is the order of IIR filter proportional to the group delay?

Thread Starter

TarikElec

Joined Oct 17, 2019
50
I know that the group delay of filter made in chain is proportionnal to the total group delay. I want to know the relationship between the group delay of fitler of order 2 and 3 ?
 

Papabravo

Joined Feb 24, 2006
16,936
When group delay is a concern, it is normally for it to be constant in the passband. The order of the filter does not have an appreciable affect on this property. Constant group delay in the passband is achieved by strategic placement of the poles of the transfer function for a filter of any order. I see no reason why the same principle should not apply to a digital filter as well.
 

Thread Starter

TarikElec

Joined Oct 17, 2019
50
''Constant group delay in the passband is achieved by strategic placement of the poles of the transfer function for a filter of any order'' I have for example to generate a coefficient of low pass filter by matlab dsp toolbox. how can I oknow where I place the poles so can I have a constant group delay?isn't the poles are placed according to the cutoff frequency and roll off order?
 

Papabravo

Joined Feb 24, 2006
16,936
''Constant group delay in the passband is achieved by strategic placement of the poles of the transfer function for a filter of any order'' I have for example to generate a coefficient of low pass filter by matlab dsp toolbox. how can I oknow where I place the poles so can I have a constant group delay?isn't the poles are placed according to the cutoff frequency and roll off order?
Constant group delay in the passband is achieved with a Bessel Filter. The key characteristic is that the poles lie outside the unit circle and the angles of the poles are equally spaced along the jω-axis. This leads to a transfer function with equal coefficients for the constant term and the linear term.
 

Attachments

Top