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Space-fed large antenna arrays offer superior efficiency, simplicity, and reductions in size, weight, power, and cost (SWaP-C) compared to constrained-feed systems. Historically, horn antennas have been used for space feeding, but they…

Signal Processing · Electrical Eng. & Systems 2025-05-15 Krishan Kumar Tiwari , Thomas Flisgen , Wolfgang Heinrich , Giuseppe Caire

We present a novel, power and hardware efficient, antenna system leveraging the eigenmodes of the over-the-air propagation matrix from an active multi-antenna feeder (AMAF) to a large reflective intelligent surface (RIS), both configured as…

Signal Processing · Electrical Eng. & Systems 2023-10-26 Krishan K. Tiwari , Giuseppe Caire

Flat-top beam designs are essential for uniform power distribution over a wide angular sector for applications such as 5G/6G networks, beaconing, satellite communications, radar systems, etc. Low sidelobe levels with steep transitions allow…

Signal Processing · Electrical Eng. & Systems 2025-10-02 Krishan Kumar Tiwari , Giuseppe Caire

We present a novel, power- & hardware-efficient, multiuser, multibeam RIS (Reflective Intelligent Surface) architecture for multiuser MIMO, especially for very high frequency bands (e.g., high mmWave and sub-THz), where channels are…

Signal Processing · Electrical Eng. & Systems 2025-07-22 Krishan Kumar Tiwari , Giuseppe Caire

Wireless communication systems have almost exclusively operated in the far-field of antennas and antenna arrays, which is conventionally characterized by having propagation distances beyond the Fraunhofer distance. This is natural since the…

Information Theory · Computer Science 2021-12-09 Emil Björnson , Özlem Tugfe Demir , Luca Sanguinetti

We propose a power- and hardware-efficient, pragmatic, modular, multiuser/multibeam array-fed RIS architecture particularly suited to operate in very high frequency bands (high mmWave and sub-THz), where channels are typically sparse in the…

Signal Processing · Electrical Eng. & Systems 2024-10-10 Krishan Kumar Tiwari , Giuseppe Caire

In this paper, we propose to investigate a single RF chain multi-antenna full-duplex (FD) relay built with $b$-bit analog phase shifters and passive self-interference cancellation. Next, assuming only passive self-interference cancellation…

Information Theory · Computer Science 2023-09-14 Armin Bazrafkan , Marija Poposka , Zoran Hadzi-Velkov , Petar Popovski , Nikola Zlatanov

A novel architecture of the center-fed pinching antenna system (C-PASS) is proposed. In contrast to the conventional end-fed PASS, signals are fed from the center input ports and propagate towards both sides of the waveguide. By doing so,…

Information Theory · Computer Science 2025-12-16 Xu Gan , Yuanwei Liu

In conventional inductive wireless power devices, the energy is transferred via only reactive near fields, which is equivalent to non-radiative F\"orster energy transfer in optics. Radiation from transmitting and receiving coils is usually…

Applied Physics · Physics 2023-02-07 N. Ha-Van , C. R. Simovski , F. S. Cuesta , P. Jayathurathnage , S. A. Tretyakov

This paper addresses a drawback of massive multiple-input multiple-output Maximum Ratio Transmission beamforming. In some propagation conditions, when the base station serves the same target user equipment for a long period, it reduces the…

Signal Processing · Electrical Eng. & Systems 2022-06-16 Nour Awarkeh , Dinh-Thuy Phan-Huy , Raphael Visoz , Marco Di Renzo

In this paper, we consider a multi-pair two-way amplify-and-forward relaying system where multiple sources exchange information via a relay node equipped with large-scale antenna arrays. Given that channel estimation is non-ideal, and that…

Information Theory · Computer Science 2016-05-26 Yongyu Dai , Xiaodai Dong

The reconfigurable intelligent surface (RIS) is a promising technology to provide smart radio environment. In contrast to the well-studied patch-array-based RISs, this work focuses on the metasurface-based RISs and simultaneously…

Signal Processing · Electrical Eng. & Systems 2023-03-08 Jiaqi Xu , Xidong Mu , Yuanwei Liu

Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including…

Instrumentation and Methods for Astrophysics · Physics 2015-05-14 Jonathan Landon , Michael Elmer , Jacob Waldron , David Jones , Alan Stemmons , Brian D. Jeffs , Karl F. Warnick , J. Richard Fisher , Roger D. Norrod

Multiplicative fading is a major limitation of reconfigurable intelligent surfaces (RIS), restricting their effective coverage in both existing sub-6GHz systems and future mmWave networks. Although active RIS architectures mitigate this…

Information Theory · Computer Science 2025-12-30 Aparna V C , Shashank Shekhar , Sheetal Kalyani

This paper investigates a modular beamforming framework for reconfigurable intelligent surface (RIS)-aided multi-user (MU) communications in the near-field regime, built upon a novel antenna architecture integrating an active multi-antenna…

Signal Processing · Electrical Eng. & Systems 2025-08-13 Giulia Torcolacci , Malte Schellmann , Davide Dardari

Modern MIMO communication systems are almost exclusively designed under the assumption of locally plane wavefronts over antenna arrays. This is known as the far-field approximation and is soundly justified at sub-6-GHz frequencies at most…

Information Theory · Computer Science 2023-02-28 Giacomo Bacci , Luca Sanguinetti , Emil Björnson

Flexible antenna arrays (FAAs), distinguished by their rotatable, bendable, and foldable properties, are extensively employed in flexible radio systems to achieve customized radiation patterns. This paper aims to illustrate that FAAs,…

Signal Processing · Electrical Eng. & Systems 2025-04-01 Songjie Yang , Jiancheng An , Yue Xiu , Wanting Lyu , Boyu Ning , Zhongpei Zhang , Merouane Debbah , Chau Yuen

The emerging reflecting intelligent surface (RIS) technology promises to enhance the capacity of wireless communication systems via passive reflect beamforming. However, the product path loss limits its performance gains. Fully-connected…

Information Theory · Computer Science 2025-03-26 Konstantinos Ntougias , Symeon Chatzinotas , Ioannis Krikidis

We consider a two-way half-duplex relaying system where multiple pairs of single antenna users exchange information assisted by a multi-antenna relay. Taking into account the practical constraint of imperfect channel estimation, we study…

Information Theory · Computer Science 2016-07-07 Chuili Kong , Caijun Zhong , Michail Matthaiou , Emil Björnson , Zhaoyang Zhang

Distributed Antenna Systems (DASs) employ multiple antenna arrays in remote radio units to achieve highly directional transmission and provide great coverage performance for future-generation networks. However, the utilization of active…

Information Theory · Computer Science 2023-09-26 Chengzhi Ma , Xi Yang , Jintao Wang , Guanghua Yang , Wei Zhang , Shaodan Ma
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