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# DC resistance of microstrip line

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#### MobiNaz

##### Full Member level 3
Hi all,

Could anyone please provide a link explaining dc resistance of a microstrip line?

---------- Post added at 03:51 ---------- Previous post was at 03:20 ----------

I found this paper useful.

A.R. Djordevic and T. K. Sarkar, "Closed-form formulas for frequency dependent resistance and inductance per unit length of microstrip and strip transmission lines," IEEE Trans. Microwave Theory Tech., vol. 42, pp. 241-248, Feb. 1994

But is the dc resistance almost zero or little under all conditions

But is the dc resistance almost zero or little under all conditions

If you make the width (cross section) of the line very small, the resistance increases, of course.

While exact solution of frequency dependant resistance is a really difficult problem of theoretical electrical engineering, DC resistance is rather a beginners exercise. Simply consider conductor cross section, length and resistivity.

I think that the question might refer to this thread:

There, an ideal DC voltage source (= perfect RF short) was used and of course, you can use a lambda/4 transmission line to transform that ideal RF short into a narrowband RF open ciruit. This would not be the equivalent of the resistor circuit, but an alternative solution to feed DC to an RF line. **broken link removed**

I think that the question might refer to this thread
Yes. Related to the purpose and value of the resistor in this thread, it would be actually sufficient to say, the TL DC resistance is about zero.

the DC resistance can be 0. it is only realted to the loss dB per miter.

---------- Post added at 16:29 ---------- Previous post was at 16:28 ----------

Z0= (l/c)^0.5

In my experience, trace width is 0.5mm, and length is about 40mm, current is about 0.5A, the voltage droped from 5V to 4.8V, so the DC resistance is 0.2V/0.5A/40mm=0.01 ohm/mm @0.5mm width. In my test, there is only DC on the trace, no RF signal.

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so the DC resistance is 0.2V/0.5A/40mm=0.01 ohm/mm @0.5mm width
1 Ohm/m can be in fact calculated for a "1 oz" (35 µm) x 0.5 mm copper trace. You don't need a measurement.

tony_lth

Points: 2