High Frequency Microwave Research Articles

TiO2 Nanotube Integrated Microwave Resonator UV Sensor

Ultraviolet (UV) irradiation is extensively utilized in numerous applications such as outer space communication, biological disinfection, memory storage, optoelectronic circuits, and biological analysis [1]. Excessive exposure to UV irradiation is deleterious and causes adverse health effects, for instance, premature aging and skin cancer. A rapid and highly sensitive device for the detection of UV is in great demand in various applications. Recently, planar microwave resonator sensors have demonstrated attractive and robust performance providing high sensitivity, real-time response, and low-cost fabrication process [2]. The planar microwave resonators can easily be integrated with nanostructured materials to make them sensitive to UV radiation via absorption and subsequent charge generation [3]. Among various wide bandgap metal oxides such as TiO2, ZnO, SnO2, one-dimensional TiO2 nanotubes (TNTs) are favorable in UV photodetectors as they possess, except intrinsic TiO2 properties high active surface area and their unique hollow geometry enables increased charge trapping and, a direct pathway for rapid transport of photogenerated carriers [4-6]. Therefore, the use of high aspect ratio (HAR) TNTs might offers superior sensing performance in the UV region.In this presentation, the impact of TNT thicknesses on the UV sensitivity of the planar microwave resonator’s response will be investigated. We will demonstrate the use of a high frequency microwave resonator integrated with different thicknesses (50, 80, 100 µm) of TNT membranes. The presented work will aid in selecting an optimized thickness of TNT membranes with a large active surface-to-volume ratio to provide the highest sensitivity to UV irradiation. We expect this investigation to act as basis for expanding the use of HAR TNTs to effectively develop low-cost, easy to use and robust microwave UV sensors in a wide range of applications. Experimental details and recent results will be presented and discussed.

Evaluation of Magnetic Properties of Ceramic Coated Soft Magnetic Composite and its Simulation for Microwave Devices

High frequency applications (in GHz) require soft magnetic materials with high resistivity, anisotropy and low losses above the ferromagnetic resonance. In this research work, fabrication of toroid cores of the magnesium compound coated soft magnetic composites (M-SMC) was carried out. High frequency magnetic properties (0.5–8 GHz) and microwave complex properties of the materials were determined using B-H analyzer and vector network analyzer. The reflection and transmission coefficients were calculated using the scattering parameters. Using Nicolson-Ross-Weir algorithm complex permeability and complex permittivity were calculated. Mathematical model for hysteresis based on Preisach Classical Model for hysteresis was developed to simulate the hysteresis of the material. By doing variation in thickness of the sample, a broad range of frequency spanning from 0.5 GHz to 7.5 GHz is covered. The optimum range for reflection coefficient i.e. 0.6–0.9 is in the frequency range of 3–5.5 GHz for samples of thickness in the ranges of 2–4 mm and 6–8 mm. The maximum transmission coefficient obtained was 0.6 in the frequency range of 0.5–1.5 GHz for samples of various thickness ranges viz. 2–5.5 mm and 6.5 to 8 mm. The transmission coefficient of 0.6 was also obtained in high frequency range of 3–5.5 GHz in case of samples of thickness 4–6 mm and above 7 GHz for samples of thickness above 6 mm.

Explaining the Changes in Climate, Earth and Viruses: It is Not Only the Carbone Deoxide to Blaim

What have we done to our Earth and its atmosphere to suffer a long-lasting global warming and a long-lasting Pandemic? Is it only the increased Carbone dioxide in the atmosphere to blame, which resulted from the use of coal, gas, and gasoline or there is more to it? I think there is more to it and that is why I am writing this article, which is about the shrinking of our atmosphere seen by our satellites and caused by human activity like HARP. There will be another article about the warming caused by the high frequency microwaves used for our 5G fast internet and their possible influence on the viruses and the ability of our immune system to defend us.

