X2M200 baseband output

Discussion in 'Respiration Sensor' started by Davide Bongiovanni, Feb 15, 2017.

  1. Davide Bongiovanni

    Davide Bongiovanni New Member

    Hello,

    Is it possible to retrieve (almost) raw antenna data from the X2M200 instead of the Amplitude/phase or IQ messages? I am trying to develop a UWB imaging system but it's hard to work with such pre-processed signals. If not, how can Amp/Phase and IQ messages be interpreted? What do they exactly represent?
     
  2. Josh Gardiner

    Josh Gardiner New Member

    Davide,
    First, you can not get the "raw raw data" through the X2M200. The down sampled base band at 20 sample per second is it with the X2M200; which is plenty, if you really need the raw radar data, Xethru also offer the Cayenne which has access to the raw data plus much more to hit the ground running.

    There is subtly here that I will overlook, but...
    A single sample will contain a series of pairs of numbers each representing a ~4cm window.

    IQ and Phase/Amp are the same data just mapped differently, You can transform one to the other and vise versa.

    Phase/amplitude is probably the easier to get your head around than rather than IQ.
    For Phase/Amplitude the pairs of numbers are phase and amplitude:

    The amplitude is the strength of the reflected signal in a window.
    The phase gives you a relative position of that reflection in that window.

    But it of course it is all in the time domain where things get fun.
    -Josh
     
  3. Davide Bongiovanni

    Davide Bongiovanni New Member

    That's very interesting! What's your source? Do you have some further reading suggestions?

    You said that the Cayenne offers raw data output. Does the Ancho kit not offer such a thing? In that case what are the advantages of purchasing the Ancho compared to just using the X2M200? I'm guessing better antennas and maybe some more signal strength and penetration?

    Your last sentence struck my curiosity the most. What do you mean with that? Is there some interesting dynamic processing that could increase the capabilities of the X2M200? You don't have to give an exhaustive answer, some keywords that I can google should be enough :D
     
  4. Josh Gardiner

    Josh Gardiner New Member

    Both the Cayenne and Ancho have access to the raw radar as far I know just different bands, the Ancho I also believe lets you play the actual chirps. I don't have either as a few X2M200's do all what that I need for development atm.

    For reference about the interpretation of the of the data I understand mostly by experimentation, and by programming my own filters and algorithms. Xethru own documentation is good source for the specifics of the sensor and it capabilities. And quite a bit of random reading about radar and uwb systems and signal processing of them. If you need a reference for IQ to PA I can dig out my code for that, but it is just a few trig functions.

    Keeping it still simple if you look at IQ data on a polar plot reflection strength is the distance from center and rotation of a data point is movement towards or away from the sensor, within that window. Breathing facing the sensor will show a series of points rotating one way as you breathe in and rotate the other ways as you breathe out.

    By fun I mean the most interesting data is found when you apply some time domain specific algorithms to filter out noise.(although from the other post I have read of yours it might what I call noise is your signal). Mostly it is about finding the right kind of algorithms for your application/project. Things like adaptive clutter map filtering , FFT's and clustering etc. And if you add motion to the picture more interesting things show up in the data, things like multiple reflections can be used to guess at things like the geometry of a space by if and where they appear by the coordinated change in signal, although you will need a model of propagation through materials for that kind of stuff to work well. If you add time synchronised data from more than one sensor you can build complex and interesting data. For example Just a simple case of multilateration is really fun to play with once you have a reliable distance, speed and size algorithms.

    Hope that does something for you.
    -Josh
     
    Olav Liseth likes this.
  5. Je_Jordan

    Je_Jordan New Member

    Greetings,
    I am pretty naive in DSP, I had just bought X4M03. I want to see the application of the radar. As I have gone through the forum their is alot of discussion about respiration and heart rate. Can you please help me with something so that I can get started with it.
    Regards
    Jordan
    (je_jordan@aol.com)