Ali Noori Alnaqeeb

Lateral surface-wave coupling between branches of a corporate microstrip feeding network often limits the efficiency of millimetre-wave planar arrays. Current feed-network mitigations, such as substrate-integrated waveguides and printed ridge-gap waveguides, require complex multilayer stack-ups or altered line cross-sections. Conversely, radiator-side techniques like electromagnetic band gaps and parasitic stripes leave feed-network losses unaffected. To address this gap, we propose a feature-graded ground stripe that interacts directly with the feed network on a single metallic layer. By using grounded auxiliary stripes and plated metallic vias, this design creates a robust isolation barrier between feeding branches to drain laterally propagating surface-waves before they can recouple. We integrated this approach into an eight-element rectangular dielectric resonator antenna (DRA) array specifically tailored for the 3GPP n257 band. The resulting array delivers a -10 dB bandwidth spanning 25.77 to 28.83 GHz (fractional bandwidth of 11.2%). Furthermore, it achieves a peak realised gain of 18.6 dBi at 28.2 GHz alongside a total efficiency exceeding 90% between 27.0 and 28.5 GHz. Inter-branch isolation (S 23) is maintained below -33 dB across the operational band. Finally, experimental validation of a fabricated prototype shows that the measured reflection coefficient (S 11) confirms the design's practical viability.

Aperiodic element distributions can reduce reflectarray cost and weight by 35%, but they introduce two problems absent in periodic designs: (i) the required phases uniformly span the full 360◦, demanding wider S-curve coverage than a single-parameter element typically provides, and (ii) non-uniform inter-element spacing causes physical overlaps when variable-size patches are used. This paper addresses both problems through a proportionally notch-loaded rectangular patch element at 28 GHz. The element has a fixed width Wp = 2.5 mm, variable length Lp, and two symmetric notches of depth d n = 0.15Lp on the non-radiating edges, yielding 336◦ of phase range with 211◦ of independent fine tuning on 0.508 mm Rogers RO4003C substrate. Combined with a stealthy hyperuniform distribution on a 120 mm diameter circular aperture, the design achieves 19.7 dBi realised gain at 27 GHz with 287 elements, 0.2 dB above a 441-element periodic reference, while using 35% fewer elements and exhibiting 0.3 dB lower sidelobes. To the authors' knowledge, this is the first reflectarray to combine a proportional notch-loaded element with a hyperuniform distribution at millimetre-wave frequencies.

Ensuring robust and uniform network coverage is crucial for mobile network operators, particularly at the cell edges, where interference remains a persistent challenge. Traditional solutions such as network densification are complex, costly, and prone to increased interference. This paper presents the performance of recently proposed Cell-Sweeping base stations deployment in a typical 4G LTE network with Single User-Multiple Input Multiple Output (SU-MIMO) operation, use of higher-order modulation schemes, i.e. 256-Quadrature Amplitude Modulation (256-QAM), as well as using 3D antenna radiation patterns. By dynamically sweeping the antenna radiation patterns, cell-sweeping aims to significantly enhance the cell-edge performance while at the same time also harmonises the distribution of throughput in the whole cell. System-level simulations conducted using the 3rd Generation Partnership Project (3GPP) configurations reveal significant performance gain of cell-sweeping of up to 147% improvement in cell-edge throughput observed under open-loop spatial multiplexing, i.e. Transmission Mode 3 (TM3) in 3GPP LTE compared to conventional (i.e. non-cell sweeping) cellular network deployment. The results demonstrate that integrating cell-sweeping with advanced modulation and MIMO configurations is feasible and significantly improves Signal-to-Interference-plus-Noise Ratio (SINR), throughput, and Channel Quality Indicators (CQI) distribution, particularly in dense urban environments. These findings highlight the potential of cell-sweeping as an effective and simpler deployment strategy for future radio access networks.