An Ultra-Wide Beam Circularly Polarized UHF Antenna for Search and Rescue Drones

An ultra-wide beam angle right-hand circularly polarized array antenna for UHF band is designed to improve the search and rescue coverage of emergency rescue UAVs effectively. The antenna is mainly composed of a radiating spiral arm board, a feed connection board and a power division phase-shifted feed network board, in which the radiating unit adopts a four-armed spiral antenna to reduce the size of the antenna array, achieving the right-hand circular polarization by controlling the phases and alignments of the excitation ports of the four spiral arms, adding an inverted F-branch between the radiating unit and the feed network to optimize the standing wave characteristics of the array, and implementing the feed network by a combination of multiple Wilkinson. The experimental results show that the array antenna has a voltage standing wave ratio <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{VSWR})&lt;2$</tex>, half-power beamwidth (HPBW)<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;120^{\circ}$</tex>, and gain<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;4\ \text{dB}$</tex> in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${4 0 6 - 4 2 5\ \text{MHz}}$</tex> band, where the above performances well satisfy the antenna requirements of the aviation emergency rescue system.