Sampled signal processing device

A device for performing the discrete Fourier transform on a sequence of an arbitrary number, N, of equally spaced samples x(nT) of a signal x(t) to be processed, the device including a signal sample memory for the N samples x(nT), digital filter means having a transfer function H(z) with an input receiving samples from said memory to a pair of outputs, where:

• ##EQU19## and ##EQU20## and r is the order of the Fourier coefficient being calculated, the digital filter being such that application of the N samples in sequence at its input causes its outputs to produce respectively the real and imaginary components of the r-th Fourier coefficient, the device further comprising a respective sine/cosine memory for storing values of a.sub.r and b.sub.r for different r, and the filter including multiplier means connected to respective sine/cosine memory to introduce the appropriate values of a.sub.r and b.sub.r into the filter during calculation, and switch means, coupled to said filter for putting the the device into a configuration in which a respective sine/cosine memory is connected to store successive values at the filter outputs for future use as values of a.sub.r and b.sub.r for successive r, the multiplier means connected to an input for initial values ##EQU21## and the filter input connected to receive a unit impulse function u(rT) instead of the signal samples, where u(rT) = 1 for R = o and o for r .noteq. o.