The Delay Filter simulates a transport delay frequency response. The frequency response magnitude of an ideal transport Delay Filter is unity for all frequencies. The frequency response group delay is equal to the duration of the transport delay for all frequencies. It is frequently necessary to account for transport delay in controls applications, and it is occasionally useful to delay a signal for timing purposes. FilterSolutions provides an approximation of an ideal transport delay frequency response consisting of a series of all-pass stages with a controlled group delay.

With an equiripple period of 2.0, the group delay is designed to be accurate for frequencies up to (N-1) /(T*PI) Hz, where N is the order of the filter, and T is the design transport delay. This value may be adjusted slightly by adjusting the equiripple period. The same equiripple group delay response is available for modified Bessel Filters. FilterSolutions allows definition of a Delay Filter by setting the delay time of the filter. The Delay Filter implemented by FilterSolutions optimizes the frequency response, as opposed to the time response, of the filter.

Shown below are examples of 8th order, 1 microsecond Delay Filters. Both frequency and step responses are shown.