Microwave Chamber Research Articles

Wideband Transmissive Programmable Metasurface for Adaptive Millimeter‐Wave Beamforming

AbstractProgrammable metasurfaces provide a promising paradigm for the beamforming of electromagnetic waves in the fifth‐generation (5G) and sixth‐generation (6G) wireless communications with low cost and low complexity. However, most of the existing researches are focused on the sub‐6 GHz spectrum, which limited the gigabits per second (Gb s−1) high‐speed data transmission on future wireless network. Additionally, as a step forward in the development of intelligent metasurfaces, extra peripheral devices are often required to sense environmental variations for self‐adaptive modulations. Here, a wideband millimeter‐wave programmable metasurface is presented for peripheral‐free self‐adaptive signal enhancement in 5G/6G wireless communication. The proposed transmissive programmable metasurface consists of meta‐atoms, exhibiting efficient transmission (1 dB loss) and a stable 1‐bit phase difference from 23.7 to 32.1 GHz, effectively covering the desired 5G millimeter‐wave frequency bands: N257, N258, and N261. By integrating the self‐adaptive algorithm based on received signal intensity into the controller, the programmable metasurface can self‐adaptively establish an optimal or acceptable channel according to the predefined threshold values. To evaluate the performance of the prototype, an experiment on wavefront modulation was first conducted in a microwave chamber, verifying the wideband beamforming performance of the programmable metasurface. Moreover, self‐adaptive signal enhancement and millimeter‐wave wireless communication experiments were conducted in indoor environments, showing a maximum signal enhancement of 21.4 dB and a significant improvement in constellation. The proposed self‐adaptive wideband programmable metasurface demonstrates high potential for application in 5G/6G millimeter‐wave wireless networks.

Energy and exergy performances of low-density polyethylene plastic particles assisted by microwave heating.

Plastic waste can exist naturally for hundreds of thousands of years and harm humans, animals, and the environment. In this study, the energy and exergy performances (absorbed energy, energy efficiency, absorbed exergy, and exergy efficiency) of LDPE (low-density polyethylene) plastic particles assisted by microwave heating based on the experimental data as affected by microwave power, feeding load, and chamber volume were evaluated and analyzed. The results showed that as the microwave power raised from 500 to 900 W, the feeding load changed from 10 to 30g, and the chamber volume decreased from 200 to 100ml, (a) the absorbed energy at the heating time of 60min increased from 19.73kJ, 5.84kJ, and 22.71kJ to 37.69kJ; (b) the energy efficiency for the whole heating process increased from 1.10%, 0.32%, and 1.26% to 2.09%; (c) the absorbed exergy at the heating time of 60min increased from 0.308, 0.091, and 0.091 to 0.724kJ; and (d) the exergy efficiency for the whole heating process increased from 0.017, 0.005, and 0.023 to 0.040%, respectively.

Novel superhard BC10N synthesized by microwave plasma CVD

Microwave Plasma Chemical Vapor Deposition (MPCVD) was used to synthesize novel superhard BC10N on silicon substrates. Feedgas mixtures of H2, CH4, N2, and B2H6 were used for a range of systematically varied microwave power, chamber pressure, and flow rate conditions. Optical Emission Spectroscopy (OES) was used to guide the synthesis of BC10N. Plasma optical emission from the C2 peak increases with pressure up to 80 Torr and saturates in the 80–100 Torr range. The C2 emission also follows the same trend, growing non-linearly with increasing microwave power (for fixed chamber pressure of 30 Torr). The presence of abundant C2 in the plasma is advantageous under specific growth conditions to produce superhard carbon-rich BC10N, a material that has been theoretically predicted but not yet synthesized. Findings obtained from X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) elucidate the existence of BC, CN, BN, and B-N-C bonding in the synthesized coating. Nanoindentation hardness measurements are within the superhard regime, showing an average hardness of 63 GPa.

Miniaturized wide‐band microstrip grid array antenna loaded with slow‐wave transmission line

AbstractA miniaturized microstrip grid array antenna (MGAA) in X‐band is proposed in the paper. The antenna consists of a radiation grid array, a feed network and a metal back cavity. The 2 × 2 planar grid array is constructed by using four MGAAs as subarrays. MGAA does not require complex feeders in contrast to microstrip patch arrays. Furthermore, a curved slow‐wave transmission line (SWTL) is adopted as the long side of grid. The SWTL not only reduces the physical size of the grid while keeping its electrical size unchanged, but also improves the impedance matching and greatly broaden the bandwidth of the antenna. A fabricated prototype was measured in the microwave chamber. The results indicate that the impedance matching band of |S11| < −10 dB is from 9 to 10.5 GHz (15.4%), and the maximum gain is 19.2 dBi. Meanwhile, the projected area of the antenna is reduced by about 40% by loading the SWTL.

