Simulation design of four-arm cavity backed dielectric loaded UWB spiral antenna

This article analyses a novel 4-arm spiral antenna operating in the 2nd mode. The CST MICROWAVE STUDIO^reg (CST MWS) is extensively used to study effects of various antenna parameters. Good performance over four octave bandwidth is achieved in terms of angular phase linearity, axial ratio, and wobble on wave (WoW). The total cumulative phase is 720 degrees for mode 2 pattern at the assigned elevation. Phase linearity over the entire bandwidth is well maintained. The standard deviation of phase is controlled within design requirement.

I. INTRODUCTION

Spiral antennas are inherently of frequency-independent characteristics. So they are widely used as circularly polarized broadband devices for airborne RF applications, mobile communications, early warning, direction finding, and other applications. Their wide impedance and pattern bandwidth allows multiple communication services such as GPS, PCS, and SDARS to be integrated into a single aperture system. Because of the front-to-back symmetry, spiral antenna in free space radiates bi-directionally. Therefore, for most applications, where unidirectional operation is required, the spiral is backed by an absorber-loaded cavity. This eliminates back-side radiation without decreasing the frequency band of operation but at the cost of efficiency reduction. In this paper, we give a new cavity backed spiral antenna, which is backed by a complex cavity. The cavity backed antenna can give a nice phase linearity and small WoW over the whole frequency band.