Abstract: An MTI-filter included in the receiver part of a tracking radar for suppressing clutter when receiving echo pulses from a certain target. The transmitting pulses of the tracking radar are transmitted in series where the carrier frequency is varied from pulse to pulse and is repeated from series to series. The MTI-filter (F) contains a number of delay links (DL1-DLN), for example digital shift registers which are stepped forward timely with the radar PRF. The input of the filter and the output of the shift register M.ltoreq.N are connected to a differentiator (SK) where M=the number of carrier frequencies in a pulse series.

Abstract: The invention relates to a method for a tracking radar which transmits radar pulses towards a certain target whose target range from the beginning is known. The carrier frequency of the transmitted radar pulses are during the target tracking varied from one pulse to the next following, so that a pulse series including a certain number M of carrier frequencies is treated. The number M is chosen with reference to the continuously measured target range and as long as this range is less than a certain value. If the target range exceeds this value the number M of carrier frequencies is changed and a new pulse series including this new number is transmitted. The unambiguous range to the followed target becomes dependent on the frequency repetition frequency in the transmitted pulse series instead of the PRF of the radar.