Different sources are giving me drastically different characteristic impedance values, and am hoping someone will verify them for me.
Generally, with microstrip, I start with an online calculator to get close, then use the free TNT Field Solver to actually calculate the values. The values differ, but are at least in the same ballpark.
However, with a stripline, the values are so different that I think something must be wrong.
I'm targeting 50 Ohm. TNT says to use 9.4 mil traces. The calculator at EEWEB says the traces should be 25.7mil (!)
Which of these is correct?
Upper ground plane: 1.35 mil copper
Dielectric: 6.7 mil FR408 (3.67 dielectric constant)
Stripline layer: 0.7 mil copper
Dielectric: 47.0 mil FR408
Lower ground plane: 0.7 mil copper