Microwave power amplifier

[mkassem]

hallo

i am designing a power amplifier using a motorola transistor
i would like to ask how can i use load pull simulation to design it for broadband operation form 1.8GHz to 2.2 Ghz
also wht should i do with the harmonics
some books say short it (crips book)
other papers (an experimental study of the effects of harmonic loading on microwave MESFET oscillators and amplifiers)say it should be optimaly terminated ,but not short circuited

thanx

 

[BigBoss]

Normally Zload at harmonics should not be shorted.In this case you'll see total power is lower than delivered power to the load due to harmonics powers.

In ADS , there is a good Design Guide for Power Amplifiers. With this Design Guide , you can simulate your power amplifier with different Zload at different harmonics as well as Zsource.

I have tried many times and measured but unfortunately this simulation is based on accuracy of the models and very sensitive process variations.

Briefly , it's quite good method to use ADS's PA Design Guide but measurement is best with slight tuner.

Rgrds

 

[mkassem]

iam designing a class A PA, i used the load line method to get the optimul internal load resistance and made deembeding and power match,(like described in crips book)
i want to ask abt stability ,how can i control it also how can i calculat and control the gain, to my knowledge the bias point controls the maximum linear output power ,but how can i control the gain

when i used load pull Zload for maximum power is gives me maximum power but not in the linear range
also in loadpull simulation ,wht abt the source impedance should i always leave it 50 ohm

thanx

 

[mkassem]

now iam trying to design it in class AB ,any advice how to start designing a class AB applifier any documents are wellcomed
thanx

 

[cybq]

I think the power gain can be simulated with the corresponding DC bias s parameters.

 

[pewang]

if want higer gain,try to tune its bias point to class A.this will give a higher gain but lower effeciency and lower output power(because heat).also good linear.