Adaptive Antennas

As a follow-on programme to the radio propagation studies (see future radio systems ), adaptive antennas have been developed to help mitigate the effects of multi-path interference. The emphasis has been on low-cost antennas for wireless-LAN applications, particularly at 2.5 GHz, where a modest phased array architecture providing spatial selectivity may considerably enhance link performance compared with omni-directional or non-adaptive antennas.

The prototype 3-beam position 2.5 GHz phased array is shown, which offers 10 dBi of directive Gain.

(Aperture coupled antenna array feed lines and phase shifters)

In this prototype, amplifier stages were integrated into each feed line to counter the slight loss in the phase shifters. In this configuration the antenna operated in receive mode only. For combined transmit-receive operation the amplifiers would be omitted. The radiation patterns are shown below. (The steered-right condition is not included, being a mirror image of the steered-left case.) It can be seen that the antenna gives spatial coverage at +/- 3 dB over 90 degrees.