A Reconfigurable Pattern Loop Antenna for Wireless Applications

This letter presents a new low-profile, reconfigurable pattern antenna. The antenna features a printed circular segmented loop fed by two separate feed points coupled to a parasitic composite right/left-handed transmission line. The key innovation of this design lies in its ability to switch between the three modes, monopole-like, broadside, and directive, by electronically controlling the p-i-n diodes, allowing for dynamic adjustment of the radiation pattern. In directive mode, the antenna's beam can be steered electronically in the azimuth plane, while the monopole-like and broadside patterns are achieved through phase difference adjustments between the antenna ports. A prototype has been fabricated and tested, demonstrating a measured impedance bandwidth of 50 MHz ($|S_{11}|< -{\text{10}}$ dB) and a maximum radiation efficiency of 86%, yielding a realized gain of 4.2 dBi.