Vector Network Analyzer Research Articles

Design, Simulation, and Fabrication of a 500 kV Ultrawideband Coaxial Matched Load and Its Connectors for Fast Transient Pulse Measurement Systems

In the past few decades, Pulsed Power (PP) has been one of the fastest growing technologies, with more and more systems frequently emerging in domains such as civil, medical and military. These systems are based on high-voltage pulses, up to several hundreds of kilovolts, with temporal parameters ranging from microsecond levels to sub-nanosecond levels. One of the biggest challenges in this technology is the accurate and precise measurement of the generated PP. The PP measurement systems must possess high-voltage and wideband properties simultaneously, which is often conflicting. The central elements of a PP measurement system are a voltage divider and a termination load. The work presented in this article is dedicated to the second element of the PP measurement system. This paper describes the development of a 50 Ω coaxial termination load and its connectors for a high power ultrawideband (UWB) pulse measurement systems. The principle roles of these devices are to serve as a dummy matched load for the former and to facilitate the connections between different components of the pulse measurement system for the latter. These devices are designed to withstand pulse voltage amplitudes at least up to 500 kV with temporal parameters, such as rise time and pulse duration, varying from nanosecond to sub-nanosecond ranges. The main challenge in the development of a high-voltage UWB termination load is the tradeoff between the high-voltage and wideband characteristics, both of them requiring opposite dimensional aspects for the load device. This challenge is overcame by the special exponential geometry of the load device. The design employs a 30 cm long low-inductance tubular ceramic 50 Ω resistor, enclosed in a critically dimensioned shielding conductor of an exponential inner profile. This shrinking coaxial structure makes it possible to maintain a good level of matching all along the 50 Ω load. The results obtained through 3D electromagnetic modeling and vector network analyzer measurements show good agreement and confirm the reflection coefficient below −27 dB up to at least 2.5 GHz for the load device. Moreover, calculations demonstrate that the load device is very well adapted for nanosecond and sub-nanosecond pulses with voltage peaks as high as 500 kV. These results demonstrate the high-voltage and UWB properties of the developed load device and prove the utilization of this device in the measurement systems for the accurate and precise measurements of the PP.

Microwave Absorption Performance of One-dimensional Mixed Metal Oxide Nanocomposite

Abstract: Microwave-absorbing materials have received numerous attentions in terms of their key roles in the fields of stealth technology and controlling electromagnetic radiation pollution. In this paper, we aim to develop one-dimensional CoFe2O4-TiO2 mixed metal oxide nanocomposite via combination of sol-gel method and electrospinning technique. and investigate its microwave absorbing capability. The phase evolution from precursor fiber to final product and corresponding micromorphology are characterized, and microwave absorption performance for different CoFe2O4-TiO2 composite fibers are investigated with a vector network analyzer in 2-18 GHz. The prepared CoFe2O4-TiO2 mixed metal oxide composite fibers exhibit excellent microwave absorbing ability. The low reflection loss can reach -32.8 dB, and the maximum effective bandwidth is up to 6 GHz (12-18 GHz) at the thickness of 4 mm. The results further reveal that the lightweight mixed metal oxide composite fiber is promising for applications in electromagnetic attenuation and other related research fields.

Microwave-assisted alkali treatment of sisal fiber for fabricating composite as non-structural building materials

