# distortion

An undesired change in waveform, as opposed to desired changes in waveshape like those from modulation. **(a) Amplitude distortion** is caused by undesired amplitude-versus-frequency characteristics. **(b) Harmonic distortion** is a nonlinear distortion characterized by the generation of harmonics of an input frequency. The percent harmonic distortion is a measure of fidelity; if *E*_{f} is the rms voltage of the fundamental and *E*_{n} is the rms voltage of the *n*th harmonic, the **percent harmonic distortion** is

*E*

_{n}

^{2})

^{1/2}

*E*

_{f}.

**(c) Intermodular distortion** is a nonlinear distortion characterized by the appearance in the output of frequencies equal to the sum and difference of integral multiples of the component frequencies present in the input. **(d) Nonlinear distortion** is caused by a deviation from a linear relationship between input and output. **(e) Phase distortion** results when phase shift is not linear with frequency over the bandpass or where it is linear but where the zero frequency intercept is not a multiple of π. Where the intercept is a multiple of *n*π, the waveshape is not changed in *n* is even and is inverted if *n* is odd, although the entire waveform may be delayed. See *linear-phase filter*.