Microwave Transmission Properties Research Articles

Real-time microwave transmittance variation of glass fiber composites subjected to laser irradiation

Laser irradiation may have a significant impact on the microwave transmission properties of glass fiber composites. In this study, a two-dimensional microwave transmission transient model of glass fiber composites during the complete laser irradiation process was developed. The numerical results indicate that carbonization during irradiation causes a significant increase in dielectric loss, thus resulting in a decrease in transmittance. After irradiation, the dielectric loss decreased due to the decrease in temperature, which, in turn, led to an increase in transmittance. The increased transmittance after cooling was lower than the original value due to the generation of pyrolytic carbon with a high dielectric loss. The numerical results were verified by conducting an experiment wherein the microwave transmittance of glass fiber composites was measured in real time before, during, and after laser irradiation. In addition, the effects of different laser parameters on the real-time microwave transmittance during laser irradiation were investigated experimentally and numerically. For the same total energy, a laser with a high power density and short irradiation time had a more significant effect on the attenuation of transmittance.

Extrinsic magnetised plasma kolakoski quasicrystal

This manuscript explores the microwave transmission properties of multilayer structures that employ the Kolakoski sequence. The structures, composed of alternating layers of extrinsic magnetized plasma, are analysed under normal incidence conditions, with a focus on various parameters such as frequency, external magnetic field intensity, and electron density. At frequencies higher than the plasma frequency, consistent bandgaps are observed across different layer counts, indicating strong transmission characteristics. Conversely, at frequencies lower than the plasma frequency, the thickness of the bandgap fluctuates due to the inherent nature of the Kolakoski sequence, suggesting potential applications in multi-channel filtering. The study demonstrates the ability to adjust the significant bandgap above the plasma frequency through manipulation of the external magnetic field. By increasing the strength of the magnetic field, the bandgap undergoes a shift and narrows, highlighting the tunability of the transmission properties. On the other hand, increasing the number of layers widens the bandgap below the plasma frequency, resulting in the emergence of narrow transmission peaks. Moreover, the influence of electron density on the transmission spectra is examined, showing that higher electron density leads to wider bandgaps, although with minimal frequency shifts. The intricate interplay between structural parameters, external factors, and transmission characteristics provides valuable insights for optimizing multi-channel microwave reflectors and related devices.

Control of magnon–photon coupling by a direct current in a Py/Pt-superconducting cavity hybrid system

In this work, using a Permalloy film and a superconducting cavity, we highlight the unique dispersion in the microwave transmission properties of the magnon–photon coupled system in the Purcell regime, in which the modulation of the coupled system can be achieved by varying the magnon dissipation rate. It is demonstrated that decreasing the magnon dissipation rate can lead to an enhancement in magnon–photon coupling. By applying a direct current into the Permalloy/platinum bilayer, we achieve modulation of the coupling in the Purcell regime. The magnon–photon coupling is enhanced with the increasing current, which is related to the decrease in the magnon dissipation rate due to the thermal effect of the current. In addition, we establish an approach to obtain the coupling strength from the coupled microwave photon dispersion and linewidth. The electrical control of the Permalloy-superconducting cavity coupled system will play an important role in manipulating integrated hybrid magnon–photon devices.

Diamond rotors

The resolution of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra remains bounded by the spinning frequency, which is limited by the material strength of MAS rotors. Since diamond is capable of withstanding 1.5–2.5x greater MAS frequencies, compared to state-of-the art zirconia, we fabricated rotors from single crystal diamond. When combined with bearings optimized for spinning with helium gas, diamond rotors could achieve the highest MAS frequencies to date. Furthermore, the excellent microwave transmission properties and thermal conductivity of diamond could improve sensitivity enhancements in dynamic nuclear polarization (DNP) experiments. The fabrication protocol we report involves novel laser micromachining and produced rotors that presently spin at ωr/2π = 111.000 ± 0.004 kHz, with stable spinning up to 124 kHz, using N2 gas as the driving fluid. We present the first proton-detected 13C/15N MAS spectra recorded using diamond rotors, a critical step towards studying currently inaccessible ex-vivo protein samples with MAS NMR. Previously, the high aspect ratio of MAS rotors (∼10:1) precluded fabrication of MAS rotors from diamond.

