Abstract: In this paper, a wideband ultra-high frequency (UHF) antenna which can be flush-mounted is designed. The antenna is composed of three parts: the cavity-backed discone antenna, the short-circuited structure between the top plate of the discone and ground, and the multi-plate antenna. These parts respectively generate medium, low and high resonance frequencies, thus widening the bandwidth of antenna efficiently. The influences of primary structural parameters on the resonance frequencies and impendence bandwidth are analyzed, then the optimal values are given, and the prototype with optimal parameters is fabricated. The measurement results show that the impedance bandwidth of VSWR≤2.5 achieves 65%, covering a frequency range from 430 MHz to 845 MHz, and the antenna has omni-directional patterns. Meanwhile, the antenna has very low profile; the overall height of it is less than one tenth of the largest operating wavelength of the antenna. This antenna has great potential in practical applications to aircrafts and vessels where flush-mounted antennas are required.

Key words: ultra-high frequency, wideband, antenna, low profile, omni-directional antenna