1dB compression point (P1dB) for LNA

[chunlee]

1 db compression point

Hi All,

how to calculate Pin and Pout in dBm? how to determine 1dB compression point from Pin and Pout? How to convert 1dB to dBm?

Thanks for your kindly reply.


regards,
Chun Lee

 

[sgperzoid]

1db compression point

Hi All,

how to calculate Pin and Pout in dBm? how to determine 1dB compression point from Pin and Pout? How to convert 1dB to dBm?

Thanks for your kindly reply.


regards,
Chun Lee

Well, I think u did not catch the point quite well.
1dB compression point is the power level where the amplifier's gain is compressed by 1dB.
For example, a LNA's gain is 15dB at small signal input
while the input signal increase, the gain will reduce due to non-linearity of the LNA.
When the gain is reduced to 14dB, then the input power now is the input-referred 1dB compression point Pin-1dB, the out put power now is the out-put referred 1dB compression point Pout-1dB. The unit of those two figure of merit is dBm, that is the power input with respect to 1mW.
1dB and 1dBm are totally different thing.
1dB is a ratio actually and 1dBm is power value.

 

[chunlee]

p1db compression

Thanks to sgperzoid.

I have another question. How to simulate IP3 of the LNA using Hspice? Please give me some ideas.


Thanks,
Chun Lee

 

[danielr]

1db compression

Thanks to sgperzoid.

I have another question. How to simulate IP3 of the LNA using Hspice? Please give me some ideas.


Thanks,
Chun Lee

Dear Chun,
Using PSPICE put a bitonal signal (2 senoidals signals with a small frequency difference between them), simulate, change to FFT
IP3=(Poutput(dBm)-Pimd3rd(dBm))/2 + Poutput(dBm)
Poutput are the sum of the bitonal output (example 1MHz 1.1MHz)
Pimd3ard are the sum of the two IMD3 componentes (example 0.9MHz 1.2MHz)
I hope you understand me
Daniel

 

[chunlee]

compression point

Hi danielr,


My design is for operating at 2.4GHz. May i know what is the suitable start, step and stop time for transient analysis and FFT?


Thanks again,
Chun Lee