Vector Network Analyzer Research Articles

A novel dielectric ceramic Na0·48La0·52MoO4 with excellent thermal stability for LTCC applications

This article reports the fabrication of a novel molybdate compound, Na0·48La0·52MoO4 (NLM), through the solid-state reaction method. The structural characterization and dielectric properties of NLM were conducted via powder X-ray diffraction, SEM, laser Raman spectroscopy, and vector network analysis. The research results indicate that the sintering temperature directly affects the firing process and microwave dielectric properties. NLM ceramics sintered at 920 °C demonstrate excellent microwave dielectric properties of εr = 8.86, Q × f = 61,378 GHz (at 13.5 GHz) and τf = −10.8 ppm/°C. Furthermore, NLM ceramics exhibit favorable chemical compatibility with Ag. These findings underscore the significant potential of NLM ceramics for utilization in LTCC applications.

Materials’ Properties of Lightweight Spiral Hybrid CNT/Epoxy Composites Enhanced Reflection Loss

Recently, various electronic devices have been developed to meet the requirements of higher frequency technology applications. This widely used application without realizing has created more electromagnetic interference pollution that is harmful to human health and other equipment. Therefore, more research interest focuses on fabricating the electromagnetic (EM) wave absorbing materials that can absorb the EM wave interference. In this regard, this research highlights the use of Iron Oxide and Cobalt Oxide as catalyst to synthesize hybrid CNT by using Thermal Vapor Deposition Tube (TVDT) method. The spiral hybrid CNT/epoxy composites were prepared at thickness of 1mm, 2mm and 3mm. The phase formation, microstructural, particle size and structural analysis of the hybrid CNT were analyzed by using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and RAMAN spectrometer respectively. The microwave characterization of the hybrid CNT/epoxy composite samples was analyzed by using Vector Network Analyzer (VNA) at GHz frequency range. The phase analysis confirmed the existence of Carbon and iron carbide in the sample. The microstructural of CNT formation are mostly in spiral and straight like structure. On the other hand, the structural analysis shows the sample are more towards defective structure with higher and broader D-band peak. This could enhance the EM wave absorption performance. The minimum reflection loss (RL) peak was ̴-23dB (t=3mm) obtained for all hybrid CNT composite samples. The differences of minimum reflection loss peak at different weight percentages are most likely shown by the shift of frequency range. Thus, this lightweight spiral hybrid CNT/epoxy composites results in better EM wave performance at different thin thickness used for different applications.

Phantom evaluation of electrical conductivity mapping by MRI: Comparison to vector network analyzer measurements and spatial resolution assessment.

To evaluate the performance of various MR electrical properties tomography (MR-EPT) methods at 3 T in terms of absolute quantification and spatial resolution limit for electrical conductivity. Absolute quantification as well as spatial resolution performance were evaluated on homogeneous phantoms and a phantom with holes of different sizes, respectively. Ground-truth conductivities were measured with an open-ended coaxial probe connected to a vector network analyzer (VNA). Four widely used MR-EPT reconstruction methods were investigated: phase-based Helmholtz (PB), phase-based convection-reaction (PB-cr), image-based (IB), and generalized-image-based (GIB). These methods were compared using the same complex images from a 1 mm-isotropic UTE sequence. Alternative transceive phase acquisition sequences were also compared in PB and PB-cr. In large homogeneous phantoms, all methods showed a strong correlation with ground truth conductivities (r > 0.99); however, GIB was the best in terms of accuracy, spatial uniformity, and robustness to boundary artifacts. In the resolution phantom, the normalized root-mean-squared error of all methods grew rapidly (>0.40) when the hole size was below 10 mm, with simplified methods (PB and IB), or below 5 mm, with generalized methods (PB-cr and GIB). VNA measurements are essential to assess the accuracy of MR-EPT. In this study, all tested MR-EPT methods correlated strongly with the VNA measurements. The UTE sequence is recommended for MR-EPT, with the GIB method providing good accuracy for structures down to 5 mm. Structures below 5 mm may still be detected in the conductivity maps, but with significantly lower accuracy.

A High-Performance, Low-Cost, and Integrated Hairpin Topology RF Switched Filter Bank for Radar Applications.

