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# power amplifier design using microwave office(I have some principle question)

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#### young.microwave.eng

##### Full Member level 3
Dear roommates
I'm going to design some power amplifier in X-band using microwave office.
seems there are two methodes for desing.1)using S parameters s2p file and 2)using non linear model.would you experts describe me the difference between two methods?(if two methods that I mentioned is correct)
I meant when I have to use S-parameters and when non-linear model

Dear Friend..
Don't misunderstand me but I should say .. do not even start to design a PA at X-Band if you don't know the difference between s-parameters and nonlinear models..

dear bigboss
I've studie microwave transistor amplifier design by gonzaless and it has been completly self study process.I know matching and other primary knowledge but as my ID indicate i'm completly newborn to microwave engineering
in comparison to you and others.so I will be appreciated if guide me

S Parameters give you a 1 to 1 correlation of input signal to output signal on a component. If you look at the data inside an S2P file, you see voltage magnitudes and phases, relative to an injected signal of 1V at 0 degrees. E.g. if S21 is 0.5 and -90.0, then the output signal at port 2 will be 1/2 the voltage present at port 1, and 90 degrees out of phase. S11 is the voltage signal reflected by port 1 (signal incident at port 1, and signal coming back out of port 1... thus, S11). Those types of values are given for sinusoidal inputs over a range of frequencies. This is simply a snapshot of the device's performance... generally under some know bias conditions, in the case of a transistor. That is a linear model.

Touchstone SnP file format
Class notes - S-Parameter intro

Non-linear models are effectively schematic-based circuit models that take into account things like compression and signal distortion. If you can look inside a non-linear model for a transistor, you'll see things like series inductance on the leads, capacitance between collector-base-emitter or gate-source-drain nodes, and resistive parasitic elements. Those, paired with the non-ideal voltage-current characteristics of a transistor model, give you a good idea of how a part will perform outside of a linear mode of operation. That type of model is good for designing amplifiers that will be running outside of class A or lightly-compressed class AB (both *fairly* linear amplifier topologies).

young.microwave.eng

### young.microwave.eng

Points: 2
dear bigboss
I've studie microwave transistor amplifier design by gonzaless and it has been completly self study process.I know matching and other primary knowledge but as my ID indicate i'm completly newborn to microwave engineering
in comparison to you and others.so I will be appreciated if guide me

Sorry about my argue but I should have to say..
Microwave Engineering can certainly be understood by self studying but it should neccessarly be noted that every study starts with small steps.Reading some textbooks,application notes,engineering bulletins,researching ph.d thesis etc. will of course help you and improve your level.
But there is one thing that you shouldn't forget.The life is real and simulators are just tools that help us.
Before doing a mighty design such as X-band power amplifier, I recommend you to start some primitive designs to learn linearity.nonlinearity,noise,matching,feedback,layout techniques,models,real and ideal components,grounding,single ended vs. balanced,thermal issues,parasitic couplings and avoiding, etc..etc..
So, there plenty of knowledge are waiting for you to learn.

First things first, you should consider those friendly warnings.

hi
I should take your advice and improve my knowledge for sure.But I have to say that I have some experiences in circuit design and layout techniques and I should improve it step by step.as you could conclude this forum is one of the best ones.I have some experiences in LNA design and PCB manufacturing.now i'm going to enter to power amplifiers.so I will be appreciated If you and other experts guide me with their experiences and knowledge.
thanks again

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