Two-Arm Sinuous Antennas

Two-arm sinuous antennas are introduced in this paper. The proposed configurations and realized phase progressions result in a unique multiband behavior with alternating polarization handedness between adjacent bands. Two sinuous embodiments are presented: a planar, cavity backed, flush mountable design and a unidirectional, conically projected structure. Both designs exhibit multiband and multipolarized performance with low axial ratio and good pattern symmetry. Conical sinuous has superior impedance matching, wider bandwidth for all circularly polarized bands and does not require absorber backing for unidirectional radiation. A computer aided analysis is performed using method of moments and finite element codes and results are favorably compared with measurements.