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IWR6843AOPEVM: How to calculate the size of range bin?

plefert
Prodigy 60 points
Part Number: IWR6843AOPEVM

Hello, I have some questions about the topic: range bin.

I use the vital sign monitoring on the IWR6843AOPEVM and would like to calculate the distance to an object.I only get the range bin from the radar module, so I wanted to calculate the range resolution and estimate the distance.

The calculation is explained in the following article:

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/873304/iwr6843-mmwave-sensing-estimator-discrepancies

I use the following vital_signs_AOP_2m.cfg. file:

% SDK Parameters
% See the SDK user's guide for more information
% "C:\ti\mmwave_sdk_[VER]\docs\mmwave_sdk_user_guide.pdf"
sensorStop
flushCfg
pmicCfg 1 1
dfeDataOutputMode 1
channelCfg 15 7 0
adcCfg 2 1
adcbufCfg -1 0 1 1 1
lowPower 0 0
%
% Detection Layer Parameters
% See the Detection Layer Tuning Guide for more information
% "<RADAR_TOOLBOX_INSTALL_DIR>\source\ti\examples\People_Tracking\docs\3D_people_tracking_detection_layer_tuning_guide.pdf"
profileCfg 0 60.75 30.00 1.00 10.00 0 0 200.0 1   96 10785.00 2 1 36
chirpCfg 0 0 0 0 0 0 0 5
chirpCfg 1 1 0 0 0 0 0 2
chirpCfg 2 2 0 0 0 0 0 5
frameCfg 0 2 48 0 90.00 1 0
dynamicRACfarCfg -1 4 4 2 2 8 12 4 12 5.00 8.00 0.40 1 1
staticRACfarCfg -1 6 2 2 2 8 8 6 4 8.00 15.00 0.30 0 0
dynamicRangeAngleCfg -1 0.75 0.0010 1 0
dynamic2DAngleCfg -1 1.5 0.0300 1 0 1 0.30 0.85 8.00
staticRangeAngleCfg -1 0 8 8
fineMotionCfg -1 1
bpmCfg -1 1 0 2
antGeometry0 -1 -1 0 0 -3 -3 -2 -2 -1 -1 0 0
antGeometry1 -1 0 -1 0 -3 -2 -3 -2 -3 -2 -3 -2
antPhaseRot 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1
fovCfg -1 70.0 20.0
compRangeBiasAndRxChanPhase 0 1 0 -1 0 1 0 -1 0 1 0 -1 0 1 0 -1 0 1 0 -1 0 1 0 -1 0
%
% Tracker Layer Parameters
% See the Tracking Layer Tuning Guide for more information
% "<RADAR_TOOLBOX_INSTALL_DIR>\source\ti\examples\People_Tracking\docs\3D_people_tracking_tracker_layer_tuning_guide.pdf"
staticBoundaryBox -1.5 1.5 0.3 1.75 0 3
boundaryBox -1.5 1.5 0.5 2 0 3
sensorPosition 2 0 15
gatingParam 3 2 2 2 10
stateParam 3 3 12 215 50 6000
allocationParam 20 100 0.1 20 0.5 20
trackingCfg 1 2 800 1 46 96 90
presenceBoundaryBox -1.5 1.5 0.3 1.75 0 3
maxAcceleration 0.1 0.1 0.1
%
% Vital Sign Parameters
% See the 3D People Counting with Vital Sign User's Guide for more information
%
vitalsign 15 300
VSRangeIdxCfg 0 21
%
% Start the Sensor
%
sensorStart

According to mmWave Sensing Estimator I get a range resolution of 8.4cm. I wanted to recalculate this using bandwidth, number of samples per chirp and number of range FFT bins.

Question 1:
Using the mmWave Sensing Estimator I have given a Valid Sweep Bandwidth of 1.78025 GHz. However, I actually use a bandwidth of 2 GHz. Which bandwidth is correct now?

Question 2:
What is the Number of Range FFT bins? Where can I get the value?

I would be very grateful for any feedback!

Best regards,
Patrick

  • 0
    TI__Genius 17877 points

    Hello Patrick,

    We will get back to you early next week.

    Best Regards,

    Pedrhom

  • +1 in reply to Pedrhom Nafisi
    TI__Expert 8970 points

    Hi

    Range bin multiplied by the range resolution would provide the distance of the person

    1. Even though you have configured a 2GHz bandwidth, effective bandwidth used by the sensor would be 1.78025 GHz. This is because the initial few adc samples and if the ramp time is more than the number of adc samples programmed, it would result in wastage of bandwidth

    2.Number of range FFT bins is next rounded off number of 2 pow n for number of adc samples. For example, in this case number of adc samples is configured for 96, number of range fft bins would be 128. It is the number points of FFT that is applied on the adc samples

    Regards