Linear Phase Filters

Filters that delay all frequencies by the same amount are called linear phase filters.

Linear phase filters have a symmetric impulse response;

the sample about which there is symmetry yields the delay (in samples) of the filter.

**Figure 5:** Filter impulse response.
$\scalebox{0.4}{\includegraphics{eps/lpir.eps}}$

For this filter, the impulse response is symmetric about sample 0.5, which corresponds to a waveform delay of one-half sample at all frequencies.

``Mus 270a: Introduction to Digital Filters'' by Tamara Smyth, Department of Music, University of California, San Diego.