CIE A Level Physics (9702) 2019-2021

Revision Notes

20.2.4 Signal Attenuation

Signal Attenuation

  • Attenuation is a problem caused by the medium in which a signal is being transmitted
    • Over a longer distance, the power of the signal decreases
  • Signal attenuation is defined as:

The reduction in power and signal strength during transmission of a signal

  • This equates to a reduction in amplitude of the signal
  • It is represented in decibels (dB) or decibels per unit length
  • Attenuation is improved through the use of amplifiers
  • Gains in dB for series amplifiers are added, not multiplied, hence why this is a useful unit for attenuation
  • Digital signals are comparatively less prone to attenuation than analogue signals
    • This is because the information in analogue signals can be encoded in any state whilst digital signals can only be encoded in 2 states (1 or 0)

Calculating Signal Attenuation

  • The attenuation is defined by the ratio of the powers of the signal:

Calculating Signal Attenuation equation

  • Where:
    • P1 = input power of the signal (W)
    • P2 = output power of the signal (W)
  • Recall the attenuation is measured in decibels (dB)

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