In pulsed radar and sonar signal processing, an ambiguity function is a two-dimensional function of time delay and Doppler frequency showing the distortion of a returned pulse due to the receiver matched filter (commonly, but not exclusively, used in pulse compression radar) due to the Doppler shift of the return from a moving target. The ambiguity function is determined by the properties of the pulse and the matched filter, and not any particular target scenario. Many definitions of the ambiguity function exist; Some are restricted to narrowband signals and others are suitable to describe the propagation delay and Doppler relationship of wideband signals. Often the definition of the ambiguity function is given as the magnitude squared of other definitions (Weiss). For a given complex baseband pulse, the narrowband ambiguity function is given by
where denotes the complex conjugate and is the imaginary unit. Note that for zero Doppler shift this reduces to the autocorrelation of . A more concise way of representing the ambiguity function consists of examining the one-dimensional zero-delay and zero-Doppler "cuts"; that is, and, respectively. The matched filter output as a function of a time (the signal one would observe in a radar system) is a delay cut, with constant frequency given by the target's Doppler shift: .
Read more about Ambiguity Function: Relationship To Time–frequency Distributions, Wideband Ambiguity Function, Ideal Ambiguity Function, Properties of The Ambiguity Function, Square Pulse, LFM Pulse, Multistatic Ambiguity Functions
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