Topic: Digital Communications
The bandwidth occupied by an 8 PSK modulated signal, where each of the I, Q and C data streams which form the n-tuple IQC toggle at a rate 200 Mbps, is:
- A. 600 MHz
- B. 200 MHz
- C. 400 MHz
- D. 133.33 MHz
Answer: B. 200 MHz
Explanation: In 8-PSK, each symbol consists of 3 bits (I, Q, C). If each data stream toggles at a bit rate of $R_b' = 200$ Mbps, they form symbols at a symbol rate $R_s = 200$ Msps (since they toggle in parallel to form the IQC tuple). The minimum Nyquist bandwidth for PSK is equal to the symbol rate, $BW = R_s = 200$ MHz.