Wideband cavity backed spiral antenna for stepped frequency ground penetrating radar

A 1.7 turn cavity backed coplanar waveguide to coplanar strip-fed logarithmic uniplanar spiral antenna is presented and compared to a 1.5 turn spiral antenna. The 1.7 turn spiral antenna has a wide beamwidth, are circular polarised and has a bandwidth with a return loss better than 6 dB in the frequency band from 0.25 GHz to 4.5 GHz (18:1). The antenna is useful for ground penetrating radar (GPR)