A miniaturized ultra-wideband UHF antenna

Abstract

This paper presents a miniaturized ultra wideband UHF antenna. The antenna is loaded with magneto dielectric material. The antenna consists of a bent dipole backed by a magneto dielectric loaded reflector. The input impedance of the antenna is matched with 50 ohm cable by adopting a special technique that increases the cable impedance gradually to 73 ohm. The antenna is backed by a magneto dielectric loaded reflector so that the radiation becomes directive. The magneto dielectric loading on the reflector plate lags the phase of the generated waves from the antenna for a broad bandwidth thus reducing the height of the reflector plate achieving miniaturization in the Z direction. The dipole also has two bent arms that adds additional miniaturization factor. The overall dimension of the antenna is 250 mm × 250 mm. The reflector is bent at the diagonals to reduce the diagonal dimension to 280 mm. The miniaturization achieved is about 25% in the X and Y directions and about 70 % in the Z direction. The impedance bandwidth of the antenna is 115.7 % centered at 950 MHz. The antenna has positive gain for all frequencies over the impedance bandwidth and the front-to-back ratio is greater than 10 dB.