Automatic modulation classification using zero crossing

A modulation recogniser that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques. The zero-crossing sampler, as a signal conditioner, has the advantage of providing accurate phase transition information over a wide dynamic frequency range. Signal parameters such as zero-crossing variance, carrier-to-noise ratio (CNR) and carrier frequency are estimated. Phase difference and zero-crossing interval histograms play the role of features for modulation recognition. The classifier performance is given in the form of a confusion matrix. The simulation results obtained demonstrate that a reasonable average probability of correct classification is achievable for CNR ≥ 15 dB.