Automatic recognition of transmitted signal modulation type - uses vector type analysis and microprocessor for evaluation

摘要

Certain transmitted signal properties, in particular whether frequency or amplitude modulation is being used are automatically analysed by means of a vector representation constructed from samples of the incoming signals and a microprocessor to evaluate this vector. The method used is illustrated for the case when differentiation between frequency and amplitude modulation on a intermediate carrier signal (J) of around 30 KHz is provided. The signal is supplied to an amplitude demodulator and limiter to produce an amplitude demodulated output and to a frequency demodulator to give a frequency demodulated output. Three signals are fed to a coding circuit to give an effective vector representation - in this case two dimensional - of the incoming signal. Samples of this are stored in an intermediate store and processed by a microprocessor using a comparison technique and a pattern store to produce a codeword output representing the modulation type, or other property desired.