In order to increase the bandwidth of a typical printed quadrifilar helix antenna (PQHA) from 5 % to approximately 30 %, a shorted parasitic strip may be added to each arm. The parasitic strip is folded down from the main radiating strip and shorted to the groundplane at the base of the helix, resulting in a printed folded QHA (PFQHA). This increase in bandwidth might allow the structure to be used in satellite, ground station or GPS applications, where the narrow bandwidth of the standard QHA may have been a limiting factor.
The PFQHA radiates a circularly polarized, cardioid shaped radiation pattern. By proper choice of the helical parameters, half-power beamwidths of up to 180°, high front-to-back ratios and good circular polarization are simultaneously obtainable...Typical gain at 0.85fc, fc and 1.15fc Typical reflection coefficient versus frequency