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Polyacrylonitrile (PAN)-based and pitch-based carbon fibers exhibit significant anisotropies in the radial and axial directions. Characterizing the anisotropy of the elastic properties of PAN-based and pitch-based carbon fibers is important for carbon fiber research communities. In this present study, the Raman scattering for anisotropy of PAN-based and pitch-based carbon fiber-reinforced plastic (CFRP) samples was investigated. The Raman scattering parameters and ratios in the CFRPs with 0°, 45°, and 90° sections are related to the tensile modulus. These linear trends for the PAN-based and pitch-based CFRPs with 0°, 45°, and 90° sections intersect in the range of 400–700 GPa. The change in Raman scattering parameters and ratios of PAN-based and pitch-based carbon fibers and CFRPs with a 0° section are related to the tensile modulus. These linear trends also intersect in the range of 400–700 GPa. The intensity ratios increased with increase in the angle for each CFRPs. The intensity ratio in an arbitrary angle could be estimated using the rule of mixtures and coordinate transformation equations. The Raman anisotropic nature of PAN-based and pitch-based fibers are identified experimentally and analytically.

A consistent study of the solar wind has been extended to a wide region of interplanetary space, up to distances from the Sun R ⩾ 90 R s . Experiments are carried out with the radio telescopes of the Pushchino Radio Astronomy Observatory (Astrospace Center, Lebedev physical Institute, Russian Academy of Sciences): DKR-1000 ( λ ≈ 2.7–2.9 m) and RT-22 ( λ ≈ 1.35 cm), respectively. The radio-wave scattering characteristics, the scattering angle θ ( R ) and the scintillation index m ( R ), are studied. The formation of a steady supersonic solar wind is associated with a sequence of four stages whose scale in different solar wind streams changes within the range 10–23 R s , depending on the initial stream speed. These circumstances should be taken into account when predicting the state of the near space using data on the solar wind in regions of the interplanetary medium close to the Sun.

As an important characteristic of a signal transmission network, scattering parameters can accurately reflect the signal transmission situation. By establishing a circuit model based on scattering parameters for the signal path unit, studying the signal attenuation and reflection curves of components including transmission lines, transmission media, vias, high-speed connectors, and transceiver termination devices, a circuit simulation model completely based on scattering parameters is proposed. This model can be parametrically adjusted according to the requirements of actual circuit implementation, and accurately reflect the high-speed signal transmission quality of the final circuit. This circuit simulation model is applied to the high-speed 5G small base station system. The transceiver performance of the modular circuit model completely based on scattering parameters and the scattering parameter model extracted based on board-level implementation is compared. The results show that the modular circuit completely based on scattering parameters can accurately match the channel communication indicators of board-level implementation.

This paper examines the effect of finger fat pad thickness on the accuracy performance of complementary split-ring resonator (CSRR)-based microwave sensors for non-invasive blood glucose level detection. For this purpose, a simplified four-layer Cole–Cole model along with a CSRR-based microwave sensor have been comprehensively analyzed and validated through experimentation. Computed scattering parameter (S-parameter) responses to different fat layer thicknesses are employed to verify the concordance of the studied model with the measurement results. In this respect, a figure of merit (FM) based on the normalized squared difference is introduced to assess the accuracy of the considered Cole–Cole model. We have demonstrated that the analyzed model agrees closely with the experimental validation. In fact, the maximum error difference for all five fingertips does not exceed 1.73 dB over the entire frequency range of interest, from 1 GHz to 4 GHz.

The heuristic homogenization approach is intensively employed to characterize electromagnetic metamaterials (MMs). The effective parameters are extracted within this framework using the Nicolson–Ross–Weir (NRW) method. Special attention must be devoted to handling this procedure because of the branch ambiguity issue affecting it, i.e., the lack of uniqueness in the evaluation of the effective refractive index neff rooted in the use of the multivalued complex logarithm to invert the Airy–Fresnel relation. Over the years, several techniques based on the phase-unwrapping approach have been introduced, but without any theoretical justification. In this paper, we aim to clarify the theoretical connection between the phase unwrapping method and the analytic continuation theory framework. Furthermore, three-phase-unwrapping approaches, which descend directly from the theory we discussed, are compared to identify which approach is best suited to reconstruct the complex refractive index of metamaterials when the NRW method is applicable.

