分析火星进入、下降、着陆(EDL)过程中直接对地通信("旗语"信号)使用的X频段MFSK通信体制,研究发现,当多普勒动态较高(大于500Hz/s)时信号的误检率较高,无法保证重要事件信息的正确接收.针对这个问题,提出基于优先级的单音与MFSK信号联合通信方式,将重要事件的优先级设为1,利用单音信号传递事件信息,其余事件仍用MFSK信号传递.实验结果表明,单音信号的检测门限比MFSK信号低2dB左右,基于优先级的单音与MFSK信号联合通信方式更有利于降低信号误检率.%A specialized form of frequency-shift keying called MFSK used in the X-band direct-to-earth communication link during entry, descent, and landing (EDL) processes of Mars probe is analyzed. The in-depth study shows the probability of incorrect detection of MFSK signal is high when Doppler frequency change rate is greater than 500Hz/s, which can not ensure the important event information received correctly. For this problem, a single-tone and MFSK signal joint communication mode based on priority is proposed. The single-tone signal is used to report important events whose priorities would be set to 1. On the other hand, the MFSK signal is used to report the rest of normal events. The experimental results show that the correct detection threshold of single-tone signal decreases by 2dB compared with MFSK signal, and the single-tone and MFSK signal joint communication mode is more advantageous to reduce the probability of incorrect detection.
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