| Microwave photonic signal generation is a popular area of research in microwave photonics.Photogenerated microwave signals can be used for a wide range of applications.It can be used in satellite remote sensing,radar system,electronic countermeasures for military,instrument testing,transportation,clinical medicine and other aspects for civil.Compared with the traditional electronics function waveform generation method,microwave photonic signal generation technology can effectively solve the bandwidth,loss and electromagnetic interference and other "electronic bottleneck" problems,and with the natural compatibility of optical fiber system.Therefore,with the increasing maturity of optoelectronic fusion technology,it is of great importance to study the optical generation of functional waveform signals.The main research work of this paper is as follows:(1)Listed some of the domestic and foreign microwave photonics to generate function waveform methods.The methods are summarized and analyzed for the problems of relatively fixed modulation characteristics,inflexible system parameter settings,complex generation equipment,and for signal repetition rates generally limited by the RF modulation frequency.(2)The concept of symmetry coefficient was introduced to integrate triangular and sawtooth function waveforms into one expression,making the calculation and derivation of the target waveform simpler and more uniform;the fitting error formula was introduced to discuss the trend of fitting error with the approximation order N of the Fourier series,and the scheme was determined for the first three orders(N=3)of approximation,with a lower symmetry coefficient between 20%～80% while ensuring a relatively simple system fitting error(η<6%).(3)A quadruple frequency tunable symmetric triangular function waveform optical generation method based on a dual parallel Mach-Zehnder modulator is proposed,deriving the signal characterization of the output optical waveform and the mutual constraints of the system characteristic parameters(modulation coefficient β and time delay τ),establishing a simulation model to verify the structural and theoretical correctness,without using redundant optical filter pieces and with simple equipment,achieving a 5GHz RF driven The stable output of the 20 GHz function waveform with a low fitting error(η<8%)in the range of 20%～80% of the waveform symmetry factor is achieved,and the effect of micro-winding of the bias voltage on the output waveform accuracy is analyzed.(4)A tunable symmetric triangular function waveform optical generation method based on a dual parallel Mach-Zehnder modulator is analyzed,and the signal characterization of the output optical waveform is derived,and the inter constraint relationship of the system characteristic parameters(RF phase shift Φ,modulation coefficient m and bias phase shift φ)is analyzed.The modulation characteristics are flexible and the system parameter settings can be varied within a certain range,which greatly improves the flexibility of waveform generation.The simulation model is built to realize the stable output of 3GHz triangular function waveform driven by 3GHz RF,and the fitting error is used as the basis for evaluation,then the waveform symmetry coefficient between 20%～80% has a low fitting error(η<6%).When the experimental model is built and driven by 2GHz RF signal,the 2GHz triangular function waveform with adjustable symmetry coefficient can be obtained in the optical domain. |
