Topic: Digital Communication
For a signal with $F_c$ (Centre Frequency) = 1200 MHz and BW = 100 MHz which of the following Sampling frequency ($F_s$) will cause spectrum inversion:
- A. 287.5 MHz
- B. 575 MHz
- C. 1150 MHz
- D. 1600 MHz
Answer: D. 1600 MHz
Explanation: The signal band is from $F_L = 1150$ MHz to $F_H = 1250$ MHz. Spectral inversion occurs when the bandpass signal falls into an even Nyquist zone (where the zone index is $m = \lceil F_H / (F_s/2) \rceil$). For $F_s = 1600$ MHz, the Nyquist frequency is $800$ MHz. The signal band $1150-1250$ MHz lies between $F_s/2$ (800 MHz) and $F_s$ (1600 MHz), which is the second Nyquist zone. Since 2 is even, spectral inversion occurs.