The CFIE technique applied to finite-size planar and non-planar microstrip antenna

Planar microstrip antennas are predominantly modelled via method of moments (MoM) schemes based on the assumption that the substrate layer, or layers, and the ground plane are of infinite extent. This assumption allows the use of a modified Green´s function so that only the printed metal of the transmission lines and patches need be modelled which significantly reduces the number of unknowns to be solved. For finite size planar and non-planar antennas no such assumption can be made and the structure is required to be modelled as a 3D conductor and dielectric scatterer. A MoM scheme based on the combined field integral equation (CFlE) is used to model such structures. The paper discusses the discretisation and the feed model needed to achieve good agreement with measurements of the input impedance of microstrip antennas