Automatic Network Analyzer Research Articles

Open-Ended Coaxial Probe for Dielectric Thickness Measurements

Open-ended coaxial probes have been used extensively in determining the dielectric properties of materials in the radio and microwave frequencies. The probes are used in conjunction with an automatic network analyzer to measure electrical and material properties. The technique is based on the principle that measured reflection coefficient of a loaded coaxial probe is related to the dielectric properties of the material in contact with the probe. The dielectric properties, in turn, provide information on the electrical energy storage, dissipation, hydration and quality of the test material.

Free-Space Transmission Dielectric Properties Measurement Based on Six-Port Technology

A six-port technology operating in transmission mode was developed for accurate determination of dielectric properties of low-loss materials from space measurements. The transmission coefficient was obtained by using the ratio of incident waves at ports 1 and 2 of the six-port network, while the power readings were performed at ports 3-6 simultaneously. The incident wave at port 1 originated from a forward propagating electromagnetic wave passing through the material sample. The incident wave at port 2 was the reference signal related to the incident wave at port 1 before or after propagating through the material. The calibration function is developed. The proposed six-port measurement technique was demonstrated at 5.8 GHz for purpose of verification. The material sample was placed between transmitting and receiving antennas. The microwave signal from the oscillator was fed to the transmitting antenna. The receiving antenna collected the signal and sent it to port 1. Two configurations were set up at port 2, either connected to the microwave signal from the oscillator or terminated with an electrical load. Magnitude and phase measurement results for various thicknesses of dielectric slabs compared well with those obtained with a commercial automatic vector network analyzer (ANA). Similarly, dielectric properties measurements on polypropylene, acrylic, and acetal spheres also agreed well with those obtained by the ANA.

Monitoring Lead in Soil Water System Using Complex Permittivity

The complex permittivity was investigated to detect lead contamination in soil. The system used consists of an Automatic Network Analyzer (ANA), a sample holder, coaxial cables and a personal computer for data processing. Five samples of Halton Till soil were prepared and mixed with five different concentrations of hybrid blends of lead salts (PbSO4, PbCl2 and Pb(NO3)2). The objective was to investigate the capability of complex permittivity to detect lead, when introduced to the soil in hybrid blend salts. Chemical analysis was conducted on the pore water of the six soil samples to investigate lead transport and the potential risk of lead in groundwater sources. The results show that the complex permittivity is sensitive to the change in lead concentration in soil as the real part decreases and the imaginary part increases with the increase of lead concentration. The real part decreased from 23 to 17 when the concentration of the lead increased from 0 to 1800 ppm. The imaginary part increased from 16 to 24 as the lead concentration in soil increased from 0 to 1800 ppm. The chemical analysis of the pore water showed that the electrolytes increased as lead concentrations increased in soil. The results displayed that the complex permittivity could be used as a nondestructive tool to monitor lead contamination in soil.

Portable Six-Port Reflectometer for Determining Moisture Content of Biomass Material

A portable six-port reflectometer for determining moisture content of biomass material is proposed for the first time in this paper. The proposed system consists of a 5.13-GHz reflectometer used with an open-ended half-mode substrate-integrated waveguide sensor. The complex permittivity of biomass (sawdust) was measured, and a dielectric-properties-based algorithm for moisture determination was developed. The reflectometer performance was verified by comparing the measured complex permittivity to results obtained with a commercial automatic network analyzer. Finally, the predicted moisture content was compared with the standard oven drying method.

Complex Permittivity to Detect Lead in Soil with Various Salt Forms and Combinations

The response of soil-water systems to an external electric field can be described as polarization and conduction. Polarization represents the electric charges stored in a material, whereas conduction is the ability of a material to conduct free charges. The combined effects of polarization and conduction can be expressed in terms of complex permittivity. Since the complex permittivity of a soil-water system is a function of soil properties, this research was undertaken to detect soil contamination using the complex permittivity measurements. The system used in this investigation to measure the complex permittivity of a lead contaminated soil consisted of an Automatic Network Analyzer (ANA), a set of coaxial cables, a personal computer (PC) for data processing and a coaxial sample holder. Two sample holders were first used: long holder and short holder. It was found that the short holder can give reliable and close measurement to the long holder. The short holder was later adopted. Soil samples were prepared in the lab and mixed with lead nitrate solutions and with hybrid blend of lead nitrate and lead chloride solutions. The relationship between the complex permittivity and lead concentration was investigated. A chemical analysis of the pore fluids for all lead contaminated soil samples was conducted to trace the presence of lead in soil. It was found that the complex permittivity is affected by lead concentration in soil, as the real part decreased and the imaginary part increased with an increase in lead concentration. Lead was not detected in the soil pore water for the soil tested, which suggested that lead was immobilized by precipitation and the adsorption mechanism.

