Ultrasound Doppler system with swept frequency excitation

A Doppler system based on frequency modulated excitation signals (FM Doppler) in the form of coherent linear sweeps is described. Both depth and velocity information can be extracted from the received signals by either of two processing schemes: phase shift measurement (PSM) and frequency (or spectral) shift measurement (FSM). The PSM is similar to the processing used in the conventional pulsed wave (PW) Doppler while the FSM is performed through cross-correlation of the magnitude frequency spectra of consecutive demodulated received signals. The FM Doppler system is characterized by low peak power, the possibility for spectral compensation of attenuation and transducer effects, and-for the FSM processing-no aliasing problems.<
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