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Jonathan Harris

How Do You Analyze ADC Noise? Part 2

Jonathan Harris
jonharris0
jonharris0
2/3/2014 10:14:06 AM
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Re: frequency sweep
Again, very good point.  The discrepancies are small in this case compared with the magnitude of the measurement.  Thanks to you for the kind words.  I enjoy the questions and interactions.  Thanks!

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etnapowers
etnapowers
2/3/2014 10:05:52 AM
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Re: frequency sweep
@Jonathan: thank you for this post, the small discrepancies are for sure due to this cause, however if the discrepancies with the actual measured data are small compared to the expected order of magnitude of the measurement, the approximation is valid.

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jonharris0
jonharris0
1/13/2014 4:06:20 PM
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Re: frequency sweep
Indeed, good points.  The ideal nature of the calculations does lend itself to some small discrepancies with the actual measured data.  I am always happy when measured data lines up closely with my calculated values. :-)

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etnapowers
etnapowers
12/28/2013 3:33:22 AM
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frequency sweep
I wonder if the error between theoretical and measured ADC noise depends on the frequency, due to capacitive or inductive effects that may appear as the operating frequency varies.

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etnapowers
etnapowers
12/28/2013 3:27:21 AM
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relative error
I think that an engineer has to take care of the absolute and relative error when evaluating theoretically a ADC noise and then measuring it.

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More Blogs from Jonathan Harris
We will continue looking at the AD9680 as an example just as we did in part 1. Similar to the real mode operation of the DDC the normalized decimation filter responses are the same regardless of speed grade.
Letís now take a closer look at the decimation filtering and how ADC aliasing influences the effective response of the decimation filtering
Increase the decimation ratio in the DDC to see the effects of frequency folding and translating when a higher decimation rate is employed along with frequency tuning with the NCO.
Letís now take a look at a real example with the AD9680-500. Weíll see how this simple yet powerful tool can be used to aid in understanding the aliasing effects of an ADC as well as help with understanding effects of some digital processing blocks in the AD9680.
Back in my April blog post this year, we took some time to look at the Frequency Folding Tool that is available on the Analog Devices web site. I would like to revisit this tool as there have been a few handy improvements that have been made based on some great feedback.
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