6.9 REVISION QUESTIONS

Write an equation for an amplitude modulated (AM) wave.

Sketch the time-domain and frequency-domain diagrams for a 10-V, 10-kHz carrier that has been amplitude modulated by a 2-V, 2-kHz waveform.

Write the equation for an AM modulation factor.

Write the equation for DSB and sketch the time-domain and frequency-domain diagrams.

Draw the time and frequency domain diagram of the USB waveform resulting from a 10-V, 10-kHz carrier modulated by a 2-V, 2-kHz waveform. Draw the LSB waveform that would result from the same modulation.

List four advantages of SSB over AM and DSB.

List two disadvantages of SSB compared with DSB.

Briefly describe VSB and ISB.

Briefly describe how the amplitude, polarity and frequency of a modulating waveform affect the carrier in FM.

Write the equation for an FM waveform.

Write the equation for the FM frequency deviation, modulation index and deviation ratio.

Write the equation for Carson’s Law for FM bandwidth.

Briefly describe the FM capture effect.

List four advantages of FM over AM.

Name the most significant disadvantage of wideband FM.

Write the equation for PM.

With the aid of time-domain and frequency-domain diagrams, describe ASK, FSK, PSK, QPSK, APSK, and QAM.

Explain why ASK is rarely used in satellite communications and identify its main vulnerability.

Explain how QPSK achieves twice the bit rate of BPSK without increasing bandwidth.

Describe the difference between PSK and DPSK and why DPSK avoids absolute phase ambiguity.

Compare QPSK, 8PSK, and 16PSK in terms of spectral efficiency and noise tolerance.

Describe the main advantages of APSK relative to QAM for use in satellite systems employing TWTAs.

Compare the error performance of BPSK, QPSK, and higher-order MPSK in terms of required E_b/N₀ and susceptibility to noise.

Briefly explain how the measure E_b/N₀ relates to probability of error and why implementation margin is required in practical systems.

Define spectral efficiency.