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IWR1642BOOST: Clarification on config trackingCfg please

TonyMakkiel
Expert 1180 points
Part Number: IWR1642BOOST

Hi,

trackingCfg 1 1 250 20 78 130 33 90

In the above example config how do I find out the highlighted fields? According to http://www.ti.com/lit/ug/tidud31a/tidud31a.pdf , page 17(and a little bit digging of the code) they are maxRadialVelocity and radialVelocityResolution. But according to the corresponding description, it should match sensor Chirp configuration. Which chirp configuration is this? I couldn't find a field where radial velocity is set. Can somebody please help?

Many Thanks,

Tony

  • Former Member
    0 Former Member

    Hello Tony,

    The maxRadialVelocity and radialVelocityResolution are derived parameters calculated from the chirp configuration you are using. The group tracker takes these two parameters for the Kalman filter and affects the velocity unrolling.

    Please refer to this application note for the equations on how to calculate derived chirp parameters: 

    Or, if you use the GUI when you load the chirp configuration, refer to the table and scroll to see the calculated values. Then modify your trackingCfg to match.

    -Amanda

  • 0 in reply to Former Member
    Expert 1180 points
    Hi Amanda,
    Isn't Max Velocity(m/s) and the Velocity Reolution(m/s) from the GUI linear velocity and velocity resolution? The reason I ask is, if I load
    ti\mmwave_industrial_toolbox_2_5_0\chirps\images\Traffic+Monitoring+Radar\mmw_tm_demo_longRange.cfg to the tm_demo ui, It reports Max Velocity as 18.0674m/s and Velocity Resolution 0.362. But the corresponding trackingCfg in the file is
    trackingCfg 1 1 250 20 189 330 50 90 which does not match.
    Many Thanks,
    Tony
  • Former Member
    0 Former Member in reply to TonyMakkiel
    Hello Tony,

    This is an error - however it isn't clear how substantially this affects the group tracker performance. Best practice would be for the trackingCfg command to match the values defined by the profileCfg.

    Here are the formulas that should be used:
    carrierFrequency = startFreqConst + (adcStartTimeConst + chirpRampTime/2)*chirpSlope; % Hz center frequency
    lambda = speedOfLight/carrierFrequency;
    maximumVelocity = lambda / (chirpInterval*4) ; % m/s
    velocityResolution[CFAR] = 2*maxVelocity/numDopplerBins

    For this configuration then,
    maxVel = 18.04 m/s and then the velRes (at the CFAR level) = 0.28m/s meaning the tracker parameters should be 180 and 28 instead.

    -Amanda