Design evaluation of microwave transmission properties of YBa2Cu3O7-based kinetic inductance detectors

We designed, fabricated, and characterized microwave transmission properties with rewound strip structures for YBa2Cu3O7 (YBCO)-based kinetic inductance detectors (KIDs). The superconducting rewound strip serves as a microwave resonator and as a broadband terahertz-wave antenna. To predict the microwave resonance characteristics before fabrication, the line-width (w) and space (s) dependence of the spiral resonators were analyzed using an electromagnetic simulator; the resonance frequency increased, and the quality factor decreased with increasing w and s from 10 to 40 μm. YBCO-based KID arrays with different w (10 and 40 μm) were fabricated on 10 mm-square MgO substrates, cooled to 3 K using a 4He refrigerator, and evaluated using a vector network analyzer to verify the result of the simulation experimentally. The measured resonance frequency ratio of 1.11 times (5.04 → 5.59 GHz) agreed with the simulated ones of 1.10 times (4.84 → 5.33 GHz) between w = 10 and 40 μm. The other resonance characteristics, such as transmission coefficient and quality factor, have a similar w dependence with the simulation.

Microwave transmission properties of D-(+)-glucose solution with concentration variations

In this paper, we investigate transmission properties of dextrose (D)-(+)-glucose solution with concentration variations using a reusable coplanar waveguide (CPW) device in the frequency ranging from 1 GHz to 10 GHz. In the present experiment, three concentrations of glucose solution, 0.2, 0.4, and 0.6 g ml−1, are measured on the proposed CPW device, and these results are also compared with that of deionized water as a control solution. From the comparative results, as glucose concentration increases, transmission properties are gradually degraded due to the reduction of penetration depth as well as the increase of electric resistance in the observed frequency region. As a result, it can be noted that the concentration variation of D-(+)-glucose solution has a significant effect on the transmission properties related to the microwave circuit, i.e. electric resistance, and field, i.e. penetration depth. In terms of the microwave circuit and field, we expect that our finding can provide fundamental sensing properties for highly sensitive glucose detection via a non-invasive and non-contact technique.

Numerical Simulation on Microwave Transmission Properties of 1-D Periodic Super-Lattice Plasma Photonic Crystals With a Finite-Difference Time-Domain Method

We here report the investigation into the microwave (MW) transmission properties of 1-D periodic super-lattice plasma photonic crystals (PPCs) through numerical simulation with a 2-D finite-difference time-domain method. The super-lattice PPCs are constituted by plasma columns each surrounded by a glass layer, two kinds of which are defined. One is constituted by columns of different shapes and the other by columns of the same shape, whereas other parameter(s) configured unequal. The transmittance bandgap (BG) characters (number, position, depth, and width) of super-lattice PPCs with columns different in shape, plasma frequency ( $f_{p}$ ), electron-collision frequency ( $\nu _{m}$ ), and diameter ( $d$ ), respectively, are compared with those of the corresponding simple lattices with similar parametric configurations. An averaging effect is found in the cases of shape, $f_{p}$ , and $\nu _{m}$ , while decreasing $d$ can serve as an equivalent effect of increasing lattice constant ( $L$ ). The BG character of super-lattice PPCs with simulation parameters changing in different ways is also studied, presenting both similarity and difference comparing to simple-lattice PPCs, and the relationship between the BG position and the $L$ is established.

