This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

ADC32RF80: Questions related to sampling rate.

Part Number: ADC32RF80

The sampling rate appears to be fixed at 2949.12 MSPS.

Is it possible to change the sampling rate?

If so, how do I change it?
Which part of the data sheet should I look at?

What does offset correct mean?

  • Hi Taemin,

    Yes, it is possible to change the sampling rate (1.5 to 3 GHz). Are you using the ADC32RF80EVM? There are some preset frequencies that can be generated by the onboard LMX2582. Additionally, you can use an external clock source (along with jumper modifications). Please refer to the ADC32RF80EVM User's Guide for more information.

    Offset Correction offers digital correction of gain mismatch between the ADC cores. This helps reduce distortion and other unwanted effects when the ADC cores are sampling.

    Best Regards,

    Dan
  • In reply to Daniel Brock36:

    Hi,Dan

    I will wish you happy new year. ^^

    While using ADC32RF80EVM, I have the following questions.

    It was a question about RF frequency according to NCO setting.

    Below is a summary of the actual RF frequency calculated by the NCO settings.

    NCO set Wanted frequency RF frequency Offset

    D908               2500.2MHz           2500.2MHz 0Hz

    D906               2500.1MHz          2500.11MHz 10KHz

    Q: Can I set the RF frequency in units of 100 KHz without offset in the ADC32RF80?

        I want to use 2500.1, 2500.2, 2500.3MHz....

            Sample clock: 2949.12MHz.

  • In reply to Taemin Ahn:

    Hi Taemin,

    Happy New Year to you, as well!

    I'm not certain as to what you mean by "without offset in the ADC32RF80?". Are you referring to the offset correction? If so, yes, you can adjust the NCO in 100 kHz steps with no offset correction.

    The NCO can increment in 50 kHz steps, so using the frequencies (2500.1 , 2500.2, etc...) will work ok.

    Best Regards,

    Dan

  • In reply to Daniel Brock36:

    Hi Dan

    If you refer to the photo attached to me, put D906 and I will get 2500.11MHz.

    Conversely, if you enter 2500.1MHz for frequency, D906 is output.

    There is a difference between 2500.11MHz and 10KHz. I hope to get 2500.1MHz exactly.

    If you have a way, please let me know what is the correct way to make 2500.1MHz.

  • In reply to Taemin Ahn:

    Hi Taemin,

    Since the clock rate (Fs) we are using here is 2949.12 MHz, and the resolution of the NCO is 16 bits, the NCO can only move in approximately 50 kHz steps.  2949.12 MHz/65535 = 45 kHz.

    From the datasheet (pg 46, 8.3.4.5), we can see that, if Fs is lowered, the NCO step size will decrease. In order to get the NCO to have a 10kHz step size, Fs must be set to 655.35 MHz. 65535*10kHz = 655.35 MHz.

    You can also test this assumption in the GUI in order to see that the NCO register bits do change when making a 10 kHz increment.

    Unfortunately, this does not solve your immediate issue since the lower Fs doesn't allow for an NCO output above 655.35 MHz, so I do not see a way to achieve the 10 kHz NCO step at 2500 MHz.

    Best Regards,

    Dan

  • In reply to Daniel Brock36:

    Hi Dan

    Thank you for your dedicated help.

    I was wondering about this, but my customers want 2500.1MHz to be accurate.

    I will look for other ways.

    If you have any other chip solution, please ask for it.

    Thanks again for your help.

    Best Regards,

    Dan

  • In reply to Taemin Ahn:

    Hi Taemin,

    One other solution I can offer would be using an ADC that has a finer resolution NCO. The ADC12DJ3200 is a dual channel, 3.2 GHz clock ADC with a 32-bit NCO, to name a few features. Taking a look at the image below, with the Fs clock set to 2949.12 MHz (as we had used before), the NCO steps in roughly 0.7 Hz increments.

    Hope that helps.

    Best Regards,

    Dan

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.