Scalar Network Analyzer Research Articles

Analytical Study of a Rectangular Microstrip Patch Antenna

This work presents the analytical study of a rectangular microstrip patch antenna design which is developed on FR4 type substrate material. The resonant frequency of this rectangular microstrip patch antenna is first estimated using Transmission Line Model (TLM) and Cavity Model (CM) based Computer Aided Design (CAD) procedure. The dielectric constant of the FR4 type substrate is assumed to be 4.4 for these calculations. The estimated value of resonant frequency is 2472 MHz. The Return Loss (RL) and Voltage Standing Wave Ratio (VSWR) of the antenna are then measured around the estimated Resonant Frequency of antenna, using a Scalar Network Analyzer setup. The actual resonant frequency of the antenna is found to be 2380 MHz from Return Loss measurements of the antenna. The dielectric constant of substrate is then estimated from the geometry and Resonant Frequency of the antenna. The estimated value of the dielectric constant of substrate comes out to be 4.7545. The probe feed location is also calculated. The radiation pattern of the antenna is measured at the Resonant Frequency 2380 MHz.

In-Line Wood Defect Detection Using Simple Scalar Network Analyzer

Timber is widely used in new structures. The leading causes of structural failure are sited at bolt connections, cavities, and knots. This paper introduces a simple method to detect bolts in wood using a UHF Scalar Network Analyzer (SNA). The electronics placed inside an aluminum box with a slot aperture transmit a microwave signal through the slot, and the near-field signal determines the reflection coefficient (S11). Major changes from baseline are an accurate method to detect cavities and bolts inside the wood. Experiments were conducted on pinewood beams with cross-section dimensions of (70 mm × 70 mm). The scalar network analyzer circuit can detect bolts and cavities within a 30 mm range from the wood surface. The technique can be used for timber beam preparation in an automated sawmill at speed.

Investigation of the Structure and Magnetic and Microwave Absorption Properties of Nanocomposite PVA/Graphite/CoFe1.97Ce0.03O4

Composites PVA/Graphite/CoFe1.97Ce0.03O4 and PVA/CoFe1.97Ce0.03O4 were synthesized and studied. The morphology and structure of the starting materials and composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and infrared spectroscopy (IR). The magnetic parameters were measured using a vibrating magnetometer. The absorptive capacity of the obtained materials was evaluated based on the results of measuring the transmission and reflection coefficients using a scalar network analyzer in the range of 8–12 GHz. The results show that the absorption characteristics of the PVA/Graphite/CoFe1.97Ce0.03O4 composite are significantly higher than those of the PVA/CoFe1.97Ce0.03O4 composites. Effective absorption is observed for the PVA/Graphite/CoFe1.97Ce0.03O4 composite in the frequency range of 8–12 GHz and corresponds to −25.08 dB mm−1, which indicates excellent absorption characteristics of electromagnetic radiation in this frequency range.

Design and Implementation of Microwave Dual-Band Pass Interdigital Filter Using an Analytical Approach

In this paper, benefiting from frequency transformation between the normalized frequency domain of low-pass prototype frequencies and the real frequency domain of the filter, a purely analytical procedure for dual-band filter design is used. The coupling matrix of the filter is analytically extracted, without the need to perform numerical optimization. The procedure also includes finding the equivalent circuit for these types of filters. The frequency transformation formula is verified through an example. The equivalent circuit and the coupling matrix are also analytically deduced through the same example. Using an electromagnetic structure simulator, an interdigital dual-band filter is designed and simulated. The simulation results fulfill the specifications of the given filter example, and the simulation results verify the possibility of achieving the required specifications of the filter frequency response. The designed and simulated filter has been implemented and measured using a Scalar Network Analyzer. The measurement results confirm the simulation results and the efficiency of the synthesis procedure.

