Reconstruct a sampled signal with ZOH
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Alessandro Russo
on 23 May 2016
Commented: Star Strider
on 23 May 2016
Hi all!
I have a simple question; i am sampling a signal and then storing the samples in Matlab. Now i want to correctly reconstruct the original signal for example with the Zero order hold, how can i do this? Is there an appropriate function? I found only d2c, but it doesn't seems that it takes directly the samples, but a model in z transform of the system! Thanks in advance.
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Star Strider
on 23 May 2016
Systems can be interconverted between discrete-time and continuous-time representations (what the d2c function does), but not signals, at least not in computers.
The signal will remain a sampled signal in your computer because that is the only way signals can be represented in computers. (It will never be a continuous-time signal.) Your signal was likely sampled using a zero-order-hold. Converting it to a continuous-time signal would require that you pass it through an appropriately-designed digital-to-analog converter (DAC). Sound cards do this all the time.
There are practical limits to signal reconstruction. The original analog-to-digital conversion characteristically uses a hardware anti-aliasing filter designed to remove all frequencies above the Nyquist frequency (one-half the sampling frequency), so all frequencies above the Nyquist frequency will be lost.
Even if the highest frequency in your signal is well below the Nyquist frequency, exactly reconstructing your signal would likely not be possible due to the inherent inaccuracies involved in sampling and reconstructing it.
There is a substantial literature on digital-to-analog conversion, so I will not even attempt to discuss the details here.
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Star Strider
on 23 May 2016
My pleasure!
I’ve done a lot of biomedical signal processing, so your question is in an area of my particular interest.
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