Center-Fed Unilateral and Pattern Reconfigurable Planar Antennas With Slotted Ground Plane

Abstract

A center-fed, single-layer, planar antenna with unilateral radiation patterns is investigated. The antenna consists of a turnstile-shaped patch and a slotted ground plane, which function as a vertical magnetic dipole and a horizontal electric dipole, respectively. By combining the two orthogonal dipoles with the same radiation intensities and antiphases, unilateral patterns with wide beamwidth and high front-to-back (F/B) ratio are achieved. As the unilateral radiation pattern can be easily steered in the horizontal plane by changing the slot location, a pattern reconfigurable antenna is further designed by using p-i-n diodes to control the connection states of the radial slots on the ground plane. Four steerable beams are obtained, capable of covering the entire azimuthal plane. For demonstration, both the unilateral and pattern reconfigurable antennas operating at 2.4 GHz WLAN band (2.40–2.48 GHz) were fabricated and measured. The measured overlapping bandwidths, with $\vert S_{11}\vert dB and F/B ratio >15 dB, are given by 7.0% (2.33–2.5 GHz) and 6.3% (2.32–2.47 GHz), respectively.