RF amplifier top level design

Question

I am trying to design a more linear amplifier by using less linear amplifiers in a push-pull configuration. IE run the signal through a 180deg splitter, each leg running through identical amplifiers then recombining through a 180deg combiner.

This should increase the OIP3, OIP2, and P1dB but what happens to the noise figure? I would think it should decrease by 3dB but I'm not sure that is right and am having trouble finding information on it.

Are there any other consequences of doing this with amplifiers besides added costs of more amplifiers?

EDIT:

Frequency Band: HF (3-30Mhz)

Power: Max 12dBm

For example

^{simulate this circuit – Schematic created using CircuitLab}

As seen here in the second half, OIP3 and P1dB should improve by 3dB but no mention of the noise figure and that is what I am trying to figure out.

Answer 1

The devil is in the details. To the degree that the two amplifiers are matched and the phase splitters & combiners match up, you should be able to reduce the 2nd-order effects nicely -- but "nicely" means something like 10 or 20dB.

You won't change the 3rd-order performance much, unless each amplifier ends up running at half power and if the amplifiers perform well at half power.

And don't be surprised if you build a push-pull power oscillator, or make matters worse -- your scheme depends on good isolation between the amplifiers.