In this thesis, firstly, based on the MATLAB/Simulink platform, the simulation channel module for terahertz wave (300GHz) communication is established based on the MPM modeled clear sky atmospheric channel,and Hamming (7,4) and RS (188,204) channel compilation code and 2FSK, QPSK, 16QAM signal modulation and demodulation, which are commonly used in the traditional frequency bands, are selected to form a simulation model of terahertz communication system. By comparing the BER analysis, it is found that Hamming (7,4) coding and QPSK modulation technology can achieve relatively low BER, but the traditional modulation and coding method has poor performance in terahertz communication at low SNR.Then,the experiments conducted on the wireless communication system controlled by LabVIEW on the PXIe platform confirmed and validated the conclusions derived from the simulations.
6G wireless communication technology is expected to provide a higher peak data rate, lower latency, high mobile speed, high spectral efficiency, and high network energy efficiency in the future. It has the advantages of wide coverage, high security, and low-cost efficiency. As one of the candidate frequency bands of 6G technology, THz wave (0.1-10 THz) bridges the infrared band and the microwave band and has a very important application prospect in the communication process. Due to the terahertz source power and the absorption of various particles in the air, indoor short-range terahertz wireless communication has practical research value. In this paper, for the three-dimensional scene of common indoor conference rooms, the ray tracing method is used to model the terahertz channel of the line-of-sight (LOS) path, the primary reflection path, and the secondary reflection path. The carrier frequency range used for the simulation is 220-330 GHz. By calculating the power loss and required time of each path from the transmitter to the receiver, parameters such as the power delay profile are obtained. Then, the related terahertz channel parameters such as Rician K-factor and root mean square (RMS) delay spread are analyzed.
Terahertz (THz) technology has become popular worldwide as a new approach to detecting biomolecules because the vibrational and rotational energy levels of many biomolecules fall in the THz band and because the THz wave has the characteristics of low electronic energy, which will not damage the samples to be measured. Many biomolecules need to maintain their biological activity in liquid environment. However, as a polar molecule, water has a strong absorption of THz wave, which is mainly because the vibration frequency of hydrogen bond in aqueous solution is within the THz frequency range. Therefore, the best solution is to reduce the action distance between the aqueous solution and THz wave and control it within 100 μm. Microfluidic chips can meet such requirements. Therefore, the combination of THz technology and microfluidic technology can study the dynamic characteristics of biomolecules in an aqueous solution. The microfluidic chip was fabricated using ZEONOR 1420Rs. The THz transmittance of the material can exceed 95%. The depth of the microchannel in the microfluidic chip is 50 μm. In addition, the chip has the characteristics of good airtightness, portability, convenient disassembling, and reusability. Seventeen kinds of electrolytes were tested with the chip. The results show that the THz spectral intensity of electrolyte composed of different anions and cations, so the spectral characteristics of other electrolyte solutions can be obtained according to the spectral information of these detected ions.
Terahertz spectroscopic characteristics are related to the large amplitude vibration of molecules and their interaction, so it can be used for molecular detection. Sodium nitrate and sodium nitrite are two very important salts in people's lives. Sodium nitrate is usually used as quick-acting fertilizer in acidic soil, but excessive use will cause certain pollution to the environment. If sodium nitrate is heated, it becomes very stable sodium nitrite, which is usually added to food as a preservative and colorant, but excessive consumption of nitrite can lead to food poisoning and even death. Therefore, it is necessary to detect sodium nitrate and sodium nitrite. Based on THz-TDS system, the spectral characteristics of sodium nitrate and sodium nitrite in 0.1-1 THz band were studied. Polyethylene, sodium nitrate and sodium nitrite were mixed in proportion of 1:1, 1:2, 1:3, 1:4 and 1:5, respectively. The mixture was evenly grinded and stirred, and then pressed. The prepared samples were tested in THz-TDS system, and the time-domain spectra of the samples with different proportions were obtained. The terahertz frequency spectrum and absorption spectra of the two samples at different ratios were obtained by Fourier transform. After comparing spectra of the two samples, it is found that they have their own absorption peaks, and their peak positions are obviously different. Therefore, it is very important to study these two substances by terahertz technology.
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