Dielectric Metrology Tool
A specialized microwave test fixture determines the complex permittivity of low loss thin film laminates through the excitation of resonant modes between two conductive plates. The balanced circular disk resonator functions by clamping a sample between two metallic disks to form a resonant cavity where the field is contained within the dielectric. This arrangement minimizes radiation losses and allows for high precision extraction of the dielectric constant and dissipation factor.
Measurement Physics
Resonant behavior depends on the physical diameter of the disk and the electrical properties of the material under test. The device relies on the transverse electric TE011 mode which lacks a vertical electric field component at the conductor surfaces. This specific mode effectively eliminates errors associated with air gaps between the sample and the plates that would otherwise plague high frequency measurements.
Accuracy remains contingent on the parallelism of the disks and the stability of the network analyzer calibration during the sweep.
Application Boundary
High frequency circuit designers use the resulting data to model transmission line impedance in millimeter wave applications. Since the balanced circular disk resonator requires a circular sample of specific dimensions, it is primarily used in material qualification instead of process monitoring of finished boards.
