How to get a microstrip out from under a SMA connector?
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    rzvc created the topic: How to get a microstrip out from under a SMA connector?

    Hey guys!

    Assuming you have a straight, PCB mounted SMA connector. How do you get the microstrip out while keeping the 50 ohm impedance?

    There's going to be a fairly big chunk of metal from the connector's body, basically resting on top of the microstrip, which will add stray capacitance and reduce the impedance. How do you deal with that?

    Thank you,
    Razvan
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    tc replied the topic: How to get a microstrip out from under a SMA connector?

    I need a better understanding of the connection you are describing. As stated it seems as if the microstrip line on the substrate is touching the outer conductor of the SMA which means that the inner conductor is open(?) and the microstrip line is grounded. This is a bizarre connection. To start, I would use an exacto knife to cut the microstrip line away from the outer conductor of the SMA and then connect the inner conductor to the microstrip by a wire bond extending over the gap in the microstrip line you just created. For low frequencies this might be enough but at higher frequencies you would need to tune the inductance of the wirebond and the capacitance of the gap to try to get a better match. This is very simplistic but its a start.
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    rzvc replied the topic: How to get a microstrip out from under a SMA connector?

    Hi,

    There's soldermask between the connector's body and the microstrip. What I'm wondering is how to keep the 50 ohm impedance while routing that microstrip out of there.

    When the microstrip is wide due to the height of the dielectric, there's going to be a bit of capacitance added because the body of the connector will be much much closer to the trace than the reference plane. I'm wondering how you would normally deal with that.

    A different type of connector would definitely be a solution (edge mount for example), but let's say you can't do that and you have to use a through hole connector.
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    tc replied the topic: How to get a microstrip out from under a SMA connector?

    How is the connector oriented. Is it parallel to the substrate with the connector body touching the microstrip or is it vertical to the substrate, maybe on the backside with the inner conductor penetrating the substrate and then connected to the microstrip line metal? If it is a vertical connector, I would use a 3D EM simulator to work out the best configuration for a match.
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    rzvc replied the topic: How to get a microstrip out from under a SMA connector?

    Yeah, I guess I'll have to do that. I was hoping there was a standard way of doing it and I missed it.

    Thanks.
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