• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.86-90
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• 2002

본 논문에서는 Ka-band 위성중계기에 사용되어지는 수신하향변환기(Receiver-Downconverter) 모듈의 설계 및 제작 그리고 시험 결과에 대하여 기술하였다. 개발된 수신하향변환기는 30.6~31㎓ 대역의 신호를 입력으로 받아들여 20.8~21.2㎓ 대역의 신호를 출력하는 일종의 Downconverter 이지만, 모듈의 입력단에 저잡음 증폭부가 포함된 수신기의 역할도 하고 있다. 개발된 모듈은 제작과정 및 시험과정에 있어 위성중계기 부품 제작 규정을 준수하였으며, 그 개발된 성능은 현재까지 알려진 국내외 유사 부품중의 최고의 성능을 보여주고 있다. 측정된 모듈의 성능은 상온에서 1.9㏈의 잡음지수, 55㏈ 이득, 58dBc의 C/l3 값을 보여주고 있다. 제작된 모듈의 크기는 93mm$\times$84mm$\times$26mm이며 무게는 240g으로서 국내외 유사 제품에 비해 소형이다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.71-76
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• 2001

A Ka Band 3-stage MMIC (Monolithic Microwave Integrated Circuits) LNA (Low Noise Amplifiers) has been designed and fabricated far the Ka band satellite communications and BWLL(Broad Band Wireless Local Loop)system. The MMIC LNA consists of two single-ended type amplification stages and one balanced type amplification stage to satisfy noise figure, high gain and amplitude linearity. The 0.15${\mu}{\textrm}{m}$ pHEMT has been used to provide a ultra low noise figure and high gain amplification. Series and Shunt feedback circuits and λ/4 short lines were inserted to ensure high stability over the frequency range form DC to 80 GHz. The size of the MMIC LNA is 3.1mm$\times$2.4mm(7.44mm$^2$). The on wafer measured performance of the MMIC LNA, which agreed with the designed performance, showed the noise figure of less than 2.0 dB, and the gain of more than 26 dB, over frequency ranges from 22 GHz to 30 GHz.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.489-496
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• 2021

The X-band frequencies for transmitting the data from earth observation satellites are limited, so a number of satellites share the frequency bands. In order for multiple satellites to utilize same or adjacent frequency bands, International Telecommunication Union - Radiocommunication (ITU-R) limits power flux density (PFD), which overcomes the interferences among multiple satellites. However, even under the regulation, the interference effect needs to be analyzed when multiple satellites are connected to communicate with multiple ground stations (GSs) located close to each other. In this paper, the interference effect is analyzed based on signal to interference plus noise ratio (SINR) when two low earth orbit (LEO) satellites operating in different orbits are connected to communicate with randomly located two GSs in Korean peninsula. From the analysis results, it is confirmed that there can be interferences during 365 days operation even if the satellites meet PFD requirement, but the periods under interference effects are short and the interference can be foreseen.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.3
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• pp.152-155
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• 2013

In this paper, the reduction of the figure of merit depending on the increased spill-over when the parabolic reflector is cut off partially for low-profile configuration in the satellite broadcast receiving antenna is analyzed. Also for the accurate analysis and simulation, it is considered that the noise temperature is increased due to the effect of ground thermal noise toword the sidelobes and back lobes when the antenna is tracked from $0^{\circ}$ to $60^{\circ}$ in elevation angle, and that the total noise temperature is increased because to the noise figure of LNA. As the results, noise temperature is increased up to about 15K and G/T ratio is decreased to about 2.5dB, when the reflector is cut 35% off partially.

