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Much has been written about Faraday and Marconi and about the history of the development of radio from the time of Marconi. However, Gerald Ganatt's special interest was in what might be termed the 'pre-history of radio'. The book therefore outline the sequence of development from Faraday's first prediction and concept of the electromagnetic field. Maxwell worked out the mathematics of electromagnetic wave propagation and here demonstrated their physical existence. Lodge identified the need of resonance between transmitter and receiver, thus leading Marconi's successful practical application.

PCVLF is a data acquisition program that collects, stores, and displays electromagnetic field amplitude values for a list of frequencies. PCVLF is a personal computer version of a HP-BASIC VLF data acquisition program previously used on Hewlett-Packard portable computers.

This thesis models induced magnetic fields from the motion of seawater in the Earth's magnetic field analytically and compares the results to arctic on-the-ice magnetic fluctuation measurements. The oceans have various types of internal motions, such as internal waves and turbulence. This motion of sea water, which is a conductor, in the earth's magnetic field induces a current density. The current density, in turn, induces its own magnetic field. This thesis models internal waves and upper layer ocean turbulence analytically. The corresponding induced magnetic fields are calculated using a static form of Maxwell's equations and parameters for the Arctic are inserted. comparisons are made with measurements from the Arctic Internal Wave Experiment (1985). The predicted fields from internal waves have magnitudes that are measureable and of the same order of magnitude as ionospherically generated fields, The predicted fields from turbulence are several orders of magnitude smaller than ionospherically generated fields. Besides giving information about internal motions in the ocean, the seawater induced fields are a noise source in magnetic anomaly detection.

This dissertation examines aspects of the interaction of multiple coherent light fields for the two-photon two-level model. In this model the interacting energy levels are not connected by an atomic dipole and a two-photon transition between them is necessary. We employ the density matrix formalism allowing easy comparison between the one- and two-photon two-level models. Significant differences are found due to dynamic Stark shifts and conjugate scattering off the pump-induced two-photon coherence. Averages over Doppler broadening are performed and the new upper-level relaxation mechanisms of decay to an intermediate nonresonant level and ionization from the upper state are included. The new relaxation mechanisms, introduced to the theory to better model experiments, are similar except that ionization is intensity dependent. They cause the resulting probe absorption spectra to become more complex and in general asymmetric. Doppler broadening is also important in experiments using gases. We analytically average over a Lorentzian velocity distribution for both co- and counterpropagating pump and probe beams. For copropagating fields the results are similar to those for the one-photon case averaged over inhomogeneous broadening, whereas counterpropagating pump and probe fields yield the so-called Doppler-free configuration that is normally only modelled to third order in the pump amplitude. We consider the pump field amplitude to all orders and find that as long as the width of the Doppler velocity distribution is significantly larger than the two-photon Rabi frequency the results are Doppler-free. The final part of the dissertation treats the question of two-photon squeezed states. This requires quantized sidemodes. Squeezed states are minimum uncertainty states with unequal variances in the two quadratures of the electromagnetic field amplitude. One way to generate these states is via multiwave mixing and we present here the first calculation for nondegenerate two-p

Discussion begins with a brief account of atomic level-pumping and reasons why atomic coherence is typically not considered in cw work on optical interactions. This dissertation is divided into four parts: semiclassical treatments of one-photon electric- dipole atom-field single-mode interactions and multimode interactions, and corresponding treatments for the two-photon interaction. We present the effects of injected atomic coherence on the polarization of the medium, the slowly varying envelope wave equation, the single- and multiwave mixing coefficients, and weak field propagation in a homogeneously broadened two-level medium. Spatial and temporal phase matching of the injected coherence to a field mode is crucial throughout, since the field may not be able to remain in phase with the induced and injected polarizations. One-photon injected coherence contributes directly to the polarization at the atomic resonance frequency. The perfectly phase-matched case leads to a linear superposition of an exponentially decaying field (Beer's law) and a constant field driven by the injected coherence. The interaction of an injected coherence with a detuned field produces frequency-symmetric sidebands about the pump field polarization. The sideband spacing equals the atom-field detuning. To probe the injected coherence we inject a weak resonant field. The resulting three-wave mixing leads to multiwave mixing coefficients that are unaffected to first-order in the weak sidemodes, but the injected coherence adds inhomogeneous terms to the coupled-mode equations. For both single- and multimode interactions the injected coherence does not affect the exponential growth/decay of the sidemodes, but it supports a weak field that may propagate if properly phase matched. For two-photon media the injected coherence requires at least one field interaction in order to produce a polarization, which then appears in the single- and multiwave mixing coefficients. The exponential growth/decay ra

Major work during this quarter has been the testing of the PCM-FM receiver-demodulator, evaluation of test results, consideration of worst case electromagnetic fields encountered in typical field deployment, and appraisal of specific test procedures and instrumentation within the confinement of MIL-STD-461 and MIL-STD-462. The rationale for recommending a specific set of interference structure and interference injection points combines results and recommendations of previous quarters' activities with the real time required for susceptibility testing of the simulation. The susceptibility test results of the PCM-FM receiver-demodulator are included along with preliminary appraisal. There were no unique susceptibility functions of the PCM-FM receiver; polarity reversals of the baseband data signal during the center of the sampling interval represented the major cause of error production. Instantaneous peak jitter in excess of approximately 70 degrees consistently produced errors. Average jitter was less consistent. Interference test results were well aligned to predictions from previous analyses. Comparison of specifications in MIL-STD-461 and MIL-STD-462 with field levels, calculated from a typical field deployment, indicate some possible suggestions for modification in the areas of like interference structures and pulsed radar interference testing.

