Asymmetric Stripline Impedance Calculator

Asymmetric Stripline Impedance Formula:

\[ Z = \frac{60}{\sqrt{\epsilon_{\text{eff}}}} \times \ln\left(\frac{5.98 \times h}{0.8 \times w + t}\right) \]

Effective Dielectric Constant (ε_eff):

dimensionless

Height (h):

Width (w):

Thickness (t):

Characteristic Impedance (Z):

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1. What is Asymmetric Stripline Impedance?

Asymmetric stripline impedance refers to the characteristic impedance of a transmission line where the signal trace is not centered between two reference planes. This configuration is common in multilayer PCB designs where signal integrity and controlled impedance are critical.

2. How Does the Calculator Work?

The calculator uses the asymmetric stripline impedance formula:

\[ Z = \frac{60}{\sqrt{\epsilon_{\text{eff}}}} \times \ln\left(\frac{5.98 \times h}{0.8 \times w + t}\right) \]

Where:

\( \epsilon_{\text{eff}} \) — Effective dielectric constant (dimensionless)
\( h \) — Height between trace and reference plane (mm)
\( w \) — Trace width (mm)
\( t \) — Trace thickness (mm)

Explanation: This formula calculates the characteristic impedance of an asymmetric stripline by considering the geometric parameters and the effective dielectric constant of the surrounding material.

3. Importance of Characteristic Impedance Calculation

Details: Accurate impedance calculation is essential for high-speed digital and RF circuit design to prevent signal reflections, maintain signal integrity, and ensure proper impedance matching throughout the transmission line.

4. Using the Calculator

Tips: Enter the effective dielectric constant, height, width, and thickness in millimeters. All values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between symmetric and asymmetric stripline?
A: In symmetric stripline, the trace is centered between two reference planes, while in asymmetric stripline, the trace is closer to one reference plane than the other.

Q2: How does effective dielectric constant affect impedance?
A: Higher dielectric constant reduces the characteristic impedance, while lower dielectric constant increases it, as they are inversely proportional in the formula.

Q3: What are typical impedance values for stripline configurations?
A: Typical values range from 50Ω to 100Ω, with 50Ω being most common for RF applications and 75Ω for video applications.

Q4: How accurate is this formula compared to full-wave simulation?
A: This formula provides good approximation for most practical applications, but for critical designs, full-wave electromagnetic simulation is recommended for higher accuracy.

Q5: Can this calculator be used for differential pairs?
A: No, this calculator is for single-ended asymmetric stripline. Different formulas are required for differential pair impedance calculations.