3 Replies Latest reply: Jan 12, 2012 3:01 AM by Harald Naumann RSS

Antenna movement

Novice

Hi all! First let me say - great community. I'm new in this area so i apologize for some newbie questions that i'm going to ask. I'm a mech. engineer, and i'm managing a project which will have a wireless connected device embedded. I'm not personally designing the wireless device (obviously:), but i would like to know as much as i possibly can. So to make a long story short, my first question is how does rotation of the device (GPRS and GPS) influence signal strength (physical model - imagine a cell phone attached to a 10 cm (4 in) long cord on one end and the other end of the cord is in your hand spinning the phone around 200 rounds per minute) ? Does circularly polarized antenna solves the problem ?

 

Thank You in advance.

  • Re: Antenna movement
    Harald Naumann Expert

    Johnny, GSM and GPS has limitation in speed. If you turn your device then you just have to calculate the velocity

    http://en.wikipedia.org/wiki/Velocity

    Civil GPS is limited in speed. At GSM you will sooner or later run in trouble with the Doupler effect.

    • Re: Antenna movement
      Novice

      Thank You for the answer Harald.

       

      I have opened two discussions wich i think are pretty similar (my initial ignorance, i apologize) so i will continue only with this one.

       

      In theory circularly polarized antennas would have better performance for my aplication (my conclusion-not neceserrily true:), but in practice, i can't seem to find circ. pol. embedded GSM/GPRS antennas on the market. Are there any ? If not, will linearly polarised antenna work in rotating conditions ?

       

      Thank You ina advance.

      • Re: Antenna movement
        Harald Naumann Expert

        Just rotated your mobile phone and see what will happen. If you seach on Google, then you will find hints on speed limitations of GSM /GPRS. GSM is using a parameter called Time Advance. See also http://www.gsm-modem.de/gsm-location.html

        You device will move fast, but the TA can be still the same. In my opinion it will work. Just test it with your phone. Set up a voice call and glue a small buzzer to the microphone and then start to rotate.
        If you use a smart phone with GPS, then you can do the same. Just write some code that will store the GPS data to the SD card.