Two-Arm Archimedean Spiral with Filter-Based Reactive Loading

Abstract

A new technique to increase the operating bandwidth of a two-arm Archimedean spiral antenna is presented in this paper. Unlike other conventional solutions, including absorbent cavity backing and resistive loading, this method incorporates the concept of low-pass filtering with the two-wire transmission line behavior of the spiral antenna. The reactive loading from the integrated low-pass filter design improves the impedance match at lower frequencies providing a greater bandwidth than the basic spiral design