A Mechanical and RF Performance Trade-Off for a Deployable Conical Log Spiral Antenna for Spacecrafts

A parametric study on a constant conductor diameter conical log spiral antenna has been performed, providing data for a mechanical and radio frequency (RF) performance trade-off. The antenna is a deployable spring intended for use on spacecraft which will be compressed for launch and released once in orbit. The results show that with a decrease in antenna cone angle the directivity, axial ratio and front-to-back ratio are improved. The antenna impedance increased with decreased cone angle. A lower cone angle results in a larger exerted force upon the spacecraft during antenna deployment. Truncating the tips of the spirals in order to remove the stiffest portion of the spring results in a significant reduction of RF performance and bandwidth, it is thus not recommended as a viable solution.