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# OIP3-estimatedP1dB - RF Cafe Forums

 The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Below are all of the old forum threads, including all the responses to the original posts. -- Amateur Radio -- Antennas-- Circuits & Components-- Systems-- Test & Measurement

Jeanalmira
Post subject: OIP3-estimatedP1dB
Unread postPosted: Wed May 04, 2005 9:45 pm
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Joined: Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi all:

I have questions regarding OIP3 and estimated P1dB.
Currently, I calculate estimated P1dB from DC power, with 50% drain effciency.

Then OIP3 (dBm) was calculated from IM3 (dBc) based on the SCL output power. After that, I take a look at OIP3-estimated P1dB. I understand that the larger the difference shown the better performance.

But at this moment I am not sure, why is it so? what are the theoretical/practical reasons behind?

Thank you in advance for clearing my doubts.

Regards,
Jean

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Unread postPosted: Thu May 05, 2005 2:52 am

Hi Jean,

A well-known rull of thumb: OIP3 is 10dB higher than P1dB.

As you know, The OIP3 is a theoretical point that is obtained by linear extrapolation of the tangents for both the fundamental and third order curves, until they meet at a certain output power point - OIP3. The higher the difference between these 2 points the linear is the amplifier. That means you will obtain lower IM3 products for a given output power.

Usually, the OIP3 is measured at the linear region of the device.

If you have a bigger difference between P1dB and OIP3 that means for a higher power (higher than which OIP3 is measured) you will obtain lower IM3 products compared to an amplifier with that has a lower difference between these parameters.

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Jeanalmira
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Unread postPosted: Thu May 05, 2005 8:36 pm
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Joined: Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi!

Thank you so much for the advice.
Truly appreciated :D

Regards,
Jean :wink:

Posted  11/12/2012