부산대학교 도서관

The propagation of electromagnetic signals through atmosphere is affected by absorptive and dispersive processes present therein. The resulting attenuation increases in adverse weather conditions. The loss of signal power due to scattering of electromagnetic waves in free space, is one of the most common hazards in ultrafast wireless communication systems. The scattering of signal is caused by the suspended atmospheric hydrometeors. Moreover, due to the humidity of the atmosphere, the defocusing of the electromagnetic beam, known as scintillation, may occur. In this paper, the authors, for the first time, have presented a comprehensive analysis of terahertz (THz) signal attenuation along with scintillation effect, in fog-laden atmosphere of Indian subcontinent under tropical climatic belt. The frequency-dependent properties of the signal attenuation have been analysed using an indigenously developed Non Linear Terahertz Attenuation Model (NLTAM)simulator. Moreover, the difference between single and multiple scattering effects of THz signal has also been presented here. The nature of THz signal attenuation spectra in foggy atmosphere, agrees closely with experimental findings, for near THz or IR signal transmission in fog-based aerosols weather scenario in both tropical and non-tropical regions. The experimental study at MMW regime was carried out through radiometric measurement of fog attenuation at Kolkata (220N, tropical region) and the results are compared with the NLTAM model data for reliability verification. The signal attenuation is found to be $\sim \,\,16\times 10^{5}$ dB/Km around 2.0 THz frequency. By incorporating parametric variations in the present simulator, the authors have estimated the reliable range of THz signal energy, coming out of atmospheric fog-layer. The authors have developed a separate reliability model to address this aspect of study. To initiate a comparative analysis on the prediction of attenuation of THz wave for different types of scattering mechanisms, especially in foggy atmosphere, under tropical climatic region, a novel technique has been developed and reported by the authors for the first time.