Electronics World Cover,TOC,and list of posted Popular Electronics articles QST Radio & TV News Radio-Craft Radio-Electronics Short Wave Craft Wireless World About RF Cafe RF Cafe Homepage RF Cafe in Morse Code Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs Twitter LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes AN/MPN-14 Radar 5CCG Notable Quotes App Notes Calculators Education Magazines Software,T-Shirts,Coffee Mugs Articles - submitted by RF Cafe visitors Simulators Technical Writings RF Cafe Archives Test Notes Wireless System Designer RF Stencils for Visio Shapes for Word Search RF Cafe Sitemap Advertising Facebook RF Cafe Forums Thank you for visiting RF Cafe!

PAR vs. EVM - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


lna
 Post subject: PAR vs. EVM
Posted: Fri Feb 19, 2010 4:35 pm 
 
Captain

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

I'm designing a 1W OFDM power amplifier for 500~700MHz. The signal PAR is about 12.5dB and ESG reading is about the same, which means the PA P1dB should be better than (30+12.5) = 42.5dBm. In my design P1dB rolls off to 38.5dBmat each end, which is 4dB compressed, however EVM measurement is better than -39dB.

Can someone help me understand this? Could a compressed PA provide doog EVM?


 
   
 
IR
 Post subject: Re: PAR vs. EVM
Posted: Wed Feb 24, 2010 4:03 pm 
 
Site Admin
User avatar

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Usually the EVM can not be good if the P1dB is lower than the signal's PEP.

Maybe it has to do with the filter the signal has (Raised-Cosine etc), and other signal parameters like clipping which affect the CCDF. This can affect (improve or degrade) the EVM.

But this is just my guess...

_________________
Best regards,

- IR


 
   
 
RDO-RF
 Post subject: Re: PAR vs. EVM
Posted: Mon Mar 01, 2010 2:43 pm 
 
Captain
User avatar

Joined: Wed Apr 08, 2009 7:53 am
Posts: 12
The signal has 12.5dB of PAR, but that doesn't exactly means that your power amplifier should have the same back-off. Note that in the CCDF curve the 12.5dB peaks have very low probability. Remember that EVM is an average value and perhaps your can effort clipping the signal once a while having no grater effect on EVM.
For some signals, clipping affects first the ACPR and then the EVM. You can check this on your VSA, by looking if this good EVM output signal that you have has degradation on its ACPR.

This was my guess.

_________________
web: http://www.rdo-labs.com




Posted  11/12/2012

RF Cafe Software

   Wireless System Designer - RF Cafe
Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chartâ„¢ for Visio
Smith Chartâ„¢ for Excel

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2022
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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

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

Try Using SEARCH
to Find What You Need. 
There are 1,000s of Pages Indexed on RF Cafe !

height-line