Investigation on Tunable Time Delays of a High-Frequency Microwave Photonic Signal Using a Distributed-Feedback Laser

Investigation on Tunable Time Delays of a High-Frequency Microwave Photonic Signal Using a Distributed-Feedback Laser

Reduced graphene oxide containing barium hexaferrite composites for high frequency microwave absorption

Reduced graphene oxide containing barium hexaferrite composites for high frequency microwave absorption

Nb5+ ion substitution assisted the magnetic and gyromagnetic properties of NiCuZn ferrite for high frequency LTCC devices

Nowadays, developing nickle zinc ferrites with excellent magnetic and gyromagnetic properties are of great importance for solving the matching problem of 5G communication system. However, much is discussed about soft magnetic properties, but little is reported gyromagnetic properties that is critical for microwave device applications. Herein, Nb5+ ions substituted Ni0.29Cu0.18Zn0.53NbxFe2-xO4 (x = 0.00-0.05), possessing high saturation magnetization, approriate initial permeability, high cut-off frequency and low ferromagnetic resonance linewidth (@9.55 GHz), were synthesized by low-temperature firing (900 °C). The phase structure and morphology evolutions were studied in detail. The results of morphology observations revealed that Nb5+ substitution has significant role in determining produce compact and uniform microstructures of NiCuZn ferrites via suppress the grain growth, which further corresponding enhance the magnetic and gyromagnetic properties. As a result, a uniform and compact grain size can be obtained, corresponding to the change of magnetic and gyromagenetic properties have different trends. Enhanced magnetic and gyromagnetic performance including high initial permeability (μ' = 203 @1 MHz), saturation magnetization (4πMs = 3966 Gauss) and low ferromagnetic resonance linewidth (ΔH = 203 Oe) of the NiCuZn ferrites is achieved though adjusting Nb5+ ions substitution. More importantly, this work not only for low temperature co-fired ceramic (LTCC) technology but also for high frequency and microwave frequency devices including phase shifter and radars.

Wideband Backscattering From Alpine Snow Cover: A Full-Season Study

This article experimentally investigates relationships between copol backscattering at a wide range of frequencies (L- to Ka-bands) and snow–ground state parameters (SPs) in different evolution phases during the full winter cycle of 2019/2020. Backscattering coefficients from 1 to 40 GHz, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> snow–ground SPs, and meteorological data are measured at the Davos-Laret Remote Sensing Field Laboratory (Switzerland). Relative strengths of the snow–ground system’s three primary scattering elements (air–snow interface, snow volume, and snow–ground interface) on backscattering are assessed. An anticorrelation between reasonably high snow wetness and backscattering coefficient is found, especially at higher microwave frequencies. For small amounts of snow wetness, backscatter coefficients at L- and S-bands are intensified via increasing snow volume and snow surface scattering. Snow–ground SPs influence backscattering according to their characteristic time scales of temporal evolution. Under dry snow conditions and at low and intermediate frequencies, ground permittivity is the major influencer of backscatter at a time scale of roughly two weeks. Snowfall is the major influencer of backscatter at a time scale of a few hours to a few days. The findings of this article are valuable to the development of retrieval algorithms using machine learning while maintaining a grasp on the ongoing physical processes. Another key message is that multifrequency active microwave measurements are critical to maximize the number of retrievable SPs and their estimation accuracy. For example, while Ka-band performs well in the detection of snow cover, L-band measurements are more responsive to changes of snow water equivalent (SWE) under moist or wet snow conditions.

Root Zone Soil Moisture Comparisons: AirMOSS, SMERGE, and SMAP

A long-standing goal in the terrestrial remote sensing community has been the development of a root-zone soil moisture (RZSM) product based on microwave radar or radiometry observations. For example, the National Aeronautics and Space Administration's (NASA's) Airborne Microwave Observatory of Subcanopy and Surface (AirMOSS) mission between 2012 and 2015 served as an airborne testbed for the development of RZSM estimates acquired from a 420-440 MHz (P-band) radar. Results from the AirMOSS mission suggest that P-band backscatter can be inverted to provide a direct measurement of 0- to 40-cm RZSM. However, whether AirMOSS RZSM is inherently more robust than indirect RZSM estimates including soil MERGE (SMERGE) and Soil Moisture Active Passive Level 4 (SMAP L4) is not clear. SMERGE and SMAP L4 leverage surface (2-5 cm depth), higher-frequency microwave observations (C- and L-bands) via data fusion (DFus) and data assimilation (DA) techniques, respectively. Therefore, the comparisons of these products are warranted and were based on bias, root mean square error (RMSE), and unbiased root mean standard deviation (ubRMSD) metrics. Comparisons also were made against in situ observations providing additional context. The seven AirMOSS sites within the contiguous United States (CONUS) were examined. Overall, direct AirMOSS RZSM measurements, based on the original retrieval algorithms, did not outperform indirect SMERGE and SMAP L4 RZSM estimates. These results provide insight into the viability of achieving enhanced RZSM accuracy via deployment of a spaceborne P-band radar.

