Trace Z

Trace impedance and skin depth

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Microstrip impedance

Example copper skin depth

Skin depth is 66.1 / sqrt(f) millimeters with f in hertz. 2.4 GHz is 2.4e9 Hz.

Worked example

H1 mmgroundW 2 mmS1 mm

Single-ended impedance

Characteristic impedance 51.002 ohm

Wide or narrow Hammerstad equation. eta_0 = 376.73 ohm. Branch uses W/H.

Effective permittivity 3.0669

Er_eff = (Er+1)/2 + ((Er-1)/2) * (1 + 12*H/W)^(-0.5)

Differential impedance

Differential impedance 83.257 ohm

Z_diff = 2 * Z0 * (1 - 0.48 * exp(-0.96 * S/H))

Delay

Delay 148.368 ps/inch

t_pd = 84.72 * sqrt(Er_eff) ps/inch

Delay per millimeter 5.841 ps/mm

ps/mm = (84.72 * sqrt(Er_eff)) / 25.4

Phase velocity 1.7118e8 m/s

V_p = 2.9979e8 / sqrt(Er_eff) m/s

Skin depth

Copper skin depth 1.3493 um

delta = 66.1 / sqrt(f_Hz) mm for annealed copper

Z0 uses the trace width. No thickness correction is applied.

Dielectric loss is not shown. The written loss product does not state whether frequency is hertz or gigahertz.