Characteristic impedance Z₀ and effective dielectric constant εeff for microstrip transmission lines, using the Hammerstad-Jensen closed-form solution with finite-conductor-thickness correction.
The calculator uses the Hammerstad-Jensen closed-form expressions for microstrip characteristic impedance, which are accurate to within ~0.2% over a wide range of W/H ratios for εr up to about 16 — the standard reference cited in textbooks like Pozar.
Conductor thickness T is included via a width correction ΔW = (T/π) · (1 + ln(2H/T)), which slightly reduces Z₀ for thicker copper. This matters most for narrow traces on thin substrates (impedance-controlled flex circuits, mmWave PCBs).
Frequency is used only to compute guided wavelength λg = c / (f·√εeff). The static εeff used here is independent of frequency. For dispersion at higher frequencies (typically > 5–10 GHz on most substrates), apply a Kirschning-Jansen correction — coming as a separate tool.
Rogers RO4350B: εr ≈ 3.66 · FR-4 (typical): εr ≈ 4.4 · Rogers RT/duroid 5880: εr ≈ 2.20 · Rogers RO3003: εr ≈ 3.00 · Taconic TLY-5: εr ≈ 2.20.