Anti-ultraviolet and microwave transmission property of ZnO coating on PLA plate

The ZnO coated on the PLA (Polylactic acid) plate with the anti-ultraviolet and high microwave transmission property was fabricated. The particle morphology was measured by the scanning electron microscopy (SEM). The UV-spectrum was measured by the UV Spectrometer. The complex permittivity was measured using a vector network analyzer in 2-18 GHz and the transmission rate (S12) was calculated for the two materials respectively. In order to get the high transmittance property, the genetic algorithm was used to optimize the thickness of the composite and the weight content of the ZnO absorbent. The results showed that the ZnO coating had the good UV protection property, UPF could be estimated 45∼50 as the wavelength was 200∼400 nm, and as the weight content increased, the transmittance value decreased. The composites with thickness 0.1 mm ZnO coating and 1 mm PLA plate had the high transmission rate (larger than 0.95).

Enhanced microwave absorption of screen-printed multiwalled carbon nanotube/Ca1−xBaxBi2Nb2O9 (0≤x≤1) multilayered thick film composites

Multiwalled carbon nanotube (MWCNT)/Ca1−xBaxBi2Nb2O9 (0 ≤ x ≤ 1)-layered thick film microwave-absorbing composites were prepared through the screen-printing method. The multilayered thick film composites were designed to improve their microwave absorption capabilities and the thickness of prepared thick films is around 115 μm. The layered thick film composites were synthesized with functionalized MWCNTs and co-precipitated Ca1−xBaxBi2Nb2O9 (0 ≤ x ≤ 1) (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) Aurivillius-type ceramics. The microwave absorption, transmission and reflection properties were investigated in the J, X, and Ku-bands with a frequency range of 6–18 GHz. The multilayered thick film composites showed enhanced microwave absorption properties in the broadband frequency region. The multilayered composite with x = 0.8 had 1.5 times better microwave absorption than the only MWCNT thick film. This work presents a new approach to the fabrication of multilayered composites with enhanced microwave absorbance via simple screen-printing method.

Suspended individual SWCNT characterization via bottom gate FET configuration

AbstractThe microwave transmission properties of suspended, quasi‐metallic individual single‐walled carbon nanotubes (SWCNTs) with a bottom gate field‐effect transistor (FET) configuration have been investigated up to 10 GHz by standard two‐port S‐parameter measurements under different gate bias voltages. A tapered coplanar waveguide (CPW) transmission‐line test fixture is designed to overcome the parasitic and mismatch issues. An open‐through de‐embedding algorithm has been applied to extract the intrinsic properties of SWCNTs. And an equivalent circuit model has been proposed to fit the extracted measurement data as a function of the bottom gate bias voltage, facilitating the applications of CNTs into high‐frequency nanocircuits. Moreover, the properties of our transistor device are found to change after a period of time.

Single layer graphene possessing anomalous dispersion with exotic microwave transmission and dielectric properties

Abstract The present study aims to experimentally deduce the transmission and dielectric properties of CVD-grown single layer graphene transferred on glass and quartz substrates in wide frequency range from 100 MHz to 10 GHz. First, structural properties of graphene layer have been probed by Raman spectroscopy and then a simple and straightforward de-embedding method based on the propagation constants is adopted to deduce the effective relative permittivity of graphene layer. The graphene layer deposited on the substrate is found to exhibit higher absorption than the bare glass as well as quartz substrate in range of 2–10 GHz. The phase and group velocities have been determined and found to be in well agreement with values obtained by using the standard de-embedding method based on ABCD parameters. In both cases, graphene on glass and quartz, the maximum values of phase velocity are found to be ∼8.57 × 10 7 m/s at 4.12 GHz and ∼9.13 × 10 7 m/s at 4.52 GHz, respectively whereas the respective maximum group velocities for these materials are found to be ∼2.0 × 10 9 m/s and ∼1.9 × 10 9 m/s at 817 MHz.

