Question

Q2.
(a)
With appropriate block diagram, describe two methods/principles of demodulating a Frequency Modulation (FM) signal.

(b)
Consider a frequency modulated signal FM )]sin(cos[)(tttsmcωβω+= where mω is the frequency of a sinusoidal message signal, cω is the carrier frequency and β is the modulation index.
i)
Using the above equation )(ts, explain the definition of Narrowband FM and wideband FM.

ii)
Prove that the narrowband FM signal is given by the equation )sin()sin()cos()(ttttsmccωωβω−=.

(c)
An angle modulated signal is given by the expression
??(??)=5??????[??????+40? ????500??? +20? ????1000??? +10? ????2000??? ]
i)
Calculate the bandwidth of the angle modulated signal by Carson’s rule, if the peak frequency deviation, fΔ= 30 Hz.

ii)
If the modulated signal is a phase modulated signal with phase deviation constant pk of 5 radians per volt, determine the message signal )(tm.

iii)
If the modulated signal is a frequency modulated signal with frequency deviation constant fkof π000,20radian/sec per volt, determine the message signal )(tm.

Answer 1