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In this paper, a lightweight spherical Luneburg lens with high performance is introduced for use in the frequency range 1 (FR1). The continuously varying refractive index profile of the lens is implemented using a quasi-isotropic partially metalized periodic structure. Much of the lens volume is made of foam, so the design is lightweight, making it applicable for low-band microwave frequency communication systems and, more specifically, 5G communications in FR1. The periodic structure allows a simple and low-cost layered construction with a quasi-isotropic response. This approach improves the scanning performance of the lens in all angular directions when compared to equivalent lens designs previously reported. Such a structure is an ideal candidate for high-gain multi-beam communication systems., Part of ISBN 978-88-31299-07-7QC 20230911

This paper focuses on the analysis of the dispersion diagram of a two-dimensional hexagonal periodic structure. The periodic inclusions are placed in a parallel plate waveguide environment and are circular holes located at the vertices of the hexagonal unit cells. The connection between the geometry of the periodic structure and the dispersion diagram is discussed. The wavevector information in the Brillouin zone is illustrated using the reciprocal lattice, from which the shape of the irreducible zone can be derived. The results give insight into the characteristics of the wave propagation characteristic of hexagonal units., Part of ISBN 978-88-31299-07-7QC 20230911

In this paper we present a lens antenna that can scan in the whole azimuthal plane. This is achieved by using two planar generalized Luneburg lenses that are connected through multiple 3 dB 90 degrees hybrid couplers. The antenna is designed for the 3GPP n260 band operating from 37 to 40 GHz making it suitable for indoor 5G coverage. Simulation results of the antenna are presented to illustrate that it can scan in the full azimuth plane., Part of ISBN 978-88-31299-07-7QC 20230911

In this contribution, we propose the use of the multimodal transfer matrix approach to investigate two-dimensional dielectric and magnetic periodic structures that possess glide symmetries. This method allows for the calculation of the attenuation constant in bandgaps, leaky structures, and material losses. In addition, this method enables a fundamental understanding of the operation of periodic structures. The method is also used to explain the differential response produced by dielectric/magnetic glide symmetries., Part of ISBN 978-88-31299-07-7QC 20230911

The linearized Multimodal Transfer-Matrix Approach (MMTMA) is a systematic hybrid solution to efficiently compute the dispersion analysis of two-/three-dimensional (2-/3-D) general periodic structures. This approach linearizes the nonlinear eigenvalue problem associated with 2-D/3-D periodic structures, avoiding the search for complex wavenumber solutions (both the phase and/or attenuation constants) in the complex plane. Here, MMTMA is explained and used for the Bloch analysis of a 2-D periodic leaky-wave antenna., Part of ISBN 978-88-31299-07-7QC 20230911

In this article, we propose an innovative concept to realize flexible and cost-effective array antenna systems for next generation communication systems. The idea is to tailor the performance of an antenna array to different use case scenarios by applying a customized dielectric lens placed in front of the array. By combining a lens with an array, we can improve certain performance properties of the antenna system and adapt it for unique site locations and requirements. Moreover, the lens may also act as a radome, providing mechanical protection from environmental conditions. This study consists of exploring the possibilities of using a lens to increase the gain of the antenna in certain directions: scanning range close to broadside (from 0 degrees to 30 degrees), and extreme scanning ranges (from 60 degrees to 80 degrees)., Part of ISBN 978-88-31299-07-7QC 20230911

We report a theoretical investigation on the possibilities and trade-offs when tapering a bi-directional fed leaky-wave antenna (LWA) to reduce the side lobes level, when operating with the two opposite antenna ports. It is demonstrated that, for high radiation efficiency designs, the directivity can be distorted due to low aperture illumination efficiency if the LWA is not symmetrically tapered with an adequate modulation function. The theory is corroborated with simulations of modulated LWAs in substrate integrated technology., Part of ISBN 978-88-31299-07-7QC 20230911

We present a dual-polarized lens antenna for point-to-multipoint communications at sub-THz. The lens is constructed by a doubly-curved parallel plate following a geodesic lens shape equivalent to the Luneburg index profile. The polarization is changed by metallic screens patterned with complementary split resonant rings (CSRRs). These screens are integrated in the radiation aperture of the lens. Two lenses are stacked up, one for each polarization. Each lens is fed by 11 waveguide ports, providing beam steering or multiple beams. The antenna is fully metallic and hence, highly efficient. In the operating band from 115 GHz to 125 GHz, the simulation shows a realized gain of 20 dBi with a maximum scan loss of 0.6 dB up to 60 degrees, a cross-polarization discrimination around 20 dB, and an insertion loss smaller than 1.5 dB., Part of ISBN 978-88-31299-07-7QC 20230911

A double-layer lens consists of a pair of rotationally symmetric index profiles or geodesic lens shapes connected by a reflecting mirror partially covering their common periphery. Such a lens can provide a focus in each layer, and a wave travelling between the foci explores both layers. Here, we concentrate on the case with one layer being homogeneous or flat, and derive a general solution for the lens profiles by solving a Luneburg-like inverse problem with pre-specified foci inside or outside the lens, and different background indices in two layers. We demonstrate four examples of interest in ray-tracing plots. These lenses may find application in communications, sensing, and imaging from millimeter waves up to the optical bands., Part of ISBN 978-88-31299-07-7QC 20230911

Here, we propose a generalized ray-tracing (RT) model to accurately compute the radiation patterns and radiation efficiency of lossy non-rotationally symmetric geodesic lens antennas. The RT model uses geometrical optics to obtain the ray paths from the source to the aperture, ray tube theory to calculate the field amplitude distribution, and Kirchhoff's diffraction formula to compute the radiation pattern. Losses in geodesic lenses are mainly produced by the finite conductivity and roughness of the metallic plates. These losses are added to the calculation of the radiation pattern to estimate the radiation efficiency of the antenna. To demonstrate the accuracy of the proposed RT model, a geodesic half-Maxwell fish-eye lens is designed. Radiation patterns, scan losses, and radiation efficiency are calculated. These results agree well with those computed by full-wave simulations., Part of ISBN 978-88-31299-07-7QC 20230911

We discuss forward and backward modes in one-dimensional (1-D) periodic bounded structures. First, it is shown that the conventional definition of the phase speed can incorrectly identify the forward/backward nature of modes. Therefore, we propose an alternative definition of the phase speed for modes in bounded periodic structures and demonstrate that this definition correctly identifies the nature of modes in a 1-D periodic corrugated parallel plate waveguide. The proposed phase speed is analyzed through simulations with commercial software and a circuit model., Part of ISBN 978-88-31299-07-7QC 20230911