Basic Doubt about determining filter order..

[themaccabee]

Hi,

I was reading across some filter documents online here (**broken link removed**)

it was mentioning about an 8th order elliptical filter like shown below.. my basic question is how it said like the filter is 8th order..is it the number of reactive components? then shouldnt it be 11 ? ...Any explanation would be really helpful

Thanks
Regards

 

[barry]

the ORDER of a filter is the value of the highest exponent in the transfer function.

For an all-pole filter (e.g. Butterworth) the order is the number of poles in the transfer function. For digital filters, order is the number of delays in the filter.

 

[LvW]

my basic question is how it said like the filter is 8th order..is it the number of reactive components? then shouldnt it be 11 ? View attachment 92158 ...Any explanation would be really helpful
Thanks
Regards

Don`t forget that an elliptical filter has zeros.
In general - the order is determined by the number of poles (zeros of the denominator of the transfer function).

 

[themaccabee]

So i need to find out how many poles in the transfer function of the above said filter..Any method to derive the transfer function of such a long filter..

 

[LvW]

So i need to find out how many poles in the transfer function of the above said filter..Any method to derive the transfer function of such a long filter..

If this is a question you should spend some more time to ask for detailed information.

 

[ninju]

1. Either derive the entire thing.
2. Or put the whole circuit in a simulator and do a .AC and see the no of poles.
3. Or, understand the whole thing intuitively and figure out which components are likely to cause a pole and which cause a zero.