Optical nulling of wideband microwave signals

Adaptive nulling is a technique to reduce the detection of unwanted interference by selecting specifically against some characteristic of the interference. In the case of an antenna with several subapertures or channels, spatial selection of the interference is implemented through appropriate complex weighting of the channels to make the net antenna sensitivity orders of magnitude smaller in the direction of the interference. This paper describes how optics has been used to achieve a wide-bandwidth (2 GHz) null centered at 6 GHz for the case of two channels. Such a 33% bandwidth null could not be achieved with microwave technology alone