Axial Ratio Improvement of Spiral Antenna with Resistive Loading

Abstract

Abstract Spiral antenna belongs to the class of frequency independent antenna. It radiates circularly polarized wave bidirectionally. Due to the finite size of the antenna, the performance at the lower frequency degrades. This could be accounted to the reflection of the current from the truncation. Wide band characteristics from 300MHz to 3.5GHz are able to achieve through the partial resistive loading of the antenna. The lower frequency 3dB axial ratio has been improved significantly from 600MHz for the unloaded case to 200MHz for the loaded case without much effect on the efficiency. At 300MHz, the efficiency is around 60% and axial ratio at within 3dB range.