Interferometer Techniques Applied to Radar

A method is described for measuring the angular rate of a radar target by measuring the rate of change of the phase difference between radar echoes received at two widely separated antennas. It is shown that it is possible by the interferometer technique employed to obtain a direct measure of target angular velocity in much the same manner that Doppler measurements yield radial velocities. Three main questions existed concerning the basic feasibility of such an approach: 1) Will the effect of the fluctuations in time of arrival arising from inhomogeneities in the atmosphere render the data incapable of interpretation? 2) Is sufficient phase stability obtainable in the equipment and in the transmission paths between widely separated sites to permit phase measurements of the required accuracies? 3) Will serious degradations in the data occur as a result of shifts in the phase center of irregularly shaped tumbling objects?