Direction finding using a four-element time-switched array system

A four element time-switched array system is described. The received signal from each element of the array is time switched and combined to provide a phase modulated output signal. The form of the time modulation is related both to the switching waveform and the direction of arrival of the incident signal. The angular response at the first upper and lower harmonic frequencies exhibits a single deep null which can be scanned in angle over a full 360 range by controlling the element switching waveform. The time-switched array therefore achieves active electronic null steering without the need for phase shift, or time delay, networks.