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Space diversity

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  • #49906 Reply
    HuNi
    Guest

    Hi

    Can anyone please explain me how to calculate the distance between two antennas if I am using space diversity.

    Regards
    HuNi

    #49907 Reply
    pix
    Guest

    there is a formula for that… but it’s totally empirical. Better than the formula is to follow the recommendations, based on experiments :

    For GSM900 : at least 3m horizontal separation
    For DCS1800 : at least 1.5m horizontal separation

    Additional rule : if height of antenna > 10*3m (or 10*1.5m for DCS1800), then the separation should not be equal to the values above, but should be at least equal to Height/10.

    If you’re using vertical separation, then the distances are shorter but it is slightly less effective.

    Pix

    #49908 Reply
    HuNi
    Guest

    Thank you Pix

    #49909 Reply
    emreigrek
    Guest

    i never forget you pix. God bless you 🙂

    #49910 Reply
    RK
    Guest

    The recommendation in general is 10x wavelength to 20x wavelngth. Of course, the higher separation the better since you’re able to de-couple the signals on both RX branches better. In GSM 1800 and PCS 1900 we’ve used 3 meter separation in deployments. But these days dual pol antenna is the answer for diversity.

    RK

    #49911 Reply
    Pix
    Guest

    Hello RK,

    when you say dual polar, you mean dualband cross-polar antennas ?

    Do you use this crosspolars in rural areas as well ?

    #49912 Reply
    RK
    Guest

    Dual Pol = Cross polar antenna. BTW, quad pol antennas are also available in the market these days. I am talking here about mature markets like Europe and North America. In some cases (even if it is rural environment) more antennas sticking out of the buildingds are not preferred due to aesthetics. So dual pol antennas rule. But yes, these are about 1 dB inferior due to lower signal de-correlation achievable.

    RK

    #49913 Reply
    Pix
    Guest

    RK, thanks for the input 🙂

    I never heard about the quad pol, it’s not in the catalog of the main antenna vendors..

    i’m very curious, does it have 4 different polarizations ? (0°, 45°, 90°, 135° ?)

    #49914 Reply
    RK
    Guest

    That is correct Pix, it is 0°, 45°, 90°, 135°. Not really sure what the applications are in 2G and 3G network- maybe applicable for 4-way diversity (?) that many vendors these days offer. I am almost sure Andrew has these antennas.

    Also, I think these antennas could be used in 4G technologies like WiMAX for 4×2 MIMO where TX at the Base station transmits on 4 parallel paths. Its also true that 4G will extensively use “smart antennas” which is an add-on smart functionality over X-pol antennas.

    RK

    #49915 Reply
    Pix
    Guest

    Hello RK,

    I cannot find these antennas in Andrews catalog, Kathrein catalog or RFS catalog… what I can find is dual-dual polar antennas (called also “quad” antennas in Andrews), which are actually two dual polar antennas, side by side, within the same radome.

    These two antennas have the same polarization and the same frequency band. I guess they provide two crosspolar with a little bit of space diversity… so it can be used for 4RX/2TX DIV. But IMO i’d use that to avoid combining 4 TRX onto one Xpol antenna. I could transmit 2 TRX on one antenna, and 2 TRX on the other antenna, that avoid a loss of 3 to 4 dB.

    What do you think ?

    pix

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