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Observer
Observer
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Registered: ‎03-26-2020

RFSoC NCO Frequency Hopping with continuous phase

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Hi, 

I need to change the RFdc NCOs frequency using API on ZCU111 while the phase coherency is kept. 

I mean while the frequency of the sine wave is changing its phase changes without discontinuity. From this post here

https://forums.xilinx.com/t5/Versal-and-UltraScale/NCO-Frequency-Hopping-Has-Different-Initial-Phases/m-p/1064511 

it doesn't seem this is achievable by RFSoC! Am I missing something here?

 

Thanks, 

Tahereh 

 

 

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Observer
Observer
193 Views
Registered: ‎03-26-2020

To give an update here, I managed to use the RFdc GUI (to send single tone to DACs) and changed mixer frequency while capturing the waveform using Pico scope. 

the phase continuity was observed as shown in the picture below.

 

tghazaany_0-1606728461515.png

 

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Scholar
Scholar
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Registered: ‎05-21-2015

@tghazaany ,

An NCO is nothing more than a phase accumulator followed by a table lookup (or CORDIC) of some type.  To generate continuous phase frequency hopping, just adjust the phase increment.

Am I missing something?

Dan

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Observer
Observer
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Registered: ‎03-26-2020
@dgisselq
You are right about the way how NCO works in general. In RFdc IP core due to the procedure of updating the frequency of the NCO, the setting get sets to zero after the update happens. So the new phase value is irrelevant to its previous value.
That's my understanding and I'm not fully sure.
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Observer
Observer
194 Views
Registered: ‎03-26-2020

To give an update here, I managed to use the RFdc GUI (to send single tone to DACs) and changed mixer frequency while capturing the waveform using Pico scope. 

the phase continuity was observed as shown in the picture below.

 

tghazaany_0-1606728461515.png

 

View solution in original post

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