Switched filter banks find widespread application in frequency-hopping radar systems and communication networks with multiple operating frequencies, especially in situations demanding elevated filter element isolation. In this paper, the design and implementation of a highly isolated switchable narrow-bandpass filter bank architecture using hairpin microstrip topology is presented. The filter bank has four discrete bandpass filters with passbands of 2.0-2.2 GHz, 2.3-2.5 GHz, 3.1-3.3 GHz, and 3.9-4.1 GHz. These filters span the radar S-frequency band (2.0-4.0 GHz). In order to switch between channels with a switching speed of nanoseconds, low-loss and highly isolated SP4T switches are implemented. Advanced design system (ADS) software is used to design the various filter functionalities, and the entire system is tested on a vector network analyzer (VNA). The proposed architecture makes it much easier to put the filter bank into practice and switch it to the desired frequency, which is useful for radar receiver applications.

Dual-Planar Monopole Antenna-Based Remote Sensing System for Microwave Medical Applications.

Neurodegenerative diseases (NDs) can be life threatening and have chronic impacts on patients and society. Timely diagnosis and treatment are imperative to prevent deterioration. Conventional imaging modalities, such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET), are expensive and not readily accessible to patients. Microwave sensing and imaging (MSI) systems are promising tools for monitoring pathological changes, namely the lateral ventricle enlargement associated with ND, in a non-invasive and convenient way. This paper presents a dual-planar monopole antenna-based remote sensing system for ND monitoring. First, planar monopole antennas were designed using the simulation software CST Studio Suite. The antenna analysis was carried out regarding the reflection coefficient, gain, radiation pattern, time domain characterization, E-field distribution, and Specific Absorption Rate (SAR). The designed antennas were then integrated with a controlling circuit as a remote sensing system. The system was experimentally validated on brain phantoms using a vector network analyzer and a laptop. The collected reflection coefficient data were processed using a radar-based imaging algorithm to reconstruct images indicating brain abnormality in ND. The results suggest that the system could serve as a low-cost and efficient tool for long-term monitoring of ND, particularly in clinics and care home scenarios.

Impact of samarium on structural and dielectric properties of U-type hexaferrites synthesized by a sol-gel auto combustion route: Analysis of XPS, Raman and FTIR spectra

In this work, the impact of rare earth element samarium "Sm" substitution on Ba4Co2SmxFe36-xO60 U-type hexaferrites was studied in detail. Five compositions with step size x = 0.00, 0.025, 0.050, 0.075 and 0.1 were synthesized. These five series were prepared using the sol-gel auto-combustion method and the samples were sintered for 6 h at 1250 °C. The synthesized samples were characterized by XRD, FTIR, Raman Spectroscopy, X-ray photoelectron Spectroscopy and vector network analyzer (VNA). The structure crystallography of Ba4Co2SmxFe36-xO60 was examined via XRD. The impact of Sm3+ substitution was assessed across all lattice parameters. Lattice constants 'a' and 'c' were found between 5.886 and 5.881 Å and 113.179 to 113.037 Å, respectively. FTIR was used to learn more about the crystal structure and atomic vibrations between 400 and 1000 cm−1 wave number, where higher frequency bands appear at 570 cm−1 (tetrahedral site) and the lower frequency band occurred at 424 cm−1 due to the metal-oxygen stretching vibration (Fe-O) bond at the octahedral site. Each spectrum supported a U-type hexagonal structure i.e. an investigation of the chemical and intermolecular bonds via Raman spectra. XPS confirms the presence of elements in materials. Different dielectric parameters were observed in the 1 MHz to 6 GHz range of all prepared samples. Cole-Cole graphs of prepared materials highlighted the influence of grain boundaries. A solitary semicircle in the impedance of a specific section of grain boundaries was evidenced through Cole-Cole plots. Dielectric properties strongly depend on electron hopping between Fe2+ and Fe3+ ions. The optimized parameters suggest the utility of these materials in microwave devices, multilayer chip inductors and high-frequency electrical circuit applications to reduce skin effects.

