Complex demodulation is used to generate a positive joint time-frequency distribution for broadband reflectometry signals, the so-called demodulogram, which is actually the dual of the well-known spectrogram and which, for a given signal, is obtained by squaring the modulus of the inverse Fourier transform of the signal frequency-windowed Fourier spectrum. The demodulogram and its properties are discussed, and the former is applied to the analysis of typical reflectometry data, being shown, in particular, that it can indeed yield what is strictly defined as the instantaneous frequency of discrete-time reflectometry signals.