Scalar Network Analyzer Research Articles

Silica-coated iron nanoparticles: Shape-controlled synthesis, magnetism and microwave absorption properties

Abstract Body-centered cubic (bcc) phase iron nanocrystals with granular, rod-like and flaky shapes were prepared through a simple surfactant-controlled chemical reduction route. In view of extra stability and enhanced manipulative ability, thus-prepared iron nanoparticles were morphology-retained modified with a thin silica shell through a Stober process. A serial of techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), thermogravimetry (TG), vibrating sample magnetometer (VSM) and scalar network analyzer (SNA) were used to characterize the iron particles before and after silica coating. Results showed that the surface silica coating could effectively improve the oxidation resistance and microwave absorption performance of iron particles, while slightly influenced their magnetic properties. Furthermore, the flaky Fe@SiO2 nanocapsules particles exhibited better microwave absorption performance than that of the granular and rod-like counterparts, which could be ascribed to the shape effect.

A Fast and Accurate Amplitude-Only Transmission-Reflection Method for Complex Permittivity Determination of Lossy Materials

Complex scattering parameter measurements using expensive vector network analyzers make microwave techniques inconvenient for industrial-based applications. In industry, accurate and fast evaluation of materials' properties using a relatively inexpensive measurement setup is a key issue. In this paper, we derive an objective function for fast and accurate complex permittivity (epsiv) determination of lossy materials using amplitude-only reflection and transmission scattering parameter measurements. The measurements can be carried out by relatively inexpensive microwave instruments such as a scalar network analyzer. The domain for computations of the epsiv is significantly reduced to facilitate rapid epsiv determination. The objective function is verified by measurements of a commercially available antifreeze solution and binary mixture of ethyl alcohol and water solution.

Characterization of carbon-attenuator coatings for helical traveling wave tube applications

Attenuator coatings of carbon were deposited on alumina support rods by pyrolytic deposition, aquadag coating and arc discharge to absorb the reflections and to improve the stability of a helical traveling wave tube. An experimental set up involving a narrow-height wave-guide with a hole was used to measure the attenuation of the coated rods at 6.0 GHz frequency by carrying out reflection and transmission measurements using a scalar network analyzer. The same structure was also simulated by using a high frequency structure simulator (HFSS). Results indicate that the aquadag-coated films provide a maximum loss or absorbance and are suitable as the attenuator coating. The simulated results by HFSS agree well with the experimental observations.

Phase-reconstruction in photonic crystals from S-parameter magnitude in microstrip technology

A method based on Hilbert-transforms is used to reconstruct phase, group-delay and impulse response from magnitude-only information regarding the S 11 and S 21 parameters of photonic crystals (PC) constructed by periodically etching the ground plane of a microstrip line. Measurements show that for many practical cases this allows us to fully characterize the devices with a simple scalar network analyser instead of more sophisticated and expensive instrumentation, such as a vector network analyzer (VNA).

Frequency domain reflectometry of plasma chambers

Abstract Frequency domain reflectometry (FDR) is used to compare the electrical characteristics of five industrial plasma chambers, without the plasma present, used in the manufacture of semiconductors devices at Intel-Ireland. A scalar network analyzer (SNA), consisting of a tracking generator/spectrum analyzer and a radio frequency bridge was used to sweep the chambers from 1 MHz to 1 GHz. The non-invasive nature of the measurement interrogates the matching network, the wafer platen electrode fringing capacitance to ground, and radio frequency resistive loss. The resulting frequency response gives a unique fingerprint of the chamber, and is completely transferable between chambers for post-maintenance qualification and chamber comparison. The results from three electron cyclotron resonance (ECR) chambers are compared with the two single-frequency capacitively coupled plasma chambers and one dual–frequency inductively coupled plasma chamber. A comparative chamber survey of the three ECR chambers reveals a strong wafer electrode reflection in the 500 MHz frequency region. Whereas, for slab-like plasma chamber designs (such as the LRC Rainbow 4400 chamber) the wafer electrode response is at 14–15 MHz. It is found that the chamber design and individual components have a unique frequency response. A linear analogue circuit simulator was used to verify and characterize the measurements.

The Interaction of the Collisional Plasma with Microwave

The generation of plasma which can absorb microwaves is currently a research topic of interest. This kind of plasma is often produced by the discharge or electron-beam impact of noble gases. In this paper an alternatice approach, combustion plasma, is studied. The plasma is produced by combusting solid grains prepared specially. Six groups of powders were made and used to generate the plasma. The transmissivity of the wave in plasma was measured by employing a microwave scalar network analyser system. In addition, the electron density and the collision frequency of the plasma were examined by microwave double-frequency diagnosis. The measurement results showed that the plasma could absorb microwaves remarkably with an average transmission attenuation being more than 18 dB in a frequency range of 2 GHz to 15 GHz. The diagnosis indicated that the electron density of the plasma varied from 1017 m−3 to 1019 m−3 and the collision frequency was about 5×1010 s−1.