Design and implementation of hybrid fed array antennae for Sub-6 GHz and 5G mm-wave communication and wireless applications

Abstract This paper proposes fractal-inspired array antennae for wideband applications. The proposed antennae have a resonance frequency range of 20–40 GHz. The modified fractal antennae are fabricated with a height of 1.6 mm, substrate width, and length of 100, 50, 25, and 18.75 mm2, and a simulated result shows that the gain is increased to 11.04, 11.9, 8.4, and 6 dBi, and the designed antennae radiate power with directivity of 11.3, 13.4, 9.29, and 7.17 dBi concerning proposed designs A, B, C, and D, respectively. The proposed antennae with 5G New Radio (NR) bands have more radiation concerning resonate frequencies in the 20–40 GHz range with Φ = 0°, Φ = 90°, and θ = 90°. Moreover, the bandwidths for applications covered in the 5G NR and sub-6G are 1.92, 0.73, 0.7, 2.4, 1.3, 5.3, and 1.26 GHz, and 3.4, 3.7, 2.67, and 4.65 GHz, and 2, 3.5, and 1.57 GHz, and 2.5, 1.5, and 1.0 GHz with the maximum return loss of 37 dB, 32.8 dB, 31.2 dB, and 23 dB with corresponding resonate frequencies as 21.5, 27.6, 33, and 27.6 GHz concerning designs A, B, C, and D, respectively. The proposed antennae have been implemented and validated using Computer Simulation Technology (CST), Vector Network Analyzer (VNA), spectrum analyzer, and power sensor.

Influence of 100 MeV 16O7+ ion irradiation on the structural, morphological, dielectric, and electromagnetic interference shielding properties of ferroelectric PVDF polymer

Polyvinylidene fluoride (PVDF), with β polymorph, is a versatile ferroelectric polymer in device fabrication. Its flexibility, lightweight, and ease of fabrication make it an alternative for electromagnetic interference shielding effectiveness (EMI-SE) improved through swift heavy ion (SHI) irradiation. For the first time, we modified PVDF thin films for EMI-SE applications, exposing them to a 100 MeV oxygen ion beam at varying fluencies. Our analysis encompassed investigating structural study, bonding interactions, surface morphology, and elemental analysis using X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), and Field Effect Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray Spectroscopy (EDS) respectively. Further, we measured dielectric response, cole-cole plot and EMI-SE in Ku-band (12–18 GHz) region using a vector network analyzer (VNA). The results revealed distinctive variations due to the deposition of 100 MeV oxygen ion beams, emphasizing the significant potential of irradiated PVDF thin films for EMI-SE applications. This study contributes to understanding the transformative impact of ion beam exposure on PVDF thin films and highlights their practical promise in emerging technological applications, particularly in EMI-SE.

Demonstration of a terahertz coplanar-strip spoof-surface-plasmon-polariton low-pass filter

There is a growing interest in spoof surface plasmon polariton (SSPP) structures at terahertz (THz) frequencies for applications such as filtering, sensing, and communications. However, to date, there are limited experiments that confirm SSPP characteristics at THz frequencies. The majority of literature focuses on simulation or verification by device scaling to Gigahertz (GHz) frequencies where standard vector network analyzers are readily available. This paper presents the first experimental verification of SSPP characteristics at THz frequencies in a guided wave system using coplanar strip (CPS) feedlines. Specifically, we design three SSPP structures with varying band-edge frequencies (1.04 THz, 0.63 THz, and 0.53 THz), then fabricate and verify the low-pass transmission characteristics using a modified THz-time-domain spectrometer (THz-TDS) system. We find strong agreement between simulation, theory, and experiment.

Electromagnetic and microwave properties of single-layer thermoplastic natural rubber (TPNR)/yttrium iron garnet (Y3Fe5O12)/magnetite (Fe3O4) composites backed by a perfect conductor

