Topic: Communication Systems
For an RF Circuit with RF = 2.5 GHz, LO = 2.64 GHz, and IF = 140 MHz, the correct statement is
- A. IF spectrum is inverted and image is at 2.780 GHz
- B. IF spectrum is not inverted and image is at 2.780 GHz
- C. IF spectrum is not inverted and image is at 2.360 GHz
- D. IF spectrum is not inverted and image is at 2.220 GHz
Answer: B. IF spectrum is not inverted and image is at 2.780 GHz
Explanation: $f_{si}$ (image frequency) $= f_{s}+2 I.F = 2.5~GHz+2\times140~MHz = 2.780~GHz$. $I.F. = f_{LO}-f_{s} = (2.64-2.5)GHz = 140~MHz$ and also $f_{LO}>f_{s}$ therefore I.F. spectrum is not inverted.