Calibration of millimeter-wave channel sounders for super-resolution multipath component extraction

Millimeter-wave communication systems will rely on highly directional antennas to compensate for the greater pathloss expected in their frequency bands of operation. Hence, electronic beamforming will form a cornerstone for the technology. For the effective design of these systems, accurate estimation of the multipath component characteristics of the environment is essential, in particular their three-dimensional angle-of-arrival. Super-resolution techniques enable extracting these components with high fidelity, even in the presence of diffuse scattering. Applying these techniques, however, requires precision calibration of our 28, 60, and 83 GHz channel sounders. This paper outlines calibration procedures implemented to deliver such precision. Specifically, we account for impulse-response distortion stemming from internal system reflections and linear distortion by RF components. We also characterize the phase centers and complex antenna patterns of the receiver array elements, and gauge the drift of our synchronization clocks.