Distortion is best defined as

Unwanted change in signal shape caused by the system's imperfect characteristics

Signals from other transmitters

Phase (delay) distortion occurs when

Phase is not linear in f, so frequencies are delayed differently

With two inputs f1 and f2, a non-linear system produces components at

f1 ± f2 and 2f1 - f2 (intermodulation)

2081 Baisakh (CS II) · 3 marks

Distortion and its types

Short answer

Distortion is the unwanted deterministic change in signal shape due to imperfect system characteristics. Linear distortion includes amplitude distortion (non-constant |H(f)|) and phase (delay) distortion (non-linear phase); nonlinear distortion produces harmonics and intermodulation products.

Define distortion and explain its types.

Distortion is the unwanted change in the shape of a signal caused by the imperfect characteristics of the system (channel, amplifier, filter) through which it passes. Unlike noise, it is deterministic and disappears when the signal is removed.

Types

Linear distortion – caused by a linear system that is not distortionless:
- Amplitude distortion: $\lvert H(f)\rvert$ is not constant over the signal band, so different frequencies are attenuated differently (e.g. a cable cutting high frequencies, making pulses rounded).
- Phase (delay) distortion: phase is not linear in $f$ , so different frequencies are delayed by different times; pulses spread and cause ISI in data links.
Non-linear distortion – caused when the output is a non-linear function of input, $y=a_1x+a_2x^2+a_3x^3+\dots$ $y = a_{1} x + a_{2} x^{2} + a_{3} x^{3} + \dots$ (e.g. an overdriven amplifier):
- Harmonic distortion: new components at $2f,3f,\dots$ .
- Intermodulation distortion: with two inputs $f_1,f_2$ , new components at $f_1\pm f_2$ , $2f_1-f_2$ , etc., causing crosstalk in multichannel systems.

Linear distortion is corrected by equalizers; non-linear distortion is reduced by operating devices in their linear region, pre-distortion or companding.

✓ Answer checked by Claude Opus 5.5 (high effort)

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