Electronic – Help with Matching circuit

impedance-matchingRFsmith chart

I'm using a SAW filter which has balanced input and output.

In the datasheet there is shown a matching application for 50ohms balanced output.

But plotting the S22 parameters into a Smith Chart and trying to get the same matching circuit is not working for me. I'm guessing the matching circuit is optimized for the center frequency 1090MHz.

Can someone please verify if the datasheet is wrong, or if it is just me (most likely 🙂 )

Datasheet and S-Parameters are available here:
http://www.triquint.com/prodserv/more_info/proddisp.aspx?prod_id=856096

Matching Network

Best Answer

@JakobJ From the datasheet it looks like the S22 parameter for 1090 mHz is about -8.2 dB at -177 degrees. Also, there are really an infinite number of combinations of values of components that will theoretically work in such a matching network, the same as there are an infinite number of components for an LC filter that will give you the same cutoff. Just because you come up with a different value graphically matching on the Smith chart doesn't necessarily mean that your solution is "wrong" or that the datasheet circuit is "right."

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