You can try to dielectically load the patch. You can add a dielectic over the patch or select a different substrate.
Check out Roger Corp.(http://www.rogerscorporation.com/acm/index.htm)
You can also dielectrically load the gap of the slot antenna.
You may not need a balun, but you may still need a transformer (or isolator)to get a better match. It depends on the S11 you can live with. You need to determine the RF link requirements and concider how much reflected power the Tx can handle. As a guide a 2:1 VSWR (-9.6 dB return loss) means...
In addition to VE1BLL, you will need to account for the ground effects (mutltipath reflections, terrain obstructions) as well as fade margin. Most manufacturers have a recommended fade margins for their receivers.
Look at:
http://www.proxim.com/support/all/stratum/technotes/tn2001-08-13a.html...
I agree with BrianR, more details are needed.
I used to work with EMS. They manufacture BFN's.
http://www.emsstg.com/space_sol/beam_forming_networks.asp
Also checkout:
http://scholar.lib.vt.edu/theses/available/etd-04262000-15330030/unrestricted/ch3.pdf
Also, BFN's can be relatively simple or...
Depending on the ground plane size check out the Numerical Electromagnetic Code (NEC) programs:
http://www.emclab.umr.edu/cemlinks.html
http://www.nittany-scientific.com/ (I have used their software 6 years ago, worked well)
Also, Ball Areospace & Malibu Research are companies that produce microstrip array antennas:
http://www.ball.com/aerospace/
http://www.maliburesearch.com/advancedAnt00.html
Other related links:
http://ndl.ee.ucr.edu/Myslide.pdf
http://www.argospress.com/Resources/antennas/books-antennarra.htm...
To add to what VE1BLL stated here are some links for atomspheric attenuation effects, which can alter the free space attenuation. Also rain can effect some frequecies
Checkout:
http://www.rfcafe.com/references/electrical/atm_absorption.htm
http://web.haystack.mit.edu/haystack/files/AtmAtt.pdf...
Contact Rogers corp (http://www.rogers-corp.com/). They have some ceramic loaded dielectric materials. Not sure if they have what you need , but they have some "composite" dielectrics. Theu may also have a recommendation.
See:
http://www.rogers-corp.com/mwu/translations/prod.htm
Try:
http://www.geocities.com/SunsetStrip/Underground/8585/loop.html
http://www.microchip.com/connectivity/rfPICDEM1/files/uwrfa1p6.pdf
For books try:
"Antennas" by John D. Kraus or for a less mathmatical book try: "Antenna Engineering Handbook" by Jasik
Search...
You might try contacting companies like www.adtran.com or www.lgcwireless.com and talk to an applications engineer.
You may try researching regular radio repeater articles i.e @ Daniels Electronics (http://www.danielselectronics.com/AnalogApplications.htm).
You may try researching some of the...
What is the goal of the reduced efficiency? Are you just trying to limit the range of the system? If so another method of "detunning" or reducing an antenna's overall gain is by using resistive paints or lossy dielectric material(i.e. absorber material). Some of these materilas can...
If you haven't found the frequency yet you may try searching the FCC number (usally printed near the model and serial number) try the following sites:
http://www.fcc.gov/oet/fccid/help.html
https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/GenericSearch.cfm
http://www.driverzone.com/fcc_reg.htm
You need the antenna factor for the antenna being used in the measurement. For calibrated antennas visit:
http://www.ara-inc.com/bbh.htm
http://www.com-power.com/Antennas.htm
For info on antenna factor visit:
http://www.conformity.com/A03F38.pdf
http://www.microindustrie.com/fcc/recaf.htm
In your original message you asked to predict propagation. If you don't have simulation software you can make a measurement by using watermellons or cantalope to simulate the cow (no joke). If you don't have access to an antenna range you can use a spectrum analyzer to make a path measurement...
The reflected power that the PA can handle dedpends on the PA design. Most PA's should be desinged to handle a short (or open) at the antenna port. If you were to use an isolator, than the reflected power is "absorbed" into the load in the isloator and the PA is protected. Typically...
This is an age old issue with antenna engineers. If you ask 7 antenna engineers you get 4 different answers. This can be a very complex issue depending on the platform. If one looks at the equation for gain you'll find it contains a term for the antenna apperature. This aperature term can be...
Review EMI standards and test proceedures. While you may not need to meet MIL-STD's, they may be a good reference.
MIL-STD-461 and MIL-STD-462
(There are commerical equivalent standards, I can't remember them right now)
Research the tests labled CE (conducted emmisions)& RE (radiated...
Check out "Antenna Enginerring Handbook" by Henry Jasik first edtion chapter 18, section 3 (pages 18-10 thru 18-32)for some insight.
Note: See page 14-3 in the second edtion version of the same book :"Antenna Enginerring Handbook" by Richard Johnson & Henry Jasik.
I use Comstudy from Radiosoft. I use it for radio coverage for mountain top repeaters/base stations. I do agree with VE1BLL that sometimes it's easer to try it than model it. Some of the software vendors offer free demo versions (with limitations). Comstudy does give you the ability to add...
Did you mean Discrimination ratio? Like in signal to noise ratio? If so, are you asking what happens when your waveform fades or gets weaker and your received signal to noise ratio gets worse (ie 3dB vs 12 dB)?
