TRemezType Type

Summary

Defines the type of the filter for Parks-McClellan algorithm.

Declaration

TRemezType = (rmtBandPass, rmtDifferentiator, rmtHilbert, rmtIntegrator, rmtDoubleDifferentiator, rmtDoubleIntegrator);

Value	Description
rmtBandpass	Supports all lowpass, highpass, bandpass, bandstop and multiband filters.
rmtDifferentiator	Designs a filter with a +20dB/decade slope and +90 degree phase shift.
rmtHilbert	Designs an allpass filter with a -90 degree phase shift.
rmtIntegrator	Designs a filter with a -20dB/decade slope and a -90 degree phase shift.
rmtDoubleDifferentiator.	Designs a filter with a +40dB/decade slope and a +90 degree phase shift.
rmtDoubleIntegrator.	Designs a filter with a -40dB/decade slope and a -90 degree phase shift.

Description

Defines the type of the filter the Parks-McClellan algorithm can create. Althought it is possible to design Double integrators and Double differentiators, these filter types do not have phase shifted as required (Double differentiator requires a 180 degree phase shift), but their amplitude response is correct. A -90 degree phase shift is a delay and a +90 degree shift is possible, because the total filter delay is (n-1)/2, where n is the length of the impulse response. The phase shift is evaluated relatively to the total filter delay. A filter with -90 degrees phase shift can be converted to a filter with a +90 degree phase shift, by scaling all the taps with -1. Inverse Hilbert transformer can be obtained by scaling the Hilbert transformer with -1.