宽带干涉测量通道群时延非线性误差标校

Calibration of channel group delay nonlinearity error applied in wide-band interferometry

以Ka频段宽带干涉测量为背景,分析了通道群时延的主要表现形式。针对通道宽带群时延非线性失真问题,提出了基于相位校正信号互相关的标校方法。利用相位标校信号梳状谱和线性相位特性,通过提取相位标校信号的互相关相位谱获取通道的相频特性曲线,并以此计算通道的群时延。针对抛物线型群时延,采用三阶非线性拟合代替传统的一阶线性拟合。仿真结果表明,在信噪比为-10dB的条件下,三阶拟合比一阶拟合与原始相频特性曲线有更高的吻合度,且标准差为一阶拟合的1/4,得到的群时延结果逼近真实群时延,证实了算法的有效性。

The form of wide-band group delay is analyzed and Ka-band interferometry is taken as the back- ground. For the problem of nonlinear distortion of channel group delay, a calibration method based on cross-correlation of phase calibration （PCAL） signals is proposed. Comb-spectrum and linear phase are key characteristics of PCAL, according to this, the phase-frequency characteristic curve of cross-correlation is obtained by extracting PCAL＇s phase, and then the channel group delay is calculated. For parabolic group delay, third-order nonlinear fitting is used to replace the traditional first-order linear fitting. Simulation results show that when the signal-to-noise ratio is -10 dB, the third-order fitting has a higher agreement with the original phase-frequency characteristic curve, the standard deviation accounts for 1/4 of the first-order fitting and the group delay result is closer to the true value. The validity of the algorithm is proved.