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IWR1443BOOST: short range through glass window

Marcin S
Prodigy 60 points
Part Number: IWR1443BOOST
Other Parts Discussed in Thread: IWR1443

Hi,

I need to put the radar in the enclousure with the glass window. Ultimately, I will need to detect obstacles as cloud of points at a distance of about 3m. I made the test by placing IW1443BOOST in 2cm behind the glass window and put two cups at a distance of about 0.5m. I saw that through the glass the radar "can see" the cups much worse. In addition, it "sees" fake objects at a distance of up to 10cm and sometimes fake points appear at a greater distance. I also noticed that the radar better detects the cups on 2Tx antenna config than on 3Tx antennas. My config was:
- range res: 0.047m
- max unambiguous range: 2.41
- range detect tresh: 9dB
If I set the lower threshold value, it was better to detect the cups, but of course there were also more fake points detected.

Please tell me how to correctly configure IWR1443BOOST to "see" well through the glass window at small distances.

Thanks in advance.

1) IWR1443 through glass (2Tx config):

2) IWR1443 without glass (2Tx config):

  • 0
    TI__Mastermind 30405 points
    Hi Marcin,

    We are looking into your query and will get back to you within this week.

    Thanks
    -Nitin
  • 0 in reply to Nitin Sakhuja
    Expert 2065 points

    I am also interested in knowing if this sensor can measure well trough glasses.

  • 0 in reply to C
    TI__Mastermind 30405 points

    Hi Marcin,

    Thanks for the patience. Glass can be used as a Radome but there are some important considerations which should be taken into account:

    1. Optimum thickness: The optimum thickness of glass depends upon the Dielectric constant and Frequency range. If we assume a dielectric constant (Dk) of 4.7, the optimum thickness of glass radome for 77GHz operation is about 0.9mm. A glass sheet thicker than 0.9mm will generate a lot of reflections from the glass itself. Additionally, a strong reflector at close distance can also cause the signal to bounce back multiple times between the reflector and antenna which would show up as harmonics (stray targets) which you are probably seeing in your setup.

    2. Shape of the Radome: The shape of the radome is very important. An appropriately designed curved glass should allow more radiation to pass through it and so it is better for a Radome as compared to a flat sheet which will reflect more energy. This is also shown in the experiment named: Detecting Walls of different materials. The results table for Glass wall shows that the Glass wall itself is detected strongest when the incident angle is 90 degrees which represents a flat surface. For incident angles of 45 degrees and 15 degrees the reflection from the wall itself becomes weaker while the object behind the wall becomes stronger.

    Please mark this thread answered if this resolves your query otherwise get back in case you have more questions on this topic.

    Thanks

    -Nitin

  • 0 in reply to Nitin Sakhuja
    Prodigy 60 points

    Thank you for the information. I did the test through a flat glass sheet about 10mm thickness. I need to have such a thick glass to provide high impact resistance. The minimum glass thickness I can use is about 8mm and I would like to have maximum radar range only about 4m. Can the use of other radar antenna help with such a thick glass?

    Regards,

    Marcin

  • 0 in reply to Marcin S
    TI__Mastermind 30405 points
    Hi Marcin,

    Can you please provide more details about your application requirements specifically: Maximum range (you already provided 4m), Field of View, Target RCS and Target velocity? Thanks.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    Prodigy 60 points
    Hi Nitin,

    I want to test the radar in tunnel. The tunnel have 6m width and 4m height. One radar should look at the half of the tunnel (left or right side), so 3m width and 4m height. In this space I want to detect the side wall of the tunnel and vertical steel support (simplifying this support is a pole about 30cm wide and high like a tunnel). Detection of the side wall and support will be performed only on a distance from 2.5m to 3.5m, so I assume a maximum radar range of 4m, and I am not interested in anything under 2m. During detection, the radar will not move, but it may rotate, and during this rotation it may be set at an angle of 0 to 40 degrees with respect to the side wall (the radar will always be set at a acute angle to side wall: 40 deg or less). Of course, as I wrote earlier, the radar must be shielded by a thick glass or possible other material that is transmitting radar waves but also protects against impact.

    Regards,
    Marcin
  • 0 in reply to Marcin S
    TI__Mastermind 30405 points
    Hi Marcin,

    Sorry for the delayed response. The sensor should be able to detect behind an 8mm thick glass. Regarding ghost objects: Glass is a strong reflector and especially at such close distance (2cm) can produce multiple reflections which show up as ghost objects. You can try to reduce RX Gain in the profile config command (please refer to the mmWave SDK documentation for details on the profilecfg parameters) but it will also affect the overall detection performance for targets of interest.

    You could try the experiment with an acrylic plastic sheet (e.g. Lexan) which is very robust and has a lower dielectric constant than glass. Again, as discussed earlier, the shape of the Radome is also critical: a properly designed curved Radome would allow more radiation to pass through thus reducing the probability of ghost objects.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    Prodigy 60 points

    Hi Nitin,

    Thank You for info about Lexan. I have already ordered PTFE sheet (teflon) for testing purposes, because it also has a very low dielectric constant. Of course, in my case the glass does not have to be transparent. But the lexan, which You proposed, should be more resistant to damage (better impact resistance), so I will test it too. What shape of radome will be the best - hemisphere? pyramid?

    Regards,
    Marcin

  • 0 in reply to Marcin S
    TI__Mastermind 30405 points
    Hi Marcin,

    The ideal shape of the Radome will depend upon the number of TX and RX channels you plan to use but in general, a hemisphere would be better choice.

    Regards
    -Nitin