Wideband Synthetic-Aperture Millimeter-Wave Spatial-Channel Reference System With Traceable Uncertainty Framework

Abstract

This paper describes a wideband synthetic-aperture system and the associated Fourier processing for generating high-resolution spatial and temporal estimates of the signal propagation environment in wireless communication channels at millimeter-wave frequencies. We describe how to configure the synthetic aperture system for high angular resolution by sampling the progression of signal phase across a large planar area in space. We also show how to synthesize discrete measurements of the channel frequency response taken sequentially over a wide bandwidth to create power delay profiles (PDPs) in specified angular directions with high delay resolution. We provide a rigorous uncertainty analysis that can be made metrologically traceable to fundamental physical standards. This uncertainty framework can propagate the errors inherent in the measured signals through to the final channel estimates and derived parameters such as root-mean-square delay or angular spread. We illustrate use of the system in conjunction with two different analysis tools to extract both narrowband and wideband parameter estimates from the synthetic aperture, allowing its use as a stand-alone channel sounder or as a tool for verifying the performance of wireless devices.

A Machine-Learning Approach for the Exemplar Extraction of mmWave Industrial Wireless Channels

“…Using true-time delay beamforming, the measured S 21 parameters were coherently processed to steer the array main beam and to generate directional PDPs. The details of data processing and the corresponding uncertainties are described in [48], [51]. A frequency-invariant taper was computed and applied across the aperture in post-processing to reduce the sidelobe levels of the array response in the boresight direction.…”

“…The receive horn used to generate the synthetic aperture was also pointed towards the control panel in a bistatic configuration and with an orientation that reduced the lineof-sight coupling between transmit and receive antennas as much as possible. The spatial sample points of the synthetic aperture [51] were located on a 35-by-35 planar grid with 3.75mm spacing that corresponds to λ/2 at 40 GHz. The minimum two-sided beamwidth of the beamformed output of the synthetic aperture array is 2.9 • when measured in the boresight direction at 40 GHz.…”