Resonant properties of a multilayer strip-slot transition and its application for microwave measurements of dielectric properties of materials

Statement of the problem: One of the actual problems of applying radio materials at high and ultrahigh frequency ranges is the problem of increased requirements for the accuracy of assessing their dielectric properties. Currently, non-resonant and resonant methods are applied to assess the dielectric properties of radio materials at the frequency ranges indicated above. Non-resonant methods are expedient for application in non-destructive testing of large-area sheet materials. Their implementation requires the application of an expensive vector network analyzer. Resonant methods are applied with a limited amount of the test material or in its powder state. In the implementation of resonant methods the main investigated parameter is the displacement of the frequency of the electrical resonance. As a consequence, only the amplitude values of the transmission and reflection coefficients need to be known. This feature makes it possible to carry out microwave measurements for the resonant method applying a scalar network analyzer which has a lower cost compared to a vector network analyzer. That feature is an advantage in some cases. One of the promising directions in the development of the resonant measurement method is its implementation based on applying of a volumetric-modular technology. In particular its implementation that based on application of a multilayer strip-slot transition. The problem with this approach is the lack of researches in terms of the effectiveness of the application of the multilayer strip-slot transition as a device with a tunable frequency of electrical resonance. Aim: The aim of this article is to present a resonant method based on the application of the multilayer strip-slot transition as a basic measuring device. Such a design solution for the implementation of resonant microwave measurements has no analogues. This determined the conduction of current research. The task of which is to theoretically and experimentally substantiate the effectiveness of applying a multilayer strip-slot transition to implement the resonant method for measuring the dielectric properties of materials. Results: The results of theoretical and experimental studies of the resonance properties of the multilayer strip-slot transition are presented. Its application makes it possible to realize an original volume-modular device for the resonant method of measuring the dielectric parameters of materials in the microwave range of wavelengths. The theoretical research is based on the development of an equivalent circuit, which is presented in the form of a cascade connection of four-port networks. The results of mathematical simulation of the multilayer strip-slot transition prove the possibility of implementing on its basis the resonance method for measuring the dielectric parameters of materials in the microwave range of wavelengths. Experimental studies were carried out on a sample of a volume-modular device with the multilayer strip-slot transition. The test material was a powder representing barium hexaferrite BaFe10Ti2O19 partially substituted by titanium. The coincidence of the results of mathematical simulation and experimental studies of the frequency-selective properties of a multilayer strip-slot transition is more than 95%. The error in assessing the permittivity of the used powder material based on the results of theoretical and experimental studies does not exceed 4.5%. Practical significance: The results of the research showed the possibility of applying of the multilayer strip-slot transition as a basic element for the implementation of the resonance method for measuring the dielectric properties of materials. The advantages of the proposed design are compactness and the ability to measure the dielectric properties of powder materials using scalar network analyzers.

Simulation of electromagnetic field distribution in the measuring cell for determining the dielectric permittivity of materials at microwave frequencies

To determine the dielectric permittivity of materials in a wide frequency range with the automation of measurements and the necessary accuracy, measuring cells have been created to ensure the simplicity of the design of the waveguide path. In order to obtain information about the suitability of measuring cells based on irregular SHF waveguides for estimation of dielectric parameters of materials, we simulated the structure of electromagnetic field in the system consisting of two irregular waveguides and waveguide chamber placed between them using a three-dimensional electrodynamic simulation in Ansoft HFSS package environment. The distribution of the electric field was simulated when an empty polyethylene tube, a rod of fluoroplastic and a rod of textolite are placed in the measuring cell. It was demonstrated that high order modes fade out in irregular waveguide and do not affect the precision of obtained results, and significant edge effects were not detected. It allows one to utilize measuring cells based on irregular waveguides together with a scalar or vector network analyzer and using the partial filling of the waveguide method or the modified Nicholson – Ross – Weir method for measurements of dielectric permittivity  of materials. The results of modeling the dependence of the amplitude and phase of the reflection coefficient of the textolite and fluoroplastic on the frequency in Ansoft HFSS environment are given. The simulation results are compared with the results obtained experimentally. The frequency dependencies of  were obtained experimentally for test materials – textolite and fluoroplastic – in the frequency range of 25,95–37,50 GHz. The experimental data are in satisfactory agreement with the results of theoretical calculations and do not go beyond the boundaries specified by the measurement uncertainty.

