Research Of Carrier Capture And Tracking Technique Of Deep Space Transponder

Since 21st century,the exploration of deep space has been set as national strategy by many countries.And deep space transponder which serves for the bi-direction communication between spacecraft and ground control is the lifeline,it’s a very important par’t of the exploration of deep space absolutely.The primary difficulty of deep space communication is carrier capture and tracking under extremely low C/N0 conditions.In this dissertation,the primary difficulty is deeply analyzed,and a solution to this primary difficulty is presented.The research contents and findings are as follow.Firstly,the carrier pre-capture technique is based on FFT computation.But the result of FFT computation will deteriorate by Doppler shift in the condition of extremely low C/N0.Consequently,a frequency domain compensation algorithm which improves the result of FFT computation is given in the dissertation.Furthermore,considering that the resource of FPGA device is limited,an iterative frequency domain compensation algorithm is proposed.Secondly,a three order phase locked loop technique is proposed for carrier tracking.The three order phase locked loop can achieve stable performance of phase error.And a self-adaptive loop switching mechanism is proposed for adapting to different task scenarios.Finally,the carrier capture and tracking technique is implemented on FPGA.According to the test validation,the carrier capture sensitivity of deep space transponder is better than-155dBm.