# Difference between repeated poles and distinct poles?

An important concept in dsp is marginal stability where we often see the term" repeated roots " or "repeated poles "? What are they?

Does the term repeated means that two or more poles occur at exactly same coordinates?

Please kindly give answer along with examples for both s domain and z domain?

• abjt, you completely shifted the focus of that question. Don't do that. A) it's not your question, B) even if it was, suddenly asking something different is frowned upon. Reverted your edit. – Marcus Müller Dec 3 '19 at 17:27
• Hey, @abjt, are you perhaps Man's second account and I was mistaken to revert your edit? – Marcus Müller Dec 3 '19 at 18:41

The Laplace transform of an integrator Is $$\frac{1}{s}$$, which is one pole at the origin. Two integrators in cascade would be $$\frac{1}{s^2}$$ so has repeated poles at the origin. The same with two accumulators in cascade would be $$\frac{1}{(1-z^{-1})^2}$$, which has repeated poles at z=1.