Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Forums Magazine Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Anritsu Alliance Test Equipment Amplifier Solutions Anatech Electronics Axiom Test Equipment Berkeley Nucleonics Bittele Centric RF Conduct RF Copper Mountain Technologies Empower RF everything RF Exodus Advanced Communications Innovative Power Products ISOTEC KR Filters Lotus Systems PCB Directory Rigol RF Superstore San Francisco Circuits Reactel RFCT TotalTemp Technologies Triad RF Systems Windfreak Technologies Withwave LadyBug Technologies Wireless Telecom Group Sponsorship Rates RF Cafe Software Resources Vintage Magazines Thank you for visiting RF Cafe!
Exodus Advanced Communications Best in Class RF Amplifier SSPAs - RF Cafe

Antenna parameters - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2010 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts.

NOTICE: The original RF Cafe Forum is available again for reading, and the new RF Cafe Blog is an active board.

-- Amateur Radio

-- Anecdotes, Gripes, & Humor

-- Antennas

-- CAE, CAD, & Software

-- Circuits & Components

-- Employment & Interviews

-- Miscellany

-- Swap Shop

-- Systems

-- Test & Measurement

-- Webmaster

 Post subject: Antenna parameters
Posted: Sat Jul 11, 2009 7:12 pm 

Joined: Sat Jul 11, 2009 6:57 pm

Posts: 1

Hi I am new to satellite field, could any body help me to explain in simple terms what is

a. polarization

b. cross polarization discrimination

c. cross polarization isolation

S Larsen

 Post subject: Re: Antenna parameters
Posted: Mon Jul 13, 2009 4:03 am 
User avatar

Joined: Fri Feb 17, 2006 12:07 pm

Posts: 236

Location: London UK

Hi Sandra

I don't have a classical textbook with me, but without here goes:

a) Polarization: every real antenna establishes E and H vectors around it when the energy in the feeder reaches the antenna structure. Conventionally, we think of the E field, because the H field is directly related to it, but 90 degrrees apart in space. Due to the way the current flows on the surface of the conductive elements making up the antenna, most of the E field will be oriented in one vector direction relative to a fixed set of orthogonal co-ordinates, on earth taken to be the horizon. If the direction is parallel to the earth's horizon, conventionally we define this as horizontal polarization, and of course if vertical to the horizon, vertical polarization. If current can be pursuaded by design of the structure to follow a particular curved path, then circular polarization results, and this is right hand or left hand depending on which sense the curved path follows.

b) and c) In the desciption above, I deliberately said "most of the E field", because the flow of current will establish E field in both the hozizontal plane and the vertical plane simultaneously. The ratio of these two vector magnitudes in dB is the cross-polarization level. In a circular polarized antenna with perfect circularity, this will be zero dB, because the E field level that can be measured is the same in the horizontal as well as the vertical plane. If you imagine a fat dipole, however, with the elements horizontal, most of the E field vector will be horizontal. However, some current will flow across the cylinder, around the curved direction, and thus it will set up a vertical E field. Let us assume this level is -15dB compared to the horizontal level. If an ideal horizontally polarized antenna were to be used as a far field source, with no vertical polarization, the level of energy received in the fat dipole is taken as 0dB when they are both in the same plane. If now the perfect antenna is rotated to the vertical, the level received should fall to zero, but will actually fall to -15dB. This is the cross polar discrimination. In my book, it is also the cross-polar isolation, but purists might disagree and argue the point.

Essentially, cross polar discrimination shows the ability of an antenna to separate, in the above example by rotating it, or discriminate, the pure vertical from the pure horizontal polarization of a received signal.


At bottom, life is all about

Sucking in and blowing out.

Posted  11/12/2012

Innovative Power Products Passive RF Products - RF Cafe
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe
Windfreak Technologies Frequency Synthesizers - RF Cafe
Amplifier Solutions Corporation (ASC) - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free


About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


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 World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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: