Design of a Low-Profile Broadband Archimedean Spiral Antenna

In this paper, a new design of low profile and ultra- wideband planar Archimedean spiral antenna for airbone application is presented. In order to meet the requirement of low profile of Archimedean spiral antenna in practical application, the spiral antenna is printed on the both side of dielectric substrate symmetrically. This topology eventually reduces the input impedance of antenna by about 50%, and enables the 50Ω coaxial cable direct connect with spiral antenna with low return loss without a microstrip balun. Besides, a Loaded Electromagnetic Band Gap (LEBG) substrates are used as reflector of Archimedean spiral antenna to realize the unidirectional beam. The performance of this antenna has been validated by measurement.