Open quarter wave transformer question

n3x · Aug 11, 2010

Hello,

I'm using a microstrip quarter wave transformer with an open end connected to a short stub(part of impedance matching for a transistor).

As far as I know a wider microstrip(smaller Z0) for the transformer would result in better bandwidth. However I cannot understand why!

Can you help me with understanding the connection between the bandwidth and the impedance of the line?

I'm currently using "Microwave transistor amplifiers: analysis and design" by Gonzalez, and I don't have access to ieee or similar sites.

Any suggestions would be helpful.

Edit:
From: **broken link removed**

The open circuit stub trick (creating an RF short circuit that is DC-open) is often done with lower impedance lines than Z0. This effectively gives a wider bandwidth. An even better trick is to use a microstrip radial stub; it provides a low impedance, it doesn't suffer from a large distributed tee junction that a constant-width low-impedance stub would, and it just works better (trust us!)

This is what I'm trying to understand (not that i don't trust microwaves101 )

Thanks!

akrcal · Aug 12, 2010

Hello,

When the Zo is lower then the tolerances of the line length becomes less critical. It happens because due to the formula Zo*j*tan(BL). So for large Zo the value of the expression will vary more with respect to the line length

cheers.
akr

Open quarter wave transformer question

n3x

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akrcal

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n3x

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Open quarter wave transformer question

n3x

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