Question

A normalized message signal has a bandwidth of W = 10 KHz and a power of
Pm= 0.75 . It is required to transmit this signal via a channel with an available bandwidth
of 80 KHz and attenuation of 50 dB. The channel noise is additive and white
with a power-spectral density of N0/2 = 10^(-10) watts/Hz. A frequency-modulation
scheme, with no pre-emphasis/de-emphasis filtering, has been proposed for this
purpose.
1. If it is desirable to have an SNR of at least 40 dB at the receiver output,
what is the minimum required transmitter power and the corresponding
modulation index?
2. If the minimum required SNR is increased to 60 dB, howwould your answer
change?
3. If in part 2, we are allowed to employ pre-emphasis/de-emphasis filters with
a time constant of τ = 75μsec, how would the answer to part 2 change?

Answer 1