• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
• /
• pp.460-463
• /
• 2004

There is a trend to replace TWTA of SSPA in S-Band uplink application for satellite operation. KARI developed l20W full S-Band SSPA system in early 2004. This paper covers SSPA system design and its test results. Through tests, nominal gain of 57dB, gain stability of +/-1dB over frequency, and gain stability of +/-0.5dB over temperature were shown. IMD value of -16.5dBc, -19dBc were revealed in PI and P3 output operations. With meeting specifications, l20W SSPA is expected to be used in operational S-Band uplink application.

• 전기의세계
• /
• 제39권5호
• /
• pp.27-37
• /
• 1990

In this paper some of the important trends in the spacecraft technology development have been discussed. Trends of higher satellite radiate power, which involves higher TWTA powers and antenna reconfiguration, and Ka-band (30/20 G $H_{z}$) utilization are discussed. Evolutionary trends in satellite communications in general have demonstrated immense potential for meeting the evolving nees and challenges regarding provision of global telecommunications during over past two decades. Their promise for the coming decades as we enter the 21st century may far surpass our imagination. The expansion of fixed satellite service market will depend upon more inelligent spacecraft and a network of more cost effective small earth stations. Radiation hardened microwave analog technologies and high speed digital technologies are getting ready to meet the challenge posed by future markets. At present commercial satellite communications are going through a trasition period.d.

• 전자공학회논문지A
• /
• 제33A권6호
• /
• pp.72-80
• /
• 1996

This paper presetns the development of a SSPA operating at KU-band(14~14.5 GHz) in order of replace TWTA used in the terrestria transponder of a satellite communication. The driving stage of SSPA uses internally matched 2W, 4W, 8W FET and the power stage is coupled with two internally matched 8W FET by branch-line cominer. The SSPA is fabricated with oth the RF circuit and the bias circuitry operating temperature compensation, regulation and sequence on aluminum housing. The SSPA testing resutls implemented in this way show 24.8$\pm$1dB small-signal gain, 41dBm P1dB power, a typical two tone C/IM3, -33dBc with single carrier backed off 6dB from p1dB, and gain stability over temeprature (-30~50)$\pm$1dB.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.649-659
• /
• 2003

OFDM/FH communication system Is widely used in the wireless communication for the large capacity and high-speed data transmission. However, phase noise and PAPR (peak-to-average power ratio) are the serious problems causing performance impairment. In this paper, PLL (phase locked loop) frequency synthesizer with high switching speed is used for the phase noise model. SSPA and TWTA are considered for the nonlinear HPA model. Under these conditions and by approximating $e^{j{\phi}[m]}$ into $1 + j{\phi}[m]-\frac{1}{2}{\phi}^2[m]$ for the phase noise nonlinear approximation, SINR (signal-to-interference-noise-ratio) with nonlinear HPA and phase noise is derived in the OFDM/FH system. The bit error probabilities (BER) are found by computer simulation method and semi-analytical method. The simulation results closely match with the semi-analytical results.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.264-266
• /
• 2006

This traveling wave tube amplifier maintenance system was developed for performance of microwave Surveillance radar traveling wave tube amplification parts, and field operation. The Maintenance system is traveling wave tube amplification part RF output waveform measurement and HVPS Voltage adjustment and a maintenance function are offer. The system was developed as an embedded system base it consisted of Linux os which applied a top-down design and visual technique. Therefore change and easy extension of a system. This paper discussed characteristic of maintenance equipment function, composition, and an employment program.

• 한국통신학회논문지
• /
• 제21권8호
• /
• pp.2109-2118
• /
• 1996

The neural convolutional decoder(NCD) was proposed as a method of decoding convolutional codes. In this paper, simulation results are presented for coherent BPSK in memoryless AWGN channels and coherent QPSK in the satellite channels. The NCD can learn the nonlinear distortion caused by the charactersitics of the satellite channel including the filtering effects and the nonlinear effects of the travling wave tube amplifier(TWTA). Thus, as compared with the AWGN channel, the performance difference in the satellite channel between the NCD for the systematic code and the Viterbi decoder for the nonsystematic code is reduced.

