RIGOL Technologies (test equipment) - RF Cafe
Exodus Advanced Communications Best in Class RF Amplifier SSPAs
 

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

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!
RF Cascade Workbook 2018 - RF Cafe

Better driver, worse system performance??? - 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

lna
 Post subject: Better driver, worse system performance???
Posted: Thu Jun 03, 2010 6:49 pm 
 
Captain

Joined: Mon May 04, 2009 6:47 pm
Posts: 22
--------------------------------------------------------------------------------

I'm looking for help for a PA design.

My project is a balanced 1W(average) OFDM PA at 600MHz, droven by a half watt class A driver. The original design is very close to system requirements, except marginal fail EVM, which I think caused by the driver. So I found a drop in replacement driver and evaluated it. With new match circuits, the new driver alone performancs very good--2dB higher P1dB and 1~2dB better EVM.

What confused me is that system EVM drop by 2~6dB!!

I don't think the driver change would impact the final stage because there is a 50ohm splitter between them.

Any idea???? Please.


 
   
 
IR
 Post subject: Re: Better driver, worse system performance???
Posted: Tue Jun 08, 2010 3:06 pm 
 
Site Admin
 

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
I think that the problem is not within the driver.
The new driver which you tested proves that point.

If the problem is linearity - which seems to be based on the description you showed, then the problem lies within the balanced amplifier.

The significant stage for cascaded IP3 calculation is the last stage of the Tx chain.

(Same as the first stage for cascaded NF calculation).

Try to focus on the balanced amplifier and optimize it.

In many data sheets of power transistors, there are measured results for different signals.

--> Have you looked on what are the expected performance of the transistor (within the balanced amplifier) for the type of signal you are using (i.e. modulation type, filter applied, clipping etc).

It might be the case that you need to consider a final stage with more output power.

_________________
Best regards,

- IR





Posted  11/12/2012
high frequency PCB of PCBONLINE
EMC Directory
Axiom Test Equipment - RF Cafe
 

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

These Are Available for Free