Transmission line temperature effects

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New for June 2020

An often ignored topic.  Cables, microstrip, waveguide all change with temperature.  And they almost always get lossier when they are hotter.

Length change

Length change: you can model the length change using a simple tgemperature coefficient of expansion.  On a copper board, this might be 17ppm/C. So for the airboren temperaure range of -54 to +85C, expect 0.24% change. This might not be a big deal at all, eacept if you were designing a time delay unit and you wanted to maintain accuracy over temperature. In that case you might want to install a heater on your delay lines to keep tham at constant temperature!

Resistivity change

Here you can model the loss change by varyng the rsistivity of a transmission line with temperature


Delectectric properties change

This is an effect that is not well studied, and is usually ignored.  Loss properties of deielctric may change, but thay changeis probably swamped out by the metal loss effects,

One effect that is common is that dielectr expands more than metal when it gets hot. In the case of coax cables, there may be permanent changes when dielctric squeezes out the ends. If you are looking for high temperature cables consider silicon-dioxide-filled cables.  Get your wallet out, they start at $1000!


Author : Unknown Editor