Electronically steerable parasitic array radiator antenna for omni- and sector pattern forming applications to wireless ad hoc networks

An electronically steerable parasitic array radiator antenna is presented. The antenna has only a single element connected to a receiver or a transmitter. This active element is surrounded by parasitic elements loaded with variable reactors (varactors). The loaded reactance and the length of the parasitic radiators are designed so that each of the parasitic elements plays its role of director or reflector depending on its bias voltage on the loaded reactance. This design guarantees that the radiation pattern can be controlled by changing the bias voltages on the varactors. For omnipattern forming, a voltage vector is obtained such that the received power is maximised under the assumption that each component of the voltage vector is equal. An experiment yields an omnipattern with an average -0.83 dBi gain over the angles [0°, 360°]. For sector pattern forming, a single-source power maximisation technique is proposed to optimise the voltage vector such that the received signal power is as large as possible in the direction of the source. Experiments yield twelve sector patterns at every 30°. The average gain is 5.5 dBi in the patterns´ beam directions. The average 3 dB beamwidth is 72.4° for the sector patterns in the directions 0°, 60°, 120°, 180°, 240° and 300°, while the average value is 90.1° for the remaining patterns.