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Layout PCB RF AMplifier

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Fhadz

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2019-04-11_19-39-50.jpg

hello i want to ask,if i design the layout pcb like a picture, if the transistor input that I rounded was sharpened like in the picture what would affect the matching impedance?
 

Are you sure that the Impedance Matching Circuits have been well designed ?? Because TLs seem to me a bit weird..( Their Widths are too large )
 

yes sure, this my schematic on ADS2019-04-01_7-44-42.jpg
 

Sorry ididnt understand about ground connection, and do you think that can be realized? because the simulation results are very good?
 

Not sure how you arrived at the TL matching network. It looks considerably different from reference design in CGH40006S datasheet. Consider that the MLIN model doesn't cover the discontinuities at the line ends.

The worst point of your layout is however the ground connection of bypass capacitors and transistors. I'm sure that the demonstration PCB uses multiple small vias below the QFN exposed pads. The different ground connection of capacitors is obvious on the photo.

cree.jpg

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the simulation results are very good

Which simulation results? Did you simulate the actual geometry, e.g. with ADS Momentum? If not, can you know how your PCB behaves? The demonstration board is assuming 35 pH source inductance for the transistor, can be hardly achieved with a single via.
 

So, what should I do ? Are there suggestions or can you help?
 

Sorry ididnt understand about ground connection, and do you think that can be realized? because the simulation results are very good?

What is your target ?? Designing a Power Amplifier or ?? At which frequency ??

Can you illustrate your simulation results here ??
 

This for my final project at my collage, i choosw 5,6 Ghz imean a simulation good is a S parameter simulation its reach my target
 

I believe that the simulation results are good. But the simulation circuit is far from representing your PCB design. It has huge parasitic inductances due to insufficient ground connections. And the matching transmission line structures need more accurate modelling than by simple MLIN segments.
 

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