PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

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( 50 t), 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)  c(t)] = 1/2π(ℑ[M(w) ⊗ C(w)])

v. AM_DSB_WC(w) = ℑ[{m(t) + 5}  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

i i. c(t) versus t ↔ C(w) versus w

iii. [m(t) + c(t)] versus t ↔ [M(w) + C(w)] versus w

iv. [m(t)  c(t)] versus t ↔ ℑ[m(t)  c(t)] versus w

v. [m(t) + (^5)  c(t)] versus t ↔ ℑ[(m(t) + 5)  c(t)] versus w
vi. cos[50t + m(t)] versus t ↔ ℑ{cos[(50t) + m(t)]} versus w
R = 1k Ω
v(t)
vs(t) i(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
  R1(s) = 3 Ω
  R2 = 7 Ω
  R3 = 5 Ω
  C 1 = 0.2 F
  C2 = 0.3 F
  L1 = 2 H
  I (^1) I
  2
  sw closes at t = 0


• 
  

  VC2(0) = 5 V
  
  
  VC1(0) = 3 V

  
  


• 
  

  IL1(0) = 1.3 A