A Method for Determining Vector Reflection Coefficient Based on Scalar Amplitude

Short-circuited reflection method is usually used to characterize the dielectric property of materials. When using the method, the extraction of the vector reflection coefficient (VRC) of the metal-backed sample is the key to determine the complex permittivity of the sample. Traditionally, the VRC is measured by a vector network analyzer associated with the transmission line or the antenna. In this letter, a method for determining the VRC using a scalar network analyzer is presented, which requires only one perturbation-two-port network composed of a standard sample layer. Based on the amplitude of the VRC, the phase of the VRC can be determined by the proposed rigorous analytical algorithm. The proposed method has been confirmed theoretically and experimentally, and the applicability of the method is analyzed.

Estimation of Cholesterol in the Presence of Urea and Other Constituents in Blood Tissue

The determination of cholesterol in pathological laboratories is more painful and may lead to infections if no proper precautions are taken into consideration. The manuscript presented here describes a non-invasive method to estimate blood cholesterol using Radio Frequency (RF) probe signal in the range of 10MHz – 500MHz. The method uses Scalar Network Analyzer and injects RF signal less than -30dbm, which is quite safe for human tissue and the frequency range falls in non-ionizing radiation wavelengths. Due to the absorption of RF signal by various body tissues including cholesterol, the received signal by the spectrum analyzer bears the signatures of percentage of the cholesterol present in the blood. These signatures are then analyzed using multivariate approach to estimate the Cholesterol. The Signal Processing Unit consists of Partial Least Square Regression (PLSR) tool based on the SIMPLS Algorithm. The results show that there is a good agreement between the predicted percentages of Cholesterol as compared to the actual. Though the study here uses only 5 components, the technique can also be used to include other blood components for the estimation of Cholesterol.

Benchmarking a Commercial (Sub-)THz Focal Plane Array Against a Custom-Built Millimeter-Wave Single-Pixel Camera

For the first time, the characteristics of an evolving commercial camera technology that can operate at millimeter-wave frequencies has been independently investigated. In this work, we benchmark the TeraSense camera against a custom-built single-pixel camera at W-band, for image quality and aperture reflectance. It is found that the Tera-1024 TeraSense camera exhibits limited image resolution and fidelity, with significant levels of systematic spatial noise. In a poor signal-to-noise ratio scenario, the addition of random noise exacerbates these problems. Possible causes of both beam and image distortion have been identified in quasi-optical applications, which gives important insight into the best use of (sub-)THz cameras and interpretation of their images. Inherent standing waves caused by the significant power reflectance of the camera aperture is investigated in detail. A simple W-band one-port quasi-optical scalar network analyzer is developed, to determine the levels of reflectance for both cameras, with its bespoke calibration routine derived from first principles - providing a low-cost solution for many non-destructive testing applications. It is found that the TeraSense camera (with additional RAM) and single-pixel camera (having default RAM) have measured reflectance values of 27% and 3%, respectively, over a corresponding aperture area ratio of approximately 714:1. While our single-pixel camera provides excellent image resolution and fidelity, it inherently suffers from very slow raster-scanning speeds and operational bandwidth limitations. For this reason, the TeraSense camera technology is excellent for performing qualitative measurements in real time, with the caveats outlined in this paper.

