A Quadruple-Polarization Reconfigurable Feeding Network for UAV RF Sensing Antenna

A quadruple-polarization reconfigurable feeding network for an unmanned aerial vehicle (UAV) RF sensing antenna operating at 915 MHz is presented. It consists of one single-pole four-throw (SP4T) switch, one 90° hybrid coupler, two 180° hybrid couplers, and two single-pole double-throw (SPDT) switches. By controlling the SP4T and SPDT switches, quadruple polarizations with two linear polarizations (vertical and horizontal) and two circular polarizations (right-hand and left-hand) were obtained. The proposed reconfigurable feeding network with quadruple polarization modes in the 902–928-MHz range has an insertion loss of approximately 2.5 dB including switch loss, and it achieves amplitude and phase variations of up to approximately 0.5 dB without divided power or switch loss, and 3°, respectively. Using the proposed feeding network, a circular low-profile UAV RF sensing antenna with quadruple polarizations was designed. Its electrical size, 10-dB impedance bandwidths, and a peak gain are approximately $0.57\lambda _{0} \times 0.57\lambda _{0} \times 0.08\lambda _{0}$ at 915 MHz, 16%, and 6 dBi(c), respectively.