Design and performance of an ultra wideband ceramic-loaded slot spiral

There is a significant interest in the commercial and military sector for antennas which are smaller and broadband. The paper is the first, to the authors´ knowledge, that pursues miniaturization of broadband antennas using high-contrast materials (ε_r>20). Specifically, we present analysis and measurements of a slot spiral antenna loaded with ceramic materials and demonstrate that a 6 inch aperture can operate down to 70 MHz and up to 4 GHz or more. A previously developed spiral antenna (Filipovic, D.S. and Volakis, J.L., IEE Proc. Microwaves, Antennas and Propag., vol.149, no.2, p.98-105, 2002) is used as a starting point and, prior to ceramic loading, the spiral is first modified and improved to allow for effective utilization of a ceramic superstrate. First, improvements on the existing slot-spiral are outlined and then data for the dielectrically loaded spiral are presented.