In this work, two novel efficient leaky-wave antennas (LWAs) with stable radiation patterns operating in the 60-GHz band are proposed. The LWAs are implemented in groove-gap waveguide (GGW) technology. To mitigate the beam squint due to the dispersive nature of LWAs, complementary-dispersive prisms are coupled to the LWA radiation aperture. The antennas are implemented in fully-metallic purely holey periodic structures, resulting in a more cost-effective and robust manufacturing process compared to previously reported pin-based structures. Two prisms are proposed, one with mirror symmetry and one with glide symmetry. When the prism possesses a glide symmetry, much fewer holes are required while maintaining a similar performance, which even further decreases the fabrication costs. The complex propagation constant is optimized for low side lobe levels (SLLs) with tailored hole diameters and waveguide dimensions, thus for the first time demonstrating the capability of using glide-symmetric holes to control the leakage rate. Two prototypes with mirror-and glide-symmetric prisms are theoretically synthesized and validated by simulated and experimental results. A frequency bandwidth of 11% is achieved for both prototypes with the beam squint within ±0.9° (mirror) and ±1.7° (glide), SLLs below -15 dB (mirror) and -13 dB (glide), total efficiency almost 90%, and realized gain of 17 ± 0.5 dB at a fixed observing angle. The developed antennas are intended for mm-wave point-to-point communications.

A multilayer aperture antenna array in millimeter-wave band is presented in this communication. The antenna array is based on glide-symmetric holey gap-waveguide technology combined with E-plane insertion gaps for a low-cost and low-loss design. The radiating part of the antenna array is formed by an array of sixteen aperture antennas, grouped in four sets of 2x2 antenna subarrays in E-plane configuration. The 2×2 subarrays are fed by a one-to-four corporate feeding network in E-plane with holey gap-waveguide technology. The antenna array has been manufactured with high precision stereolithography (SLA) and subsequent metal plating. This design procedure yields a low-cost and low-weight manufacturing process for functional prototypes. The complete array has been manufactured and measured, comparing its performance with the simulation results. Measurements show an input reflection coefficient below -10 dB which ranges from 68 GHz to 74 GHz. The measured radiation patterns suit adequately the defined ones in the design stage. Moreover, gain above 19 dBi in the entire operating frequency band is achieved with a 74.1% mean antenna efficiency.

Geodesic lenses are a compelling alternative to traditional planar dielectric lens antennas, as they are low loss and can be manufactured with a simple mechanical design. However, a general approach for the design and analysis of more advanced geodesic lens antennas has been elusive, limiting the available tools to rotationally symmetric surfaces. In this paper, we present a fast and efficient implementation built on geometrical optics and scalar diffraction theory. A numerical calculation of the shortest ray path (geodesic) using an open-source library helps quantify the phase of the electric field in the lens aperture, while the amplitude is evaluated applying ray-tube power conservation theory. The Kirchhoff-Fresnel diffraction formula is then employed to compute the far-field of the lens antenna. This approach is validated by comparing the radiation patterns of a transversely compressed geodesic Luneburg lens (elliptical base instead of circular) with the ones computed using commercial full-wave simulators, demonstrating a substantial reduction in computational resources. The proposed method is then used in combination with an optimization procedure to study possible compact alternatives of the geodesic Luneburg lens with size reduction in both the transverse and vertical directions.

This paper presents a compact and low-loss V-band waveguide phase shifter based on glide-symmetric pin configuration. This kind of higher symmetry permits the control and improvement of the electromagnetic behavior or radiofrequency devices, as it is the case of the proposed phase shifter. The study of the dispersion diagram of the phase shifter unitary cell demonstrates that the pin configuration is a proper option for introducing a phase shift in a waveguide-based system. There is a significant increase in terms of phase shift when using a glide-symmetric pin distribution compared to its corresponding non-glide-symmetric configuration. Through this paper, the key geometrical parameters are also determined. The complete phase shifter is composed of an optimized cascade of tailored unitary cells so that the desired final phase shift value is achieved. A prototype has been manufactured in order to validate the theoretical approach through the comparison of phased shifters with both non-glide-symmetric and glide-symmetric configurations. The measurement results demonstrate the higher performance and compactness of the glide-symmetric phase shifter. For the same distance, the glide-symmetric version of the phase shifter provides more than 60% of phase shifting compared to the non-glide-symmetric phase shifter. Both phase shifters have a good impedance matching between 46 and 60 GHz and an insertion loss lower than 1 dB, thus clearly enabled as a 5G technology.

Many frequency-selective surface (FSS) structures are based on the use of a single periodic array of slot/apertures in a conducting sheet embedded in a layered medium. However, it is well known that stacking several conducting sheets and breaking the alignment of the stack can bring multiple benefits to the structure. In this article, the analysis and design of stacks of 2-D aperture arrays are carried out by exploiting as much as possible all the potential of a rigorous and systematic formulation based on the multimodal equivalent circuit approach (ECA). A key feature of the formulation is that linear transformations between the apertures of adjacent plates (rotation, translation, and scaling) can be dealt with from a purely analytical perspective. This fact is of potential interest for many practical applications, such as the design of polarization converters, absorbers, filters, and thin matching layers. When the apertures have an arbitrary geometry, it can be applied a hybrid approach that combines the ability of commercial simulators to handle arbitrary geometries with the fast computation times and physical insight of the ECA. In general, either the purely analytical or the hybrid approach can be applied in those many practical scenarios where the spatial profile of the electric field on the considered apertures hardly changes with frequency. As an additional feature of the approach, the dispersion properties (phase/attenuation constants and Bloch impedance) of infinite periodic stacks can be derived, and in particular, analytical expressions for the mirror- and glide-symmetric configurations are provided.

This paper presents an efficient equivalent circuit approach (ECA), based on a Floquet modal expansion, for the study of the co- and cross-polarization in frequency selective surfaces (FSS) formed by periodic arrays of patches/apertures in either single or stacked configurations. The ECA makes it possible the derivation of analytical expressions for the generalized scattering parameters associated with the proposed circuit networks. Furthermore, the proposed circuit approach is an efficient surrogate model that can be combined with optimization techniques and artificial intelligence algorithms for the efficient design of FSS structures, saving efforts in the computation compared to time-consuming full-wave simulators and tedious synthesis (simulation-assisted) techniques. Due to the simplicity of the topology of the involved networks, the ECA can also be advantageously used to gain physical insight. The proposed approach is applied and validated in different FSS configurations where the cross-pol component plays a fundamental role in the design, as in circular polarizers, polarization rotators, and reflectarray cells.