Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

[SOLVED] How to calculate the IM3?

Status
Not open for further replies.
tony_lth

tony_lth

Advanced Member level 5
Joined
Jul 28, 2010
Messages
2,088
Helped
377
Reputation
756
Reaction score
368
Trophy points
1,363
Location
Beijing
Activity points
12,641
1. Suppose PA OIP3=+40dBm
2. At PA output port, one CW is +26dBm.
3. At PA output port, another CW is +14dBm.
4. How to calculate the IM3 of the two CWs at the PA output?

Thank you very much.
 

The following equations can be used if you are in the small signal region of your amplifier. Note though that once you get close to the P1dB, these relations are not valid and you'll need a more complicated model or actual test data to get IM3.

at 2*f.1 - f.2
IM3 = 2*P.1 + P.2 - 2*IIP3

at 2*f.2 - f.1
IM3 = 2*P.2 + P.1 - 2*IIP3
 
There are some assumptions to define OIP3.Namely, OIP3 is an "extrapolation point" so that amplifier will never reach to this output power.
-Two carriers will have same amplitude that is at least 10dB below P1dB
-Carriers are as close as possible to observe IM3 products

OIP3=Single Carrier Level+Delta/2
Delta=Single Carrier Level-IM3 Level which is greater

So you can do the math to find IM3 level

But I warn you again... This equation is valid only with the assumptions that we have done...
 
If you already know the OIP3 and use unequal input levels the equation for IM3 @ (2*f1-f2) is:

IM3 @ (2*f1-f2) [dBm] = P1[dBm] – 2*[OIP3[dBm] – P2[dBm]]

As was stated, your amplifier have to be way below compression.
 
Hi, pstuckey and Bigboss and vfone,
Thank you very much.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top