Soil Urea Estimation using Embedded Systems

With the advancements in technology constant efforts are being made towards making agriculture sustainable. Green Revolution made extensive use of chemical fertilizers to increase the crop yield, which gave the desired outputs, but high usage of fertilizers led to soil degradability, ground water contamination etc. Precision farming techniques are currently being used to make agriculture sustainable and profitable. Lot of automation is involved in the techniques used for irrigation, harvesting, soil testing etc. Soil testing is an important aspect in agriculture as it decides the crops that can be grown in a particular type of soil and also todecide how much external inputs can be applied to give a good crop yield. Precision farming involves techniques which are real time based. The paper discusses the design and development of a novel soft core embedded platform on Altera FPGA for estimation of urea in soil. RF spectra of five different constituents found in soil are recorded using a scalar network analyzer consisting of Signal Hound tracking generator TG44A and Signal Hound spectrum analyzerUSB-SA124B and a dielectric cell. The samples for recording the RF spectra are prepared in the laboratory by mixing five different constituents namely urea, potash, phoshate, salt and lime taken in the study in distilled water in different proportions. The spectra obtained are then passed through a multivariate system ported on FPGA for the estimation of an unknown concentration of urea in a sample. The multivariate analysis is done using Partial Least Square Regression (PLSR) technique and is implemented using SIMPLS algorithm developed in C. The results obtained show that the estimated values of urea have percentage error of around 5% which is acceptable. Even if the sample concentrations lie outside the confidence interval i.e CI, the estimated results are still satisfactory.

Synthesis and microwave dielectric studies of pure Li2MgSiO4 and B2O3, MgF2, WO3 added Li2MgSiO4 for substrate applications

Synthesis of pure Li2MgSiO4 (LMS) ceramics through solid-state ceramic route and variations in its microwave dielectric properties by addition of different compounds are discussed. Boron trioxide (B2O3), Magnesium Fluoride (MgF2), and Tungsten trioxide (WO3) were used as additives to produce three different ceramics besides pure LMS. Scanning electron microscope and X-ray diffraction spectrometer were used to study the morphology and crystal structure of prepared samples. The densities of the respective samples were measured via Archimedes method. The microwave dielectric properties of the ceramic materials were determined by the cavity perturbation technique using a Scalar Network Analyzer. Pure LMS sintered at 1100 °C/6 h exhibited a relative permittivity (εr) of 5.73 and dielectric loss of 5.897 × 10−4 at 8 GHz. Among the three additives, WO3 improved the relative density of pure LMS from 90.6% to 94.5% and the LMS-WO3 sample sintered at 1100 °C/4 h showed comparatively good dielectric properties, εr = 6.03, tan δ = 6.598 × 10−4 at 8 GHz.

Microwave Absorbing Characteristics of Plasma Sprayed SiC-CNTs/AT13 Absorbing Coating

Electromagnetic parameters of ultra-fine SiC, SiC whisker and nanometer SiC were tested to evaluate the microwave absorbing properties. Optimized nanometer SiC-CNTs/AT13 composite was fabricated by high energy mechanical commixture. Nanometer SiC-CNTs/AT13 absorbing coating was prepared by multi-functional micro-plasma spray system. Morphology and the structure of the powders were characterized by scanning electron microscope. The microwave absorbing characteristic of the coating was evaluated by measuring the reflection loss using an HP8757E scalar quantity network analyzer in the 2-18 GHz band range. The coatings were density, low porosity and uniform morphology. The reflection loss values of -10 dB are obtained in the 2~18GHz range. The minimum reflection loss of the coating is -13.12 dB at 12.64 GHz, and the bandwidth of the reflectivity below -5dB is 9.36GHz. It is indicated that the plasma spraying process is an effective way of preparing microwave absorbing coating.

Moisture and salt monitoring in concrete by evanescent field dielectrometry

Monitoring the water content and detecting the presence of soluble salts in concrete is a key issue for its maintenance. Evanescent field dielectrometry, originally developed for the diagnostics of frescoes and mural paintings, is proposed as a tool for monitoring the decay of cement-based materials. A measuring system, based on a scalar network analyzer and a resonant probe, has been realized and tested on concrete samples taken from historical buildings in France or purposely developed in the laboratory. Measurements on water-saturated and oven-dry samples provide the basis for calibrating the instrument for on site monitoring of concrete historical buildings, sculptures and cement-based artifacts.

