Atmospheric effects on the propagation of very short pulses at millimetric wavelengths

An alternative approach to the solution of the Fourier integral in closed form was adopted by Terina (1967) for reflections from the ionosphere of pulsed HF (3-6 MHz) transmissions. This technique, appropriate to any line shape, assumes that the atmospheric channel transfer function can be approximated by a truncated Taylor series of frequency; its validity thus relies on the presumption that high-order terms can be neglected. Although this may not be strictly valid at frequencies very close to resonant absorption lines, the treatment allows an examination of a variety of phenomena arising from the dispersive nature of the atmosphere, such as the imposition of frequency modulation (chirp) on the carrier frequency within the pulse and the corresponding changes in the spectrum which arise through the frequency-dependent group velocity. This analysis has been considered briefly for line-of-sight transmissions near 55 GHz by Medeiros Filho et al (1983). The paper extends this to investigate absorptive and dispersive effects on pulses at carrier frequencies between 10 and 200 GHz, for pulse widths between 2 ns and 0.1 ns, for line-of-sight pathlengths from 1 to 50 km, and along Earth-space paths