Custom Search
Over 10000 Pages Indexed
Your Host
Click here to read about RF CafeKirt
Blattenberger

... single-
handedly
redefining
what an
engineering website
should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse
riding business website -
lots of info

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe©

RF Cafe E-Mail

Microstrip impedance vs. frequency - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

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


mike
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 decrease....to 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

-mike


Top

guest
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:

http://www.rogerscorporation.com/mwu/pdf/rt312.pdf

Good Luck!


Top

anormalhouse
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
dominant.

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


Top

Guest
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!


Top

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


Top

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

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?


Top

anormalhouse
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.


Top

Guest
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
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel