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Mariya Antyufeyeva (V.N. Karazin Kharkiv National University, Ukraine)
| 15:30 | Millimetre wave lens antennas for 5G and beyond communication systems ABSTRACT. In order to increase the bandwidth of wireless communications, 5G and 6G communications are considering higher frequency bands than previous generations. With the increase of the frequency, the wavelength decreases, therefore, microwave components become smaller. This implies a need of higher resolutions in the manufacturing, which results also in higher costs. In addition, at higher frequencies, the path loss is higher, so a larger aperture is needed for the antennas to mitigate its effect. In this scenario, the use of quasi-optical systems is necessary to reduce the complexity of conventional antennas. One possible solution is lenses, which are able to transform the wave fronts of the feeding networks into directive beams at multiple or steerable directions. |
| 15:50 | Analysis and Design of Wideband Flat Lens Antennas Based on Artificial Dielectrics PRESENTER: Caspar Coco Martin ABSTRACT. This work describes the analysis and design of wideband flat lenses based on artificial dielectric layers. Planar lenses based on metasurfaces or resonant elements are typically narrowband, due to the phase wrapping over the period of 2π that is strongly frequency dependent. On the contrary, true-time-delay (TTD) planar lenses, which do not resort to phase discontinuities, can achieve large bandwidths. Here, artificial dielectric layers are employed to design wideband TTD lenses with low profile and low reflection. |
| 16:10 | Analysis and Design of Inhomogeneous Lenses for mmWave Radio Links PRESENTER: Matteo Albani ABSTRACT. Inhomogeneous dieletric materials can be nowadays easily manufactured thanks to latest technological advancements. The local dielectric permittivity can be tailored at each voxel by mixing various density materials or by leaving subwavelength holes or hollow parts. Therefore inhomogenuous lenses are becoming a promising solution for mmWave antenna system In standard homogeneous lenses rays follow straight trajectories and the design of such lenses consists on defining the geometry of the two interfaces. Instead, in inhomogeneous lenses, rays follow curved trajectories inside the lens because are smoothly and continuously bent by the refractive index gradient. Therefore, lens interface surfaces can even be simply flat, while a much larger number of degrees of freedom is available for the lens design, which involves the whole lens volume. In addition, since refraction is not needed at the interfaces, reflection can also be avoided by minimizing the impedance discontinuity along the ray paths. Geometrical Optics (GO) allows the description of the wave propagation phenomenon by determining ray trajectories locally orthogonal to the wave phase fronts, while the energy can be regarded as being transported along the ray paths. Since lenses are electrically large antennas, their numerical analysis with a full-wave method is very demanding, whereas high frequency ray methods can be both computationally efficient and accurate. Hence, the use of Geometrical Optics (GO) for inhomogeneous media finds its natural application in this class of problems. Such a methods is very fast and permits to trace rays across the lens along which the field is “transported” by using proper transport equations. However, the standard format of this scheme, available on textbooks, always hides a difficulty because it requires the knowledge of the ray divergence, which is not available in the single ray tracing. This impairment is resolved in various ways in the literature, typically resorting to the calculation of a ray bundle to predict the energy spread along the ray trajectory. In this paper instead we propose a novel approach by introducing a novel transport equation of the ray curvature matrix, whose trace is the ray divergence. Hence, the various differential equation along the ray (i.e., ray trajectory, local ray direction, local field, and local wavefront curvature) are all combined in a single first order vector differential equation which can be solved with a standard routine for Ordinary Differential Equation (ODE), thus predicting the field propagation. The above GO methodology for the description of the wave propagation through a lens can also be adopted to attack the inverse problem, i.e., the lens design. Indeed, the lens antenna is a device which must convert one impinging wave into a prescribed outgoing wave. Therefore, for a given feed and a target aperture distribution on the output interface, one can define a mapping between the input and the output interfaces which operates the desired transformation of wavefronts and amplitude distribution. Accordingly, a congruence of rays can be traced implementing such a mapping; indeed, the ray direction at any starting point on the input interface is dictated by the phase variation of the impinging wave, whereas the ray direction at the corresponding ray arrival point on the output interface provides the prescribed phase variation on the output interface. In addition, the ray density is adopted to modulate the aperture distribution power. Among the possible ray congruence implementing the desired transformation, minimum curvature ray trajectories can be chosen to minimize the refractive index variation in the lens. Finally, by resorting to a novel phase tracing algorithm, the GO wavefront phase function can be retrieved from the ray congruence and the map of the inhomogeneous refractive index inside the lens is obtained. This establishes a methodology to explicitly design any arbitrary lens antenna. |
| 16:30 | Fully metallic Mikaelian lens using holey glide symmetric metasurfaces PRESENTER: Zvonimir Sipus ABSTRACT. Periodic structures with higher symmetries have the potential to unlock many enhanced properties of microwave and mm-wave products and enable the development of novel components. In this paper, we propose the design of a planar fully metallic Mikaelian lens consisting of a parallel-plate waveguide (PPW) and coaxial holes with glide symmetry in lateral walls. |
