Maitry07
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keep your test simple with minimum variables. Just connect same signal to two ADCs. This should give zero phase.
Target dc by setting NCO to -RF then if you don't get zero phase either the NCO phase is playing or your logic needs check.
You can directly check the final I/Q dc levels and tell us what are they.
We have recommended this several times now. But OP refuses to cooperate.
Thus I'll leave this thread.
I have connected the same signal to 2 ADCs via BNC TEE.We have recommended this several times now. But OP refuses to cooperate.
Thus I'll leave this thread.
My last post was the feedback of your excel fileHello,
Is there any feedback on the above attached zip analysis?
Please check in excel. My amplitude is same only for both DDC = 0 Hz and DDC = 3 MHz and for both channel 1 and channel 2For DC and 3MHz, the phase and amplitude are different. You should get at least amplitude to be close enough.
So your test is not valid for its purpose.
For now, test 3MHz only and also ignore your other scaling calculations, you don't need them. Just look at I,Q as they are.
Avoid initial sections as tone goes through DDC filters (just delete them from vector).
Still you need to capture both channels at same time as the 3MHz cycles around?
channel A _ I data | channel A _ Q data | channel B _ I data | channel B _ Q data |
21563 | -19040 | -20188 | 20775 |
21574 | -19013 | -20226 | 20743 |
21607 | -18998 | -20256 | 20718 |
21584 | -18966 | -20277 | 20729 |
21640 | -18936 | -20300 | 20665 |
21655 | -18916 | -20307 | 20643 |
| | | |
OK you checked that and it looks close enough, just ADC noise variation expected. Now the phase is different, sort it out.Please check in excel. My amplitude is same only for both DDC = 0 Hz and DDC = 3 MHz and for both channel 1 and channel 2
For amplitude , sqrt (I^2+Q^2) need to be done and after doing that , both channels amplitude are same at DDC=0 and DDC =3 MHz
--- Updated ---
Please check below I,Q data. Amplitude are similar for both the channels .
channel A _ I data channel A _ Q data channel B _ I data channel B _ Q data 21563 -19040 -20188 20775 21574 -19013 -20226 20743 21607 -18998 -20256 20718 21584 -18966 -20277 20729 21640 -18936 -20300 20665 21655 -18916 -20307 20643
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency. so there has be some mismatch in the front end chain of the high speed ADC PCB. Let me check that.OK you checked that and it looks close enough, just ADC noise variation expected. Now the phase is different, sort it out.
Also check your I/Q are not swapped by mistake.
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency.OK you checked that and it looks close enough, just ADC noise variation expected. Now the phase is different, sort it out.
Also check your I/Q are not swapped by mistake.
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency.OK you checked that and it looks close enough, just ADC noise variation expected. Now the phase is different, sort it out.
Also check your I/Q are not swapped by mistake.
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency.OK you checked that and it looks close enough, just ADC noise variation expected. Now the phase is different, sort it out.
Also check your I/Q are not swapped by mistake.
Hello,No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency. so there has be some mismatch in the front end chain of the high speed ADC PCB. Let me check that.
--- Updated ---
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency.
--- Updated ---
No I have rechecked. My I and Q are not swapped. the offset increases with respect to frequency.
Yes, I do have the datasheet of high speed ADC. PFAHi
post#48 now.
Is there a progress in finding the problem .. or better say finding a solution?
I guess we never have seen a schematic. I dot understand why ...
I still can not find results and conclusions when both ADCs are fed with identical signal.
One can find out whether it is a constant time delay ... or a filter characteristc delay (analog or digital filter, wanted or not wanted filter).
(A constant time delay would cause twice the phase shift .. on twice the input frequency. Phase and frequency are proportional
A filter may cause 0..90° phase shift [per order] .. and will NOT be linearely proportional to frequency)
I just had time for a quick view through the (incomplete) datasheet.
* in post#1 you talk about "simultaneous sampling". How? The ADC datasheet does not mention "simultan*" at all. Maybe it is, maybe not...
* when searching the (incomplete) datasheet about "phase" ... then it often mentions "calibration". Did you do the ADC / chip calibration?
Do you have the full dataheet? Because the calibration is not explained in the incomplete datasheet?
* the datastream has some latency. It is given as "typical" values only. No MIN and no MAX specification! .. so: unknown.
Klaus
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