Hi! Joel,
Thats so nice of you, appreciate your speed of answering my queries. I'm glad and grateful to you. Your answers are simple to make out.
In response to ur last answer, following is the query:
How do I phase lock sources used?
How long do I observe Vphs on scope? what should be observed on scope as a check that Vphase is changing in response to the input phase variations, I mean what is the validation of correctness informing relation between o/p changes associated with i/p changes, numerically. Say, I wish to verify: 10mV/deg i.e. Vphase outputs 10mV per 1 deg.relative change at the applied i/ps, or for that matter say, Vphs=min(30mV) when relative phase diff at i/ps =180 deg, and max(1.8V) when relative phase diff at i/ps =0 deg . Say, i wanna graph these details, so how do and where do i find data points??? I mean how do I record them using scope, is it manual-STEPWISE observations OR is it automated-SPECTROSCOPIC/SWEEPs recorded? Because, I want to plot VPHS characteristic given as below:
If you want to say, what I see on the scope is same as Figure 5 above, then how do i verify its correctness in terms of numerical values knowing what i/p corresponds to what o/p values. Can I set scope axis as phase (horizontal) and amplitude (vertical) to notice these details and make out clearly as said above???
Secondly, I wish to bring your kind attention as given below what i did practically about phase characteristic evaluation of AD8302:
Please also note, this was done before receipt of your last answer.
I possess: AD8302 EVALZ board and AD9834 EVALSDZ along with EVAL SDP-CBZ. I did use characterization setup (Fig.16) suggested in DATA sheet (AD8302) while experimenting. I wanted to see if it is possible to check complete Vphs output dynamic swing for the associated inputs.
Referring one of your answers in engineer zone posts which says:
STEP1: set 90 deg offset between two input signals derived from the same source and phase lock them using true 90 deg phase splitter to note VPHS on CRO.
STEP2: Apply two i/ps with 100KHz freq offset and read sawtooth signal on CRO@ 100KHz.
My question is:Can you share what phase splitter part/module was used exactly. Some manufacture part no.,web.link etc. if readily available?? for purchasing.
Further, can you suggest part which can synthesize input phase difference on AD8302 such that complete VPHS output swing can be observed STEPWISE (ONE AT A TIME) on CRO ???
Also, is there any set of capacitance values you can advise, which can bring phase differences in STEPS if inserted in the SIGNAL path of INPA & INPB (FIXED), derived from the same source OR may be from two different sources for that matter. Because, you know, capacitance load leads phase angle. So the path having 'C' inserted will develop diff of phase angle relative to INPB, am I right???.
I guess, that could be the simplest way of doing STEP1(90 deg.phase diff bet.two signals) and subsequent STEPWISE EVALUATION of VPHASE characteristic. Is this approach convincing to you, as cap values are easily available with most of the engineers.
EXPERIMENTATION TRIED:
Note: following was tried before your first response on my post.
I tried doing VPHS evaluation, starting with STEP2 (INPB @1.10MHz, 0dBm; INPA@1.0MHz, 0 dBm) as I was having no clue on how to do STEP1 (recording DMM and scope reading when inputs @ 90 deg phase shift). I noticed freq value of around 2 MHz (VPHS connected to scope) while I was expecting diff (1.10-1 =100kHz) when auto-scaled CRO (HP infinium 500 MHz scope).
Please see it for yourself in the attached pictures, various values that are appearing on DMM (topmost is Vref; bottommost is VMAG; middle is VPHS) and scope (only VPHS is connected). So it can be seen, neither of the values displayed on CRO and DMM match as expected except vref (1822mV on topmost DMM).
What I mean by expected values is:
VMAG = 900mv(because INPA=INPB=0dBm); what VPHS is displaying, I'm unable to make out, I mean to exactly what phase diff the displayed VPHS value is associated with ???. Also, I wish to enquire how long should I observe VPHS. I mean generally, we vary inputs in STEPS and note corresponding output values. That's what I did when I evaluated VMAG, what I call step-wise evaluation. I did it through two sources: INPB-fixed@ 1.10MHz, 30dBm; INPA-variable@ 1.0MHz, 5dBm step size.
In VMAG case, I was able to note associated variations on VMAG comfortably, they were quite visible and record-able through STEP-WISE approach.
Also, my query is, how do we do phase locking of two sources? as suggested in case of VPHS characterization. Because I'm not making any inter source connections in my set-up. I mean they are operating independently while supplying INPA & INPB, and are not connected from my side to short their grounds, phase locking or so. Even the common grounding of both the sources is happening through single ended input SMA connectors of AD8302 board automatically through cable (SMA one end and BNC other end). I'm not doing any forced efforts. While characterizing VPHS, I was trying to observe two extreme conditions on VPHS to make it more visible. That is, if I can apply 0 deg ph.diff. and observe VPHS = 1.8V, and in other case 180 deg.ph.diff and observe VPHS= 30mV. I was trying so suing two sources through continuous sine-wave burst mode which allows phase offset.
However, can we do that some how, any simple ways? like use of capacitor values as I don't have phase splitter at the moment and not sure if i'm using burst mode correctly.
NEXT QUERY:
Please refer following block diagrams:
Figure 12.(DATA SHEET, AD8302): Using the AD8302 to Measure the Gain and Insertion Phase of an Amplifier or Mixer
Figure A: Article web link (DDS Applications by EVA Murphy, Analog Devices): http://www.eetimes.com/document.asp?doc_id=1156511
I wish to use AD8302 as shown in Fig 12 above. The specific application that i intend to develop, propose to measure magnitude and phase of unknown signal (V2 of "Figure A"), which is what AD8302 is capable of doing. My load/Network/Black box will be: varying impedance value due to permittivity change. Operating freq of application range is 100KHz-50MHz. My question is: do you think I will need DCA and DCB as shown in Figure 12 above if I'm following "Figure A-concept" for developing application?? If yes, what values of DCA and DCB you will recommend? What manufacturer? Any specific part?. Will highly appreciate your inputs. Also, In case I don't know exact power swing of load/network/Black box I'm measuring, can still tentatively will it be possible for you answer what ATTENA and ATTENB (Figure 12, above) are required, any mfg part no? any values to select from. May be you w'd recommend/ choose sort of variable ATTENA & ATTENB & DCA&DCB which provides flexibility to tune them as per unknown load. I know, nothing can provide blanket/unlimited flexibility but, to begin with, you may kindly recommend limited but wide range flexibility parts.I will be grateful to you.
NEXT QUERY:
o/p swing of AD8302 is 30mV to 1.8V for both (VMAG and VPHS). Also, resolution (min change) is scaled to 30mV /dB (i.e.30mv o/p @ VMAG for relative per 1 dB change at i/p) and 10mV/deg ( i.e.10mv o/p @ VPHS for relative, per 1 deg change at i/p). Question: Do you think, for digitizing outputs (VMAG & VPHS) using ADC (analog -digital converter), I need to use any buffer or amplifiers considering swing & resolution levels. I think, 12 bit ADC should serve the purpose comfortably without a need of amplifier and buffers.
NEXT QUERY:
For fabricating PCB (printed circuit board) of AD8302 based application development, do you recommend any experienced designer and fabricator who is aware of all design issues concerning AD8302. That experience helps in getting best performance of AD8302. Although, I agree, most designers are aware in general but, do we have one worked on AD8302 based designs earlier??
Attachments: as above (VPHS experimentation outputs on DMM and CRO)
Thanks and sincere regards,
Dr.Babankumar
