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ADC12DJ3200EVM: ADC12DJ3200EVM input signal

FRANK1
Expert 7835 points
Part Number: ADC12DJ3200EVM
Other Parts Discussed in Thread: ADC12DJ3200

Hi Team,

A Japanese customer bought TI's evaluation board ADC12DJ3200EVM.
He has some issues on this EVM board.
He can't post by his university email , so I help him confirm these issues.

When QAM modulation wave is input into the input signal,
I think I can use ADC for DDC output I / Q data when sampling in decimation mode,
Does NCO need to set its frequency by myself at that time.
In addition, if I need to set it yourself, what kind of value is more better at this time?

Thanks for your clarification.
Regards,

  • 0
    TI__Mastermind 20541 points

    Hi Frank1,

    Yes you will need use the NCO to bring the signal down to baseband. You will have to program the NCO yourself to the correct frequency so that your signal after decimation, falls within your decimation band. 

    Regards.

    Neeraj

  • 0 in reply to Neeraj Gill
    TI__Expert 7835 points

    Hi Neeraj,

    Thank you for your suggestion that I needed to configure NCO.
    I wanna know more about NCO setting.
    For example, if I wanna sampling fc = 2.0 GHz modulation signals at FS = 3.2 GHz by JMODE10.

    At this time, FS / 2 = 1.6 GHz and the main component of the input signal appears at 1.2Ghz.
    What frequency will be set for the NCO at this time?

    Also, I would like to know how to determine the phase of NCO which needs to be set by NCO.
    As an experimental system for this experiment,
    Is the input signal only the modulation signal to be sampled?
    Or do I need a sync signal for DDC?

    BTW，I have an other query on the input bandwidth of the ADC.

    What this input bandwidth of the ADC is determined by which element of the ADC.

    Analog input BW = 8000 MHz,
    FPBW is 7.9 GHz for single channel and 8.1 GHz for a dual channel in the datasheet.

    Usually, the input bandwidth limit to the ADC was different from that of FPBW,
    and it was the recognition that the input bandwidth limitation was set smaller than FPBW, but was this wrong?

    Thank you for your advice on this further query.

    Regards,

  • 0 in reply to FRANK1
    TI__Mastermind 20541 points

    Hi Frank1,

    You should set the NCO frequency to your carrier frequency(Fc). By setting the frequency to carrier frequency you will be able to demodulate the signal to base band. 

    Analog input BW is the frequency at which the signal will drop by 3dB in amplitude when compared amplitude near DC. 

    Instantaneous BW is  max bandwidth signal that can be analyzed with ADC. It is generally calculated with the following formula. 

    Inst BW = (Sampling Frequency/2/(decimation factor) ) .

    Regards,

    Neeraj

  • 0 in reply to Neeraj Gill
    TI__Expert 7835 points

    Hi Neeraj,

    Thank you.

    Q1: Customer understands that he needs to set the frequency of the NCO to the carrier frequency (FC).
    He would like to know how to set the frequency of NCO.
    He would like to know if he can configure NCO with such an operation on the ADC ADC12DJ3200 GUI.

    Q2:For the test system, can the input signal only be the modulated signal to be sampled?
    Or does he need a sync signal for DDC?

    Q3: The frequency band that can be sampled by the ADC is instantneous BW, not the FPBW?
    In this case, Sampling Frequency = 3.2GHz, Decimation Factor = 4, (JMODE10) is Inst BW = 3.2G / 2 / 4 = 0.4G [Hz]
    Can't sample signals above 0.4 GHz?

    I'm sorry for questions about the difference between the FPBW and instantneous BW due to the limited knowledge.
    Thanks a lot.

  • +1 in reply to FRANK1
    TI__Mastermind 20541 points

    Hi Frank1,

    Yes NCO can be configured through the GUI. The setting are under NCO Configuration Tab. As shown in the Figure below. By Preset 0 Frequency the NCO frequency can be updated. 

     

    Q2:For the test system, can the input signal only be the modulated signal to be sampled?
    Or does he need a sync signal for DDC? Can you please clarify your question above. 

    Q3: The frequency band that can be sampled by the ADC is instantneous BW, not the FPBW?
    In this case, Sampling Frequency = 3.2GHz, Decimation Factor = 4, (JMODE10) is Inst BW = 3.2G / 2 / 4 = 0.4G [Hz]
    Can't sample signals above 0.4 GHz?

    The Max bandwidth of the signal in JMODE10 is 0.85*(3.2G/4) = 680MHz but signal can be centered around any frequency up to 8GHz(analog bandwidth of the ADC) given it not spread across Nyquist zone. For example you can have a signal 680MHz wide signal centered around 4GHz and you can use the DDC to bring the signal down to baseband. 

    Regards,

    Neeraj

  • 0 in reply to Neeraj Gill
    TI__Expert 7835 points

    Hi Neeraj，

    The customer appreciates your careful explanation。

    very professional.

    Thanks a lot.

    Have a good day!