A Wide-Band Low-Profile Antenna for a High-Integration Phased Array System.

In this paper, a wide-band, low-profile antenna is presented for a high-integration phased array system. The proposed antenna, implemented using a tightly coupled array, operates over roughly the X-K frequency band and is performant at 8 GHz-18.5 GHz. The antenna can scan to ±60 degrees in both the E- and H-planes. Compared to previous tightly coupled antennas with smaller element spacing, the antenna in this paper reaches 9.4 mm, which corresponds to 0.58 λ of high frequency, suitable for engineering application conditions in production. The antenna can be soldered to BGA T/R chips in this space. Additionally, to facilitate flexible assembly for large arrays, the antenna is manufactured modularly using four elements and its parasitic radiation is analyzed. Then, a method for repressing parasitic radiation is presented. Finally, the antenna is fabricated and measured in a microwave chamber, exhibiting an excellent pattern and scanning radiation. The measured performance agrees with the full-wave finite array simulations.

Design of the Monopulse Feeding Network for a Slotted Waveguide Array on an Annular Disk

Design of a monopulse feeding network including a compact power distribution network and a monopulse comparator for a dual polarization slotted waveguide array fabricated on an annular disk is presented in this paper. As the slotted waveguide array is arranged on an annular disk, the feeding network is more complicated than that of a regular array such as a rectangular array. The design details of some key waveguide components, such as the compact assembly of H-plane T-junctions and E-plane elbows used to connect power distribution networks and radiation waveguides, are provided. Quasiplanar magic tees are designed and used to construct the compact sum and difference comparator. The antenna system contains two comparators, which are used to generate sum and difference beams for horizontal polarization and vertical polarization, respectively. Finally, the monopulse slotted waveguide array antenna is divided into two modules, a comparator module and an antenna module (including power distribution network), and fabricated with the layered processing and bonding process. The comparator module is measured using a network analyzer to verify its amplitude-frequency characteristics and phase-frequency characteristics. Screwing the comparator module and the antenna module together, a monopulse slotted waveguide array antenna is obtained, and the sum beam and difference beam characteristics of the antenna are measured in a microwave chamber and presented.

An improved gain and directivity design of an antipodal Vivaldi antenna for ultra‐wideband detection

AbstractA novel antipodal Vivaldi antenna (AVA) is proposed to achieve improved gain and directivity. To enhance the bandwidth of the antenna, a series of equal‐sized slots are etched onto the patch surface. Additionally, a dielectric lens with a fan‐shaped structure is integrated along the patch openings to boost gain. The length of the lens which will affect the radiation characteristics of the antenna in the end‐fire direction will be discussed. Furthermore, three arrays of directors are added to enhance the directivity. The fabricated antenna is then measured using a vector network analyzer in a microwave chamber to assess its performance. The results indicate that the antenna's minimum operating frequency is reduced by 0.5 GHz after etching the slots. Besides, the average gain is improved by 1 dBi after installing the fan‐shaped expansion structure. By introducing the directors, the sidelobe levels decrease and the 3 dB Half‐Power Beamwidth becomes sharper. Finally, an ultra‐wideband (UWB) detection experiment is designed to analyze the detection capability of the fabricated antennas. The results demonstrate that the antenna is well‐suited for UWB applications.

A STUDY ON SiC SUSCEPTOR CONFIGURATION FOR MICROWAVE HYBRID HEATING

Microwave hybrid heating (MHH) is a novel method to enhance ceramic sintering at high temperatures. The heating mechanism by MHH involves two directions of heat transfer for materials: microwaves heat the sample from the inside out, while the susceptor provides conventional heating from the outside. This unique heating mechanism offers several advantages, including uniform heating, rapid sintering, and enhanced microstructure and properties of materials. This study investigates the configuration of silicon carbide (SiC) susceptors for microwave hybrid heating. The microwave oven (multi-mode, 2.45 GHz, 1.2 kW) was modified with a ceramic insulator housing to maintain the temperature in the chamber. The effects of different configurations of SiC susceptors and microwave powers on the heating rate and maximum temperature were investigated. SiC susceptor plates were placed in the microwave oven using 3 different configurations, and for each condition, the microwave power was varied at 40, 60, 80, and 100% (480, 720, 960, and 1,200 W). The temperature in the microwave chamber was recorded until it reached 900°C or after 30 min of heating. Using two plates of SiC susceptor at 100 % power resulted in the highest heating rate of 62°C/min to reach 925°C. The results of this study offer guidance for the selection of appropriate heating conditions for individual ceramic materials, which can lead to more effective sintering processes.

