1.   Inevitably, filtering action is accompanied by a frequency-dependent phase shift.

2.   Although all the filter networks treated so far in this chapter cause phase shift, in each case it is accompanied by attenuation.

3.   What is more, should a component be varied to alter the phase shift, the attenuation also changes.

4.   Many practical situations require the introduction of a variable phase shift, ideally with no attenuation but at least with fixed attenuation.

5.   The parameter beta represents the phase shift introduced by a section.

6.   For a filter having n sections the total phase shift is, of course, and the total attenuation.