An improved frequency-domain algorithm for stable reduction to the pole at low latitudes

Abstract

Based on a modification of the routine of the reduction-to-the-pole (RTP) operator in the frequency domain, the approaches of local suppression and global suppression perform well in suppressing the unstable amplification zone for low-latitude RTP. However, additional parameters are inevitably introduced whose values exert a direct effect on the accuracy of the RTP. In this paper, these introduced parameters are optimized by calculating the correlation coefficient between the RTP results and the normalized source strength (NSS), then the RTP results under the optimal parameters can be obtained. Furthermore, an improved regularization algorithm is proposed and applied to the optimized operators to resolve the problem of the high-frequency amplification effect existing in these operators. The results of a simulation and principal verification experiment prove that the proposed method cannot only taper off the high-frequency noise in the original signal but also improve the stability of the low-latitude RTP effectively.