What is the impact of antenna array on link budget  RF Cafe Forums

Michael

Post subject: What is the impact of antenna array on link budget
Posted: Thu Apr 23, 2009 9:35 am


Joined: Thu Apr 23, 2009
9:17 am Posts: 2 
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





nubbage 
Post subject: Re: What is the impact of antenna array on link budget
Posted: Mon Apr 27, 2009 7:49 am



General 

Joined: Fri Feb 17, 2006
12:07 pm Posts: 236 Location: London UK

My vote is 10*LOG(M+N) plus a fudgefactor, and
assuming the antennas are still in the Far Field
region.
_________________ At bottom, life is all
about Sucking in and blowing out.





Michael 
Post subject: Re: What is the impact of antenna array on link budget
Posted: Wed Apr 29, 2009 4:16 pm


Joined: Thu Apr 23, 2009
9:17 am Posts: 2 
Thank you nubbage, Could you reconsider please (I
think differently at least on Tx  why do you thin
I am wrong? )
Given the assumption of the
original single antenna link has the same parameters
to the NTx/ MRx case  same output power per antenna,
NF per antenna, etc + no reflections, line of sight,
ideal spatial summing at the max gain direction,
array max gain direction same as the single antenna
max gain direction, and any other assumption that
minimizes the problem to the simple one.
For the Tx antenna side, for sure fields of the
N antenna sum perfectly. So if at point P in the
single antenna case field was for example E it will
become now N*E. (The E vectors are all in the same
size and direction according to the assumptions
above). Therefore the transmitted power which
is proportional to E^2 willl follow the 20*LogN
at point P. So, the antenna gain in the link
budget will increase by 20*LogN compared to the
N=1 case. i.e. at point P
What happens
on the Rx side?


Posted 11/12/2012


