• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 31 subscribers
  • Views 904 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

IWR1443BOOST: Is it possible to measure the RCS spectrum?

Khalid Rajab
Intellectual 262 points
Part Number: IWR1443BOOST
Other Parts Discussed in Thread: IWR1443

Is it possible to use the IWR1443 (or other chips in the range) to detect the scattered spectral response (i.e. RCS versus frequency)? Or does the matched filter inhibit us from doing this?

Objects may exhibit RCS variation with frequency, which is useful to know for classification. I would be interested to know whether this can be measured (I'd like to compare it to measurements from a quasi-optics VNA setup).

  • 0
    TI__Guru 50240 points
    Hi Khalid, This is a great question. I'll need another day to figure out the answer but will get back to you.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    Intellectual 262 points

    Thanks Akash, looking forward to your response (and will keep trying on my own in the meantime).

  • 0 in reply to Khalid Rajab
    TI__Guru 50240 points
    I am still getting information and should have an answer for you by Friday.


    Cheers,
    Akash
  • 0
    TI__Prodigy 545 points
    Hi Khalid,

    Depending on the type of characteristics you are trying to get, you could do a sequence of relatively narrow chirps with different start frequencies and then looking at the reflected signal power for each of those chirps. This would be proportional to the RCS for different frequencies, with an additional contribution due to the TX output power + RX gain variation across frequency. Within each chirp, you would get roughly the average RCS across the frequencies of that chirp.

    Given the dependence on the Pout + RXgain, which have roughly a 2dB total variation across a 2GHz bandwidth, you would need an object that has larger RCS variation than this or would have to calibrate against an object of known RCS vs. frequency (e.g., a sphere).

    Regards,
    Brian
  • 0 in reply to bginzz
    Intellectual 262 points

    Hi Brian,

    Thanks for the response. I thought it might be the case that I'd have to take multiple measurements; I'm trying another approach that might be more direct in the meantime.

    For the case of take narrow chirps, is there a hardware limitation on the minimum bandwidth?

    Regards,

    Khalid

  • 0 in reply to Khalid Rajab
    TI__Prodigy 545 points

    Hi Khalid,

    There are two basic limitations on the minimum bandwidth.  The first regards the increment of the chirp slope and minimum chirp time.  The slope can be set to zero and then incremented in multiples of ~48kHz/us.  With the minimum chirp time of around 10us, this leads to quite small bandwidths.

    The more practical limitation, however, is the high-pass filters in the baseband.  For the best sensitivity, you want the object reflection to come back beyond the HPF corner frequencies (175 and 350kHz), which means you generally would like the IF of the target to be >500kHz.  f_IF = 2*d*S/c, where d is the distance, S is the slope, and c is the speed of limit.  This sets a lower bound on slope as a function of distance: S > 500kHz*c/2d.  You can then take this and combine it with the minimum chirp time of 10us to come up with a better minimum bandwidth as a function of distance.

    Regards,

    Brian