To increase the radiation efficiency and broaden the operation bandwidth, an aperture-coupled microstrip antenna of high temperature superconductor with multi-layer substrates is designed.

In this paper, the equations for calculation of the radiation performances on high efficiency double reflector antenna fed by beam waveguide are derived.

Using this model and the relevant dyadic Green's function, some characteristics of a rectangular patch antenna near resonance, such as radiation resistance and space wave efficiency, are analysed.