A Miniaturized Pattern-reconfigurable Antenna for Broadband VHF and UHF Communications

In this paper, a miniaturized and broadband patter-reconfigurable antenna working at very high frequency (VHF) and ultra-high frequency (UHF) band is proposed. A dipole antenna element with a compact size, stable horizontal gain, a wide bandwidth, and an omnidirectional pattern is introduced firstly, which operates from 116 MHz to 505 MHz with a relative bandwidth of 108.55% and a size of 0.11λL× 0.33λL. An antenna array is constructed by combining four elements in a rotationally symmetrical manner. When one element is excited and other ports are terminated by matched loads, switchable directional beams are achieved. A 10:1 scaled model of the proposed antenna is fabricated and tested. Measured results show that the antenna element operates from 1.48 GHz to 4.86 GHz (a relative bandwidth of 106.62%) with a gain above -2 dBi. The proposed antenna array can achieve directional beams with a high front to back ratio (FBR) with gain value of 3-4 dBi within 2-4 GHz.