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How does link budget imrpoves for antenna arrays - RF Cafe Forums
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| Michael
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Post subject: How does link budget imrpoves for antenna arrays
Posted: Thu Apr 23, 2009 9:38 am
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Joined: Thu Apr 23, 2009
9:17 am
Posts: 4 |
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I have
N antenna elements Tx array
communicating
with
M antenna elements Rx array.
By
how much will the link improve ?
by 20LogN +
10LogM or by 20LogN + 20LogM ?
Why?
(Compared
to same link with just single identical antenna
and same power, NF, distance etc)
Thanks
Michael
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Loren A. |
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Post subject: Re: How does link budget imrpoves for antenna arrays
Posted: Tue Apr 28, 2009 1:46 pm
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| Captain |
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Joined: Fri Jul 16, 2004
4:12 pm
Posts: 11 |
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Hi Michael
The answer isn't a simple one
since it depends on the configuration of the antennas
on both ends, and what your objective is. Theoretically,
a system like 802.11n that uses three antennas,
depends on orthogonality to realize maximum efficiency.
In an ideal environment (no reflections, equal path
lengths, equal antenna performance, equal TX/RX
circuitry) the three orthogonal antennas independently
transmit/receive energy from the same signal in
all three planes, without any interaction. The receive
system would add the signals.
In the real
world you know that the antenna configurations have
to be adjusted for best average performance in the
operational environment. Same goes for two antennas
or even one antenna.
For any system of antennas,
the net performance depends on spacing between antennas
and how the receiver handles the signals. Again,
for and ideal scenario where all antennas are far
apart enough to be considered independent and all
signals arrive at the same phase (or can be adjusted
for addition), the total received power is the sum,
in watts (not dB), of the individual signals.
To get a meaningful feel for how your intended
configuration will perform, a computer simulation
will be needed.
Have fun.
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Michael |
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Post subject: Re: How does link budget imrpoves for antenna arrays
Posted: Fri May 01, 2009 12:23 pm
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Joined: Thu Apr 23, 2009
9:17 am
Posts: 4 |
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And what would be the answer if make assumptions
that will make it easiest to answer:
-Line
of sight between Tx and Rx.
-No reflections
-The single transmitter is identical to each of
the N transmitters.
-The single receiver is identical
to the each of the M receivers.
-The direction
for the single antenna maxGain is the direction
of the array maxGain
-The question is asked regarding
that max gain direction
What is igain link
mprovement compared to single antenna link?
10LogN +10LogM ?
20LogN +10LogM ?
20LogN
+20LogM ?
Why?
Thanks
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Posted 11/12/2012
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