Anatech Electronics (RF Filters) - RF Cafe
LadyBug Technologies LB479A RF Power Sensor - RF Cafe

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

ADS Momentum Simulation problem - 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: ADS Momentum Simulation problem
Posted: Sun Oct 09, 2005 10:43 pm 
i'm having a big problem in displaying the gamma and impedance values of a transmisison line. i've a simple microstrip and i attached a substrate definition and ran the simulation. it worked fine and i got the s-parameters but when i do Momentum-->Post Processing -->Visualization to see the gamma and impedance graphs versus frequency, i get impedance being 50 ohm throughout the frequency range and gamma being zero throughout.

The s-params make sense but for some reason i'm not getting the right transmission line data. does any one know what's going on? i read the momentum manual and it said that if it didn't recognize the ports as 'Single' it sets the gamma=0 and impedance=50. So, i'm assuming that might be the case but how do I fix that. My ports are single with 50 ohms. I did Momentum--> Port Editor... I also read in the manual that if you define a 'Single' port your 'substrate definition must include at least one infinite metal layer: a top cover, ground plane, or a slot layer, or a ground reference must be used in addition to the port'. Now, I've a ground plane because i'm simulating a microstrip and i've mapped the ground plane as a slot layer. so, i think i'm meeting the requirement but i'm still unable to see the right gamma and impedance.

Any help will be much appreciated.

 Post subject: Re: ADS Momentum Simulation problem
Posted: Sun Oct 23, 2005 12:32 am 
Hi, What you see is the impedance which is connected to the port , which
is usually assumed to be 50 ohm. If you want the input impedance and vswr they automatically does not appear on the list. You need to calculate them through eqn. option of ads. i.e. zin=(1+s11)/(1-s11)*z0

 Post subject: Re: ADS Momentum Simulation problem
Posted: Thu Feb 25, 2010 2:44 pm 

Joined: Tue Dec 15, 2009 10:22 am
Posts: 1
Is that a general expression, or is it assuming a terminated network?

Posted  11/12/2012
high frequency PCB of PCBONLINE
Werbel Microwave - 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