Spectral domain analysis of a proximity feed polarimetric microstrip antenna

As a form of feeding the microstrip antenna, there is a method of exciting the patch via a gap from the semiinfinite feed line. In this scheme, the polarization plane can be switched by changing the stub length. Due to the effect of the feed line on the input and polarization characteristics and to the expected strong coupling by the surface wave through the gap, the rigorous analysis by the conventional method has not been possible. In this paper, the operating principle of the present model is presented. In addition, a model of the current basis on the feed line is proposed including the scattering by the patch. Further, by means of the spectral domain method, the input and polarization characteristics are analyzed rigorously. The behavior of the polarization is shown analytically when the frequency and the stub length are varied.