In this work we present an automatic, deterministic procedure to fully design an isotropic metasurface antenna, self-consistently including the metallic feeding structure. The impedance pattern has full spatial variability in two dimensions, to allow designs otherwise difficult. The design is based on the integral-equation formulation with a current-only approach, in which the surface impedance profile is derived only after the optimal current is found; this allows to avoid the solution of the forward problem at all steps of the algorithm, with a drastic reduction of computational resources; it does not require any assumption on the impedance profile. We also show how a 3-D feed can be accounted for in a hybrid scheme partially employing commercial 3-D simulation software. Application examples address center-fed circular metasurface antennas, in which the feed is not connected to the metasurface, and rectangular “strip-like” leaky wave antennas (LWAs) where the metasurface is electrically connected to the feeding surface. In all cases, the design is carried out up to the final layout, and the full antenna is simulated to verify the design.

Beam-scanning antennas are employed in a wide range of applications, such as in satellite communications and 5G networks. Current commercial solutions rely mostly on electronically reconfigurable phased arrays, which require complex feeding networks and are affected by high losses, high costs, and are often power-hungry. In this paper, a novel beam scanning architecture employing a pair of planar metasurfaces, for use in thin reconfigurable antennas, is presented and experimentally demonstrated. The structure consisted of a radiative passive (non-reconfigurable) modulated metasurface, and a second metasurface that controls beam pointing, operating as a variable-impedance ground plane. Unlike other existing approaches, surface impedance variation was obtained by on-plane varactor diodes, no vias and a single voltage bias. This paper presents a design procedure based on an approximate theoretical model and simulation verification; a prototype of the designed antenna was fabricated for operation in X band, and a good agreement between measured results and simulations was observed. In the presented simple embodiment of the concept, the angular scanning range was limited to ${10}^{°}$; this limitation is discussed in view of future applications.

We present an automatic, deterministic procedure for the complete design of tensor metasurfaces, fulfilling field manipulation specifications and physical realizability constraints. Radiated field specifications are of the mask-type (inequalities). The tensor impedance pattern has full spatial variability in two dimensions, without any assumption on the tensor components or spatial variation envelope, yielding maximum flexibility. In particular, the choice of purely capacitive (or inductive) tensor impedances can be enforced. A compact representation of the impedance tensors allows to set independent bounds on the tensor components derivable from the chosen unit cell database: this ensures the synthesis of practically realizable structures. The design is based on the integral-equation formulation with a current-only approach, in which the tensor impedance profile is derived only after the optimal current is found; this allows to avoid the solution of the forward problem at all steps of the algorithm, with a drastic reduction of computational resources. 3-D metallic feeding structures are self-consistently accounted for in the design process (when present). An innovative process to optimally realize the whole set of unit cells is also described that allows to implement the full design without even computing the impedance distribution. Application examples address centerfed circular metasurface antennas, for broadside pencil beam, squinted beam, and shaped cosecant beam; special emphasis is devoted to realizing linear polarizations. In all cases, the design is carried out up to the final layout, and the full antenna is simulated to verify the design. The method to enforce design bounds, and the impedance-free unit cell design can also be employed in design methods which are not current-based.

In this work, we design and fabricate broadside-radiating edge-fed metasurface antennas with linear polarization employing a spatially-varying isotropic reactance; in order to avoid losses, the antenna is not terminated on a matched load. The design is achieved using a deterministic numerical algorithm for the synthesis of metasurfaces, combined with an accurate modeling of the feeding structure. The procedure effectively keeps into account the open-ended layout of the antennas; remarkably, optimization of radiation, and input impedance matching, results in structures that are of standing-wave type or traveling (leaky)-wave type depending on the substrate. In case of leaky-wave type of result, it is shown that the related open stop-band issue is avoided. The performance of the designed antennas is tested by full-wave simulations and measurements of fabricated prototypes.

We present an automatic, deterministic procedure for the complete design of tensor metasurfaces, fulfilling field manipulation specifications and physical realizability constraints. Radiated field specifications are of the mask-type (inequalities). The tensor impedance pattern has full spatial variability in two dimensions, without any assumption on the tensor components or spatial variation envelope, yielding maximum flexibility. In particular, the choice of purely capacitive (or inductive) tensor impedances can be enforced. A compact representation of the impedance tensors allows to set independent bounds on the tensor components derivable from the chosen unit cell database: this ensures the synthesis of practically realizable structures. The design is based on the integral-equation formulation with a current-only approach, in which the tensor impedance profile is derived only after the optimal current is found; this allows to avoid the solution of the forward problem at all steps of the algorithm, with a drastic reduction of computational resources. 3-D metallic feeding structures are self-consistently accounted for in the design process (when present). An innovative process to optimally realize the whole set of unit cells is also described that allows to implement the full design without even computing the impedance distribution. Application examples address center-fed circular metasurface antennas, for broadside pencil beam and shaped cosecant beam with linear polarizations, and a rectangular metasurface operating as an anomalous reflector. In all cases, the design is carried out up to the final layout, and the full structure is simulated to verify the design. The method to enforce design bounds, and the impedance-free unit cell design can also be employed in design methods which are not current-based.

In this work we present an automatic, deterministic procedure to fully design a metasurface antenna, self-consistently including the metallic feeding structure. The impedance pattern has full spatial variability in two dimensions, to allow designs otherwise difficult. The design is based on the integral-equation formulation with a current-only approach, in which the surface impedance profile is derived only after the optimal current is found; this allows to avoid the solution of the forward problem at all steps of the algorithm, with a drastic reduction of computational resources; it does not require any assumption on the impedance profile. We also show how a 3D feed can be accounted for in a hybrid scheme partially employing commercial 3D simulation software. Application examples address centerfed circular metasurface antennas, in which the feed is not connected to the metasurface, and rectangular "strip-like" leakywave antennas where the metasurface is electrically connected to the feeding surface. In all cases, the design is carried out up to the final layout, and the full antenna is simulated to verify the design.