Visit RFCafe.com Thanks for visiting RFCafe.net Thanks for visiting the RF Cafe Archives Thank you for visiting RF Cafe Thank you for visiting the RF Cafe Archives!

term antenna - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

lee85
 Post subject: term antenna
Posted: Tue Feb 03, 2009 10:04 pm 
 
Captain
User avatar

Joined: Fri Dec 14, 2007 11:23 am
Posts: 9
Location: malaysia
hello all,

i am new with design antenna, can anyone tell me what is isolation and diversity?
only that i understand isolation mean that interaction between an antenna and its surrounding
i am confuse what correlation between isolation and diversity if we have 2 antenna in one device?
thanks.

rgds,
lee85


 
   
 
nubbage
 Post subject: Re: term antenna
Posted: Wed Feb 04, 2009 4:41 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 236
Location: London UK
Hi lee85
I suppose isolation is the reciprocal of coupling but I have not seen it mentioned as an antenna parameter. Coupling has 2 meanings: there is coupling between adjacent elements in an array which is either desired because it enhances either sidelobe levels or gain, and unwanted coupling that degrades performance or complicates the design process.
So far as isolation is concerned, there is a parameter called cross-polar isolation, which is the degree to which two antennas with nominally opposite polarisation still cross-couple due to imperfection. Thus if an antenna is nominally vertically polarised but with a small say -15dB of horizontal vector, then the isolation to an antenna that is hrizontally polarised will be -15dB.
Diversity takes several forms and is normally encountered when a path between antennas has a time-varying refractive index and a possibility of two or more paths: one direct and the others by reflection. Spacing two receive antennas maximises the probability that the paths to one of them will result in a vector sum that is a maximum, whilst at the other antenna the received signal has a vector sum that is a minimum, ie has faded due to out of phase vector addition. The antennas can be spaced apart vertically or horizontally (space diversity), or the polarisation can be opposite (polarisation diversity), or two different frequencies can be used (frequency diversity). The ITU-R publish recommendations how these can be implemented.

_________________
At bottom, life is all about
Sucking in and blowing out.




Posted  11/12/2012
RF Stencils for Visio v3.1 by RF Cafe
RF Cascade Workbook 2018 (GS) - RF Cafe
About RF Cafe Archives
Kirt Blattenberger - RF Cafe Webmaster
Copyright: 1996 - 2024
Webmaster:
    Kirt Blattenberger,
    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:  AirplanesAndRockets.com

spacer