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IWR6843: Minimal adcStartTime and end time

Johanwww
Intellectual 500 points
Part Number: IWR6843
Other Parts Discussed in Thread: MMWAVE-STUDIO, AWR1642BOOST, MMWAVE-SDK

Hi

Do you have any data on how small it is possible to make the adsStartTime and the time between the end of the ADC sampling and the rampeEndTime?

We want to use as much of the ramp as possible for sampling and we are right now assuming that there are no irregularities in between the start of the transmission of the chirp and until after the rampEndTime. We know of the overshoot and undershoot that occurs after the rampEndTime and on the ramp down to the starting frequency.

  • 0
    TI__Mastermind 30405 points

    Hi Johan,

    1. ADC Start time: As mentioned in this app note, there is no hard minimum requirements for ADC valid start time but it should be selected keeping in mind the various settling times (synthesizer, HPF and LPF) to get a good "beginning of chirp" signal. We have not collected any data on how the selection of this parameter affects the start of chirp for a particular chirp profile so you'll need to experiment yourself. There is a Ramp Timing Calculator in MMWAVE-STUDIO which provides the various ramp component timings for different settling cases (99%, 95% etc) which you can use to collect the resulting samples to analyze the signal quality.

    The following discussion may also be useful in this context: AWR1642BOOST: Understanding changes in "TX start time" and "ADC valid start time"

    2. Excess Ramp Time (i.e. time between the end of the ADC sampling and the rampeEndTime): Again, there is no minimum requirement for this time but we generally set the ramp end time to include 1us of excess ramp time in the sample profiles provided in MMWAVE-SDK demos. Here again, you can experiment using the Ramp Timing Calculator to find the best trade-off between total occupied bandwidth vs signal quality for your particular chirp profile.

    Hope that answers your questions.

    Regards

    -Nitin