Terminology

carrier signal/wave

  • a periodic waveform
  • is used to transmit information through space
  • a communication medium
  • the carrier signal is higher in frequency than the modulation signal

modulation signal/wave

  • contains information to be transmitted
  • types of modulation signals: audio signal, video signal, or a digital signal
  • a modulation signal of any type is transmitted via a carrier signal
  • the modulation signal is lower in frequency than the carrier signal

modulate

  • the impressing of the information-bearing modulation signal onto a carrier wave

demodulation/demodulate

  • the extraction of the information-bearing modulation signal from a carrier signal

modulator

  • is a device that performs modulation

demodulator

  • is a device that performs demodulation

modem (modulator-demodulator)

  • is a device that performs modulation and demodulation

baseband

  • the frequency band occupied by the modulation signal

passband

  • the higher frequency band occupied by the modulated carrier