Anatech Electronics (RF Filters) - RF Cafe
Exodus Advanced Communications Best in Class RF Amplifier SSPAs

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

PLL's an more important Low pass folter - 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: PLL's an more important Low pass folter Posted: Thu Aug 09, 2007 2:27 am


Joined: Wed Sep 15, 2004 3:15 am
Posts: 4
Location: Huntington beach
Well first i would like to know if anyone knows any online places that have goos info on pll's? searching i only came up woth some very basic stuff like wkipedia.
But my main question is on the after the phase comparator the lpf (can this be a band pass?) and how exactly does it effect settleing time. I would think a narrower bandiwidth will lock loop faster since it would pass less noise. And i thought that the filters job was just to pass dc because thats what input to the varactor on the vco?

Sorry for the "newb" question but i actually never seen a pll circuit, we use it internal to the chip so i cant probe around.


Post subject: Posted: Thu Aug 09, 2007 5:39 am


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
That site provides design guides and design routines for Mathcad
Hope it helps.


Post subject: Posted: Thu Aug 09, 2007 10:36 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
The only filter possible in PLL is a LPF. The purpose of the LPF is to smooth the output of the FPD (Frequency Phase Detector) and it sets the speed of the loop.

A wide filter will cause the loop to react faster, since the filter's pole(s) is/are located far, therefore, the filter has a wider reponse. The tradeoff, as you mentioned, will be a degradation in phase noise and vice versa.


Post subject: Posted: Thu Aug 16, 2007 4:33 pm


Joined: Wed Sep 15, 2004 3:15 am
Posts: 4
Location: Huntington beach
Thanks. i had not had the chance to thank you guys been doing alot of reading.
I do understand pll better but not enough yet.

Posted  11/12/2012
RF Superstore (RF Components) - RF Cafe
ConductRF Precision RF VNA Test Cables - RF Cafe

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

These Are Available for Free