Sensitivity of a Passive Correlation Interferometer to an Angularly Moving Source

A derivation of the sensitivity and signal-to-noise ratio of a passive correlation interferometer viewing a radiating point source moving angularly in the plane of the antennas is presented. A new method of measuring the angular velocity of moving objects using a correlation interferometer has recently been developed, and in order to evaluate the detection capabilities of such a sensor, the sensitivity to a fast angularly moving source must be known; such an analysis has not previously been published. It is shown that the spectral sensitivity of the interferometer is dependent on the angular velocity of the source: objects with faster angular velocities result in lower spectral sensitivities. Furthermore, the spectral response does not, in general, extend to dc. The total signal power is constant, however, and when integrated over the response bandwidth, the total sensitivity is independent of the angular velocity and reduces to the theoretical sensitivity of a correlation interferometer viewing a stationary source. The derivation thus proves that the interferometer sensitivity in angular velocity measurements can thus be calculated using the conventional definition of the sensitivity of a correlation interferometer.