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Contributor
Contributor
350 Views
Registered: ‎09-10-2019

ZCU111 Spurs Distortion

Hello,

We have the ZCU111. The RFDC IP is set up in the following way:

RFDAC_setup.PNG

We are trying to send an OFDM signal with stream clock 92.16MHz , 3686.4MSPS DAC sample rate and 2.4 carrier frequency. The main problem is that we see some spurs in the DAC output spectrum that are located in : Fcarrier and Fcarrier -+ stream clock. Is this logical? Are these spurs due to wrong setup? Maybe some hardware restrictions? Harmonics HD1,HD2 etc does not seem be in these frequencies.

IMG_7800.jpg

Best regards,

Theo

 

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Moderator
Moderator
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Registered: ‎04-18-2011

Re: ZCU111 Spurs Distortion

The signal and the spurs seem to be quite low power. 

I wonder can you share how you have the clocking on the ZCU111 set up?

Can you share what DAC and Channel you have here. Do you use one of the Baluns on the XM50), if so which one?

Keith 

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Contributor
Contributor
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Registered: ‎09-10-2019

Re: ZCU111 Spurs Distortion

Hello @klumsde ,

Thanks for responding.Yes the signal is quite low power and needs to be fixed. That was my main suspicion too. But after boosting the signal (+9dB i.e) and fixing the input values to the DAC also these spurs where boosted too and this is concerning me. About the clocking i programm the clocks with the Board UI .exe :

Clocking.PNG

Yes i am using on of the XM500 Baluns (the High frequency one). I am connecting my analyzer to the DAC229_T1_CH0 channel in XM500 corresponding to HF_TX_T1_CH0 HF balun as shown below:

IMG_7844.jpg

Thanks in advance,
Theo

 

 

 

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Moderator
Moderator
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Registered: ‎04-18-2011

Re: ZCU111 Spurs Distortion

Hi Theo, 

I gave this a try with the Evaluation set up. 

I don't have a scope but I look it back into the ADC high frequency Balun. 

I just use the coarse mixer to down shift it by FS/4 so we can decimate it a bit. zcu111_rx_spur_test.PNG

Can you take a look at it there. 

Keith 

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Contributor
Contributor
228 Views
Registered: ‎09-10-2019

Re: ZCU111 Spurs Distortion

Hello Keith,

Could you please explain me the configuration? What is the sampling frequency of the RFDAC - ADC? What is the streaming clock? Could you please give me some more details to understand?Also,is it the same (in terms of spurs and harmonics behaviour)  to use coarse mixer setup instead of fine mixer ?

One more question, about the configuration i uploaded. Should i change the decoder mode to linear or keep SNR as it is?

Thanks,
Theo

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Contributor
Contributor
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Registered: ‎09-10-2019

Re: ZCU111 Spurs Distortion

Hello,

Any progress?

Thanks

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Moderator
Moderator
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Registered: ‎04-18-2011

Re: ZCU111 Spurs Distortion

here is my set up. 

I use DAC tile 1 Channel 0. 

Same FS. Same Mixer setting. same interpolation. 

Only difference is the PL words. This is fixed and I can't change it. 

save it into the install of the Eval tool in the Config folder. 

change it from a .txt to a .cfg file and then load it in the GUI. 

 

Keith 

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