The integration of Internet-of-Things (IoT) with sixth-generation (6G) wireless technology has recently been represented as a major advancement to achieve Internet-of-Everything (IoE). Different with traditional networks, 6G IoT is expected to use Unmanned-Aerial-Vehicle (UAV) for enhancing communication with ground-based users/devices. However, ensuring reliable communication between UAVs acting as aerial-base-stations (ABS) and ground users poses significant challenges, requiring innovative approaches for maintaining ubiquitous connectivity and robust deployment capabilities in complex environments. This paper presents a high-gain and wideband aerodynamic antenna with conical-beam (CB) radiation covering entire E-band spectrum for enhancing aerial-to-ground coverage of UAV-assisted 6G IoT networks. By simultaneously multi-exciting a grounded segmented dual-ring structure and architecting a multiple-stage circular-cavity-substrate-integrated-waveguide (CCSIW) feeding network, proposed antenna performs as a circular-array of complementary magnetoelectric radiating sources, resulting to an exceptional high-gain and wideband CB while still upholding a fully planar aerodynamic configuration. Numerical and experimental investigation revealed that proposed structure performs a 10-dB impedance bandwidth of 59.38–89.95 GHz (40.9%) with highly stable CB radiation across entire operating frequency and high peak gain of 12.1 dBi at 74.4 GHz; which surpass other state-of-the-art CB planar antennas and make it become a potential candidate for enhancing aerial-to-ground coverage for UAV-assisted 6G IoT networks.

Adaptive, functional, and reconfigurable devices that can manipulate incoming electromagnetic (EM) waves of arbitrary polarization into any desired output polarization are essential for advancing a wide range of Internet of Things (IoT)-related applications, including smart wireless communications, radar, imaging, and sensing systems. Achieving this functionality requires precise control over both the amplitude and phase of co-polarized and cross-polarized components—a task that presents significant challenges. In this work, we present a novel electrically Reconfigurable Intelligent Surface (RIS) capable of controlling all three fundamental EM wave properties: amplitude, phase, and polarization (encompassing both co- and cross-polarized components). The RIS leverages a field-programmable gate array (FPGA) to enable real-time, on-demand reconfiguration of its EM response. By employing far-field optimization techniques to determine the required amplitude and phase distributions for both polarization components, we demonstrate—through proof-of-principle applications—the RIS’s ability to dynamically steer beams, shape wavefronts, and arbitrarily transform polarization states. This advancement underscores the RIS’s potential as a transformative component for next-generation wireless systems, imaging technologies, and information processing applications, offering significant improvements in both performance and functionality across diverse fields.

A comprehensive review of 3-D/4-D-printed reconfigurable metasurfaces (RMSs) is presented in this article. A metasurface (MS) demonstrates exceptional abilities for electromagnetic (EM) wave molding beyond that offered by conventional planar interfaces, and RMS provides MS with more diverse EM wave-control capabilities. RMSs are categorized by the type of external stimulus used for reconfiguration, such as electrical RMS, fluidic RMS, mechanical RMS, and thermal RMS. To implement these RMSs, it is important to understand the design and fabrication requirements as well as the EM characteristic of each RMS, including its advantages and disadvantages. In particular, except for electrical RMS, RMSs require complex 3-D structures or special materials that are difficult to implement with conventional subtractive manufacturing methods such as printed-circuit-board manufacturing. Recently, advanced 3-D/4-D printing technology has achieved high fabrication freedom and meets the design and fabrication requirements of each type of RMS. In this article, we introduce representative RMSs with the development of 3-D/4-D printing technology and materials. Furthermore, current issues of RMSs based on 3-D/4-D printing technology and future directions are described.