# choosing an input signal for system identificaiton [closed]

I know we can use a

-step
-impulse
-sinus
-multisine
-random phase multisine


To identify a system.

## closed as too broad by Dilip Sarwate, lennon310, Paul R, penelope, Peter K.♦Jan 22 '14 at 19:35

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• This is too broad a question. Please edit it to specify what kind of system you are trying to identify (e.g. discrete-time or continuous-time), and any other information you have or assumptions that you can make, e.g. is the system just being modeled as a linear system for small-signal analysis purposes but is very definitely non-linear for large signals, for example, an audio amplifier. – Dilip Sarwate Jan 19 '14 at 14:59
• I'm not trying to identify a real system, just trying to gain a better understanding into the effect of using different kinds of input signals when doing system identification. I would however limit the discussion to continuous systems that are not necessarily linear because I know that some inputs will demonstrate the non-linear behavior better. I know this is a very broad question but I need something to get me started :) – Thomas Jan 19 '14 at 17:45

a swept-frequency sinusoid is a popular driving signal and there is some theory behind it, if the swept frequency varies linearly with time. if log-frequency is swept linearly with time, the preceding theory no longer applies. the crest factor is $\sqrt{2}$.
another possible driving signal is a bipolar maximum-length sequence, which is $(-1)^{a[n]}$ where $a[n]$ is a binary {0,1} maximum-length PN sequence. with that signal the crest factor is as low as it can get (which is 1), but there can be unpredictable behavior if there are sufficient non-linearity in the system being tested.