A method of direction finding for dispersive electromagnetic pulses

A 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. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(5): 23–32, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20327