高码率SOQPSK接收机的低时延解调和快速同步设计

Low-delay Demodulation and Fast Synchronization Design of High Bit Rate SOQPSK Receivers

针对遥测信号——成形偏移正交相移键控的高码率接收时序设计难度大的问题,提出了一种低时延解调及其快速同步设计方案。结合互相关网格编码正交调制(Cross-Correlated Trellis Coded Quadrature Modulation,XTCQM)技术,提出了一种四进制维特比(Quaternary Viterbi,QViterbi)译码模型,相比现有方案译码时延降低了1/3。为降低同步捕获时长,针对XTCQM-QViterbi解调,设计了一种基于早迟门的符号定时和面向判决的载波相位联合同步方案。仿真结果表明,同步理想时XTCQM-QViterbi解调信噪比损失几乎可以忽略不计;恒定载波、定时相偏场景下,联合同步方案引起的信噪比损失约0.3 dB(误码率为10-5),捕获时间约为1000 T_(b)(T_(b)为比特周期)。该方案具有译码时延短、同步精度高、捕获快等优点。

For the difficulty of high bit rate reception for shaping offset quadrature phase shift keying(SOQSPK),a kind of telemetry signal,a low-delay demodulation along with the synchronization design scheme is proposed.By combining with cross-correlation trellis-coded quadrature modulation(XTCQM)technology,a quaternary Viterbi code(QViterbi)model is proposed,which reduces the decoding delay by 1/3.To reduce the capture time,a joint synchronization scheme combining timing synchronization scheme based on early and late gate symbol and decision-directed carrier phase synchronization scheme,is designed for XTCQM-QViterbi demodulation.Simulation results show that the signal-to-noise ratio(SNR)loss of XTCQM-QViterbi demodulation is almost negligible when synchronization is ideal,and SNR loss from joint synchronization is about 0.3 dB when the deviation of timing and carrier frequency is constant,while the capture time is about 1000 T_(b) where T_(b) is the bit period.The scheme has advantages of less time delay,high synchronization accuracy,and fast capture speed.