A rigorous analysis of planar antennas having a finite size substrate

This paper gives an extended approach for microstrip antennas and circuits having nonhomogeneous and finite size substrate. The formulation combines the method of lines and the Green´s function concept; it includes also a rigorous description of the feeding generator and the matched load termination, which are introduced as additional boundary conditions and used to calculate the scattering parameters for multiport antennas and circuits. The numerical characterization follows the same calibrating steps as the network analyzer. The proposed technique is applied to investigate the influence of the finite size substrate on the propagation characteristics and the scattering matrix parameters of radiating microwave structures. The obtained theoretical results of a microstrip antenna are compared with our measurements and a good agreement is observed.