Waveforms and Relative Phase Stability of Transients Radiated from a Helicopter-supported Antenna Wire
Waveforms and Relative Phase Stability of Transients Radiated from a Helicopter-supported Antenna Wire

Author: E. A. Lewis

Publisher:

Published: 1965

Total Pages: 18

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A nearly vertical antenna wire varying in length from 3000 to 8000 ft was shock-excited by a high-voltage source. The resulting radiation fields were received at distances of about 600 km by two stations separated laterally so as to subtend an angle of about 15© at the source. The difference in wavefront arrival times at the two stations, observed for 101 transmissions, showed an average absolute deviation from the mean of about only 1/2 [mu]s. This figure includes the effects of possible source asymmetries, sferics noise, instrumental errors, and wave propagation. Typical oscillograms of antenna currents and radiation fields are given. It is shown that the amplitudes and durations of the pulse envelopes, the amplitudes and durations of the first half-cycles, and the quasi-frequencies of the pulses are in good agreement with a theory that takes energy losses into account.

Asymptotic Solutions of Dipoles in a Semi-infinite Medium
Asymptotic Solutions of Dipoles in a Semi-infinite Medium

Author: Kondagunta U. Sivaprasad

Publisher:

Published: 1965

Total Pages: 62

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A theoretical analysis is made of the electromagnetic fields in two homogeneous media separated by a plane interface with a point source located in the denser medium. The solution is expressed in the form of integrals which cannot be evaluated explicitly. Asymptotic evaluations of the integrals have been made by many investigators using the saddlepoint technique. In the present work, all known asymptotic results are presented in one comprehensive form, using a modification of the method suggested by Lighthill for the asymptotic evaluation of the Fourier integrals. The regions of validity of the solutions are indicated wherever possible. The advantage of this method over others is its ease and simplicity. The present results agree term by term with the earlier ones of Banos and Wesley (1953-1954), and Paul (1959), who investigated the case of a source and receiver close to the interface, and an arbitrary location of source and receiver, respectively. The results obtained in the report are also compared with those of Stein (1955). (Author).

The Application of a System of Fixed-rotating Vectors to Circuit Analysis and Synthesis
The Application of a System of Fixed-rotating Vectors to Circuit Analysis and Synthesis

Author: Carl T. Case

Publisher:

Published: 1965

Total Pages: 22

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A system of fixed-rotating vectors can be used to study the impedance loci of functions of the first Foster form and of systems including negative impedance converters. Of particular interest in the field of dielectrics and biological membrane studies is a parallel RC network, where the dielectric of the capacitor is given by the Debye dispersion relations. Such a network also falls into the category of the first Foster form.

Earth-to-space Communications at Millimeter Wavelengths
Earth-to-space Communications at Millimeter Wavelengths

Author: Edward E. Altshuler

Publisher:

Published: 1965

Total Pages: 46

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It is expected that with the exploration of outer space, a requirement for high data rate earth-to-space communication channels will arise. A program to investigate the feasibility of using the millimeter-wave region of the spectrum for this application is presented. The theory of atmospheric attenuation resulting from losses due to absorption, scattering and refraction processes is reviewed and used to estimate propagation losses produced by atmospheric gases, clouds and precipitation. Curves of total atmospheric attenuation and noise level as a function of meteorological parameters and antenna elevation angle are also presented. A series of experiments designed to obtain as much information as possible on the limitations imposed by the atmosphere on millimeter-wave propagation is considered. Although experiments using natural celestial bodies such as the sun, moon, planets and galaxies as radio sources are emphasized, those which would utilize aircraft, rockets and satellites are also mentioned. Finally, the characteristics of a recently installed precision 29-ft antenna designed to operate at 35 Gc (wavelength = 8.6 mm) with a traveling-wave maser as a preamplifier for the radiometer are outlined along with the specific experiments for which this antenna system will be used. (Author).

Nonlinear Terms in the Generalized Ohm's Law
Nonlinear Terms in the Generalized Ohm's Law

Author: Noel Stone

Publisher:

Published: 1965

Total Pages: 58

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It is shown that a spatial gradient in the steady flow of an ionized gas introduces terms into the generalized Ohm's law that represent an exchange of momentum between the electrons and the gas flow. Depending upon the flow geometry and gas compressibility this electrokinetic exchange can behave like a generator, a Hall current, or a resistive current. The scale of the phenomenon is L = +/V, where V is fluid velocity, + is electron-positive charge collision time. Electrokinetic conditions apply largely at boundaries. In a resistive medium with a static B-field, the principal condition for electron-flow interchange is that magnetic pressure dominate dynamic pressure. At the boundary of a plasma jet the scale over which EK terms are important is of the order of 1 mm. Only geometry and scale considerations are used in the momentum equation. The electrokinetic generation of surface currents is as fundamental for describing moving media as spacecharge effects are in the static case. (Author).

On the Theory of Boolean Formulas
On the Theory of Boolean Formulas

Author: E. W. Samson

Publisher:

Published: 1965

Total Pages: 38

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The theory of substitutions for Boolean formulas developed in a previous report is applied here to the determination of those s-tuples of formulas that may be allowable replacements for s -tuples of sub-formulas of given Boolean formulas. The criteria of allowability are very general and flexible, yet may be expressed with great precision and ease. The results formalize and extend various known isolated instances. They may be used for the study of a large number of problems in the theory and application of Boolean formulas and functions.