一种双环路高动态QPSK载波跟踪器设计

A dual-loop structured QPSK carrier tracker for high-dynamic applications

针对低轨卫星正交相移键控(QPSK)连续波通信,提出一种在高动态环境下载波频率的跟踪方法。采用双环路载波跟踪机制,其中外部环路用于频偏牵引,减少较大频偏引起的匹配滤波器频谱截断失真;内部环路用于精确解调数据,能稳定跟踪含有加速度≤30g的信号。采用加速度补偿方法,解决在百毫秒级中断间隔情况下,残余频偏造成匹配滤波器相位突变的问题。该方法能够快速准确地消除高动态载波频偏,在信噪比为10 d B时经上板测试误码率小于10-5量级。采用FPGA+DSP实现架构,开发敏捷,应用灵活,性能可靠。

A method of tracking carrier frequency in high dynamic environment is proposed for Quadrature Phase Shift Keying(QPSK)continuous wave communication of Low Earth Orbit(LEO)satellite.Using dual-loop carrier tracking mechanism,the external loop is utilized for frequency offset traction,which can quickly reduce the large frequency offset caused by the matched filter cutoff spectrum distortion;the internal loop is utilized for accurate data demodulation,which can stably track the signal containing the acceleration less than 30g.The method of acceleration compensation is adopted to solve the problem of the phase mutation of the matched filter caused by the residual frequency deviation in the millisecond interval.This method can eliminate the high dynamic carrier frequency offset quickly and accurately.When the Signal to Noise Ratio(SNR)is 10 dB,the error rate of the terminal is less than 10-5.Using digital Field Programmable Gate Array+Digital Signal Processor(FPGA+DSP)implementation framework,the method is flexible,reliable and agile for development.