Currently, the world needs sustainable materials to replace and minimize the use of synthetic materials in order to reuce environmental pollution. In this context, natural fiber-reinforced composites (NFRCs) are in high demand. However, the low thermal and mechanical properties have limited their application spectrum. The current research investigation explores the effectiveness of alkali treatment and microwave-assisted alkali treatment (MAAT) on sisal fiber and sisal/high-density polyethylene (HDPE) composites. The MAAT was performed at three different power levels (300, 640 and 800 W) and treatment time was kept constant (10 min); the power level was optimized based on the fiber’s performance. The chemical analysis of treated fibers showed an increased ratio of cellulose percentage in the fibers when compared to untreated fibers. The MAAT (at 640W10) showed improvement in the thermal stability of sisal fiber as compared to untreated and alkali treated fibers. The single fiber test showed the highest (21.92% and 45.77%) increase in tensile strength for MAAT (at 640W10) as compared to alkali treated and untreated sisal fibers, respectively. Scanning electron microscopy (SEM) showed the effectiveness of the MAAT (at 640W10) in terms of a more uniform surface roughness on the fiber surface. The research also focused on using time efficient microwave-assisted molding (MAM) method for the fabrication of NFRCs. Vector network analyzer (VNA) was used to determine the dielectric constant of the fibers as it plays a critical role in heat generation during microwave heating. Mechanical, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) tests were performed on the fabricated composites. It was observed that the MAAT sisal fiber (at 640 W) reinforced HDPE composites (640W10/HDPE) had recorded the best performance as they showed increased thermal stability, percentage crystallinity (3.56% and 10.26%), tensile strength (14.93% and 32.04%) and flexural strength (10.28% and 28.60%) as compared to alkali treated sisal fiber reinforced HDPE composites (NTSF/HDPE) and untreated sisal fiber reinforced HDPE composites (USF/HDPE), respectively. From the results, it is observed that MAAT has strong potential to be commercially employed for the time-efficient treatment of natural fibers before fabricating the sustainable construction components, parts, and products.

Hybrid nanofillers loaded epoxy resin; Synthesis, characterizations, and dielectric spectroscopy

In the current work, synthesis, structural, magnetic, and dielectric characterization of nanofillers doped epoxy composites were studied deeply. Bisphenol A-(epichlorohydrin): epoxy and hardener N(3-dimethylaminopropyl)-1,3-propylene diamine was used to prepare epoxy composite and nano epoxy composites. (CoFe2O4 + Fe3O4), and (NiFe2O4 + CoFe2O4) hybrid nanofillers were used as nanofillers. The structural information of neat epoxy and nano-epoxy composites was obtained by XRD. To understand the actual chemical changes, the nature of bonding and interaction mechanism between the nano-particles and the neat epoxy; the structural chemistry and surface functionality of nano-epoxy composites were examined through Fourier transform infrared spectroscopy (FTIR). Moreover, vibrational sample magnetometer (VSM) measurements were done to gain additive information about the magnetic properties of nanoparticle-loaded epoxy composites. Dielectric spectroscopy measurements of nano epoxy composites were carried out using a precision LCR meter in the frequency range of 1 kHz to 2 MHz and with the help of a vector network analyzer along with SPEAG dielectric assessment kit for thin layers over the frequency range of 200 MHz to 20 GHz at room temperature. The influence of nano-fillers on the dielectric properties of neat epoxy composites is discussed thoroughly.

A Sub-6 GHz Switching System for Simultaneous Use of 2-Port Network Analyzer by 4 Users

A vector network analyzer (VNA) is an expensive and essential device for measuring the scattering coefficients of RF devices in the research and development of microwave systems. However, these VNAs are limited in that they can be only used by one user. To address this limitation, this paper presents a switching system that allows multiple users to measure each device under test using a single VNA at the same time. In particular, a four-user switching system is developed in this study. It is important to calibrate the differences between each channel that inevitably arise during implementation. For calibration, we propose and implement a technique for de-embedding the uneven characteristics between these channels. Its performance is validated by measuring insertion loss, reflection loss, and isolation for the developed switching system.

