Just had a quick question regarding impedance of a microstrip as I am a bit curious on how this will work out in real life.

what happens if you change the width of a microstrip for only one place in the line as the example below. Lets say that all other factors/variables are the same for the full length.

How will this affect the impedance, will you have to calculate impedances individually and add these in series? What would be the correct way to calculate the total impedance of this line? How will the wider part affect the circuit, will it lower the impedance for the full length, or will the thin line limit this.

Any tips on the mathematics for this?

best regards,

Viggo