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Original question:

IWR6843ISK: Criteria for TLV7 (SNR/noise side info)

IWR6843ISK: IWR6843ISK

Zai Mei Chen
Prodigy 10 points
Part Number: IWR6843ISK
Other Parts Discussed in Thread: IWR6843AOP

Tool/software:

Hello,

I am experiencing the same issue for on application. 

Part used: IWR6843AoP 

SDK Version: 3.5.0.4

Firmware: OOB or the demo version.

Applicaiton:  It is used for altimeter application to measure the distance to various grounds: Concrete, Grass, Wooden ship decks with metal frames underneath.

Observation:  The Altimeter worked well against the concrete, wooden deck.  When measuring against grass pads, there are geometries where the cloud point output (TLV 1 and 7) has detections with missing SNR or SNR values -1.   This gap or missing SNR gap would varies between 0.2 to over a second.

The range CFAR threshold was set to 15 dB. 

The frame is set to 100msec.  

  • 0
    TI__Mastermind 19620 points

    Hello.

    It is more likely to work well on concrete/wood because the reflection will be more direct, but when reflecting off of grass you may see a weaker return signal as it is not a "clean" reflection.  You can increase the # of chirps or reduce any backoff you may have currently to see if it improves performance on grass.  You can also try using the level sensing application as it may fit your application needs.

    Sincerely,

    Santosh

  • 0 in reply to Santosh Krishnan
    Prodigy 10 points

    Santosh, 

    Thank you for your response. I am in the process of making the following changes to see how if they make any differences.  In the meantime, could you kinda help me understand the significant of a clout point out with SNR value -1 and a valid doppler value. 

    Change 1: I am going to reduce the receiver gain to see if Tx-Rx leakage or DC term in the beating frequency has any impact on this condition. 

    Change 2: I was going to reduce the number of chirps in the hope that the radar doesn't end up with coherence process "loss" due to grass moving as the engine blade with high forced air. 

    Change 3: Per your comment, I am also going to try higher # of chirps with the hope for coherent processing gai on the target not the clutter. 

    Thanks again for your time. 

    Zai

  • 0 in reply to Zai Mei Chen
    TI__Mastermind 19620 points

    Hello Zai.

    Zai Mei Chen said:
    In the meantime, could you kinda help me understand the significant of a clout point out with SNR value -1 and a valid doppler value. 

    I don't think SNR should ever be negative, but even if it is, since it is below the threshold it should not be included in the detected objects list.  How are you reading the SNR values of the points?  I would make sure that it isn't a TLV parsing error from when you are reading the UART data.

    Sincerely,

    Santosh