Development of double-layer metamaterial with high effective medium ratio values for S- and C-band applications

This study introduces a compact double negative metamaterial (DNM) composed of three split rings connected slab resonator (TSRCSR) based double-layer design with a high 13.9 EMR (effective medium ratio) value. A double-layer patch is introduced to achieve the novel double negative properties, including negative behaviours of effective medium parameters, including refractive index, permittivity, and permeability with a high effective medium ratio for the miniaturised size of the introduced unconventional material that is highly suitable for microwave S and C band covering applications. The popular low-loss Rogers RT5880 (thickness 1.575 mm) substrate and copper resonator materials are utilized to develop the metamaterial unit cell that offers triple resonance between frequencies from 1 to 8 GHz. Therefore, the proposed metamaterial exhibits resonance peaks at 2.75, 5.2, and 6.3 GHz, suitable for radar, communication satellite, and long-distance telecommunication applications, respectively. The commercially available simulator known as Computer Simulation Technology (CST) is adopted to develop and simulate the 8 × 8 mm2 metamaterial design. The simulation results of the introduced TSRCSR design structure were verified by adopting the Ansys High-Frequency Structure Simulator (HFSS). Furthermore, it was then proved with the help of equivalent circuit model findings gained from the Advanced Design Structure (ADS) software. On the other hand, the analytical results were further validated by measuring the TSRCSR design utilizing a Vector Network Analyzer (VNA). These analyses become one of the novelties of this work, where the compact TSRCSR metamaterial successfully gained small discrepancies in transmission coefficient values when compared to both analytical and measurement results. The proposed metamaterial is highly suggested for communication devices for its extensive effective characteristics and compactness.

Identification of damage and corrosion effect in aging aircraft data transmission lines

Corrosion in aircraft structures and systems persists to pose significant problem in the aircraft industry. It affects both the aircraft structures and all the wiring systems including data transmission lines at the points of mechanical damage (missing or damaged insulation and jacket materials) and connections. Reliability of data transmission through aircraft data transmission lines (ATDL) is essential for maintaining performance capability and safety of flights. Unfortunately, there is no existing method for detecting corrosion and predicting its effect for wiring systems including ADTL. Detecting corrosion and predicting its effect on time would prevent unexpected system failures and catastrophes. This paper presents novel experimental method that has been employed, for the first time, to detect and study the effect of localized corrosion process on reflected and transmitted power signals passing through locally corroded ADTL with mechanically induced damage. ADTL with three types of induced damage were corroded in a Q-Fog cyclic accelerated corrosion chamber for over 14 weeks (2352 h) using ASTM G85-A5 Prohesion test that resembles the environment of aircraft operation. Cable specimens were taken out every week and investigated by measuring transmitted and reflected power signals passing through the corroded ADTL using Vector Network Analyzer (VNA), where signals from 0 to 6 GHz were swept into the ADTL. Reflected and transmitted power signals (S11 and S21 respectively) were acquired in time domain and processed in MATLAB. Analysis of results show that corrosion effect is not arbitrary and can be tracked over time and predicted. Reflected signal peak width changed over time of corrosion exposure and is proportional to corrosion propagation width inside the ADTL. It is also observed that corrosion induced extra distortion of signals passing through the corroded damage region. The results are very promising for detecting corrosion and predicting its effect in ADTL.

Mineral composition, crystallinity and dielectric evaluation of Bamboo Salt, Himalaya Salt, and Ba’kelalan salt content

