Near earth propagation: physics revealed

R. Wert; A. Goroch; E. Worthington; V. Wong

doi:10.1117/12.720560

11 May 2007 Near earth propagation: physics revealed

R. Wert, A. Goroch, E. Worthington, V. Wong

Proceedings Volume 6562, Unattended Ground, Sea, and Air Sensor Technologies and Applications IX; 65620F (2007) https://doi.org/10.1117/12.720560
Event: Defense and Security Symposium, 2007, Orlando, Florida, United States

Abstract

Both the military and consumer sectors are pursuing distributed networked systems and sensors. A major stumbling block to deployment of these sensors will be the radio frequency (RF) propagation environment within a few wavelengths of the earth. Increasing transmit power (battery consumption) is not a practical solution to the problem. This paper will discuss some of the physical phenomena related to the near earth propagation (NEP) problem. When radiating near the earth the communications link is subjected to a list of physical impairments. On the list are the expected Fresnel region encroachment and multipath reflections. Additionally, radiation pattern changes and near earth boundary layer perturbations exist. A significant amount of data has been collected on NEP. Disturbances in the NEP atmosphere can have a time varying attenuation related to the time of day and these discoveries will be discussed. Solutions, or workarounds, to the near earth propagation problem hinge on dynamic adaptive RF elements. Adaptive RF elements will allow the distributed sensor to direct energy, beam form, impedance correct, increase communication efficiency, and decrease battery consumption. Small electrically controllable elements are under development to enable antenna impedance matching in a dynamic environment. Additionally, small dynamic beam forming arrays are under development to focus RF energy in the direction of need. With an increased understanding of the near earth propagation problem, distributed autonomous networked sensors can become a reality within a few centimeters of the earth.

Citation Download Citation

R. Wert, A. Goroch, E. Worthington, and V. Wong "Near earth propagation: physics revealed", Proc. SPIE 6562, Unattended Ground, Sea, and Air Sensor Technologies and Applications IX, 65620F (11 May 2007); https://doi.org/10.1117/12.720560

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