Distributed Lumped Loads and Lossy Transmission Line Model for Wideband Spiral Antenna Miniaturization and Characterization

A lossy transmission-line model that incorporates the radiation resistance of small loop antennas is introduced to characterize the input impedance of a spiral antenna over a large frequency range. This model also leads to a concept of controlling the current velocity and impedance on a spiral antenna by introducing distributed reactive loading along the spiral arms. An important application of the concept is to reduce antenna size and this is demonstrated by numerical simulation examples.