The use of a single-layer material for microwave applications continues to attract many researchers due to materials’ homogeneity in an acceptable range of thickness. This study outlines the microwave electromagnetic characteristics and interpretation of results based on a single-layer material backed by a perfect conductor. Data from three different laboratory prepared thermoplastic natural rubber (TPNR)/yttrium iron garnet (Y3Fe5O12)/magnetite (Fe3O4) composites were presented. The microwave relative complex dielectric permittivity (ε r*) and magnetic permeability (µ r*) were measured using a microwave vector network analyser (MVNA) in the frequency range of 0.1846–10.0104 GHz. The specular material model backed by a perfect conductor was used to obtain the frequency-dependent reflection loss (R L) assuming a normal incident of electromagnetic (EM) wave. The real and imaginary components of ε r* (ε r′ and ε r″) and µ r* (µ r′ and µ r″) for the three samples show a similar trend of frequency dependent. TPNR/Y3Fe5O12 reflected the EM wave less when its thickness (t) equals a quarter of the propagating wavelength (λ m/4) inside the material. Interestingly, in the presence of Fe3O4, multiple minimal reflections occur at smaller thicknesses (e.g. t = λ m/32). For both cases, this is the condition where the reflected wave at the surface of the material is in a 180°-phase difference from the wave reflected earlier at the material-conductor interface. Destructive interference occurs when these two waves meet and is visualized as the dip on the reflection loss (R L) vs. frequency plot. The number of dips increases with thickness. The lowest frequency dip occurs at a lower frequency for a thicker material. For TPNR/Y3Fe5O12/Fe3O4 and TPNR/Fe3O4, as the material gets thicker, the high-frequency dips on the R L plot become smaller and the use of the material in microwave application is no longer practical due to the increase in its weight and a smaller reflection loss.

Extending Copper Interconnects and Epoxy Dielectrics to Multi-GHz Frequencies.

Future multichip packages require Die-to-Die (D2D) interconnects operating at frequencies above 10 GHz; however, the extension of copper interconnects and epoxy dielectrics presents a trade-off between performance and reliability. This paper explores insertion losses and adhesion as a function of interface roughness at frequencies up to 18 GHz. We probe epoxy surface chemistry as a function of curing time and use wet etching to modulate surface roughness. The morphology is quantified by atomic force microscopy (AFM) and two-dimensional fast Fourier transform (2D FFT). Peel test and vector network analysis are used to examine the impacts of both type and level of roughness. The trade-offs between power efficiency and reliability are presented and discussed.

Fabrication of compact circular ring antenna loaded with Gd-YIG ferrites: Photon–magnon interaction

In telecommunications technology, transmitting and receiving signals is not possible without an integrated antenna. Recently, novel approaches of transmitting and receiving signals using advancement in quantum technology as “information coherent transfer” have been emphasized which overcomes the limitations of superconducting qubits. In the present investigation, a compact-sized circular-ring antenna was designed for a 12 GHz centre frequency. The antenna was topped with Gd(x)-doped YIG (x = 0.0, 0.1, 0.2, 0.3) thin disks to investigate its tunable operation over the tri-band (C to Ku) frequencies due to the photon–magnon coupling, which enables coherent qubit information transmission from an electromagnetic (EM) carrier to the magnons. The proposed prototype of the antenna is validated using HFSS simulation. To characterize the frequency tunability of the designed antenna, we measured the return loss (S11) via a vector network analyzer as a function of dc magnetic field. Different concentrations of Gd-doped YIG ferrites (Gdx-YIG) have been loaded on ring antennas to observe strong anti-crossing phenomena with the application of an external magnetic field. The designed antenna has a tunability of around 300% for a small applied magnetic field up to 3.7 kOe. The maximum gain of dual resonance antenna is 1.4 for higher magnetic field of 3.7 kOe. The highest efficiency and lowest bandwidth of 30% and 14% respectively, for Gd0.1-YIG disk are observed. The measured normal mode splitting spectrum as a function of bias magnetic field that gives the maximum coupling strength is 153 MHz for a Gd concentration of 0.1. For practical applications, such antennas are suitable for use in tunable tri-band or multi-band applications (C to Ku).

Different morphologies of super-balls obtained to form photonic crystals of cholesteryl benzoate liquid crystals.

