At which frequency we chose dielectric constant

If I have a digital signal of 1 GHz clock frequency. How do I chose the dielectric constant value of the dielectric material ? Do I need to look for the dielectric constant value at 1 GHz ? I don’t think so because 1 GHz is not the bandwidth.

I understand that bandwidth of a digital signal is related to rise time or edge rate but if I do not have that information with me then how do I estimate the bandwidth for a given digital signal having clock frequency 1 GHz.

I guess it is the bandwidth of the signal at which I need to chose dielectric constant value, right ?

At 1GHz dielectric constant is not what PCB designers focus on. The more important rules to follow would be the width of traces and their proximity to other traces and components.

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A true digital signal is made up of infinite harmonics combined with the base frequency. I suspect that you will want to select a harmonic frequency value somewhat higher than the base frequency. If your base frequency is 1GHz and it is digital, I assume you will want to select a 5GHz or 10GHz Dk value to use as an input to for impedance track geometry calculations.


The frequency operation is only one of the factors that’s important when choosing dielectric constant. The operating frequency range is probably the most important, but even then most of the manufacturers only list one or two dielectric constant values (1 GHz or 10 GHz are usually the most common, especially for high-frequency low-loss materials).

So you should check how much room you have for your traces because a low Dk would allow you to make your them smaller. The board thickness is also another factor because that determines the size of your traces.

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