PA output matching.. Gain Vs Max power output

[J0hn]

Dear all,

For design a PA, the optimum load impedances for the max gain and max power output fall on different places on the smith chart. Is there any way to bring these two points closer together, so that when I do the output matching, both max gain + max power output can be obtained simultaneously. Please advise..

Thanks~~

 

[penghan]

Seems a mission impossible task

 

[WimRFP]

There is even a third thing, efficiency (or Power Added Efficiency).

Maximum gain, maximum output power and maximum efficiency will not be at the same point.

 

[vfone]

Using an input/output load-pull tuning you can optimize all PA parameters as power, gain, efficiency. linearity, etc.

 

[WimRFP]

You cannot get all at the same time. When you want, for example, high efficiency, you have to sacrifice gain and linearity.

One example is a class E output stage, you have to drive the active component harder to get the switching behavior. This does not adds to linearity. This is the reason that it is used for constant envelope modulation only. When using QAM or other non-constant envelope schemes, you also need power supply modulation.

 

[Element_115]

Note that Pout is = V^2/R, most PA's have a lower value of R, because
if R-->0 P --> ∞. Then if R is lower than Zo (50 Ω system) there will be more
reflection and less transfer of energy Lower Gain !

So they are typically contradicting requirements.