ad9854

Dear

We are using in our current design the AD9854asvz. This already for almost 10 years. We have now some questions for our future designs.

  1. Do you have an idea how long this IC will be in the market. The because we didn’t find it anymore between the search tool for Direct Digital Synthesis & Modulators (http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators.html)
  2. Has Analog Device maybe a newer or popular IC that we can use for our application. The import specifications for our application are the following:
    • Generate fast sweeps with a programmable bandwidth with a maximum of 60MHz. RFSK (triangle) and chirp.
    • Programmable output power.
    • Operating in high temperate.

We have also another question about the AD9854asvz. With a big RRC the peaks will be okay but when you make it small there happened something strange. You can see occurring this result the the document that you can download with the link: WeTransfer

Another problem is that normally the signal will not be random. It starts every time on the same value according to FTW1 and it takes certain steps according to DFW. Now we see on the spectrum analyzer that for certain values the peak is not on the specific frequencies anymore, it looks random. For our application is this better but we don’t understand why it is random between our min and max value and that part we don’t like. I hope you can help with this problem too.

Thank you in advance
Kind regards
Stef Roelants

  • 0
    •  Analog Employees 
    on Apr 6, 2016 12:17 AM

    There are no plans at this time to take the AD9854 obsolete; it is unlikely we will make it obsolete near term unless the manufacturing chain is disrupted (for example if the package were made obsolete by our subcontractor and we could not easily transfer to a footprint compatible alternative).  Eval boards require parallel printer cables, though, and with newer products (for example AD9954, AD9956, AD9910) available, we do not expect to see a lot of new design activity with the AD9854.  I'll have to see what happened to it with regards to the IST.

    Trying to explain the plots - as you sweep, you are temporarily at various intermediate frequencies.  If I am understanding the plots correctly, then for the longer pulses, you are capturing more states in which the DDS frequency resides briefly.  If that's the reason, and you could run the lower plots longer so you capture more data, then it would start to look more like the first plot.

    As to the question about the starting point, it's not immediately obvious to me why the starting phase might affect it, but try clearing the phase accumulator before you start each sweep; this should always get you to a common starting point and be repeatable.

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:25 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin