DocumentCode :
1191228
Title :
Detection of weak Doppler signal in a strong carrier: an equivalent high-Q band-elimination filter
Author :
He, J.
Author_Institution :
RIKEN, Inst. of Phys. & Chem. Res., Saitama, Japan
Volume :
141
Issue :
5
fYear :
1994
fDate :
10/1/1994 12:00:00 AM
Firstpage :
377
Lastpage :
381
Abstract :
In the paper, weak Doppler-shifted components of reflected ultrasonic signals were measured following the application of continuous-wave ultrasound for the measurement of blood flow velocity using the Doppler effect. The component of the emitted frequency was suppressed by subtracting an extracted signal from the reflected signal obtained by nonlinear closed loops. Phase information of the signal was obtained with a phase-locked loop, while the amplitude was controlled by an integrated loop to make the component of the emitting frequency minimum after subtracting. In principle, the circuit could be considered as a sufficient narrow band-elimination filter. The Q of the fitter was 104-105; its elimination depth was larger than 40 dB; its frequency stability was better than 10-5 because the phase-locked loop used a crystal oscillator as the voltage-controlled oscillator. Applying this circuit to a telemetry system, an example of measuring carotid blood velocity in an exercising man is given in the paper
Keywords :
Doppler effect; Q-factor; band-stop filters; biomedical electronics; biomedical measurement; biomedical ultrasonics; flow measurement; frequency stability; haemodynamics; interference suppression; medical signal processing; phase-locked loops; signal detection; Doppler effect; US signals; blood flow velocity measurement; continuous-wave ultrasound; crystal oscillator; equivalent high-Q band-elimination filter; frequency stability; integrated loop; narrow band-elimination filter; nonlinear closed loops; phase information; phase-locked loop; reflected ultrasonic signals; strong carrier; telemetry system; voltage-controlled oscillator; weak Doppler signal detection; weak Doppler-shifted components;
fLanguage :
English
Journal_Title :
Circuits, Devices and Systems, IEE Proceedings -
Publisher :
iet
ISSN :
1350-2409
Type :
jour
DOI :
10.1049/ip-cds:19941188
Filename :
329870
Link To Document :
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