Applications for directional modulation on a digital phased array

Whereas traditional beamforming concepts for phased arrays transmit the same signal content in all directions, shaped in magnitude by the array factor and element patterns, a phased array system employing directional modulation presented here forms a signal in a desired direction through spatial combination using a solution of randomized phase weights applied across the array. In a radar system application, these randomized phased weights are applied over many time segments of a radar pulse compression waveform. Matched filters trained on the spatially varying signal projected in a particular direction respond preferentially to the signals in these directions, while partial orthogonality with respect to the signal in other directions allows for directionally dependent responses to reflected returns from a target. Effective transmit patterns for these matched filter banks are shown. Additionally, coupling on the array as a function of scan angle and the randomized phase weights is characterized.