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AWR1243BOOST: Interference between two AWR1243s with identical chirp configuration

Expert 2985 points
Part Number: AWR1243BOOST
Other Parts Discussed in Thread: AWR1243

Hi,

I am doing experiement about interference between two AWR1243s with identical chirp configuration.

Each PRI has 128 chirps, each chip has 512 samples. One AWR1243 is working as victim radar, the other one is working as aggressor radar.

Here is the FFT plot of 20th chirp of the data I collected on the victim radar side.

In the figure above, there is one ghost target in the positive FFT part (FFT bin:0~255), this is because the interfering chirp is below the TX chirp.

As the number of chirp increases, like 21st chirp, the ghost target  is moving in one direction. This is because of random clock drift.

What makes me confused is:

why there is a symmetric ghost target in the negative FFT part (FFT bin:256~511) at the same time?

why the symmetric ghost target in the negative FFT part is with less intensity than that in the positive FFT part?

 

Thanks!

  • Hi
    Could you let us know if you have complex-2x in the static configuration.
    If you have used complex-2x then Ghost target in the negative frequency is due to IQ-mismatch.

    Regards,
    Jitendra
  • Hi Jitendra,

    I am running mmwavelink_example in VS to capture data. It was set as complex 2X mode. So the image band will not be filtered.

    IQ mismatch is reasonable. 

    But why is there no symmetric peak in the negative frequency when the real target is presenting?

    Is it because the ghost target generated from another mmwave board has much higher power intensity, which causes IQ mismatch largely so that the symmetric peak is visible?

    Thanks!

    Feng

  • Hello Feng,
    You are right, the signal level from the other mmwave board is much higher since it sees only a one-way path loss. The reflection from a real object sees a two way path loss and hence would be typically lower in power level (keeping all other conditions same).

    Regards,
    Vivek