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Microwave Theory and Techniques, IEEE Transactions on

Issue 2 • Date February 1971

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Displaying Results 1 - 25 of 27
  • [Front cover - Feb. 1971]

    Page(s): f1 - f2
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  • Table of contents - Feb. 1971

    Page(s): 1
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  • Editor's note

    Page(s): 2
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  • Guest Editorial [Special issue intro.]

    Page(s): 2 - 3
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  • Introductory remarks [Special issue intro.]

    Page(s): 130
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  • The Tri-Service Program -A Tribute to George M. Knauf, USAF (MC)

    Page(s): 131 - 146
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    During World War II, the Department of Defense medical services became interested and concerned about possible hazards associated with the development, operation, and maintenance of the increasing numbers of RADARs and other radio-frequency emitting electronic equipment. After some investigations by the U. S. Navy and the U. S. Air Force, responsibility for research on the biomedical aspects of microwave radiation was delegated in July, 1957, as a tri-service arrangement to Rome Air Development Center, Griffiss Air Force Base, N. Y. Primary responsibility for coordination of the program rested with Dr. George M. Knauf, USAF (MC). The Tri-Service Program included investigation of effects of exposure of the whole-body, selected organs and tissues, single cells, and enzyme systems using various power levels, pulsed and continuous wave, in the frequency spectrum from 200 through 24 500 MHz under acute, subacute, and chronic conditions. The most important contribution of the Tri-Service Program was the validation of the 10-mW/cm/sup 2/ safety standard. The Tri-Service Program is to date the only large-scale coordinated effort in the Western world to elucidate and understand some of the basic mechanisms of microwave bioeffects and to assess possible health implications of this form of energy. This paper constitutes an overview of the Tri-Service Program to provide some historical insight into the significance of the program and its contributions to our understanding of the biologic effects of microwaves. The initiative, foresight, and drive of Colonel Knauf was an immeasurable contribution to the success of the program. View full abstract»

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  • Interaction of Microwave and Radio Frequency Radiation with Biological Systems

    Page(s): 146 - 152
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    A survey of thermal and nonthermal effects is presented with some recommendations for future work. A basis of all biophysical considerations are the electrical properties including dielectric constants and conductivities for nearly all body tissues. Equations are presented which summarize previous experimental work and state dielectric constant and conductivity for tissues of high water content as functions of macromolecular content and frequency. No evidence is available supporting resonance behavior. Previous thermal work includes determination of depth of penetration values and the relative absorption cross section of man and was the basis for present standards. Nonthermal principles which explain many previous observations are largely due to field-induced forces. Such effects occur in the human body only at field-strength levels which are thermally dangerous. Several important conclusions are made. 1) Field-force effects cannot be enhanced by use of pulsed fields. 2) It is not possible to directly stimulate nerve membranes by microwave fields. 3) It is fluids and tissues. Finally, a guideline for future standard work in complex fields is proposed. It is based on the concept of a tolerance current density, which is stated to be near 3 mA/cm/sup 2/ between 1 and 1000 MHz. The biophysical principles which pertain to the interaction of nonionizing electromagnetic radiations with biological systems are not discussed. This was done in the past on several occasions. The field will be summarized only briefly and attention will be given to problems not already delt with satisfactorily. We intend to concentrate on some topics that are presently of particular interest. View full abstract»

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  • Biological Function As Influenced by Low-Power Modulated RF Energy

    Page(s): 153 - 164
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    In recent years it has been recognized that low-power-density modulated RF energy can affect the functioning of higher living organisms. In this paper the sparse data generated in the western hemisphere on this subject are considered, the reasons for their sparseness are noted, and the hypotheses on mechanisms that may provide an explanation for the observed effects and other possible effects are sketched. Possible conclusions with regard to hazards to personnel are then considered. View full abstract»

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  • Microwave Radiation Safety Standards in Eastern Europe

    Page(s): 165 - 168
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    Research in Eastern Europe on biological effects of microwaves is briefly reviewed and a basic viewpoint involving non-thermal and cumulative effects is presented. Safety standards expressed in terms of dose or irradiation are described based on this viewpoint. It is suggested that differences between these standards and those in the West may become smaller with further study and closer collaboration between researchers in this field. View full abstract»

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  • Absence of Heart-Rate Effects in Rabbits During Low-Level Microwave Irradiation

    Page(s): 168 - 173
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    Soviet studies have reported that low-level microwave irradiation alters the heart rate of humans and animals. In a replication of one such study, 16 rabbits were exposed to dorsal irradiation n of the head by 2.4-GHz CW. microwaves at a power density of 10 mW /cm/sup 2/ for 20 min. The rest of the animal's body was shielded by absorbent material. There was no significant difference between the heart rate during or after irradiation and the heart rate of the same animals during a control condition in which they were not irradiated. Analysis of the variability in heart rate observed in this experiment suggested that the heart-rate effects reported in the original Soviet study might have been chance variations. In a second experiment, heart rate, respiration rate, and body temperature were recorded simultaneously while each of two rabbits was irradiated as before, on the dorsal aspect of the head only, at various power densities from 0 to 100 mW/cm/sup2/, in steps of 20 mW/cm/sup 2/. Respiration rate increased during irradiation at 40 mW/cm/sup 2/, body temperature rose at 80 mW/ cm/sup 2/, and ultimately the heart rate also increased, but only at 100 mW/cm/sup 2/. View full abstract»

