Distributed wavefront shaping in radiative near-field sub-terahertz wireless networks.

In sub-Terahertz (sub-THz) wireless networks, the radiative near-field regime can no longer be ignored. Indeed, this less-explored electromagnetic regime can provide unprecedented opportunities to tackle the long-standing challenges of sub-THz wireless communication, including using focused beams to combat higher propagation losses and self-healing beams that offer enhanced resilience against line-of-sight blockage. Nevertheless, our mathematical modeling and experimental study find that such favorable near-field properties can be observed only within a smaller range of the nominal near-field Fresnel regime. To extend the functioning range where the use of near-field beams is advantageous, prior literature advocates the use of transmit arrays with larger form factors; however, such arrays may be impractical in real-world environments and are often difficult and costly to fabricate. In this study, we present the mathematical modeling and experimental demonstration of distributed near-field beam shaping using multiple coordinated transmitting apertures, hence, increasing the effective near-field regime. Our modeling is built on a detailed understanding of near-field electromagnetics, Fourier optics, and wave optics.