1. MEDICAL INSTRUMENTATION. Second Homework
동서의료공학과
정 진 웅

2. 1. Phase-sensitive Demodulation
Example1. e X

3. Matlab sourse of example1.
>> t1=0:0.001:0.1; >> x_0=2; >> y1=x_0*sin(2*pi*10*t1); >> y2=sin(2*pi*50*t1); >> y3=y1.*y2; >> plot(t1,y1); >> plot(t1,y2); >> plot(t1,y3);

4. Example2. X

5. Matlab sourse of example2.
>> t2=0:0.0001:0.1; >> y4=x_0*sin(2*pi*10*t2); >> y5=sin(2*pi*1000*t2); >> y6=y4.*y5; >> plot(t2,y4); >> plot(t2,y5); >> plot(t2,y6);

6. y ? If y(t) = x(t) * c2(t)= x(t) * sin2(2π*fct)
Diagram of demodulation y ?
If y(t) = x(t) * c2(t)= x(t) * sin2(2π*fct)
2sin2(2π*fct) = 1-cos(4π*fct)
So, sin2(2π*fct)=1/2(1-cos(4π*fct) )
y(t) = x(t) * c2(t)= x(t) * 1/2(1-cos(2π*fct) )
= 1/2x(t) - x*1/2*cos(2π*fct) = 0

7. 2. Capacitive Sensor
(a) step1
chest
Applied HR=60bpm → f=1Hz

8. On next slide, try sketch the Vo(t) using matlab
(b) step2
Analyzing this circuit,
On next slide, try sketch the Vo(t) using matlab

9. (c) step3

10. our goal is to measure ‘|P1 – P2|’
3. Problem 10
sol) P1 P2
rigid
rigid x1 x2
when P1=P2,, C1 = C2
diaphragm C A B C1 C2
our goal is to measure ‘|P1 – P2|’

11. sol)

12. constant
constant

13. LPF
10Hz