Microwave Resonance Method Research Articles

Dielectric Properties of Heterogeneous Mineral Compositions Based on Bentonite and Gypsum

To interpret the well-known experimental fact of reducing the depth of GPR diagnostics of railway subgrades in arid regions, the properties of model samples of mineral compositions formed by adding gypsum to bentonite at low moisture were studied. Using electron microscopy, the microstructure of bentonite and the compositions of bentonite and gypsum were studied with various methods of introduction of gypsum. Dielectric permittivity is studied by the microwave resonance method in the GPR frequency range of 1200 - 1700 MHz. The influence of the interaction of water and gypsum, as well as the Maxwell-Wagner dielectric effect on dielectric permittivity of heterogeneous mineral compositions, depending on the concentration of the components, is estimated.

Microwave Resonance Method for Measuring Microliter Volumes of Free Moisture of Aviation Fuels

One of the conditions for ensuring the safety of air transport operation is the quality of aviation fuel refueled in aircraft. Fuel quality control is a multi-parameter task that includes monitoring the free moisture content. Regulatory documents establish the free water content of not more than 0.0015 wt.%. A direct electrometric microwave resonator method for controlling free moisture in aviation fuels has been developed. The method consists in measuring the resonance characteristics of a cylindrical cavity resonator. At that, on a solid dielectric surface inside the resonator, there are moisture drops that are pressed by a thin plate. As a result, dielectric losses increase dramatically. Analytical and experimental analyses of the proposed method are carried out. The monitoring range of 0.5–30 μl of the absolute moisture volume in aviation fuels with a maximum error of no more than 25% is justified. The sensitivity of the proposed method for monitoring microwave losses in free moisture drops transformed into a thin layer by pressing with a thin plate is an order of magnitude higher than the sensitivity of the method for monitoring microwave losses in moisture drops on a solid surface in a resonator. The proposed method can be used as a basis for the development of instruments for monitoring the free moisture of aviation fuels in airfi eld and laboratory conditions. The direction of development of the method is shown.

Microwave resonance method for measuring microliter volumes of free moisture in aviation fuels

One of the conditions for ensuring the safety of air transport operation is the quality of aviation fuel refueled in aircraft. Fuel quality control is a multi-parameter task that includes monitoring the free moisture content. Regulatory documents establish the content of free water no more than 0.0015% by weight. It is developed a direct electrometric microwave resonance method for controlling free moisture in aviation fuels, which consists in changing the shape of the water drops by pressing them on a solid surface inside a cylindrical cavity resonator. This can dramatically increase dielectric losses. Analytical and experimental analysis of the proposed method is carried out. The control range from 0,5 to 30 μl of absolute volume of moisture in aviation fuels with a maximum error of not morethan 25 % is justified. The sensitivity of the proposed method for monitoring microwave losses in free moisture drops transformed into a thin layer by pressing is an order of magnitude greater than the sensitivity of the method for monitoring microwave losses in moisture drops on a solid surface in a resonator. The proposed method can be used as a basis for the development of devices for monitoring the free moisture of aviation fuels in the conditions of the airfield and laboratory. The direction of development of the method is shown.

Multi-Channel, Microwave-Based, Compact Printed Sensor for Simultaneous and Independent Level Measurement of Eight Liquids

Industrial automation relies on sensing the process parameters like liquid levels. Simultaneous sensing of multiple fluids is especially useful for many automation processes involving multiple ingredients. Some of the desirable features in any level sensor are its non-intrusiveness, high accuracy, and consistent performance. These features can be achieved with typical microwave radar-based level sensors. However, this paper presents a microwave resonance method instead of typical microwave reflectance (radar) to reliably sense the liquid level at fraction of the cost using a unique printed sensor. In addition to that, sensor design presented in this paper enables sensing liquid level of eight liquids simultaneously and independently utilizing its multiple channels. An array of eight modified microwave T-resonators has been compactly packed inside a metallic cylinder of just $4$ diameter where the resonators share the same ground plane. Sensors’ performance, to measure the unknown level of eight different fluids (with dielectric constant ( $\in _{\mathbf {r}}$ ) ranging from 2.8 to 80), has been measured in real time using a custom-built software. Simple one point calibration procedure has also been proposed in this paper which has resulted into measurement accuracy of ~0.6% which is better than 1%, realizable with high-end and expensive radar based level sensors

Experimental Research on Granule Moisture Measurement by Microwave Resonance Technology in a Fluidized Bed Dryer

Drying is one of the most important methods for industrial processing while the granule moisture is a critical quality attribute (CQA) which has a significant influence on the finished product quality. In-line measurement of granule moisture during fluidized bed drying is getting more imperative to meet more stringent product quality specifications. Nowadays, several methods have been applied to measuring the granule moisture in-line. Comparing to other methods, microwave resonance (MR) technology provides more representative results due to its independency of both the particle density and the bed density. In the current study, one MR sensor was mounted onto an industrial fluidized bed dryer to monitor the real-time moisture of granules. The drying experiments were performed at different drying air temperatures and flow rates. The comparison between the results of in-line and off-line granule moisture measurements, namely MR technology and loss on drying caused by infrared light (LOD/IR), was presented. Furthermore, the influences of inlet air temperature and flow rate on the performance of the MR sensor were investigated. As a conclusion, the MR method, which is independent of the drying air temperature and flow rate, provided more accurate results when the granule moisture was below 25% (wet basis). Therefore, it is a promising method to be applied in real-time measurement of the granule moisture and predict the end-point in fluidized bed drying processes as well.

