Basic Research On Baseband Signal Processing And External Modulation Techniques In THZ Communication System Based On External Modulation

With the development of wireless communication technology, the frequency band has become increasingly scarce resources, the existing frequency band can not meet people’s demands for high speed communications. Therefore, the terahertz communication systems emerge at the right time. Compared to other THz communication systems has been completed at present, THz communication system based on direct external modulation has its irreplaceable advantages: modulator is independent of terahertz source to facilitate its independent research, and be flexible to match different terahertz source, the system can achieve relatively large transmission power in this way, and the modulation performance of the whole system depends on Terahertz external modulator itself. Therefore, the research of the modulator, key device in THz communication system based on external direct modulation, is rather important. To test the performance of the system, the research of baseband information transmission is also very important. The main contents and results are as follows:1、Compared several classes of THz communication systems’ performance and the technology they used, introduced the THz wireless communication system based on direct external modulation.Given a brief introduction to terahertz external modulation technology and further studied the modulation techniques based on Metamaterials. On the basis of the performance of VO2 film and the theory of Metamaterials designed a cell structure of terahertz modulator based on VO2 and Metamaterials through electromagnetic simulation, analyzed the results and found out that how the structure make an effect on the resonance frequency and the absorption of terahertz wave.2、Prepared the sample of terahertz modulator based on VO2 and Metamaterials using MEMS technology. Using time domain spectroscopy system system TPS3000 to test the sample and the test result matched the simulation result very well, proving the reliability of design method and processing method. The static and dynamic experimental results show that the designed modulator based on VO2 and Metamaterials has a good modulation effect near the target frequency 0.34 THz.3、combined with external modulation THz wireless communication system, proposed initial program of baseband data transmission, and completed the data transmission of sending side based on the FPGA design method, providing a stable and reliable THz modulation signal to the external modulator. Given a preliminary configuration to AD sampling platform on the receiving side, made it possible to work and to achieve the corresponding functions. Carry out a preliminary joint trial for THz wireless communication system based on direct external modulation by Using the baseband transmission scheme raised in the issue, the eye diagrams of 50 Mbps, 100 Mbps, 150 Mbps signal were achieved respectively in the experiment to prove the feasibility of transmission scheme,and given the foundation for the following research.