Research On The Incoherent Band Pass Microwave Photonic Filter

With the development of the information technology,microwave photonics has been defined as the study in microwave or photonic system.The microwave photonic filter is a kind of important devices in the field of microwave photonics,which has many advantages such as low loss,high bandwidth and immunity to electromagnetic interference and it can overcome the electronic bottleneck.Due to these advantages,it can be widely used in modern radar system and radio-over-fiber system.Microwave photonic filters have been extensively pursued during the past few years.Incoherent band-pass microwave photonic filter was studied in this thesis.Firstly,we introduced the research background and working principle of the microwave photonic filter.We mainly analyzed the microwave photonic filters based on time delay and phase modulation to intensity modulation conversion.The microwave photonic filters based on time delay usually have the periodic frequency responses.We analyzed the microwave photonic filter based on mach-zehnder structure,and got the response through simulation.This filter has a low-pass and periodic frequency response,we eliminated those shortcomings through phase modulator single-mode fiber.We got a single pass-band microwave photonic filter which can be adjusted from 8.3GHz to 25 GHz.Then,the microwave photonic filter based on stimulated Brillouin scattering was introduced.It has no any responses when we detect the phase modulated single directly.Stimulated Brillouin scattering can break the balance of the sidebands and realize the band-pass response.We built the microwave photonic filter whose tunable range is 21.7GHz based on phase modulator and stimulated Brillouin scattering,then studied the influence of temperature on the microwave photonic filter.We got the conclusion that the center frequency of the filter changed about 1.03 MHz when the temperature increased one degree,while the pass-band width and out-of-band-rejection of the filter kept the same.We analyzed the microwave photonic filter with multiple pumps based on the study of microwave photonic filter based on stimulated Brillouin scattering.We produced multiple pumps with two intensity modulator s,and realized double pass-band microwave photonic filter whose each pass-band can be adjusted independently.When the frequency difference of the two intensity modulators is equal to two times of Bril ouin frequency shift,we can achieve a widely tunable microwave photonic filter.