Wideband Spiral Antenna with Superstrate Designs for Radio Altimeter

A novel wideband log spiral antenna with superstrate design is proposed for C-band applications. Initially spiral antenna is designed on a 20.4 mm diameter then Minkowski fractals are placed on outer boundary of spiral antenna. The bandwidth of an antenna is improved using Minkowski fractals. Further one more single layer is added as a superstrate design which making the radiation pattern unidirectional. The single layer spiral antenna with fractals has return loss bandwidth of 0.59 GHz and fractional bandwidth of 11.98% where as double layered spiral antenna has return loss bandwidth of 1.34 GHz and a fractional bandwidth of 27.50%. The proposed antennas have a gain varying in the range of 2.5 to 4.64 dBi over the operating frequency band for both the single layer spiral antenna and double layer (superstrate) spiral antenna.