Measured Dielectric Permittivity of Contaminated Sandy Soil at Microwave Frequency

Measurement of dielectric permittivity of soil has been studied by many researchers. However, few studies have been conducted on contaminated soil. The motivation of the present study is to investigate the behavior of sandy soil contaminated by lubricant oil at microwave frequency. Two different artificially prepared soil samples are measured in the laboratory. The measurement of the complex permittivity of soil samples is reported in the frequency range 500 MHz – 4 GHz using open-ended coaxial probe technique. Measurements are carried out using a dielectric assessment system associated with an automatic network analyzer and a dielectric probe connected to a computer. The experimental set up is described and the system response is obtained. It is observed that the complex permittivity of the soil is associated with the contamination. The measurement results show that the change in the dielectric loss of dry sand before and after lubricant oil contamination is quite significant. Measuring these dielectric contrasts provide a basis for using ground-penetrating radar or other high-frequency electromagnetic sensors in the detection of soil contamination.

Microwave Dielectric Properties of Standard Liquids: Numerical and Experimental Data

Dielectric spectroscopy has been established as a standard technique to study the interaction of electromagnetic waves with biological materials such as tissues and cells. In this work, we developed a MATLAB program to simulate the dielectric dispersion characteristics of three standard liquids using the Debye and Cole-Cole models. The liquids were water, methanol and ethanol, simulated in the microwave frequencies. In addition to plotting the real and imaginary parts of complex permittivity, as a function of frequency, we also developed a code to linearize the data by computing different mathematical combinations of the dielectric properties. We validated the models by using a Dielectric probe in conjunction with Agilent E5071C Automatic Network Analyzer (ANA), to measure the dielectric properties of these liquids between 100 MHz and 8.5 GHz frequency range, at a room temperature of about 20 degrees Celsius. We computed properties such as the relaxation time and the relaxation frequency, which were in good agreement with literature data. Results show a good agreement between the numerical and experimental data. This work will enhance the determination of the electrical properties of substances in biological and material sciences.

Absorption of Microwaves in Low Intensity Eucalyptus Litter Fire

A fuel bed was constructed where various vegetation species could be used as combustion fuel. The fuel bed was equipped with a thermocouple to measure fire temperature and a two-port automatic network analyser to measure microwave scattering parameters in flame medium. The parameters are then used to determine microwave propagation characteristics in fire. The measurements have implications on radio wave communication during wildfire suppression and in remote sensing. The attenuation data also provide an estimation of vegetation fire ionisation and conductivity. Eucalyptus litter fire with a maximum flame temperature of 976 K was set on the fuel bed and X-band microwaves (7.00 - 9.50 GHz) were caused to propagate through the flame. Attenuation of 0.35 - 0.90 dB was measured for microwaves in the frequency range. For the low intensity fire, conductivity was measured to range from 0.00021 - 0.00055 mho/m and electron density was to be the range of 1.83 - 2.24 × 1015 m-3.

Monitoring Diabetic Wound Healing with a Dielectric Probe

Diabetes is a metabolic disease in which an individual cannot produce enough insulin or utilize the insulin produced by the body. This results in high or low blood glucose levels, which can be fatal if not monitored and controlled. Complications of diabetes include nerve end damage, reduced peripheral blood flow, which can also lead to slow wound healing, ulcers and amputations. This work proposes the use of a dielectric probe to track the wound healing process of a diabetic subject. It is based on the principle that the microwave dielectric properties of tissues such as skin or muscle, provide information on their structure, composition and physiological state. We used an automatic network analyzer, together with a dielectric probe, to measure dielectric constant and dielectric loss factor of the skin of our subject over a one-month period. Data was collected between 100 MHz and 8.5 GHz frequency range. Results showed a proportional increase in dielectric constant and loss factor with increase in the wound-induced edema. This work enhances the development of an electromagnetic wound-monitoring technique and provides data for tissue engineering applications.

Analysis and Design of a Differential Sampled-Line Six-Port Reflectometer

The analysis and design of a differential six-port reflectometer (SPR) based on a sampled-line structure is presented in this paper. The practical differential SPR is realized in Coplanar Strip (CPS) transmission line form, using two baluns for interfacing with the RF source and device under test (DUT) and four baluns connected to the RF logarithmic detectors. The performance of the proposed differential SPR structure is evaluated with a common-mode rejection ratio analysis and impedance measurement. A prototype differential SPR was designed and fabricated at 1 GHz in order to verify the analysis. Measurement results for various load impedances are compared with the measured results obtained from a commercial automatic vector network analyzer. It is shown that the differential structure gives a significant advantage in rejecting common-mode interference signals.

