Feng Qingqing, Xu Huaping, Wu Zhefeng, You Yanan, Liu Wei, Ge Shiqi
School of Electronic and Information Engineering, Beihang University, Beijing 100191, China.
Electronic and Electrical Engineering Department, University of Sheffield, Sheffield S1 3JD, UK.
Sensors (Basel). 2016 Nov 23;16(11):1976. doi: 10.3390/s16111976.
The quality of an interferogram, which is limited by various phase noise, will greatly affect the further processes of InSAR, such as phase unwrapping. Interferometric SAR (InSAR) geophysical measurements', such as height or displacement, phase filtering is therefore an essential step. In this work, an improved Goldstein interferogram filter is proposed to suppress the phase noise while preserving the fringe edges. First, the proposed adaptive filter step, performed before frequency estimation, is employed to improve the estimation accuracy. Subsequently, to preserve the fringe characteristics, the estimated fringe frequency in each fixed filtering patch is removed from the original noisy phase. Then, the residual phase is smoothed based on the modified Goldstein filter with its parameter alpha dependent on both the coherence map and the residual phase frequency. Finally, the filtered residual phase and the removed fringe frequency are combined to generate the filtered interferogram, with the loss of signal minimized while reducing the noise level. The effectiveness of the proposed method is verified by experimental results based on both simulated and real data.
干涉图的质量受各种相位噪声的限制，会极大地影响合成孔径雷达干涉测量（InSAR）的后续处理过程，如相位解缠。因此，对于InSAR地球物理测量（如高度或位移）而言，相位滤波是必不可少的一步。在这项工作中，提出了一种改进的戈德斯坦干涉图滤波器，用于在保留条纹边缘的同时抑制相位噪声。首先，在频率估计之前执行所提出的自适应滤波步骤，以提高估计精度。随后，为了保留条纹特征，从原始噪声相位中去除每个固定滤波块中的估计条纹频率。然后，基于改进的戈德斯坦滤波器对残余相位进行平滑处理，其参数α取决于相干图和残余相位频率。最后，将滤波后的残余相位和去除的条纹频率相结合，生成滤波后的干涉图，在降低噪声水平的同时使信号损失最小化。基于模拟数据和真实数据的实验结果验证了该方法的有效性。
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