Can you comment if I can characterize VPHS performance evaluation of AD8302 using AD9854 EVAL kit.
I am not an expert of AD8302. Looking at some of the thread about AD8302, I came upon this thread:
It was noted there that the 2 input power levels should be as close to each other.
As I have understood your question, the input of your AD8302 will be taken from AD9854.
The output of AD9854 is close to each other because the current output depends only on one variable, the RSET. Just make sure that you terminate I and Q with the same load impedance.
The AD9854 is a quadrature digital up converter. The output I (IOUT1 and IOUT1B) and Q (IOUT2 and IOUT2B) are sine and cosine outputs so the outputs are 90 degrees out of phase.
To check if the output of AD9854 is compatible with the input of AD8302, we have to check:
1. input voltage range (IVR) of AD8302 for INPA and INPB :
AC-Coupled (0 dBV = 1 V rms) –73 min –13 max dBV
@ 50 Ω –60 min 0 max dBm
2. frequency input of AD8302
>0 to 2.7GHz
3. output voltage of AD9854
@50 ohm load, and 20mA IOUT, Vout= 1V (should not be exceeded because of compliance range)
4. output frequency of AD9854
DC to 150MHz
The AD9854 eval board has the following output:
To conclude, you can use AD9854 eval board to provide input to your AD8302 INPA and INPB.
Let me first congratulate you for drafting such a beautiful response for me.
Well, still matter remains, as you are hitting incomplete exactly to where and what it should have been.
Before, adding my inputs, I would wonder and request if you can bring Joel (the one who responds to my ad8302 queries, an expert on that) on this discussion platform / thread. Because what I'm asking him relates ad8302 and then it includes some portion of ad9854 too, which is your area. That's when my problem starts because like you said "you are not an expert on ad8302". He too saying something same that he is not an expert and rather requested someone to come on-board from "ad9854, DDS" community for that matter.
Can we get away with this impediment you think??
For me it would be a best situation conversing with both experts under one thread, as all would be reading every on-going details. That would result in pouring-in exact and much more enriched / helpful experience in terms of its contents.
Coming back to technical aspect:
I was asking you about VPHS characterization of ad8302 using ad9854 because to do that, we need to bring I/ps of ad8302 in quadrature. That is the first requirement. This brings VPHS output of ad8302 to nominal that is 900mV. From there, rest all differences of phase variations are measured between two I/ps of ad8302.
Rest, I fully agree as regards I/p limitations of ad8302 what you cited in your last post. And your detailed explanation on that considering ad9854 o/ps to clearly notice differences and feel cautious about, are worth for deciding upon use of any attenuators, if need be.
I simply feel curious to know if I can see VPHS o/p changing in steps according to I/p change applied from ad9854. This is what i.e.STEPWISE variation in magnitude at the VMAG o/p of ad8302 was observed by me using two function generators to characterize magnitude performance of ad8302. These two function generators allowed me changing I/p magnitude supply to the two I/p channels of ad8302 to observe corresponding variation in the VMAG o/p of the ad8302.
To determine "MAGNITUDE' and "PHASE' variations of the two i/p RF signals is what this IC ad8302 does, right? That's something I'm trying to validate and understand to proceed further on actual application development.
My application would require to use 100KHz-100MHz operating freq band for the I/p signals.
Can you comment as above.
Hello Dr. Babankumar,
If you change the phase of the input signals on the AD8302, it will change VPHS.
I thought the ad9854's outputs we in quadrature, always. So if you insert a load between the two parts that changes the phase, then the AD8302 should be able to measure it. Keep in mind if the phase change of the load is anywhere in the 90 degree area, your total phase will be back to 0 or 180 degrees, and VPHS will be in error.
Dear Sittie and Joel,
Thanks to both for bringing yourself on common platform.
Sittie in her last post confirmed safe use of ad9854 for applying i/p signals to ad8302. She did inform her point with detailed explanation supported with actual calculations considering ad9854 EVAL board's component as well as absolute limitations, and ad8302's i/p limits. I appreciate these details.
Joel said: as soon as phase on the i/p channels of ad8302 varies, it is measured successfully as long as such i/p channel phase variations are kept within +/- 15 To +/- 165 deg range. Beyond this range, phase linearity error would surface as per TPC 26.
