【作者】 张儒源； 詹亚锋； 戴晓洁； 陆建华；

【Author】 Zhang Ruyuan;Zhan Yafeng;Dai Xiaojie;Lu Jianhua;Department of Electronic Engineering,Tsinghua University;Space Center,Tsinghua University;

【机构】 清华大学电子工程系； 清华大学宇航中心；

【摘要】 深空通信中探测器距离遥远,同时星载发射机功率受限,导致地面接收信号非常微弱。此外探测器高速飞行,具有很大的径向速度及径向加速度,使得接收信号中产生了严重的多普勒频偏及频偏变化率,尤其是后者给信号的可靠捕获及后续解调译码带来极大挑战。为此,本文采用了锁频锁相环加联合解调译码接收机的设计思路:结合锁频环动态跟踪范围大以及锁相环跟踪精度高的优点,精确跟踪信号的动态多普勒频偏;再将去除动态频偏后的信号送入联合译码接收机。仿真结果表明:发送端采用1/5码率LDPC编码,在动态多普勒频偏为传输速率0.01倍时,本文方案能够稳定工作在E_b/N_O=1.2dB,与理想条件下LDPC的译码门限相比仅损失约0.2dB。更多还原

【Abstract】 In deep space communications,the limited transmission power and long distance between the spacecraft and ground stations result in very low SNR for the receiver.Moreover,target vehicle’s high-speed moving which has large radial velocity and acceleration would bring severe Doppler frequency offset and acceleration to the downlink signals.All of these make much trouble for signal acquisition,demodulation and decoding.In this letter,a novel design idea of combining the frequency and phase lock loop with iterative receiver is proposed.Since the frequency lock loop(FLL) could offer large dynamic range and phase lock loop(PLL) has the advantage of high accuracy,FLL is adopted to assist PLL for tracking dynamic Doppler frequency.Then joint iterative demodulation and decoding technology is introduced to lower the demodulation threshold of sub-carrier signals.Simulation results show that our algorithm of 1/5 LDPC code can work under E_b/N_O=1.2dB and the Doppler frequency acceleration of one percent of the transmission rate with a performance degradation of only 0.2dB.更多还原