Terahertz response of NbN-based microwave kinetic inductance detectors with rewound spiral resonator

We have developed microwave kinetic inductance detectors (MKIDs) consisting of dual-purpose rewound spirals (spiral-MKIDs) made of a metal nitride superconductor for terahertz imaging applications. An NbN-based spiral-MKID array with 25 pixels was fabricated, and the fundamental performance of the terahertz receptivity was evaluated at the equilibrium temperature of a conventional 4He refrigerator (≃3 K). The microwave transmission property of the array showed the 25 resonance lines, equally separated by frequency, in the microwave range from 2.70 to 2.95 GHz. To evaluate its optical performance as a terahertz detector, we measured the spiral-MKID’s spectral response, response time, and noise equivalent power (NEP), and confirmed that it revealed a broad spectral response from 1 to 9 THz and an effective response time of approximately 80 μs. The noise-equivalent power was estimated to be .

Humidity Sensor of p-n InN/Si Nanostructure With GHz Resonant Microwave Property

As the growth temperature, annealing temperature, and annealing time of InN sensing film of InN/InNO/In2O3/In/SiO2/Si humidity sensor were, respectively, adjusted at 400 °C, 400 °C, and 15 min, the sensing surface possesses obvious particles of nanometer scale. The particle size of InN sensing film was estimated about 65 nm which realized the quantum effect of InN sensing film for the humidity sensing performance in chemistry. The designed p-n InN/InNO/In2O3/In/SiO2/Si structures of humidity sensor in this paper contained three different buffer layers (indium layer, InNO layer, and In2O3 layer) which also revealed the negative differential resistance effect with peak current density of 2.8 kA/cm $^ {2}$ and peak-to-valley current ratio of 1.93 for quantum resonant microwave performance in physics. The periods of water molecular adsorption and desorption are $\sim 600$ and 580 s, respectively. The sensing resolution of adsorption and desorption is defined by resistance variation per second. The response sensitivity ( $S_{{\it {R}}})$ of adsorption and desorption are $\sim 0.25~\text{m}\Omega $ /s (0.1 %RH/s) and 0.41 $\text{m}\Omega $ /s (0.1 %RH/s), respectively. The InN/InNO/In2O3/In/SiO2/Si humidity sensor revealed the sensing sensitivity of $6 \times 10^{{ {-3}}}$ ohm/% RH. The InN/InNO/In2O3/In/SiO2/Si humidity sensor also revealed the resistive cutoff frequency ( $f_{r})$ and the self-resonant frequency ( $f_{\rm {SR}})$ of microwave device reached as 1.6 MHz and 70 GHz, respectively. Microwave transmission property of p-n InN/InNO/In2O3/In/SiO2/Si humidity sensor reached as gigahertz frequency range can transfer the humidity signal from patient to monitoring station via high frequency wireless communication from one device. InN/InNO/In2O3/In/SiO2/Si humidity sensor can be, therefore, applied in wireless microwave transmission of human body sensing signal.

Microwave Sensing System for Real-Time Monitoring of Solid Contaminants in Gas Flows

The presence of undesired solid contaminants, such as black powder (BP), in natural gas flows diminishes the integrity of the pipeline network. The success of any efficient integrity management program applied to the affected pipeline requires real-time monitoring of the amount of BP traversing the given pipeline and its distribution in the network. In this paper, a new microwave-based system for real-time BP monitoring is introduced and its performance is thoroughly analyzed. The proposed system utilizes custom-designed hermetically sealed probe to interrogate the flow mixture with low-power microwaves in the industrial, scientific, and medical frequency band and monitors the signals reflected from the flow and transmitted through it. Based on extensive simulation and measurement results, it will be shown that the presence of the BP, even in small quantities within the flow, is manifested with considerable variations in the microwave transmission and reflection properties of the flow rendering high overall sensor detection sensitivity and specificity. Experimentally, it will be shown that the developed system can detect flowing BP as well as other contaminants, such as sand, in subgram quantities within 101 mm-ID pipe while utilizing simple detection scheme.