The mineral composition, crystallinity, and dielectric properties of salts can provide valuable insights into the quality and suitability of different types of salt for various applications. In this study, comprehensive analysis of the X-Ray Diffraction (XRD), X-ray fluorescence (XRF) and dielectric analysis of the Ba'kelalan salt, Himalaya salt and Bamboo salt have been investigated. The mineral composition of these salts, encompassing vital elements such as iodine and other trace minerals, significantly influences the salt's nutritional profile and overall excellence. Nonetheless, gauging the dispersion and density of these minerals poses difficulties due to conventional techniques that can be arduous, damaging, and expensive. Sample preparation is carried out before conducting X-ray diffraction (XRD), X-ray fluorescence (XRF), and dielectric analysis. XRD measurements are performed using the Bruker D2 Phaser to identify crystalline material phases. XRD operates on the principle of constructive X-ray interference within crystalline samples. For elemental analysis across a broad spectrum of materials, XRF is employed. Elemental peaks are scanned, starting from the lowest to the highest angle of incidence. The X-ray intensity at characteristic peaks is compared to the standard series. Dielectric spectroscopy analysis examines the dielectric behaviour of Ba'kelalan salt, Himalaya salt, and Bamboo salt. The setup involves a vector network analyser (VNA) paired with an open-ended coaxial probe, utilizing the microwave method. This approach ensures rapid, efficient, and non-destructive measurements of dielectric constants (ε′) and loss factors (ε”). The dielectric permittivity spectra are acquired within the frequency range of 4 GHz–20 GHz. ε′ of these salts increase with frequency. Meanwhile, ε” seem varies insignificantly over frequency. Mineral contents and crystallinity are the crucial factors lead to these responses. Based on the study, the quality and suitability of the selected salts for specific applications can be determined by considering their mineral composition, crystallinity, and dielectric properties in the context of the intended use. This gives an insight for some applications that may benefit from certain minerals or crystalline structures, others may require specific dielectric properties for effective use. Therefore, understanding these properties allows for decision-making in choosing the right type of salt for a given purpose, whether it's for foods, medical, industrial, healthcare, and technological applications.

Microwave heating characteristics of cement mortar containing carbonyl iron powder applied to airport pavement deicing

To improve the microwave deicing efficiency of airport concrete pavement, carbonyl iron powder (CIP) was used as an absorbing material to prepare the microwave-absorbing cement mortar. Firstly, to characterize the microwave absorption ability of the mortar, its electromagnetic (EM) parameters and microwave reflection loss (RL) with different CIP content were investigated by using the coaxial vector network analyzer (CVNA) and arching reflected method, respectively. Then, the microwave heating rate and deicing efficiency of the mortar coated with ice was investigated under different icing temperature and ice layer thickness conditions with a microwave heating frequency of 2.45 GHz. Finally, the mechanical strength of mortar after deicing was tested to analyze the effect of an icing-deicing cycle on its engineering performance. The results showed that at the total frequency band, the mean RL and effective bandwidth of 10CCM was −2.8 dB lower and 1.6 GHz wider than that of the control group. Meanwhile, at 2.45 GHz, the RL of 10CCM was 1.31 times lower than that of the control group. When the icing temperature and ice layer thickness were − 10 °C and 1 cm, the heating rate of 10CCM was 1.34 times higher than that of the control group. Compared to the icing temperature, the changes in ice layer thickness on the mortar surface had less effect on its heating rate. After deicing, the CIP mortar still had favorable mechanical strength. Hence, the CIP was a favorable absorbing material that could be applied to cement mortar to improve the microwave deicing efficiency of the concrete pavement during long-term service.

Fe30Co70/Co/CoxFe3−xO4-δ nanocomposite with multiple magnetic exchange resonance mechanisms and large magnetic loss available for microwave absorption application

Soft magnetic alloys are widely studied and reported as a type of important microwave absorption (MA) materials, while their magnetic losses are limited. In this paper, a multiphase composite strategy of the soft magnetic alloys, hard magnetic metals, and hard magnetic ferrites is adopted for increasing the magnetic loss. Then, three-phase Fe50Co50/CoxFe3−xO4-δ/γ-Fe2O3 (FC31), three-phase Fe30Co70/Co/CoxFe3−xO4-δ (FC22), and three-phase CoxFe3−xO4-δ/Co3O4/Co (FC13) nano-composites are prepared by a simple thermal decomposition process of FeC2O4 and CoC2O4 in vacuum. The crystal structure, surface composition, vibration of chemical bonds, morphology, micro-structure, and static magnetism are characterized by XRD, XPS, FTIR, Raman, SEM, TEM, and SQUID, respectively. The electromagnetic (EM) parameters are measured in 2–18 GHz by a vector network analyzer. Based on the measured EM parameters, the calculated magnetic loss tangents (tanδm) are over 0.5 in a wide frequency band of 8–18 GHz for the FC22/paraffin absorber, showing that the tanδm can be increased dramatically through the multiphase composite strategy. Benefiting from the increased tanδm, an effective absorption bandwidth of 7.0 GHz is achieved for the FC22/paraffin absorber at a thin thickness of 1.45 mm, exhibiting great application advantages in the MA field.