A multiresonance method for measuring the reflection coefficient in a waveguide

A new method for measuring the complex reflection coefficient in rectangular waveguides using a scalar network analyzer is proposed. This method is based on measurements of the resonance characteristics of a quasi-resonator, i.e., a portion of the waveguide between a reflecting object on one side and an object with a known scattering matrix on the other side. One advantage of the multiresonance technique is that simultaneous analysis is performed for the entire set of resonance frequencies, which substantially increases the accuracy in finding the reflection coefficient. The errors in measuring the magnitude and phase of the reflection coefficient in actual experiments were close to 0.015 and 1.5°, respectively.

Frequency-domain measurement of indoor UWB channels

In this paper, we have implemented and analyzed BSFs with ring resonators. The attenuation poles were obtained using the ABCD matrix. We have utilized different perturbation elements to control the attenuation poles in order to obtain good performance. The numerical calculation of the lumped elements agrees with the simulation and measurement. In addition, all the simulated and measured results of the filters have been presented and compared with the theoretical results. ABSTRACT: A frequency-domain approach for propagation measure- ments and characterization of indoor ultra-wideband (UWB) channels is presented. The approach is based on measurement of the magnitude using a scalar network analyzer and retrieving the phase from the mag- nitude data using a Hilbert transform relationship. Extensive propaga- tion data are collected in a frequency range of 1 to 12 GHz in two buildings on the Virginia Tech campus. Using the measured data, chan- nel-characterization results are obtained and compared to those based on time-domain measurements. The statistical results for small-scale fading, the path-loss exponent, and signal quality are presented. The frequency-domain results are generally in good agreement with the time-domain results, and also reaffirm the immunity of UWB propaga- tion to small-scale fading. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 118 -123, 2005; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/mop.20563

A frequency domain measurement diagnostic technique for plasma-tools

The design of a 10–500 MHz bridge is described and also its use with a tracking generatorand spectrum analyser to form a scalar network analyser for the investigation of theinternal electro-mechanical components of a parallel-plate and inductively-coupledplasma-tool. The non-invasive frequency scalar data obtained (with the plasma off)provides a frequency related registration of the internal components of the plasma-tool forgiven match network settings. Frequency data are presented for a parallel-plate chamberand a STS plc inductively-coupled plasma-tool as viewed via the lower electrode platen.Components identified relating to these chambers are the matching network, electrodeposition, wafer loading arm, wafer lift pin position and silicon wafer dislodgement. Thedata are used for comparing similar build configurations and fault conditions.

Selektiver S-Band-Messempfänger für einen Millimeterwellen-Netzwerkanalysator

The following report shows the design and development of a selective S-band measurement receiver. Its function is the detection of the received power in a 100 GHz to 175 GHz scalar networkanalyser. The dynamic range is from -90 dBm to +7 dBm. A superheterodyn receiver architecture is realized. The received signal is converted down to an intermediate frequency of 115 MHz by a passive mixer. The local oscillator uses a PLL stabilized VCO to pump the mixer. In the intermediate frequency the level is matched and a bandpass filter limits the bandwidth. The detector is a logarithmic amplifier which is available as an integrated circuit. This project was possible through a cooperation between the Institut fur Hochleistungsimpuls- und Mikrowellentechnik at the Forschungszentrum Karlsruhe and the Institut fur Hochstfrequenztechnik und Elektronik at the Universitat Karlsruhe (TH).

Group delay measurement of WDM components using photonic microwave technique

AbstractIn this paper we propose a new method for the measurement of the relative group delay of WDM components, based on photonic microwave technique using a low frequency (below 1.3 GHz) scalar network analyzer. Experimental results demonstrate that this technique has the advantages of low cost, simplicity, and high accuracy (less than ±1 ps). © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 346–348, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10602

Novel technique to detect rancidity of oils using microwave microstrip ring resonator

AbstractThe present article presents a novel technique to study the rancidity of oils at microwave frequencies through measurements of microwave dielectric properties of liquids. CaCO3 (chalk) was used as a noninteracting medium (matrix) to hold the liquids within and is used to perturb the microwave microstrip ring resonator (MMRR). The rancidified oils exhibit high dielectric constants, giving higher changes in resonating frequencies. The method is found to be repeatable. Coconut oil (Cocos nucifera), sunflower oil (Helianthus annuus), rancidified coconut oil and rancidified sunflower oil were studied using this technique. The resonant frequency was measured using a scalar network analyzer (SNA, HP 8757C). The method shows noticeable differences in resonating frequency (few tens of MHz) between fresh oil and rancidified oil. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 377–379, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10327

A microwave microstrip ring resonator as a moisture sensor for biomaterials: application to wheat grains

