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Is it mandtory the difference between IIP3 and P1dB compression point

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narayani

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Is it mandtory the difference between IIP3 and P1dB compression point must be 10 dBm

I am using pHEMT transistor for design of my LNA. I have got 46 dBm as the IIP3 and P1 dB as 12 dBm.

I have heard that difference between IIP3 and P1 dB must be 10 dBm. Is it mandatory difference between P1 dB and IIP3 must be 10 dB or even difference crosses more than 10 dB as we were getting 34 dBm difference, is it correct or any thing wrong in measuring. We have measured P1 dB compression point with respect to output power.

Difference between P1 dB and IIP3 must be closer to 10 dBm, is it O.K. or if difference cross more than or less than 10 dBm, as such more than 20 dBm, 30 dBm , 35 dBm or as such less than 5 dBm, 8 dBm , 2 dBm, is it wrong.

Can you clarify
 

mtwieg

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The 10dB difference rule of thumb is normally between the input referred P1dB and input referred IP3, otherwise the difference would be dependent on the amplifier's gain. 34dB might be normal if your amp has a gain over 20dB.
 

vfone

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In my opinion 34dB difference between P1dB and IIP3 is unusual.
This could happen only if the bypass impedance of the bias circuit (at the frequency of F2-F1) is much higher than the input impedance of the LNA.
Bias decoupling of both, drain and gate, affect the difference in dB between P1dB and IIP3.
 

narayani

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34dB might be normal if your amp has a gain over 20dB.

My LNA has gain of 23 dB. Is 34 dBm of P1 dB compression point O.K.

What could be reasonable reason of P1 dB compression point, when gain of the LNA is greater than 23 dB.
 

mtwieg

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My LNA has gain of 23 dB. Is 34 dBm of P1 dB compression point O.K.
Didn't you say above you measured P1dB at 12dBm with respect to output power? If you're going to refer to both input and output, then use specific terms like P1dBin and P1dBout.

If P1dBin is 12dBm and IIP3 is 46dBm, then that's far too much of a gap. Are you sure you don't mean OIP3 is 46dBm? Could you show your plots?
 

BigBoss

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OIP3 ( dBm)-P1dB Output Compression Point(dBm)=9.6dB

IIP3=OIP3(dBm)-Gp(dB)

I guess you're confusing OIP3 and IIP3..
 

RCinFLA

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The difference depends on how soft or hard the onset of compression of the amp is.

34 db seems excessive. Your measurement of IP3 is probably the error. If you used spectrum analyzer in measurement you may have put too high a signal level into it. Try putting in some attenuation.
 

narayani

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Didn't you say above you measured P1dB at 12dBm with respect to output power? If you're going to refer to both input and output, then use specific terms like P1dBin and P1dBout.

If P1dBin is 12dBm and IIP3 is 46dBm, then that's far too much of a gap. Are you sure you don't mean OIP3 is 46dBm? Could you show your plots?

The difference depends on how soft or hard the onset of compression of the amp is.

34 db seems excessive. Your measurement of IP3 is probably the error.

Earlier I have drawn the P1dB compression point graph using fundamental power, which was generated from the HB2 Tone Swept Power using ADS2011, it was showing P1dB compression point as 14 dBm for 46 dBm of IIP3, Which is shown below figure name as P1_Graph_Using_HB2ToneSweptPowerTemplate.

Now I have drawn the same P1dB compression point graph using fundamental power, which was generated from HB1 Tone Swept Power using ADS2011, now it is showing earlier same frequency P1dB compression point as 3.559 dBm of 52 dBm of IIP3 simulated value, which is shown in figure below P1dB_Compression_Point_drawn_Graph_From_HB1ToneSweptPower and also P1 dB compression data generated using HB1 Tone Swept Power shown below name as P1_dB_Compression_point_drawn_Graph_From_HB1ToneSweptPower. I am confused which data I have to take from the HB1 Tone Swept Power simulated data and how to draw P1 dB compression point correctly.

I have simulated IIP3 data using HB2 Tone Swept Power of ADS 2011, and have simulated the IIP3 as 52 dBm. IIP3 Graph is shown in figure name as IIP3_Graph and also IIP3 data simulated data using HB2 Tone Swept Power shown below name as IIP3_data_Generated_Using_HB2ToneSweptPowerTemplate.

Really I am confused, where I have done mistake. Can you guide me properly how to draw P1 dB compression correctly using HB1 Tone Swept Power template of ADS 2011. But in the HB1 Tone Swept Power generated it is showing P1 dB compression point as 3.559 dB for 52 dBm simulated IIP3 using HB2 Tone Swept Power.

I have shown all the required graphs, please guide me where I have done wrong for drawing IIP3 and P1dB compression point and how to draw properly P1 dB compression point and IIP3 point using HB 1 Tone Swept Power and HB2 Tone Swept Power generated data.
 

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  • IIP3_data_Generated_Using_HB2ToneSwptPowerTemplate.pdf
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  • IIP3_Graph.jpg
    IIP3_Graph.jpg
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  • P1_dB_Compression_Point_drawn_Graph_From_HB1ToneSweptPower.jpg
    P1_dB_Compression_Point_drawn_Graph_From_HB1ToneSweptPower.jpg
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  • P1_dB_Data_Using_HB1ToneSweptPwrTemplate.pdf
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  • P1_Graph_Using_HB2ToneSweptPowerTemplate.jpg
    P1_Graph_Using_HB2ToneSweptPowerTemplate.jpg
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BigBoss

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Earlier I have drawn the P1dB compression point graph using fundamental power, which was generated from the HB2 Tone Swept Power using ADS2011, it was showing P1dB compression point as 14 dBm for 46 dBm of IIP3, Which is shown below figure name as P1_Graph_Using_HB2ToneSweptPowerTemplate.

Now I have drawn the same P1dB compression point graph using fundamental power, which was generated from HB1 Tone Swept Power using ADS2011, now it is showing earlier same frequency P1dB compression point as 3.559 dBm of 52 dBm of IIP3 simulated value, which is shown in figure below P1dB_Compression_Point_drawn_Graph_From_HB1ToneSweptPower and also P1 dB compression data generated using HB1 Tone Swept Power shown below name as P1_dB_Compression_point_drawn_Graph_From_HB1ToneSweptPower. I am confused which data I have to take from the HB1 Tone Swept Power simulated data and how to draw P1 dB compression point correctly.

I have simulated IIP3 data using HB2 Tone Swept Power of ADS 2011, and have simulated the IIP3 as 52 dBm. IIP3 Graph is shown in figure name as IIP3_Graph and also IIP3 data simulated data using HB2 Tone Swept Power shown below name as IIP3_data_Generated_Using_HB2ToneSweptPowerTemplate.

Really I am confused, where I have done mistake. Can you guide me properly how to draw P1 dB compression correctly using HB1 Tone Swept Power template of ADS 2011. But in the HB1 Tone Swept Power generated it is showing P1 dB compression point as 3.559 dB for 52 dBm simulated IIP3 using HB2 Tone Swept Power.

I have shown all the required graphs, please guide me where I have done wrong for drawing IIP3 and P1dB compression point and how to draw properly P1 dB compression point and IIP3 point using HB 1 Tone Swept Power and HB2 Tone Swept Power generated data.
Your P1dB Compression Point Definition is Wrong.Therefore you find nonsense resuts...

The best method is to draw Gain vs. Output Power chart to obtain P1dB compression point.Put your marker on this chart and find the Output Power where the Gain is dropped 1dB..

You chart looks "Saturated Output Power" but definitely NOT P1dB Compression Point..
 

SunnySkyguy

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image.jpg

See 1dB compression point
 

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