The current study highlights the synthesis and characterization of some nanocomposite materials formed by polymer particles and liquid crystals. The liquid crystals used were cholesteryl benzoate (CLB), and the particles were synthesized by emulsion polymerization in the absence of the emulsifier. Through SEM and DLS analysis, the synthesis of particles of the same size was emphasized, and the amount of CLB showed no influence on these parameters. The lack of signal for CLB in the case of DSC and XRD analyses for the sample with the smallest amount of liquid crystal is attributed to the detection limits of the devices. To complete the surface characterization of the particles, XPS analysis was performed. Through XPS it was underlined that in the case of the smallest amount and the largest amount of CLB, respectively, it is encapsulated in the polymer particles, unlike the case of the average amount used, in which core-shell type morphologies have been obtained. For the electrical characterization of the samples, a Vector Network Analyzer (VNA) connected to two rectangular X-band (i.e., 8.2-12.4 GHz) waveguides through coaxial cables was used.

In silico, in vitro, and in vivo validation of a microwave imaging system using a low‐profile Ultra Wide Band Archimedean spiral antenna to detect skin cancer

AbstractMicrowave imaging (MI) is a noninvasive and nonionizing procedure for detection of cancerous cells in healthy body tissues using radiofrequency (RF) and microwaves. The procedure involves the use of Ultra Wide Band (UWB) antennas for sensing purposes. Therefore, this research article presents the design, development, and testing of a low‐profile UWB Archimedean spiral microstrip‐patch antenna (ASMA) for detection of skin cancer using monostatic radar‐based microwave imaging. The proposed ASMA consists of a spiral resonator with a defective ground structure and a slotted microstrip feed line with dimensions of 38 × 38 × 0.87 mm3. The proposed antenna shows an impedance bandwidth for the frequency range of 2.2–13.9 GHz, with a peak gain of 6.8 dB at 7.8 GHz. In silico analysis of the proposed ASMA for MI is carried out with Gaustav model using Computer Simulation Technology Microwave Studio. To validate the performance of the ASMA as a sensor for MI, a prototype of the same is fabricated and a four‐layered bio‐phantom of the human forearm is prepared for in vitro and in vivo testing of the proposed procedure. The validation of ASMA radiation properties is done using a Vector Network Analyser (E‐5063A) (VNA) and an anechoic chamber with the fabricated antenna at 10 mm away from the prepared bio‐phantom. The recorded S parameter data with bio‐phantom and the VNA is processed using different beamforming algorithms like Delay and Sum and Coherent Factor‐Delay Multiply and Sum (CF‐DMAS) to reconstruct the image of the scanned area. The reconstructed images are 97%–98% accurate. The proposed ASMA sensor is also safe for human exposure as it has a specific absorption rate of 0.0546 W/Kg at 5 GHz that complies with the safety guidelines of the Federal Communications Commission to minimize potential health risks associated with exposure to RF and microwave radiation.

Discovery of electromagnetic polarization in Asian rice wine deterioration process and its applications.

Rice wine, known as yellow wine in China and Japan, possesses considerable nutritional value and holds significant global influence. This study addresses the challenge of preserving rice wine, which is prone to rancidity due to its low alcohol content. Conventional storage techniques employing pottery jars often result in substantial spoilage losses. Through rigorous investigation, this research identifies a polarization phenomenon exhibited by degraded rice wine when subjected to high-frequency microwaves(>60GHz), presenting a pioneering method for detecting spoilage, even within sealed containers. Employing a multi-channel microwave radar apparatus, the study delves into the susceptibility of rice wine to electromagnetic waves across various frequencies, uncovering pronounced polarization traits in deteriorated samples within the E-band microwave spectrum. Furthermore, lab-controlled simulations elucidate a direct correlation between physicochemical alterations and high-frequency Radar Cross Section (RCS) signals during the wine's deterioration process. A novel six-membered Hydrated Cluster hypothesis is proposed, offering insights into the molecular mechanisms underlying this phenomenon. Additionally, dielectric property assessments conducted using vector network analyzers (VNA) reveal noteworthy enhancements in the dielectric constant of deteriorated rice wine, particularly within the high-frequency domain, thereby augmenting detectability. These findings carry implications for refining rice wine preservation techniques and contribute to the advancement of non-destructive testing technologies, enabling the detection of rice wine deterioration or indications thereof, even within sealed vessels.

