Dual band circularly polarized off-centered EMCP antennas

Stacked electromagnetically coupled patches (EMCP) have been used for broadband and dual frequency operations. Wide bandwidth can be obtained by selecting the sizes of the two stacked patches such that the two resonant frequencies are close to each other. If the resonant frequencies of the two stacked patches are far apart, dual frequency operation is obtained. When lateral shift is given along the feed axis, it has been reported that the lower resonance frequency decreases and the upper resonance frequency increases. An off-centered stacked circular microstrip antenna along /spl plusmn/45/spl deg/ axis from the fed patch has been investigated for broadband, dual frequency and circularly polarized operations.