Experimental studies of circularly polarized printed square spiral slot antennas

A simple design for a circularly polarized printed square spiral slot antenna is presented. The printed slot antenna has a square spiral slot of about 1.25 turns, whose total slot length is approximately one free-space operating wavelength. Simply by trimming at the end point of the square spiral slot, circular polarization (CP) operation with a wide operating bandwidth can easily be achieved. The CP bandwidth can be enhanced when a proper width of the square spiral slot is chosen. Much wider CP bandwidth about 11% is also obtained for the proposed antenna incorporating the sequential rotating technique.