Wideband Pattern-Reconfigurable Antenna Using Pair of Radial Radiators on Truncated Ground With Switchable Director and Reflector

A compact wideband pattern-reconfigurable antenna that is based on multiple radiators and switchable director/reflector is presented. The antenna consists of two quarter-wavelength radial radiators placed on two sides of a central feeder at the top layer. The bottom layer of the antenna includes a truncated quarter-wavelength ground plane and two quarter-wavelength parallel strips surrounding the radiators. Four p-i-n diodes, which are interlocked in pair, are used to control the radiation direction by selecting the radiator at the top layer and switching the strips at the bottom layer between being a director or reflector. Thus, the antenna achieves four-state pattern reconfigurability in the azimuthal plane. The antenna has a bandwidth of 1.88–2.64 GHz (34% fractional bandwidth) and is capable of steering the beam in the four directions 0°, 45°, 135°, and 180° in the azimuth plane. The antenna achieves a stable measured gain of more than 2.8 dBi across the band with a peak gain of 3.7 dBi. It has a low profile of 0.48λ<italic>e</italic> × 0.64λ<italic>e</italic> × 0.02λ<italic>e</italic> (λ<italic>e</italic> guided wavelength at 1.88 GHz) on a low-cost FR4 substrate. With the covered band, the antenna can be used in compact handheld and portable devices, indoor or short-range communications, WiMAX and WLAN.