Mutual impedance between bifilars of a quadrifilar helix antenna

In this paper we present the results of a study to quantify the mutual coupling between the two bifilars of a 1/2 turn 1/2 wavelength quadrifilar helix antenna (QHA). A new circuit model approach is used which is suitable for computing the impedance when the structure is fed by a single voltage source as in the case of a self phasing QHA. The validity of the circuit model is first confirmed by comparisons with simulated results obtained from the literature for various configurations of parallel fed dipoles.