Damian Stewart wrote:
Charles Henry wrote:
There is no zero at z=0. I'm not sure about this one--but it seems as though it's impossible to have a zero at z=0?
a zero at z=0 is a delay of 1 sample, so in:
y = a x(0) + b x(-1) + c x(-2) + d y(-1) + e y(-2)
there is a zero at z=0 if a == 0, and two zeros at z=0 if a == 0 and b == 0
(iirc)
[shrug] i don't even know what a 'zero' is. and that's after reading several different webpages that attempted to explain biquad filtering to me. i just don't understand it.
if you have a transfer function like:
(z-a)(z-b)
H(z) = g ---------- (z-c)(z-d)
then 'a' and 'b' are zeros and 'c' and 'd' are poles.
The gain+phase response at a given frequency f is given by:
H( exp(i w) ) = H( cos(w) + i sin (w) )
where w = 2 * pi * f / SR
Intuitively the closer the point exp(iw) is to a zero, the less the gain (and if it's equal to a zero the gain is zero), and the closer the point is to a pole, the greater the gain (and if it's equal to a pole, the gain is infinite - so keep pole radius strictly less than 1 !).