Résumé
A 60 GHz high spatial resolution millimeter near-field scanning microwave microscope (NFSMM) system is developed with aim of non-destructive testing of material and circuits. Like SNOM, it involves a modulation of the probe-to-sample distance. We derive an analytical model of the probe detection versus the standoff distance and the harmonic order used for lock-in detection. Both the model and experiments exhibit the filtering of the high spatial frequencies with greater efficiency obtained at highest harmonics. When combined with a specially designed bow-tie probe and an optimized detection setup operating on the third harmonic it yields a resolution of ≈ 2 μm (i.e. λ/2500).