IWR6843ISK-ODS: Calculate the maximum velocity and velocity resolution using the parameters in a cfg file

user5903056

Part Number: IWR6843ISK-ODS

Hi,

I'm trying to calculate the maximum velocity and velocity resolution using the pameters in a cfg file, but the results calculated using the equations below seem wrong.

max_Velocity = λ/4Tc; V_resolution = λ/（2NTc);

The following is the cfg file and the calculation details (The useful values in cfg file has been highlighted):

% ***************************************************************
% Created for Area Scanner v2.0.x
% Frequency:60
% Platform:xWR68xx
% Azimuth Resolution(deg):15 + Elevation
% Range Resolution(m):0.0703
% Maximum unambiguous Range(m):14.4
% Maximum Radial Velocity(m/s):2.45
% Radial velocity resolution(m/s):0.15
% Frame Duration(msec):100
% ***************************************************************

% *****************STANDARD MMWAVE SDK COMMANDS******************
sensorStop
flushCfg
dfeDataOutputMode 1
channelCfg 15 7 0
adcCfg 2 1
adcbufCfg -1 0 1 1 1
profileCfg 0 60.5 100 25 69 0 0 50 1 256 6000 0 0 30
chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 2
chirpCfg 2 2 0 0 0 0 0 4
frameCfg 0 2 32 0 100 1 0
lowPower 0 0
guiMonitor -1 1 0 0 0 0 0
cfarCfg -1 0 2 8 4 3 0 20 0
cfarCfg -1 1 0 4 2 3 1 15 0
multiObjBeamForming -1 1 0.5
clutterRemoval -1 1
calibDcRangeSig -1 0 -5 8 256
extendedMaxVelocity -1 0
bpmCfg -1 0 0 1
lvdsStreamCfg -1 0 0 0
compRangeBiasAndRxChanPhase 0.0 1 0 -1 0 -1 0 1 0 1 0 -1 0 -1 0 1 0 1 0 -1 0 -1 0 1 0
measureRangeBiasAndRxChanPhase 0 1.5 0.2
CQRxSatMonitor 0 3 15 125 0
CQSigImgMonitor 0 115 6
analogMonitor 0 0
aoaFovCfg -1 -90 90 -90 90
cfarFovCfg -1 0 0 11.11
cfarFovCfg -1 1 -2.04 2.04

% *****************SENSOR START*********************
sensorStart

The results I obtained were 9.917m/s and 0.31m/s, which are different with the "Maximum Radial Velocity(m/s):2.45" "Radial velocity resolution(m/s):0.15" given in the cfg file. I would like to know what's wrong with my calculation?

By the way, I am not sure how to obtain the "Number of chirps". Can I calculate it by Number of Tx * the third argument in frameCfg?

Thanks a lot.

Regards,

Jie

over 4 years ago

0 Former Member over 4 years ago

The number of chirps is the chirp loops * num of Tx.

The values at the top of the cfg file in the comments are so users can replicate the cfg generation again using the same slider/input values in the visualizer. However, there can be differences in the actual parameters from the output .cfg file. Generally the algorithm closesly approximates the input values but there can be differences.

When I run the calculations, I get values quite close to the input/slider values:

velMax: 2.4451m/s
velRes: 0.1528m/s

They are calculated using:

velResolution_mps = wavelength/(2*numLoops*numTXChannel*(idleTime+rampEndTime)/sec2usec)

velMax_mps = wavelength/(4*numTXChannel*(idleTime+rampEndTime)/sec2usec)

If you download the industrial toolbox and look in the area scanner gui there is a file claculateChirpParams.m it may be helpful to study this file to understand how to make these calculations from chirp parameter values.

0 user5903056 over 4 years ago in reply to Former Member

Intellectual 910 points

Hi AmandaN,

Thanks for your reply!

I have another question about the num of TX. As for my understanding, the second argument for channelCfg command indicates the num of TX. However, in the cfg file below, the thee TX are enabled in channelCfg, the numLoops is 32 in frameCfg, but the comments say the number of chirp intervals is 64 (These values are highlighted). Why isn't it 3*32 = 96?

% Carrier frequency GHz 60
% Ramp Slope MHz/us 166
% Num ADC Samples 256
% ADC Sampling Rate Msps 12.5
% ADC Collection Time us 20.48
% Extra ramp time required (start time) us 3
% Chirp time (end time - start time) us 21
% Chirp duration (end time) us 24
% Sweep BW (useful) MHz 3399.68
% Total BW MHz 3984
% Max beat freq (80% of ADC sampling rate) MHz 10
% Max distance (80%) m 9.04
% Range resolution m 0.044
% Range resolution (meter per 1D-FFT bin) m/bin 0.044
%
% Inter-chirp duration us 7
% Number of chirp intervals in frame - 64
% Number of TX (TDM MIMO) 2
% Number of Tx elevation antennas 0
% Number of RX channels - 4
% Max umambiguous relative velocity kmph 72.58
% mileph 45.36
% Max extended relative velocity kmph 145.16
% mileph 90.73
% Frame time (total) ms 1.984
% Frame time (active) ms 1.536
% Range FFT size - 256
% Doppler FFT size - 32
% Radar data memory required KB 272
% Velocity resolution m/s 1.26
% Velocity resolution (m/s per 2D-FFT bin) m/s/bin 1.26
% Velocity Maximum m/s 20.16
% Extended Maximum Velocity m/s 40.32
% Maximum sweep accorss range bins range bin 0.91
%
sensorStop
flushCfg
dfeDataOutputMode 1
channelCfg 15 7 0
adcCfg 2 1
adcbufCfg -1 0 1 1 1
lowPower 0 0
profileCfg 0 60 7 3 24 0 0 166 1 256 12500 0 0 30
chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 4
chirpCfg 2 2 0 0 0 0 0 2
frameCfg 0 2 32 0 100 1 0
guiMonitor -1 1 1 1 0 0 1
cfarCfg -1 0 2 8 4 3 0 15.0 0
cfarCfg -1 1 0 4 2 3 1 15.0 0
multiObjBeamForming -1 1 0.5
calibDcRangeSig -1 0 -5 8 256
clutterRemoval -1 0

compRangeBiasAndRxChanPhase 0.0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
measureRangeBiasAndRxChanPhase 0 1. 0.2

aoaFovCfg -1 -90 90 -90 90
cfarFovCfg -1 0 0.25 9.0
cfarFovCfg -1 1 -20.16 20.16
extendedMaxVelocity -1 0

CQRxSatMonitor 0 3 4 63 0
CQSigImgMonitor 0 127 4
analogMonitor 0 0
lvdsStreamCfg -1 0 0 0
bpmCfg -1 0 0 0

sensorStart

Regards,

Jie

0 Former Member over 4 years ago in reply to user5903056

Where did you get this cfg from? The comments appear incorrect. It should be 3*32. But note that is because you have 3 chirp cfg defined using 1TX each. While most of the time the number of TX enabled in channelcfg matches the number of chirps defined per transmitter (for TDM MIMO cases) this is not always the case.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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IWR6843ISK-ODS: Calculate the maximum velocity and velocity resolution using the parameters in a cfg file