Abstract
The reflections of high frequency (HF) radio waves between ionosphere and earth’s surface make long-distance information transmission possible. In this paper, the propagation process of radio signals was analyzed and the ionosphere was simplified. Considering the strength loss of signals that occurs in the travelling process and at the reflection points, two pairs of differential equations and integral equations were established to simulate the strength variations of HF radio waves and noises. A different equation of SNR was also developed, which utilized the failure threshold of signal-noise-ratio (SNR) as a criterion to evaluate the effectiveness of signals. Meanwhile, the pace of SNR attenuation was simulated when reflections happens on calm ocean, turbulent ocean, smooth terrain and rugged terrain.
Highlights
On high frequencies (HF, defined to be 3-30 MHz), radio waves can travel long distances by multiple reflections off the ionosphere and off the earth
2.1 Physical model simplification Considering the propagation of high frequency (HF) radio waves between the ionosphere and the earth as a process from one point to another distant point on the earth’s surface, the assumption was made that both the ionosphere and the earth’s surface can be considered as two curved surfaces which do not intersect (Fig. 1)
The propagation of HF radio waves can be simplified to a process in which the waves travel up and down at a certain angle between the two curved surfaces
Summary
On high frequencies (HF, defined to be 3-30 MHz), radio waves can travel long distances (from one point on the earth’s surface to another distant point on the earth’s surface) by multiple reflections off the ionosphere and off the earth. The characteristics of the reflecting surface determine the strength of the reflected wave and how far the signal will travel while maintaining useful signal integrity
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