# How to check if given samples represent an underdamped signal that converges?

1. ## How to check if given samples represent an underdamped signal that converges?

How to check if given samples represent an underdamped signal that converges to a final value?
You can use any programming language you want?
Samples are taken in a systematic and fixed periodical manner
A friend of mine was asked this question in an interview.. I'm trying to solve it? any idea?

What kind of question this is?

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2. ## Re: How to check if given samples represent an underdamped signal that converges?

It's one of those questions that are open-ended. It doesn't have only one correct answer. The interviewer can watch how the applicant approaches a challenge, how he focuses on the key issue, how much knowledge he brings to the table, how he considers possibilities, looks for pros & cons, etc.

I think the idea is to look for peaks in amplitude, while trying to locate peaks that occur at regular intervals, and then check whether each peak is less than the previous peak. If that is the case then it suggests the signal is converging.

Although the question does not ask the final value, however if it did then we might be able to calculate it by taking an average of the peak readings.

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3. ## Re: How to check if given samples represent an underdamped signal that converges?

Hi,

Yes, I agree with Brad's solution.

If you want a second (possible) solution - not sure if it's worth the effort in reality:
* Continously run an FFT on the sample data,
* Find the peak (besides DC)
* focus on ths frequency, it should continously decrease in amplitude

Klaus

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