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Abstract

Method and apparatus for synthesizing a continuous estimate signal of a Gaussian signal resulting from ultrasonic Doppler measurement on a fluid flow, from existing segments of the Gaussian signal. The segment signals are first stored and there is at the same time calculated a characteristic frequency parameter for each segment. The frequency parameter is combined with the first stored segment signal for transposition thereof to a base-band at or about the zero frequency point, and this base-band signal is used to generate coefficients in a controlled filter device which on the basis of a broad-band input signal gives a synthesized filter output signal which is a substantially Gaussian signal. The filter output signal is multiplied by a weighting or window function for smoothing the transitions between successive segments. Parallel to the above signal processing there is for each segment of the initial Gaussian signal on the basis of said frequency parameter, formed a parameter at each instant which is an estimate of the frequency parameter of the initial signal between the segments, in order to thereby represent the comparatively quick variations in the location of the frequency spectrum of the initial signal. The latter estimated frequency parameter is combined with the smoothed filter output signal so that this is transposed back to the frequency range of the initial signal and thereby constitutes the synthesized continuous estimate signal. The invention primarily is intended for use with ultrasonic blood flow measurement in living biological structures. This method and apparatus may be incorporated into a complete system for investigating circulatory systems, particularly in hospitals.

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First Claim