Millimeter-wave near-field imaging with bow-tie antennas

Abstract

A near-field reflectometry experiment operating at 60 GHz is built in view of material and circuit inspection. Experiments are always obtained in constant height mode of operation. The bow-tie near-field probe acts mostly as a linearly-polarized electric dipole and allows strongly subwavelength resolution of ≈ λ/130. Its interaction with sample is shown polarization dependent and sensitive to both the local topography and the local dielectric constant or metal conductivity. Resonant and non-resonant probes are both evaluated.

Millimeter wave near-field imagery with micrometer spatial resolution

“…As a result, a resolution of ≈ 2 µm is obtained @ 3f in Fig. 1d instead of only λ/130 previously [7].…”

“…Our 60 GHz NFSMM is a very low-cost system built using a reflectometry setup with a Gunn source, a dual-directional coupler and Schottky detectors. Near-field sensing is obtained with a home-made bow-tie probe fabricated by attaching two metal triangles to the open end of a WR15 waveguide [7]. Various probe metals and geometry (gap g between triangles tips) were studied.…”

“…The detection process is thus part of the image formation [6]. We recently developed a NFSMM experiment operating at 60 GHz similar to SNOM with a bowtie near-field probe that interact mostly by a tangential electric field [7] instead of the longitudinal field of more classical tips. In this communication we construct a probe-sample model and improve the detection process to achieve a λ/2500 resolution.…”

Full-wave modeling of broadband near field scanning microwave microscopy

“…However, there exist significant challenges in the numerical modeling of nano-structures and nano-materials at microwave frequencies. Unlike near field imaging in the optical regime for NSOM applications where the tip-size is around at the infrared range 34 , 35 , or probes at millimeter scale for microwave applications 24 – 26 . The SMMs use an AFM probe with tip dimensions that can be less than at millimeter-wave frequency band 10 .…”

Traceable measurement and imaging of the complex permittivity of a multiphase mineral specimen at micron scales using a microwave microscope

“…This fundamental limitation of a monopole probe tip has important implications for measurements on multiphase materials. Several papers demonstrate that a smaller sensing volume can be obtained using probes based on parallel-plate lines [16][17] [18] or miniature bow-tie antennas [19]. These types of probe can be difficult to fabricate to the ideal level of precision, and so problems such as air gaps between the probe tips and specimens, and poor edge definition of metal plating, are likely to occur.…”