The most commonly used cables in device-to-device communication, such as USB, HDMI, DP, or PCI-e cables, as well as the MCIO cables currently used in artificial intelligence (AI) servers, has a differential Twinax configuration. The use of differential transmission aims to mitigate the impact of external interference. The Twinax structure consisted of a twin-core cable with an outer copper foil shielding. Achieving perfect symmetry in the Twinax cable is a challenge. This work investigated whether the asymmetrical structure and material impacted the production yield rate. The focus was on the mixed-mode analysis of the asymmetric Twinax cable. By utilizing mixed-mode S-parameters, we aimed to determine whether the cable designs met industry standards and complied with data rate requirements. Due to intense market competition and short development cycles, 3D full-wave simulations were time-consuming because of the high mesh count. Moreover, modeling was challenging because the center of each segment of an actual cable underwent slight variations. To expedite the design process, a method was developed to extract Twinax cable RLGC (Resistance, Inductance, Conductance, Capacitance) parameters, calculate mixed-mode S-parameters, and perform analysis and evaluations. Our approach not only enables efficient signal quality assessment across cables of varying lengths by simply connecting each small segment to account for continuous manufacturing variations but also significantly reduces product development time to under one hour. Furthermore, this work investigated the impact of common manufacturing imperfections, ensuring robust and reliable designs for real-world applications.

Potential applications of microwave energy, a developed form of clean energy, are diverse and extensive. To expand the applications of microwave heating in the metallurgical field, it is essential to obtain the permittivity of ores throughout the heating process. This paper presents the design of a 2.45 GHz ridge waveguide apparatus based on the transmission/reflection method to measure permittivity, which constitutes a system capable of measuring the complex relative permittivity of the material under test with a wide temperature range from room temperature up to 1100 °C. The experimental results indicate that the system is capable of performing rapid measurements during the heating process. Furthermore, the system is capable of accurately measuring dielectric properties when the real part of the permittivity and the loss tangent vary widely. This measurement system is suitable for high-temperature dielectric property measurements and has potential applications in microwave-assisted metallurgy.

We present the broadband transmission-reflection meniscus-removal method for liquid characterization in a semi-open rectangular waveguide. The algorithm utilizes 2-port scattering parameters measured with a calibrated vector network analyzer for three states of the measurement cell: empty and filled with two liquid levels. The method enables the mathematical de-embedding of a symmetrical sample of a liquid, not distorted with a meniscus, and provision of its permittivity and permeability, as well as its height. We validate the method for propan-2-ol (IPA), a 50% aqueous solution of IPA, and distilled water in the Q-band (33–50 GHz). We investigate typical problems for in-waveguide measurements, such as phase ambiguity.

Stretchable materials are widely used for the realization of various sensors, but their radio frequency behavior has not been fully characterized so far. Here, an innovative method is proposed for deriving the surface impedance of this kind of materials. The material characterization represents a fundamental step for exploiting the material as a sensing element within a radio frequency device. Indeed, the proposed method is capable of retrieving the surface impedance of the material while it is being stretched, thus deriving a correspondent calibration curve. The characterization approach is based on a contactless measurement of the scattering parameters using waveguides. By exploiting the measured scattering parameters, the variation in the surface impedance as a function of both frequency and strain is recovered through an analytical inversion procedure. Numerical simulations were initially performed trough a numerical electromagnetic simulator, and subsequently, experimental validation was carried out using a dedicated test bench designed to ensure a contactless measurement of the stretchable material.

This paper gives an overview of optimizing wireless power transfer systems using magnetic coupling. Optimization aims to maximize either the power transfer efficiency or the transferred power. The resulting load calculation and matching strategies are revisited. Moreover, the coupling system is described, starting with its equivalent circuit and scattering parameters. In addition to wireless power transfer, communication in RFID and NFC systems and its frequency characteristics and bandwidth issues are highlighted. The focus in this paper is on load modulation for data transfer between a tag and reader. For this purpose, subcarrier voltages are derived using time-domain as well as frequency-domain signal analysis.