DYNAMIC NULL STEERING IN AN ULTRAWIDEBAND TIME-STEERED ARRAY ANTENNA

We develop a method for forming squint-free wideband nulls in the ante nna pattern of an ultrawideband array antenna. The technique uses an o ptical dispersive-prism beam former to provide time-delayed microwave signals to each antenna element for forming a squint-free main bean. T he amplitude-modulated optical carrier is propagated through a set of optical Links. Each link feeds an array element and includes an amount of dispersion proportional to element position. Tuning the wavelength of the optical carrier controls the microwave signal's arrival-time d elay gradient across the array. A dispersive-prism tapped delay-line m icrowave filter is used to frequency shape a nulling signal. The wideb and nulls do not significantly distort the main beam and are steered i ndependently of the main beam. The technique is applied to sidelobe nu lling for a transmitter and for jammer suppression for a receiver arra y. (C) 1998 Optical Society of America.