Beam adaptive single arm rectangular spiral antenna with switches

A rectangular spiral antenna with switches is proposed for beam adaptive applications. The excitation of switches introduces variations in the current distribution on the antenna arm, thus causing the beam to steer. A switch is implemented as an element to short-circuit at a point on the spiral arm to the ground conductor (shorted spiral antenna). A shorted spiral configuration using four switches is analysed. For this configuration, both single- and multipoint switching are implemented. Sixteen possible switching cases are investigated. The radiation patterns are measured in the Satimo antenna test facility and numerically supported using the finite-difference time-domain (FDTD) method. Tilted (24°<θ_max<44°) and axial (5°<θ_max<12°) beams are obtained using various switching cases, thus realising an adaptive antenna. The gain, which is approximately 6.5 dBi, stays uniform within ±1 dB variation and the VSWR remains within an acceptable limit of 2 for the majority of the switching cases.