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AWR1843BOOST: Frequencies of each samples acquired

Titouan Tyack
Prodigy 55 points
Part Number: AWR1843BOOST
Other Parts Discussed in Thread: DCA1000EVM

Hi,

Following my previous question here: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1306352/dca1000evm-awr1843-not-receiving-raw-datas-as-expected, I would now what are the exact frequencies acquired by the ADC. Regarding mmwaveSensingEstimator, with the following configuration, and the above diagram given in (https://www.ti.com/lit/an/swra553a/swra553a.pdf?ts=1628143440604), my understanding is that the F0 (First frequency acquired by ADC) = Ft (last frequency acquired by ADC) - Valid_Bandwith(which is equal to FreqSlope*Num samples/SamplingRate), am I right ? If yes, for a chirp of 256 samples, does the 256 frequencies correspond to F0 + n*FreqSlope/SamplingRate ?
Or does F0 = freqSlope * adcStartTime + startFreq(77e9) ? Then what would be the vector of frequencies ?

Thanks.
Regards
Titouan

  • +1
    TI__Genius 12916 points

    Hey Titouan,

    Thanks for posting your question on sampling and ADC data. Your initial equations for determining the start frequency - assuming you know the last sampled frequency - and the frequency associated with each sample are correct. The other equation you proposed for the start frequency using the ADC start time would also be valid but might not be as accurate due to the synthesizer ramp up settling time which means the chirp slope prior to the ADC start time is not constant/stable, so the frequency spanned during that time might differ from the ideal/calculated value. The synthesizer ramp-up settling time and other factors are mentioned in Section 5.2 of the Programming Chirp Parameters app note you referenced.

    Let me know if you have any other questions.

    Regards,

    Kristien

  • 0 in reply to Kristien Everett
    Prodigy 55 points

    Hi Kristien,

    Thank you for your answer. I wanted to know because there is an important gap between the results of each way to compute the first frequency. It could be nice to write the calculation somewhere in the documentations of DCA1000EVM maybe. Thanks again.

    Regards,
    Titouan

  • 0 in reply to Titouan Tyack
    TI__Genius 12916 points

    Hey Titouan,

    I'm glad I was able to help! I will look into potentially working in more calculation information in the documentation for the DCA1000EVM. Thank you for letting us know about this gap!

    Regards,

    Kristien