A 100–300-GHz Free-Space Scalar Network Analyzer Using Compact Tx and Rx Modules

This paper presents a 100–300-GHz quasi-optical network analyzer using compact transmitter and receiver modules. The transmitter includes a wideband double bow-tie slot antenna and employs a Schottky diode as a frequency harmonic multiplier. The receiver includes a similar antenna, a Schottky diode used as a subharmonic mixer, and an LO/IF diplexer. The 100–300-GHz RF signals are the 5th–11th harmonics generated by the frequency multiplier when an 18–27-GHz LO signal is applied. The measured transmitter conversion gain with $P_{\textrm {in}} = 18$ dBm is from −35 to −59 dB for the 5th–11th harmonic, respectively, and results in a transmitter EIRP from +3 to −20 dBm up to 300 GHz. The measured mixer conversion gain is from −30 to −47 dB at the 5th–11th harmonic, respectively. The system has a dynamic range > 60 dB at 200 GHz in a 100-Hz bandwidth for a transmit and receive system based on 12-mm lenses and spaced 60 cm from each other. Frequency-selective surfaces at 150 and 200 GHz are tested by the proposed design and their measured results agree with simulations. Application areas are low-cost scalar network analyzers for wideband quasi-optical 100 GHz–1 THz measurements.

Magnetic Properties and Magnetization Dynamics of Magnetic Tunnel Junction Bottom Electrode With Different Buffer Layers

We present the research on magnetic tunnel junction bottom electrodes CoFeB prepared on different buffer layers: 5Ta/30CuN/5Ta, 5Ta/15CuN/3Ta/15CuN/5Ta, 5Ta/10CuN/5Ta, 5Ta, 10Ta, and 5Ta/10Ru/5Ta (all thicknesses in nanometers). The buffer crystallographic microstructures were characterized with X-ray diffraction measurements while the roughness was investigated with atomic force microscopy measurements. We show the influence of crystallographic texture and surface roughness on the coercivity and anisotropy fields. Ferromagnetic resonance measurements were performed with a scalar network analyzer to determine the spin-wave dispersion relation of the precession frequency and the damping parameter. The results were confirmed with pulse inductive microwave magnetometry measurements.

Microwave absorption properties of FeSiBNbCu glass-covered amorphous wires

Coaxially dielectric samples consisting of different packing ratios of glass-covered Fe73.5Si13.5B9Nb3Cu1 amorphous wires embedded in a paraffin wax matrix were fabricated, and the influence of short-wire packing ratio (3%–9% in mass fraction) and thickness (1–7 mm) on the microwave absorption properties was systematically investigated in microwave frequency range of 2–18 GHz. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and scalar network analyzer (SNA) were used for characterizing microstructure and evaluating microwave absorption properties. Experimental results show the significant frequency (6–18 GHz) dependence of the complex relative permeability and permittivity. The reflection loss (RL) with different thickness and short-wire packing ratio reveals that the composite sample containing 7% exhibits better microwave absorption behavior with its minimum value of RL reaching −34 dB in thickness of 3 mm at 14 GHz. Therefore, it is significantly useful to develop microwire-dielectric materials with much wider absorption band for microwave absorption applications.

Research on the memory order of the power‐line communication channel

SummaryAs a memory channel, power‐line communication (PLC) channel can be modeled by the finite states Morkov model. The memory order in an finite states Morkov model is a key parameter, which is not solved in PLC systems yet. In the paper, the mutual information is used as a measure of the dependence between the different symbols, treated as the received scalar network analyzer, or amplitude of the current channel symbol or that of previous symbols. The joint distribution probabilities of the envelopes in PLC systems are computed based on the multi‐path channel model, which is commonly used in PLC. With the first‐order Markovian assumption, we confirm that given the information of the symbol immediately preceding the current one, any other previous symbol is independent of the current one in PLC systems. The field test is also performed to model the received OFDM signals with the help of autoregressive model. The results show that the first‐order autoregressive model is enough to model the fading channel in PLC systems, which means the amount of uncertainty remaining in the current symbol should be negligible, given the information corresponding to the immediately preceding one. Copyright © 2014 John Wiley & Sons, Ltd.

