Impedance matching on Rf PCB

[enemra]

I have two questions in the image that I have attached. the image is of a power amplifier board.

1. The output of the amplifier has irregular copper trace with different length until the output SMA, which I pointed as (1). Doesn't this impact the impedance of the trace?
2. What is the use of two vertical traces before the output SMA, which I pointed as (2)?

Thank you

 

[FvM]

1. Stepped quarter wave transmission line for impedance matching
2. Transmission line stop filter for (probably 2nd) harmonic suppression

 

[BigBoss]

They are probably Open Circuited Stubs for matching purpose.

 

[volker@muehlhaus]

There is a nice article on using distributed elements on Wikipedia:

Distributed-element filter - Wikipedia

en.wikipedia.org

 

[BigBoss]

There is a nice article on using distributed elements on Wikipedia:

Distributed-element filter - Wikipedia

en.wikipedia.org

It might also be a filter but ..
are the open stubs too narrow ?? Seems to me open stub matching.

 

[vfone]

Should be a matching network, from the moment that in the datasheet is mentioned that the output impedance of BLF2425 is about 2.5ohms at 2450MHz.

 

[enemra]

Thanks to all who answered. Amazing.... Learning on RF part is never ending Thanks for the heads up.

 

[navet]

The section (1) is a matching network, his function is to present to the transistor some specific impedances (trade-off between efficiency and power output) in the band of interest.
The wide lines are near to the trans are low impedance, by stacking them together a transformer is created. Usualy this kind of network can be quarter wave sections / exponentiel tapper / or even Klopfeinstein taper (non linear step).

The section (2) is with no doubt a low-pass filter as an harmonic filter . The central freq of BLF2425 is 2.4GHz and according to the length of the stubs are tuned @ around 4.8GHz see attached a 10s quick EM simul.