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CPWG trace widths and spaces

The Hittite document "Layout Guidelines For MMIC Components" is a great help but they only provide a single dielectric thickness, trace width, trace space and trace thickness combination that gives a 50ohm trace. It would be great to have a list of other combinations that work well with the various Rogers 4350 standard thicknesses. I noticed that many of the Hittite evaluation boards have trace widths and spaces that differ from the recommendations in the document but unfortunately the dielectric thickness and copper/plating thickness isn't mentioned so it is not so easy to duplicate.

Specifically I am looking for something that works well for a trace width of 15 to 20 mils (similar to what the HMC424 or HMC525 evaluation boards use).

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  • Hi Mark,

    I found this statement very interesting:

    "If you enter these into a grounded CPW calculator you will get approximately 55Ω.  The parasitic effects of the SMA connector drop the impedance to 50Ω."

    Is this a rule of thumb, from experimentation, or was this modeled using an EM simulator with the pcb board properties and the connector geometries?

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  • Hi Mark,

    I found this statement very interesting:

    "If you enter these into a grounded CPW calculator you will get approximately 55Ω.  The parasitic effects of the SMA connector drop the impedance to 50Ω."

    Is this a rule of thumb, from experimentation, or was this modeled using an EM simulator with the pcb board properties and the connector geometries?

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