Space/time/frequency methods in adaptive radar - New Jersey ...

16Figure 2.5 Magnitude of the Fourier transform of a sine wave with a frequency of20 HzA complex-valued frequency-shift-keyed signal, as in Figure 2.6, is an exampleof a signal which displays time localization of spectral components. This figure showsonly a single frequency is present at any instance of time. This frequency may beobtained as the derivative of the instantaneous phase, arg{s(t)}, which is defined asthe instantaneous frequency (IF) [29],The group delay (GD) is defined aswhere arg{S(ƒ)} is the phase spectrum.