Unstable Example

To form a linear phase TIIR filter based on the previous example, we need also the ``flipped'' impulse response generated by

$$\begin{eqnarray*} H^-_{\rm FIR}(z) &=& \frac{ -0.139770 z^2 +0.162126 z - z^{-300}} {0.98 z^2 -1.9z + 1} \\ &=& \frac{ -0.142622 z^2 +0.165435 z - 1.020408 z^{-300}} { z^2 -1.938776 z + 1.020408} \end{eqnarray*}$$

where the last equation is normalized by $0.98$ to make the denominator monic.

This system has two unstable hidden modes.