用于VLBI测轨的新型Gold码调制PN-DOR信标的设计与仿真

Design and Simulation of a New PN-DOR Beacon Modulated by Gold Code Used in the VLBI

中国VLBI网(Chinese VLBI Network,CVN)在探月工程中采用相对差分单向测距(delta differential one-way ranging,ΔDOR)技术,通过交替观测探测器和邻近致密射电源标校系统误差,以获得高精度的探测器轨道角位置。尽管如此,探测器和射电源信号频谱差异引起的接收设备相位波动仍然是ΔDOR的重要误差来源之一。通过Gold码对DOR信标扩频调制,产生与射电源频谱特性近似的伪随机噪声差分单程测距(pseudorandom noise DOR,PN-DOR)信标,可以有效减少相位波动误差。参考中国探月工程嫦娥五号的VLBI信标参数,设计了PN-DOR信标参数,生成了PN-DOR信标,完成了PN-DOR信标的编码、调制、提取、解调和解码等过程的仿真分析,由于后续探月任务可能出现频谱混叠情况,还研究了频谱混叠对PN-DOR的影响。

Delta differential one-way ranging(ΔDOR)technology is used in the Chinese Very Long Baseline Interferometry(CVN)system in the Lunar Exploration Smission,which can accurately determine angular position of spacecraft by observing the spacecraft radio signal and nearby quasar radio signals alternately.One of the major error sources is the instrumental phase error,caused by the differences between the spacecraft and quasar signal spectrum.It is possible to reduce phase error by spreading DOR beacons with Gold code,which are Pseudorandom Noise DOR(PN-DOR)beacons closely resembling the quasar signal spectrum.In this paper we introduce parameter designs of PN-DOR beacons by referring the parameters of VLBI in the Chinese Chang’E-5 lunar mission,realize PN-DOR beacons,and also finish coding,modulation,extraction,demodulation and decoding of PN-DOR beacons.Finally,the influence of PN-DOR beacons due to spectral aliasing is analysed,because spectral aliasing may occur in the Lunar Exploration mission in the future.