دانلود کتاب انتشار امواج رادیویی در سیستم‌های ماهواره‌ای

Reliable information about the propagation characteristics serves as the backbone for the design, fabrication, and operation of a satellite system. The transmission of radio signals from the ground users to the satellite in such a system must pass through the earth’s atmosphere, including the troposphere and the ionosphere layers. The effect generated on radio wave propagation by the earth’s atmosphere, the ground, and different coverings brings about a change in amplitude, phase, polarization, and angle of arrival of the Earth-space link signal, resulting in signal degradation and even grave system interruption; hence, it is vital to consider the effect of radio wave propagation on system performance as well as achievement of projected technical indexes in the system design. How radio wave propagation affects the functioning of the satellite system depends on the operating frequency, transmission method, angle of elevation toward the satellite, and local geographic, meteorological, and ionospheric environment. For example, while rain attenuation plays an important role in satellite systems operating at the Ku frequency band and above, it rarely affects satellite systems operating at the L frequency band; similarly, clutter reflections, fading, and shadowing emerge as instrumental factors responsible for affecting the performance of a mobile satellite system and are preventable by the selection of a proper terminal site in the fixed satellite system. While planning and designing a satellite system, a reliable formulation of the transmission link must be carried out in accordance with the statistical characteristics of radio wave propagation for the Earth-space link pertaining to diverse satellite systems, to enhance the environmental suitability of the link. During the functioning of a satellite system, fade dynamics, short-term forecasting, and near real-time forecasting can be utilized to ensure the smooth implementation of anti-fading techniques as well as the planning of system tasks.