Wide-band microstrip patch antennas using parasitic elements and defected ground structures on different substrates

In this paper, a microstrip antenna composed of a square patch with mitred corners on a low dielectric substrate together with two smaller square parasitic patches on a substrate with high permittivities is introduced, which tends to reduce the size of the antenna, generate circular polarization and increase the frequency bandwidth. The high permittivity substrate under the parasitic patches causes strong surface waves to appear on the antenna and decrease its radiation efficiency. Defected ground structures are made to counter the generation of surface waves and also reduce the size of microstrip antenna. This antenna with favourable characteristic is presented for applications in mobile systems.