Ultra‐wideband imaging with an improved backward projection algorithm for far‐field applications

AbstractUltra‐wideband (UWB) radar imaging is widely used in penetration detection, target location and detection, and vital monitoring because of its high interference immunity and excellent target recognition with high resolution. In this paper, we report the design of a UWB stepper radar imaging system by using a vector network analyzer and a specially designed novel Vivaldi antenna for far‐field imaging applications. An anti‐attenuation backward projection (AA‐BP) algorithm is proposed to alleviate the attenuation impact of electromagnetic wave propagation. The AA‐BP algorithm and the specially designed Vivaldi antenna are jointly applied in our experiments on multiple targets through wall imaging in both free space and multiple‐path propagation environments. The experimental results show that our reported imaging system achieves desirable performances of far‐field imaging.

Исследование влияния конструкции антипараллельной пары диодов с барьером Шоттки на потери преобразования гармонического смесителя 3-мм диапазона

This paper presents the design and principle of operation of a passive harmonic mixer in the 3-mm range (75-110 GHz), the active element of which is an antiparallel pair of Schottky barrier diodes (SBD). A theoretical analysis of the mixer operation was carried out. A technique for measuring conversion losses using a vector network analyzer is presented. The experimental results of a study of the dependence of the conversion losses of a harmonic mixer on the design of an antiparallel pair of DBSs are presented. The variable parameters of the antiparallel pair of diodes were the distance between the anode leads, the length of the anode lead and the diameter of the Schottky barrier contact. The dynamic range of the mixer is investigated.

Design, Development and Characterization of Indigenously Developed High Temperature Black Body Source for Calibration of ECE Diagnostics

The design, development, and characterization of a Silicon Carbide (SiC) based hightemperature black body source at 600 ºC for Electron Cyclotron Emission (ECE) measurements has been done. The design has been optimized for higher emissivity performance in 65-140 GHz frequency range using CST Microwave Studio. The innovative design features a pyramid-based structure, incorporating a heater and emitter surface, integrated with an electrical control system. The improvement in emissivity with variation in pyramid slant angle was analysed. The design was refined to ensure surface temperature consistency within a range of ± 15 ºC and rapid heating, taking less than 60 minutes to reach 600 ºC from room temperature. The developed black body calibration source was thermally characterized using IR camera for different set of temperatures and mean temperature distribution was determined. The microwave characterization of the calibration source has been performed in 65–220 GHz frequency range using Vector Network Analyser (VNA) and reflectivity of more than 20 dB has been obtained. The results highlight the synergy between advanced design methodologies, and precise engineering, leading to the development of an efficient SiC-based black body source. This research work not only contributes significantly to the field of engineering but also paves the way for enhanced accuracy and reliability in ECE measurements.

THE EFFECT OF MOISTURE CONTENT ON ELECTRICAL PROPERTIES OF SELECTED SOFTWOODS; CEDAR, JUNIPER, AND PINE

Natural woods as a raw material have been taking a considerable interest topic by industries such as the forest industry, furniture manufacturing, and nowadays suitable electronics. One of the most essential steps of manufacturing for those industry purposes is RF heating/drying of raw wood material nowadays. However, knowing the electrical properties, such as the dielectric constant of wood-based material before processing is tremendously important. It is well-known that the moisture content and density levels of material directly affect the dielectric properties. Moisture and density conditions are different in each material because it’s related directly to the absorption and affection of material towards moisture sources. Therefore, in this study of wood material under varying conditions, proper empiric models have been generated to express this relationship. This study is based on three different softwood specimens widely used in the forest industry. The dielectric properties were determined in the frequency range of 2.17 GHz-6.0 GHz as a function of moisture content and density for wood species. Each measurement contains 500 raw data points; a vector network analyzer collected 49,500 S-parameter data. Each wood specimen consists of six samples; the average of data obtained from these samples was considered as a dielectric measure for the examined wood specimen. The proposed empiric models have RMSE better than 0.05 for the relation between loss tangent and density, while the proposed empiric models for dielectric permittivity have better than 0.90 with density relation, which is considered an acceptable ratio for model generation.

Evaluation of Random Errors for Vector Network Analyzers Based on a Residual Model

Evaluation of Random Errors for Vector Network Analyzers Based on a Residual Model