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IWR1443: Noise of Ich is larger than Qch

Part Number: IWR1443

Hi technical support team,

A customer observed that the noise of Ich signal is larger than Qch signal.
Is this usual characteristics?
Could you pelase explain the cause of this behavior and how to resolve it?

Here I attached the data taken by the customer. Ich in blue and Qch in red.

Best Regards,
Katsuhiro

  • Hi,

    How were you able to generate these plots of just noise (no signal)? I see that the envelope of the Q channel does appear to be larger than the envelope of the signal on the I channel. Are you referring to that? Or the components close to 0 Hz on the frequency plot? 

    Best,

    Nate

  • Hi Nate

    The sensor was placed in the anechoic chamber, and the figure was the result of the measurement.
    The content of the inquiry is not about 0Hz, but about the difference between the envelopes of I and Q signals.
    (Because the red line is Q signal, I signal has a larger envelope than Q signal.)

    Best Regards,
    Katsuhiro

  • Hi Katsuhiro,

    I see that envelope difference, and I will investigate on my end. Is this interfering with measurement? Or are you just interested? Understand that a question of this depth may take some time for a thorough answer.

    Best,

    Nate

  • Hi Nate,

    Here is the comment from the customer:

    The envelope difference doesn’t interfere our measurement so far.
    However, we would like to know how the envelope difference affects vital (heart rate and respiration) data which we want to measure.
    Target is a single person indoors.

    In addition to the above,
    Is the envelope difference due to board or chip?

    Best Regards,
    Katsuhiro

  • Hi Katsuhiro,

    The envelope difference doesn’t interfere our measurement so far.
    However, we would like to know how the envelope difference affects vital (heart rate and respiration) data which we want to measure.
    Target is a single person indoors.

    I am not sure if we can trace down the chain all the way to IQ data and say how that will affect vital signs. If this is a route you want to pursue, I would suggest capturing the data in complex 2x mode and check the spectrum so that you can plot the IQ imbalance. I think this is not likely to yield a straightforward answer like "This IQ imbalance causes us to overestimate the heart rate" if that's what you're looking for.

    Is the envelope difference due to board or chip?

    You will have to try a different board/chip to see if you see the same behavior. You might also want to try the same chip but with different chirps to see if the behavior is replicable on the same chip.

    Best

    Nate

  • Hi Nate,

    Have you confirmed the envelope difference using evaluation board of IWR1443?

    If you can confirm that, could you provide whether the value of envelope difference depends on the difference of chip.

    Above is a comment from the customer.

    Best Regards,

    Katsuhiro 

  • Hello Karsuhiro,

    Apologies for the delay on this. I have been in communication with my team members on these E2Es.

    Yes, a small difference in noise floor and DC level is possible between I & Q chains if the Tx is turned ON. This wouldn’t affect the system performance however.

    Hope this helps,

    -Shareef