In-Situ Quasi-Optical Characterization of High-Frequency Printed Circuit Laminates
Non-destructive quasi-optical characterization captures true millimeter-wave permittivity tensors, preventing costly phase velocity errors before lamination.
Gaussian Beam Propagation
Wave Distribution
Electromagnetic wave analysis in the millimeter-wave spectrum utilizes the mathematical description of a beam with a transverse field intensity profile. In quasi-optical characterization of printed circuit board laminates, gaussian beam propagation governs how high-frequency energy travels between focusing horns and the material sample. This modeling ensures that the wavefront matches the aperture of the sample holder.
Coupling Efficiency
High-frequency material testing requires passing a beam through the substrate to extract the complex permittivity without the feed-line losses of coaxial fixtures. The transmitting horn antenna shapes the wave to have a narrow waist at the exact location of the dielectric sample. Gaussian beam propagation formulas calculate the beam waist size and the depth of focus to guarantee that all energy falls within the sample boundaries.
If the sample is too small, diffraction at the edges will corrupt the measured reflection and transmission coefficients. By maintaining the beam waist smaller than the substrate sample width, scattering losses are minimized, which ensures highly accurate transmission measurements.
Measurement Calibration
Calibration of these free-space test benches employs standard metal plates and reference delay paths to isolate the sample behavior. The propagation calculations help position the focus lenses and horn antennas at precise distances. This precision directly influences the stability of the extracted loss tangent.