GATE 2014 EC (EC4) – Question 61
M-level PSK transmits independent binary digits through a 100 kHz bandpass channel at 200 kbps. The system has a raised-cosine spectrum with 100% excess bandwidth. Find minimum M.
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Correct answer: 15.9 to 16.1
Explanation
For raised-cosine shaping with100%excess bandwidth, α=1and RFbandwidth B=(1+α)Rs=2Rs. With B=100kHz, the symbol rate is at most50ksymbols/s. Carrying200kbps then needs at least4bits/symbol, so log2M≥4and **M=16**.