PREPARATION AND PROPERTIES OF SiO2/Ag MICROBEADS USING ELECTROLESS PLATING METHOD

SiO2/Ag microbeads were synthesized using the electroless plating method by changing the addition order and the mixed method of electroless plating. Conducting composites were prepared using the prepared SiO2/Ag microbeads and unsaturated polyester resin as the fillers and substrate, respectively. The microstructure and properties of the prepared microbeads and composite were characterized with a scanning electron microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), particle size analyzer, DC milliohm meter and vector network analysis tester. Results show that the SiO2/Ag microbeads prepared with the reverse dropping electroless plating method achieved the best uniformity and integrity of the silver coating on the surfaces of glass beads, and its compaction resistance reached 138.80 mΩ·cm. When the ratio of the prepared SiO2/Ag microbeads and unsaturated polyester resin was 1:2, the obtained coating composite had a resistivity of 2.79 × 10–5 Ω·cm, showing good electromagnetic shielding performance.

Design of a Compact Microstrip Filtenna for Miniaturized Devices to Access Internet of Things Using Long Term Evolution

A filtenna or filtering antenna has both radiation and filtering functions and is an important module for the RF front-end of wireless devices. The main function of a filtering antenna is to filter out the out-of-band interferences from the adjacent bands. In this paper, the design of a compact coplanar microstrip filtering antenna at 2.6GHz band is presented. The antenna is designed for the miniaturized devices for the city connectivity to access the internet of things (IoT) services over 2.6GHz long term evolution (LTE) gateways. Filtering antenna is designed using hairpin bandpass filter integrated with semi-circular microstrip antenna. Filtering antenna is designed by computer simulation technology (CST) software and measurements are performed by vector network analyzer. Good impedance matching at 2.6GHz band is obtained for the filtering antenna by choosing appropriate dimensions of the hairpin bandpass filter. The simulated 10dB return loss bandwidth of filtering antenna is 4.65% with maximum gain of 1.9dB. Measured and simulated results agree well for the semi-circular filtenna.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

Design and Development of RF Window for Gyro-TWT

In this paper, the electrical design of an RF quartz window for a Ka-band Gyro-TWT amplifier has been carried out using CST microwave studio. The return loss (S11) and insertion loss (S12) of the RF quartz window have been −35.3 dB and −0.02 dB, respectively. The thermal design of the RF quartz window for Gyro-TWT during extreme cases of operation, i.e. at saturation has been carried out using ANSYS software and as discussed in the paper. The temperature 368 K on the disc of the RF window for Gyro-TWT has been obtained. The RF quartz window for the Ka-band Gyro-TWT amplifier has been developed. The cold characterization of the RF quartz window for the Ka-band Gyro-TWT amplifier has also been carried out using a Vector Network Analyzer. A good agreement between simulation and measurement has been obtained.

Tunable and wideband high-performance rare earth-doped Ni-Mg-Cu-Zn nano ferrite-based meta-absorbers for C-band application

