A high efficiency L-band microstrip antenna

The design of a high efficiency circularly polarized nearly square patch antenna at L-band is presented. One way to improve the efficiency of the inherently low efficiency microstrip antennas is to use substrates with a low permittivity. A low permittivity substrate with /spl epsi//sub r/=1.1028 was obtained by using a combination of Rogers RT/Duroid 5880 and Rohacell hard foam. The effect of a 5 mils thick Rogers RT/Duroid 5880 superstrate on the efficiency was also studied. Results of the antenna efficiency and bandwidth for both the low dielectric substrate and superstrate are presented. The results were obtained using the 1E3D software package and compared with measured results. Efficiencies of the order of 85% for a single patch element were obtained.