Broadband Archimedean spiral antenna above a loaded electromagnetic band gap substrate

The development of a low profile, lightweight, broadband spiral antenna for airborne applications is described. The use of an electromagnetic band gap substrate with loads as reflector for an Archimedean spiral antenna is proposed. A method based on a transmission line model is presented to design this loaded electromagnetic band gap substrate. Simulation and measurements results demonstrate the applicability of the concept. A good impedance matching as well as a good circular polarisation are achieved over a 10:1 frequency bandwidth. Finally, thickness and weight of this new antenna are greatly reduced and their performances are better compared with a conventional spiral antenna with unidirectional beam