The time-frequency representations of the signals are a powerful tool for the analysis of non-stationary signals such as the biological ultrasound Doppler pulsed type. The measure of their instantaneous frequencies and of the amplitude of their spectral components, which corresponds to the measure of moving tissue velocity, can be performed using specific type of time-frequency representation such as the pseudo Wigner distribution that exhibits good properties and has been implemented in MATLAB-SIMULINK with optimized algorithms listed in the Appendix.