A method of direction finding for dispersive electromagnetic pulses

Abstract

SUMMARYA new measurement method which can determine the direction of arrival of a pulse electromagnetic wave with frequency dispersion characteristics has been developed. The direction of arrival is determined by conventional data analysis for an electric field component and two magnetic field components. The sensor system is composed of a vertical dipole antenna and two search coils oriented in perpendicular directions in the horizontal plane. The major part of the analysis of the detected signal is composed of the derivation of the spectrum with frequency dispersion from the pulse waveform and the calculation of the direction of arrival from the amplitude and the phase obtained for each frequency in the dispersion characteristics. By the proposed method, the direction of arrival can be determined even when a frequency-dependent delay is produced in propagation (frequency dispersion). The method is applied to lightning discharge pulses, and it is shown that the direction of arrival can be determined with high accuracy. Thus, the method can be used for continuous observation.

Various Compositions to Form a Triad of Collocated Dipoles/Loops, for Direction Finding and Polarization Estimation

“…4) The {e z , h x , h y } triad has been investigated in [25]- [29], with closed-form estimation formula available for the azimuth arrival angle in [26], but no closedform estimation formula is available for the elevation 1 Real antenna patterns depend on frequency. The array manifold would not depend on frequency if all antennas have the same frequency-dependence.…”

Method of Pointing Source Locations of Earth-origin Electromagnetic Pulses as a Precursor of Earthquakes

“…are, respectively, the vertical electric field and the horizontal magnetic field in each frequency component f . The detailed procedure for obtaining these field components is described in the previous paper (6) . A plausibly true arrival direction of the detected EM pulse is determined among them and drawn on a map of a computer display.…”

Spatial Distribution of Source Locations of Earth-origin Electromagnetic Pulses Excited before Earthquakes

“…We have developed an analysis method for deriving f − t forms from impulsive waveforms of detected EM pulses (2) . The right part in Fig.…”

“…We have developed a specific analysis method for deriving frequency dispersion characteristics (f − t form) of impulsive signals. Furthermore, using amplitudes and phases in all frequency components in the f − t form, we could obtain an exact arrival direction of an EM pulse (2) . We could determine propagation distances of EM pulses and could identify their source locations.…”