Question

In amplitude shift keying, transmission bandwidth is equal to
1. Base bandwidth
2. Twice base bandwidth
3. Half the base bandwidth
4. Four times base bandwidth

Answer 1

Correct Answer - Option 1 : Base bandwidth

In amplitude shift keying, transmission bandwidth is equal to Base bandwidth. 

The bandwith of differnet passband modulation scheme is as shown:

Modulation Scheme	Bandwidth
ASK and PSK	2Rb (Same as baseband BW)
FSK	fH - fL + 2Rb where fH is the higher cut-off frequency, fL is the lower cut-off frequency.
DSB-FC & DSB-SC	2fm Where fm is the frequency of the message signal.
SSB-SC	fm
VSB-SC	fm + fv where fv is the vestige frequency
NBFM (β < 1)	2fm
WBFM (β < 1)	2fm(1 + βf) Where βf is the modulation index of WBFM, given by βf = Δf/fm,  where Δf is the frequency deviation.
PM	2fm(1 + βp) Where βp is the modulation index of pm, given by βp = Kp × Am, where Kp is amplitude sensitivity of PM signal, Am is the amplitude of message signal.
M - array PSK	2Rb/n Where n is the number of bits.
M – array QAM	For rectangular pulse, 2Rb/n For raised cosine signal, Rb(1 + α)/n, where α is the roll-off.