The maximum deviation allowed in a FM broadcast system is 75kHz. If the modulating signal is a single tone sinusoidal of frequency 15kHz, find the bandwidth of the FM signal. How does the bandwidth change if the modulating frequency is doubled? -

Mumbai University > Computer Engineering > Sem 3 > Electronic Circuits and Communication Fundamentals

Marks: 5 Marks

Year: May 2016

Given:

∆f =75 kHz, $ \ \ f_m=15 kHz$

We have $BW=2(∆f) + 2f_m=75 x 2 + 15 x 2=180 kHz$

When modulating frequency is doubled, the bandwidth changes slightly,

BW=75 x 2 + 15 x 20 = 450 kHz

When modulating signal amplitude is doubled, the frequency deviation becomes 2 x 75 = 150 kHz.

Now, the bandwidth becomes,

BW=2 x 150 + 2 x 20 = 340 kHz

Thus, the bandwidth is almost doubled.