Abstract: A signal processor eliminates sidelobe response from signals produced by a spaced antenna array that forms a single beam using spatial frequencies. The signal processor also produces error signals. The signal processor uses a phase coherent local oscillator to simultaneously convert the wavefront signal from each element of the antenna array to three different first intermediate frequency signals IF. The first IF signals of each element are cross-correlated with the first IF signals from each of the other array elements to form the signals containing sampled spatial frequency components IF.sub.2. Cross-correlating a second time using the sampled spatial frequencies as inputs produces signals containing derived spatial frequency components IF.sub.3. The signals containing derived spatial frequency components are synchronously detected (phase compared) and summed to provide a single beam output signal.