Research On Millimeter-wave Generator Based On Feed Forward Modulation Technique

The wireless and broadband are the hot topics in the field of communication, which have become the goal of telecommunication in future. Thus, Radio-Over-Fiber technique is studied in this paper. As an emerging broadband access network, ROF, taking the advantage of the fiber communication and wireless communication, makes Gb/s transmission possible and find many applications in high rate and broadband-mobile of wireless communication system. As the vibration source and emissive source in the ROF system, the millimeter-wave generator affects the performance of the system and plays an important role.In this paper, the technique of the millimeter-wave generator is analyzed and simulated. The main work of the thesis can be listed as follows:1. The background and basic concepts of the ROF system are introduced at first. Then, the baseband-over-Fiber, the IF-over-Fiber and the RF-over-Fiber transmission system are compared with each other. Also, their respective advantages and disadvantages are summarized. At last, the key techniques of ROF system are introduced.2. Various mainstream schemes for millimeter-wave generation in optical domain are analyzed, including direct modulation techniques, external modulation techniques, optical heterodyne techniques and up-conversion technology. The models of the technique are built from the basic principle step by step. Compared with themselves, the advantages and disadvantages are summed up, and the suggestion for development is proposed.3. A method of millimeter-wave based on feed forward modulation, involving its advantages and disadvantages, is analyzed in this paper, and a new improved one is put forward.4. A new way to realize the generation of millimeter-wave based feed forward modulation is proposed. According to the theoretical model, the signal equation containing the millimeter-wave frequency is deduced through theoretical analysis. In this scheme, two lasers with 70GHz frequency interval are served as sources. Then a frequency-quadrupling with feed forward modulation (FFM) technique is employed to generate two phase correlated sidebands. The desired millimeter-wave signal can be filtered by array grating from the sidebands. 5. By simulations, the influence of various parameters on millimeter-wave generation is listed. By adjusting the laser line-width of laser 1 and 2, time delay, optical fiber length and dispersion coefficient, the attenuation items of millimeter-wave power can be controlled and millimeter-wave with good quality can be obtained. Finaly, the traits of the system of millimeter-wave based on feed forward modulation are summarized, including its advantages and problems that should be paid attention to when building the real system.