A novel approach for systematically deriving the complex poles and residues of a structure from a set of time-domain data is presented. The method is based on Prony's algorithm which involves the inversion of two matrices and a solution of the zeros of an n th degree polynomial, n being the number of desired poles. Two numerical examples are presented and several numerical advantages of this method are discussed.

A technique for extracting the poles and residues of a system directly from its transient response

A data processing technique, namely Prony's method, is evaluated. The use of the algorithm for EMP and other transient problems is illustrated and the relationship between the waveform parameterization and the singularity expansion method (SEM) is described. The impulse response of a synthesizer network is obtianed using Prony processing of the output of the double exponential excited circuit. Difficulties which arise in this type of processing such as rank deficiency, aliasing, and noise effects are considered and methods for alleviation such as filtering and rank-overspecification are introduced and evaluated. The overall status of waveform parameterization as applied to SEM is considered and suggestions for future research presented.

Evaluation of a processing technique for transient data

Integral equation methods for transient scattering

Lateral electromagnetic waves along a plane boundary between homogeneous half-spaces are reviewed. The electromagnetic fields generated by vertical and horizontal electric dipoles near the boundary between air and the earth (salt or fresh water, soil, ice, etc.) are summarized in terms of a new unified theory of lateral-wave propagation. Complete theoretically determined fields are displayed and compared with measured fields at f = 601 MHz relative to the boundary between air and salt water (σ = 3.5 S/m, e r = 80). Near, intermediate, and asymptotic fields are related graphically to the new general theory and to the approximate and restricted formulas of Norton and Banos as well as to the Zenneck wave. Application is made to the specific problem of communication with submerged submarines by means of transmitters consisting of electrically short monopoles in air and horizontal traveling-wave antennas and directional arrays in sea water. The properties of the antennas are evaluated in the frequency range 10 ≤ f ≤ 30 kHz which is optimum for receiver depths near 10 m, and at f = 1 kHz which is optimum for depths up to 50 m. The effects of reflections from the ionosphere and of the earth's curvature are not included.

Lateral electromagnetic waves along plane boundaries: A summarizing approach

A new simple formula is derived as an approximation for the general exact integrals for the radial component of the electric field generated by a horizontal electric dipole in a half-space of water or earth near its boundary with air. The field in the water or earth is investigated as a function of radial distance from the source for er = 80, 20, and 4, over wide ranges of conductivities and frequencies. Special attention is paid to the ranges in which the direct wave from the dipole produces an interference pattern of standing waves when it interacts with the lateral wave. For selected values of the parameters the radial electric field computed from the new simple formula is compared with the field evaluated numerically from the exact integrals. The agreement is excellent when the ratio of wave numbers characteristic of the denser half-space and air is large, quite good even when this ratio is as small as 2.

Lateral waves: a new formula and interference patterns

The behavior of electromagnetic surface waves generated by both elevated and buried sources is explained with physical reasoning and described with mathematical formulas. All combinations of source and receiver orientations are considered. Applications of generalized surface wave formulas for mixed-path and spatially varying terrains are discussed. The generalized surface wave formulas for elevated and buried sources are validated with Sommerfeld integrals and are applicable over a wider range than previous approximate surface wave formulas.

A physical explanation of electromagnetic surface wave formulas

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LLL transient electromagnetic measurement facility: a brief description

Although the real part of the complex Poynting vector, P→ cannot be strictly interpreted to indicate power flow, its previous use for this purpose has produced no logical inconsistencies. Results of Re(P→) for sources in lossy media, for plane waves interacting with a lossy half-space, and for Hertzian sources located near a lossy ground have been generated. The power flow results for these problems provide unexpected but physically consistent results.

E. K. Miller

Papers

A physical explanation of electromagnetic surface wave formulas

LLL transient electromagnetic measurement facility: a brief description

Poynting vector behavior in lossy media and near a half space