| In this thesis, the propagation characteristics of the Terahertz wave in several mediums are studied. The following works have mainly been done:1. The absorption model of THz wave in atmosphere is studied. By this model, the absorption rate of THz wave in the water air and oxygen are calculated. Then the effect of radius and complex refractive index of atmospheric particulate on the propagation of the Terahertz wave is analyzed by the Mie theory.2. Based on the propagation mechanism of hollow metallic waveguide, the main modes and attenuation coefficients of Terahertz wave in this kind of waveguide are analyzed. The impact of coating metal and internal radius of hollow metallic circular waveguide on the attenuation coefficients are discussed.3. The method of Finite-Difference Time-Domain (FDTD) for periodic structure is obtained by using the Floquet theory, and the periodic boundary condition and the total-field boundary are derived. The transmission characteristics of Terahertz wave in metallic periodic square hole arrays are studied.4. The fingerprint spectrums of two similar materials are compared by the principles of data processing in transmission THz time-domain spectroscopy (THz-TDS) technique. And combining the FDTD method with the double Debye model, the propagation characteristics of Terahertz wave in three different dispersive mediums are discussed.
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