Yes / This paper presented a new circular polarization reconfigurable antenna for 5G wireless communications. The antenna, containing a semicircular slot, was compact in size and had a good axial ratio and frequency response. Two PIN diode switches controlled the reconfiguration for both the right-hand and left-hand circular polarization. Reconfigurable orthogonal polarizations were achieved by changing the states of the two PIN diode switches, and the reflection coefficient |S11| was maintained, which is a strong benefit of this design. The proposed polarization-reconfigurable antenna was modeled using the Computer Simulation Technology (CST) software. It had a 3.4 GHz resonance frequency in both states of reconfiguration, with a good axial ratio below 1.8 dB, and good gain of 4.8 dBic for both modes of operation. The proposed microstrip antenna was fabricated on an FR-4 substrate with a loss tangent of 0.02, and relative dielectric constant of 4.3. The radiating layer had a maximum size of 18.3 18.3 mm2, with 50 W coaxial probe feeding. / European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Yes / In this paper, a novel dual-polarized highly-folded self-grounded Bowtie antenna that is excited through I-shaped slots is proposed for applications in sub-6GHz 5G multiple-input-multiple-output (MIMO) antenna systems. The antenna consists of two pairs of folded radiation petals whose base is embedded in a double layer of FR-4 substrate with a common ground-plane which is sandwiched between the two substrate layers. The ground-plane is defected with two I-shaped slots located under the radiation elements. Each pair of radiation elements are excited through a microstrip line on the top layer with RF signal that is 180° out of phase with respect to each other. The RF signal is coupled to the pair of feedlines on the top layer through the I-shaped slots from the two microstrip feedlines on the underside of the second substrate. The proposed feed mechanism gets rid of the otherwise bulky balun. The Bowtie antenna is a compact solution with dimensions of 32×32×33.8 mm3. Measured results have verified that the antenna operates over a frequency range of 3.1–5 GHz and exhibits an average gain and antenna efficiency in the vertical and horizontal polarizations of 7.5 dBi and 82.6%, respectively.

Yes / The world is experiencing an explosion in demand for ultra-high data rates with far greater expectations in the next few years. These expectations, given the bandwidth-demanding applications such as augmented and virtual reality and other beyond-5G applications, motivate the exploration of higher-frequency communication in the terahertz (THz) bands. However, THz communication is faced with many technical challenges, primarily due to the high susceptibility to blockages that limit its applications. Here, reconfigurable intelligent surfaces (RIS) provide alternative paths to circumvent such blockage effects and ensure reliable, spectral, and energy-efficient communication, thus advancing the THz-RIS technology concept. However, the ambitious targets of ubiquitous and global connectivity can only be satisfied by many technologies extending to multiple domains, from terrestrial networks to non-terrestrial network (NTN) domains. The use of airborne and spaceborne networks is considered a potential solution for addressing these challenges due to their dynamism, coverage, and ability to leverage their altitude for achieving line-of-sight communication for enhanced signal quality and network performance. Therefore, unmanned aerial vehicles, high-altitude platform stations, and satellites are poised to use flying THz-based RISs to improve air-to-ground and space-to-ground communication reliability while exploiting novel RIS architectures, techniques and enablers to address the issues regarding the propagation conditions, hardware limitations, network complexity and system performance. The aim in this paper is to present the discussion and a survey on the technical advances on THz-RIS NTNs, in addition to outlining potential applications, architectural variants, influencing properties, as well as its prospects, associated challenges, open issues and future directions towards high-data rate THz-RIS NTN communication for 6G and beyond. / This work was supported in part by the Universiti Kebangsaan Malaysia through Dana Impak Perdana 2.0 under Grant DIP-2022-020; and in part by the Engineering and Physical Sciences Research Council [grant number EP/Z001544/1] through the UK Research and Innovation (UKRI)-funded Marie Skłodowska-Curie Actions (MSCA) Postdoctoral Fellowship