Validation of Physics-Based Circuit Model For Multiport Microstrip Antennas Using DCIM

The previously proposed circuit model for general planar antennas of arbitrary geometry is extended to antennas over microstrip substrates. Using discrete complex image method (DCIM) together with matrix pencil technique, the microstrip dyadic green's function is modeled analytically and used for characteristic mode analysis (CMA) and field calculation of arbitrary microstrip antennas. The characteristic modal responses are then used as the basis to expand antenna input responses at arbitrary feed positions. A 2-port antenna system is numerically investigated to validate the extended circuit model, and illustrate its utility for antenna feed placement and input parameter visualization.