What is a stub column

What is a stub on the circuit board?


What is a stub on the PCB and what is it used for? Stubs exist with PCB traces and also vias, why?


Reply:


They are used for impedance matching and filtering.

The image from Wikipedia below shows various stripline features used to create various elements etched into a circuit board with the descriptions below.

In the first column some simple planar filter structures are shown. The second column shows the open-wire equivalent circuit diagram for these structures. The third column is a semi-lump element approximation where the elements labeled K or J are impedance and admittance transformers, respectively. The fourth column shows an approximation with lumped elements, the further assumption being made that the impedance transformers are λ / 4 transformers.

(a) A short-circuit stub parallel to the main line.

(b) An interruption parallel to the main line.

(c) A short-circuit line coupled to the main line.

(d) Coupled short-circuited lines.

(e) Open circuit coupled lines.

Stripline vias (the little silver connections at the ends) create a strap through the board that connects to the baseplate below

Once you become familiar with transmission lines, you will understand the purpose of these elements. If you're not familiar, it's a scary but fascinating subject that I want to learn more about. It's the weird stuff about electricity. Know your enemy.

There is a little more explanation in a previous answer I gave to your previous question about reflections.





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