Unmanned aerial vehicles (UAVs) need high data rate connectivity, which is achievable through mm-waves and sub-THz bands. The proposed two-port leaky wave MIMO antenna, employing a coplanar proximity technique that combines capacitive and inductive loading, addresses this need. Featuring mesh-like slots and a vertical slot to mitigate open-stopband (OSB) issues, the antenna radiates broadside and bidirectionally. H-shaped slots on a strip enhance port isolation, and a coffee bean metasurface (MTS) boosts radiation efficiency and gain. Simulations and experiments considering various realistic scenarios, each at varying vertical and horizontal distances, show steered beam patterns, circular polarization (CP), and high-gain properties, with a maximum gain of 13.8 dBi, an axial ratio (AR) 9.98 dB, and an envelope correlation coefficient (ECC) <0.003. This design supports drones-to-ground (D2G), drone-to-drone (D2D), and drone-to-satellite (D2S) communications.

With their compact design and versatility, CubeSats have emerged as critical platforms for advancing space exploration and communication technologies. However, achieving reliable and efficient communication in the dynamic and constrained environment of low Earth orbit (LEO) remains a significant challenge. Beam-steering antenna systems offer a promising solution to address these limitations, enabling adaptive communication links with improved gain and coverage. This review article provides a comprehensive analysis of the state-of-the-art in CubeSat communication, concentrating on the latest developments in beam-steering antennas. By synthesizing the findings from recent studies, the key challenges are highlighted, including power constraints, miniaturization, and integration with CubeSat platforms. Furthermore, this paper investigates cutting-edge techniques, such as phased array systems, metasurface-based designs, and reconfigurable antennas, which pave the way for enhanced performance. This study can serve as a resource for researchers and engineers, offering insights into current trends and future opportunities for advancing CubeSat communications through innovative antenna systems.

In this study, at ultra-wideband (UWB) frequency band (3.1–10.6 GHz), we propose the use of compact 2:1 and 3:1 nonuniform transmission line Wilkinson power dividers (NTL WPDs) as feeding networks for simple 2 × 1 linear UWB Vivaldi tapered and nonuniform slot antenna (VTSA and VNSA) arrays. The 2:1 and 3:1 tapered transmission line (TTL) WPDs are designed and tested in this work as benchmarks for NTL WPDs. The VTSA array provides measured S₁₁ < −10.28 dB at 2.42–11.52 GHz, with a maximum gain of 8.61 dBi, which is 24.39% higher than the single element. Using the VNSA array, we achieve 52% compactness and 6.76% bandwidth enhancement, with good measured results of S₁₁ < −10.2 dB at 3.24–13 GHz and 15.11% improved gain (8.14 dBi) compared to the VNSA single element. The findings show that the NTL and Vivaldi nonuniform slot profile antenna (VNSPA) theories are successful at reducing the size of the UWB WPD and VTSA without sacrificing performance. They also emphasize the Vivaldi antenna’s compatibility with other circuits. These compact arrays are ideal for high-resolution medical applications like breast cancer detection (BCD) because of their high gain, wide bandwidth, directive stable radiation patterns, and low specific absorption rate (SAR). A simple BCD simulation scenario is addressed in this work. Detailed parametric studies are performed on the two arrays for impedance-matching enhancement. The computer simulation technology (CST) software is used for the simulation. Hardware measurement results prove the validity of the proposed arrays.

