Microwave Approach Research Articles

Combined optical and microwave approach for performing quantum spin operations on the nitrogen-vacancy center in diamond

Electron spin echoes were performed on nitrogen-vacancy $(\mathrm{N}\ensuremath{-}V)$ centers in diamond using optical polarization and detection and 35 GHz microwave control. The experiments demonstrate an approach to quantum information in the solid state. A phase memory time of $3.6 \ensuremath{\mu}\mathrm{s}$ was measured, and coupling of the electronic spin to the ${}^{14}\mathrm{N}$ nuclear spin was observed. Because of the favorable properties of the $\mathrm{N}\ensuremath{-}V$ center, interesting extensions of these single-qubit operations can be proposed.

On interactions of microwave with lightwave

This paper addresses interactions of lightwave with microwave, and is divided into two parts. In part one, the background and the main topics of the research filed are introduced. In part two, some research activities at Shanghai University are reviewed. These include optical control of microwave devices, photoinduced electromagnetic radiation, lightwave interaction with superconductors, microwave control of lightwave, and the microwave approach to highly irregular fiber optics.

A crack identification microwave procedure based on a genetic algorithm for nondestructive testing

This paper is aimed at exploring the possibility of using a microwave approach based on a genetic algorithm to detect a defect inside a known host object. Starting from the knowledge of the scattered field, the problem solution is recast as a two-step procedure. After defining a cost function depending on the geometric parameters of the crack, a minimization procedure based on a hybrid-coded genetic algorithm is applied. The influence of the noise as well as of the geometry of the defect on the crack detection and reconstruction is investigated. Moreover, the numerical effectiveness of the iterative approach is examined.

ChemInform Abstract: Recent Advances in Microwave‐Assisted Organic Syntheses

The application of microwaves to organic synthesis is opening up new opportunities for the synthetic chemist by providing new routes not practical by traditional means, such as improved reaction yields, solvent-free reaction conditions or decreasing the time needed for transformations. This is an area of synthesis that is rapidly developing. It is becoming clear that microwave approaches can be developed for most reactions requiring heating. The most interesting developments are those demonstrating the enabling of microwave reactions where traditional methods have failed or give only poor yields. This review intends to point out some of the more interesting papers in this area published over the last year or so, where the microwave method was demonstrated as clearly superior to previously available techniques or a new useful approach was presented.

AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors on SiC substrates

We report on AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors (MOS-HFETs) grown over insulating 4H–SiC substrates. We demonstrate that the dc and microwave performance of the MOS-HFETs is superior to that of conventional AlGaN/GaN HFETs, which points to the high quality of SiO2/AlGaN heterointerface. The MOS-HFETs could operate at positive gate biases as high as +10 V that doubles the channel current as compared to conventional AlGaN/GaN HFETs of a similar design. The gate leakage current was more than six orders of magnitude smaller than that for the conventional AlGaN/GaN HFETs. The MOS-HFETs exhibited stable operation at elevated temperatures up to 300 °C with excellent pinch-off characteristics. These results clearly establish the potential of using AlGaN/GaN MOS-HFET approach for high power microwave and switching devices.

Vertically positioned axially viewed aerosol cooled plasma — a new design approach for microwave induced plasma optical spectrometry with solution nebulization

A vertically positioned axially viewed argon microwave induced plasma (Ar-MIP) system is described, which can serve as a spectrochemical excitation source. The design concept of improved TE 101 rectangular cavity based on strong coupling between the plasma load and the magnetron generator has been presented. The idea of plasma cooling with a pure water aerosol is explained. The torch cooling system which permits aerosol generation and circulation has been described in detail. The influence of cooling on the argon plasma positioning in the discharge tube was investigated. The spectroscopic temperatures of iron and argon have been measured to evaluate excitation conditions and effect of plasma cooling. Analytical performance of the presented MIP system was characterized by determination of the limits of detection for some elements and comparison with other Ar-MIP experimental setups. Analysis of certified reference material was performed to determine the accuracy and precision available with the presented system.

