Scanning microwave coaxial cavity profiler [PCB conductor pattern profiling]

A λ/4 TEM open-ended coaxial probe cavity operating at 1 GHz is developed to provide profile information for conductor patterns on printed circuit boards. The cavity´s inner conductor is terminated in an open circuit probe tip projecting from the resonator´s end. The proximity of track metallization reduces the resonance frequency of the sensor and this perturbation is used to extract profile information about the conductor pattern of the sample. A novel 50 Ω tapered design is introduced to substantially reduce the cavity´s end area, and this in turn reduces the dispersion of the electromagnetic field. This modification significantly improves the resolution of the sensor. The measurement system and the sensor are described and results are presented for two different tapered designs.