Apparatus for processing a signal

An apparatus for processing a signal for input to a neural network, the apparatus comprising:

• an input configured to receive a signal comprising a plurality of samples of an analog signal over time;
• and
• a processor coupled to the input and configured to:
• determine at least one frame comprising a group of consecutive samples of the signal, wherein the or each frame includes a first number of samples,
• for each frame, determine a set of correlation values comprising a second number of correlation values, the second number less than the first number, each correlation value of the set of correlation values based on an autocorrelation of the frame at a plurality of different time lags, and
• provide an output based on the set of correlation values corresponding to the or each of the frames for a neural network for one or more of classification of the analog signal by the neural network and training the neural network based on a predetermined classification.