Interaction between moderately high power microwaves and plasma in corrugated wall waveguides

Local protuberances in negatively biased probe current (NBPC) after the incidence of moderately high power microwave pulses in a plasma-filled corrugated waveguide are observed. The aim of the present experiment is a fundamental study in the research of high power plasma-filled backward wave oscillators. Protuberances in NBPC profile and the peaks of standing waves of the RF electric field are observed always at the identical axial positions where the radius of the corrugated wall is the minimum. The electron energy distribution after the incidence of the microwave approaches the Druyvesteyn distribution rather than conventional Maxwellian distribution that is observed before microwave incidence. The protuberances in NBPC are found to consist of a uniform increase in electron temperature and of a localized rise in plasma density that is calculated from ion saturation currents. Physical reasons for the observations are discussed in some detail.

MICROWAVE MEASUREMENT-PARAMETER OPTIMIZATION FOR DETECTION OF SURFACE BREAKING HAIRLINE CRACKS IN METALS

Fatigue and stress induced hairline surface crack detection in metals is an important practical issue. A newly developed microwave inspection approach, using an open-ended rectangular waveguide, has proved to be an effective tool for detecting such cracks. This novel microwave approach overcomes some of the limitations associated with the standard detection methods for surface crack detection. In addition, this approach is applicable to exposed and filled cracks (with a dielectric such as dirt, rust, etc.), and cracks under dielectric coatings such as paint and composite dielectric laminates. This paper briefly presents the basic foundation of this surface crack detection methodology. More importantly, this paper focuses on the ways by which measurement parameters may be optimized for increased crack detection sensitivity. Theoretical as well as experimental results are provided.

Integration of air-gap transmission lines on doped silicon substrates using glass microbump bonding techniques

Air-gap transmission-line structures have been fabricated and integrated on doped silicon substrates using glass microbump bonding (GMBB) techniques. The air-gap transmission lines have the advantages of low losses and low dispersion compared to conventional uniplanar transmission lines on semiconductor substrate. This bonding technique provides an alternative approach for both monolithic microwave integrated circuits (MMICs) and optoelectronic integrated circuits (OEICs) on silicon substrates. To demonstrate the potential of air-gap structures, several transmission-line configurations are fabricated and tested. The measured data are compared with simulation results. The results confirm the air-gap structures low-loss capabilities. To further explore the advantage of this bonding technique, several spiral inductors are fabricated in air-gap configurations. Their measured characteristics demonstrate the low dispersion potential of this technology. Finally, the integration of air-gap interconnects for OEICs on silicon CMOS circuitry is also proposed.

A layout approach to monolithic microwave IC

A layout approach for monolithic microwave integrated circuits (MMICs) is described, in which layout elements are transistors, inductors, capacitors, resistors, coplanar waveguides, etc., implemented in a GaAs fabrication process. The layout issue typical of such MMIC's consists essentially in how to realize a single-layered placement of different shapes of layout elements under a variety of spacing and orienting constraints as well as shape variations. In this paper, the interconnection requirements among the elements are represented by a graph, to which a planarization algorithm is applied. On the basis of the planarization result, the physical placement is first constructed with the use of a merging scheme and then refined iteratively by means of a new rectangle-packing algorithm. Experimental results are also shown to demonstrate the practicability of the described layout approach.

Low Temperature Antigen Restoration of Steroid Hormone Receptor Proteins in Routine Paraffin Sections

The most widely used non-enzymatic method for unmasking antigens prior to immunohistochemical staining is based on immersion of deparaffinized paraffin sections in citrate buffer and exposure to high temperature heating (100°C) with a microwave. In our experience, the benefits of this technique as applied to cytoplasmic proteins does not routinely translate to the nuclear estrogen and progesterone receptor (ER and PgR) proteins. The lifting or loss of portions of a breast biopsy section can seriously interfere with efficient scoring of invasive tumor cells. The use of low temperature restoration (80°C) in citrate buffer using a water bath avoids problems of tissue disruption and generally restores the immunoreactivity of ER and PgR proteins in a more uniform fashion than does the microwave approach. (The J Histotechnol 20:155, 1997)

Low Temperature Antigen Restoration of Steroid Hormone Receptor Proteins in Routine Paraffin Sections

