Page 177 - Fundamentals of Communications Systems

Analog Communications Basics 5.17

(e) Parsevals theorem allows the power to be computed in the frequency domain
as
2
∞ 2
2 4 4
P m = |m n | = 2 + = 0.3325 (5.30)
π 2 9π 2
n=−∞
(f) The Matlab code
%
% M-file for EE501
% Problem 5.2
% Author: M. Fitz
% Last Revision: 01/29/01
%
time=linspace(-0.5,0.5,1000);
%
% e) Computing the power after filtering
%
m_1=4/pi^2;
m_3=4/9/pi^2;
p_m=2*(m_1^2+m_3^2)
%
% f) plotting the output message waveform
%
mess=2*m_1*cos(2*pi*2*time)+2*m_3*cos(2*pi*6*time);
% plotting
figure(1)
plot(time,mess)
xlabel('Time, t, seconds')
ylabel('m(t)')
produces the plot shown in Figure 5.14.