Integrated Microwave Photonic Spectral Shaping For Linearization and Spurious-Free Dynamic Range Enhancement

Integrated microwave photonics (MWP) is a fast growing area where high frequency microwave signals are processed in the optical domain, merging key advantages of both microwave photonics and photonic integrated circuits (PICs) technologies including low-loss, reconfigurability, advanced functionality, enhanced stability, and reduced footprint. Plenty of functionalities have been demonstrated in integrated MWP, especially based on spectral shaping technique, where the phase and amplitude of the optical spectrum is precisely tailored by PICs. However, on-chip linearization is lagging behind and has not been investigated deeply. It is crucial and urgent to study on-chip linearization methods, which will lead to advanced integrated MWP systems with large spurious-free dynamic range (SFDR). In this paper, we present two novel techniques for on-chip linearization of microwave photonic links. The first technique is based on line-by-line complex spectral shaping using a series of ring resonators. The second technique relies on spatial separation to achieve parallel spectral shaping in two complementary spatial channels. Both methods are demonstrated in low-loss programmable silicon nitride circuits that can already host a number of advanced functionalities. Our results point to the great potential of integrating advanced functionalities and linearization in the same integrated platform.

Experiments on intense ion beam formation with an inhomogeneous electric field

The high efficiency of a new ion beam extraction system with a strongly inhomogeneous electric field has been experimentally demonstrated. Previously, this approach was proposed and analysed numerically by the authors. The experiment was carried out using a pulsed high-current electron-cyclotron resonance (ECR) ion source SMIS 37 with high frequency (37.5 GHz) and high power (100 kW) microwave plasma heating. The accelerating field strength is increased (when compared to a flat or a quasi-pierced geometry) in the plasma meniscus region due to its inhomogeneity. It allows for the increase of the ion acceleration rate and for expansion of the available range of current densities with effective ion beam formation. The experiment demonstrated the main advantages of this approach, such as: a significant decrease in the optimal accelerating voltage for certain values of current density; a possibility of ion beam formation with previously inaccessible current densities; a significant decrease in the ion flux to the puller in non-optimal modes of ion beam formation. Proton beams with a current density of up to 1.1 A cm−2 were obtained for the first time with an ECR ion source.

Water-based devices for advanced control of electromagnetic waves

Tunable devices are of great interest as they offer reconfigurability to their operation, although many of them employ rare and expensive materials. In a world with increasing focus on ecological compatibility and recyclability, immense efforts are being made to find bio-friendly alternatives. However, in some cases, one does not have to look far, because water, a high-permittivity dielectric at microwave frequencies, is readily available. Recent studies have shown that compact Mie resonators, which are the fundamental blocks in all-dielectric metamaterials and dielectric resonator antennas, can be realized with small water elements. In a variety of applied physics areas, encompassing frequencies from the radio to the optical parts of the spectrum, all-dielectric implementations have received immense attention. When it comes to water, its temperature-dependent permittivity and liquidity enable a multitude of unprecedentedly simple means to reconfigure and tune the resulting devices. Moreover, being a polar solvent, water easily dissolves various physiologically important electrolytes, which potentially can be exploited in a sensor design. Presently, we review water-based devices for advanced microwave control and sensing. We show and discuss the dynamic properties of water and examine the microwave scattering and absorption characteristics of single water elements. We investigate how such water elements can be employed in various microwave designs, including single resonators, metamaterials, metasurfaces, antennas, absorbers, and radio frequency components. The main complications of water are its losses, especially at higher microwave frequencies, and its stability. We discuss how to overcome these and show that even highly loss-sensitive modes, namely, toroidal modes and bound states in the continuum, can be realized with water-based devices. We believe that water-based devices usher the route to meet the UN proclaimed goals on global sustainability and human-friendly environment.

