Fast circuit model for interaction of open-ended rectangular waveguide probes with arbitrary-shape surface cracks in metals

The study proposes a fast modelling technique to predict output signal of an open-ended rectangular waveguide when scanning an arbitrary-shape surface crack in a metal. In this technique, the crack is first segmented into an appropriate number of short rectangular waveguides each of which is modelled by a two-port network with an equivalent RLC circuit. The generalised scattering matrix technique is then used to predict the probe output signal. The efficiency of the proposed model is demonstrated by comparing the simulation results of several case studies with measurements and those obtained using the mode-matching method and a commercial finite integration technique code.