Inside a GSM antenna

Discussion in 'Wireless & RF Design' started by Martino Chiro, Mar 9, 2019.

  1. Martino Chiro

    Thread Starter Member

    May 1, 2015
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    What components there are inside a GSM antenna ?
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    Any GSM antenna in particular?
     
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  3. Yaakov

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    Jan 27, 2019
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    Antennas, per se, are passive and don’t contain any components. They are, themselves, inductors with resistance and capacitance (like all components). They resonate if properly tuned, and may include external matching networks, which are sometimes contained in the “radome”, the container for the antenna, which is transparent to radio frequencies.

    So, you might find inductors and capacitors closely connected to antennas, but, in the case of a GSM antenna, it is most likely the a fancy bit of PCD tracing or a simple radiator with no components directly on it. If you include the matching network, then it might have capacitor and inductor components to make it function.
     
  4. Martino Chiro

    Thread Starter Member

    May 1, 2015
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    Many thanks Yaakov,
    do you know some book or web site that is involved in the antenna construction, manufacturing, design,
    in the GSM, GPRS and GPS area ?
     
  5. Yaakov

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    Unfortunately, no. What is your goal?
     
  6. bertus

    Administrator

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    Hello,

    Have a look at the attached PDF.

    Bertus
     
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  7. Martino Chiro

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    May 1, 2015
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  8. Yaakov

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    Jan 27, 2019
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    That is an active antenna. It is not just an antenna, it requires a power supply, so it has some active circuitry in it. This could be an amplifier, maybe with some sort of filter. The antenna itself is not powered, but the amplifier in the radome needs it.

    So this is really two things, being imprecisely called by the name of one.
     
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  9. Martino Chiro

    Thread Starter Member

    May 1, 2015
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    Many thank Bertus
     
  10. Martino Chiro

    Thread Starter Member

    May 1, 2015
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    Due to a labeling error on a quantity of this type of antenna, i need to recognize GSM from GPS antenna.
    I try with a capacitance meter, to measure each one, but i'd like to know what is inside GSM (GPS)
    antenna, so to be sure what is the antenna i am measuring. I measure 400 - 500pF (with 2,5m of RG174 cable)
    in one antenna, and no measure (overload my tester) in the other antenna (with also 2,5m of RG174 cable).
    Both are SMA-M terminated.
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Wich antenna do you have?
    There are several on the give page.

    Bertus
     
  12. Yaakov

    Well-Known Member

    Jan 27, 2019
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    Well, there may be no simple measurement you can make but if you have samples of the good ones and you consistently read a certain capacitance and/or resistance that is different from the others, that might work.

    The only other way is to measure the SWR at the frequency of interests, or other resonant characteristic.

    One other idea comes to mind: the GSM antenna will be for transmission while the GPS only for reception. There may well be a strong difference at DC (capacitance, resistance, inductance) because of this.
     
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  13. Martino Chiro

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    May 1, 2015
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    The JCB008 model.
     
  14. Martino Chiro

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    May 1, 2015
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  15. Yaakov

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    Jan 27, 2019
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  16. Yaakov

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    The data sheet says there is an LNA for the GPS antenna, so it will have components to deal with the power supply coming in on the coax and that will make it different at DC than the GSM antenna. But I think the only way to be sure is open one, identify the leads, measure resistance, capacitance, and perhaps inductance on each and see how they differ.
     
    Last edited: Mar 10, 2019
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  17. bertus

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  18. Martino Chiro

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    May 1, 2015
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    I follow your suggestion.
     
  19. Martino Chiro

    Thread Starter Member

    May 1, 2015
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    I opened one unit, this is a picture of the inside. 20190313_080821.jpg
     
  20. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Now you can clearly see that the GSM antenna is connected directly to the coax.
    The GPS coax goes to the box.

    Bertus
     
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