AD9910 EVALUATION BOARD DRIVER
The product detailed below complies with the specifications published by RS Components. It really only measures PM-noise. You have chosen to save the following item to a parts list:. Furthermore, the Agilent SSE also uses the mixing method. There is absolutely no difference of the resulting noise plots within the accuracy of the measurement method 1dB. Suspicion existed regarding the actual DDS chip revision being used on my prototype board, because it is a pre-production chip obtained through the early sample program before the AD was officially released.
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Without the bypass capacitor, the AD is noticeably worse than the AD, but it shows the same characteristic plateau effect with borad cutoff frequency at an offset of around KHz from the carrier. Another elegant and simple method to measure sideband noise, including phase noise, is the Crystal Notch Filter Method. The reason why ADI did this “optimization” is unclear.
PM-noise cannot be filtered away easily, but AM-noise can be scrubbed of by carefully clipping the carrier with a squarer. On the borad hand if you really need a clean sinus wave output with or even without bit resolution AM, and excess AM-noise cannot be tolerated, the reality is that then there is a problem. Whether it ebaluation be actually done is something evaluuation only ADI can tell!
Notch Filter Method results Another elegant and simple method to measure sideband noise, including phase noise, is the Crystal Notch Filter Method. More about that can be found here: In order to leave these extra factors out of the measurement a different method was needed to drill down further into the problem.
The five main areas to look for the source of the noise are: The following analyzer screen shot shows the Biard 0dBm carrier at The mixer method would also allow for much more flexibility like measuring at different frequencies and also much closer-in than was practically possible with both the notch and the reciprocal mixing method.
EVAL-AD Evaluation Board | Analog Devices
The tests with that evalaution also proved that the pre-production chip is not causing the problem. Although chances are slim when two different methods produce quite similar results, it cannot be ruled out completely. Sending feedback, please wait Therefore we have to use more specialized phase noise measurement methods.
The foregoing information relates to product sold on, boarv after, the date shown below. Save this item to a new parts list. Suspicion existed regarding the actual DDS chip revision being used on my prototype board, because it is a pre-production chip obtained through the early sample program before the AD was officially released.
This test scrubbed yet another possibly noisy candidate from the list! This firmly indicates that the reference clock is not the cause of the excess sideband noise of the DDS.
Also the cutoff point is at roughly the same offset. If the internal band-gap device is not thoroughly filtered, then the noise will end up directly in the output signal of the DAC.
Analog Devices Direct Digital Synthesiser (DDS) Evaluation Board for AD9910
The five main areas to look for the source of the noise are:. They produce relatively much noise up to a few hundred KHz out and then drop off quickly towards the thermal noise floor. Crystal Notch Filter Method. However there is a vast improvement possible when the bypass capacitor is a9910.
Save to an existing parts list Save to a new parts list. Just scrub of the AM-noise with a squarer and use the square wave instead of the sinus wave output signal. ac9910
My homebrew regulators are using a band-gap voltage reference that is de-noised with an RC filter cutting off at 0. So ADI’s DDS design lab was contacted with a detailed report on the AD noise plateau and the effort made so far to find the source of the problem, including full details on the 2 measurement methods.
It also shows that the reciprocal mixing method is working quite well, because the notch filter method confirms its results. The answer to the question whether it is an insignificant design flaw or a pretty serious one that the AD produces orders of magnitude more AM-noise than its documented PM-noise, depends on the application where the evaluatiob is used for.
The unit is only specified for good frequency stability, evaluaation its phase noise is probably not in the same class as the Wenzel oscillator, but still no difference in the end result. So the change could even be made in a backward compatible way without invalidating existing designs that don’t care so much about the AM-noise.