A new model for calculating the input impedance of coax-fed circular microstrip antennas with and without air gaps

Abstract
A model is presented for calculating the input impedance of a probe-fed circular antenna with and without air gaps between the substrate and the ground plane. It is based on the cavity method, the dynamic permittivity constant (to take into account the influence of the fringing field at the edge of radiating element), and the resonant parallel R-L-C circuit with an inductive reactance. Numerical results are shown to agree well with experimental ones. The model is well suited for computer-aided design.

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