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Participant anton2
Participant
459 Views
Registered: ‎05-28-2019

Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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Hi,

I'm trying to transmit a complex-valued waveform (bandwidth of like 20MHz and up-converted to an IF=50MHz) on a DAC channel (8x interpolation, sampling rate 983.04MS/s) of zcu1275, and receive it by an ADC channel (8x decimation, sampling rate 983.04MS/s) with down-conversion.

But the waveform error, compared with transmitted one, seems very large (like SNR < 25dB).

Does anyone have experience on similar experiments?

I guess it may be related to DAC/ADC dynamic range, or some overflow within the digital data path.

Does RF data converter IP core have a range of "suitable" input amplitude? Current waveform has a max of about -5 dBFS (dB below full scale) and an average of about -15 dBFS.

And will the data amplitude be somewhat adjusted within the digital data path of RF-DAC/ADC (e.g., to prevent overflow)? Can I find relevant information somewhere?

Since I don't have much experience on this RF data converter IP core, or analog part, any suggestion is appreciated.

Thanks a lot.

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1 Solution

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

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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@anton2 wrote:

Hi @zhendon 

Thanks a lot.

I'm still working on this issue.

(1) In my setup, the received baseband waveform had a phase shift compared with transmitted baseband waveform. May I ask how to remove it (for example, by setting any parameters)?

(2) What kind of cable did you use for loop back? And, did you use DC Block? This information could be important for me. Thanks a lot.

(3) May I ask how to use "RF analyzer" together with ZCU1275? Could you please kindly provide any web links or user guide?

 


Hello @anton2 

Sorry for the delayed response. I was on vacation for a week.

1) You might can compenstate the phase shift by setting and updating the NCO phase. there are two ways to do that. One is to update the mixer setting by using API function XRFdc_SetMixerSettings . The other way is to manipulating the NCO frequncy hopping interface. The interface is used for frequency hopping application so you can certainly use it for setting the new phase shift value.

The detail information of both methods can be found in PG269 and feel free to let me know if you have further questions.

2) I used an external balun board and the balun is DC blocked.

3) It is very easy to use RF analyzer for ZCU1275. There is an prebuilt bit file in the folder ..\RF_analyzer_1_5\Protocol\RFAnalyzer\bitstreams. You can used the bit file with name "RF_Analyzer_29DR_20mA.bit".

This AR can help you have a quick look on how to startup the GUI.

https://www.xilinx.com/support/answers/72486.html

UG1309 is the official document

https://www.xilinx.com/support/documentation/user_guides/ug1309-rf-data-converter-interface.pdf

You can jump to Ch5 in this user guide for detail information of RF analyzer.

thanks.

 

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6 Replies
Community Manager
Community Manager
362 Views
Registered: ‎08-30-2011

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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Hello,

Is it possible for you to have a check on the DAC output by a spectrum analyzer before looping back to the ADC? I will check you case with my ZCU1275 and get back to you later.

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

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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You have two parts to the problem,
analog and digital,
you need to divide an conqueror

Digital , simulate the design, see if that saturates, wave forms get through un distorted.

Analog, do you have the correct filtering on the DAC output, are you saturating the amplifiers / drivers,

Out with the spec analyser scope , unless you have good simulation for this

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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Community Manager
Community Manager
342 Views
Registered: ‎08-30-2011

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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Hello,

I had a quick check on ZCU1275. DAC output loop back to ADC. It seems no problem with your setting for this board. I compared the ADC output in GUI with the DAC output directly to spectrum analyzer. ALmost the same.

image.pngimage.pngimage.pngimage.png

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Don’t forget to reply, kudo, and accept as solution.
-------------------------------------------------------------------------------------------------
如果提供的信息能解决您的问题,请标记为“接受为解决方案”。
如果您认为帖子有帮助,请点击“奖励”。谢谢!
-------------------------------------------------------------------------------------------------
Participant anton2
Participant
306 Views
Registered: ‎05-28-2019

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

Jump to solution

Hi @zhendon 

Thanks a lot.

I'm still working on this issue.

(1) In my setup, the received baseband waveform had a phase shift compared with transmitted baseband waveform. May I ask how to remove it (for example, by setting any parameters)?

(2) What kind of cable did you use for loop back? And, did you use DC Block? This information could be important for me. Thanks a lot.

(3) May I ask how to use "RF analyzer" together with ZCU1275? Could you please kindly provide any web links or user guide?

 

0 Kudos
Participant anton2
Participant
304 Views
Registered: ‎05-28-2019

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

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Hi @drjohnsmith 

Thanks a lot for the advice.

0 Kudos
Community Manager
Community Manager
202 Views
Registered: ‎08-30-2011

Re: Transmit an IF waveform using RF-DAC & RF-ADC loopback of RFSoC

Jump to solution

@anton2 wrote:

Hi @zhendon 

Thanks a lot.

I'm still working on this issue.

(1) In my setup, the received baseband waveform had a phase shift compared with transmitted baseband waveform. May I ask how to remove it (for example, by setting any parameters)?

(2) What kind of cable did you use for loop back? And, did you use DC Block? This information could be important for me. Thanks a lot.

(3) May I ask how to use "RF analyzer" together with ZCU1275? Could you please kindly provide any web links or user guide?

 


Hello @anton2 

Sorry for the delayed response. I was on vacation for a week.

1) You might can compenstate the phase shift by setting and updating the NCO phase. there are two ways to do that. One is to update the mixer setting by using API function XRFdc_SetMixerSettings . The other way is to manipulating the NCO frequncy hopping interface. The interface is used for frequency hopping application so you can certainly use it for setting the new phase shift value.

The detail information of both methods can be found in PG269 and feel free to let me know if you have further questions.

2) I used an external balun board and the balun is DC blocked.

3) It is very easy to use RF analyzer for ZCU1275. There is an prebuilt bit file in the folder ..\RF_analyzer_1_5\Protocol\RFAnalyzer\bitstreams. You can used the bit file with name "RF_Analyzer_29DR_20mA.bit".

This AR can help you have a quick look on how to startup the GUI.

https://www.xilinx.com/support/answers/72486.html

UG1309 is the official document

https://www.xilinx.com/support/documentation/user_guides/ug1309-rf-data-converter-interface.pdf

You can jump to Ch5 in this user guide for detail information of RF analyzer.

thanks.

 

-------------------------------------------------------------------------------------------------
Don’t forget to reply, kudo, and accept as solution.
-------------------------------------------------------------------------------------------------
如果提供的信息能解决您的问题,请标记为“接受为解决方案”。
如果您认为帖子有帮助,请点击“奖励”。谢谢!
-------------------------------------------------------------------------------------------------

View solution in original post