Real Time Spectrum Analyzer Including an Automatic Digital Modulation Classifier

In this paper, a new instrument for analyzing and characterizing an unknown signal without any a priori parameter knowledge is proposed. This new instrument joins the characteristics of a real time spectrum analyzer (RTSA) with those of an automatic modulation classifier. The modulation classifier is able to recognize classical single carrier modulations such as M-ary phase-shift keying (PSK), M-ary frequency shift keying (FSK), M-ary amplitude shift keying (ASK), and M-ary quadrature amplitude modulation (QAM), as well as orthogonal frequency division multiplexing modulations (OFDM) such as the discrete MultiTone (DMT). After the identification of the modulation type, the classifier automatically estimates some parameters characterizing the modulation. In order to evaluate the performance of the new instrument, several experimental tests, with actual signals, have been carried out in different operating conditions that are particularly critical by varying both the values of the signal to noise ratio and the main parameters of each identifiable modulation.