• Journal of Satellite, Information and Communications
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• v.8 no.1
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• pp.31-34
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• 2013

This paper deals with the interfering audio noise caused by LTE(Long Term Evolution) UE(User Equipment) which is 4th generation mobile communications on audio devices. At first, we realized that the interfering signal of the LTE UE is determined by the transmit power of the LTE UE through analysis and measurement. Then, we performed to measure audio noise level according to the variation of transmitting power level and separation distance between the LTE UE and an audio device. As a result, it is required that minimum separation distance should be 25 cm and above in order to protect audio device from the interference noise of the LTE UE with the maximum transmit power level of 22 dBm.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.1 no.1
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• pp.1-9
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• 2002

In this paper, a DRO (Dielectric Resonator Oscillator) with high stability in DSRC(Dedicated Short Range Communication) is designed and fabricated. The DRO shows the phase noise characteristic of -109.3 dBc/Hz at 100 kHz offset from the fundamental frequency. The output power of 11.53 dBm, and the second harmonic suppression of 55.33 dBc for the DRO are obtained. This DRO with high stability of the phase noise characteristic can be used for the system in DSRC.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.1-5
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• 2010

Recently, the transmission amount of information that each single person requires is growing by development of electron information communication technology. So in this paper we analysis the phase noise characteristics to obtain a most suitable of SNR performance request characteristic by BER on CATV transmission system that satisfy performance request DOCSIS 2.0 standard. Especially we get the parameter value of PLL that satisfy phase noise characteristic request standard using developed simulator. Presented method can be used to obtain a performance request standard connection performance request standard of high speed CATV transmission system in the future.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.451-453
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• 2011

본 논문에서는 챔퍼 디스턴스 매칭(chamfer distance matching)를 이용하여 위성 영상 상의 북한군 자주포진지(self-propellent artillery position)를 매칭하는 기법을 제안한다. 먼저 입력되는 위성 영상을 잡음환경에 강인한 가우시안-라플라시안 연산자를 이용하여 에지(edge)를 추출한다. 추출된 에지 영상의 각 픽셀에 대해 가장 가까운 에지까지의 거리를 나타내는 거리 변환(distance transform) 영상을 생성한다. 템플릿 영상은 다양한 자주포진지 영상에서 샘플링된 영상으로 에지를 추출한 후 거리 변환을 거친다. 마지막으로 템플릿 영상을 입력된 거리 변환 영상에 윈도우 슬라이딩(window sliding)하여 최소값의 가지는 위치를 구한다. 제안 기법은 잡음에 강인한 가우시안-라플라시안 연산자를 사용하여 기상조건에 의한 입력 영상의 편차에도 효율적인 매칭이 가능하다. 또한 에지 기반의 챔퍼 매칭을 이용하기 때문에 비 균일 조명 환경에서도 강인한 매칭이 이루어진다. 전산 모의 실험에서 제안 알고리즘은 입력 위성 영상 상의 자주포진지를 적은 계산량으도 신뢰있게 매칭함을 보여준다.

• Journal of Astronomy and Space Sciences
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• v.10 no.2
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• pp.189-196
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• 1993

Satellite laser ranging observation of LAGEOS II has been performed using the SLR System at Sheshan Laser Ranging Station, Shanghai Observatory. And we obtained 1,838 observational points. The observed range data is corrected by means of system delay correction using ground target observation, atmospheric refraction delay correction, offset correction, general relativistic correction and tide correction including solid tide, polar tide and ocean tide. As a result, the determined range delay mean value is 19.12m and the mean internal accuracy by means of polynomial fitting and least square method is $\pm$7cm. Corrected observational points are 1,340 and noise ratio to total observational points is 27.1%.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.84-95
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• 2011

In this paper, we present a deblocking algorithm that removes grid and staircase noises, which are called "blocking artifacts", occurred in the compressed satellite images. Particularly, the given satellite images are compressed with equal quantization coefficients in row according to region complexity, and more complicated regions are compressed more. However, this approach has a problem that relatively less complicated regions within the same row of complicated regions have blocking artifacts. Removing these artifacts with a general deblocking algorithm can blur complex and undesired regions as well. Additionally, the general filter lacks in preserving the curved edges. Therefore, the proposed algorithm presents an adaptive filtering scheme for removing blocking artifacts while preserving the image details including curved edges using the given quantization step size and content analysis. Particularly, WLFPCA (weighted lowpass filter using principle component analysis) is employed to reduce the artifacts around edges. Experimental results showed that the proposed method outperforms SA-DCT in terms of subjective image quality.