Gap-coupled stacked microstrip antenna for dual band operation

Theoretical investigations of a gap-coupled stacked microstrip antenna is presented using equivalent circuit concept. It is found that the antenna operates with dual frequency band characteristics with resonances at 4.76 GHz and 6.79 GHz. The dual nature of the antenna is realized by adding coplanar U-shaped parasitic elements around the radiating edges of the fed patch and stacking a rectangular patch above them. The lower and upper frequency bands are achieved as 443 MHz and 287 MHz respectively. The radiation patterns show shifts of 5deg towards left and 12deg towards right for lower and upper resonance frequencies respectively.