Can you both now comment on my intention to check VPHS o/p on ad8302 for a systematic, STEPWISE phase variation applied from ad9854. Do you think, ad9854 can supply STEPWISE phase variations to i/p channels of ad8302 such that ideal ramp (+ve/-ve slope) characteristics can be plotted using VPHS o/p values for every associated i/p phase changes applied. What probably I mean is, ad9854 would apply say INPB(fixed) using its IOUT1, and vary phase on INPA using IOUT2. Can these two o/ps (IOUT1 & IOUT2) of ad9854 be varied independently to bring systematic phase variations to ad8302 for checking complete VPHS characteristics. Can ad9854's o/p be controlled independently for phase, one fixed and other variable, to check VPHS characteristic of ad8302???
zHi Dr. Babankumar,
It sounds like you can put whatever data you need into the control DAC (and thus make is a stepwise phase variation referenced to the I DAC):
That sounds good information, will also read thoroughly in ad9854. Before I do so, can you answer as below.
In summary, Can you confirm if ad9854 EVAL board allows me independent controlled phase variations, say: 1-90 degree on both o/ps:IOU1 and IOUT2. I would apply them to ad8302 then, to see VPHS o/p of ad8302.
Hi Dr. Babankumar,
Yes, you can do that by using the phase adjust registers of AD9854.
Thanks! I appreciate your response for precisely confirming my last query.
I hope you are meaning that I can use EVAL kit ad9854 to do smooth phase variations from 0-90/180 degrees in the o/ps ( IOUT1 & IOUT2).
I hope the software interface provided in case I buy ad9854 EVAL kit provides such a facility (customized phase and freq variations) within its absolute specifications, and I don't have to take extra efforts in writing software codes in controlling its registers while controlling phase / freq o/ps.
Everything, I'm expecting is facilitated by the EVAL kit of ad9854. Can you kindly confirm above so that I can firm up my decision of buying ad9854.
Can you also confirm if ad9854 is the most recent product / generation in this class of product / similar specifications?? Would you also like to suggest more recent generation / version of product compared to ad9854 which satisfies similar specs plus offers better user friendliness such as USB interface while working with EVAL kit instead of parallel port etc, in case???
Thanks and sincere regards,
Hi, Dr. Babankumar.
Yes, The AD9854 can do the smooth phase variation.
However, since you asked about an alternative part, I suggest you use AD9958.
The eval board is much more friendly (USB interface).
The output of the AD9958 eval board has:
AD9958 is a 2-channel DDS. If you want a quadrature output, you just set CH0 to sine output while CH1 to cosine output, or the other way around. This will give you a 90-degree phase difference on outputs.
Also, each DAC output is independent of each other so you can program each output independently. This is much more flexible compared to AD9854.
Hope this helps.
Thanks for all the satisfactory replies earlier. I'm diverting little bit on ad9834 that I'm possessing readily. Can I use ad9834 to safely apply I/p sweeps between 1-30MHz to ad8302 within 8302's I/p compliance levels??
I'm using ad8302's EVAL and ad9834's EVAL boards to experiment with.
Hi Dr. Babankumar.
The AD9834 eval board output is 0.6V, but this is for a 200-ohm load. A 200-ohm load should be maintained at the output of the AD9834 to be within the compliance range of the internal DAC.
For AD8302 board, the default input termination (R1 and R2) is 52.3 ohms for both. You can change these resistor values to 200-ohms since INPA and INPB are high-input impedance channels.
AD9834 board +AD8302 board will then be good to connect to each other.
The AD8302 eval board is indeed terminated in about 50 Ohms on the input, but it doesn't necessarily need to be. The actual input of the AD8302 is much higher (1k to 2k Ohms) as stated above. The reason we put the 52.3 Ohms on the board is to create an equivalent 50 Ohms impedance for a test environment (and it makes it convenient to use dBm's) , but this isn't strictly necessary because the AD8302 responds to voltage and not power fundamentally. So you could put a higher termination resistor on the input to increase to 200 Ohms to make the AD9834 happy.
Thanks to both for nicely explaining issues on my query.
Can you kindly now help to program DDS, 9834 and AD9958 for applying controlled freq sweeps (1-30MHz), phase etc to ad8302. Also, I want to read /log o/ps magnitude and phase information from ad8302 for the applied freq sweeps. The freq sweeps generated from DDS would be applied to ad8302 (INPB: fixed; INPA: load inserted). The o/ps of ad8302 would be logged appropriately. Please guide on following requirements.
1.Readily available programming libraries/drivers for DDS to o/p controlled frequ, phase etc.
2.What sampling rate and resolution of ADC would be required for my case given above to read ad8302 o/ps.
3.Readily available programming libraries/drivers for ad8302 to read its o/ps for said freq sweep
4.You may like to provide support in the cases such as: use of microcontroller; use of PC / laptop
5.Proposed driver / software can be written for microcontroller or using VB/VC++ platforms. You may kindly supply resources and guidance for both platforms.
Hi, Dr, Babakumar.
You can open another thread for your inquiry and I'll close this one since the inquiry for this thread has been answered.
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