Analysis of the noise immunity of quadrature modulation method for turning signal constellations

Abstract

The paper considers the effect of the rotation of the signal constellation on the noise immunity of quadrature multi-point modulation methods. Based on the error vector in the Matlab + Simulink simulation environment, models of M - QAM modulators and demodulators with rotation of the signal constellations at an arbitrary angle are proposed. Considered the most commonly used in digital data transmission systems modulation: 4-QAM, 16-QAM, 64-QAM and 256-QAM. The simulation results of the proposed models confirmed the coincidence of the values of the rotation angles of the signal constellations recommended by the DVB-T2 standard, and also revealed the values of other angles that can be used to improve the noise immunity of multipositional quadrature modulation methods.