IWR6843ISK: Spurious reflections in FFT profile

Sanjib Sur

Part Number: IWR6843ISK
Other Parts Discussed in Thread: DCA1000EVM, MMWAVEICBOOST, IWR1443BOOST

Hello,

I have set up the IWR6843ISK+MMWAVEICBOOST+DCA1000EVM and ran the data capture demo LUA script DataCapturedemo_xWR.lua from the mmWave studio (v. 2.0.0.2). I can gather the I/Q reflections, 2D FFT, and range FFT. However, I see a very strong reflection at the 0th distance of the Radar. This is the default LUA script and the IWR6843ISK device is ES1.0. Attaching the output from the mmWave studio and the hardware picture. As you can see, there is nothing near to the Radar, but still a strong reflection at the 0th distance. Could you please help? Thanks!

over 3 years ago

0 Ishita Kochar over 3 years ago

TI__Mastermind 31680 points

Hello Sanjib,

The peak observed at range bin zero is due to TX-RX Antenna coupling.

In the past, there have been various users who have faced similar situations like this. You can use your local site search engine by typing "Site e2e.ti.com TX-RX antenna coupling in mmWave Sensor" or typing similar relevant keywords.

I have linked a similar thread below for reference using the above search method :

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/875210/awr1642boost-dca1000-evm-mmwave-studio-range-fft-peak-at-zero-range

Hope this helps.

Regards,

Ishita

0 Sanjib Sur over 3 years ago in reply to Ishita Kochar

Prodigy 30 points

Thanks, Ishita, for the links.

How can we resolve this issue or at least reduce the coupling so that spurious peaks can be minimized? Is there any filtering or windowing I can enable?

I don't see this problem on IWR1443BOOST https://www.ti.com/tool/IWR1443BOOST

or on MMWCAS-RF https://www.ti.com/tool/MMWCAS-RF-EVM

Sanjib

0 Ishita Kochar over 3 years ago in reply to Sanjib Sur

TI__Mastermind 31680 points

Hello Sanjib,

TX-RX antenna coupling is a common phenomena which can happen irrespective of the Board/EVM used. Let me consult with the relevant team members on this and get back to you with a solution or technique to minimize the effect of this.

Thankyou for your patience in this matter.

Regards,

Ishita

0 Sanjib Sur over 3 years ago in reply to Ishita Kochar

Prodigy 30 points

Ishita,

Are you saying that this effect is random and another IWR6843ISK ES1.0 device may not show this problem? Or, is this issue prevalent across all IWR6843ISK ES1.0 devices?

Note that we have used more than 10 IWR1443BOOST and have never seen this Tx-Rx coupling issue. This is the first time we saw the problem with the IWR6843ISK ES1.0 device.

Please let me know if there is any software/hardware solution to minimize the effect.

Thanks,

Sanjib

0 Ishita Kochar over 3 years ago in reply to Sanjib Sur

TI__Mastermind 31680 points

Hello Sanjib,

Antenna Coupling as I mentioned is a common phenomena. It would depend on the isolation between the Rx antennas and the Tx antennas. But it would be a stable signature for a given chirp configuration. So we can measure it, and remove it.

You can leverage the "calibDcRangeSig" CLI command that is included in the Out-of-Box Demo. This is to account for the fact that the antenna coupling signature dominates the range bins close to the radar. You can read more about this in the mmWave SDK User's Guide.

Also, I found a similar thread on the E2E platform as well, please take a look :

(+) AWR1642: Antenna coupling signature and its compensation algorithm in mmw demo - Sensors forum - Sensors - TI E2E support forums

(+) AWR1642BOOST: Constant received energy and Varing antenna coupling signature - Sensors forum - Sensors - TI E2E support forums

(+) IWR6843: The difference between Antenna coupling signature removal and the static clutter removal - Sensors forum - Sensors - TI E2E support forums

There does seem to be publicly available literature discussing antenna non-idealities such as coupling etc. which you could look up.
(e.g. a google search yielded the following paper ieeexplore.ieee.org/.../7075441)

Hope this helps.

Regards,

Ishita