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Transition SMA Endlaunch - Microstrip Line

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Tybi

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Hello,
how can I design a good transition from a SMA endlaunch to a microstrip line? I designed a pcb and used the recomended footprint (from the datasheet) of the SMA endlauch. The width of the pad of the signal pin was bigger than the width of the microstrip line. So a made a tapered transition. When I measured a simple through connection with two SMA endlauches and the microstrip line I get a horrible matching.
Here are my suggestions what could solve the problem:
- make the width of the pad of the signal pin the width of the microstrip line
- make a tapered cut out in the ground plane

By the way: do I have to solder the SMA endlaunch to the top AND the bottom ground plane of the pcb?
 

barry

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Please define “horrible matching”. How did you measure it?
 

BigBoss

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What is your frequency and what did you measure. Post your PCB design and measurement results here..
 

vfone

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- make the width of the pad of the signal pin the width of the microstrip line
This would be the best solution. You can edit the SMA footprint in the CAD PCB software that you use, and make the width of the pad the same as your microstrip line.
For SMA you can use a thin flat tab connector:
 

Tybi

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The frequency range is 5GHz to 6GHz.
The reflection is worse than -3dB and the transmission is about -7dB.
What is your frequency and what did you measure. Post your PCB design and measurement results here..
 

BigBoss

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The frequency range is 5GHz to 6GHz.
The reflection is worse than -3dB and the transmission is about -7dB.
Post a picture of the layout and the measurement set-up.
-3dB means to me that there is a more serious problem than mismatch.
 

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