Frequency analyzer comprising a digital band-pass and a digital low-pass

Abstract

A frequency analyzer of a predetermined number of channels comprises a digital band-pass and a digital low-pass filter section. A preselected number of digital samples sampled with a sampling period are stored in a buffer memory to be read out in each sampling period. A band-pass parameter memory memorizes for the respective channels band-pass filter impulse responses, each having preselected values, equal in number to the preselected number. A band-pass filter calculator calculates a convolution of each read-out digital sample and the preselected values of each response. The low-pass filter section produces frequency analysis results for the respective channels in each analyzing frame period equal to a first prescribed number of the sampling periods. A low-pass filter impulse response having a duration equal to the frame period multiplied by a second prescribed number and prescribed values, the predetermined number in each sampling period, is memorized in a low-pass parameter memory with its phase or the duration successively shifted by the frame period. A multiplier calculates products of each convolution and the prescribed values of the respective memorized responses read out in an interval of production of that convolution. Absolute values of the products are accumulated in an accumulator register memory according to the respective channels and the respective phases and produced therefrom as the analysis results for the respective channels in those of the sampling periods which are spaced by the frame period and at which the respectively shifted durations have ends, respectively.