Distortions of a Chirp Radio Pulse in Resonant Absorbing Atmosphere

摘要

Formulas for the envelope and the instantaneous frequency are obtained for a chirp electromagnetic pulse whose carrier frequency coincides with the resonance frequency of a single spectral line of one of the gas components of the atmosphere, while the spatial length is much greater than the wavelength of radiation. The main feature of the distortion in the envelope of a frequency-modulated pulse is that its maximum, initially sin- gle, gradually decomposes into a series of maxima, whereas the main feature of the variation of the instanta- neous frequency during the pulse is its short (as compared with the impulse length) spikes. The magnitude of these spikes may exceed both the frequency deviation in the pulse and the spectral linewidth.