Double-folded Half Wavelength Printed Quadrifilar Helix Antenna with Feeding Network

A method to miniaturise printed quadrifilar helix antenna (PQHA) by reducing its axial length is presented. The axial length reduction is achieved by folding the helical element of the PQHA several times depending on targeted size reduction. As for the feeding network, a compact cascaded power divider network with folded arms is designed to excite each of the antenna helical arm. Comparisons between conventional and double-folded (DF) PQHAs’ reflection coefficient and gain pattern show that this method can achieve nearly 70% of axial length reduction without significantly compromising on its impedance bandwidth and efficiency.