Number of transistors in power combining (Doherty)

Hello,

This is my first post here. Hope I am posting in the right section.

I have a problem understanding a few sentences from a text I need to study. The problem is only in one word, which is repeated continuously in the sentences.

I am not used to this actual field (power combining for mobile communications) so I hope someone can help me to understand what it's meant here.

They are mentioning that the use of "an odd number of transistors for power combining" (which is necessary in some designs) lacks production consistency so they provide another solution.

These are some of the sentences as they appear in the text:
"The output power of a particular transistor is substantially fixed, which results in the phenomenon that an odd number of transistors are needed for power combining in some designs.Although the multi-transistor (including an odd number of transistors) Doherty power combining technique, especially the Doherty power amplifier technique realized with an odd number of transistors, was referenced in a lot of technical literature, it has been found that the production consistency of Doherty power amplifiers realized with an odd number of transistors is poor in practical application."

The problem is I don't understand what they mean with ODD here. Are they referring to an odd number (1, 3, 5, etc..) as opposed to an even number of transistors? or they mean an unusual number of transistors?...? Why would the production consistency be poor with an odd number of transistors?

Thanks in advance,

frangs

Odd (uneven) number, surely.

Hello FvM, thanks for the reply. But here is still something I don't see clear.

With "uneven" you mean "inconsistent" or a number pertaining to the set: 1, 3, 5, 6,...?

If it is the first case, why would some designs need an inconsistent number of transistors when they have just said that the ouput power of a particular transistor is substantially fixed?

Also, if it was the latter, I don't understand either why an odd number (1, 3, 5,..) would create this inconsistency in production.

Now, thinking of it, do they mean possibly a "variable" or "changing" number of transistors, like a design where you are able to choose the number of transistors working, in order to select the power combined? Pretty confusing to me...

The basic Doherty amplifier cell is using two transistors, thus I understand the quoted statement so that a multi-Doherty design would better use an even transistor number (n*2) although the designed power might suggest an odd number (n*2+1).

FvM said:

The basic Doherty amplifier cell is using two transistors, thus I understand the quoted statement so that a multi-Doherty design would better use an even transistor number (n*2) although the designed power might suggest an odd number (n*2+1).

Click to expand...

It could be so, but then the inconsistency in production is still unexplained. They could have said that it is better to use an even number of transistors than an odd one, for one on another reason, but I don't see the relation with inconsistencies, or at least it is not explained here.