On the Feasibility of Multi-Mode Antennas in UWB and IoT Applications below 10 GHz

While on the one hand 5G and B5G networks are challenged by ultra-high data rates in wideband applications like 100+ Gbps wireless Internet access, on the other hand they are expected to support reliable low-latency Internet of Things (IoT) applications with ultra-high connectivity. These conflicting challenges are addressed in a system proposal dealing with both extremes. In contrast to most recent publications, focus is on the frequency domain below 10~GHz. Towards this goal, multi-mode antenna technology is used and different realizations, offering up to eight uncorrelated ports per radiator element, are studied. Possible baseband architectures tailored to multi-mode antennas are discussed, enabling different options regarding precoding and beamforming

M4 : Multi-Mode-massiv-MIMO

In 2012 a group of researchers proposed a basic research initiative to the German Research Foundation (DFG) as a special priority project (SPP) with the name: Wireless 100 Gbps and beyond. The main goal of this initiative was the investigation of architectures, technologies and methods to go well beyond the state of the art. The target of 100 Gbps was set far away from the (at that time) achievable 1 Gbps such that it was not possible to achieve promising results just by tuning some parameters. We wanted to find breakthrough solutions. When we started the work on the proposal we discussed the challenges to be addressed in order to advancing the wireless communication speed significantly. Having the fundamental Shannon boundary in mind we discussed how to achieve the 100 Gbps speed.Angesichts der rapiden Entwicklung der Funkkommunikation hat die Deutsche Forschungsgemeinschaft im Jahr 2012 ein Schwerpunktprogramm mit dem Titel "Wireless 100 Gbps and beyound" (dt.: Drahtloskommunikation mit 100 Gbps und mehr) gestartet. Diese Initiative zielte auf neue Lösungen, Methoden und neues Wissen zur Lösung des Problems des kontinuierlichen Bedarfs an immer höheren Datenraten im Bereich der Funkkommunikation. Eine international besetze Jury hat etliche Projektvorschläge evaluiert, aus denen 11 Projekte ausgewählt und über zweimal 3 Jahre von Mitte 2013 bis Mitte 2019 gefördert wurden. Das vorliegende Buch versammelt die Ansätze, Architekturen und Erkenntnisse der Projekte. Es überspannt einen breiten Themenbereich, angefangen mit speziellen Fragen der physikalischen Übertragung, des Antennendesigns und der HF-Eingangs-Architekturen für unterschiedliche Frequenzbereiche bis 240 GHz. Darüber hinaus beschreibt das Buch Ansätze für Ultra-Hochgeschwindigkeits-Funksysteme, deren Basisbandverarbeitung, Kodierung sowie mögliche Umsetzungen. Nicht zuletzt wurden auch Fragen des Protokolldesigns behandelt, um eine enge Integration in moderne Computersysteme zu erleichtern

Benchmark problem definition and cross-validation for characteristic mode solvers

In October 2016, the Special Interest Group on Theory of Characteristic Modes (TCM) initiated a coordinated effort to perform benchmarking work for characteristic mode (CM) analysis. The primary purpose is to help improve the reliability and capability of existing CM solvers and to provide the means for validating future tools. Significant progress has already been made in this joint activity. In particular, this paper describes several benchmark problems that were defined and analyzes some results from the cross-validations of different CM solvers using these problems. The results show that despite differences in the implementation details, good agreement is observed in the calculated eigenvalues and eigencurrents across the solvers. Finally, it is concluded that future work should focus on understanding the impact of common parameters and output settings to further reduce variability in the results

Systematic analysis and design of multimode antennas based on symmetry properties of characteristic modes

This thesis deals with the systematic analysis and design of multimode antennas based on characteristic modes. A multimode antenna is a single physical antenna element with several independent antenna ports. The ports are intended to excite mutually orthogonal radiation patterns in order to provide pattern and polarization diversity. Therefore, the use of multimode antennas is a space-efficient alternative for multiple-input multiple-output (MIMO) systems compared to conventional antenna arrays with spatially distributed antenna elements. A systematic analysis and design of multimode antennas is enabled by means of the theory of characteristic modes. This is due to the fact that the characteristic modes of an arbitrary antenna object possess advantageous orthogonality properties. In particular, the modal radiation patterns are orthogonal to each other. Therefore, the ports of a multimode antenna should excite mutually exclusive sets of characteristic modes. This way, perfectly uncorrelated antenna ports are realized by exploiting the diversity potential of the characteristic modes. In order to selectively excite a certain set of characteristic modes, their characteristic surface current densities must be orthogonal to those of all other modes. This orthogonality property, however, is not guaranteed by the theory of characteristic modes. It is found, though, that the orthogonality of the characteristic surface current densities is governed by the symmetry of the antenna. This is due to the fundamental fact that the characteristic surface current densities are basis functions of the irreducible representations of the symmetry group of an antenna. Characteristic surface current densities belonging to different irreducible representations or belonging to different rows of a multi-dimensional irreducible representation are orthogonal to each other. The mutually orthogonal sets of characteristic surface current densities are thus found by assigning the characteristic modes to the irreducible representations of the symmetry group of a given antenna, which can be done automatically by means of the projection operator method. Consequently, the number of mutually orthogonal sets of characteristic surface current densities is governed by the finite number and dimensions of the irreducible representations and thus limited. These mutually exclusive sets of characteristic modes can be excited separately by antenna ports that fulfill the symmetry requirements of the irreducible representations. This means that a single antenna port consists of several feed points placed symmetrically on the antenna element. The input signals of the antenna ports are distributed to the feed points by means of a feed network. The optimal port configurations are governed solely by the symmetry of an antenna and are thus independent of the actual antenna shape and size. In other words, the optimal port configurations are known a priori and there is an upper bound for realizing orthogonal antenna ports. These optimal port configurations can be constructed automatically by means of the projection operator method. Further a priori knowledge is gained by exploiting relationships between different symmetry groups. Symmetry groups may be isomorphic or may be decomposed as direct-product groups, allowing to reuse or build upon the analysis of simpler symmetry groups. Additionally, related symmetry groups can be collected into families. The characteristic modes of the corresponding antenna geometries have similar properties in terms of both eigenvalues and characteristic surface current densities. Moreover, these properties can be estimated by means of a modal analysis of a generalized antenna geometry with an infinite symmetry group. These relationships are exploited in order to compare potentially suitable antenna geometries and estimate the minimum antenna size for realizing a desired number of orthogonal antenna ports. Based on this generalized modal analysis and the a priori knowledge gained from the symmetry analysis, a compact six-port multimode antenna based on a square geometry is designed. The feed points of the optimal port configurations are replaced by excitation slots in order to flexibly perform impedance matching. A feed network which distributes the port signals to the excitation slots with the correct amplitude and phase relations as required by the irreducible representations is realized in multilayer technology. Following a modular design approach, the antenna element and the feed network are first optimized separately and then assembled. The simulation and measurement results show that the six antenna ports are practically uncorrelated, offering the desired pattern and polarization diversity. With these results, the fabricated prototype demonstrates the practical feasibility and relevance of the presented design concepts