| The microwave photonic filter has the same function as the traditional microwave filter which is select the required signal,eliminate or suppress the noise and interference signals in the system.However,the microwave filter cannot achieve the tunability,reconfiguration and high frequency selectivity of the filter system simply and conveniently due to its electronic bottleneck.Microwave photonic filters process the modulated light carrying RF signal by using various optical means to realize filtering in the optical field and then convert into the required electrical signal by the photoelectric detector.Microwave photonic filter can overcome the bottleneck of electronics because it processes the signal in the optical field,and also has the following advantages: anti-electromagnetic interference,tuning conveniently and the filter system reconfigurable.There are many ways to realize the single passband microwave photoni filter.This paper realizes the single passband microwave photonic filter by combining the phase modulator and the stimulated Brillouin scattering.The basic concept and principle of the single passband microwave photonic filter based on the stimulated Brillouin scattering are studied.Two kinds of single passband microwave photonic filters with high frequency selectivity are proposed.The main work of this paper is as follows:1.The research progress of microwave photonic filter is introduced,the basic theory of single passband microwave photonic filter based on stimulated Brillouin scattering is analyzed,and the key parameters of Brillouin such as Brillouin threshold,Brillouin frequency shift and Brillouin gain spectrum are measured.Then the tunability of the single passband microwave photonic filter is verified by experiments,and the stability of the filter is analyzed and improved.A tunable single passband microwave photonic filter with a tuning range of 20 GHz is obtained in the experiment,and the filter response fluctuation is less than ±3 d B.2.A high Q-value single passband microwave photonic filter based on fiber loop filter is proposed.A high frequency selective filter with a tunable range of 20 GHz is obtained through experiments,the 3 d B bandwidth of the passband is 3.6 MHz,and the sideband rejection ratio is more than 20 d B.3.A high Q-value single passband microwave photonic filter based on optical-electrical feedback loop is proposed.Through experiments,a high frequency selective filter with a tuning range of 17 GHz is obtained.The 3 d B bandwidth of the passband is 300 k Hz,the sideband rejection ratio is more than 20 d B and the amplitude fluctuation of passband is less than 2 d B. |
