characteristics impedance vs dielectric constant vs frequency

[VJKris]

Hi ,

I would like to know the relation between Er , Zo and frequency.

I have some issue on below statements:

1)As frequency increases, Zo decreases
2)As frequency increases,Er decreases

3)but in general Er increases,Zo decreases.

Based on statements 1 & 2 ,statement 3 will be false..So pls correct my understanding and let me know the actual relation.

Regards,
VJ

 

[FvM]

In a first order, Z0 and Er are frequency independent.

 

[marce]

Er is dependent on the dielectric material used (4.3-4.5 average for FR4 based PCBs.
Z0 is dependent on the topology used on a PCB design, number of layers proximity to planes etc etc.
Download and play with this:
https://www.saturnpcb.com/pcb_toolkit.htm

 

[VJKris]

Hi,

Yes i understand that the Er depends mainly on the material,trace geometry.

But my query is w.r.t the frequency..For eg at freq of 25-30 GHz,what would be the effects on Er,Zo?

Is there a way to quantify the effects of freq on Zo and Er?

Regards,
VJ

 

[marce]

Er depends on the material, nothing to do with trace geometry.
As to the rest use the Saturn calculator and observe the results, there are trace impedance calculators.
It is the ER and Zo that effect the EM wave at various frequencies not the other way round.