A 77 GHz Near-Field Probe with Integrated Illuminating Waveguide used for Reflectarray Characterization

In this paper, a near-field probe with integrated illuminating waveguide for frequencies around 77 GHz is introduced. For such high frequencies, alignment of transmitter and receiver probes in the near-field measurement setup are difficult. So the purpose of this work is to integrate both devices into one setup for an easy and reproducible measurement procedure. The measurement probe is used to characterize individual patches on the surface of reflectarray antennas, placing the device a few millimeters above the antenna surface. This requires a high spatial resolution and a insignificant influence of the probe on the examined structure. The ability of the developed probe has been investigated in simulations and verified in near-field measurements at reflectarray structures for 77 GHz. In this extended paper version, the setup is used to investigate a test-array with polarization twisting elementary cells and the lower reflector of a folded antenna, whose characteristics are based on a bifocal design process.