Linear Phase

A type of filter design where the phase response is a linear function of frequency. In other words, all frequencies are delayed in their passage through the filter by exactly the same amount. Extremely difficult to engineer in the analogue domain, but simple in the digital domain, and widely used in A-D and D-A converters for anti-alias and reconstruction filters. The impulse response of a linear phase filter is symmetrical, with pre- and post-ringing.