Design, analysis and construction of an Archimedean spiral antenna and feed structure

To aid in the antenna design, the Electromagnetic Surface Patch Code (ESP) was used to predict the spiral's performance in terms of radiated pattern and input impedance over the two-octave region between 2.5 and 10 GHz. The spiral and feed structure were constructed and the measured results were compared to the predictions from ESP. In general, it is found that ESP is a reliable method of obtaining impedance information as long as frequencies are chosen low enough that the thin-wire approximation used in ESP (i.e. that the radii of all wires in the structure remain less than 0.1 lambda ) is not violated.<>