Miniature Folded Printed Quadrifilar Helical Antenna with Integrated Compact Feeding Network

A miniature folded printed quadrifilar helical antenna (FPQHA) using a novel compact feeding network is proposed. Folding and meandering techniques are used to obtain 66% of size reduction for the axial length of the printed quadrifilar helical antenna. A compact feeding network using an out-of-phase power divider based on double-sided parallel-strip lines and a Wilkinson power divider is designed. A fabricated prototype of the FPQHA employing the compact feeding network is presented. The measured positive gain bandwidth is from 380 MHz to 425 MHz with a reflection coefficient less than -20 dB and an axial ratio below 2 dB. The measured maximum gain is 3.08 dBic at 395 MHz with a half-power beamwidth of 150 degrees. With good radiation performance and integrated feeding network, the proposed antenna can become a better candidate in satellite and mobile communications.