Title :
Coherent FM Doppler system [US blood flow measurement]
Author :
Wilhjelm, J.E. ; Pedersen, P.C.
Author_Institution :
Worcester Polytech. Inst., MA, USA
Abstract :
A new Doppler approach to measuring the velocity of moving scatterers is presented. The technique is based on repetitive phase-coherent linear sweep signals (chirps), and promises to combine the high signal-to-noise ratio of continuous-wave (CW) Doppler with the ability to provide range information of pulsed-wave (PW) Doppler. Separate transmitting and receiving transducers are used. The receiver signal is demodulated with a frequency or time-shifted version of the transmitted signal, followed by a stationary echo canceller for removal of echoes from stationary reflectors. By appropriate choice of frequency shift and bandwidth of the lowpass filter, information from a small measuring volume, at a given depth, can be extracted. The position and velocity of each scatterer is encoded into the received chirp; specifically, the velocity is uniquely related to the Doppler-shifted sweep rate of the output signal from the stationary echo canceller
Keywords :
Doppler effect; biomedical measurement; biomedical ultrasonics; flow measurement; haemodynamics; Doppler-shifted sweep rate; chirps; coherent FM Doppler system; frequency shift; lowpass filter; moving scatterers; receiving transducers; repetitive phase-coherent linear sweep signals; signal-to-noise ratio; stationary echo canceller; stationary reflectors; time-shifted version; transmitted signal; transmitting transducers; Bandwidth; Blood flow; Chirp; Echo cancellers; Fluid flow measurement; Frequency; Scattering; Signal to noise ratio; Transducers; Velocity measurement;
Conference_Titel :
Ultrasonics Symposium, 1989. Proceedings., IEEE 1989
Conference_Location :
Montreal, Que.
DOI :
10.1109/ULTSYM.1989.67119