This paper introduces a novel miniaturized, four-mode, semi-flexible leaky wave Multiple-Input Multiple-Output (MIMO) antenna specifically designed to advance vehicular communication systems. The proposed antenna addresses key challenges in 5G low- and high-frequency bands, including millimeter-wave communication, by integrating innovative features such as a periodic Spoof Surface Plasmon Polariton Transmission Line (SSPP-TL) and logarithmic-spiral-like semi-circular strip patches parasitically fed via orthogonal ports. These design elements facilitate stable impedance matching and wide impedance bandwidths across operating bands, which is essential for vehicular networks. The hybrid combination of leaky wave and SSPP structures, along with a defected wide-slot ground structure and backside meander lines, enhances radiation characteristics by reducing back and bidirectional radiation. Additionally, a naturalization network incorporating chamfered-edge meander lines minimizes mutual coupling and introduces a fourth radiation mode at 80 GHz. Compact in size (14 × 12 × 0.25 mm³), the antenna achieves high-performance metrics, including S11 < −18.34 dB, dual-polarization, peak directive gains of 11.6 dBi (free space) and 14.6 dBi (on vehicles), isolation > 27 dB, Channel Capacity Loss (CCL) < 3, Envelope Correlation Coefficient (ECC) < 0.001, axial ratio < 2.25, and diversity gain (DG) > 9.85 dB. Extensive testing across various vehicular scenarios confirms the antenna’s robustness for Vehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P), and Vehicle-to-Infrastructure (V2I) communication. Its exceptional performance ensures seamless connectivity with mobile networks and enhances safety through Specific Absorption Rate (SAR) compliance. This compact, high-performance antenna is a transformative solution for connected and autonomous vehicles, addressing critical challenges in modern automotive communication networks and paving the way for reliable and efficient vehicular communication systems.

This paper presents a compact, high-performance metasurface-based leaky-wave MIMO antenna with dimensions of 40 × 30 mm², achieving a gain of 12.5 dBi and a radiation efficiency of 85%. The antenna enables precise control of electromagnetic waves, featuring a flower-like metasurface (MTS) with coffee bean-shaped arrays on substrates of varying permittivity, separated by a cavity layer to enhance coupling. Its dual-port MIMO design boosts data throughput operating in three bands (3.75–5.25 GHz, 6.4–15.4 GHz, and 22.5–30 GHz), while the leaky-wave mechanism supports frequency- or phase-dependent beamsteering without mechanical parts. Ideal for CubeSat communications, its compact size meets CubeSat constraints, and its high gain and efficiency ensure reliable long-distance communication with low power consumption, which is crucial for low Earth orbit operations. Circular polarization (CP) maintains signal integrity despite orientation changes, and MIMO capability supports high data rates for applications such as Earth observations or inter-satellite links. The beamsteering feature allows for dynamic tracking of ground stations or satellites, enhancing mission flexibility and reducing interference. This lightweight, efficient antenna addresses modern CubeSat challenges, providing a robust solution for advanced space communication systems with significant potential to enhance satellite connectivity and data transmission in complex space environments.

Breast cancer is one of the growing issues among women. Current ultrawideband (UWB) antennas utilized for Microwave Imaging (MI) present several limitations, such as resolution and penetration trade-offs, large dimensions of the antennas degrade patient comfort, and clutter in the received signal. To tackle these restrictions, this study presents the design, fabrication, and testing of ultra-compact Vivaldi antennas based on the new Vivaldi non-uniform slot profile antenna (VNSPA) theory. These antennas, with their significant slot length reductions of 50 % and 60 %, and circuit area reductions of 72.74 % (Antenna A) and 81.8 % (Antenna B), hold great promise for modern wireless communication and medical fields. Antenna A and B provide matching S₁₁ values of less than −11.36 dB and −10.21 dB and peak gains of 5.9 dBi and 6 dBi through 2.63–12.33 GHz and 3.16–14.34 GHz, respectively. Although Antenna B is 30.58 % smaller than Antenna A, it provides 13.24 % bandwidth (BW) with a 1.7 % gain enhancement, highlighting the significance of the exponential nonuniform slot profile (ENSP) shape on the antenna’s performance. Antenna B provides good Breast Cancer Detection (BCD) results through UWB MI. The simulation in this work, which is performed using computer simulation technology (CST) software, agrees well with the practical results to prove the antenna’s capabilities in detecting tumors in a breast. These results, like the directive stable radiation patterns and low specific absorption rate (SAR) values, ensure the proposed antennas are good candidates for modern wireless communication applications such as reader antennas in body area networks and high-resolution medical applications such as BCD.