Resolution improvement method for non-destructive imaging with near-field scanning microwave microscopy

In this paper we report a resolution enhancement method for non-destructive imaging application with near-field scanning microwave microscopy (NFMM). The technique proposed for the image processing is based on the combination of the position/signal difference (PSD) method and an adaptive robust statistical (ARS) method. The NFMM, is built up with a vector network analyzer (VNA), an evanescent microwave probe (EMP), a high resolution motorized XYZ stage, and a data acquisition system. Thanks to the broadband matching network based on an interferometric technique, the electromagnetic coupling between the probe and sample can be adjusted to guarantee a high measurement sensitivity at any frequency from 2 to 18 GHz. Experimental results demonstrate that the proposed resolution enhancement solution can effectively correct the distortion caused by multiple parameters such as measurement noise and tilt errors of the sample. The post-processing technique associated to the microwave instrumentation result in an improvement of spatial resolution for non-destructive evaluation.