Optimal Apertures for Wireless Links in the Radiative Near Field

Traditional beams, such as Gaussian and Bessel beams, are commonly used in the design of wireless links in the near field. However, these beams are generally suboptimal for linking apertures at such standoff distances. To overcome this limitation, we propose the use of engineered quasi-bound states in the continuum (quasi-BICs) to design wireless links in the near field. We theoretically show that these quasi-BICs are optimal. A general design procedure is presented, starting with the identification of quasi-BICs for a given wireless link, and concluding with the design of a metasurface antenna that can transmit and receive the identified quasi-BICs. A design example at 30 GHz is presented to illustrate the design procedure.