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# Electrical Lenght of Microstrip Transmission Lines

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#### denizduran

##### Member level 2
I am building a conventional feed network using lambda/4 transformers to feed my patch antenna array. Sometimes, I need to increase the length of my transmission line to fit everything. For example, I have a 50 ohm trl as a starting point, when I split that trl I have two 100 ohm trl branches but I need those branches to be longer, so I increase their length by half a wavelength. Should I be designing all the other trl half a wavelength longer?

Not clear what you are exactly trying to achieve. Without specified source and load impedance, we can't recognize a transformer.

The transformer isn't the point here. All I want to know is; if I change the electric length of one transmission line (like the 100 ohm trl) do I have to change the electric length of all the other trl's in the feed?

The transformer isn't the point here. All I want to know is; if I change the electric length of one transmission line (like the 100 ohm trl) do I have to change the electric length of all the other trl's in the feed?
I didn't understand what you exactly mean but if you change the Length of any Transmission Line which is Loaded by Arbitrary Impedance, the Impedance that is seen at L=z point will also be changed.
That's why it changes depending which Impedance you desire at L=z point.
But you query is not so clear.

I am just trying to design a feed system. I need to make some of my lines longer for the transmission lines not to intersect. If I double the electric length for one tranmission line (from 180 to 360 degrees) do I have to change the dielectric length for other transmission lines in the feed?

I am just trying to design a feed system. I need to make some of my lines longer for the transmission lines not to intersect. If I double the electric length for one tranmission line (from 180 to 360 degrees) do I have to change the dielectric length for other transmission lines in the feed?
If the Feeding Transmission Line has 50 Ohm Characteristic Impedance, no matter its length is. But don't forget that no Transmission Line has 50 Ohm "Pure" Characteristic Impedance so changing its length may change the Driving Point Impedance too. So some tuning may have necessity ( may be not, depends on how it will be tolerated )

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