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 Stencils for Visio RF & EE Shapes for Word Advertising RF Cafe Homepage Thank you for visiting RF Cafe!
everythingRF RF & Microwave Parts Database (h2) - RF Cafe

urgent, LPF to suppress the hamonics - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

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

nassim1
 Post subject: urgent, LPF to suppress the hamonics
Posted: Thu Apr 16, 2009 8:02 am 
 
Lieutenant

Joined: Thu Apr 16, 2009 7:45 am
Posts: 2
Dear all,

I want to filter the all harmonics above 125MHz using Low pass filter (BW : 300MHz, specification) but I could not suppress them even I used a good response LPF . Note that, this harmonics are from mixing an RF signal and an LO signal.

Is an idea about it ??

Thnak you in advance

N


 
   
 
nubbage
 Post subject: Re: urgent, LPF to suppress the hamonics
Posted: Mon Apr 27, 2009 7:35 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 343
Location: London UK
Hi nassim
You will not be able to filter the second harmonic of 125MHz if the -3dB bandwidth of the LPF is 300MHz.
If your max frequency is 125MHz, then the -3dB cutoff frequency should be no higher than say 140MHz, in order to ensure that at the second harmonic (250MHz) the level is well attenuated. There may be other products generated by the mixer, depending on your system topology. Thus you should ensure that the expected products in all conditions are above the low frequency -3dB cut-off frequency. What are all the frequencies present at the mixer ports?

_________________
At bottom, life is all about
Sucking in and blowing out.





Posted  11/12/2012
Triad RF Systems MPDevice microwave devices - RF Cafe
Res-Net Microwave - RF Cafe Berkeley Nucleonics Academy - RF Cafe
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 typing 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

spacer

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

These Are Available for Free