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AWR1843BOOST: Question about angular resolution in the ROS Driver

Longyi Zhan
Prodigy 20 points
Part Number: AWR1843BOOST
Other Parts Discussed in Thread: AWR1843

Hello！

When using the ROS engine to generate mmWave point clouds, I noticed that the point cloud distribution forms an arc. Moreover, on the azimuthal plane, the spacing between points is very close, with an angular separation of approximately less than 2 degrees relative to the radar. However, to my knowledge, the azimuth angular resolution of the AWR1843 is only about 15 degrees. Why is it that when obtaining point clouds using the ROS engine, the angular separation between two points is 2 degrees? The same issue also occurs on the elevation plane.

  • 0
    Prodigy 20 points

    What I would like to add is that these two points are very close to the radar in terms of distance; are they resolved in terms of lateral distance? Additionally, the spacing between the point clouds behind the figure increases, while their angular separation remains constant. Why does the spacing between points increase as the distance from the radar increases?

  • 0 in reply to Longyi Zhan
    TI__Expert 7735 points

    Hello,

    Thank you for reaching out over E2E regarding your questions on angular resolution! While the angular resolution of the device is 15 degrees, points can still be resolved based on their distance or velocity. In the case of the configuration used by the ROS driver, the distance resolution is 0.044 m which should be able to detect the points shown in your image.

    As for your latter question, you are likely getting fewer points and larger separation due to the limitations of angular resolution since an object at a great distance will occupy a lower percentage of the azimuth and elevation FOV, but you are still retaining a few points due to the range resolution. This could also be because the angular resolution deteriorates at wider angles - i.e., angles away from boresight. 

    Regards,

    Kristien

  • 0 in reply to Kristien Everett
    Prodigy 20 points

    Hello Kristien,

    Thank you for your reply. I understand the response to the first question. But regarding the response to the second question, I may not have expressed it clearly. In the point cloud obtained directly in front of the radar, the distance between points will also increase as the distance from the radar increases. But the angle interval between points remains constant. What I want to know is, how is this angle determined? It has an angular resolution far less than 15 degrees。

  • 0 in reply to Longyi Zhan
    TI__Expert 7735 points

    Hey, 

    The angular resolution is determined from the following equation: angle resolution = 2/N, where N is the number of virtual antennas/channels in a given plane. For the 1843, there are 8 azimuth virtual channels and 2 elevation channels, hence an azimuth resolution of 15 degrees and elevation resolution of 58 degrees. I would recommend giving a quick read through this E2E post or reviewing the angle estimation section of the following application note, https://www.ti.com/lit/pdf/swra554, for more information.

    What you might actually be seeing is ghosting. This is a common phenomenon caused by multi-path reflections from an object in an environment, especially if the object is moving or the scene is cluttered or reflective. Your best bet to mitigate this from occurring is to increase the CFAR threshold to detect fewer points or decreasing the output power of the device. This can be done by modifying the second to last parameter of cfarCfg and the txOutPowerBackoff command in the .cfg file. Keep in mind this may affect the ability of the radar to detect target objects, so you may have to play around a bit before you get something acceptable.

    Hopefully this helps but let me know if you have any more questions!

    Regards,

    Kristien