Null-steering antenna for mobile communication

The letter describes an antenna system for communication with mobiles. It provides omnidirectional coverage in the horizontal plane, plus a directional null which may be electronically steered in azimuth to minimise unwanted interference. The system uses a 5-element circular array with a simple feed network and a single phase shifter to control the null direction. Experimental results are quoted for a system capable of operating over a band of 120 to 190 MHz.