A Switched Array Sounder for Dynamic Millimeter-Wave Channel Characterization: Design, Implementation, and Measurements
Xuesong Cai, Erik Bengtsson, Ove Edfors, Fredrik Tufvesson
Abstract
A prerequisite for the design and evaluation of wireless systems is the understanding of propagation channels. While abundant propagation knowledge exists for bands below 6 GHz, the same is not true for millimeter-wave (mmWave) frequencies. In this article, we present the design, implementation, and measurement-based verification of a reconfigurable 27.5–29.5 GHz channel sounder. Based on the switched array principle, our design is capable of characterizing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$128 \times 256$ </tex-math></inline-formula> dynamic double-directional dual-polarized channels with snapshot times of around 600 ms. This is in sharp contrast to measurement times on the order of tens-of-minutes of sounders by rotating horn antennas. The antenna arrays at both link ends are calibrated in an anechoic chamber with high angular sampling intervals of 3° in azimuth and elevation domains, which enables de-embedding the system responses of the sounder from the propagation channels. This is complemented with a bandwidth of up to 2 GHz, i.e., nanosecond-level delay resolution. The short measurement times and stable radio frequency (RF) design facilitate real-time processing of the received wave fronts to enhance measurement dynamic range. After disclosing the sounder design and implementation, we demonstrate its capabilities by presenting a measurement campaign at 28 GHz in an indoor laboratory environment.