maximum power transfer VS maximum efficiency

Hi, all.

We all know that maximum efficinecy does not correspond to when maximum power transfer is occurred. Because, even in the ideal case of max. power transfer, its efficiency can be only achieved 50%.

Then, why engineers want to match the power using max. power transfer theorem?
One factor I can guess is that when reflection is more important than its efficiency. In this case, of course we would like to use max. power transfer theorem to minimize a signal's reflection. Is there any case we would like to consider efficiency more than max. power transfer? For example, an antenna has 50Ohm source impedance and I would like to make a filter that goes in front fo LNA. Should I make that filter have max. power transfer characteristic or should I ignore antenna's impedance such that max. voltage is transferred to the input of the LNA (max. power efficiency)? Assuming that the signal reflection is not much of concern. Since most of RF systems (obviously not all RF systems) deals with voltages (i.e. fc = 1GHz), why don't we place impedance bridging instead of impedance matching so that maximize voltage can be transferred into LNA. Except reflection reason, are there any other reasons?


Another related to this question is what is the difference between impedance matching and max. power transfer thoerem?
It seems that both requires complex conjugate of the source impedacne and the result is identical.

Can I understand them identical theorem, but only difference lies from their origins?


Any useful discussion is welcome~

for maximum power transfer, impedence should be conjugate matched.

maximum power transfer, is not the same case.
you should use impedence transform method the change the wanted impedence

for example, VDD 10V Z=50
maximum transferd power is 1W

but now you have 3V and you want to transfer 1W,
then you should change your impedence to 4.5.

In my opinion, impedance matching is a terminology related when talking about Ultra Wideband antennas UWB. In this case its difficult to get max power trasfer throughout whole frequency range. While max transfer term is used for single or multi resonant structures and when talking about a particular resonant frequency

Did it make scence

Both are two very different phenomena. Maximum power transfer is for linear amplifiers, maximum efficiency is for getting the most out of inherently non-linear amplifiers. Main target is PA's because there you can save most power.

It's two different worlds!