Antennas for future communication systems are required to be highly directive and steerable to compensate for the high path loss in the millimeter-wave band. In this work, we propose a linear array of modulated geodesic Luneburg lens (the so-called water drop lens) antennas operating at 56-62 GHz. The lens array antenna features two-dimensional beam scanning with low structural complexity. The lenses are fully metallic and implemented in parallel plate waveguides, meaning that they are highly efficient. Each lens is fed with 13 rectangular waveguides surrounded by glide-symmetric holes to suppress leakage. The lenses provide 110 degree beam coverage in the H-plane with scan losses below 1 dB. In order to scan in the E-plane, we use a feeding network based on a 1:4 power divider and three phase shifters. In this configuration, the array can scan 60 degrees in the E-plane, albeit with higher scanning losses than in the H-plane. The lens array is manufactured and a good agreement between simulated and experimental results is obtained.

In this letter, we propose and study a 2-D glide-symmetric dielectric periodic structure. We demonstrate that glide symmetry broadens the bandwidth of operation and achieves lower effective refractive indices when compared to non-glide configurations. These two properties are beneficial for producing graded-index lens antennas. To demonstrate the potential of the proposed unit cell, we designed a Luneburg lens operating in the K- and K $_\text {a}\!$ -bands. The lens was manufactured with conventional additive manufacturing and it has a potential use for future wireless communications given its low-cost and low-profile.

Antennas in emerging millimetre-wave applications are often required to have low losses and produce a steerable directive beam. These properties are achievable with fully-metallic geodesic Luneburg lens antennas. In this paper, we report the first experimental verification of a geodesic Luneburg lens antenna in V-band. The designed lens antenna is fed with 13 waveguides providing beam switching capability in a 110-degree range. The lens is implemented in parallel plate waveguide technology. The antenna is manufactured in two pieces, and a tolerance analysis indicates that gaps between the pieces can cause a severe performance degradation. Based on this tolerance analysis, two measures are taken to alleviate the manufacturing tolerances for the prototype. First, electromagnetic band gap structures are placed around the feeding waveguides. Second, the electrical contact between the two pieces is improved in critical regions. Two prototypes are manufactured, one without and one with the extra measures implemented. The measured radiation patterns of the prototype without these measures have high side lobes and low realized gain compared to the simulation. The measurements of the robust version of the prototype agree well with the simulations and demonstrates the applicability of geodesic Luneburg lens antennas for applications in V-band.

Fully metallic geodesic lens antennas are popular for millimetre-wave band applications due to their simplicity, robustness and low loss. Here, we report the experimental results of a geodesic lens array antenna, which was specifically designed to be additive-manufactured in one single piece using Laser Powder-Bed Fusion (LPBF). LPBF in aluminum alloy AlSi10Mg is able to produce high conductivity and relatively low surface roughness, so the antenna is highly directive and efficient. In addition, LPBF increases the robustness of the design since the lens array is monolithic, i.e., the risks associated to the assembly, including misalignments and undesired air gaps between pieces, are totally eliminated.

This paper applies an in-house generalized ray-tracing model to efficiently compute both the radiation pattern and the efficiency of geodesic lenses with non-rotationally symmetric shapes. Losses due to ohmic effects and surface roughness are included in the model. These losses are very relevant for monolithic geodesic lens antennas as postprocessing techniques cannot be applied to reduce the surface roughness of the internal part of the metallic plates. The model is validated by comparison with full-wave simulations for three different lenses: a circular flat parallel-plate waveguide, an elliptically-compressed geodesic lens, and a water-drop lens. These results show a reduction in computational time by a factor of 600 using the ray-tracing model. A non-rotationally symmetric water drop lens has been manufactured in a monolithic piece using the laser powder-bed fusion technique with successful experimental results.

The Physical Optics (PO) method is used to derive simplified expressions to compute the radiation electric fields of planar graded-index and geodesic lenses based on a parallel-plate waveguide (PPW) implementation. If the PO method is combined with ray-tracing (RT) techniques, the resulting RT-PO procedure is capable of computing radiation patterns and gain of the PPW-based lens antennas when their apertures have a general shape and the electric field is vertically polarized. The RT-PO method is validated by comparing it with the full-wave simulation results of the commercial software ANSYS HFSS for three application cases. The results show that the RT-PO approach is not only very efficient from a computational point of view but also accurate, thus being a very convenient analysis/design tool for this kind of antenna.