The most widely used non-enzymatic method for unmasking antigens prior to immunohistochemical staining is based on immersion of deparaffinized paraffin sections in citrate buffer and exposure to high temperature heating (100°C) with a microwave. In our experience, the benefits of this technique as applied to cytoplasmic proteins does not routinely translate to the nuclear estrogen and progesterone receptor (ER and PgR) proteins. The lifting or loss of portions of a breast biopsy section can seriously interfere with efficient scoring of invasive tumor cells. The use of low temperature restoration (80°C) in citrate buffer using a water bath avoids problems of tissue disruption and generally restores the immunoreactivity of ER and PgR proteins in a more uniform fashion than does the microwave approach. (The J Histotechnol 20:155, 1997)

Remote sensing applications to hydrology: soil moisture

Abstract Passive and active microwave remote sensing instruments are capable of measuring the surface soil moisture (0–5 cm) and can be implemented on high altitude platforms, e.g. spacecraft, for repetitive large area observations. The amount of water present in a soil affects its dielectric properties. The dielectric properties, along with several other physical characteristics, determine the microwave measurement. In addition, the significance of the dielectric properties depends upon the sensor design, especially the wavelength. Instruments operating at longer wavelengths (> 5 cm) have fewer problems with the atmosphere and vegetation, sense a deeper soil layer and maximize soil moisture sensitivity. Another instrument concern is whether to use an active or passive microwave approach. Active approaches, especially synthetic aperture radar, can provide extremely good ground resolution from space (< 100 m). Passive methods currently provide much coarser resolution data (> 10 km). The existing data interpretation algorithms for passive data are well tested for bare soil and vegetation and can be applied to a wide range of conditions. At the present time, the active microwave algorithms have not been widely verified. There has been a significant amount of recent research using both active and passive methods as a result of the availability of new sensor systems. With these new instruments have also come greater efforts to integrate the observations in large scale multidisciplinary investigations. A greater emphasis on the spatial distribution and temporal behaviour of soil moisture has produced some very interesting and valuable data sets that demonstrate the potential of a dedicated observing system for scientific and operational studies.

Microwave heating systems for atmospheric pressure: Nonequilibrium plasmas

Nonequilibrium plasma-chemical processing is attracting increasing interest because of the possibility of creating mixtures of active species that would not be available in thermal equilibrium. For significant throughput of reactants it would be advantageous to create nonequilibrium plasmas in large volumes of atmospheric-pressure mixtures of gases. Techniques for accomplishing this are very limited at present. Here we describe a novel microwave approach to creating nonequilibrium plasmas in large volumes of atmospheric-pressure gases using pulses of microwave radiation with very high peak power that are focused by quasi-optical techniques at one or more points in the interior of the reaction chamber. A new type of microwave source, the Plasma Electron Microwave Source (PEMS), is able to produce the required power levels by storing cw microwave power in a mirror-confined, relativistic-electron plasma and periodically transforming a fraction of that stored energy into intense microwave pulses. This approach avoids many of the limitations inherent in resonant cavity approaches and is expected to permit ultrahigh purity discharges to be produced.

Principal Electrical Conductivities in the Organic Conductors TEA.(TCNQ)2 and TTF.TCNQ: The Microwave Approach

Abstract We describe a microwave technique to measure the directions and magnitude of the principal electrical conductivities and permittivities of organic conductors. The method is applied to single crystals of triethylammonium-bis 7,7,8,8-tetracyano-p-quinodimethane (TEA.(TCNQ)2) and of tetrathiafulvalenium-7,7,8,8-tetracyano-p-quinodimethane (TTF.TCNQ). For the former, the apriori set of principal axes (a*, (a*∧c), c) is confirmed with principal conductivities of 430, 5.3 and 0.41–0.77 Ω−1m−1 respectively. The room temperature permittivities have been measured for the first time (ε*α ∼ 5.4–5.5, ε*α∧c ∼ 7.5). For the latter it is clearly shown that the principal electrical axes are (a, b, c*) and, in contrary to earlier d.c data, we observe σc· < σ<a which is more consistent with the anisotropy of interchain interactions in this compound. The observed transverse and longitudinal anisotropies (∼3.3 102 and 2.8 104 respectively) are larger than believed up to now.

