Adaptive Techniques to Correct for Effects of Ionospheric Refraction in Navigation, Surveillance and Communications Systems.

摘要

The following research work has been performed: (1) adaptive procedures to correct ionospheric variability in time delay and range error measurements of radio waves (2) seasonal and diurnal studies of total electron contents (TEC) at Ascension Island ( ) effects of ionospheric modification caused by high power, HF radio waves (4) Faraday polarization fluctutations (FPF) of satellite signals in transionospheric propagation. Multiplicative and additive prediction functions are used as adaptive procedures to estimate and compare their effectiveness in correcting ionospheric variability in time delay and range error measurments of radio waves. Post-sunset TEC enhancement and sudden sharp changes in the TEC are the two striking characteristic features of the night-time ionosphere at Ascension Island. Some nonlinear phenomena, caused by powerful, HF radio waves in the ionosphere, are analyzed theoretically, such as ion line enhancement, the excitaiton of upper hybrid modes or field-aligned plasma lines, and field-aligned non-oscillatory ionospheric irregularities. A mechanism has been proposed to explain the FPF of satellite signals in HF and VHF bands in their trans-ionospheric propagation.