i) Frequency Modulation

  • Frequency Modulation where the modulating signal causes changes to the frequency of the carrier signal.

  • This gives a more complex spectrum than AM and as a result occupies more bandwidth.

ii) Amplitude Modulation

  • Amplitude Modulation where the modulator causes the envelope of the carrier frequency to follow the waveform of the modulating signal.

  • The demodulator recovers this modulating signal from the envelope.

iii) Pulse Amplitude Modulation

  • Carriers are modulated with a train of pulses where a train of direct current digital signals is converted into a train of carrier frequency samples.

  • These samples are applied to an Analogue-to-Digital Converter (ADC) resulting in a series of on-off pulses.