Investigation on non‐linear aspects of pattern reconfigurable hexagon shaped planar loop antenna

Abstract

A planar electronically pattern-reconfigurable antenna based on Alford-loop-type hexagon shaped radiator is presented. The antenna consists of three half-wavelength dipole radiators arranged on both sides of an FR-4 substrate. It has an overall profile of 0.47λ 0 × 0.47λ 0 × 0.012λ 0 (λ 0 free space wavelength at 2.35 GHz). The bottom ground layer is tapered to allow impedance matching. Three PIN diodes are used to control the direction of radiation pattern by switching them in a controlled manner. Thus the antenna provides reconfigurable radiation patterns in six spatial directions with by switching three PIN diodes in ON and OFF states. The antenna has a measured impedance bandwidth of 2.35-to 2.45 GHz (4.16% fractional Bandwidth) and steers the beam in six directions 0°, 60°, 120°, 180°, 240°, and 300° covering the entire azimuthal plane. The antenna offers a maximum measured gain of 2.66 dB with simulated efficiency over 75%. Further, an investigation of non-linear effects due to PIN diodes shows that the antenna operates in the linear region up to an input power level of 27 dBm where the strength of received spurious harmonic and intermodulation signals is negligible. It makes the antenna suitable for indoor and short-range communication applications in the 2.4 GHz band.