AWR1642BOOST: + DCA1000 EVM ::: mmwave studio Range FFT :: Peak at zero range

The peak in range bin 0 is due to Rx/Tx coupling

thank you

Cesar

Hi Cesar,

Thank you for your reply, however, I have a few queries about it. You said " The peak in range bin 0 is due to Rx/Tx coupling ". After your reply and indication towards the cause, I searched the TI website and found following good and relevant posts ( I am mentioning them for my reference and for those who have similar query like me):

https://e2e.ti.com/support/sensors/f/1023/t/783763?AWR1843-Why-block-points-cloud-when-range-less-than-0-25m-in-SDK-demo

https://e2e.ti.com/support/sensors/f/1023/t/776876?tisearch=e2e-quicksearch&keymatch=coupling

https://e2e.ti.com/support/sensors/f/1023/t/817780?tisearch=e2e-sitesearch&keymatch=IWR1443BOOST

1-  Although i prefer not to work on TI mmwave Demo Visualizer and I prefer and I am working on TI mmwave Studio and I try to work on the ADC data acquired through DCA1000 EVM, yet, after going through above posts, I referred the user guide of mmwave SDK at C:\ti\mmwave_sdk_03_03_00_03\docs and I referred CLI command " calibDcRangeSig " which states that " Antenna coupling signature dominates the range bins close to the radar. These are the bins in the range FFT output located around DC. "

From the above posts, I also referred the profile_2d config at " C:\ti\mmwave_sdk_03_03_00_03\packages\ti\demo\xwr16xx\mmw\profiles ". 

I learnt that the CLI command " cfarFovCfg  " is used to exclude the data from the range bins that lie quite near to the radar and in the profile_2d config, data received from the range bins that lie from 0 to 0.25 m from the radar , is discarded. (Note : This command also gives limit for discarding data beyond an upper limit of range as well).

From this, I understand that TI recommends 0.25 m as the minimum distance for placing a target. Can I assume it as a general recommendation for avoiding Rx/Tx Antenna coupling ? 

2-  I further learnt that CLI command " CLI command " calibDcRangeSig "  of TI mmwave SDK calculates the DC signature from the number of range bins dictated in this command and then it removes the DC signature level from the SUBSEQUENT bins (and it does not remove this calcualted DC signature from the range binds defined int his command).

However, CLI command " calibDcRangeSig " cannot / does not remove the relatively broader peak occurring at 0 range bin and adjacent closer bins in the range profile. Is my understanding right ?

3-  Today, I did a little experiment with TI mmwave studio. I did not use any Window operation. For a certain target and parameters configuration, I obtained the following figure:

Then, I used the "remove DC" option from the Miscellaneous options of mmwave studio and I obtained the following figure:

I am unable to see any observable difference between the two plots except that a vertical line now appears at 0 range after removal of DC. Can you please explain this? Furthermore, I dont see that the operation defined by calibDcRangeSig of SDK is performed for DC removal in mmwave Studio.

Are CLI command calibDcRangeSig of mmwave SDK, and, DC removal option of mmwave Studio two different things? If yes, then can you please elaborate the difference ? 

4- Can you please elaborate a bit more on Rx/Tx coupling and / or advise some TI document(s) which address this issue in somewhat detail ?

5- Can you say that this peak at 0 range will ALWAYS be there and can we say that it is a normal behaviour ?

6- In continuation of question no. 5 above, are there some way(s) to remove this peak at 0 range ? If yes, then please advise about them ?

7- Is their any relation for the width and height of this peak against the range or frequency or some other parameter ? I mean that can we estimate and predict the width of this peak from some parameters of TI mmwave sensors or scene parameters ? This question is important because then, I must realize this fact that I will not be probably able to detect a target if it falls within the the area under this peak at 0 range bin?

Thanks and regards.