Reconfigurable Microwave Photonic Filter Based On Carrier Cancellation

Microwave photonic filter is defined as a microwave frequency-selecting and filtering device which can process microwave signal in optical domain.While the advantages of microwave technique and photonic technique are remained,the features of high speed,wide bandwidth,anti-electromagnetic interference,tunability and reconfigurability are also achieved in microwave photonic filter which has attracted wide spread attention.Based on the basic principle,microwave photonic filters are divided into two kinds which based on delay-line and carrier cancellation respectively.More filtering bands are possessed in the microwave photonic filters which based on delay-line.But as the periodicity between all bands exists,single band is difficult to tune.The filtering bands can be reduced in the microwave photonic filters which based on carrier cancellation.But single band is tuned easily and it is adapted to the demand of multi-service transmission.Due to the uncertainty of the clutters in complicated environment,different filtering demand should be satisfied with a single microwave photonic filter,which the demand of reconfigurability is increased.In this thesis,a high-speed switchable microwave photonic filter between low-pass and band-pass and a reconfigurable multi-stopband microwave photonic filter are designed,numerically simulated and experimentally demonstrated.(1)A high-speed switchable microwave photonic filter between low-pass and band-pass is designed.Frequency-hopping radio-frequency signal is adapted as the driving signal of Mach-Zehnder modulator,switcfhable spectral response which controlled by radio-frequency signal is implemented based on the frequency-selecting by single tunable optical filter.As the numerical simulation results show,microwave photonic filter with 2 ns switching speed between low-pass and band-pass is realized.The center frequency of passband is equal to the half value of the bandwidth which the tunable optical filter possessed.The bandwidth of passband is determined by the frequency of radio-frequency signal which is used to drive Mach-Zehnder modulator and can be tuned in 2?20 GHz.The high-speed switchable spectral response is implemented by tuning the frequency of radio-frequency signal with the advantages of simple structure.(2)A reconfigurable multi-stopband microwave photonic filter are designed.Programmable multi-tone radio-frequency signal is adapted as the driving signal of Mach-Zehnder modulator,variable multi-tone pump signal is generated.Based on stimulated Brillouin scattering,multi-frequency optical sideband processing is realized and reconfigurable spectral response with multiple stopbands is obtained.As the numerical simulation and experiment results show,microwave photonic filter with 1?4 stopbands is realized which the center frequencies of all stopbands tuned in 2?8 GHz independently and the maximum out-of-band rejection reaches 49 dB.The spectral response is controlled by radio-frequency signal with the advantages of convenient tuning,simple and controllability.