JAMES D. MEINDL 
1179 
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GAIN CELL 
DETECTOR 
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COMMAND RECEIVER SCHEMATIC DIAGRAM 
Figure 10. — Schematic diagram of command receiver. 
urement with the CW Doppler ultrasonic flowmeter. 
Proc. 24th ACEMB, Oct., 1971. 
16. Meindl, J. D., et aL An implantable ultrasonic 
blood flowmeter utilizing monolithic integrated cir- 
cuits. Proc. 8th ICMBE, July, 1969. 
17. DiPiETRO, D. M. and Meindl, J. D. An implantable 
ultrasonic flowmeter. Proc. 23rd ACEMB, Nov. 
1970. 
18. DiPiETRO, D. M., Meindl, J. D., et al. Chronic blood 
flow measurement in heart transplant dogs. Proc. 
24th ACEMB, Nov. 1971. 
19. Hudson, P. H. and Meindl, J. D. An implantable 
monolithic command receiver. Proc. 8th ICMBE, 
July, 1969. 
Meindl, J. D. et al. A monolithic command receiver 
for biomedical telemetry. Proc. 24th ACEMB, Oct., 
1971. 
Peronneau, p. A. and Leger, F. Doppler ultra- 
sonic pulsed blood flowmeter. Proc. 8th ICMBE, 
July, 1969. 
22. Baker, D. W. Pulsed ultrasonic Doppler blood 
flow sensing. IEEE Trans, on Sonics and Ultra- 
sonics SU-17:170-185, 1970. 
23. Gill, R. W., Meindl, J. D., and Haase, W. C. An 
implantable pulsed Doppler ultrasonic flowmeter. 
Proc. 24th ACEMB, Nov. 1971. 
20, 
21 
DISCUSSION 
CHAIRMAN Franklin: Are there questions? 
P. SOMANi, Abbott Laboratories, North Chi- 
cago : I'd like to ask you how you can work the 
velocity into actual flow. You have not ex- 
plained, and I am not very familiar with it. 
Dr. Meindl : Let's discuss the CW flowmeter 
first. We use a zero crossing detector to convert 
the frequency input to a voltage output, and 
the voltage output has a direct proportionality 
to the velocity at the position where the beam 
patterns intersect. It's important that the spec- 
trum be very narrow in order to use such a 
simple demodulation technique. In the past, very 
broad, or relatively broad, spectrums, have been 
used. This simple demodulation technique does 
not work with broad spectrums in the CW flow- 
meter. 
Now, in the pulse flowmeter, we essentially do 
the same thing. That is, we look at a very small 
volume, a volume whose diameter is small com- 
