Coplanar waveguide ground potential imbalance as a source of useful signal in near-field scanning microwave microscopy

Various techniques are available in order to obtain information on samples of a different nature in near-field scanning microwave microscopy (NSMM), with transmission-line resonator (TLR) techniques considered the most advanced in terms of sensitivity and resolution. In this paper, we focus on the development of TLR-based NSMM supplied by a new source of useful signal: coplanar waveguide ground potential imbalance. Electromagnetic modeling of the device and experimental scanning of two planar structures are conducted to examine the performance of the proposed technique. Both modeling and experimental results demonstrate the ability to distinguish symmetric inhomogeneity positions with respect to the central conductor of the coplanar waveguide by the phase of the imbalance signal. The thin-film structure scanning procedure displays the possibility of the proposed approach to resolve low-contrast structures with an accuracy of up to 98.7%.