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Transfer function has 5th order denominator, how to factor the denominator such as D(s) = (1+s/wp) (1+s/wo1Q1 + (s/wo1)²) (1+s/wo2Q2 + (s/wo2)²)

Ali on 3 Aug 2023
Latest activity Reply by Carlos M. Velez S. on 12 Feb 2025

Hi Everyone,
I have a high-order filter and I need to determinate its R,L,C values. In the simulation, the filter is unstable for some values. But I want to find values for stability of the filter. For second order system has some formulation between Q and phase margin so that it can be obtain the stability ciriteria to choose components.
My transfer function denominator is 5th order polynomial, and it is not possible to find roots in terms of R,L,C, Lm. I need to factor it like one 1th and two second order as shown in below.
D(s) = (1+s/wp) (1+s/wo1Q1 + (s/wo1)²) (1+s/wo2Q2 + (s/wo2)²)
Is there any methods to reduce order of transfer function?(Maybe, it can be possible for only in certain frequency range, can be renounced high-frequency )

1 Comment

Carlos M. Velez S.
Carlos M. Velez S. on 12 Feb 2025
I recommend you to use a parameter estimation method directly. You can use the System Identification Toolbox or the Simulink Design Optimization Toolbox.

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