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IWR1443: IWR1443 doppler spur issue

Wesley He
Expert 6205 points
Part Number: IWR1443

Hello team,

Customer is built their own IWR1443 board with LP87524J power solution.

SDK version: 2.1.0 OOB demo

clutterRemoval enable, and peak grouping disable.

When the radar board towards to open air. We can see some(less) detection point at 1.3m and 2.6m.

When using hand cover the board, we will see a lots of detection points shown on 1.3m and 2.6m. 

The target frequency is always at ~800KHz. It looks like the leak from TX-RX that cause this issue. but why it will have doppler spur at 1.3m and 2.6m?

And how to avoid it? Is it a silicon issue?

CFG shown below:

sensorStop
flushCfg
dfeDataOutputMode 1
channelCfg 15 5 0
adcCfg 2 1
adcbufCfg 0 1 0 1
profileCfg 0 77 192 7 50 0 0 80 1 240 5714 0 0 30
chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 4
frameCfg 0 1 16 0 100 1 0
lowPower 0 1
guiMonitor 1 1 0 0 0 0
cfarCfg 0 2 8 4 3 0 1280
peakGrouping 1 0 0 1 229
multiObjBeamForming 1 0.5
clutterRemoval 1
calibDcRangeSig 0 -5 8 256
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 5 123 0
CQSigImgMonitor 0 119 4
analogMonitor 1 1
sensorStart

Thanks,

Wesley

  • 0
    TI__Mastermind 25835 points

    Wesley,

    I suspect this problem is due to insufficient filtering of PMIC ripples. It could be possible that PMIC clock frequency harmonics showing as ghost objects. 

        Have you tried this on the IWR1443Boost EVM? 

    You could try increasing Capacitor values on the PMIC (LP87524J) output (additional 22uF cap on each of the rails), This will help in reducing the ripple. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    TI__Expert 6205 points

    Hello Chethan,

    Thanks for your reply. Issue solved.

    It's because the PFM/PWM auto select mode in 1.2V power rail on LP87524J.

    Compare with 6843 and 1642, the 1443 needs less 1.2V current. So the LP87524J will be switch from PFM->PWM while processing, and switch PWM->PFM while idle. Or it stay at PFM mode all the time. so it create a dopper spur with the switch frequency change in 1.2V power rail.

    After changging the PFM/PWM auto select mode to force PWM mode on LP87524J using IIC. The issue solved.

    Regrads,

    Wesley

  • 0 in reply to Wesley He
    TI__Mastermind 25835 points

    Wesley,

         Great, Yes that explains very well on resolving this issue.

    Thanks for going extra step on this direction to resolve this issue.

    Really appreciate your initiative. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.