# 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.

• 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.