Research Institute for Electromagnetic Materials

In this paper, the Laser Direct Structuring (LDS) process is used to fabricate a beam-switching modulated metasurface (MTS) antenna system with a 300 mm diameter, developed for Low Earth Orbit (LEO) satellite communications. The system operates in the Ka-band, centred at 31 GHz, offering high-performance communication capabilities. It comprises 48 elementary MTS antennas, each 40 mm in diameter, printed on LDS-compatible Liquid Crystal Polymer (LCP), suitable for injection molding. These elements are mounted on a 300 mm hemispherical Nylon PA12 support, fabricated using 3D Multijet printing. Each antenna element provides a gain between 14 and 20 dBi across the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$28-34.5 \text{GHz}$</tex> band. The complete system delivers a wide angular coverage of 120° in both azimuth and elevation, in transmit and receive modes.

In the context of the increasing global demand for renewable energy and the rapid development of large-scale photovoltaic (PV) power generation, efficient grid connection of PV energy has become crucial. However, existing grid-connected inverters (GCI) face issues such as high-power losses issue of inductive GCI (IGCI) or limited operating ranges issue of capacitive GCI (CGCI). This article introduces a multiple energy conversion channels fusion GCI (MC-FGCI) for large-scale PV power injection. First, MC-FGCI is proposed based on a new topology circuit configuration. Second, an equivalent circuit model of IGCI and CGCI is introduced to calculate the critical point for channel switching. The IGCI and CGCI efficient operating boundaries are determined based on the critical point. Third, based on the efficient operating boundaries, a finite state machine based method is proposed to choose the optimal VSI for high-efficiency grid connection. Finally, experimental results show that compared to previous multiple parallel IGCI (MP-IGCI), the proposed MC-FGCI saves around 11% power loss by eliminating the lossy dc/dc link. Compared to MP-CGCI, the proposed MC-FGCI expands the active power injection range under low maximum power point (MPP) voltage.

With respect to the transport properties of conduction electrons in liquid metals; two theories are available to explain electrical resistivity of liquid metals. In 1961, Ziman proposed “how the conduction electrons are scattered by ions” which is known as the Ziman theory. In 1962, Takeuchi and Endo proposed “how the fluctuation of ion’s assembly, in other words, the density fluctuation of component ions, affects to the scattering of conduction electrons.” The Ziman theory was widely accepted by many researchers, but Takeuchi-Endo theory was very limited. Are there appreciable differences between two theories?

Abstract Electro-optic modulators are pivotal to the advancement of photonic technologies, delivering faster, more efficient, and scalable solutions in optical communications, computing, and sensing. Their integration with existing photonic platforms, low-power operation, and high-frequency response is fundamental for current and future optical technologies. Silicon, compound semiconductors, thin‐film ferroelectrics, and organic polymers are widely used integrated electro-optic materials. However, standalone materials often exhibit inherent limitations in efficiency, optical loss, or response time. Hybrid integration emerges as a vital strategy to circumvent these fundamental constraints, synergizing complementary strengths to achieve modulator devices that satisfy stringent performance requirements. Here, we introduce a novel graphene-organic-silicon hybrid modulator that harnesses the unique properties of two-dimensional graphene materials as low-loss electrodes alongside the large electro-optic effects of organic materials, the high mode confinement of silicon slot waveguides, all seamlessly integrated within a silicon photonic device platform. The device capitalizes on the advantages of its constituent optical materials, delivering a highly efficient and compact phase modulator with a high efficiency of UπL~0.32 V⋅mm and a footprint of merely 25 μm, featuring low on‐chip losses of 0.86-2.6 dB and achieving data modulation speeds measured up to 144 Gbit s-1. By extending the frontiers of hybrid material integration, this work not only enhances modulator performance but also demonstrates the broader implications of advanced hybrid systems in advancing integrated photonic technologies.

Abstract The spatial distribution of electron density in the ionosphere exhibits notable variability and undergoes considerable changes during storms and substorms driven by solar wind disturbances. Electron density variations and irregularities can cause total signal blackouts during strong scintillation periods and enhance satellite positioning errors. We analyzed Global Navigation Satellite System (GNSS) - total electron content (TEC) and Arase satellite observation data to elucidate the characteristics of the electron density variation in the plasmasphere and ionosphere during the May 2024 super storm. To identify the electron density variation in the ionosphere, we calculated the ratio of the TEC difference (rTEC), which is defined as the difference from the 10-quiet-day average TEC normalized by the average value. Additionally, we estimated the electron density in the plasmasphere and inner magnetosphere from the upper frequency limit of the upper hybrid resonance (UHR) waves observed by the Arase satellite. Consequently, an L-t plot of the electron density showed that the plasmasphere contracted from L = 7.0 to L = 1.5 within 9 h after a sudden commencement. During the storm recovery phase, the plasmapause gradually shifted to a higher L-shell. The electron density in the plasmasphere recovered the geomagnetically quiet-time level on a 4-day scale. The timescale of the plasmaspheric refilling was much longer than that of other coronal mass ejection (CME)-driven storms during the Arase era. The rTEC in the Northern Hemisphere showed that an enhancement in the rTEC value occurred at high latitudes (60°–70° in magnetic latitude (MLAT)) in the daytime (10–14 in magnetic local time (MLT)), approximately 1 h after the storm onset. Subsequently, a tongue of ionization (TOI) formed in the polar cap owing to the enhancement of two-cell convection in the high-latitude ionosphere. The rTEC was globally depleted during the storm recovery phase. The depletion indicates the occurrence of a negative storm owing to a neutral composition (O/N 2 ) change driven by the energy input from the magnetosphere in the high-latitude thermosphere. The coincidence of the long refilling timescale of the plasmasphere and the depletion of the rTEC suggests that a strong negative storm impedes plasmaspheric refilling.

As wireless communication technologies progress towards higher data rates and improved connectivity, massive MIMO systems are becoming a crucial technology for achieving 5G and future communication standards. In conventional MIMO systems, increasing beam gain can be challenging due to limitations in antenna aperture and the number of channels. To address this issue, a digital multibeam forming array based on the ballistic simulation bifurcation algorithm to significantly enhance the beam gain of the system is proposed in this paper. The simulation results confirm that the digital multibeam forming array has significant potential for practical applications as an effective scheme for largescale MIMO implementation.

A circularly polarized magnetoelectric dipole antenna array with a parasitic loop is proposed in this paper. The innovative design combines a multi-patch structure with a parasitic loop element, utilizing a microstrip slot-coupled feeding mechanism. The parasitic loop introduces dual circularly polarized modes, achieving an axial ratio bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{4 5 \%}(\text{AR}&lt;\mathbf{3 ~ d B})$</tex> and an impedance bandwidth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$61 \%\left(\left\Vert S_{11}\right\Vert&lt;-10 ~\text{dB}\right)$</tex> for the single-element configuration. The developed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \times 2$</tex> array further improves performance, delivering a peak gain of 12.3 dBic while maintaining an impedance bandwidth 52 % and an axial ratio bandwidth of 42 %. Simulation results confirm stable circular polarization radiation patterns across the entire operational bandwidth.