Communication Characteristics Of The Signal Analysis, Automatic Identification And Parameter Extraction

The automatic identification of the modulation types has been applied to many fields such as source identification, interference identification, radio interception, -electronic countermeasures, etc. The modulation recognizer based on the decision-theoretic approach and the constellation diagram is proposed and the signal's kurtosis is used as the indicator to differentiate the analogue modulation from the digital modulation. The analogue modulation recognizer utilized the decision-theoretic approach that a set of decision criteria for identifying different types of modulations is developed. The modulation types classified by this recognizer can be AM, DSB, SSB, VSB, FM. For the digital modulation recognizer, the blind identification and equalization algorithm based on Second-Order Statistics is applied to equalize the received signals firstly, and then the modulation type used can be figured out according to the shape of the rebuilt constellation. Some modulation parameters, such as the carrier frequency and the symbol rate, can be estimated prior to the recognition of modulation types. Such other parameters as the modulation index, the modulation frequency deviation, and the signal broadband can be further estimated after recognition. The recognition method for analogue modulations has less computational complexity, and the method for digital modulation has flexibility and can be easily extended to the coming modulation types.