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  • Evidence For Nonthermal Effects of Microwave Radiation: Abnormal Development of Irradiated Insect Pupae

    Page(s): 173 - 178
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    Several investigators have reported experiments in which microwave radiation caused biological damage at tissue temperatures which were not harmful when brought about by means other than microwaves. To study the effects of 10-GHZ CW radiation on a poikilothermic invertebrate animal, we irradiated early pupae of the mealworm beetle, Tenebrio molitor. Each pupa was inserted in a waveguide and irradiated therein at waveguide powers of 80 mW for either 20 or 30 min or at 20 mW for 120 min, after which their subsequent development was observed. In control groups similarly treated, except that no microwave power was applied, 90 percent metamorphosed to become normal adult beetles. In the irradiated groups only 24 percent developed normally; 25 percent died and 51 percent developed abnormally. In half of the abnormal animals, the front half had undergone metamorphosis to form a normal beetle head and thorax but the hind part remained in the pupal state. Temperature increases within pupae were recorded during irradiation. When these thermal conditions were duplicated by means of radiant heating, subsequent development of pupae was normal in 80 percent of the experiments. We therefore concluded that the abnormalities induced by microwave radiation were not a thermal effect. View full abstract»

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  • Quantifying Hazardous Electromagnetic Fields: Scientific Basis and Practical Considerations

    Page(s): 178 - 187
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    As commonly recognized, the problem of quantifying hazardous electromagnetic (EM) fields is difficult and has not yet been satisfactorily solved. Essentially, this is because people are often exposed to emanations from powerful sources of EM fields at points close to the sources and at points where arbitrary polarization and multipath interference exist. However, the accepted concepts, standards, and most measuring instrumentation are based on simple plane-wave field propagation and so are inadequate for complicated fields. The complications and problems of quantifying hazardous EM fields involving source-subject coupling, reactive near-field components, multipath components, and arbitrary polarization are examined in some detail General discussion of dosimetric measurements and hazard survey measurements is given, and also some basic considerations for the design of field probes for these measurements. Recommendations are given for suitable parameters for quantifying complicated EM fields, and essential and desirable characteristics for hazard survey meters are stated. Several recently designed hazard survey probes are capable of measuring these recommended parameters in many complicated fields of interest, and improved instruments are anticipated. View full abstract»

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  • Induced Fields and Heating Within a Cranial Structure Irradiated by an Electromagnetic Plane Wave

    Page(s): 187 - 196
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    The induced fields and the static heating patterns within a multilayered spherical model that approximates the primate cranial structure irradiated by plane waves in the microwave spectrum are calculated. The relation of the model to the biological structure and the sensitivity of the results to the uncertainties in the dimensions and electrical properties of biological material are investigated. A method of solution for both the scattered and the interior fields for a sphere with an arbitrary number of electrically different concentric layers is developed in a form readily amenable to machine computation. It is shown that the semi-infinite slab model is inappropriate for calculating the microwave radiation dosage for the human head and similar structures. View full abstract»

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  • New Techniques for Implementing Microwave Biological-Exposure Systems

    Page(s): 197 - 204
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    In investigating the biological effects of microwave radiation, one of the most vexing problems is that of generating an essentially uniform plane wave with sufficient power density for illuminating biological samples. This paper describes three illumination systems: a focused prolate spheroid, an absorber-lined horn, and a compact range. The focused prolate spheroid has two foci: a waveguide feed is located at one, and the biological sample is located at the other. Large power densities can be obtained over an area of about one square wavelength. The absorber-limed horn acts as a small source within an anechoic chamber; such an illumination system reduces errors due to interaction with the biological sample. The compact range employs a reflector and feed system to generate a plane wave across a large aperture; such a range is an attractive device for illuminating large volumes. All three systems can be implemented in a limited space without an anechoic chamber. Experimental data obtained from model systems are presented. View full abstract»

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  • Analyses of Electromagnetic Fields Induced in Biological Tissues by Thermographic Studies on Equivalent Phantom Models

