Process of sub-sampling in RF systems

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siyom

Member

• Nov 8, 2014

• #1

I know that this process basically involves sampling the incoming signal at lower frequencies to avoid having to process a larger signal,just don't quite get the gist of how this is done.for example I have a signal of 500kHz I want to make it low enough that it can be fed into an A/DC with a sample rate of 96kHz,how do I use sub-sampling?
Can I be referred to a more thorough explanation?

 

crutschow

Well-Known Member

Most Helpful Member

• Nov 9, 2014

• #2

You use sub-sampling to sample at a lower frequency. It's unrelated to how "large" the signal is.
The sub-sample frequency is related to the modulation frequency since all you need to do is sample fast enough to detect the modulation. So what is the modulation of the 500kHz signal?

 

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siyom

Member

• Nov 9, 2014

• #3

I am using frequency modulation.

 

crutschow

Well-Known Member

Most Helpful Member

• Nov 9, 2014

• #4

siyom said:

I am using frequency modulation.

Click to expand...

Then I'm not sure that sub-sampling will work for FM.

 

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siyom

Member

• Nov 11, 2014

• #5

I'm not dealing with high frequencies,just wanna use something like 100-500kHz...will that work?

 

crutschow

Well-Known Member

Most Helpful Member

• Nov 11, 2014

• #6

siyom said:

I'm not dealing with high frequencies,just wanna use something like 100-500kHz...will that work?

Click to expand...

The frequency is not the issue, its that it's FM. Just don't know that sub-sampling will work to detect an FM signal. Normally it's used to detect AM modulation.

 

languer

Active Member

• Nov 13, 2014

• #7

One of the keys of sub-sampling is that the ADC (I assume that is what you are using) bandwidth must be wide enough to capture your carrier signal. If it is, then the ADC will see everything and you can use the sub-sampling techniques. Modulation should not be an issue as long as your modulation bandwidth meets the Shannon's criteria.

ADI has very good references on this topic:
https://www.analog.com/static/imported-files/seminars_webcasts/3689418379346Section5.pdf

 

crutschow

Well-Known Member

Most Helpful Member

• Nov 14, 2014

• #8

An ADC measures amplitude changes. FM has no amplitude change. Thus I don't see how sub-sampling with an ADC can be used to detect an FM signal.