Research & Implementation On VLBI Wideband Correlation Technology In Deep Space Exploration

Deep space exploration as one of the three major human space activities in the 21st century has become a hot topic in international space activities. In the activities of deep space exploration, the accurate tracking and positioning of the detector is particularly important. Correlation processing of the downlink radio signal that is transmitted from the detector and collected by deep space exploration can be implemented by VLBI wideband correlation technology, and then the signal’s estimating delay of different observation stations can be obtained, and thereby achieving the goal of accurate positioning the detector. Therefore, researching on VLBI wideband correlation technology applied to the accurate tracking and positioning of the detector is of great significance.This thesis mainly studies wideband correlation technology applied to wideband signal of deep space exploration. The design of VLBI wideband correlation software processor is first carried on. VLBI wideband correlation processing algorithm and design difficulties are deeply discussed, and then three main modules:pre-processing module, data correlation module and the fringe results of the processing module are designed within data processing method and key portions in detail. After that, use MATLAB to accomplish the algorithm design and verify the design of VLBI wideband correlation software processor by simulation signal and the wideband satellite signal、radio source signal collected by RSR. It is showed that the delay estimation error of simulation signal is 10-4ns and the delay estimation error of RSR signal is less than 0.4ns. Then model free VLBI wideband correlation technique to accomplish wideband correlation without time delay prediction is studied. Quick sliding window correlation and LOFAR graph method are designed for quick time delay prediction search, and then signal correlation is implemented by fringe search technique with coarse delay. Afterwards, the processing results of radio sources that is more than 2600KM away from two observation stations obtain a clear interference fringes with time delay estimation error of 0.8ns. Finally, VLBI wideband correlation of heterogeneous receiver based on RSR system and MARK5B system is discussed. Base on the design of heterogeneous receiver correlation algorithm, the key implementation difficulties such as correlation of real signal and complex signal, estimation of delay range and searching of time delay prediction, decoding of heterogeneous receiver signal are studied. Eventually through wideband signal processing, the results of RSR signal and MARK3B signal obtain a clear interference fringes. The result is of great significance for calibration between RSR system and MARK5B system.