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Explorer
Explorer
720 Views
Registered: ‎06-19-2014

RFSOC ADC high noise issue

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I am using ZCU111 with Vivado 2018.3 on windows 10.

I have initialized ADC and ADC is giving data on channels after m_axis_tvalid is high.

The problem is, when there is nothing connected to ADC input, the noise level is +-150 ADC counts which is pretty high. It should be around +-20. 

I am attaching how i connected signals with ADC and would like to know if there is anything wrong with clocking or resets or some other issue?

Details of circuit connection:

ADC clocks are coming from a source outside of ZCU111 board.

m_axis_aclk is coming from MMCM whose input clock is driven by clk_adc pins of ADC IP.

All resets are coming from onboard switch.

 

Capture.PNG
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1 Solution

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Explorer
Explorer
267 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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The issue was solved by porting big design to small one which had less noise. Strange but issue resolved.

View solution in original post

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14 Replies
700 Views
Registered: ‎09-17-2018

Re: RFSOC ADC high noise issue

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Have you terminated the ADC inputs in a quiet termination (2X - 50 ohm single ended, or 100 ohm differential)?

l.e.o.

Explorer
Explorer
606 Views
Registered: ‎06-19-2014

Re: RFSOC ADC high noise issue

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It is not related to hardware as there is no noise if a see ADC channels on Xilinx evaluation tool. This noise appears in my firmware.

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Highlighted
586 Views
Registered: ‎09-17-2018

Re: RFSOC ADC high noise issue

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OK,

If you think so, but it is most assuredly related to the hardware as far as I can tell.  So, good luck with your superior knowledge,

l.e.o.

 

Community Manager
Community Manager
558 Views
Registered: ‎08-30-2011

回复: RFSOC ADC high noise issue

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Your clock scheme and block diagram is very similar to the the example design generated with rfanaylzer enabled in IP wizard. Except the saxi-lite interface connection. So I assume it should perform good.

How about try the example design and insert system ILA then check the result if it is different with your project?

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Explorer
Explorer
486 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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It is fine in example design. I am wondering what can be wrong.

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Scholar drjohnsmith
Scholar
480 Views
Registered: ‎07-09-2009

回复: RFSOC ADC high noise issue

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Is this simulation or a real board ?

 

Assming a real board,

 

You need to do as others have said

Lets divided the problem first, ........

   

is it the ADC is the first question.

 

Put a ILA on the rad digital ADC output, 

     see if you have the noise there.

If so the next question is where from..

    its either comming in as analog signal, or on the power supplies.

        identify this by "shorting" the input to the adc directly, so you KNOW there is no signal in, 

           ( you might have to isolate the inputs on your board, to do this. Can you share your schematic of the inputs )

   Assuming you have not completely blown the input , If you still have noise, its most likely on the PSU into the RFsoc analog pins.

      If noise has gone , its comming in on the analog circuit you have, YOu know where to look.

 

At the ILA, if you do not see theis excessive noise, its not comming from the ADC, ..

     My guess then is the data has been shifted up, the digital equivilant of adding gain, you need to look at your code.

 

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
Explorer
Explorer
442 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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@drjohnsmith : Thanks for your detailed reply. 

This is not simulation.

As i mentioned earlier, this issue may not be related to hardware as I can not see this issue on xilinx evaluation tool. 

To debug, I disconnected everything from RFSOC IP outputs and checking with chipscope.

I was playing with resets and clocking scheme of different modules to see if it is rlated to clocks and reset issue but after many iterations, problem persists.

I posted here to know if someone can point looking at block diagram if something is wrong.

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Scholar drjohnsmith
Scholar
423 Views
Registered: ‎07-09-2009

回复: RFSOC ADC high noise issue

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My first guess would be a scalling issue in the chipscope capture,
try the ILA, and look at the bits, do you see what bits toggling ?
<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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Explorer
Explorer
402 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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This is ILA data which shows that without any signal at input, adc count is around +-150.

 

In another small firmware, in which no other logic is connected, ADc count goes to +-20.

In this firmware, I have removed all logic from ADC outputs but ADC count is too much.

Capture.PNG
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Scholar drjohnsmith
Scholar
382 Views
Registered: ‎07-09-2009

回复: RFSOC ADC high noise issue

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Ok, got that

 

Do both the designs have the same adc setup ? the same number of bits / interleaving  etc ?

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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Explorer
Explorer
378 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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Yes everything is same. 

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Scholar drjohnsmith
Scholar
376 Views
Registered: ‎07-09-2009

回复: RFSOC ADC high noise issue

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well im out of ideas,

Same input , same set up , then you should be getting same results.

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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Explorer
Explorer
360 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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@drjohnsmith thank you for follow up. I think I should take my rest of design to the correct working one. 

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Explorer
Explorer
268 Views
Registered: ‎06-19-2014

回复: RFSOC ADC high noise issue

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The issue was solved by porting big design to small one which had less noise. Strange but issue resolved.

View solution in original post

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