Design of miniaturised printed quadrifilar helix antenna with isoflux coverage and wide‐angle circular polarisation

Abstract In the study, a miniaturised printed quadrifilar helix antenna (PQHA) with isoflux coverage and wide‐angle circular polarisation is presented. It is composed of a three‐stage stepped impedance spiral arm and open stubs. Each of the three‐stage spiral arms has different pitches and number of turns. For the last‐stage spiral arm, meander lines are used. The proposed PQHA features the characteristics of wide bandwidth, isoflux radiation, small size, and wide‐angle circular polarisation. Moreover, in order to feed the proposed PQHA, a miniaturised quad‐feed network is designed to provide equal amplitude signals with sequential orthogonal phases. For demonstration, a prototype is designed, fabricated, and measured. The overall size of the proposed antenna is 88 × 88 × 132 mm (0.44 λ0 × 0.44 λ0 × 0.66 λ0). The results show that isoflux radiation with a coverage of about ±60° is realised from 1.40 to 1.62 GHz (14.6%) while maintaining more than 10 dB return loss and larger than 200° 3‐dB axial ratio beamwidth