My professor mentioned that the order of a band-pass and a notch filter must always be even, when showing an example of designing a digital filter using the bilinear transformation.
Then he also mentions that the MATLAB code
ellipord returns half the actual order, so I figured the two statements must be connected somehow. I can't ask him since it's currently 3 AM and I couldn't find anything alone as to why these two statements are true.
Any thoughts? Thank you!