Dual-Band Antenna With Omni/Unidirectional Radiation Realized by Single Metal Plate

Abstract

This letter proposes a novel dual-band antenna realized by single metal plate. The basic antenna structure is a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> /2 dipole with omnidirectional radiation pattern, operating at 1.4 GHz. To obtain a second working band with directional radiation, this dipole is folded, therefore forming an open-end slot in-between its two arms, serving as a magnetic dipole. Then, by properly exciting these two dipoles with 90° phase difference in time domain, the inherent 90° phase difference formed between the slot and the electric dipole is cancelled. As a result, cardioid radiation pattern is obtained at 3.7 GHz. The measured results show that an impedance bandwidth of 10.3% and 18.1% is achieved at these two bands, respectively, with omnidirectional radiation pattern at 1.4 GHz band, and unidirectional radiation with at 3.7 GHz with wide beamwidth.