针对突发GMSK信号的侦察,设计了一种多速率GMSK全数字化盲解调器。首先通过符号率粗估计和抽取滤波将不同符号率信号降采样为固定过采样倍数的数据,运用乒乓缓存结构将不同突发数据包区分处理,然后采用无训练序列的前向载波恢复算法和定时同步算法保证解调的实时性,最后通过1比特相位差分加Viterbi译码进行符号判决。Matlab软件仿真结果表明了算法的有效性,FPGA硬件测试结果进一步验证了该解调器方案的可行性。
The receiver with full-digital and forward structure for burst-mode GMSK signal with multiple symbol rates is designed. Firstly, the received signal is down-sampled on the basis of symbol rate estima- tion, signal extracting and filtering. A Ping-pang RAM structure is used to separate the adjoin burst data package, and then a forward estimation algorithm without preamble is adopted to implement carrier recovery and symbol timing in the real-time GMSK demodulation. Finally, a Viterbi decoder based on 1-bit differen- tial phase detection is designed to recover the information bits. Both the computer simulation with Matlab and the on-line testing results based on FPGA platform verify the feasibility of the proposed receiver.