Propagation of a Rectangular Radio Pulse with a Chaotic Phase in a Resonance-Absorbing Gas Media
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TRODYNAMICS AND WAVE PROPAGATION
Propagation of a Rectangular Radio Pulse with a Chaotic Phase in a Resonance-Absorbing Gas Media G. M. Strelkov* Kotelnikov Institute of Radioengineering and Electronics, Fryazino Branch, Russian Academy of Sciences, Fryazino, 141190 Russia *e-mail: [email protected] Received November 2, 2018; revised November 2, 2018; accepted January 11, 2019
Abstract—In this study, we analyze the possible nature and characteristics of dispersion distortions of a rectangular nanosecond radio pulse with a chaotic phase modeled based on a Chebyshev map of the first kind of the third order during propagation in a resonant-absorbing gas medium. The removal of the pulse from the emitter is shown to be accompanied by the transformation of the envelope to a noise-like form and the formation of its “tail,” which can account for a noticeable fraction of the current energy. It was established that, in a sufficiently wide range of parameter values describing the degree of randomness of the instantaneous phase of the emitted pulse, the effect of the medium does not lead to the destruction or fundamental changes in the form of its correlation functions during the propagation process. DOI: 10.1134/S1064226920080112
INTRODUCTION One of the modern directions in the development of radio systems for various purposes is pulse signals, the characteristics of which change randomly (chaotically) (see, for example, [1–5]). Such signals have wide spectra, including the ability to increase the secrecy and noise immunity of the systems and have several other advantages compared with regular ultrawideband signals. At the same time, the research results published to date completely lack an analysis of an important aspect of the problem associated with the effect of the propagation medium on the characteristics of chaotic signals. This situation is primarily due to the fact that dispersion distortions of signals are always considered based on the Fourier integral while the characteristic widths of the amplitude and phase spectra of chaotic signals are such that they apparently prevent direct numerical estimates of the level of distortions. A solution to the problem of the propagation of a radio pulse in a resonance-absorbing gas medium that is based on the temporal representation of the signal and, therefore, is not a result of the calculation of the Fourier integral is given in [6]. The principal feature of the solution is the possibility of an analytical description based on this representation of the spatiotemporal evolution of the pulse, provided that the refractive index of the medium is slightly different from unity in the frequency range occupied by its spectrum. For Earth’s atmosphere, in particular, the indicated differ-
ence in the giga- and terahertz ranges does not exceed ~10–4 (see, for example, [7–9]). This study is aimed at presenting the results of the initial stage of theoretical analysis based on the problem of dispersion distortions in a resonance-absorbing medium of a rectangular radio pulse with a
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