Windfreak Technologies
Windfreak Technologies

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:

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

Microstrip impedance vs. frequency - 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

Post subject: Microstrip impedance vs. frequency Posted: Sun Sep 25, 2005 10:14 pm
two questions: 1) as the frequency increases what happens to microstrip characteristic impedance assuming dispersion affects are included?

2) i think at high freq., impedance will compensate for it do i make width bigger or smaller? my understanding is that you have to increase the width to get higher impedance. answers will be much appreciated. thanx



Post subject: microstripPosted: Wed Sep 28, 2005 5:50 pm
I'm at work right now & don't have access to the papers - but Rogers Corp. has an on-line calculator (downloadable too) and the formulas it's based on in this pdf:

Good Luck!


Post subject: Posted: Wed Sep 28, 2005 7:05 pm
A microstrip transmission line will tend to
"roll off" as frequency increases.
This is because the shunt capacitance becomes

A 50 ohm line is a 50 ohm line regardless of frequency.


Post subject: microstripPosted: Thu Sep 29, 2005 2:26 pm
anormalhouse said: "A 50 ohm line is a 50 ohm line regardless of frequency".

Not true. Most substrate materials have a dielectric constant which is a function of frequency. Since the dielectric constant is part of the impedance formulas, the characteristic impedance varies with frequency.

FR4 is a particularly blatantly bad example of this. "50 Ohm lines" on FR-4 vary from 50 Ohms as the frequency goes above 1 GHz. This is in the literature. Again, see the Rogers website.

Good Luck!


Post subject: Posted: Thu Sep 29, 2005 2:40 pm
Yeah, you kinda missed my point.


Post subject: Posted: Thu Sep 29, 2005 4:26 pm

you guys really didn't answer the question and i'd like someone to answer it again for me also and for the person who orginally asked the question. taking into account frequency effects what will happen to impedance when the width is increased?


Post subject: Posted: Thu Sep 29, 2005 4:37 pm
whoa, whoa, calm down "guest". We'll aswer the questions in due time.

Let me have a cup of coffee first, then we can all about frequency vs. line width, dielectric constants, and dogs.


Post subject: Posted: Fri Sep 30, 2005 6:46 am
When you increase the width the impedance goes down, mor capacitive. Decreasing the width the impedance goes up, more inductive.

Posted  11/12/2012
TotalTemp Technologies (Thermal Platforms) - RF Cafe
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe

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

These Are Available for Free