• 한국전자파학회논문지
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• 제12권6호
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• pp.906-911
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• 2001

본 논문에서는 비화 통신을 위하여 chirp 방식을 이용한 BPSK 시스템의 LPI(low probability of intercept)와 AJ(anti jamming) 성능을 분석하였다. Chirp 방식은 주파수를 전체 확산대역 내에서 임의적으로 변화시켜 신호의 주기적인 특성을 제거하기 때문에, feature parameter인 chip rate를 검출하는데 용이한 DAM(delay and multiplier)과 반송파 주파수 검출에 용이한 SC(Squaring Circuit)에 대항하여 뛰어난 LPI 특성을 가진다. chirp parameter의 변화에 따른 LPI 특성으로 chirp duration(Tc)이 커질수록 좋은 LPI 성능을 보인다. PBNJ(partial band noise jammer)환경에서, chirp 방식이 이론적인 DSSS(Direct Sequence Spread Spectrum) 방식에 비하여 AJ 성능이 우수함을 시뮬레이션으로 확인하였다. PBNJ와 MTJ(multi-tone jammer)를 비교하였을 때, chirped BPSK 시스템이 동일 JSR(jammer to signal power ratio)에서 MTJ에 더 우수한 AJ 성능이 있다.

• 한국군사과학기술학회지
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• 제11권5호
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• pp.23-33
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• 2008

In this paper, we verify the performance of LDPC coded OFDM/DS system by Monte-Carlo simulation of BER on Eb/No. The simulation results show that LDPC coded OFDM/DS has a strong anti-jamming characteristic over pulse-noise jammer and partial-band noise jammer. The performance of LDPC coded OFDM/DS system is evaluated on both faded waveforms and non-faded waveforms. For non-faded waveforms, high coding gain is attained due to LDPC, even when waveforms have short PN sequence and JSR is only 5dB. Especially, the increase in the repeated number of LDPC decoding enhances coding gain. However, faded waveforms cannot achieve sufficient average effect when PN sequence is short. High coding gain of faded waveforms can be achieved by extending length of PN sequence. In addition, we compare LDPC coded OFDM/DS system with Convolutional coded OFDM/DS system. The simulation results illustrate that when LDPC coded OFDM/DS system with short PN sequence has sufficient average effects, the system shows lower BER than Convolutional coded OFDM/DS system with long PN sequence.