A simple two-port model for an active printed board antenna element

We present a simple 2-port model for the analysis of the stability and radiation characteristics of an active printed board receive-transmit element. The model is then used to analyze the stability, pattern and polarization characteristics of a special microstrip circular patch. The patch with two orthogonal mode excitation works as a transmit-receive element for circularly polarized waves. Comparisons with experiments are also presented.