IIR Bessel filter coefficients

[Alain_S]

Can someone tell me why I get 20 "Reverse" coefficients and 25 "Forward" coeffcients for a band pass 10 pole Bessel filter?

I expected 20 for both forward & reverse

Thanks for any reaction.

[Ashwin_S]

Check this out,

 why the number of Feed Forward and Feed Back co-efficients are varied while designing an IIR filter.

AshwiN,