DM2_enonce

s(t)
s(t)
s(t)
Additionneur
s(t)
U0s’(t)=U0+s(t)
Multiplieur sm(t)=k s’(t) p(t)
p(t)
Alimentation
continue
GBF
(porteuse)
GBF (signal)
Antenne
émettrice
•s(t)
•p(t)
•U0
•sm(t)
•s(t)s(t) = S0cos(ωst)fs=ωs/2π < f <
•p(t)p(t) = Ecos(ωpt)fp=ωp/2π < fp<
•k k = 1/U0
sm(t)
sm(t) = (1 + m cos(ωst))Ecos(ωpt)m S0U0

sm(t)
Emax
Emin E m
E m fs
s(t)fp
0.00 0.05 0 .1 0 0.1 5 0.2 0
t em ps (m s)
2.0
1.5
1.0
0.5
0.0
0.5
1.0
1.5
2.0
signal (V)
signal m odul e en am p lit ude
E
E
max
min
sm(t)
sm(t)
sm(t)
s(t)sm(t)
Multiplieur
sm(t) s1(t)=k’ sm(t) p(t)
p(t)
Antenne
réceptrice
s
2
(t)
s
3
(t)
Filtre 1
GBF
(porteuse)
Filtre 2
s
2
(t)
s
3
(t)
p(t)
s1(t)k0
k0= 1/E
s1(t)
s1(t) =
5
P
n=1
s1ncos(2πf1nt)
s1nE m f1nfsfp
f11 f12 f15
E m f fp
f1n
s1n
s1(t)
s1(t)
x=ω/ω0=f/f0
(jx) = 2
1−x2+jx
Q

•Q Q = 1/√2
•ω0ω0= 2πf0f0= 50kHz
s2(t)
s2(t)
s2(t) =
5
P
n=1
s2ncos(2πf2nt+φ2n)n f2n=f1n
s2ns1nf1nf0Q
f2n
s2n
s2(t)
s2(t)s2(t)
s2(t)s(t)
s3(t)s(t)