We know for AM signal,
Available bandwidth = 2*fm = (fc + fm) - (fc - fm)
where, fm = message signal or modulating signal
On the other hand, modulation index = Em / Ec
where, Em is equal to amplitude of modulating signal and Ec denotes amplitude of carrier signal.
Modulation index is calculated differently for frequency modulation (FM)
Where modulation index = (frequency deviation) / frequency of modulating signal
Bandwidth = 2*modulating signal (modulation index + 1)
and for phase modulation (PM), the maximum change in the phase of the carrier signal in accordance with the highest amplitude of the message signal is termed as modulation index.
Q. In AM modulation, if modulation index increases what happens to the bandwidth, transmission power, and noise
A. So, if modulation index increases then there is no change in Bandwidth while the frequencies of modulating signal and carrier signal remain same.
Now, we're coming to the transmission power part,
Pt = Pc (1 + (modulation index)^2)/2 )
where, Pt = transmitted signal power
Pc = power of the carrier signal
As a result, as the modulation index rises, so does the transmission power.
Bandwidth of ASK, FSK, and PSK
Bandwidth of ASK = 2*Rb
Bandwidth of FSK = 2*Rb + f1-f2
Bandwidth of FSK = 2*Rb
where, Rb = bit rate