How to debug the output match of PA?

[TerryADS]

Dear friends,
I have a PA demo board.vendor supply us the MMIC PA load pull impedance and PCB.and duplex follow PA.my work is debug the board.some documents tell me:firstly connect the componts in series with 0R between PA and duplex,measure the output impedance,then match the load pull impedance to measured one.
Normally,when designing match,we use capacitor,micrstrip or inductor matching step by step.But debugging seems another thing(connect the componts in series with 0R,measure the output impedance,then match the load pull impedance to measured one.),why not we measure the impedance before duplex,get the impedance,and make match,but using the above process?
Thanks,

 

[pewang]

Honestly, I didn't understand your question because of my awful english.
Basically PA output match will be easy after you got the load pull data. You need to match/transform the load impedance of your PA which is the duplex input impedance in your case to the load-pull data you have (use Gama load data). This is only a basic impedance matching.

 

[vfone]

RF3166 is a GSM power amplifier which has internal 50 ohms output matching network, and you don't need to do load-pull at the output.
In fact you need to match the input impedance of the Murata switchplexer to this 50 ohms impedance.
Beware that you can get very poor isolation on this switchplexer if is not terminated properly on all ports at specific frequencies.

 

[TerryADS]

Thanks for reply! it is from rfmd introduction.let us say :structure=rfic pad(pa output port)+match circuit(need match)+switchplexer and match circuit=microstrip+pads in series The documents introduce firstly connect the pads in series (match circuit) with 0R of match network between PA output pin(IC pad) and switchplexer , and measure the PA output port(IC pad,and not solder RF IC), get the output impedance as ZL(the microstrip+0R+switchplexer ). Then using load pull impedance(vendor supply) as Zopt directly match to ZL. Why not measure the switchplexer input port(not include microstrip+0R of match network) for ZL,and do match ?
Thanks,

 

[vfone]

RF3166 has the output pretty well matched to 50ohms, but the switchplexer input is not perfect.
Some switchplexers needs certain impedance at their ports (use load-pull) to get best performances, especially isolation at some specific frequencies.
So, you have to match that certain impedance to the output impedance of the PA, or whatever is connected to that port.
Doesn’t make sense to load-pull an internally matched power amplifier.

 

[TerryADS]

Thanks.Vfone,you are right.It is for switchplexer.But why use 0 Ohm connected?As we know, microstrip is also counted on match network,and there are some pads between this microstrip as attached photo.Normal we use smithchart to do match by adding components or microstrip step by step from switchplexer input impedance to MMIC PA output Pad,or Via from PA output Pad to switchplexer,Now microstrip have been fixed,what we need is selecting correct components to match.Why the match is from ZL2 to 50R(RF output port),not ZL1 to 50R(RF output port)?
Thanks,

 

[TerryADS]

Anyone can help me?

 

[TerryADS]

Anyone?

 

[pewang]

use a 0 ohm is just because of easy for measurement i guess. because you have to sold the switchplexer on board and you have to consider the solder pad effect when design the match. the o ohm resister can be seen as a "point" in this case, it should be replaced by your designed matching network after your design completed.