What should I know when using two radars?

Discussion in 'X4M03' started by jaeyong, Jul 2, 2019.

  1. jaeyong

    jaeyong New Member

    1. I would like to implement a program that uses two X4A04 and Raspberry pi to determine the position when an object appears. When I used a single radar sensor, there was no problem in detecting the distance of the object.
    However, when two radar sensors were used, it was confirmed that it did not work properly.
    The first thing I considered was setting the distance between the two radars to 50 cm.
    The second consideration was to set the center frequency to 7.29 GHz for one radar and 8.748 GHz for the other.
    But the results of the program did not change.
    So, I want to know what to consider when using two radar sensors.

    2. I wonder if it has the ability to stop and restart the radar sensor.
    I thought that if you set the fps value to '0' through x4driver_set_fps () function, the radar would stop working.
    And then I thought radar would work again if I set the fps value to something other than '0'.
    But it was not. How can I stop and then restart the radar?
     
  2. Charlie Shao

    Charlie Shao Moderator Staff Member

    Hi Jeayong,
    1. I have verified the two module work at same space before, this problem should not be caused by interference between modules, see how X4 modules avoid interference on this thread: https://www.xethru.com/community/threads/interference-on-the-frequency-band-with-other-devices.654/
    I reckon you use two modules with one raspberry, if it is true, I suggest you verify two separate kit( single X4M07+RPI) can work at the same space. If it works, it is highly suspect the (two X4M07+RPI) program has a problem.

    2. I did a test with modified MC python script, it also works, see the attached script and pay attention to the following codes:
    Code:
            count = count+1
            if count == 170:
                xep.x4driver_set_fps(0)
                print ("10 seconds passed, stop radar and restart after 5 seconds")
                time.sleep(5)
                xep.x4driver_set_fps(17)
     
  3. jaeyong

    jaeyong New Member

    Hi Charlie,

    Thank you for answer.
    I confirmed that I can stop sensor using xep.x4driver_set_fps(0).
    Previously my code had an error.
    Always thanks a lot Charlie. : )
     
  4. jaeyong

    jaeyong New Member

    Hi Charlie,

    I have an another question.

    1.
    If one radar is stopped, is there any interference while the other radar is operating?
    If there is no interference, can I reduce the distance between two radars to 50 cm or less?

    2.
    As the data sheet of X4M07_radar_sensor_rev_a_preliminary.pdf
    Does the antenna gain (dB) mean that only positive areas are detectable by radar? In other words, does it mean that azimuth can only be measured with radar if it is around -60 to +60?
     
    Last edited: Jul 11, 2019 at 4:23 PM
  5. Charlie Shao

    Charlie Shao Moderator Staff Member

    1. They still have in-band interference, but the hardware and software can make their performance reliable. I have done the test with two X4M200 sensors standing side by side, then I did not feel any difference compared with a single sensor. For your case, I suggest you do a similar test.
    2. PCB antenna covers 360 degrees, but they have different sensitivity in different directions. Anttena pattern describes this feature, see X4M07 datasheet chapter 4.