Antenna spacing considerations in an interference canceller

It is possible to remove an interfering signal from a receiver by injecting a sample of the interference in equal amplitude but opposite phase into the receive line. In the case of a remotely located source of interference, an auxiliary antenna is used to obtain the interfering-signal sample. When the angle of arrival of an interfering signal relative to the desired signal is small, or when other system requirements dictate omnidirectional antennas, the desired signal can either be enhanced or reduced in amplitude depending upon the spacing between the auxiliary and receive antennas. The author discusses the effect of antenna spacing on the desired signal and provides quantitative guidelines for such spacing. Placement of antennas relative to the direction of the signal sources is also considered. Experimental data are presented to verify the calculated results