Due to advanced technology, electromagnet interference and dissipation problems in the electronic and portable devices at GHz range are increasing daily. Magnetic absorbing materials with outstanding electromagnetic properties, wide bandwidth, and strong absorption are highly desirable. The present investigation deals with the preparation of Ni-Mg-Cu-Zn (NMCZ) substituted nano ferrites with composition of Ni0.3Mg0.2Cu0.3Zn0.2X0.02Fe1.98O4 (X = Nd, Ho, Pr, Gd, Yb). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), a vibratory sample magnetometer (VSM), and a Vector network analyzer (VNA) were used to investigate these rare earth-doped nanocrystalline ferrites' features. XRD reveals the single spinel phase structure in all Ni-Mg-Cu-Zn ferrites. FTIR spectroscopy shows the presence of tetrahedral and octahedral bands of spinel ferrites. FESEM images reveal the lowest agglomeration for the Ho-doped NMCZ nano-spinel ferrites sample. TEM images show the hexagon shapes of the Yb- and Nd-doped NMCZ ferrites. Pr-doped NMCZ ferrites show more coercivity than other rare earth metals substituted NMCZ nanocrystalline ferrites. VSM analysis was used to calculate the magnetic features like initial permeability, magnetic anisotropy constant, remanence, coercivity, and magnetic moment. High-frequency switching field distributions (SFD) analyses were also investigated. Magnetodielectric characteristics such as losses, permittivity, modulus, Q, ac conductivity, and impedance of the Nd-, Ho-, Pr-, Gd-, Yb-doped Ni-Mg-Cu-Zn ferrites were evaluated. The minimum reflection loss (–57.3 dB) is found at 1.4 GHz for Pr-doped Ni-Mg-Cu-Zn ferrite absorber. However, the reflection loss (RL) of –53.9 dB at 2.9 GHz is observed for Ho-doped Ni-Mg-Cu-Zn ferrite absorber. Soft magnetization, low coercivity, outstanding magnetodielectric, and absorption properties of the Nd-, Ho-, Pr-, Gd- and Yb-doped Ni-Mg-Cu-Zn ferrites are suitable candidates for absorption in telecommunication, defense, and technological industries.

Error Vector Magnitude as a Performance Standard for Antennas in the Millimeter-Wave Era: Part 2: Modeling, simulation, and measurement methods

The error vector magnitude (EVM) is a comprehensive measure of the amplitude and phase distortion of digitally modulated signals and a potential tool for characterizing the performance of active beamforming arrays, especially at millimeter-wave frequencies, because of the high level of integration and limited spacing between the radiating elements. A review of the EVM measurement process and fundamental principles for time-domain demodulation with a vector signal analyzer (VSA) and spectral correlation with a vector network analyzer (VNA) was presented in [1]. This article demonstrates how researchers have modeled and measured impairments from antenna and phased array signal transmission to characterize their influence on the EVM of single and multicarrier digital signals. It presents examples of simulation models and measurements of the distortion from ultrawideband (UWB) passive antenna transmission, power amplifier (PA) nonlinearities, and phased array beam squint and beam scan intersymbol interference (ISI). A brief survey of over-the-air (OTA) test ranges for EVM analysis is also provided. This overview of state-of-the-art EVM simulation and measurement methods is intended to help interested readers understand and enhance the EVM performance analysis methods applied to antennas and phased arrays in this new era of millimeter-wave communications.

Synthesis BaFe12O19/RGO Composite As Microwave Absorber For Ku-Band

In this study, a composite microwave absorber consist of barium hexaferrite (BaFe12O19) and Reduced Graphene Oxide (RGO) for Ku-band (12-18 GHz) was prosperous blend. Barium hexaferrite to arrange using the sonochemical method and at calcination temperature of 1000°C and a holding time of 1 hour. Subsequently, commercial RGO was composited with barium hexaferrite at a weight percentage of 6% RGO. The synthesized composite was characterized using X-Ray Diffraction (XRD) to analyze the formed phases, Raman Spectroscopy to confirm the presence of RGO in the composite, and Vector Network Analyzer (VNA) to evaluate the microwave absorption performance. The XRD test results show that there is no change in the crystal structure of barium hexaferrite due to the addition of RGO. The VNA test results showed that the addition of RGO could enhance the reflection loss value of barium hexaferrite. The BaFe12O19/RGO compound displayed a reflection loss value of -14.43 dB at a frequence of 16.50 GHz.

