Notes on Digital Signal Processing: Practical Recipes for Design, Analysis and Implementation

Note 28. Exploring Periodogram Performance: Modulated Communications Signals

This note demonstrates the performance of the unmodified periodogram when it is used to estimate the spectrum of a continuous-phase frequency shift keyed (CPFSK) signal. This signal has nulls in its spectrum, but these nulls are not evident in the periodogram.

The utility of a spectrum estimation technique should not be judged solely on the technique’s ability to resolve closely spaced sinsoidal components. This note applies the unmodified periodogram technique to a binary CPFSK signal. The random nature of the data signal used to modulate the CPFSK signal helps to highlight how the unmodified periodogram’s high variance has a weakness in dealing with signals that are ...