Microwave Sensor for Measuring the Growth of Biomaterials

The propagation of electromagnetic waves in a transmission line is affected by the dielectric permittivity and thickness of the material surrounding the line. We present a technique that can determine the growth of biomaterials from measurements of wave propagation characteristics. It utilizes a coplanar transmission line as sensor and an Agilent Automatic Network Analyzer for measurements in the time domain. The test material is placed on one side of the sensor. Numerical analysis indicates that the phase velocity, effective dielectric constant, and characteristic impedance show dependence on the thickness of the test dielectric. Experimental verification was obtained using water as the test dielectric. This technique can be used for continuous monitoring of the growth or thickness of biomaterials.

Frequency and Time Domain Characterization of a Novel Hexagonal-shaped Microstrip Antenna for Ultra Wideband Applications

This paper presents frequency- and time-domain characterization of a new hexagonal-shaped monopole antenna with small slots for ultra-wideband (UWB) applications. The antenna was simulated using commercial software tools (CST) microwave studio and Agilent ADS. Neltec make a soft substrate having a dielectric constant of 2.2 and a board thickness of 0.254 mm (10 mil) was used to fabricate the proposed antenna. Frequency-domain characterization using an automatic network analyzer showed return loss less than -10 dB over the entire UWB frequency band. To study the effect of various parameters on the antenna performance, the detailed parametric study was carried out. The radiation patterns and group delay characteristics were measured in an anechoic chamber. Using an Agilent DSO9000A oscilloscope, time-domain characterization of the antenna was carried out. The simulated and measured results in the time domain showed good agreement. It was observed that the proposed antenna shows reasonably good frequency characteristics and time-domain pulse distortion is small indicating usefulness of the antenna for UWB communication applications.

A millimeter wave large-signal model of GaAs planar Schottky varactor diodes

A millimeter wave large-signal model of GaAs planar Schottky varactor diodes based on a physical analysis is presented. The model consists of nonlinear resistances and capacitances of the junction region and external parasitic parameters. By analyzing the characteristics of the diode under reverse and forward bias, an extraction procedure of all of the parameters is addressed. To validate the newly proposed model, the PSVDs were fabricated based on a planar process and were measured using an automatic network analyzer. Measurement shows that the model exactly represents the behavior of GaAs PSVDs under a wide bias condition from −10 to 0.6 V and for frequencies up to 40 GHz.

Determination of Contamination of Beverages using Dielectric Spectroscopy

Knowledge of the dielectric properties of beverages and juices provides information on their purity, quality and composition. Dielectric properties such as relative permittivity, dielectric loss factor, and electrical conductivity were measured as a function of frequency using an open-ended dielectric probe in conjunction with an automatic network analyzer (ANA) between 0.1 and 3 GHz frequency range. Dielectric properties of pure drinks such as Gatorade, water, wine, beer, and drinks contaminated with various volumes of ethylene glycol were measured at a temperature of 20.0 degrees Celsius. Results showed a decrease in dielectric constant with frequency for all samples. There was- a linear increase in dielectric constant with per cent volume contaminant. Results also showed an increase in the dielectric relaxation time of the contaminated drinks with the level of contamination, which is attributed to the increased charge content in the contaminated drinks. The minimum detectable per cent contamination was about 1 %. This technique holds a strong potential for use in routine quality control measurements in pharmaceutical industries and wineries.

Wideband planar Goubau line integrated circuit components at millimetre waves

This study provides the design, fabrication and test results of passive planar Goubau line (PGL) components compatible with active micro-strip circuits, in millimeter(mm)-wave frequency range (40–60 GHz). Such wideband passive components are of interest in designing wideband digital wireless communication equipment. Basic passive components of this study include: two PGLs with conductor strip widths of 50 and 260 µm, respectively, transitions from chosen PGLs to 50 Ω micro-strip circuit, PGL loads and PGL power divider/combiners. Active components such as planar micro-strip circuits can be placed in tandem with passive PGLs using above transitions to design wide band circuits from microwaves to mm waves. PGL is formed by a planar conductor deposited on a standard 0.254 mm (10 mil) planar alumina substrate (ceramic) as opposed to the standard Goubau line made with a circular conductor and a circular dielectric. Passive PGL components are designed, simulated, fabricated and measured with an automatic network analyser (ANA) and test fixture. Simulation and test data support PGL component designs. PGL components operate well over a wide frequency range (from 40 to about 60 GHz). Similar results are expected with PGL at other mm-wave frequencies (below 40 GHz and above 60 GHz) and at terahertz frequencies (above 100 GHz).

