Communication Systems – Multiple Choice Questions (MCQs)

1. 1. Which of the following is an analog modulation technique?

   • A. PCM
   • B. QPSK
   • C. AM
   • D. FSK

2. 2. The modulation index for AM is defined as:

   • A. Ac/Am
   • B. Am/Ac
   • C. Af/Ac
   • D. Ac/Af

3. 3. What happens if the modulation index in AM exceeds 1?

   • A. Overmodulation
   • B. Undermodulation
   • C. Perfect modulation
   • D. No effect

4. 4. Which type of AM has the highest power efficiency?

   • A. DSB-SC
   • B. SSB-SC
   • C. AM (with carrier)
   • D. VSB

5. 5. The bandwidth of an FM signal is approximately given by Carson's rule as:

   • A. 2(Δf + fm)
   • B. 2fm
   • C. Δf + fm
   • D. Δf - fm

6. 6. Which modulation technique is more robust to noise?

   • A. AM
   • B. FM
   • C. PM
   • D. DSB-SC

7. 7. Pre-emphasis and de-emphasis circuits are used in FM to:

   • A. Increase bandwidth
   • B. Reduce noise
   • C. Increase power
   • D. Improve fidelity

8. 8. Phase Modulation (PM) is a form of ________ modulation.

   • A. Amplitude
   • B. Frequency
   • C. Angle
   • D. Pulse

9. 9. Noise in a communication system is undesirable because it:

   • A. Increases signal power
   • B. Decreases signal power
   • C. Corrupts the signal
   • D. Increases bandwidth

10. 10. Thermal noise is generated due to:

    • A. Random motion of electrons
    • B. Switching activity
    • C. Interference from other signals
    • D. Atmospheric conditions

11. 11. Shot noise is associated with:

    • A. Resistors
    • B. Diodes
    • C. Transistors
    • D. All of the above

12. 12. The signal-to-noise ratio (SNR) is a measure of:

    • A. Signal power to noise power ratio
    • B. Signal voltage to noise voltage ratio
    • C. Noise power to signal power ratio
    • D. Bandwidth to noise ratio