Characteristics of aperture-coupled coplanar microstrip subarrays

The characteristics of aperture-coupled microstrip antennas with parasitic elements are studied. Four configurations for increasing the bandwidth of aperture-coupled microstrip antennas are described. Additional patches are gap-coupled to the nonradiating edges of the rectangular fed patch. The spectral domain Green function approach and the reciprocity method are used for the analysis. The SWR bandwidth and the E- and H-plane beamwidths can be improved by changing the sizes and the locations of the parasitic patches. Low backlobe radiation can be achieved by locating a plane reflector slightly below the microstrip feedline. The bandwidth of the microstrip subarray can also be enhanced with the addition of the plane reflector. The theory is confirmed by experimental data.