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AWR2243: ADC start time vs Sample rate

user244678
Expert 1375 points

Part Number: AWR2243

Hi,

I would like to ask about ADC Start Time in mmWaveStudio's Profile configuration.

Is there any dependency between the ADC Start Time and Sample Rate settings?

For example, if the SampleRate is slow, I would like to know if there is a possibility that the AWR2243 is actually securing a longer ADC Start Time than the set value.

Best Regards,

Hiroyuki

  • 0
    TI__Mastermind 20605 points

    Hi Hiroyuki,

    There should be no dependency on the actual ADC start time based on the Sampling rate. As far as the actual ADC start time, it will be whatever is set to.

    That being set, the minimum ADC start time required for the chirp to linearize will be dependent on the slope. For slopes less than 50 MHz/us you can have ADC start time as less as 1us but for slopes greater than 50MHz/us it is suggested to go with a minimum time of 2.5 us.

    Hope this answered your question. Let me know if further support is required.

    Happy Holidays!

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    Expert 1375 points

    Hi Kaushik.

    Thank you for your reply.

    I understand that there is no dependency between adcStartTime and sampleRate.

    Currently, I am checking the waveform by acquiring ADC RAW data with the ramp timing shown below.

    adcStartTime is set to 3.64us against the 95% settling value 3.32us.

    However, looking at the obtained IF waveform, it seems to be quite unstable immediately after sampling starts.

    Other parameters are:

    rameEndTime = 23.3us

    idleTime = 6.01us

    txStartTIme = 0us

    This instability can be resolved by increasing rampEndTime and delaying adcStartTime, but in order to satisfy the required measurement performance, it is not possible to increase rampEndTime.

    Is there any workaround?

    Best,

    Hiroyuki

  • 0 in reply to user244678
    TI__Mastermind 20605 points

    Hi Hiroyuki,

    Let me check regarding this internally and get back to you by Jan 2nd latest.

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    TI__Mastermind 20605 points

    Hi Hiroyuki,

    Here are some methods that you can try based on inputs from the team to adjust the settling time of the filter:

    1. Increase HPF cutoff freq
    2. Reduce RF gain or TX power
    3.  Check if on board TX RX isolation can be improved
    4. Increase sampling rate

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    Expert 1375 points

    Hi Kaushik,

    Thank you.

    I will try methods 1 and 2.

    Regards,

    Hiroyuki

  • 0 in reply to user244678
    Expert 1375 points

    Hi Kaushik,

    I tried methods 1 and 2, but no improvement was seen.

    On the other hand, increasing the sample rate seems to be effective.

    Unfortunately, it is not possible to increase the sample rate in this application, but why would increasing the sample rate improve the performance?

    Regards,

    Hiroyuki

  • +1 in reply to user244678
    TI__Mastermind 20605 points

    Hi Hiroyuki,

    Digital filter settling depends on the rate at which filter runs, which depends on sampling rate. Adjusting the sampling rate would change the filter's settling time directly.

    Regards,

    Kaushik