Abstract: The invention relates to arrangement for detecting the presence of echos for a multi-range-gate radar system.The signal A from a gate is combined with a signal B from one or more neighboring gate. This combination is performed by means of an operator which supplies signals S.sub.1 = A + k.sub.1 B and S.sub.2 = k.sub.2 (A - k.sub.1 B), where k.sub.1 and k.sub.2 are complex coefficients. A demodulator receiving S.sub.1 and S.sub.2 supplies a signal proportional to the cosine of the phase between S.sub.1 and S.sub.2. Said cosine signal is sampled, filtered and compared to a threshold. When exceeding said threshold the output signal indicates that an echo signal is received.