How to work on baseband data ?

Discussion in 'X4M03' started by Abhishek Jain, Jul 9, 2018.

  1. Abhishek Jain

    Abhishek Jain New Member

    I have been working on X4M03.I have been working on raw data,putting it to some use but I feel there's too much data aka noise associated with raw data and I need to filter it out.Then i saw the baseband data.I wasn't really able to comprehend that data.I felt that the raw data at-least had some clarity.I searched on internet,actually baseband data is kinda filtered data.So any suggestions that how to proceed with the baseband data ?
     
  2. Aksel Johnsby

    Aksel Johnsby Moderator Staff Member

    Hi Abhishek Jainm,
    First of all, to obtain baseband data you will need to enable downconversion on your x4driver, this will result in a complex number output. This is called IQ-baseband, where I is the real part and Q is the complex part. These are basically vector coordinates and the magnitude of the signal is the length of the vector and the phase angle is the vectors angle from the I-axis. To convert a IQ-baseband signal to AP(amplitude and phase)- baseband signal follow these steps:

    • IQ-baseband(n)=I(n)+Q(n)i
    • Amplitude(n) = sqrt( I(n)^2 + Q(n)^2)
    • Phase(n) = arctan(Q(n)/I(n))
    If you want an example on how to work with baseband, take a look at the XEP examples in ModuleConnector. Additionally I recommend checking out the XeThru File Formats application note.

    Have a great day!
    --
    Aksel
     
  3. Abhishek Jain

    Abhishek Jain New Member

    Thanks a ton @Aksel Johnsby.
    Can you tell me what does X-axis in the baseband data represent ?
    As far as I can see, In raw-data it represented number of bins,So why they have been reduced by 8 times here ?
     
  4. NSANGOU CHOUAIBOU

    NSANGOU CHOUAIBOU Active Member

    Hi Abhishek Jain,
    In digital signal process (DSP), down conversion of RF signal to baseband signal absolutely needs LPF (anti-aliasing low pass filtering) as you have to filter out all high frequency components and make sure that all baseband samples fit the nyquist frequency band.
    If your RF signal is acquired by oversampling (many times the required Nyquist sampling criteria = easy design of the low pass filter), you can perform the decimation (removing some samples = reduction of number of samples) without any loss of information in your digital signal.
    At the same time, you will save memory in your chip by not storing unnecessay samples. This topic is well documented.

    B.R
     
    Last edited: Jul 11, 2018
    Aksel Johnsby likes this.
  5. Aksel Johnsby

    Aksel Johnsby Moderator Staff Member

    Hi Abhishek Jain,
    The x-axis are range bins, @NSANGOU CHOUAIBOU gave a good explanation on why they are reduced, each range bin represent a 5.14 cm distance.

    Have a great day!
    --
    Aksel
     
  6. Abhishek Jain

    Abhishek Jain New Member