456
Practical MATLAB
® Applications for Engineers
P.4.37 Let the modulating and carrier signals of a communication signal be given by
m(t) = pul(t/2) and c(t) = cos(50t), respectively.
Create the MATLAB script fi le telecom_analysis that returns
a. Expressions of
i. C(w) = ℑ[c(t)]
ii. M(w) = ℑ[m(t)]
iii. M(w) + C(w)= ℑ[m(t)] + ℑ[c(t)]
iv. AM_DSB_SC(w) = ℑ[m(t) ᠨ c(t)] = 1/2π(ℑ[M(w) ⊗ C(w)])
v. AM_DSB_WC(w) = ℑ[{m(t) + 5} ᠨ c(t)]
vi. FM(w) = ℑ[fm(t)] = ℑ[cos (50t + m(t))]
b. The following time–frequency plots:
i. m(t) versus t ↔ M(w) versus w
ii. c(t) versus t ↔ C(w) versus w
iii. [m(t) + c(t)] versus t ↔ [M(w) + C(w)] versus w
iv. [m(t) ᠨ c(t)] versus t ↔ ℑ[m(t) ᠨ c(t)] versus w
v. [m(t) + 5 ᠨ c(t)] versus t ↔ ℑ[(m(t) + 5) ᠨ c(t)] versus w
vi. cos[50t + m(t)] versus t ↔ ℑ{cos[(50t) + m(t)]} versus w
R = 1k Ω
v (t )
i (t )
v s (t)
+
−
C = 0.2 mF
−
FIGURE 4.99
Circuit diagram of P.4.34.
FIGURE 4.100
Circuit diagram of P.4.35.
V1 = 50 V
v 2 (t ) = 50 sin(5t )V
R 1(s) = 3 Ω
R 2 = 7 Ω
R 3 = 5 Ω
C 1 = 0.2 F
C 2 = 0.3 F
L1 = 2 H
I 1
I 2
sw closes at t = 0
+
VC 2(0) = 5 V
_
_
VC 1(0) = 3 V
+
IL1(0) = 1.3 A
CRC_47760_CH004.indd 456
CRC_47760_CH004.indd 456
7/28/2008 12:26:26 PM
7/28/2008 12:26:26 PM