In radar, a two-dimensional function of radar range and Doppler frequency, determined by the transmitted waveform, that defines the effective filter response of the radar receiver. The ambiguity function is used to examine the suitability of different transmitted waveforms for achieving accuracy, resolution, freedom from ambiguities, and reduction of unwanted clutter. In particular, it defines 1) the sidelobe response to a complex radar waveform at different Doppler frequencies, and 2) the response of a receiver to targets at other ranges and Doppler frequencies from the desired target. The ambiguity function applies to both point targets and distributed targets.