| 17:20 | Angularly stable mm-wave polarising reflectors for broadband satellite systems in 6G PRESENTER: George Goussetis ABSTRACT. Periodic arrangement of electromagnetic scatterers are attracting increased attention for 6G systems e.g. as Metasurfaces or Intelligent Reflective Surfaces. They enable to manipulate the electromagnetic radiation in a way that ultimately optimises the end-to-end propagation characteristics. One class of such surfaces includes linear-to-circular reflection polarisers. By virtue of the scatterers geometry, reflection polarisers enable the conversion of a linearly incident wave to a circularly polarised reflected wave. This can bring significant benefits in e.g. links with Rician channel characteristics such as satellite links. In these systems, circular polarisation removes the requirement for polarisation alignment and hence improves the link performance in mobility scenarios. Despite aforementioned favourable characteristics, reflection polarisers suffer from unwanted angular dependence, i.e. the axial ratio of the reflected signal will vary for different angles of incidence of the incoming wave. Moreover, their implementation on doubly curved non-developable surfaces is technologically challenging. In this contribution we will present new findings relating to new reflection polariser designs that have improved angular stability. The presented design meet the requirements of emerging broadband satellite systems operating in the Ka-band, which are forecasted to play a central role in 6G. In these systems orthogonal circular polarisation is required at the up- and down-link bands. An implementation of such a polarising surface along a parabolic geometry will be presented, which in addition to polarisation conversion, also enables high level of beam collimation. Consequently, the proposed solution is suitable for broadband satellite systems operating in Ka-band. |
| 17:40 | Efficiency-Enhanced Wideband Ku-Band Array Antenna for CubeSat Links PRESENTER: George Goussetis ABSTRACT. CubeSats are an emerging solution for non-terrestrial networks for the small sizes and low weight, attracting intensive interest recently. The traditional uplink and downlink antennas are separately allocated on the same surface of a CubeSat. Due to the limited physical dimension, the gain of both links is suffering and leading to increased requirements for RF systems. Usually, an approach of shared aperture arrays could solve this problem by using the whole CubeSat surface for both links with doubled gain. However, the Ku downlink (10.7-12.75 GHz) and uplink (14-14.5GHz) bands are so close that a wide band array is preferable. Thus, we studied a planar array with a wide bandwidth covering both links, high efficiency and gain. |
| 18:00 | Electromagnetic and Thermal Analysis of Finned Heatsink Active mm-Wave Linear Array Antennas PRESENTER: Yanki Aslan ABSTRACT. The electromagnetic and thermal performance of the linear arrays of finned heatsink antenna elements are jointly studied for the first time, with a focus on the active integrated mm-wave phased array technology. An original element integrating a heatsink on top of a patch is designed at 28 GHz with significant improvements in directivity, bandwidth and radiation efficiency, as compared to a conventional low-cost patch antenna. A novel computational fluid dynamics (CFD) based thermal model is proposed for reliable natural convection simulations. The powerful ability of the heatsink antennas in enhancing passive cooling is demonstrated, which highlights their dual-functionality. |
| 18:20 | Dielectric Folded Reflectarray for 5G Applications PRESENTER: Andrea Massaccesi ABSTRACT. The next generation of wireless communication networks is called for offering and supporting services such as virtual and augmented reality, portable video streaming, Internet of Things, and on-move communication. These demands also affect the radiating sub-system, and many efforts are spent to face the challenge of designing innovative antenna configurations suitable for obtaining the required features. Among the different possible solutions, there are also those based on the use of Reflectarray (RA) [1, 2] technologies: they have been extensively studied to develop configurations showing features such as broad-band behaviour and beam-scanning capabilities. From the technological point of view, different solutions are considered, with the aim of improving the antenna performance and, at the same time, keeping as low as possible complexity and the manufacturing cost. For this reason, the design of metal-only [3] or a completely dielectric structure [4, 5] has been recently considered. Compared to the classical reflector antenna, a reflectarray has the advantage to provide shaped beams without increasing the mechanical complexity of the antenna by using a flat reflector. Several applications also require that the antenna is compact. For this purpose, a folder reflectarray can be used [6, 7]. It typically consists of a feed antenna, which radiates a linearly polarized field, a planar polarizing grid, and a planar reflectarray, which also acts as a “polarization-twist reflector.” With respect to a conventional reflectarray with the same focal ratio, a folded reflectarray presents a reduced thickness. In this contribution, folded reflectarray that makes use of a fully dielectric reradiating element and a plastic metalized polarizer is proposed. This solution allows low-cost manufacturing of the antenna using 3D printers in case of a moderate number of samples or a compression molding process for mass production. The adopted RA unit-cell consists of a dielectric resonator realized with a material characterized by a high value of the dielectric constant, to minimize the thickness, and low losses. Its shape is such to provide the desired phase shift between the incident and the reflected field and also to twist the field polarization of 90o. References [1] J. Huang, J.A. Encinar, Reflectarray Antennas, Hoboken, NJ: John Wiley & Sons, 2007. [2] P. Nayeri, F. Yang, A.Z. Elsherbeni, Reflectarray Antennas: Theory, Designs, and Applications, Hobo- ken, NJ: John Wiley & Sons, 2017. [3] K.Q. Henderson, N. Ghalichechian, “Circular- polarized metal-Only reflectarray with multi-slot elements”, IEEE Trans. Antennas Propag., vol. 68, 2020. [4] B. Li, et al., “A 3-D-printed wideband circularly polarized dielectric reflectarray of cross-shaped element,” IEEE Antennas Wirel. Propag. Lett., vol. 19, 2020. [5] A. Massaccesi, M. Beccaria, P. Pirinoli, “3D- printable perforated dielectric reflectarray in Ka-band,” Proc. 2019 IEEE Int. Symp. Antennas Propag., Atlanta, GA, USA, 2019. [6] D. Pilz and W. Menzel, “Folded reflectarray antenna,” Electronics Letters, vol. 34, no. 9, pp. 832–833, Apr. 1998. [7] A. Freni, A. Mazzinghi and G. Carluccio, "Folded Reflectarray With Spherical Polarizer," IEEE Transactions on Antennas and Propagation, vol. 68, no. 5, pp. 3613-3624, May 2020. |