On the achievable DF accuracy of two kinds of active interferometers

We compare the performance of direction finding (DF) using two kinds of active interferometers in a minimal configuration: a conventional interferometer with one transmitter and two receivers, and an alternative interferometer of one receiver and two transmitters, each one of them radiates a different signal. By studying the Cramer-Rao bound (CRB) on the estimation error of the bearing of a silent, nonradiating target we find conditions under which the achievable DF performance of the two interferometers is equivalent. We show that under an ideal situation, a necessary and sufficient condition is that the two transmitted signals in the latter interferometer are perfectly uncorrelated. In more realistic scenarios the performance of the two interferometers is not the same unless more restrictive requirements are posed. The theoretical results are supported by simulation results.