Research On Microwave Photonic Mixing And Phase Shifting Technology Based On Parallel Modulator

The frequency mixing technology based on microwave photonics can up-mix or down-mix the radio frequency signal so that the receiving device can receive and improve the system communication capacity.Meanwhile,the phase shifter realized by microwave photonic phase-shifting technology is the core structure of phased array radar,which has the advantages of low loss,strong anti-crosstalk,wide bandwidth and simple operation.In the past 20 years,many microwave photonic frequency mixing and phase-shifting schemes have been proposed,but the achievable functions are single,which cannot meet the requirements of future multi-functional frequency mixing and phase-shifting systems,such as: sub-harmonic mixing that can reduce the frequency requirements of the local oscillator signal and the bandwidth of the modulator,double-balanced mixing that can suppress spurs and increase output power,I/Q mixing that can be applied to transmit and receive equipment,and image rejection mixing.In order to solve the above problems,this thesis intends to study the microwave photonic frequency mixing and phase shifting technology based on parallel modulators.The detailed research contents are as follows:(1)Firstly,the research background of microwave photonics is introduced,the research significance and development status of microwave photonic mixing and phase shifting technology are summarized,and the existing realization methods of microwave photonic mixing and phase shifting are summarized in this thesis.Then,the structure and working principle of the optical external modulator required for the follow-up research are analyzed,and the commonly used optical sideband modulation methods and performances are summarized in this thesis.Finally,the model of the mixing phase-shifting system is summarized.(2)In order to expand the function of the system and reduce the frequency requirements of the local oscillator signal,this thesis proposes a sub-harmonic mixing scheme based on parallel double parallel Mach-Zehnder modulators,which outputs the up/down mixing phase-shifted microwave signal,whose phase can be changed from-180° continuously increases to +180°.The scheme utilizes the second-order sideband mixing of the local oscillator signal,which reduces spurious interference and frequency requirements for the local oscillator signal,increases the phase-shifting function,and improves the isolation,electromagnetic resistance and frequency mixing performance of the system.However,the mixing range of the system is limited by the filter bandwidth,and it cannot be extended to multiple channels for independent phase shifting,so the system application scenarios are limited.(3)In order to meet the requirements of large-bandwidth microwave photonic mixing systems and improve the system mixing range and overall performance,this thesis proposes a high-order harmonic mixing and phase shifting scheme based on dual parallel Mach-Zehnder modulators and parallel Mach-Zehnder modulators.In this scheme,the even-order sidebands of the local oscillator signal are beat frequency of the first-order sidebands of the radio frequency signal in turn,so the microwave signal with a wide range of adjustable frequency can be output,whose phase can not only continuously increase from-180° to +180°,but also related to the analyzer.When applied to multiple channels,this scheme can simultaneously up/down mix and change the phase of each channel independently.Theoretical analysis and simulation results show that this scheme greatly reduces the bandwidth requirements of the local oscillator signal generator and modulator,so the output microwave signal has a larger frequency adjustable range,lower power jitter,and higher phase shift Flatness and strong spurious immunity.Meanwhile,the scheme provides theoretical support for the realization of multi-functional mixing and phase-shifting by reconstruction in Chapter4.(4)In order to meet the multi-functional development of the mixing phase-shifting system in the future and expand the application scenarios of the system,this thesis proposes I/Q mixing,double-balanced mixing,image-reject mixing,and multi-channel multi-band mixing and phase-shifting schemes with higher performance by reconstructing the structure of the above-mentioned high-order harmonic mixing.The scheme improves the flexibility,anti-spur capability and application scenarios of the system.Theoretical analysis and simulation results show that the performance of I/Q mixing and double-balanced mixing has been greatly improved,the image signal is greatly suppressed,and the multi-band mixing microwave signal power and phase shift amplitude are highly flat.The scheme expands the system functions,which has high feasibility and flexibility,and it can be applied to systems such as radar,satellite communication,electronic countermeasures and broadband microwave measurement.