Comparing PSK and PAM Sensitivity to Phase Noise Through Signal Constellation Diagrams

This analysis compares the sensitivity of Phase Shift Keying (PSK) and Pulse Amplitude Modulation (PAM) to phase noise through signal constellation diagrams. By plotting constellation diagrams, we can visually evaluate the performance differences between these modulation schemes under phase distortion. The constellation diagram displays signal points representing various phase and amplitude combinations, where the distribution patterns reveal their tolerance to phase noise. Key implementation aspects include generating modulated signals using MATLAB's communication toolbox functions like pskmod() and pammod(), then applying phase noise models through complex exponential multiplication. The analysis examines constellation point clustering and dispersion - tighter clusters indicate better noise resilience. PSK maintains constant amplitude with phase variations, while PAM exhibits amplitude changes with phase sensitivity. Further evaluation involves calculating error vector magnitude (EVM) and symbol error rate (SER) metrics from the distorted constellations. Density analysis of signal point distributions helps quantify performance differences, where PSK typically shows superior phase noise tolerance due to its circular constellation structure compared to PAM's linear arrangement. This comparison provides practical guidance for selecting appropriate modulation schemes in phase-noise-affected communication systems.