Research On Terahertz Radar System And Its Signal Processing

Terahertz wave is a very important research domain recognized by the domestic and overseas academic circles nowadays, which is a valuable undeveloped frequency resource. Compared to the traditional millimeter wave radar, the advantages of terahertz radar system are as follows. First of all, the shorter wave length is favorable toward providing a wider bandwidth, which could benefit higher precision of imaging. Secondly, the narrow antenna beam in terahertz band could not only obtain higher antenna gain in radar LOS, improving the ability of multi-target discrimination and recognition, but also reduce the opportunity of main lobe jamming.The technology of Terahertz is developing rapidly because of the great attention by developed countries, such as USA and Germany, in which, the experimental radar system have been researched and developed.By the rapid development of terahertz technology, terahertz system could be applied in the domain of the target imaging, environment monitoring, safety inspection and anti-terrorism detection, especially in satellites communication and imaging radar. The capability of high resolution of terahertz wave can enhance the ability for spatial perception. Therefore, the research on terahertz can not only benefit to the level of information acquisition and detection, but also promote the technology of terahertz development.On the other hand, electromagnetic wave will be absorbed strongly by vapor and oxygen in terahertz band due to the interaction between polar molecule and incident wave will induce strong absorption and the water coagulum (e.g. raindrop, fog, snowflake, frost and cloud etc.) will cause additional attenuation. Meanwhile, it is still of much difficulty to produce high power frequency source and high sensitivity detection device. Thus a new frame of terahertz radar system is needed, which could be suitable for the present situation of terahertz technology and make full use of the performance of these components.Whereas, the huge difference between terahertz wave and microwave in frequency and wavelength will induce some distinction on target detection, especially in micro-doppler phenomenon. This phenomenon provides a new concept of target detection, recognition, and imaging. But it may reduce the performance of detection if we still use the traditional detection method. So a new target detection method for terahertz radar system is needed.In consideration of the above, the work for this subject has been done as follows:1. To design a terahertz radar system. Aiming at design transmitting and receiving subsystem, we chose suitable parameters of radar system and demonstrated the system's key technical indexes in detail. Then, we presented a feasible terahertz radar system model and make simulation to verify the validity of this system.2. To research on the phenomenon of micro-doppler. In this dissertation, we discussed the typical model of micro-doppler, and quantitative analyzed them by joint time-frequency method. From this analysis, we could find out the difference between terahertz and microwave, which could be beneficial to target detection. Then, the feature extraction of micro-doppler has been done for high resolution imaging or target recognition.3. To analyze the influence of micro-doppler for target detection under terahertz band. Discussion the performance losses of ascertained signal detection method when micro-doppler is existing. Then, we presented a model for target detection which has micro motion and simulations were done for performance verification.4. To research technology for radar system integration. We integrated the components of radar system which have been done, and tested the performance of this system, such as the transmitting power, the noise figure, and so on. Then we did the experiments to verify the functions of radar system.In this dissertation, we presented a feasible terahertz radar system frame, and verified the functions after implementing it. In addition, we researched the algorithm for target detection method, which has micro motion. It is the foundation for further research on terahertz radar system.