Профилактические меры по снижению негативного воздействия электромагнитного излучения на здоровье

Man-made electromagnetic waves are the most widely and rapidly expanding exposure in today's world, including exposure in several frequency groups: extremely low frequencies (ELF) from electricity lines, hybrid car batteries and high power lines (&gt;3 Hz–3 kHz), radiofrequency (RF) and microwave frequencies including millimeter waves (3 kHz–300 GHz) from mobile phones, towers, base stations and wireless devices, and intermediate frequencies "Dirty Electricity" emitted from power lines. While such organizations as ICNIRP (the International Commission on Non-Ionizing Radiation Protection) still continue to claim that electromagnetic radiation can cause "only thermal effects", clinging to theory that does not match facts and upholding obsolete thermal safety standards, extensive scientific evidence has clearly demonstrated that non-thermal health effects produced by electromagnetic radiation do exist, are important to health, and should be taken into consideration when safety standards are set. This review aims to highlight some evidence of biologic effects in various body systems, and to suggest preventive measures to reduce such effects on health. Exposure to electromagnetic radiation at intensities lower than thermal safety standards has been associated with non-thermal biological effects including damage and changes to cells and DNA. This review presents evidence of such effects demonstrated in: the hematologic system, the nervous system, the immune system, the reproductive system, the skin and muscles, the cardiovascular system, glucose metabolism, and Electrohypersensitivity ("Microwave sickness"). Protective measures are then suggested to reduce these effects.

Preventive measures to reduce harmful effects produced by electromagnetic radiation on health

Man-made electromagnetic waves are the most widely and rapidly expanding exposure in today's world, including ex- posure in several frequency groups: extremely low frequencies (ELF) from electricity lines, hybrid car batteries and high power lines (&gt;3 Hz–3 kHz), radiofrequency (RF) and microwave frequencies including millimeter waves (3 kHz–300 GHz) from mobile phones, towers, base stations and wireless devices, and intermediate frequencies "Dirty Electricity" emitted from power lines. While such organizations as ICNIRP (the International Commission on Non-Ionizing Radiation Protection) still con- tinue to claim that electromagnetic radiation can cause "only thermal effects", clinging to theory that does not match facts and upholding obsolete thermal safety standards, extensive scientific evidence has clearly demonstrated that non-thermal health effects produced by electromagnetic radiation do exist, are important to health, and should be taken into considera- tion when safety standards are set. This review aims to highlight some evidence of biologic effects in various body systems, and to suggest preventive measures to reduce such effects on health. Exposure to electromagnetic radiation at intensities lower than thermal safety standards has been associated with non- thermal biological effects including damage and changes to cells and DNA. This review presents evidence of such effects demonstrated in: the hematologic system, the nervous system, the immune system, the reproductive system, the skin and muscles, the cardiovascular system, glucose metabolism, and Electrohypersen- sitivity ("Microwave sickness"). Protective measures are then suggested to reduce these effects.

Dielectric Coupler for General Purpose Q-Band EPR Cavity

Here, we report on a robust and efficient mechanism for tuning the microwave coupling of a Q-band (34 GHz), general purpose, cylindrical EPR cavity operating in the TE011 mode. This novel mechanism allows for both the adjustment of the cavity’s coupling over a wide frequency range, as well as its bandwidth from that of a high-Q cavity (about 10 MHz), to a broadband cavity (above 1 GHz). The coupling element consists of a dielectric plate fixed onto a movable waveguide short that allows for two modes of operation. In the first mode, the dielectric plate does not influence the resonance properties of the coupling iris and allows for precise, critical coupling of the high-Q cavity. In the second mode, the dielectric plate is positioned in front of the coupling iris, varying the iris’ resonance properties and allowing very strong overcoupling to be achieved. This mechanism can be generalized for other types of EPR cavities, in particular at high microwave frequencies.

