Circularly polarised wire antenna with a dual rhombic loop

Abstract

A single feed wire antenna with a dual loop configuration for circular polarisation is proposed. The dual loop consists of two rhombic loops of the same size, and is located above a ground plane. Each loop has a gap, and the two gaps are located symmetrically with respect to the feed point. Two types of feed can be considered because of the combination of the loops, Antenna characteristics are calculated by the method of moments, and compared with measured data. By adjusting the perimeter, the rhombus vertex angle and the gap position of the loop, axial ratio bandwidths (/spl les/2 dB) of more than 20%, and gains of more than 10 dBi are obtained for the two types of feed. In addition, it is observed that the sense of circular polarisation can be changed easily from left-hand to right-hand, and vice versa, by switching the feed types or gap positions.