Folded loop C.P. antenna

A new type of wire loop antenna has been developed for the production of circular polarization. The antenna was obtained by twisting a one-wavelength square loop with two small gaps at the middle of its two non-radiating sides. The twisted loop antenna can achieve circular polarization with axial ratio less than 1 dB at broadside. The 3-dB axial ratio beamwidth is about /spl plusmn/30/spl deg/, over which the co-polarization component is almost constant. In addition, the antenna also has excellent input impedance characteristics over the 3-dB axial ratio bandwidth. The input VSWR is about 1.2 near the design frequency.