Custom Search
Over 9,000 pages indexed!
Your Host
Click here to read about RF CafeKirt
Blattenberger
... single-handedly
redefining what an
engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse riding business website - lots of info

Doggy Dynasty:
My son-in-law's dog training business
•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<
Job Board
About RF Cafe©
RF Cafe E-Mail
Product & Service
Directory		 Engineering
Jobs
Personally Selected
Manufacturers		 Employers Only
(no recruiters)
Connection between IP3 and P1dB... - RF Cafe Forums
Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


New System Designer
 Post subject: Connection between IP3 and P1dB...
Posted: Sun Sep 25, 2005 2:20 pm 
Hello everyone,

Help needed:

What is the connection between IP3 and 1dB compression point in RF Amplifiers ? as I understood, when I deal with Amp. with high IP3 (for example: +30dBm) there is a problem to measure it with spectrum analyzer...

And I don't know what's the answer ?

I assume that for seeing the IP3 spurious, I need to inject very high power signal which might compress the Amp.
but I can't figure other way for measure the IP3 power without injecting very high signal and compressing the Amp. ??!!


 
  
 
IR
 Post subject:
Posted: Mon Sep 26, 2005 8:13 am 
 
Site Admin
User avatar

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 413
Location: Germany
Hello,

There is no constant connection between IP3 and P1dB in amplifiers, and even the "rule of thumb" of: IP3=P1dB+10dB is not accurate and doesn't apply. These quantities are dependent by the technology and process of the amplifier. However, you can say that in amplifiers the IP3 is always higher than P1dB.

To measure the IP3 you need to inject 2 signals that are adjacent to each other, and measure the 3rd orfer products. The formula to measure the IP3 is:

OIP3=P1+IMR3/2

Where:

P1 - The output power of the fundamental signal
IMR3- The power difference between third order products to fundamental product [dBc].

The IEEE definition is that the IMR3 should be equal or higher than 20dBc: IMR3 >=20dBc

In linear operation, if you increase the input signals by 1dB, the third order products will increase by 3dB. You should do the IP3 measurement in small signal (That is being covered by the IEEE definition) to obtain an accurate result.

_________________
Best regards,

- IR


 
   
 
New System Designer
 Post subject:
Posted: Wed Sep 28, 2005 3:59 pm 
Thanx for the reply IR. Your frequent postings on this forum are a great help - I've read through many of them. Keep up the great work!!!!

:D :D :D


 
  
 
IR
 Post subject:
Posted: Thu Sep 29, 2005 2:12 pm 
 
Site Admin
User avatar

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 413
Location: Germany
You are welcome! :)

One more clarification:

Quote:
to measure the IP3 you need to inject 2 signals that are adjacent to each other


According to the IEEE the IP3 measurement is done under a narrwband condition, which is: ±5% of the center frequency. That gives you the range in which the adjacent signals can be located.

Good luck!

_________________
Best regards,

- IR




Posted  11/12/2012

RF Cafe Software

RF Cascade Workbook
 RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

Smith Chart™ for Excel
Smith Chart™ for Visio
RF & EE Symbols Word
RF Stencils for Visio
A Disruptive Web Presence™

Custom Search
Over 9,000 pages indexed!
 Read About RF Cafe
Webmaster: Kirt Blattenberger
KB3UON

Product & Service Directory
Personally Selected Manufacturers

 RF Cafe T-Shirts & Mugs
Calculator Workbook
RF Workbench
Please Support My Advertisers