Heating performances of corn straw particle with/without SiC particle in a microwave chamber.

The amount of biomass production each year is huge, and microwave-assisted pyrolysis of biomass to obtain biogas, bio-oil, and biochar is a promising method. In this study, silicon carbide (SiC) was selected as the microwave absorber, and the effects of microwave power (400, 450, 500, 550 and 600 W), reactor chamber volume (100, 150, 200, 250, and 300 W), and the mass ratio of SiC and corn straw (0, 0.25, 0.5, 0.75, and 1) on the heating performances of corn straw particles were investigated and presented in this study. When the microwave power increased from 400 to 600 W, the average heating rate of corn straw particles increased from 23.06 ℃ /min to 101.46 ℃ /min, and that of mixture particles of corn straw and SiC increased from 87.00 ℃ /min to 236.88 ℃/min. When the reactor chamber volume increased from 100 to 300mL, the average heating rate of corn straw particles decreased from 38.21 ℃/min to 22.54 ℃/min, and that of mixture particles of corn straw and SiC decreased from 98.84 ℃/min to 76.01 ℃/min. When the mass ratio of SiC and corn straw increased from 0 to 1, the average heating rate of mixture particles of corn straw and SiC increased from 101.46 ℃/min to 236.88 ℃/min. Some formulae with R2 values ranged from 0.971 to 0.998 were proposed to determine the transient temperatures of corn straw particles and mixture particles of corn straw and SiC.

Modeling of the Modification Process of an Epoxy Basalt-Filled Oligomer in Traveling Wave Microwave Chambers

This paper presents modeling data to select the optimal industrial unit for the microwave modification of an epoxy basalt-filled oligomer (EBO) at electric field strength E of an electromagnetic wave equal to 11.9 × 103 V/m and a uniform distribution of the temperature field over the entire volume of the modified object. A mathematical description of the electrodynamic and thermal processes occurring in the object under consideration subjected to microwave exposure includes the Helmholtz equation for the electric field strength vector and the heat conduction equation. The joint solution of this problem in a three-dimensional formulation is based on the use of the finite element method, which in this work was implemented in the COMSOL Multiphysics® 6.1 software environment. According to the modeling results, the use of microwave chambers with a traveling wave of a waveguide type is inefficient because the required value of the electric field strength E is not achieved, while the modeled microwave chamber with a traveling wave on a quasi-coaxial waveguide makes it possible to achieve the required value of the electric field strength E and uniform distribution of the temperature field over the entire volume of the modified object by reducing the generated power for the modification of an EBO from 400 W up to 300 W. Optimal parameters for modifying an epoxy basalt-filled oligomer in the microwave electromagnetic field in the working chamber with a traveling wave on a quasi-coaxial waveguide have been developed, which provide a uniform microwave modification of an EBO with a microwave installation capacity of 11.6 kg/h. A sketch of an industrial microwave working chamber has been developed, which provides a mode of the uniform modification of the oligomer at electric field strength E = 12.3 × 103 V/m. The proposed microwave chamber with a traveling wave on a quasi-coaxial waveguide can be replicated for the microwave modification of filled oligomers of various chemical compositions.

