Dual Band Circular Polarized Microstrip Antenna Using Defected Ground Structure

A slit cut square microstrip antenna with corner truncated defected ground structure is reported for dual band circular polarized response. The reported configuration yields bandwidth of 7.5% and 2.9 % respectively at lower and upper band. It also reported AR bandwidth of 40 MHz and 11MHz for lower and upper band, however the reported work does not provide in depth analysis of resonant modes responsible for dual band circular polarized response. The present paper gives in depth analysis using resonance curves and surface current distributions for dual band circular polarized response for reported configuration. From parametric investigations done it is detected that slit dimensions on main patch and defects created in ground plane using rectangular slot and truncated corners modifies the TM10, TM01, TM11 modes of main patch that yields dual band with circular polarization. Further optimization of same configuration is done on FR4 yielding impedance band width of 1.1 % and 1.3% for lower and upper band. It also results in AR band width of 7.8 % and 0.8 % for lower and upper band.