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Does TI's MMIC has STC function?

Yang Tianxi
Intellectual 525 points

Some radar  system support  function of Sensitivity Time Control, does TI's MMICs support STC?

Thank a lot.

  • 0
    TI__Mastermind 23725 points

    Hello Yang,

    Can you please elaborate further on this function or provide an example usage to get context.
    I am assuming you are referring to Radar RF side of things here, however more information would help us with answering the question.

    Thank you,
    Vaibhav

  • 0
    TI__Guru 58035 points
    Hello,
    The receiver gain in the TI MMIC is programmable by the user in the profile config API. There is 24 dB programability at 1dB step size, so using this the receiver gain can be changed based on the requirement.

    regards,
    Vivek
  • 0 in reply to Vaibhav Mahimkar
    Intellectual 525 points

    STC menas Sensitivity time control (STC),this is an issue in radar system, pls refer to following

    11.6.1 Sensitivity Time Control
    One method to increase the dynamic range of receivers is to decrease the sensitivity of the
    radar for near-range returns. Sensitivity time control (STC) is normally accomplished by
    inserting an attenuator between the duplexer and the receiver front end or LNA. Typically
    around 30 dB, the maximum attenuation (Figure 11-22) is switched in either at or just prior


    to transmit time. A short time following pulse transmission, the attenuation is decreased as
    the range increases. Decreasing the attenuation as a factor of R−4 would maintain constant
    amplitude for a given target RCS, whereas decreasing it as a function of R−3 would hold it
    constant for pulse-limited clutter RCS. Reducing the attenuation following an R−3.5 rule
    provides a compromise between both. The STC attenuation present at short ranges helps
    prevent receiver saturation from strong targets or clutter, and then as the range is increased
    the attenuation is reduced to enable detection of small RCS targets.


    it means low gain for near targets to avoid saturation, high gain for far target to ensure SNR

  • 0 in reply to Vivek Dham
    Intellectual 525 points
    That means user can achieve STC via programable gain of receiver of MMIC,right?
  • 0 in reply to Vivek Dham
    Intellectual 525 points
    to elaborate this issue further, I depict scenario as below, with time of a chirp increasing, the gain of the receiver can be programmed to decrease atomatically, does TI MMIC support this function?
  • 0 in reply to Yang Tianxi
    TI__Guru 58035 points
    Hello Yang,
    The exact implementation of STC as you described is in context to pulsed radar while the TI MMIC is FMCW radar. In the FMCW context you can change the RX gain every frame via software if required. So you can have one frame with RX gain 48dB, next frame with RX gain 47 db and so on.
    I am not sure if this meets your purpose.

    Regards,
    Vivek
  • 0 in reply to Vivek Dham
    Intellectual 525 points

    According to your explanation, RX gain can be changed from chirp to chirp, question still here, during ONE chirp, RX gain is fixed at a constant value, not changeable right?

  • 0 in reply to Yang Tianxi
    TI__Guru 58035 points
    Hello Yang,
    That's right , the gain during a chirp would be fixed.

    Regards,
    Vivek
  • 0 in reply to Yang Tianxi
    TI__Prodigy 545 points
    Hello Yang,

    For the FMCW modulation format, the equivalent for STC is the high-pass filter in the IF stages. As close-in objects show up at lower frequencies, they are naturally suppressed by the high-pass filtering, leaving the far objects unattenuated. With a second-order high-pass filter, the overall channel response can be completely compensated. As the HPF poles can be programmed independently, you can create different compensations to address the near-far problem and scene dynamic range.

    This is in addition to the variable gain that is available within the receiver to handle the object RCS variation and any uncompensated channel response.

    Regards,
    Brian
  • 0 in reply to bginzz
    Intellectual 525 points

    Hi Brian,

    Your explanation is very reasonable, STC attenuates gain of near objects to avoid saturation, this is essentially same as a practical HPF.

    HPF and variable gain offer  alternative solution to saturation problem.