Ultrasonic flow measurement system employing cross-correlation of

Abstract

An ultrasound flow measurement system converts each of plural groups of reflection sample values from scatterers, into baseband complex data values and enables a velocity determination from just two lag samples. A cross correlation function derives a first cross-correlation value between a first set of complex data values that are derived at a first common sample time, during succeeding transmit events, and a second set of complex data values that are derived at a second common sample time, during succeeding transmit events. A second cross-correlation function derives a second cross-correlation value between the first set of complex data values and a third set of complex data values that are derived at the common second sample time. A local oscillator synchronizes both the baseband conversion and cross-correlation operation, and exhibits a rate of change of phase per sample time. A processor relates the rate of change of phase of the local oscillation signal, the first cross-correlation value and the second cross-correlation value to derive the velocity of the ultrasound scatterers. In particular, the first and second cross-correlation values enable establishment of a linear function defining the phase of the cross-correlation function of the complex data values. The rate of change of phase of the local oscillation signal enables establishment of a further linear function. The intersection of the two linear functions identifies the time at which a maxima occurs of the cross-correlation function, thereby enabling derivation of the velocity of the scatterers.