Analysis of an aperture coupled microstrip patch antenna with a thick ground plane

The aperture coupled microstrip patch antenna was proposed in Pozar (1985) to alleviate the difficulties of feeding printed antennas operating at millimeter wave frequencies. This geometry has subsequently been analyzed by a number of researchers using various techniques and models. The addition of a thick ground plane to the aperture coupled patch antenna, proposed as a heat sink for active MMIC circuitry and a mechanical support for thin substrates, has been analyzed using a time domain analysis (Takeuchi et al. 1993). A disadvantage of the thick ground plane is that the decay in coupling to the patch increases with ground plane thickness due to the fact that the thick slot acts like a waveguide below cutoff. A subsequent increase in slot length to compensate for the preceding tradeoff could potentially increase unwanted back lobe radiation. The aperture coupled patch antenna with a thick ground plane is analyzed in the present paper using the reciprocity method with a full-wave moment method analysis in the spectral domain. The tradeoff of coupling vs. ground plane thickness is studied through calculated and measured results.<>