The effects of electromagnetic interference (EMI) on microelectronic circuits were investigated on a component basis to establish a methodology for a practical measurement technique to determine these effects. This investigation resulted in the development of breadboard instrumentation capable of subjecting microelectronic devices to radiated electromagnetic fields, and procedures to define and measure the effects of these controlled environments in terms of the device parameters. Essential to the implementation of this program were (1) a thorough microelectronic device characterization, (2) classification and definition of electromagnetic fields, and (3) design and fabrication of breadboard instrumentation capable of generating these fields and radiating the microelectronic devices under investigation. The semiautomatic test method developed and test data obtained during this program utilized low-level generators in conjunction with low-level device parameters. This approach of using a low-level indicating parameter, such as 'inherent ambient noise' of a device in the frequency domain, has provided the groundwork for predictive techniques to determine the effects of EMI on a device's response. (Author)

Research and development work is described on a traveling-wave power amplifier tube employing transverse-wave interaction between the negative synchronous wave and a circuit wave on a balanced structure. The theoretical advantage in this arrangement is the possibility of high-power amplification with high overall efficiency, due to the lack of longitudinal or transverse velocity modulation in the spent beam. No d-c pumping process is involved, so that such a tube should be free from noise orbit pumping or beam blowup. Theoretical and experimental work on a circuit composed of a twisted, finned, ridged, circular waveguide has shown that an appropriate dispersion curve, as well as adequate interaction impedance, can be obtained at S-band. A completed RF circuit including all necessary transitions and input and output RF windows has exhibited broadband coupling from 3.5 to 4.6 GHz.

A formulation has been obtained suitable for determining the radiation patterns of scalar feed modes by evaluation of diffraction integrals on a digital computer. The problem of the excitation of scalar feed modes in the case of circular waveguide dominant mode input has been programmed for the computer and a large number of cases have been run. Problems have been encountered with the singularities of the modes at the vertex and an improved formulation has been obtained and programmed. The effect of the circular cylindrical geometry on the normal surface reactance X of the corrugated structure has been derived and it has been shown to be negligible for the most part, so that the flat plane values of X may be used. (Author)

The concept of using a volume of a colloidal ferromagnetic liquid, rotating at high speed under the influence of an applied electromagnetic torque as a gyroscope is studied. Two different experimental arrangements are described. Electromagnetic torques are applied at a variable rate, from 50 to 50,000 cycles per second, to a 2 cc volume of ferromagnetic liquid. The ferromagnetic liquid used is a water base colloidal suspension of finely divided magnetite. The rotation of the liquid volume caused by viscous coupling to the particles is observed at a maximum rate of over 4 revolutions per second. The bulk fluid rotation rate is observed to pass through a maximum value as the rate of the applied field is increased, and it is demonstrated to depend on the square of the magnitude of the field. A prior theory, predicting fluid torque and rotation, taking into account the disorienting forces acting on the particles, is adapted for a multidisperse colloid and numerical computations are given for the fluids used in the experiments. The experimental observations follow the predicted trends. (Author)

A theoretical model based on the linearization of the fluid equations and Maxwell's equations for wave interaction in a uniform plasma which is interpenetrated by a nonrelativistic electron beam is developed. The effects of electron-neutral and electron-ion collisions and temperatures of both the beam and plasma electrons are included and no quasi-static approximation is made for the electromagnetic field. An external d.c. magnetic field is assumed to act so that a general formulation is developed which is valid in the limit of small d.c. magnetic fields and in the limit as the field becomes very large. Graphs of the computer solutions are given for the propagation constants in a beam-plasma system for the cases of an unbounded system and for the TM wave solutions that may exist in an axisymmetric cylindrical system in which the finite beam interpenetrates an unbounded plasma. (Author)

The report reviews some of the more recent quantum mechanical aspects of photon counting, optical coherence, and the space-time correlation of a lightbeam. The coherent states of the radiation field are defined in terms of the photon number states, and it is seen that these coherent states are the best ones to describe a classical radiation field, in that photon number and phase have an exact compromise for these states. A short discussion of the phase state is given. Many properties of the coherent state are described, and the density matrix for a mixed coherent and noise field in the photon number representation is given. (Author)