Understanding $\mathcal Z$-transforms and pole locations

1. How do you find the poles of Z-transform?
2. What does the Z-transform tell us?
3. How do you calculate Z-transform and ROC?

How do you find the poles of Z-transform?

The values of z for which H(z) = 0 are called the zeros of H(z), and the values of z for which H(z) is ¥ are referred to as the poles of H(z). In other words, the zeros are the roots of the numerator polynomial and the poles of H(z) for finite values of z are the roots of the denominator polynomial.

What does the Z-transform tell us?

In a like manner, the Z-Transform allows us to analyze the frequency and phase of sinusoidal components of a system to characterize a system's response. In short: If the Z-Transform of a system identifies exponentially increasing output values, then your system exhibits instability for that value of x[n] and z^-n.

How do you calculate Z-transform and ROC?

For x(n)=δ(n), i.e., impulse sequence is the only sequence whose ROC of Z-transform is the entire z-plane. If x(n) is an infinite duration causal sequence, then its ROC is |z|>a, i.e., it is the exterior of a circle of the radius equal to a.