Dielectric properties of acetic acid and vinegar in the microwave frequencies range 1–20 GHz

Complex dielectric spectra of acetic acid solutions were measured at frequencies in the range of 1–20 GHz using an automatic network analyser at room temperature. The spectra of different commercial vinegars were also measured. All spectra follow a Debye relation for both the real and imaginary parts of permittivity. The Debye relation, with an additional term for ionic conduction losses, was fitted to the data, and six parameters were extracted. Quantitative relations between the parameters that define Debye relations and the acid contents in solution were obtained.

A novel approach of measuring the dielectric properties of PET preforms for stretch blow moulding

AbstractPolyethylene terephthalate (PET) is the most common plastic material used in injection stretch blow molding (ISBM) process for the manufacturing of bottles. The injection‐molded PET preform has to be preheated uniformly to a pliable state before the blowing stage of the process. Microwave technology offers a potentially more economical means for preheating the preform in place of the conventional infrared oven heating. For such applications, determination of dielectric properties of PET preform of a given geometry is essential. This article describes a novel approach of measuring the dielectric properties of PET preforms at microwave frequencies instead of the common experimental procedures used for such measurements. The dielectric properties are determined by using both CST Microwave Studio electromagnetic simulation software and the automatic network analyzer together. No complex mathematical solutions are required. Validation of this new approach has been made by comparing the measured dielectric properties of some polymers with those available in the published literature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

The Effects of Salinity on the Accuracy and Uncertainty of Water Content Measurement

We used an automatic network analyzer (ANA) operated in both time and frequency domain modes to investigate the measurement accuracy of metallic time domain reflectometry (TDR) probes operated in sands saturated with NaCl solutions of varying electrical conductivity (EC). We chose to use time domain transmission (TDT) measurements for this investigation to separate the effect of the bulk soil‐probe interaction from the effect of the large reflection typically found at the air–soil boundary for a TDR configuration. Pulse travel times and their variability increase with increasing pore‐water EC. The source of travel time variability arises from the extreme variability in pulse shape, thereby introducing a high degree of uncertainty to curve fitting routines used to determine travel times. Pulse shape distortion is due primarily to attenuation of high frequency components through conductive loss rather than by dispersion. There is generally good correspondence between pulse rise time and the average water content measurement error over a 0‐ to 40‐dS m−1 EC range. For rise times <6 ns, measurement errors are <0.1 m3 m−3 Given that rise times can be determined easily, we recommend that they be reported routinely as indicators of data quality. Because the variability of travel time measurements at a given EC is on the same order as the average difference between the travel time measured at that EC and that measured at zero salinity, pulse rise times cannot be used to correct for individual travel time measurements at high salinity. Similarly, knowledge of the EC of the medium may allow for identification of erroneous water content measurements, but does not allow for error correction.

Analogies between the measurement of acoustic impedance via the reaction on the source method and the automatic microwave vector network analyzer technique

One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ‘‘looking into’’ the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ‘‘removed’’ completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer’s characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.

Transients on multiconductor transmission lines above dissipative earth~numerical simulation and measurement

A finite-difference time-domain (FDTD) analysis is presented to simulate, up to the high-frequency regime, transients on multiconductor transmission lines above dissipative earth. Excitation is in the high-frequency regime if the pulse has significant spectral content up to /spl omega//spl ap//spl omega//sub c/, with /spl omega//sub c/ the frequency where the conduction and displacement current densities have equal magnitude. Thus, /spl omega//sub c/=/spl sigma//sub g///spl epsi//sub 0//spl epsi//sub rg/ with /spl sigma//sub g/ and /spl epsi//sub rg/ the ground conductance and relative permittivity. The FDTD algorithm extends the formulation of Agrawal et al. (1980), by incorporating the theory of D'Amore and Sarto for the interaction of wide-band transients with the earth. Careful experimental testing of the new algorithm is presented. The measurement configuration consists of two parallel wires; first suspended above an aluminum sheet to test the code in the low-frequency regime; then above a block of absorbing material for experiments in the high-frequency regime. The end of one of the conductors is driven with a 2-ns synthesized impulse by a stepped-frequency, automatic network analyzer. Reflected and cross-talk signals are presented in the time domain. These show good agreement with the numerically predicted common mode, differential mode and mode-converted pulses.