IIR filters can be designed using different methods ,one of the most commonly used is via the reference analog prototype filter,but there is other method is model order reduction .
I want more information about these two methods, when we can use the analog prototype filter for design iir filter ,and when we use the model order reduction techniques.
There is many techniques in model order reduction like balance truncation BT, impulse response graimian, Hankel approximation ..and for find a reduced system there need to have ''original system'', in generally , the original system must be transformed to state space representation, with use the controllability , observability in a closed form.
That is what i have a problem and i want to understand them,how can apply the state space ,how can i use the observability ,the controlability..?
Why do i think this is a IIR Filter Design method?
because these techniques is based on approximation of an original filter which satisfies the given frequency response specifications and subsequently obtaining a lower order IIR.