【作者】 张润峰；

【导师】 张尔扬；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2007， 硕士

【摘要】 TDRSS高速数传对数据传输速率的要求不断提高,通信系统必然需要采用更高阶的调制样式和更高效率的编码方式,在功率和带宽同时受限的情况下,低信噪比条件下的载波恢复问题亟待深入研究和解决,否则将成为信号接收和解调的瓶颈。本文简要分析了各种调制方式特别是TCM-8PSK信号的解调信噪比门限,提出了低信噪比条件下载波恢复这一命题;重点研究了低信噪比条件下载波恢复参数估计算法,并提出改进方案以降低信噪比门限;最后基于Xilinx公司的Virtex-Ⅳ系列FPGA设计了TDRSS高速数传8PSK数字接收机的载波恢复系统方案。分析结果表明:改进后载波频偏估计的信噪比门限降低到5dB左右,该载波恢复系统在6dB信噪比条件下工作良好,能够满足TCM-8PSK在6dB条件下实现10^-5误比特率的性能要求。更多还原

【Abstract】 The request of high speed data transmission in TDRSS （Track and Data Relay Satellite System） to transmission rate continuously rises. Communication systems have to adopt higher-alphabet-size modulations and more-efficient codes. When the power and bandwidth is limited at the same time, carrier recovery in low-SNR （Signal Noise Ratio） condition is one of problems which need to be researched and solved, otherwise it will be a bottleneck to signal receiving and demodulating.Firstly, the SNR threshold of different modulations especially of TCM-8PSK is analyzed, and the problem of carrier recovery in low-SNR condition is put forward. Then, parameter estimation algorithms in carrier recovery are researched, and an improved project is proposed to reduce the SNR threshold. Finally, based on the FPGA of the Virtex-IV series of Xilinx company, a carrier recovery system in 8PSK digital receiver for high speed data transmission in TDRSS is designed.Simulation result indicates that: The SNR threshold of the improved carrier frequency offset estimation algorithm is reduced to be as low as 5dB. The carrier recovery system proposed can work well under the situation of 6dB SNR, and the request that the BER performance comes down to 10^-5 in 6dB SNR condition for TCM-8PSK signal can be satisfied.更多还原