Compact Circularly Polarized Archimedean Spiral Antenna for Ultrawideband Communication Applications

A novel compact circularly polarized Archimedean spiral antenna for ultrawideband (UWB) communication applications is presented. The basic structure is a two-arm planar Archimedean spiral antenna, which is fed by a tapered wideband balun. These two arms are extended on the profile and connected together at the end to elongate current path, while four lumped resistors are loaded on them to improve the reflection coefficient at low frequency. A circular reflector with cross slots that consists of one circular slot at the junction of two orthogonal rectangular slots are designed and optimized, which improves the performance of axial ratio (AR). The proposed antenna has a compact size of 36 × 36 × 20 mm
³
. The voltage standing-wave ratio is less than 2.5 in the frequency range of 1.9-8.5 GHz and the AR is less than 3 dB in the frequency range of 2-6 GHz. Both the simulation and measurement results are presented, demonstrating the UWB characteristics of the proposed antenna for wireless communication applications.