Evaluation of the efficiency of microwave heating of soils

One of the innovative directions of heat treatment of soil in the technologies of decontamination from pesticides, oil products and disinfection is heating in a microwave electromagnetic field. Numerical studies testify to the effectiveness of the microwave treatment method. This is due to the peculiarities of the interaction of the microwave field with dielectric materials. Unique effects arise, such as the possibility of local heating, volume heating of the material, unidirectionality of pressure and humidity gradients. This contributes to the intensification of transfer processes and the possibility of energy savings. However, the challenge at present is to determine the processing regimes, including load mass, specific microwave field power, electric field strength, material layer thickness, and processing time, under which the microwave method will be energy efficient. Conducting multifactorial experimental studies allows determining the conditions of energy feasibility of microwave soil treatment. Therefore, the object of research is the process of heating a dense layer of soil under the action of a microwave electromagnetic field. The results of studies on the effect of microwave treatment of soil contaminated with organophosphorus pesticides, contaminated with petroleum products, and under what conditions the qualitative effect was obtained, as well as the results of the effect of the microwave field on the pathogenic microflora of the soil used for growing plants, were considered. The high quality of implementation of soil treatment technologies is determined. Energy efficiency was determined on the basis of data on temperature and moisture content, analysis of thermograms of microwave heating of chernozem and clay soil, analysis of the influence of material layer thickness, influence of dielectric properties and power of the microwave field. According to the results of thermal calculations, the values of the efficiency of the microwave chamber and the intensity of the electric field were determined, which are recommended as the basis for scaling in order to transfer the experimental results to industrial installations. During the research, specific experimental methods of research under microwave heating conditions, analytical methods of thermal calculations, developed by the authors of the experimental research methodology were used. Experimental studies were carried out on the installation created by the authors. The results of the research are intended for the wide implementation into practice of technological calculations of microwave chambers for heat treatment of soils, intensification of disinfection processes under the conditions of energy efficiency of the transformation of the energy of the microwave field into the internal energy of the soil.

Technique of Expanding the Thermal-Indication Capabilities of Standard Thermal Paper for Studying the Field Distribution in a Microwave Chamber

Technique of Expanding the Thermal-Indication Capabilities of Standard Thermal Paper for Studying the Field Distribution in a Microwave Chamber

Heating performances of corn straw particles in a microwave chamber

ABSTRACT Heating performance of biomass is of significant importance for the followed chemical reactions i.e. pyrolysis, gasification, combustion, etc. Corn straw (CS) is an important renewable resource. Microwave (MW) heating performances of corn straw particles affected by corn straw mass (10, 16, 22, 28 and 34 g), corn straw particle size (0.075, 0.125, 0.200, 0.355 and 0.600 mm) and microwave power (400, 450, 500, 550 and 600 W) were explored in detail in this study. It can be obtained that when the microwave powers were 400, 450, 500, 550 and 600 W, the average heating rates were 23.06, 33.19, 61.35, 88.70 and 101.46°C/min, respectively. When the corn straw particle sizes were 0.075, 0.125, 0.200, 0.355 and 0.600 mm, the average heating rates were 101.46, 61.07, 52.70, 37.34 and 56.04°C/min, respectively. When the corn straw masses were 10, 16, 22, 28 and 34 g, the average heating rates were 36.31, 46.24, 101.46, 92.95 and 46.01°C/min, respectively. Formulae were further proposed to estimate the transient temperatures of biomass particles, and the R2 values ranged from 0.984 to 0.999.

Estimation of Axial Ratio of Single-Port Dual-Mode Circularly Polarized Antenna Using Reflection Coefficient

In this article, a simple way that can estimate the axial ratio (AR) of a circularly polarized (CP) antenna using its measured reflection coefficient is proposed. The estimation method applies to a single-port CP antenna that is composed of two resonant modes with orthogonal polarization and 90° phase difference. It is most common among CP patch antennas, cross-dipole antennas, and substrate-integrated waveguide antennas. Based on the equivalent circuit model, the analysis method builds a bridge between the reflection coefficient and excitation property. It is shown that the trace property of the reflection coefficient on the Smith Chart infers whether the antenna performs the best AR value and AR bandwidth. By locating impedance points and extracting circuit parameters, accurate circular polarization properties can be estimated. We also provide a numerical way, which is based on an optimization algorithm, to estimate the AR while considering the difference between the two equivalent antenna resonators. A verification program is compiled, and different CP antennas are simulated, fabricated, and analyzed. This study also illustrates the source of estimation errors and proves that the method reaches acceptable AR estimation without time-consuming microwave chamber measurement. Therefore, the method provides a new look to high-speed pre-test and tuning for volume production of CP antennas.

