Printed backfire wideband circularly polarised tapered gap loop antenna

Abstract

A new type of broadband printed loop antenna is presented. The antenna produces backfire linearly polarised signals over a wide band of frequencies 1.2 to 2.2 GHz, with <3 VSWR. The front-to-back ratio of the antenna is 22 dB; its on-axis cross-polarisation level is around -25 dB at 1.5 GHz and is better than -16 dB; over the entire frequency band. Backfire radiation is achieved by using a novel wide printed rectangular loop radiating element with integral tapered gaps. These gaps provide the phasing necessary for the radiating elements of the antenna to enable backfire radiation in the plane of the loop. Two such printed tapered gap loops are arranged in an orthogonal configuration to produce broadband circularly polarised radiation. Here for a VSWR &LE; 3 the bandwidth is more than an octave (1.1 to 2.4 GHz) with an axial ratio of <4 dB. Simulated and measured results are presented for both configurations.