    Page(s): 205 - 214
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    One of the most vexing problems in studies involving the interaction of electromagnetic fields and living biological systems and tissues is the quantification of the fields induced in the tissues by nearby sources. This paper describes a method for rapid evaluation of these fields in tissues of arbitrary shape and characteristics when they are exposed to various sources including plane wave, aperture, slot, and dipole sources. The method, valid for both far- and near-zone fields, involves the use of a thermograph camera for recording temperature disitributions produced by energy absorption in phantom models of the tissue structures. The magnitude of the electric field may then be obtained anywhere on the model as a function of the square root of the magnitude of the calculated heating pattern. The phantoms are composed of materials with dielectric and geometric properties identical to the tissue structures which they represent. The validity of the technique is verified by comparing the results of the experimental approach with the theoretical results obtained for the case of plane layers of tissue exposed to a rectangular aperture source and cylindrical layers of tissue exposed to a plane-wave source. This technique has been used successfully by the author for improving microwave applicators. View full abstract»

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  • Electromagnetic Fields and Relative Heating Patterns Due to a Rectangular Aperture Source in Direct Contact with Bilayered Biological Tissue

    Page(s): 214 - 223
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    Expressions are derived and evaluated for the electro-magnetic fields and associated relative heating patterns in two-Iayered biological tissue media exposed to a direct-contact rectangular aperture source. The source consists of a linearly polarized electric field distribution specified in the plane of the aperture. The results may be used for many biomedical applications ranging from the design of diathermy applicators to the establishment of standardized electromagnetic field intensities in connection with research on electromagnetic effects in living biological media. View full abstract»

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  • Microwave Heating of Simulated Human Limbs by Aperture Sources

    Page(s): 224 - 231
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    Microwave heating of phantom models of human limbs by aperture sources is investigated theoretically and experimentally. These phantom models consist of triple-layered circular lossy dielectric cylinders. The three layers of dielectric materials simulate human tissues of fat, muscle, and bone. In the theoretical investigation, apertures operating in the frequency range of 433 to 2450 MHz are used as microwave sources for heating the dielectric materials. The theoretical investigation makes use of the technique of summation of cylindrical waves. A high-speed computer is used to calculate the numerical results. For the experimental investigation, an aperture is designed and built to operate at the frequency of 918 MHz. The resulting temperature patterns in the phantom models are detected by the use of a thermograph camera. The theoretical results are shown to be in agreement with the experimental results. The technique and results of this investigation may be applied towards the design of applicators for therapeutic heating of human tissues. View full abstract»

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  • Determination and Elimination of Hazardous Microwave Fields Aboard Naval Ships

    Page(s): 232 - 238
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    A qualitative description of the way that the problems of radio frequency and microwave radiation hazards to personnel aboard Naval ships have been handled is presented. The prediction and measurement of microwave fields produced by typical equipment used for communication, command and control, surveilance, fire control, and naviagtion are discussed. A hazard evaluation survey conducted aboard a fictitious ship, which closely parallels that performed on actual ships, is described. Mentioned are the various methods and techniques used to define and control the potentially hazardous environment which is unique to the Navy. View full abstract»

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  • Selective Electromagnetic Heating of Tumors in Animals in Deep Hypothermia

    Page(s): 238 - 245
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    A technique for heating tumors with microwave energy has been developed to achieve differential hypothermia in laboratory animals. In the differential hypothermia technique, a temperature difference of about 25/spl deg/C is maintained between the tumor and the body with the tumor being at normal body temperature. While the animal is in this deep differential hypothermic state, chemotherapeutic drugs are administered to treat the tumor. For large tumors, the technique was implemented with S-band equipment and for smaller tumors it was implemented with X-band equipment. Both systems employ a feed or probe designed for use with the particular system. Results are presented that show the applicability of microwave energy in the selective heating of tumors. View full abstract»

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  • Prolongation of Life During High-Intensity Microwave Exposures

    Page(s): 245 - 247
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    In an attempt to determine whether environmental control would be a feasible and effective tool with which to further investigate microwave bioeffects, we have performed a pilot study. Osborne-Mendel rats were exposed in a Iucite environmental chamber, continually flushed with liquid-nitrogen-cooled air. The results of this study indicate that ambient air temperature control can provide a means for prolonging life in test subjects exposed to high-intensity microwave fields. Dosimetric considerations are presented in an attempt to relate heating curves to exposure conditions. View full abstract»

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  • Electromagnetic Fields and the Life Environment (Book Reviews)

    Page(s): 248
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  • Electromagnetic Fields and Life (Book Review)

    Page(s): 248
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  • Electromagnetic Radiation Meter (Correspondence)

    Page(s): 249 - 250
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    A radiation meter has been designed for the measurement of leakage from microwave ovens. A brief description of the meter is presented together with characteristics which suggest that the instrument has measurement applications other than that for which it was specifically designed. Some of the characteristics presented are geometry, temperature effects, frequency sensitivity, and conversion from calibrated power density to energy density. View full abstract»

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  • Microwave Cataract (Correspondence)

    Page(s): 250 - 251
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    The production of cataract by exposure to microwave radiation can occur, although just how it occurs is not well established. Clarification as to the occurrence of cataract in microwave worker population can only be achieved by careful cumulative records of the visual and ophthalmological status of microwave worker populations. View full abstract»

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Aims & Scope

The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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