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针对VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)系统直接相位差分法的群时延测量精度与分辨率存在矛盾,以及线性最小二乘拟合法不适用于群时延失真链路的问题,采用一种基于非线性拟合的宽带信道群时延测量方法,对出现的问题进行分析与仿真,同时进行了实验验证并获取到实测数据。仿真表明,基于非线性拟合的宽带信道群时延测量方法适用于非线性相位系统,而且群时延的测量精度优于直接相位差分法2个量级。实测数据表明,在270~370 MHz频段内,传统的直接相位差分法和线性拟合测量法已失效,而该方法群时延的测量精度优于0.1ns,由此验证非线性拟合法能够以较高精度进行附加相位和群时延特性测量。
In view of the contradiction between the group delay measurement accuracy and the resolution of the direct phase difference method for Very Long Baseline Interferometry (VLBI) system and the problem that the linear least squares fitting method is not suitable for the group delay distortion link, A method based on non-linear fitting of broadband channel group delay measurement method was used to analyze and simulate the emerging problems. At the same time, experimental verification was carried out and the measured data were obtained. The simulation results show that the method based on nonlinear fitting is suitable for nonlinear phase systems, and the measurement accuracy of group delay is better than that of direct phase difference method. The measured data show that in the band of 270-370 MHz, the traditional direct phase difference method and the linear fit method have failed, and the measurement accuracy of the group delay method is better than 0.1 ns, which verifies that the nonlinear fitting method can Accurate additional phase and group delay characteristics measurements.