Abstract: A coherent radar receiver that has pulse-to-pulse coherence using an unlocked voltage controlled oscillator, such as a Gunn voltage controlled oscillator. The present invention is a W-band, for example, bistatic receiver that uses a scanning sum channel antenna to scan the target, a downconverter for downconverting received alternating sum and difference pulse echoes from the bistatic illuminator to provide video signals, and processing circuits for processing the downconverted the video signals to precisely locate the null position on the target. A Fourier transform circuit, magnitude detector and a peak detection and centroid circuit are used to generate a voltage frequency control output signal that is applied to the voltage controlled oscillator or local oscillator that controls its frequency. An angle estimation algorithm is used that processes the video signals to locate the null offset from the center of a scan pattern generated by the antenna.