Study of optical properties of gold nanoparticles embedded in normal, benign, and malignant breast tissues

In this work, the complex dielectric permittivity of breast tissue is calculated for different growth rates of benign and malignant tumors using the Maxwell Garnett (MG) effective medium theory. The results show a wide variability of the dielectric properties depending on the nature and the volume fraction of the cancer cells. The benign-normal and malignant-normal heterostructures are denoted respectively x-B/N and x-M/N where x is the volume fraction of cancer cells in the breast tissue. The real and imaginary parts of dielectric permittivity increases when the growth rates of benign and malignant tumors increase and decrease when the microwave frequency increases from 0.5 to 8 GHz. In the aim to use the gold nanoparticles (GNPs) in breast cancer therapy, both for a better image diagnostic and photothermal therapy (PTT), we present here a study on the optical properties of GNPs embedded in normal, benign and malignant breast tissue in the frequency range from 0.5 GHz to 8 GHz. optical band gap energy for GNP is located in [0.5eV−1.46eV](±0.06eV), [0.72eV−1.20eV](±0.04eV) and [0.11eV−0.74eV](±0.02eV) ranges for Normal, Benign and Malignant breast tissues, respectively. We use the Finite Element Method (FEM) to evaluate the spectra of the dielectric and optical parameters of GNPs namely: complex dielectric permittivity, absorption cross section, reflectivity, dielectric loss function and conductivity, the surface plasmons resonance (SPR) properties are deduced from these spectra. The obtained results show that the SPR-peak of the GNPs is located in the Visible (Vis), near infrared (NIR) and short wavelength infrared (SWIR) bands when they are embedded respectively in the normal, benign and malignant breast tissue. For these three tissues when the microwave frequency increases from 0.5 to 8 GHz, the SPR-peak position λmax shifts towards the short wavelengths. The calculations show that in the vicinity of λmax the dielectric loss function take a maximum value and the reflectivity change strongly. These results show that the absorption and dielectric loss peaks are less wide for the high microwave frequencies and very wide for the low frequencies, which also influences the difference between the asymptotic values of the real part of permittivity and of the reflectivity. These results make it possible to identify the nature of the breast tumor using the GNPs in the sensors based on the of SPR phenomenon. The optical properties of GNPs depending on their size and on the tumor growth rate in the breast tissue are also studied and discussed. The study carried out represents a feasibility proposal for the use of GNPs for determining the degree of breast tumor progression and estimate the good performance of using the GNPs for the selective destruction of breast cancer cells.

Low dielectric loss and narrow FMR linewidth of Ca-Ge co-substituted YInIG ferrites for microwave device application

Recently, the yttrium iron garnet (Y3Fe5O12, YIG) ferrite material is widely applied in the microwave devices due to its good frequency stability and loss magnetic loss. In this work, Y3−xCaxIn0.6GexFe4.4−xO12 (x = 0.0–0.6 with a step of 0.1) materials were synthesized by the conventional solid-state reaction method. The effects of Ca-Ge co-substitution on the microstructural, dielectric and magnetic properties of YInIG materials were investigated. Ca-Ge co-substitution did not change the phase formation of YInIG ferrite, and enhanced dielectric and magnetic properties of samples. The high saturation magnetization (4πMs), low dielectric constant (εr), low dielectric loss (tanδε), small coercivity (Hc) and narrow ferromagnetic resonance (FMR) linewidth (ΔH) were obtained for high frequency microwave device application. When substituted content x = 0.4, Y2.6Ca0.4In0.6Ge0.4Fe4O12 has the optimum microwave properties: εr = 13.884@10.8 GHz, tanδε = 3.053 × 10–4, Hc= 22.75 Oe, 4πMs = 1226.83 Gs, ΔH= 19.3 Oe. The narrow FMR linewidth and low loss dielectric loss of the investigated samples suggested the possible use of these materials in high frequency applications.