Nexus between inflation and inflation expectations at the zero lower bound: A tiger by the tail

Ultra-low policy rates and zero lower bounds (ZLB) have been major issues for monetary policy formulation. In this context, we investigate the nexus between inflation and inflation expectations. Employing a non-linear ADRL framework on UK and Canadian datasets, we find significant asymmetries in the nexus among inflation and inflation expectations and their determinants, including labour market slack, output gap, oil shocks, fiscal deficit and exchange rates. Heterogeneities are explicit in the short and long-term as well as in the pre-and post-ZLB regimes. Inflation and inflation expectations become more responsive to their determinants as key policy rates approach the ZLB. There is strong evidence of persistence in inflation and inflation expectations in both regimes manifesting the importance of keeping expectations well anchored. Robustness testing with Time-Varying Parameter Vector Auto-Regression and Network Analysis confirms our findings. To mitigate the persistence of a high inflation regime, it would be vital to keep the inflation expectations well anchored.

Wearable microstrip patch antenna with low SAR for WBAN applications

The development of intelligent textile systems to raise the degree of protection for the wearer has revealed the need for wearable communication devices and motivated research in textile antennas. In this paper, a new fully textile microstrip patch antenna is designed for a central frequency of 5.8 GHz. a substrate made of polyester and cotton with a dissipation factor of tan = 0.02 and a dielectric constant of 1.6 was employed. Thanks to its high conductivity (0.02 Ohm/cm), the Stick E shield was chosen as a conductor material. The CST simulator version 2018 is used to simulate the suggested conception, and measured by Vector Network Analyzer Master MS2026C, the HFSS software was employed as a comparative tool. For wearable situations in the free medium and on the human body, promising results from simulation and experimental studies are presented. The suggested antenna might possibly be connected to the human body, requiring the calculation of the specific absorption ratio (SAR).Thus, the proposed antenna design permits to attain 0.087 W/kg for 1 g. SAR and 0.0321 W/kg for 10 g. Experimental and numerical results demonstrate excellent performance regarding return loss, VSWR. Finally, our results indicate that the suggested antenna performs as intended when situated within the vicinity of the human body, making it a good candidate for application in wearable technologies.

13…67 GHz Frequency Mixer

Introduction. The requirements for the performance of measuring devices, including their operating frequency, are constantly becoming stricter. This encourages the creation of wide-band microcircuits for application in microwave blocks of devices, such as vector network analyzers (VNA) and spectrum analyzers (SA). One of such microcircuits, used in the receiver system, is a frequency mixer. The operating range of the mixer determines the operating range of the measuring instrument. Aim. Research and development of an ultra-wideband integrated circuit for a 13…67 GHz frequency mixer based on the GaAs QSBD technology by Micran JSC. Materials and methods. An analysis of existing classic and modified circuit transformers used in mixers was conducted. A modification of the transformer circuit, which allowed a frequency range of 10…70 GHz to be achieved,was proposed. Based on the obtained transformer and GaAs diode technology of Micran JSC, a complete mixer topology was developed and produced. An electrodynamic analysis of the integrated circuit was carried out; measurements were performed using a VNA up to 67 GHz. Results. A wideband mixer with a frequency range of 10…67 GHz is developed. A circuit design is proposed based on a balanced circuit with modified transformers and an intermediate frequency output circuit. The calculated dependences and measurement results of the integrated circuit of the mixer are presented. The mixer exhibits a conversion loss of less than 10 dB in the range of 10…67 GHz. Conclusion. A new broadband transformer with a range of operating frequencies from 10 to 70 GHz was developed. On its basis, a mixer microcircuit was simulated and manufactured. This microcircuit can be used in the receiving and transmitting units of modern measuring instruments. In terms of its characteristics, the proposed microcircuit is an analog of the Marki Mikrowave MM1-1467L mixer.