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!
Axiom Test Equipment - RF Cafe

Some distributed systems questions ... - 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

taz

Post subject: Some distributed systems questions ...

Unread postPosted: Thu Oct 07, 2004 12:12 pm

Offline

Lieutenant

Joined: Thu Oct 07, 2004 11:52 am

Posts: 2

hi,

I have two basic but important questions, I hope you can help me:

1. Why do we use distributed model (and not lumped) in frequency applications\problems ??? what are the advantages\disadvantages ?

2. Why there are incident waves and reflected waves in a transition line ? this happen for both sinusoidal and step function….why ???

Thanks,

taz

Top

Profile

Itay

Post subject:

Unread postPosted: Thu Oct 07, 2004 12:36 pm

Greetings,

No clue for your first question. If you will be more specific I might give you an answer. Basically, distributed elements can be modeled as lumped elements for the the purpose of analysis; for example, this is the way to derive the telegraphic equations of a transmission line.

For your second question: Incident waves are voltage waves that flows from a source eg: Generator to a load. In an ideal circuit all the energy of these waves is being absorbed in the load. In the practical world, a portion of this energy is reflected back due to impedance mismatch. The impedance of the load should be equal to the characteristic impedance of the system eg Zo, which is usually 50 ohm in RF systems, 75 ohm in Video applications and 600 ohm in Audio applications. The amout of the mismatch determines the size of the reflected waves. The reflection coefficient determines the size of the reflections. It is defined as: rho=(ZL-Z0)/(ZL+Z0). From here you can also derive the return loss, which is the amount of the reflected wave in relation to the incident wave: RL=-20 log |rho|. That means how lower is the reflected wave comparing to the incident one (It should be as low as possible of course)

Hope this helps,

Itay

Top

taz

Post subject:

Unread postPosted: Thu Oct 07, 2004 1:02 pm

Offline

Lieutenant

Joined: Thu Oct 07, 2004 11:52 am

Posts: 2

Hi Itay, thanks for your answer !

I will start with your second answer, I agree with what you said 100%, and for the present time I accept it as an axiom. This is why I'm asking these questions …why mismatch is causing reflected waves ? why In the practical world, a portion of this energy is reflected back ??? why match circuits don't have reflected waves ???

I understand the math, but I don't understand the physics behind it ….

And for my first question, for my best understanding …these are two different theories , but according to what you said – they are derived from another . is that a correct interpretation ???

by the way, why in speakers wiring there's no indication for impedance ??

again…thanks,

taz

Top

Profile

Itay

Post subject:

Unread postPosted: Thu Oct 07, 2004 1:42 pm

Greetings Taz,

You are welcome.

Yes the theory of transmission lines is derived from an analysis of lumped model which defines the transmission line as LPF circuit that includes L,G,R,C elements and also their values per unit length. From this theory you also derive the Zo and Gamma coeffiencient: Zo= sqrt (L/C) - In loseless tranmission lines and Zo= sqrt ((R+jwL)/(G+JwC)) in lossy transmission lines and many more definitions...

I advise you to read more in text books regarding your questions and find better answers. Posting questions like these in a forum won't bring the answers you would expect, as there are many lines to write about it and people aren't that patient to write them...

Regarding your question about speakers, please read the following:

http://www.duncanamps.com/technical/dummyload.html

Speakers have a varying load impedance and there is no meaning for the impedance of the wiring.

I hope this helps,

Itay

Posted  11/12/2012

Copper Mountain Technologies (VNA) - RF Cafe
RF Superstore (RF Components) - RF Cafe
Anatech Electronics (RF Filters) - RF Cafe
TotalTemp Technologies (Thermal Platforms) - 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

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