Research on delay calibration method of VLBI Terminal Device

VLBI (Very Long Baseline Interferometry) Terminal Device is a mixed analog and digital conversion system. Since the analog closed loop can´t be built, the vector network analyzer can´t be used to do delay calibration. In this paper, a delay calibration method of VLBI terminal device based on PCAL (Phase Calibration) signal is proposed. To solve the problem of low computational efficiency of PCAL signal extraction in traditional correlation method, an efficient extraction method based on DFT is proposed which use the special frequency characteristics of PCAL signal. By measuring the practical VLBI terminal device, the effectiveness of this method is verified.