Hybrid Applications of RF Lens and Absorbing Material to Optimize the Radiation Patterns of Four-arm Spiral Antennas in the Direction Finding System

Abstract

The broad radiation patterns of the four-arm spiral antenna can potentially cause difficulties in the practical direction finding applications. For example, the patterns might be interfered with multi-path signals, which will cause errors in the angle estimation, when installed in an aircraft structure. This paper proposes a hybrid application of RF lens and absorbing materials to optimize the radiation patterns so that the antennas may retain their advantageous characteristics in the applications of direction finding system. The characteristics of the impact on the angle estimations with this hybrid structure will be examined by numerical simulations and validated by experimental measurements.