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IWR1443: ADC sampling rate

user5769462
Prodigy 50 points

Part Number: IWR1443
Other Parts Discussed in Thread: IWR1642

Hi, 

In the Ti document mmwaveSensing-FMCW-offlineviewing_3, it says that the adc sampling rate sets a limit on the max range the radar can detect. I agree, as longer range requires a higher bandwidth of the IF signal, hence larger sampling frequencey. It says in the paper that F_s >= 2*S*d_max/c, which means the sampling frequence must be bigger or equal to the IF signal's bandwidth, but according to Nyquist sampling principle, shouldn't the sampling rate be at least twice the highest frequency of the IF signal, i.e. the bandwidth of the IF signal?  By looking at configurations of either 16xx or 14xx of some applications, they also imply the same thing.

I wonder why.

Thank you and regards.

  • 0
    TI__Mastermind 37500 points
    Hello,
    The RF portion and ADC sampling is at a much higher frequency, 900Msps or 1800Msps from the quadrature mixer, and dual ADC.
    the DFE provides filtering, decimation, IQ correction, resampling, and tuning (Complex 1x mode). If the profile FMCW design is incorrectly
    set for the 2*distance, Synthesizer slope, and DFE output rate (has .45 Complex 2x filtering, .9 Complex 1x filtering, .45 Real DFEoutrate* x), then the
    Rx reflection is not seen.

    There is an online Sensing Estimator tool that allows you to setup your use case. " training.ti.com/mmwave-sensing-estimator-overview ""

    DFE output mode, and output rates do limit the distance that can be seen. Also the RCS of the target and the Tx integration time (Radar equation).
    Complex 2x (-Fs/2 to Fs/2) DFE rate 2 - 18.75Msps, positive frequency distance .2 - 8.44Mhz IF, negative frequency for interference mitigation
    Complex 1x (tuned 0 - Fs), DFE rate 2 - 18.75Msps, positive frequency distance .2 - 16.88Mhz IF, no negative frequency
    Real (0 to Fs - only 0 to Fs/2 used as 1st Nyquist zone), DFE rate 2 - 37.5Msps, positive frequency distance .2 - 16.88Mhz, 1st nyquist zone

    Regards,
    Joe Quintal
  • 0 in reply to Radio-Joe
    Prodigy 50 points
    Hi,

    Could you first specify which type of zoom fft algorithm is used?

    Regards.
  • 0 in reply to user5769462
    TI__Mastermind 37500 points

    Hello,

    The High Accuracy Lan for IWR1443, and IWR1642 is available in the Mmwave Industrial Control Toolbox, the User Guide attached here, discusses finding the peak object magnitude, then interpolating, to create the higher number of points.

    The precompiled project and source code can be downloaded for your use.

    Regards,

    Joe Quintalhigh_accuracy_16xx_lab_user_guide.pdf