• State TI Thinks Resolved
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 32 subscribers
  • Views 128 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

IWR6843ISK: maximal beat frequency

Piotr Banach
Prodigy 40 points
Part Number: IWR6843ISK

Tool/software:

Hi everyone,

I’m currently making some tests with an IWR6843ISK EVM, and I have a question about the maximal beat frequency (and hence the maximal unambiguous range) that can be reached. The max beat frequency is lower than the full ADC sampling rate due to prior LPF, but in TI’s mmWave Sensing Estimator the max beat frequency is computed as 0.8 * f_ADC (with f_ADC the ADC sampling rate), while in TI’s parameter tuning application report (https://www.ti.com/lit/an/swra553a/swra553a.pdf?ts=1734050219685&ref_url=https%253A%252F%252Fwww.google.com%252F) it is computed as 0.9 * f_ADC.

So which one is the “true” value, 0.8 * f_ADC or 0.9 * f_ADC, and why?

This was already discussed in a previous thread (https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/822521/awr1642boost-the-beat-frequency-from-swra553-pdf-is-not-consistent-with-the-mmwave-sensing-estimator-v1-3-why) but no final answer and explanation were given.

As an example, in the attached range-Doppler map containing the full range axis (so not cut at the max unambiguous distance yet) obtained with Complex_1x sampling mode, cutting beat frequency values beyond 0.9 * f_ADC would mean cutting the map beyond 22.32 meters, and cutting beyond 0.8 * f_ADC would mean cutting the map beyond 19.845 meters, which would remove amplitude peaks hence potential radar targets (unless these are aliased components from further targets), so these few meters can be important.

Thank you in advance for your help!

Best regards,

Piotr Banach

  • 0
    TI__Mastermind 33200 points

    Hi,

    It looks like this range-doppler map gives you all the way up to 1X the sampling rate (24.8 m). It is your decision how high to make the max range here - it looks like you can use 0.9 or 0.8 as the multiplication factor. Your risk of aliasing is relatively small because objects that are further away (and would have higher IF frequency returns) will have reduced detection power because of the 1/R^4 relationship between range and power for FMCW radar. No matter whether 0.8 or 0.9 is the multiplication factor, if you have an object whose detection power exceeds the 5 MHz bandwidth, an aliased frequency could appear at the baseband frequency, and you could have a false alarm detected near the radar when the true object's location is far from the radar, but you can reduce this risk by making the frequency slope lower if you expect to detect large SNR targets at long distances away.

    Best,

    Nate