Question

An M-level PSK modulation scheme is used to transmit independent binary digits over a band-pass channel with bandwidth 100 KHz. The bit rate is 200 kbps and the system characteristic is a raised-cosine spectrum with 100% excess bandwidth. The minimum value of M is

Answer 1

For M-Ary the bandwidth of the signal is given by B \( = \frac{{{R_b} \times \left( {1 + ∝ } \right)}}{{logM}}\) where ∝ is the Roll of Factor.

Application: For M-PSK bandwidth of signal given by B \( = \frac{{{R_b} \times \left( {1 + ∝ } \right)}}{{logM}}\)

Given bit rate  = 200kbps, excess bandwidth = 100

⇒ 100 KHz \( = \frac{{200\; \times \;{{10}^3} \times \;2}}{{logM}}\)

⇒ Log M = 4

M = 16