PCB Signal Integrity Tool
Transmission Line Loss Calculator
Calculate conductor loss, dielectric loss, and surface roughness effects for microstrip and stripline structures
Line Parameters
Enter your transmission line geometry
Geometry
mm
mm
mm
mm
Geometry
Material Properties
mm
mm
mm
mm
µm
GHz
GHz
Loss Components
Total transmission line loss consists of:
- Conductor Loss (αc): Due to finite conductivity and skin effect
- Dielectric Loss (αd): Due to polarization losses in substrate
- Roughness Loss: Additional loss from surface roughness (Hammerstad-Jensen model)
Loss Analysis Results
At operating frequency
Total Loss
--dB
Total attenuation over trace length
Loss per Unit Length
--dB/mm
-- dB/inch
Conductor Loss (αc)
--dB
Skin effect + DC resistance
Dielectric Loss (αd)
--dB
Substrate polarization loss
Roughness Loss
--dB
Hammerstad-Jensen correction
Characteristic Impedance
--Ω
Estimated Z₀
Skin Depth
--µm
At operating frequency
Effective εr
--
Effective dielectric constant
Loss Distribution
Conductor: --%
Dielectric: --%
Roughness: --%
Loss vs. Frequency
Total Loss
Conductor
Dielectric
Microstrip Cross-Section
Loss Calculation Formulas
Conductor Loss (Microstrip)
αc = Rs / (W × Z₀) [Np/m]
Rs = √(π × f × μ₀ / σ)
Rs is surface resistance, W is trace width, Z₀ is impedance, f is frequency, σ is conductivity
Dielectric Loss
αd = 27.3 × (εr/√εeff) ×
(εeff-1)/(εr-1) × tan(δ) / λ₀
tan(δ) is loss tangent, εeff is effective permittivity, c is speed of light
Roughness Factor (Hammerstad-Jensen)
Ksr = 1 + (2/π)×arctan(1.4×(Δ/δ)²)
α_rough = αc × Ksr
Δ is RMS roughness (≈ Rz/4), δ is skin depth. Factor ranges from 1 to 2.
Skin Depth
δ = 1 / √(π × f × μ₀ × σ)
Cu @ 1GHz ≈ 2.1 µm
Cu @ 10GHz ≈ 0.66 µm
Current penetration depth into conductor, decreases with √f
Effective Permittivity (Microstrip)
εeff = (εr+1)/2 + (εr-1)/2 ×
1/√(1 + 12×H/W)
Accounts for fringing fields in air above microstrip
Total Loss
α_total = αc×Ksr + αd [dB/length]
Loss(dB) = α_total × L × 8.686
Convert from Np/m to dB/m by multiplying by 8.686 (20/ln(10))