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Technion: Compressed sensing ups data acquisition resolution, cuts cost

8/18/2010 01:44 PM EDT
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kendallcp
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re: Technion: Compressed sensing ups data acquisition resolution, cuts cost
kendallcp   8/22/2010 4:24:04 PM
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An earlier paper on the process can be found at http://arxiv.org/PS_cache/arxiv/pdf/0902/0902.4291v3.pdf, a colleague pointed it out to me last year It's interesting, but there's no "free lunch" in there. The signal path still needs to deliver the required performance at the required bandwidth. It's a little different from the commonplace (in radio) application of undersampling, where the sampling process targets a higher order band of alias frequencies. Here, sparseness in the spectrum is exploited to allow the wanted aliases to be watermarked as belonging to a particular alias zone. But it's a bit disingenuous of one of the originators to say that they are doing something that EE's are normally taught not to do.

eryksun
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re: Technion: Compressed sensing ups data acquisition resolution, cuts cost
eryksun   8/22/2010 11:05:29 AM
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Each channel gets modulated separately by a PWM signal that has a spectral density specific to that channel. The modulated spectrum for each channel thus consists of scaled and shifted copies of the input signal's spectrum at the harmonics of the PWM signal. The important part here is that the resulting spectra of the 4 channels are all unique in a mathematically precise way. Thus the aliased output of undersampling is unique for each channel and mathematically related in such a way that it's possible to compute the original signal from the combined information. Also, since they claim compression, I assume each of the 4 ADCs is running at less than 1/4 the nyquist rate. If you record to an intermediate media, you could use this technique to sample at the bandwidth of the analog media using a much lower bandwidth ADC (but precise and accurate) -- trading off speed and real-time processing vs. the cost of having a separate ADC/PWM for each channel.

yosko
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re: Technion: Compressed sensing ups data acquisition resolution, cuts cost
yosko   8/19/2010 12:07:35 PM
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They suggest swapping one high-frequency sampler, with 4 lower-frequency samplers, each working on a different (ie. shifted) 'clock' (PWM signal). By modulating the high-frequency input signal, you "copy" it's frequency content to the lower frequencies (ie aliasing), which usually "harms" the input signal and causes data-loss. I'm assuming the input signal has a very narrow band frequency content, so the aliasing to lower frequencies doesn't harm it.

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