Improvement of thermal stability and gamma‐ray absorption in microwave absorbable poly(methyl methacrylate)/graphene nanoplatelets nanocomposite

AbstractThe graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) by in situ polymerization method. The optimum high frequency (microwave) absorption was evaluated at X‐band due to changes in the scattering parameters (determined by using a vector network analyzer). The slight improvement has been attained in gamma attenuation coefficient of the polymer nanocomposite by using gamma transmission technique. The addition of graphene nanoplatelets (2 wt%) resulted in a thermal improvement from 196.73 to 243.00°C (with 5% weight loss) in TGA analysis. The graphene nanoplatelets provided an optimum decrease in scattering of the microwaves due to the elimination of the defects and the prevention of the agglomeration of the graphene nanoplates. The improvement of microwave absorption (between 8 and 12 GHz) suggested that the nanocomposite was a suitable candidate as a microwave absorbing material. This multipurpose nanocomposite has provided thermal stability and it has ensured the optimum gamma‐ray and microwave absorption depending on the development of the structural properties. The development of these physical characteristics has enabled to improve the electrical conductivity as a result of the progress in the structural properties.

Study of high efficiency, low noise sputtered magnetron's cathode using GaN and SiC semiconductors for modulated microwave power transmission

AbstractSemiconductor deposition on magnetron's cathode surface using different materials such as gallium nitride (GaN) and silicon carbide (SiC) semiconductors is conducted to grow approximately 80, 100 and 120 nm plasma layers. The cathode is then used to generate high frequency and low-power microwave for further comparison and analysis with the conventional magnetron operation. Parameter of analysis to identify the efficiency includes electron drift velocity, harmonic order, total harmonic distortion, low harmonic distortion, and spectrum observation. The sputtered cathode of the magnetron is used to generate a low-power microwave observing a generator efficiency up to 93 and 88% for GaN and SiC materials, respectively, compared to the conventional material, which observes 37% of efficiency at 2450 MHz, 5 W. Also reported is the quality of semiconductor sputtering on the magnetron cathode, which was manipulated by the deposition period, temperature, and plasma layer growth thickness.

Performance Characteristics of Unsaturated Polyester Reinforced with High Frequency Microwave Treated Natural Fibre

Using the most environmentally sustainable agro-waste fibers as reinforcement has opened up a new direction for polymer composite research. Research has recommended that altering of fibre surface by both chemical and physical means, increases the performance characteristic of natural fibre/polymer matrix. In this study, high-frequency microwave irradiation at a frequency of 2.45 GHZ and 550W power was used to treat natural fibre extracted from plantain (Musa paradisiacal) pseudo steam. Microwave modified and untreated plantain fibre was used to fabricate a biocomposite using polyester resin as polymer matrix, by means of hand lay-up and compression moulding technique. Results reveal an increase in mechanical strength of the modified fibre reinforced bio-composites at optimised conditions, thus creating opportunities and consistency to be use in technological and structural applications.

Design and Characterization of n–Si/p–CdO Broken Gap Heterojunctions as High Frequency PMOSFETs and Microwave Resonators

Herein, p- type CdO thin films coated onto n- type Si crystals are employed to form metal oxide semiconductor field effect transistors (MOSFET). In the broken gap design, the valence band edge of Si substrates centered at 5.25 eV is aligned at conduction band edges of CdO centered at 5.20 eV. The construction of the energy band diagram indicated that the devices could reveal a deep built in potential of 4.68 eV. The device is fabricated by the thermal evaporation technique under vacuum pressure of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> mbar. CdO thin films grown onto Si thin crystals form a randomly distributed nanorod-like grains of rod length and diameter of ~2.0 μm and 160 nm, respectively. In addition, n-Si/p-CdO heterojunctions displayed typical diode characteristics with ideality factors of equiv. 1.40 and barrier height of 0.67 eV. As passive mode devices, the C-V curves displayed enhanced PMOS channel with the ability of capacitance depletions in a wide range of frequency (10M-1.0 GHz). The depletion width of the device widens from 7.0 nm to 660 nm in that frequency domain. Moreover, the biased and unbiased impedance spectra analyses in the frequency domain of 1.0M-1.0 GHz, indicated the voltage controllability of the devices when operated as microwave cavities. The magnitude of the reflection coefficient spectra indicated the ability of using the MOSFET devices as high pass filters. The features of the n-Si <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">/p</i> -CdO heterojunctions nominate them for use as microwave band filters, PMOS field effect transistors and as frequency and voltage controlled tunable capacitors.