Tunable dual-band negative refractive index in ferrite-based metamaterials

A tunable dual-band ferrite-based metamaterial has been investigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance (FMR) frequency which can be influenced by the dimension of the ferrites. Due to having two negative permeability frequency regions around the two FMR frequencies, the metamaterials consisting of metallic wires and ferrite rods with different sizes possess two passbands in the transmission spectra. The microwave transmission properties of the ferrite-based metamaterials can be not only tuned by the applied magnetic field, but also adjusted by the dimension of the ferrite rods. A good agreement between experimental and simulated results is demonstrated, which confirms that the tunable dual-band ferrite-based metamaterials can be used for cloaks, antennas and absorbers.

MULTI-BAND NEGATIVE REFRACTIVE INDEX IN FERRITE-BASED METAMATERIALS

A multi-band ferrite-based metamaterial has been inves- tigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance (FMR) frequency which can be in∞uenced by the saturation magnetization 4…Ms of the fer- rites. Due to having multiple negative permeability frequency regions around the multiple FMR frequencies, the metamaterials consisting of metallic wires and ferrite rods with various 4…Ms possess several passbands in the transmission spectra. The microwave transmission properties of the ferrite-based metamaterials can be not only tuned by the applied magnetic fleld, but also adjusted by the 4…Ms of the ferrite rods. A good agreement between experimental and simulated results is demonstrated, which conflrms that such a ferrite-based metamaterial possesses a tunable multi-band behavior. This approach opens a new way for designing multi-band metamaterials.

The Influence of Cavity‐defect Shapes on Resonant Peak of Three‐dimensional Electromagnetic Band Gap Structure

Localized mode is an important property of defect electromagnetic band gap (EBG) structure, which plays a key role in the application of EBG structure. The purpose of this article was to study the impact on localized properties by introducing cavities of different shapes into diamond EBG structure. Alumina‐based ceramic diamond EBG structures were fabricated using stereolithography (SL), gel‐casting and vacuum freeze‐drying. When the microwave transmission properties of samples with cavities of different shapes were tested, the resonant peaks appeared within the band gap. By varying the cavity shape, the quality of the localized mode could be adjusted. The results have shown that localized mode with a high quality factor (Q factor) corresponded to the optimal cavity shape in EBG structure. The experimental results agreed well with simulation results. These excellent microwave properties of 3D EBG structure could be directly applied in microwave devices, such as microwave antenna and filter devices.

Microwave transmission properties of metamaterials with double sets of square holes

The transmission property of microwave through a kind of metamaterial is investigated experimentally. Such metamaterials are fabricated with a structure of double sets of square holes: subwavelength ones, and small ones whose sizes and spacing are smaller at least one order of magnitude than those of the subwavelength holes. The experimental results show that the peak power of the measured transmission spectra is dependent on the structure parameters of the small holes. The physical origin to create this phenomenon is that the designer surface plasmons sustained by the small holes affect on the transmission property of the microwave passing through the subwavelength holes. The results are promising for proposing some techniques for optoelectronic devices in terahertz and microwave regime.

Microwave transmission properties of chemical vapor deposition graphene

In this letter, the microwave transmission properties of graphene grown by the chemical vapor deposition are studied by using a multiple-layer coplanar-waveguide transmission-line based measurement method. Remarkable energy loss and phase shift have been observed in graphene from the measured scattering parameters through vector network analyzer. The effective permittivity is deduced by partial-capacitance technique, and the complex permittivity of graphene are extracted in the frequency range of 500 MHz to 6 GHz. Different from conventional dielectric material, the permittivity of graphene shows frequency-dependent below 4 GHz and has an magnitude larger than 104 for both real and imaginary parts.

A New Method to Calculate the Degree of Electromagnetic Impedance Matching in One-Layer Microwave Absorbers

A delta-function method is proposed to quantitatively evaluate the electromagnetic impedance matching degree. Measured electromagnetic parameters of α-Fe/Fe3B/Y2O3 nanocomposites are applied to calculate the matching degree by the method. Compared with reflection loss and quarter-wave principle theory, the method accurately reveals the intrinsic mechanism of microwave transmission and reflection properties. A possible honeycomb structure with promising high-performance microwave absorption, devised according to the method, is also proposed.