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This work is divided into two parts: A theoretical study and a discussion of actual applications. In the first part, a brief introduction of the common antenna synthesis procedures is presented. Two new novel approaches were also suggested. First, the use of the signal-to-noise ratio as a criterion of design of arrays. Second, the use of the prolate spheroidal functions for aperture synthesis. In the second part, a number of high performance antennas as well as experimental work performed in the University of Pennsylvania is discussed. Practical techniques, such as tunneling application of microwave absorbing material, are described and evaluated., See also AD609077.

Section I is concerned with a theoretical and experimental study of coupling to the TE11 mode in a coaxial line in the presence of TEM signals. Bethe's small hole coupling theory is used to derive design equations. Section II is concerned with a study of techniques for measuring interpulse noise. Four techniques were explored. These were: Diode Switch, Ferrite Switch, TR Switch and a Pulse Inverter. The determination of the important parameters needed for the evaluation of the performance of microwave antennas is given in Section III. Section IV is concerned with methods for generating and measuring standard fields in the 1 to 10 Gc region. This research was entirely theoretical and considered only the dipole antenna. An updated collection of patterns and gain of antennas at harmonic frequencies is given in Section V. The effects of impedance missmatch and polarization are included. Section VI is concerned with the nonlinear effects of Signal Transmission. Section VII is concerned with the evaluation of antenna patterns measured in anechoic chambers. (Author), In cooperation with The Moore School of Electrical Engineering, Philadelphia, Pa.

Experimental studies were undertaken to evaluate if pulsed fields may act differently on biological systems than continued fields of the same average power. The conclusion of this work confirmed theoretical predictions that field evoked forces act at best as CW fields of the same average power. Calculations which concern the possibility of creating 'hot spots' in tissues by microwave irradiation were performed. The conclusion of this work is that hot spots are possible in objects with a radius of curvature up to 5 cm, but not likely in man. Animal work is therefore not necessarily of significance for man., Presented at the Proceedings of Defense Electromagnetic Research Workshop, held at Washington, D.C., on 27-28 Jan 71.

The report presents an analysis of the physical and electrical characteristics of a plasma jet for the purpose of using the plasma column as an antenna. The report presents a first order approximation synthesis of an argon arc jet in air, at atmospheric pressure. The jet is in the shape of a cylindrical column of high temperature laminar flow for a considerable length (approximately one meter) and terminates abruptly because of turbulent mixing with air. Along the extension of the laminar flow, the sole important loss mechanism is assumed to be radiation. The equation of energy balance allows computation of the axial temperature distribution, and, therefore, the axial conductivity distribution. An approximate solution for the current distribution on a cylindrical antenna with axially varying conductivity is obtained. Coupling the conductivity distribution obtained into the solution for the current distribution, it is shown that the argon arc jet can provide a highly capable UHF antenna. For antennas in the HF range it is suggested that combustion jets be utilized. The proper conductivities may be obtained by seeding with low ionization material. (Author)

An experimental analysis has been made of the harmonic performance of a half-wave dipole element fed by a balun from a coaxial transmission line. The impedance of 10 presumably identical elements was measured over a five to one frequency range in free space. The impedance of one element was measured over a large ground plane. The coupling impedance was measured between dipole pairs separated by a half-wave length for parallel, end fire and 45 degree orientations when mounted on the ground plane. The impedance of the center element of a 3 x 3 array was also measured over the five to one frequency range. Patterns of the center element of a 3 x 3 array (the other elements terminated in short circuits or 50 ohm loads) were measured over a five to one frequency range. The performance of the presumably identical antennas was found to vary considerably even in the design band. At harmonic frequencies the variation was sufficiently great as to suggest that such measurements may be meaningless. (Author), See also Volume 7 Appendix 6, AD-830 023.

By the help of local operations in digital picture processing it is possible to display special picture informations corresponding to the case of application. With a density interval an equidensity film is simulated. Second order equidensities can be extracted directly from the original picture by additional application of the first derivation. The equidensity areas can be counted. The equidensities of mixed order which are combinations of first and second order equidensities are effected by a quantisation process with the following derivation of the picture and some additional conditions. The use of a well known physiological effect allows a pseudoplastic display of the pictures. (Author), Text in German. Summary in English.

The eikonal equation as derived by Sommerfeld and Runge has been extended to include the case of moving media under the condition where v/c << 1 (v is the velocity of the medium, c is the speed of light in vacuum). Using the Hamilton Jacobi formalism, the equivalent system of linear equations was determined which can be used for ray tracing. An example of a moving medium where the index of refraction is a function of one of the coordinates has been considered. (Author)

The reflection coefficient of a plane monochromatic electromagnetic wave incident on an idealized laminar plane stratified jet stream is determined. This is accomplished by applying the principle of invariant imbedding to derive a differential equation for the reflection coefficient. The differential equation which is of the Riccati type is solved approximately for the case of a jet stream with a parabolic velocity profile. (Author)