An interferometric technique for scanning near-field microscopy applications is proposed. The method is based on the association of a vector network analyzer, an evanescent microwave coaxial probe and a precise interferometer built up with a power divider, a phase-shifter, and an attenuator. Advantages, such as simplicity of operation, broad frequency band capabilities and high measurement sensitivity are achieved. In particular, a scanning near-field microwave microscope is built and experiments related to the measurement sensitivity in the frequency range 2-6 GHz are demonstrated. A lumped element model is also performed to represent the interaction between the probe and sample. A one port calibration model is developed to retrieve the reflection coefficient and then the electromagnetics properties of the sample.
Interferometric technique for scanning near-field microwave microscopy applications