The Spectral-Domain Approach for Microwave Integrated Circuits

A survey is given of the so-called spectral-domain approach, an analytical and numerical technique particularly suited for the solution of boundary-value problems in microwave and millimeter-wave integrated circuits, The mathematical formulation of the analytical part of that approach is described in a generalized notation for two- and three-dimensional strip and slot-type fields. In a similar way, the numerical part of the technique is treated, keeping always in touch with the mathematical and physical background, as well as with the respective microwave applications. A discussion of different specific aspects of the approach is presented and outlines the peculiarities of shielded-, covered-, and open-type problems, followed by a brief review of the progress achieved in the last decade (1975-1984). we survey closes with considerations on numerical efficiency, demonstrating that spectral-domain computations can by speeded up remarkably by analytical preprocessing. The presented materal is based on ten years of active involvement by the author in the field and reveals a variety of contributions by West German researchers previously not known to the intenational microwave community.

Remote Sensing of Soil Moisture: Recent Advances

In the past few years there have been many advances in our understanding of microwave approaches for the remote sensing of soil moisture. These advances include a method for estimating the dependence of the soil's dielectric constant on its texture; the use of percent of field capacity to express soil moisture magnitudes independently of soil texture; experimental and theoretical estimates of the soil moisture sampling depth; models for describing the effect of surface roughness on the microwave response in terms of surface height variance and the horizontal correlation length; verification of the ability of radiative transfer models to predict the microwave emission from soils; and experimental and theoretical estimates of the effects of vegetation on the microwave response to soil moisture. This research has demonstrated that it is possible to remotely sense soil moisture in the surface layer of the soil (about 0-5 cm). In addition there have been simulation studies indicating how remotely sensed surface soil moisture may be used to estimate evapotranspiration rates and root-zone soil moisture.

Strategic considerations in SETI, and a microwave approach

The only practical way we know now to actively test the hypothesis that life exists outside the Solar System, depends on an intelligent fraction of that life providing an electromagnetic signature we can recognize over interstellar distances. The nature of the local universe, a relatively mature microwave technology, recent digital solid state developments, and a minimal number of ad hoc assumptions, suggest a promising set of initial strategies of exploration for a range of possible electromagnetic artifacts. As a consequence, the Ames Research Center (ARC) and the Jet Propulsion Laboratory (JPL) are pursuing a moderately broad program using existing radiotelescopes and automated, state-of-the-art electronics, with the objective simply to detect and identify a relatively strong, relatively narrowband, essentially steady, intelligent, non-human, microwave signal. There are two main parts to this approach. In a companion paper, R. E. Edelson (JPL) discusses a survey over 80% of the sky in the 1–25 GHz band, with a frequency resolution of ∼ 300 Hz and to a sensitivity in the range of 10 −19 to 10 −21 W/m 2. The second half of the approach (ARC) discussed here, is a study primarily of neighboring F,G,K, “target” stars in the 1.4–1.7 GHz band, with a frequency resolution of ∼ 1 Hz and to a sensitivity of 10 −25 to 10 −27 W/m 2. Whether or not a detection is achieved, the combined approaches should reduce our present uncertainties by many orders of magnitude, as well as provide valuable astrophysical information.

Theoretical Basis for Decision to Microwave Approach for Industrial Processing*

ABSTRACTTheoretical formulae facilitating a decision to adopt a microwave approach for industrial processing in contrast to a conventional approach are introduced. Factors considered include energy, power, utility current, quality of the products, speed, cost, payback period, and profit. Some examples are given.

Application of Microwave Concepts to the Theory of Acoustic Fields and Waves in Solids

During the past 20 years the value of the microwave approach to electromagnetic field problems has been amply demonstrated. The purpose of this paper is to show the basic similarity of acoustic and electromagnetic field equations and to exploit this fact in applying microwave methods to acoustic resonator and waveguide problems. This is accomplished most directly and efficiently by using symbolic notation, rather than tensor subscripts, for the acoustic fields. The usefulness of this notation is illustrated by the problems of plane wave propagation and piezoelectric stiffening in an anisotropic medium, and by derivations of Poynting's and reciprocity theorems for a piezoelectric medium. Piezoelectric resonators are treated in detail from the point of view of normal mode expansions. A general network representation is obtained and is applied to the disk transducer, as an example. Normal mode theory of piezoelectric waveguides is briefly sketched and a perturbation theorem, which can be applied to both resonator and waveguide problems, is derived.