0.22 THz wideband sheet electron beam traveling wave tube amplifier: Cold test measurements and beam wave interaction analysis

In this paper, we describe micro-fabrication, RF measurements, and particle-in-cell (PIC) simulation modeling analysis of the 0.22 THz double-vane half period staggered traveling wave tube amplifier (TWTA) circuit. The TWTA slow wave structure comprised of two sections separated by two sever ports loaded by loss material, with integrated broadband input/output couplers. The micro-metallic structures were fabricated using nano-CNC milling and diffusion bonded in a three layer process. The 3D optical microscopy and SEM analysis showed that the fabrication error was within 2–3 μm and surface roughness was measured within 30–50 nm. The RF measurements were conducted with an Agilent PNA-X network analyzer employing WR5.1 T/R modules with a frequency range of 178-228 GHz. The in-band insertion loss (S21) for both the short section and long section (separated by a sever) was measured as ∼−5 dB while the return loss was generally around ∼−15 dB or better. The measurements matched well with the S-matrix simulation analysis that predicted a 3 dB bandwidth of ∼45 GHz with an operating frequency at 220 GHz. However, the measured S21 was ∼3 dB less than the design values, and is attributed to surface roughness and alignment issues. The confirmation measurements were conducted over the full frequency band up to 270 GHz employing a backward wave oscillator (BWO) scalar network analyzer setup employing a BWO in the frequency range 190 GHz–270 GHz. PIC simulations were conducted for the realistic TWT output power performance analysis with incorporation of corner radius of 127 μm, which is inevitably induced by nano-machining. Furthermore, the S21 value in both sections of the TWT structure was reduced to correspond to the measurements by using a degraded conductivity of 10% International Annealed Copper Standard. At 220 GHz, for an elliptic sheet electron beam of 20 kV and 0.25 A, the average output power of the tube was predicted to be reduced from 90 W (for ideal conductivity/design S-parameters) to 70 W (for the measured S-parameters/inferred conductivity) for an average input power of 50 mW. The gain of the tube remains reasonable: ∼31.4 dB with an electronic efficiency of ∼1.4%. The same analysis was also conducted for several frequencies between 190 GHz–260 GHz. This detailed realistic PIC analysis demonstrated that this nano-machined TWT circuit has slightly reduced S-parameters and output power from design, but within an acceptable range and still have promising output power, gain, and band width as required. Thus, we expect to meet the specifications of 1000 W-GHz for the darpa program goals.

A 15–50-GHz Quasi-Optical Scalar Network Analyzer Scalable to Terahertz Frequencies

A 15-50-GHz two-port quasi-optical scalar network analyzer consisting of a transmitter and receiver built in a planar technology is presented. The network analyzer is based on a Schottky-diode multiplier and mixer integrated inside a planar antenna and fed differentially by a coplanar waveguide transmission line. The antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The local oscillator signal is swept from 3 to 5 GHz and high-order harmonic mixing in both the up- and down-conversion mode is used to realize the RF bandwidth. The network analyzer has a dynamic range of >;50 dB in a 1-kHz bandwidth, and was successfully used to measure frequency-selective surfaces with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =20, 30, and 40 GHz and a second-order bandpass response. Furthermore, the system was built with circuits and components for easy scaling to millimeter-wave frequencies, which is the primary motivation for this work.

Use of conducting inductive meshes with periodic rectangle units as an infrared/microwavedual-mode detecting beamsplitter

By optimizing the periods along thex andy axes of conducting inductive meshes with periodic rectangle units to minimizethe differences in microwave reflectivity between the perpendicular and parallelpolarizations, conducting inductive meshes with periodic rectangle units can be madeuseful as an infrared/microwave beamsplitter for the construction of a dual-modedetecting system. A conducting inductive rectangle-unit mesh beamsplitter isdesigned and fabricated using a laser directing writing technique. The microwavereflectivity and infrared transmissivity coefficients of the mesh beamsplitter sample aremeasured using a scalar network analyzer and a Fourier infrared spectrometer.Measurement and simulation results indicate that the microwave reflectivity and infraredtransmissivity coefficients of infrared/microwave mesh beamsplitter are higher than − 1.5 dBand − 0.7 dB, respectively. It can therefore be concluded that conducting inductive meshes withperiodic rectangle units can be used as an infrared/microwave beamsplitter in a dual-modedetecting system.