Comparison of near infrared and microwave resonance sensors for at-line moisture determination in powders and tablets

In this paper we demonstrate the feasibility of replacing KF for water content testing in bulk powders and tablets with at-line near infrared (NIR) or microwave resonance (MR) methods. Accurate NIR and MR prediction models were developed with a minimalistic approach to calibration. The NIR method can accurately predict water content in bulk powders in the range of 0.5–5% w/w. Results from this method were compared to a MR method. We demonstrated excellent agreement of both NIR and MR methods for powders vs. the reference KF method. These methods are applicable to in-process control or quality control environments. One of the aims of this study was to determine if a calibration developed for a particular product could be used to predict the water content of another product (with related composition) but containing a different active pharmaceutical ingredient (API). We demonstrated that, contrary to the NIR method, a general MR method can be used to predict water content in two different types of blends. Finally, we demonstrated that a MR method can be developed for at-line moisture determination in tablets.

Increasing the speed of microstrip-line-type polymer-dispersed liquid-crystal loaded variable phase shifter

We discuss a method for the production of microwave polymer-dispersed liquid-crystal devices. We also show how to obtain a fine grained uniform fibrous polymer network. We then measure how the microwave-band dielectric properties and response-time characteristics of microstrip-line-type polymer-dispersed liquid-crystal devices vary with polymer concentration, and we measure how their response-time characteristics vary with the thickness of the polymer-dispersed liquid-crystal layer. With a layer thickness of 50 /spl mu/m, an applied voltage of 100 V and a polymer concentration of 7 wt%, we show that the decay time can be reduced to approximately 1/30th that of a plain liquid crystal at the expense of an increase in rise time of approximately 2.5 times and a deterioration of dielectric birefringence of approximately 50%. Finally, we discuss the results obtained with a prototype polymer-dispersed liquid-crystal loaded variable phase shifter in the 15-GHz band. By comparing the variable phase and response time of this phase shifter with basic experimental data obtained by the microwave resonance method, we verified the validity of these values.

Measurement Methods of Nematic Liquid Crystal Response Time

ABSTRACT We have proposed two methods for measuring liquid crystal response times using a microwave resonance method and an optical transmitted light measurement method. In this paper, the response time characteristics for the paralleled nematic and twisted nematic liquid crystal layer structures were investigated by using two different proposed measurement methods. The results obtained with these two different methods can be compared quantitatively by clarifying the physical meaning of the response time of each method. Also the transition performance of response time for the microstrip-line type liquid crystal devices was measured by using the proposed microwave resonance method.

Estimation of Frequency Accuracy and Stability in a Diode Laser-Pumped Rubidium Beam Atomic Clock Using a Novel Microwave Resonant Method

Experiments on a diode laser-pumped rubidium (Rb) beam atomic clock are carried out. A novel microwave resonance method (HORR) with a conventional cylindrical cavity is used. On the basis of the experimental results, the expected frequency accuracy of 1.4×10-12 is theoretically estimated with this clock. A frequency stability as high as 7.8×10-13 τ-1/2 is also estimated.

Lamb shift in singly ionized helium.

The Lamb shift ($n=2$) in $^{4}\mathrm{He}^{+}$ has been measured in a beam of metastable helium ions by means of the microwave resonance method. Our result is 14.0420(12) GHz which is in good agreement with the theoretical result based on the binding correction of Mohr, 14.0423(5) GHz.

Determination of moisture content of concrete by microwave-resonance method

The moisture content of concrete is one of its important properties. A new method of measuring the moisture content of concrete and other building materials is described. The method is based on the measurement of the dielectric constant at microwave frequencies. Studies on concrete have shown that a linear relation exists between the evaporable water content of concrete and the instrument reading. The main advantages of this method are i) it is nondestructive, ii) rapid response of the instrument, iii) humidity gradients in the specimen can be studied iv) measurements are independent of the dielectric losses and the conductivity of the material, v) sharp resonance peak of the microwaves allows very accurate measurements.

A study of the phase relations in ionization waves in neon with the aid of a microwave resonator method

The following paper describes the generalization of the microwave resonance method for measuring the phase between relative changes of the concentration and collision frequency of electrons. It also presents the results of measuring the phase between the above-mentioned parameters of plasma in neon, in which slow and fast ionization waves are propagated which, have been obtained by the described method.

Measurements of electric dipole moments by a microwave resonance method

Aus dem Temperaturverlauf der Dielektrizitatskonstanten wurde das elektrische Dipolmoment einiger Gase bestimmt. Das Verfahren benutzt den Vorteil hoher Resonanzgute von Hohlraumresonatoren fur 9400 MHz. Wahrend der eine Resonator nacheinander das Versuchsgas und ein bekanntes Vergleichsgas enthalt, wird der andere durch Variation des Gasdruckes auf Frequenzkoinzidenz eingestellt. Mit der behelfsmasig aufgebauten Versuchsapparatur wurde eine Genauigkeit von ca. 2·10−6 in e und ca. 6% fur das Dipolmoment erreicht. Der Versuch zeigte aber, das die Genauigkeit des Verfahrens wesentlich gesteigert werden kann, d.h. auf nahezu 10−7 in e. Die Methode kann leicht ausgebaut werden zu Absorptionsmessungen; dazu mussen nur die Verstarker geeichte Eingange erhalten, damit die Variation der Gute der Resonatoren gemessen werden kann. Ein Nachteil der Apparatur besteht in der fixen Frequenz. Dadurch hat man keine Anhaltspunkte, ob zufalligerweise ein Absorptionsband in der Nahe des Mespunktes liegt, was die Messungen stark beeinflussen kann. Es wurde sich lohnen, zu versuchen, die Methode auszubauen fur Messungen auf einem kontinuierlichen Frequenzband z.B. von 3000÷30000 MHz.