Reception and Transmission of Transient Electromagnetic Fields

Hans J. Schmitt

Jän. 1963 · Sandia Corporation

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The receiving and transmitting properties of small linear antennas, conical antennas, and loops for transient electromagnetic fields were investigated experimentally. Short electrical dipoles loaded by a capacitance represented by a cathode follower can be used successfully for the measurement of transient fields with rise times of less than 1 nanosecond, if the first antenna resonance is suppressed by a series resistor at the base of the antenna. The currents induced on nonresonant structures by transient electromagnetic fields are investigated and their application to a direct measurement of the time sequence of the electromagnetic field is discussed. Signals with a simple and known time dependence such as a unidirectional pulse can be radiated into space if the reflection of current waves at discontinuities of the antenna structure is avoided. In a manner similar to that useful for the absorption of continuous waves in media with a stratified conductivity, it is shown that reflections at discontinuities can be avoided by dipoles with tapered resistive loading. (Author).