Abstract: The invention relates to a system for identifying targets as a friend or foe, which is operated in the millimeter-wavelength range by means of an interrogator and a transponder, with the interrogator and the transponder having essentially the same electronic assemblies and operating in essentially the same middle transmitting and receiving frequency, and with a large frequency difference between the two being tolerable. The interrogator operates with a directional transmitting/receiving antenna, whereas the transponder possesses an omnidirectional transmitting/receiving antenna.

Abstract: A method of determining the velocity of a radar target wherein at least two different pulse repetition frequencies are used. Each pulse repetition frequency comprises a predetermined division into equidistant Doppler numbers. For an echo signal, a Doppler number associated with the echo signal is determined for each pulse repetition frequency. Out of two Doppler numbers associated with different pulse repetition frequencies, a nonambiguous Doppler number is subsequently determined which lies within a predetermined velocity nonambiguity range, and the velocity of the radar target is determined from this Doppler number.