IWR6843: The difference between Antenna coupling signature removal and the static clutter removal

Hi Nitin

Thanks for your reply.

I understand the two functions. My point is that both the DC coupling (between TX and RX) signature and the near range reflection from a Radome/enclosure should be in the zero doppler bin since TX, RX, and radome are all stationary. Is this true?

If so, the static clutter removal is a more general method as it removes the static targets/points in all the range bins.

Thanks!

Kai

The short answer to your question is you are right - if you enable static clutter removal, you don't need to do antenna coupling measurement and removal procedure.

They serve different purposes. When you enable static clutter removal, you cannot detect any static objects in the scene. When you are interested in detecting static objects, weak objects near the radar sensor may not get detected if you don't do the antenna coupling signature removal procedure. This is a calibration procedure the intent of which is to remove high reflections in the near range bins due to antenna coupling and/or radome. You may wonder why we need all this processing, why we simply don't throw away these range bins in all processing when there will never be an object of interest to detect say within the radome? The point of this is that the back and forth reflections may extend the dc energy beyond the physical extent of the radome for example (ghost objects) and it is for those range bins that this matters because any weak objects present close to the radar risk being not detected due to the overwhelming energy from the reflections due to radome and coupling [The range bin width in physical space is also playing a role here, if you have a range bin representing way beyond the physical radome extent, you will have to worry about this]. So basically what you do is you first see in controlled conditions where you don't have any real objects [that you don't intend to cancel] in the scene and everything is static and see how far the "halo" or "glow" of the radar extends (you can see in range profile), pick the number of range bins for measurement, do the measurement and feed this measurement for all subsequent actual sensing which will continuously subtract the measurement. So now in the sensing if you have any objects present in the range bins involved in the measurement, you will detect them, whether static or moving.

Hi Piyush

Thanks for your detailed response.

I have a little confusion on the following statement. I can understand if antenna coupling signature removal is used as a calibration procedure without weak objects near the radar sensor because the high reflection from radome or TX-RX coupling in the near range bins could be saved to calibrate the further measurements. But antenna coupling signature removal procedure is not helpful when it is not used as the calibration, i.e., weak objects are near the radar sensor because their reflections are removed in antenna coupling signature removal as well.  

"When you are interested in detecting static objects, weak objects near the radar sensor may not get detected if you don't do the antenna coupling signature removal procedure. This is a calibration procedure the intent of which is to remove high reflections in the near range bins due to antenna coupling and/or radome."

Thanks!

Kai

During measurement, your environment should have no external objects in the range bins involved in the measurement [unless these objects are going to be always there forever and you want to cancel them]. Now when you start sensing using the measurement, you will be able to detect objects near the sensor. If you didn't do this, you may fail to detect the near objects.

Hi Piyush

Does the sensor save the measurements without external objects? Otherwise, how can it tell whether the measurement includes external objects or not? In my understanding, everything including external targets in the near range bins will be removed when antenna coupling signature removal is enabled unless the measurements without external objects are saved.

Thanks!

Kai

The signature procedure is a calibration procedure that is done in controlled conditions. The goal is to measure the signature so you cannot have any objects that you don't intend to cancel out once you start applying this one time measurement in the real sensing.  Please read the full doxygen documentation that was pointed out earlier. Thanks

Hi Piyush

I checked Antenna coupling signature removal in the doxygen file in the following location but didn't find that it mentions the signature procedure is a calibration procedure.

file:///C:/ti/mmwave_sdk_03_03_00_03/packages/ti/datapath/dpu/rangeproc/docs/doxygen/html/dpu_rangehwa.html

Thanks!

Kai