IWR6843: The spur of the TX output of IWR6843

Hao Liu3

Intellectual 380 points

Part Number: IWR6843

When i set the IWR6843 into CW mode output, and the radar output 61GHz cw signal.

but always it has some spur move around the signal just like the video, all the frequencys is the same.

i confirm the enviorment do not have this spur and the demo board of ODS also has the spur just like my board.

So could you give me some advices?

my config file is ：

sensorStop
flushCfg
dfeDataOutputMode 2
contModeCfg 61 0 0 2600 0 0 30 0 1024
channelCfg 15 1 0
adcCfg 2 1
adcbufCfg -1 0 0 1 1
sensorStart

over 5 years ago

0 CHETHAN KUMAR Y.B. over 5 years ago

TI__Mastermind 25835 points

Hello,

Is this custom board or TI ODS EVM measurement?

There is a known errata for the Doppler spurs. You might see lower amplitude spurs, closer to these frequencies.

http://www.ti.com/lit/er/swrz087a/swrz087a.pdf

Do you see these spurs appearing in Range/Doppler heatmap?

Thanks and regards,

CHETHAN KUMAR Y.B.

0 Hao Liu3 over 5 years ago in reply to CHETHAN KUMAR Y.B.

Intellectual 380 points

Hi CHETHAN

1、 I test my board and TI ODS EVM, the spur is the same.

2、As you say，the spur is at non-zero doppler bin because of the non-linearity of synthesizer. but i set the the mode is CW but not FMCW. so does it also has the spur ?

3、Also i think if it is a doppler spur, it cause by phase. So i only can get it from the data of ADC and can see it due to 2d-FFT. but can not catch it by Signal Analyzier.

How can i understand this spur? Does my understand is right?

Thanks

0 Hao Liu3 over 5 years ago in reply to CHETHAN KUMAR Y.B.

Intellectual 380 points

Could you give me more information?

Thank you.

0 CHETHAN KUMAR Y.B. over 5 years ago in reply to Hao Liu3

TI__Mastermind 25835 points

Hao Liu3,

2) Yes, it's because of the non-linearity of synthesizer, Yes, you would see in CW mode as well.

3) Yes, you are right, You can get it from the data of ADC and can see it due to 2D-FFT, You would see it's (Spur) effect more prominently if the RF bandwidth is smaller (say <500MHz) and FMCW signal crosses 62.1GHz in that band. For larger RF bandwidth this effect is minimal.

This is a known errata in the silicon, Customers need to avoid this frequency during their chirp design to overcome this problem.

Thanks and regards,

CHETHAN KUMAR Y.B.

0 Hao Liu3 over 5 years ago in reply to CHETHAN KUMAR Y.B.

Intellectual 380 points

OK ,I get it ,thanks

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IWR6843: The spur of the TX output of IWR6843