Linear phase

Linear phase is a property of a filter, where the phase response of the filter is a linear function of frequency. The result is that all frequency components of the input signal are shifted in time (usually delayed) by the same constant amount, which is referred to as the phase delay. And consequently, there is no phase distortion due to the time delay of frequencies relative to one another.

For discrete-time signals, perfect linear phase is easily achieved with a finite impulse response (FIR) filter.  Approximations can be achieved with infinite impulse response (IIR) designs, which are more computationally efficient.  Several techniques are:

When a sinusoid${\displaystyle ,\ \sin(\omega t+\theta ),}$  passes through a filter with group delay ${\displaystyle \tau ,}$  the result is:

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