RIGOL Technologies (test equipment) - RF Cafe
RF Electronics Symbols, Stencils for Office, Visio by RF Cafe
 

About RF Cafe

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 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:

AirplanesAndRockets.com

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 App Notes Calculators Education Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Homepage Thank you for visiting RF Cafe!
Anatech Electronics

How to design a matching network (given VSWR) - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2012 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. If the folks at phpBB would release a version with integrated sign-in from the major social media platforms, I would resurrect the RF Cafe Forums, but until then it is probably not worth the effort. 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.

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

meade58
Post subject: How to design a matching network (given VSWR)
Unread postPosted: Wed Apr 27, 2005 12:05 pm
Offline
Lieutenant

Joined: Wed Apr 27, 2005 11:51 am
Posts: 1
Can anyone explain how to design a matching network given the VSWR of a device?
Given:
an RF power amp module "optimized for 50 Ohm system".
the data sheet says the the module incorporates matching networks optimized for output power and linearity in a 50 Ohm system.
the only spec that the manufacturer lists is input impedance VSWR of 2:1

a duplexer with VSWR of 1.4 on the TX side
frequency range: 1920 - 1980 MHz

Is this solved by use of the Smith chart? As you can tell, I am a newbie to RF

Thanks,
Rich


Top
Profile

Guest
Post subject:
Unread postPosted: Wed Apr 27, 2005 1:30 pm

Hello,

You have to measure the output impedance of your module, Once you have this information, you can design your matching network. The output impedance of your module will be the starting point on the Smith chart from which you have to "move" towards 50 ohm load (the prime-center).

To measure the output impedance: Terminate the input of the device with 50-ohm, bias it and measure the output impedance (S22) with Network Analyzer


Top


Guest
Post subject:
Unread postPosted: Wed Apr 27, 2005 5:50 pm

WRONG!


Top


Jeanalmira
Post subject:
Unread postPosted: Wed Apr 27, 2005 9:49 pm
Offline
General
User avatar

Joined: Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi,

Regarding your questions on designing matching network of a given input VSWR.

Basically VSWR represents impedance and return losses, which the best value is 1:1.

I think what you can do is, measure the RF PA small signal by VNA, and plot in Smith Chart for S11 and S22. at this point you can see whether VSWRin is 2:1.

To design input matching networks, you have to move the curve to the nearest point of 50 Ohm (center) by adding either low-pass or high-pass configurations.
It depends which directions it should be moved.

For details, maybe you could check out this textbook:

G.Gonzales," Microwave Transistor Amplifiers, Analysis & design," 2nd Ed, Prentice Hall,1997


However I am not sure what kind of matching networks you need to design, is it input or output matching networks?



Regards,
Jean


Top
Profile

Guest
Post subject:
Unread postPosted: Thu Apr 28, 2005 9:04 am

Are you making a power match or a gain match? This is not the same.


Top


Guest
Post subject:
Unread postPosted: Thu Apr 28, 2005 9:12 am

Additionally

If you see that the manufacturer is claiming the device to be already optimaly matched and that you have a bad VSWR from measurement, then it is a power match. You will not improve things by trying to conjugate match the module. You will in fact decrease its power output capacity.

You have to choose, gain or power?


Top


Guest
Post subject:
Unread postPosted: Thu Apr 28, 2005 9:14 am

Gee...

Were talking about input match... Sorry disregard my comment about output power match.



Posted  11/12/2012
Copper Mountain Technologies - RF Cafe
withwave microwave devices - RF Cafe
 

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

These Are Available for Free