On the Distortion of the Leading Edge of a Quasi-Monochromatic Signal in a Resonantly Absorbing Medium

Abstract

The paper is concerned with the distortion of a sharp leading edge of a quasi-monochromatic electromagnetic (light or radio) signal (wave packet) propagating in a medium with an absorption line (or band). It is shown that the frontal jump of the complex envelope of a radio signal propagates without changing its magnitude. Behind the leading edge, the signal level decreases with a rate increasing with the path length. As a result, the leading and trailing (if it exists) edges of the signal acquire tooth kinks, which become more and more acute with increasing path length. Such tooth kinks are formed not only at the points of discontinuity of the real amplitude of a signal but also at the points of discontinuity of its phase; therefore, the propagation of a phase-shift keyed radio signal in a resonantly absorbing medium is accompanied by its “self-disclosure”.