Wave Impedance Determination for PCB SIWs Considering Metal Roughness Loss Effects

Area of Science:

• Electromagnetics
• Microwave Engineering
• Materials Science

Background:

• Substrate-integrated waveguides (SIWs) are crucial components in modern microwave circuits.
• Accurate modeling of SIW impedance is essential for effective circuit design.
• Existing models often overlook conductor losses, impacting accuracy.

Purpose of the Study:

• To develop a novel expression for the complex wave impedance of SIWs for the dominant TE10 mode.
• To enhance the accuracy of modeling the imaginary part of the wave impedance.
• To provide a method for characterizing SIWs for circuit design applications.

Main Methods:

• Derivation of an expression for complex wave impedance incorporating conductor losses.
• Consideration of conductor surface roughness effects on longitudinal currents.
• Validation through comparison of simulated and experimental insertion loss and S-parameters.

Main Results:

• The proposed expression accurately determines the complex wave impedance of SIWs.
• Additional conductor losses due to field-material interaction are systematically identified.
• Reconstructed S-parameters using the determined wave impedance show good agreement with experimental data.

Conclusions:

• The developed expression provides a more accurate method for modeling SIW complex wave impedance.
• The inclusion of conductor losses and surface roughness is critical for precise characterization.
• This work facilitates improved matching characteristics and circuit design for SIWs.