November 23, 2007
Due: November 30, 2007 at 13:00 O’clock
ECE 311 ANALOG COMMUNICATION
HOMEWORK 4
1- An angle modulated signal has the form
s(t )  100 cos2f ct  4 sin 2000t 
where f c  10 MHz .
a) Determine the average transmitted power.
b) Determine the peak phase deviation
c) Determine the peak frequency deviation
d) Is this an FM or a PM signal? Explain.
2- The carrier c(t )  100 cos( 2f c t ) is phase modulated by the signal m(t )  5 cos( 2000t )
The PM signal has a peak phase deviation of  / 2 .The carrier frequency is 100 MHz.
a) Determine the magnitude spectrum of the sinusoidal components and sketch
the results.
b) Using Carson’s rule, determine the approximate bandwidth of the PM signal
and compare the results with the analytical result in part (a).
3- The message signal m(t) into an FM modulator with k f  25 Hz / V is shown in Fig.3.
Plot the frequency deviation in Hz and phase deviation in radians.
Fig.3
4- An angle modulated signal is given as
s (t )  100 cos( 2000t   (t ))
Where (a)  (t )  5 sin( 20t ) and (b)  (t )  5 cos( 20t ) . Determine and sketch the
amplitude and phase spectra for (a) and (b), and compare the results.