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IWR6843AOP: NLOS Interference Mitigation for Indoor Dense Radar Deployment

Jenn-Bing Ong
Prodigy 75 points
Part Number: IWR6843AOP

Hi TI,

We have a scenario of indoor patient monitoring (10m x 10m), 10 - 20 radars deployed for vital sign and posture detection. The radars are not synchronized in terms of transmission, many shared the same chirp design and functionality, the radars transmission power can go up to 15 mW, but they point at different directions to cover the whole area.

The time of flight is << 0.1us (10m max. range), therefore I vary the chirp idle time by 0.1us between the radars to minimize probability of interference, no dithering techniques has been applied to preserve the signal quality.

My questions are:
(1) Is the mitigation technique mentioned above useful ?
(2) Without synchronization, what are TI recommendations for non-line-of-sight interference mitigation for indoor dense radar deployment ?
(3) How to measure the success of the mitigation techniques applied ?

Best Regards,
jenn

  • +1
    TI__Mastermind 23177 points

    Hello Jenn,

    Just to confirm, have you referred to our Interference Mitigation app note that we have for mmWave devices? You mention varying chirp idle time which I believe is still technically dithering, as we provide the tools to apply an offset to chirp slope, chirp start frequency, and the chirp idle time. Also the guide covers examples of waveforms and heatmaps that include and exclude interference. As far as a specific technique of interference mitigation that is best for cluttered indoor environments, I will need more time to look into.

    https://www.ti.com/lit/an/swra662a/swra662a.pdf

    Best Regards,

    Pedrhom 

  • 0 in reply to Pedrhom Nafisi
    Prodigy 75 points

    Hi Pedrhom,

    Thanks for your quick reply.

    Yes, I have gone through the comprehensive TI documentation and videos on interference mitigation.

    I will look into the waveforms and heatmaps that include and exclude interference, right now I am looking into the Interference mmWave Demo Visualizer to analyze the noise level with / without interference, but I am not sure this would work for parallel interference in our case.

    Appreciate if you can recommend some specific mitigation techniques that is best for cluttered indoor environments.

    Best Regards,
    jenn-bing

  • +1 in reply to Jenn-Bing Ong
    TI__Mastermind 23177 points

    Hello Jenn-Bing,

    The 'signal and image band' monitor would work best in a cluttered environment to detect interference. It works as follows - the complex baseband allows the separation of the signal band - i.e. the positive frequencies corresponding to positive delays when using a positive slope), , and the image band (i.e the negative frequencies corresponding to negative delays). Since there can be no negative delay, there is no signal in the image band (except thermal noise). It is in that sense clean, when an interferer cuts across the inband of the victim, even if it is weak, we can see it in the image band. In the signal band, since there may be strong tones (due to strong reflections) weak interferers may not be seen. That being said, simpler techniques such as 'first difference' also works very well here.

    Best Regards,

    Pedrhom