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Design >> RF Design >> metal line width
https://designers-guide.org/forum/YaBB.pl?num=1213063873

Message started by aaron_do on Jun 9^th, 2008, 7:11pm

Title: metal line width
Post by aaron_do on Jun 9^th, 2008, 7:11pm

Hi all,

I have a metal line carrying an LO signal but not DC current. The line is quite long (~0.5mm) and the LO is at 2.4 GHz. I doubt that the series resistance of the line will matter since it is driving a rather small capacitive load, but i'm worried that the capacitance of the line will be large. Therefore, i decided to route it using a line width of only 0.4 um. Will there be any issues with using such a long line with such a small width? Is it better to use a wider line?

thanks,
Aaron

Title: Re: metal line width
Post by ACWWong on Jun 10^th, 2008, 2:02am

Hi Aaron,

you should be able to "extract" the capacitance of your LO line and put it back into the simulation. This is also true for the resistance and inductance using tools like Assura etc.

anyway you should use higher/top level metals far from substrate and minimise other metals crossing... i don't see a problem with 0.4um * 0.5mm length if properly extracted and accounted for, but what I would say is that if the track was say 0.8um wide, then roughly the resistance would half, but the capacitance would only increase by say 33% and not double because fringing capacitance should be dominate over bottom plate capacitance for such a thin line.

cheers
aw