Generation of Circulating Cavity Magnon Polaritons

In a circulating cavity magnon polariton (quantized spin wave plus photon, resonating in a microwave chamber), the hybrid state and a noninteracting photonic state rotate in opposite directions---an important phenomenon for generating chiral states of electromagnetic modes in cavity magnonics and microwave engineering, to impart angular momentum upon standing waves. This study demonstrates the unidirectional nature of the mode propagation, paving the way for the generation of a high-power microwave beam with high coherence and narrow bandwidth. The authors also demonstrate how the unidirectional mode propagation results in nonreciprocity of the mode's transmission amplitudes and phases.

A technique for expanding the thermal indication capabilities of standard thermal paper for studying the field distribution in a microwave chamber

A technique for expanding the thermal indication capabilities of standard thermal paper for studying the field distribution in a microwave chamber

Improving the quality of bog oak boards using microwave drying chambers

The stocks of bog oak taken from the bottom of reservoirs are increasingly used to preserve growing valuable species of wood, primarily oak. English oak (Quercus pedunculata Ehrh.) is a hard-drying species. Drying modes of oak boards have been well developed for both convection and microwave drying. The interest in bog oak, rose out from water bodies, sharply increased, but it turned out to be impossible to dry it using known methods other than microwave drying. Cracking defects are 70% at a thickness of 30 mm and 100% at a cross section of 60 mm. The article analyzes the results of bog oak drying in laboratory-type microwave chambers. The distance between magnetrons was 0.5 m, and a length of boards was 1.2 m. A semicommercial plant with a loading volume of 2 m3 and total power of 30 kW was used. Total drying time for boards with a total loading volume of 0.2 m3 was from 3 to 5 days. Cracking defects reduced to 20% for a thickness of 30 mm and to 32% for a thickness of 60 mm (with additional treatment by 40% carbamide solution). Board warping was not noticed.

Использование СВЧ излучения для предынкубационной стимуляции яиц сельскохозяйственной птицы

The article describes the effect of short-term exposure to an electromagnetic field (EMF) of microwave radiation at a frequency of 2.45 GHz on the rate of development of an embryo in an egg of an agricultural bird. To carry out the experiments, a laboratory microwave setup was developed for controlled and controlled impact on the object being processed. The dielectric characteristics of protein and yolk of fertilized and non-fertilized poultry eggs were measured and analyzed, on the basis of which computer electromagnetic modeling of a microwave chamber for a laboratory pre-incubation processing unit was carried out. The influence of the microwave field on the concentration of proteins in the eggs of poultry was experimentally tested depending on the time of exposure. Keywords: EMF MICROWAVE RADIATION, ENVIRONMENTALLY FRIENDLY STIMULATION OF DEVELOPMENT

Использование СВЧ излучения для предынкубационной стимуляции яиц сельскохозяйственной птицы

The article describes the effect of short-term exposure to an electromagnetic field (EMF) of microwave radiation at a frequency of 2.45 GHz on the rate of development of an embryo in an egg of an agricultural bird. To carry out the experiments, a laboratory microwave setup was developed for controlled and controlled impact on the object being processed. The dielectric characteristics of protein and yolk of fertilized and non-fertilized poultry eggs were measured and analyzed, on the basis of which computer electromagnetic modeling of a microwave chamber for a laboratory pre-incubation processing unit was carried out. The influence of the microwave field on the concentration of proteins in the eggs of poultry was experimentally tested depending on the time of exposure. Keywords: EMF MICROWAVE RADIATION, ENVIRONMENTALLY FRIENDLY STIMULATION OF DEVELOPMENT

Dual‐interference filtering method for the main lobe based on polarimetric monopulse radar

In the field of target tracking, monopulse radar is widely used to obtain the positions of radar targets. The achieved angle measurement performance is greatly weakened when barrage interference is contained in the main lobe of the receiving antenna. Interference signals can be easily filtered by the conventional polarization filtering (PF) method. However, the conventional PF method is unable to address situations in which two barrage interferences with different polarization states are contained in the main lobe, because the polarizations of both interferences become complex. To filter dual-interference sources in the main lobe, a novel polarimetric filtering method is proposed in this letter. This novel method is based on polarization selection, which is implemented to suppress one of the dual-interference sources. The appropriate polarimetric parameters are first selected by a monopulse ratio constraint condition. Then, the spatial location of the other interference source can be measured. After searching the whole polarimetric domain, the spatial parameters of the two interference sources can be acquired by the polarimetric monopulse system. Finally, the waveforms of the interference signals can also be estimated during the filtering process. The results of a microwave chamber experiment demonstrate that this novel filtering method is effective.