Multi-hop HF Radio Propagation

The energy gradually decays during the propagation of radio waves. By analyzing the factors that affect the attenuation of wave energy, the energy loss model of radio waves in the ionosphere and the model of reflection and loss of radio waves on the sea surface are established.For problem one, firstly, by studying the relationship between wave and sea surface, we find that the dielectric coefficient, conductivity, and other factors will affect the wave propagation process. Combined with the absorbing principle of absorbing materials, a sea surface reflection model of reflectivity is established. Based on the principle of Gerstner model and MATLAB simulation, 3D wave pattern data based on PM spectrum are obtained, and the reflection intensity of the calm sea surface and the turbulent sea surface is calculated to be 95.1 W and 85.4 W. Secondly, the absorption loss of waves in the ionosphere is considered. By studying the structure of the ionosphere, the factors affecting the wave energy are found to be: electron density, atmospheric conductivity, dielectric coefficient. In order to simplify the study, only the absorption loss of layer D is considered. Finally, the loss of the electric wave on the sea surface is calculated. Based on the Longely-Rice model, the original model is further improved, and the two-path model is used to simulate the loss of the electric wave on the complex sea surface. From the relation between the initial signal-to-noise ratio of the radio wave and the total loss, the functional relationship between the number of hops and the initial signal-to-noise ratio is obtained. When the SNR threshold is not less than 10 dB, the maximum allowable number of hops is 3 hops when the SNR is 400 dB.For problem two, taking into account the terrain in the mountainous area height is obvious, we use Egli model to calculate the wave in the jump process, influence the ups and downs of the terrain on the radio. The radio wave propagation loss and loss in the sea were compared, concluded that: when the mountain height is getting lower and lower, the loss model of wave and mountain has certain universality. However, the loss model of the mountain will not be a good response to the energy loss on the sea. In addition, with the Okumura-Hata model we can draw a conclusion: due to the change of terrain height, rugged terrain will produce reflection and diffraction in the process of propagation, thus increasing the wave propagation loss. For problem three, on the basis of the sea loss model established by question 1, considering that the fluctuation of ship hull on the sea surface will have a great influence on the loss of the electric wave, the loss and correction coefficient of the electric wave passing through the hull can be added, which are designed to enable the model to respond to a more complex sea surface environment. In order to keep in communication and realize the signal without distortion when the ship sailing. The lower limit of signal-to-noise ratio is set to 70 dB. The initial signal-to-noise ratio is assumed to be 400 dB. According to the relation between initial signal-to-noise ratio and energy loss, the communication time of ship is calculated to be about 1.07 h.The analysis of the sensitivity of the model indicates that the change of propagation distance has little effect on the model, but the change of antenna height has a great influence on the model.