| The generation and processing of microwave and millimeter signals plays an important role in the field of electronic warfare, radar, wireless communication and so on. When generating and processing of high frequency and large bandwidth signals, the capability of the electronic approaches is limited by the bandwidth of the electronic components and faces the electronic bottleneck. In contrast, the photonic approaches show the superior performance with large bandwidth, low weight, low loss and immunity to the electromagnetic interference, and have been widely used to realize the microwave photonic signal generation and processing.In this dissertation, we mainly study on several key technologies of microwave photonic signal generation and processing. Firstly, two structures of optoelectronic oscillator (OEO) to generate microwave signal with low phase noise and high frequency stability are proposed. Then, an approach to generating microwave chirped signals with large time-bandwidth product (TBWP) is proposed, and the mathematical model of the system and the performance analysis are also presented. Next, the mathematical model and the design criterion of the system which can generate microwave phase-coded signals are also presented, and the performance analysis is also investigated.In addition, an exact analysis model to characterize the wideband-processing photonic time stretch system (PTS) is presented, and the performance parameters of the system are comprehensively investigated. The major innovations and contributions are as follow1. An OEO by using a dual-transmission-peak phase-shifted fiber Bragg grating (PS-FBG) is proposed. In the structure, the optoelectronic cavity can realize high Q by using a PS-FBG with high finesse, and the frequency of the generated microwave signal is decided by the frequency spacing between the two transmission peaks of the PS-FBG Therefore, the need of long loop of fiber and narrowband electric filter is removed. The proposed structure has the advantage of low insertion loss, compact, photonic-integrated and low cost. In the experiment, an oscillation signal with center frequency of 10.6 GHz and phase noise of -99.3 dBc/Hz at 100 kHz frequency offset from the carrier is generated. In addition, to solve the frequency-shifting problem in the conventional OEO, an approach to realize frequency-locking is presented by utilizing an optical comb-filter. Compared with the additional feedback circuits to stabilize the frequency, this structure is simpler to implement.2. An approach to generating chirped microwave signals with high TBWP based on frequency-to-time mapping (FTTM) is proposed. By analyzing the mathematical model of the system, the performance of the maximum TBWP achieved in this system is demonstrated. The TBWP of the chirped microwave signals generated in the simulation and experiment results are as 368 and 61.2, respectively.3. A mathematical model to fully characterize the generation of phase-coded microwave signals based on FTTM is proposed, and the design criterion is also given. The maximum TBWP of the generated signal achieved in the system is also presented. Both simulation and experiment results prove the theory. The TBWP of the phase-coded signal in the simulation is 263.2. The theory can help to design the system effectively.4. An exact theoretical model of the PTS system to precisely characterize the harmonics and intermodulation products is presented. Based on this theoretical model, the design of the PTS system is simplified, and the performance parameters of the system can be evaluated, such as the harmonic power distribution, system bandwidth, 1 dB compression point, TBWP, third-order interception point, spurious-free dynamic range and so on. The theoretical results are proved by both simulation and experiment results. The spurious-free dynamic range of the system in the simulation and experiment are 119.16 dB-Hz2/3 and 88.9 dB-Hz2/3, respectively.
|
PDF Full Text Request