A miniaturized, non-destructive sensor employing a microwave microstrip ring resonator (MRR, GHz, mean diameter 3.69 mm) was developed for estimating the moisture content of a single wheat ( Triticum aestivum L) grain. A single wheat grain with a known amount of moisture was placed on the MRR at two different orientations ( and ) with respect to the feedline. The resonance frequency , bandwidth (B) and quality factor of the MRR were calibrated against the moisture content. The measurements were made with a scalar network analyser. The sensor was studied in the normal useful moisture range of 11-32% (on a wet-weight basis), the actual moisture values being obtained by an oven-drying method. The orientation was more sensitive to moisture than was the orientation. The total changes in for a 21% change in moisture content for and 90 orientations were 235 and 150 MHz, respectively. The errors in moisture estimation with for and were % and %, respectively. The corresponding values with B and for orientation were % and %, respectively. The proposed sensor is more sensitive than a reported waveguide resonator and is easy to operate, for the microstrip offers an open structure, thereby facilitating easy loading and unloading of the samples.

Characterization of high-Q resonators for microwave filter applications

A one-port reflection technique is developed to measure the unloaded Q and external Q of a microwave resonator. The unique procedure of measuring unloaded Q is outlined in three easy steps. A sample chart is provided to further simplify the process. This method is so simple that even a scalar network analyzer is adequate for the measurement. In addition, a time-delay response around the resonator resonant frequency is also derived and presented. This theoretical result, combined with the advanced capability of modern vector network analyzers, has been proven to be very useful for characterization and tuning of the external Q of a resonator. All the results derived are verified by practical measurement. Finally, this technique is applied to the realization and tuning of a six-pole dielectric loaded cavity filter.

A novel vector network analyzer

A calibration procedure for a perturbation two-port vector network analyzer is presented. It consists of a variable perturbation two-port placed between a device-under-test and a scalar network analyzer. A measured vector reflection coefficient is determined on the basis of amplitude-only measurements. A full correction of systematic errors is possible. The new principle was experimentally confirmed in the frequency band up to 14 GHz. The results enable prediction of an add-on for scalar analyzers, enabling vector measurements.

Hilbert-transform-derived relative group delay

Many common types of microwave circuits, particularly filters, are required to meet a group delay ripple specification. This is normally measured using a vector network analyzer (VNA) or some specialized test configuration. A new method of assessing the group delay ripple of a broad class of microwave circuits is presented, which uses a scalar network analyzer and a form of the Hilbert transform. Experimental results illustrating the usefulness of the technique are shown for a series of examples and the principal sources of error are analyzed.

Q-factor measurement with a scalar network analyser

An accurate determination of the unloaded Q-factor of RF and microwave resonators is required when the electrical properties of materials are being measured or when the resonator is to be characterised for an application in a filter or an oscillator. A procedure is described of weighted least-square curve fitting to the measured magnitude of the reflection coefficient. The accuracy of the results is significantly improved by incorporating coupling losses in the equivalent circuit model.

PCs for AP and other EM reflections

A FORTRAN subroutine is presented, which accurately determines the effective width of a waveguide and its length, by measuring the resonance frequencies of the cavity made of the same waveguide. This measurement method only necessitates a scalar network analyzer and standard waveguide components. >

Dielectric constants of rubber and oil palm leaf samples at X-band

The paper reports on the measured dielectric constants of leaves of two tropical crops, namely rubber and oil palm, as a function of moisture content at X-band. Using a microcomputer-based automated system consisting of a Wiltron scalar network analyzer and a slotted waveguide, the measurements are done based on the waveguide thin sheet technique. Theoretical values from the dual-dispersion model by Ulaby and El-Rayes [1987] and from the simple dielectric theory of Fung and Fung [1977] are compared with the experimental data. The model from Ulaby and El-Rayes is found to be able to give good estimates of the dielectric constants for the two types of leaf samples at X-band.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Rapid High Temperature Measurement of Microwave Dielectric Properties

ABSTRACTPractical high temperature (above 500°C) dielectric measurement techniques are reviewed stating both advantages and limitations of known methods. Details of a new and practical dual frequency microwave high temperature dielectrometer are discussed. This dielectrometer technique is capable of measurements beyond 2000°C. Both heating of the small samples and the measurement of their complex dielectric constant is done simultaneously using both a medium power (60W) microwave source and a low power scalar network analyzer. Good accuracy is obtained and the measurement is capable of being totally automated. Presently, a measurement and heating cycle time of about 20 s is needed to completely characterize the sample's microwave dielectric response from 300°C to 1600°C. A second high temperature dielectrometer technique is discussed which requires only one microwave source of medium power level (60W). This method requires only the reflected power to be monitored during the microwave heating of the sample to obtain the complex permittivity versus temperature curve.