Bianisotropic Huygens’ Metasurface Pairs for Nonlocal Power-Conserving Wave Transformations

Microwave Huygens’ Metasurfaces: Fundamentals and Applications

“…In [47], a phase-retrieval algorithm was employed to find the appropriate phase profile that the fields should acquire from M1, so that the power density profile at the input of M2 is the desired one. On the other hand, in [48] the fields at the output M1 were expanded in a set of basis functions with unknown complex weights. By carefully employing Maxwell's equations to propagate the field distribution, the power density profiles were calculated at the inner boundaries of the two HMSs as a function of the unknown weights.…”

Metasurface Design Using Electromagnetic Inversion

“…Lastly, we extend the design framework to the scenario in which two metasurfaces are used in a cascaded fashion to produce a desired transmitted field, similar to the backpropagation-based technique in [32,33]. A single passive and lossless metasurface is limited in the variety of field transformations that it can support due to the fact that local power must be conserved at each and every unit cell.…”

“…While practically necessary, the drawback of enforcing LPC is that the supported field transformations are restricted. One possible solution is to utilize multiple metasurfaces in succession, as described in [32,33,109,110,111]. In this scenario, the field transformations at each metasurface still satisfy LPC, but the transmitted field from the last metasurface no longer has to have the same power distribution as the field incident on the first meta-surface.…”

“…These subwavelengthly thin structures can perform arbitrary field transformations by imposing appropriate generalized boundary conditions, providing a level of control over some desired field produced by a known incident field. This fundamental ability has led to a variety of applications, including generalized refraction and reflection [14], polarization manipulation [12,13], spatial processing [18], impedance matching [103], radiation pattern tailoring [32], and others.…”

“…Recently, different methods have been suggested to enable more amplitude control by considering total power conservation (TPC); e.g., see [104] for different examples. One of these methods [32], [33] uses two metasurfaces instead of one, each of which individually satisfies LPC. However, collectively, the two-metasurface system only satisfies TPC.…”