New signal processing methods of ultrasound phase reconstruction for measurement of disturbed flow

摘要

Natural turbulence occurring in streaming fluid modulates an ultrasound signal as well in phase as in amplitude. For further signal processing the ultrasound signals have to be demodu- lated. By undersampling the received signals at two points 90° shifted the phase and the amplitude modulation can be calculated. The modulation of the phase angle is calculated with the arctan function. The phase position of the receiving sensors is unknown and not connected with the sampling time. A new phase reconstruction algorithm by using the characteristics of the normal distributed phase is based on the analysis of the density distribution function of the phase angle. The position of the maximum of the distribution repre-sents the searched zero phase adjustment point of the receiv-ing sensor. By shifting the maximum back to zero the phase signal can be reconstructed. The modulation of the ultrasound signal is strongly influenced by disturbed profiles behind a single elbow or a double. Due to the new phase reconstruction method for the first time even disturbed profiles can be measured by calculating the transit time between two ultra-sonic barriers.