Omega-type bianisotropic Huygens' metasurfaces offer a novel approach for controlling the aperture field distribution of leaky-wave antennas. This paper presents a methodology utilizing a parallel-plate waveguide with a metasurface as its top plate. Previous limitations on constant leakage factor are addressed using a slowly varying amplitude approximation in order to satisfy Maxwell's wave equation, enabling the design of the radiation pattern. A semi-analytical algorithm is employed to obtain the required multi-layer unit-cell geometries. Here, the inter-layer coupling is taken into account, enabling an efficient synthesis of these antennas. Several designs presenting different pointing angles and aperture field distributions are carried out, showing very good agreement between theory and realistic simulations without further full-wave optimization. Finally, the design process is experimentally validated through several prototypes, whose measurements are shown and discussed. These results, demonstrating straightforward semi-analytical synthesis of versatile aperture profiles, would significantly broaden the applicability of such antennas in next-generation wireless systems.

This paper presents a method for effectively characterizing the dielectric permittivity of nematic liquid crystals across a broad frequency range. These materials show significant potential for reconfigurable devices operating in microwave and millimeter-wave frequencies. To achieve this goal, an additive manufacturing technique is used to create a microstrip line that can be filled with liquid that acts as its substrate. The liquid crystal (LC) is then biased to modulate its permittivity. After manufacturing, a time-gating approach is used to extract the permittivity, eliminating the need for in-fixture calibration, such as Thru-Reflect-Line (TRL). Finally, the approach is validated through simulations and experimental results, which closely align with those reported using other methods in the bibliography.

An equivalent-circuit topology for two-port lossy non-symmetric reciprocal networks is proposed. The circuit topology is based on the eigenstate decomposition. The proposed circuit consists of two immittances and two transformers with a single complex turns ratio, all obtained from the eigenvalues and eigenvectors of the admittance or impedance matrix of the network in a straightforward way. The interconnection of the circuit elements is simple and compact, and the real parts of its immittances are always positive. To verify its behavior, the equivalent circuit of two different leaky-wave antenna unit cells is extracted: a series-fed coupled patch radiating element, and the complementary strip-slot. Simulated and measured data are provided for the study cases, highlighting the satisfactory behavior of the equivalent circuit over a very broad bandwidth. A simple asymmetry model is also proposed that can be used advantageously in the analysis and design of non-symmetric two-ports, like unit cells of leaky-wave antennas.