Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
To meet the application requirements of broadband radar systems for broadband power amplifiers, a Ku-band broadband power amplifier (PA) microwave monolithic integrated circuit (MMIC) based on a 0.15 μm gallium arsenide (GaAs) high-electron-mobility transistor (HEMT) technology is proposed in this paper. In this design, the advantages of the stacked FET structure in the broadband PA design are illustrated by theoretical derivation. The proposed PA uses a twostage amplifier structure and a two-way power synthesis structure to achieve high-power gain and high-power design, respectively. The fabricated power amplifier was tested under continuous wave conditions, and the test results showed a peak power of 30.8 dBm at 16 GHz. At 15 to 17.5 GHz, the output power was above 30 dBm with a PAE of more than 32%. The fractional bandwidth of the 3 dB output power was 30%. The chip area was 3.3 × 1.2 mm2 and included input and output test pads....
Metamaterial analysis for microwave frequencies is a common practice. However, adopting a multi-layered design is unique in the concept of miniaturisation, thus requiring extensive research for optimal performance. This study focuses on a multi-layered symmetric metamaterial design for C- and X-band applications. All simulation analyses were performed analytically using Computer Simulation Technology Studio Suite 2019. The performances of the proposed metamaterial design were analysed through several parametric studies. Based on the observation, the proposed metamaterial unit cell design manifested resonant frequencies at 7.63 GHz (C-band) and 9.56 GHz (X-band). Moreover, the analysis of effective medium parameters was also included in this study. High-Frequency Simulation 15.0 and Advanced Design System 2020 software validated the transmission coefficient results. Simultaneously, the proposed multi-layered metamaterial design with Rogers RO3006 substrate material exhibited a unique transmission coefficient using double, triple, and quadruple layers. The two resonant frequencies in the unit cell design were successfully increased to three in the double-layer structure at 6.34 GHz (C-band), 8.46 and 11.13 GHz (X-band). The proposed unit cell design was arranged in an array structure to analyse the performance changes in the transmission coefficient. Overall, the proposed metamaterial design accomplished the miniaturisation concept by arranging unit cells in a multi-layer structure and possesses unique properties such as a highly effective medium ratio and left-handed characteristics....
Kaolin clay is one of the essential components of utility and technical ceramic products. Drying is one of the stages of its production and is crucial for the quality of the obtained products. Due to the low energy efficiency of the dryers, it is also one of the most energy-intensive operations performed not only in the production of ceramics but in the industry as a whole. For this reason, modern drying techniques are sought. They are required to be energy efficient, sustainable and produce high-quality products. An example is the so-called hybrid drying, which combines several drying techniques (energy sources) into one process. The aim of this work was to determine the impact of microwave and infrared radiation on the kinetics and energy consumption of convective drying of kaolin clay and the quality of the products. The interaction of convective, microwave and infrared drying was investigated. Drying times, energy consumption and visual quality were compared for the tested processes. The fastest process was convection–microwave drying, where a reduction in drying time of 70% and energy consumption of 50% was observed. Unfortunately, intensive drying had a negative impact on the quality of the products (numerous cracks on the side surface). The best drying methods are those that use all energy sources simultaneously and periodically. Hybrid processes that use all energy sources in a periodic manner had the greatest efficiency. The drying time in these programs was shortened in relation solely to the convection process by 45 to 50% while reducing energy consumption by 3–18%. The product had the best quality....
Conformal multilayer micro-nanocrystalline diamond coatings were grown on substrates of a hard alloy with 9% Co with a high aspect number in microwave plasma from gas mixtures CH4/H2 and CH4/H2/N2. The substrates were of a cylindrical axial tool model with a size ratio: d = 12 mmto l = 75 mm. An original tool holder made of molybdenum, in the form of a sector of the excessive ring with the axis of the hole parallel to the central conductive platform, protects part of the substrate from heating due to the edge effect of plasma. The uniformity of heating of the growth part, which is located inside the excessive ring, is calculated using mathematical modeling and is provided by rotation at a speed of at least 12 rpm, which ensures the uniformity of the coating. The average grain size of the nanocrystalline film measured along the cylinder forming was 41 nm....
The robust development of electric vehicles has driven a surging decommission stream of lithium-ion batteries (LIBs) owing to their limited service life. The recycling of spent LIBs has become an urgent and essential task for the sustainable development of the LIB industry. However, the prevailing recycling methods focus only on recycling valuable metal, whilst the graphite anode materials are usually discarded or burned as fuels, leading to great waste of valuable carbon material. A facile strategy to obtain value-added products in an efficient manner is of great significance for the recycling of spent graphite. As graphite has excellent microwave absorption capability and electrical conductivity, microwave radiation on spent graphite can induce a Joule heat–discharge–plasma coupled effect, leading to a rapid heating process, especially when discharge occurs, exhibiting a thermal shock effect with the generation of a large number of high-energy electrons and active materials. This special feature facilitates microwave heating that is tailored for assisting the removal of impurities, structure repair, and graphite intercalation and exfoliation in an efficient manner. Therefore, different from the conventional graphite recycling route that is associated with energy/solution-intensive processes, this paper reviews the progress on microwave-assisted removal of impurities, repair of damaged graphite structure, and innovatively discusses the breakthroughs in microwave-assisted preparation of graphite intercalation compounds, expanded graphite, graphene and graphene-based materials, and porous graphene, with an aim to provide a scientific reference for the value-added resource utilization of spent graphite and preparation of new energy storage materials....
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