• 한국전자파학회논문지
• /
• 제17권8호
• /
• pp.773-787
• /
• 2006

비행체 탑재 레이다는 민군 겸용으로 기상에 관계없이 전천후로 비행체의 안전 항행, 임무 감시, 사격 통제, 충돌 회피, 이착륙 등 비행에 필수적인 항공 전자 장치이다. 본 논문에서는 헬기 탑재 다중 모드 X-밴드 펄스 도플러 레이다 시험 모델의 설계, 제작 및 비행 시험 결과를 제시한다. 레이다 시스템은 안테나부, 송수신부, 신호처리부와 전시부의 4개의 LRU로 구성되며, 개발 기술은 평판 슬롯 배열 안테나, TWTA 송신기, coherent I/Q detector, 디지털 펄스 압축, MTI, DSP 기반 도플러 FFT 필터, 적응 CFAR, 도플러 추정보상 기법, 비행 안정화 및 TWS 추적 처리기를 포함한다. 개발된 레이다 시스템의 설계 성능은 다양한 지상 고정 및 이동 시험과 헬기 탑재 비행 시험을 통하여 이동 비행체 이동 클러터 보상과 MTD 성능을 확인하였다.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 1996년도 학술대회
• /
• pp.27-31
• /
• 1996

In this paper, The SSPA(Solid State Power Amplifier) is 100 watts amplifier which is used with C-Band Satellite communication Up-Link frequency, 5.875 ∼6.425 GHz. SSPA requires more output power than is available from a single GaAs FET with result it is necessary to combine the output of many device. To achieve a high power, it is important to make a good N-way power divider which has a small different phase, good combining efficiency and high power handling capability. The reliability of Power GaAs FET decrease with increasing junction temperature, power amplifier in general dissipate amount of power. It is important to provide them with a heatsink and a temperature compensation circuit to dispose of the unwanted heat. To compensate temperature, Using PIN diode attenuator, it is enable to get a precision gain control. The output power of the SSPA is more than 100 watt with which the TWTA (Traveling-Wave Tube Amplifier) can be replaced. Each stage was measured by the Network analyzer PH8510C, Power meter Booton 42BD, The gain is more than 53 dB, flatness is less than 1.5 dB.

• 한국위성정보통신학회논문지
• /
• 제3권1호
• /
• pp.15-21
• /
• 2008

OFDM (직교 주파수 분할 다중화) 신호의 높은 PAPR은 시스템의 송신단에서 전력증폭기의 비선형적 특성으로 인해 비선형 왜곡이 불가피하게 발생한다. 이 현상은 대역 내 왜곡과 대역 외 방사를 초래한다. 본 논문에서는 다항식 (polynomial) 모델에 기반한 사전왜곡(pre-distortion) 기법으로 이러한 문제를 보상하는 기법을 제안한다. 비선형 및 역비선형 다항식 모델 추정은 LSE(Least Square Error) 알고리즘으로 수행한다. 또한 시스템의 성능 향상을 위해 피크제거와 클리핑 결합기법을 이용해 OFDM 신호가 전력증폭기의 포화 영역 근처에서 동작함으로써 발생하는 왜곡된 신호의 진폭을 제거한다.

• 한국통신학회논문지
• /
• 제19권6호
• /
• pp.1115-1125
• /
• 1994

본 논문에서는 위성 채널에 효율적인 오류 정정 방식으로 펑쳐드 콘볼루션 부호(punctured convolutional code)를 이용한 직렬 연결 부호(concatenated code) 방식을 제안하고 위성 채널을 모델링 하여 제안된 오류 정정 방식의 오율 성능을 모의 실험을 통하여 분석하였다. 제안된 직렬 연결 부호 방식은 외부 부호를 (255.223)RS 부호로 하고 구속장 길이가 7인 2/3 펑쳐드 콘볼루션 부호를 내부 부호로 사용하였으며, 일반적으로 위성 부호 채널(satellite coding channel) 모델로 사용되고 있는 광대역 부가 백색 가우시간 잡음 채널의 부정확성을 보완하기 위해 위성 채널 입력 여과기, 고출력 진행파관 증폭기(traveling wave tube amplifier), 위성 채널 출력 여파기 및 하향링크 잡음 등으로 구성되는 위성 부호 채널을 모델링하여 성능 평가 실험에 사용하였다.