Automatic equalizing system with dft and fft

Abstract

The equalizing arrangement in accordance with the invention comprises an equalizing unit (4) for correcting the frequency characteristic of an electric signal applied to its first input (7) under the influence of a control signal (10) applied to its second input (8) and for supplying a corrected electric signal to its output (9), and a frequency analyzing unit (16) having a first input (15) coupled to a point in the signal path between the input terminal (1) and the first input (7) of the equalizing unit (4), a second input (17) coupled to the pick-up means (14) and an output (19) for supplying the control signal (10). The analyzing unit (16) is constructed to apply a Fourier transform to the previously digitized input signals x(t) and y(t) applied to its first and its second input, to compute Fourier-transformed signals F.sub.x (f) and F.sub.y (f) of these two signals and to compute a transfer function between these two signals. Preferably the frequency analyzing unit is further constructed to compute a coherence function .gamma..sup.2.sub.xy (f) between the two signals and, in determining the control signal, to ignore the values of the transfer function for those frequencies f.sub.i for which .gamma..sup.2.sub.xy is smaller than a specific value, for example 0.8. By means of the arrangement in accordance with the invention a better equalization can be achived and the distortion of the output signal of the arrangement is low.