X4 PRF and range resolution

Discussion in 'X2 & X4 SoC' started by Qiwen, Jan 23, 2019.

  1. Qiwen

    Qiwen New Member

    Hi,

    I have a question with PRF setting for X4. I initially set PRF as 17Hz and I received 1536 samples in fast time. When I increased it to 34Hz, I found I still got same numbers of sample in fast time axis. Does it mean increasing PRF will also improve the range resolution? I also found when I increase PRF to 34Hz from 17Hz, the time spent to grab one frame nearly doubled. I don't understand why it happened, does it related to how sampler works in receiver side?

    Best,
    Qiwen
     
  2. NSANGOU CHOUAIBOU

    NSANGOU CHOUAIBOU Active Member

    Hi Qiwen,
    It is a normal behavior. 1536 samples is the default number of bins in your radar frame.
    The PRF is the number of pulses per second, or 1 pulse each 1/PRF second transmitted by the radar. If you double the PRF, keeping all other parameters unchanged (pps, DACmin, DACmax, etc...), you will also double the time it take to build one frame, directly related to the Frame Per Second (FPS) parameter.
    Just pay attention to the regulatory compliance !

    BR,
    Chouaibou.
     
    Last edited: Jan 25, 2019
  3. Qiwen

    Qiwen New Member

    Thanks for your reply Chouaibou. Could you explain more on why double the PRF will double time to build a frame? As you mentioned in reply, PRF setting will affect time spent between pulses. According to my understanding, total time spent to build one frame will include sweep time, frame transfer time and system overhead. While sweep time is related to 1/PRF, (DACmin - DACmax)/ DACstep, pps and iterations. Thus, if I increase PRF and leave others unchanged, the sweep time will actually decrease. If I assume frame transfer time and system overhead are unchanged, the total time spend for one frame is suppose be less rather than double.

    For my first question, you said 1536 will always be the number of bins for one frame.Can I say no matter what max range(by changing PRF) I set for the radar, say 4m (34MHz for PRF) or 9m (17MHz for PRF), it will always be sampled to be 1536 bins?

    Best,
    Qiwen
     
  4. NSANGOU CHOUAIBOU

    NSANGOU CHOUAIBOU Active Member