Researches On Time Delay Estimation Algorithm Of The VLBI

The Very-Long-Baseline Interferometry technology, which has been applied in GPSnavigation and positioning of spacecraft for deep space exploration, will be the certaindirection for precise positioning and tracking of spacecraft in the future. In the pastdecade, the major space powers have applied this technology in deep space spacecraftorbit determination test to achieve the positioning accuracy of nanosecond and evenpicosecond. The core algorithm of this technology is Time-Delay Estimation. This paperanalyses the factors affecting the errors in same beam interferometry under thebackground of deep space navigation application. Meanwhile, it also designs time-delayestimation in line with the characteristics of deep-space signals and does performanceanalysis for this algorithm.Focusing on Time-Delay Estimation based on Very-Long Baseline Interferometry,this paper carries out the following work:1) Analyze the time-delay estimation errors arising from the measurement ofvery-long-baseline under the condition of same beam in detail, explain its basicprinciples, and make a quantitative index analysis of influences on the time-delayestimation accuracy from various factors. Especially, have mathematical derivation, testand proof for effects on time-delay estimation caused by earth’s rotation time-delay rate,verify that the impact on time-delay estimation can be negligible with compensation forthe error.2) Research intensively into time-delay estimation algorithm on deep space signalof single-carrier frequency, model the signal mathematically, and derive the CRB ofaccuracy about time-delay-estimation theoretically. Propose super-resolution algorithmof cross-correlation function and fast feasible way for the radio star signal, experimenton the performance of time-delay estimation of this algorithm to prove that theestimation accuracy of this algorithm is almost close to the CRB. Moreover, introducebandwidth synthesis technology for time-delay estimation of spacecraft signal, andconclude that effective signal time-delay estimation can also be achieved with a smallnumber of frequency phase information after making corresponding algorithm performance simulation for this technology.3) Research intensively into time-delay estimation algorithm on deep space signalof multi-carrier frequency, model the signal mathematically, and derive the CRB ofaccuracy about time-delay-estimation theoretically. Work along both lines to achieve thetime-delay estimation of multi-carrier frequency——on one hand, refine the time-delayestimation algorithm on deep space signal of multi-carrier frequency, propose the ideaof using correlation function method to measure signal time delay, as well as avoidambiguity problem caused by direct phase time-delay estimation in phase measurement;on the other hand, map out the multi-carrier frequency configuration of spacecraft,improve the accuracy of signal time-delay-estimation theory. The simulation resultsshow that multi-carrier frequency signal from the design have good autocorrelationcharacteristics, weaker signal periodicity, and is not easy to generate ambiguoustime-delay estimation.