X4 X4M03 range resolution

Discussion in 'X2 & X4 SoC' started by Manikanta, Nov 22, 2017.

  1. Manikanta

    Manikanta New Member

    What is the range resolution of X4M03 radar? What is the sampling frequency? What is pulse repetition frequency?
    I am confused because resolution be (speed of light)/(2*sampling frequency). A resolution of 5 cm requires a sampling frequency of 3 GHz which is extremely high.
     
  2. Aksel Johnsby

    Aksel Johnsby Moderator Staff Member

    Hi Manikanta

    Maximum pulse repetition is frequency 60.75 MHz.

    The effective sampling rate is given by the receiver PLL frequency.
    F(s)= F(rx_PLL)*12

    The receiver PLL frequency is the product of the common PLL clock frequency and the feedback divider settings
    F(rx_PLL)=F(refclk)*N(fbdiv_rx)

    Using the register default values the RX PLL frequency is 27 x 8 x 9 = 1944 MHz and the sampling rate is 1944 x 12 = 23.328 GS/s

    All this information is available in the X4 Datasheet.

    Hope this clarifies :)

    Aksel
     
  3. Manikanta

    Manikanta New Member

    Thanks Aksel. Please inform me if the SDK provides access to range-Doppler images (a two-dimensional image which provides the amplitude and phase of the signal at each of the range-radial speed bins). And at what frequency can I obtain these images?
     
  4. Sruthy Skaria

    Sruthy Skaria New Member




    Hi,

    RF raw signal is 1536 range bins per frame for 9 m, which meaning there is range resolution of .006 meters. Is it correct? How does it changes when we down convert? Would you be able to help me out with this?

    Many Thanks,
    Sruthy
     
  5. Sigurd Pleym

    Sigurd Pleym New Member Staff Member

    Hi Sruthy
    The RF range bin spacing is apporoximately 6mm as you say. The downconversion also downsample by a factor of 8 giving you a range bin spacing of approximately 5.14cm and a maximum of 192 complex range bins
     
  6. Sruthy Skaria

    Sruthy Skaria New Member

    Hi Sigurd,

    Thank you so much for your advice.
    So if I take raw RF signal and then down convert digitally without decimation I can get 6mm resolution right?
    Also one question: When sampling the received signal it only takes the first 1536 sample right?? Then it will wait for next pulse..is that true?

    Kindly advice me for the same.

    Many Thanks,
    Sruthy
     
  7. Sigurd Pleym

    Sigurd Pleym New Member Staff Member

    Hi Sruthy
    If you don't downsample you can get 6mm range bin spacing at RF.
    Note: Resolution and spacing is not the same thing. Range resolution is an indication of how closely located two reflectors can be resolved into two distinct targets in the receiver. This is related to the transmitted bandwidth of the radar signal.

    For the next question: This is more complex to answer. The short answer is yes.
    The longer answer will be to read about the swept threshold technique in the datasheet. However, to build one RF frame of 1536 range bins, the chip uses a lot of pulses. The total number N is related to iterations, pulses_per_step , dac-range. When all pulses for a frame has been received, a frame of 1536 range bins is ready. The next consecutive frame of 1536 range bins will be ready when the next N pulses has been transmitted.

    Cheers,
    -sigurd-