Wideband Reflectarrays for 5G/6G: A Survey

Theoharis, Panagiotis Ioannis; Raad, Raad; Tubbal, Faisel; Khan, Muhammad Usman Ali; Jamalipour, Abbas

doi:10.1109/ojap.2022.3195665

“…Our architecture is in line with [3, Figure 1 (e)] and with [4]. This can also be seen as a reconfigurable reflectarray [5] where the horn feeder is replaced by the AMAF. The main difference between our present work and [3], [4] is that these works consider a rich scattering channel (which must be estimated) between the RIS elements and the users and some form of digital baseband processing.…”

Section: Introductionsupporting

confidence: 57%

“…where A is the set of all eigenmode-based designs. Note that since the columns of V forms a unitary basis for C Na , there is no loss of generality to represent the AMAF BF vector b in the form (5). Also, the corresponding excitation vector Na i=1 σ i β i u i over the RIS elements is any vector in the linear subspace T = Span(T) = Span(u 1 , .…”

Section: Eigenmode-based Designsmentioning

confidence: 99%

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RIS-Based Steerable Beamforming Antenna with Near-Field Eigenmode Feeder

Tiwari¹,

Caire²

2023

Preprint

0

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<p>We present a novel, power and hardware efficient, ``reconfigurable'' antenna system leveraging the eigenmodes of the over-the-air propagation matrix T from an active multi-antenna feeder (AMAF) placed in the near-field of a large reflective intelligent surface (RIS) to the RIS. We consider directive antenna elements with finite non-zero aperture constituting the two standard linear arrays (SLAs) - the AMAF and the RIS. We demonstrate the flexibility of the proposed architecture by showing that it is capable of generating radiation patterns for multiple applications such as very narrow beams with low side lobes for space-division multiple access communications, wide-angle beams for short range automotive sensing and sectorial beaconing, and monopulse patterns for radar angular tracking. A key parameter in our design is the AMAF-RIS distance which must be optimized and it is generally much less than the Rayleigh distance. Active RF amplification is done at the AMAF only with almost no signal splitting unlike conventional RF beamforming for massive MIMO systems in millimeter-wave (mmWave) and sub-teraHertz (sub-THz) bands. For a given AMAF aperture, the optimal AMAF-RIS distance increases as a function of the RIS size. The AMAF-RIS loss is compensated almost exactly by the larger aperture gain of the RIS leading to almost constant RIS gain with increasing RIS sizes. This allows to choose different beam angular selectivities with the same center beam gain.</p>

show abstract

“…Note that array fed near field RIS hardware are already being developed and tested, e.g., [4]. This can also be seen as a reconfigurable reflectarray [5] where the horn feeder is replaced by the AMAF. Note that while the AMAF is in the near field of the RIS, the individual antenna elements of the AMAF and the RIS are in far fields of each other.…”

Section: Introductionmentioning

confidence: 99%

RIS-Based Steerable Beamforming Antenna with Near-Field Eigenmode Feeder

Tiwari¹,

Caire²

2022

Preprint

0

View full text Add to dashboard Cite

<p>We present a novel, power and hardware efficient, ``reconfigurable'' antenna system leveraging the eigenmodes of the over-the-air propagation matrix T from an active multi-antenna feeder (AMAF) placed in the near-field of a large reflective intelligent surface (RIS) to the RIS. We consider directive antenna elements with finite non-zero aperture constituting the two standard linear arrays (SLAs) - the AMAF and the RIS. We demonstrate the flexibility of the proposed architecture by showing that it is capable of generating radiation patterns for multiple applications such as very narrow beams with low side lobes for space-division multiple access communications, wide-angle beams for short range automotive sensing and sectorial beaconing, and monopulse patterns for radar angular tracking. A key parameter in our design is the AMAF-RIS distance which must be optimized and it is generally much less than the Rayleigh distance. Active RF amplification is done at the AMAF only with almost no signal splitting unlike conventional RF beamforming for massive MIMO systems in millimeter-wave (mmWave) and sub-teraHertz (sub-THz) bands. For a given AMAF aperture, the optimal AMAF-RIS distance increases as a function of the RIS size. The AMAF-RIS loss is compensated almost exactly by the larger aperture gain of the RIS leading to almost constant RIS gain with increasing RIS sizes. This allows to choose different beam angular selectivities with the same center beam gain.</p>

show abstract

“…This is evidenced by our authors' and readers' growing interest as reflected in the number of submissions, that exceeded 630 (until August 2022), and in more than 278,000 article views and downloads (until July 2022). The journal has published 262 articles, including thirteen review articles [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], an expanding cluster of articles with shared data and code [12], [16], [17], [18] along with fifteen topical article collections [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33] and a special article collection spotlighting research published by female researchers [34]. It is noteworthy that, based on data gathered until July 2022, OJAP has been ranked second among all IEEE gold open access journals in terms of article usage (Figure 1).…”

mentioning

confidence: 99%