W-Band Imaging Sensor Using a Rectangular Waveguide Structure With Choke

A new application of a rectangular waveguide structure with a choke from Baskakova and Hoffmann (2021) is proposed for high-contrast imaging in the W-band. As with homogeneous lossy waveguides, the field distribution in front of the open-ended sensor is observed and a calibration/correction method is applied. The sensor is evaluated using planar metal- dielectric samples under test (SUT), thus enabling the detection of different materials with a standoff distance ranging from 0.08 to
$1.07~\lambda _{0}$
. The sensor can determine both amplitudes and the contrast of the reflection coefficients correctly at the reference plane of the SUT, which is not possible for state-of-the-art sensors. The maximum contrast of the imaging is greater than 26 dB. A spatial resolution and minimum resolution for the tracking of SUT local properties of 1.9 mm are achieved at standoff distances of 2 and 1 mm, respectively.