Pattern reconfigurable wideband circularly-polarized quadrifilar helix with broadside and backfire radiation patterns

This paper introduces a pattern reconfigurable wideband circularly-polarized (CP) quadrifilar helical antenna (QHA) with both broadside and backfire radiation modes. A compact 1:4 power divider network is proposed to feed the QHA for obtaining the wide bandwidth. To realize pattern diversity, PIN diodes on the power divider are to reconfigure the sequences of the output phases such that the direction of radiation pattern can be controlled alternatively for the broadside or the backfire radiation. The fabricated antenna prototype is compact and light-weight. Measured results show that the broadside and backfire radiation modes can be switched by applying opposite voltages on the two DC bias. The proposed QHA has the wide impedance bandwidth of 43% and the wide 3-dB AR bandwidth of 38%. The measured broadside and backfire radiations have the wide 3-dB gain beamwidth of 140° and 120° with the maximum gain of 2.3 and 3.0 dBic respectively. The proposed antenna can be used in many applications as subway and railway communications, base station for narrow street coverage, RFID or satellite systems.