IWR6843ISK: A shift in the detected distance

Mahmoud Abdelgelil

Part Number: IWR6843ISK
Other Parts Discussed in Thread: MMWAVEICBOOST, IWR6843

Hi,

we were trying to conduct distance measurement tests for an object using (IWR6843+MMWAVEICBOOST+DCA1000). Every time we do measurements we find about 8 cm shift from the actual distance ( this for far field measurements). So, we have some questions

1) does this shift happen due to the the connection between the chip and the antenna in IWR6843 as in below figure (I highlighted the transmission lines while using TX0 and RX0)

2) if this distance shift is due to the length of the transmission lines, then what is the actual length of these transmission lines?

3) Can I compensate this delay during measurement ?

4) Do you have an actual calculation for this delay for different chirps, as I saw slight differences for this delay for different chirps

5) At short distances (<5cm), we saw that this delay is varying, so does this delay changes at short distances or there are extra effects at such low distances?

Thanks,

Mahmoud

over 2 years ago

0 E. Shareef over 2 years ago

TI__Genius 15810 points

Hello,

What tool are you sing for this measurement? Could you use the online mmwave demo visualizer tool to look at your data and send us a screenshot of the same?

Thanks,

-Shareef

0 Mahmoud Abdelgelil over 2 years ago in reply to E. Shareef

Prodigy 20 points

I am using mmwave studio. I have collected some data from it as below.

The chirp used parameters is

Parameter	Value
Idle time (us)	7
ADC start time(us)	5.99
Ramp end(us)	19.82
Slope (MHz/us)	199.987
ADC samples	64
Sample rate (ksps)	5000

for a target at 2cm with Tx0 we detect ~10.5 cm at Rx0

for a target at 4cm with Tx0, we detect ~14cm at Rx0

for a target at 10 cm with Tx0, we detect ~17.5cm at Rx0

for a target at 30 cm with Tx0, we detect ~38.43cm at Rx0

It seems that from all different distances that there is a shift in the detected distance. Also, when I change the Tx and Rx used I got different distance but within the range of +/-1cm .

0 CHETHAN KUMAR Y.B. over 2 years ago in reply to Mahmoud Abdelgelil

TI__Mastermind 25835 points

Hello Mahmoud,

Range bias of ~8cm is expected in the far field measurement for the ISK board, This delay could be different for different boards. You are right, this is function of delay of transmission line and on chip routing delays.

You could compensate with the calibration, you could refer below appnote /e2e post for Range bias and Gain/offset compensation.

mmWave Production Testing Overview https://www.ti.com/lit/an/spracx7/spracx7.pdf 1.2.2 Range Bias and Receiver Channel Gain/Offset Compensation

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/987480/mmwave-sdk-radar-range-bias-and-rx-gain-compensation

Thanks and regards,

CHETHAN KUMAR Y.B.

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IWR6843ISK: A shift in the detected distance