Research On Microwave Photonic Direction Finding Technology

The radio direction finding technology can provide the direction or location of the enemy radiation source,which can help for the next step to interfere with or even destroy the enemy radiation source.It is an indispensable key module in the electronic reconnaissance and countermeasure system.Modern electronic systems are developing towards high operating frequency,large bandwidth,and high dynamic range.At present,the electronic direction finding technology has low working frequency band,poor frequency tuning capability,narrow bandwidth,and is susceptible to electromagnetic interference.Due to the limitation of these“electronic bottlenecks”,it will not be able to meet the development needs of future electronic reconnaissance systems.The microwave photonic direction finding technology realizes the microwave direction finding in the optical domain.It has the significant advantages of high and tunable working frequency,large instantaneous bandwidth and no electromagnetic interference.It can work in conjunction with the photonic assisted microwave signals generation,transmission and processing systems.In this thesis,the main research on the microwave photonic direction finding technology is carried out,and the main work are described as follows:?1?The basic models and key components of microwave photonic links are introduced,such as lasers,electro-optic modulators,and photodetectors.Mathematical derivation and analysis of the periodic power decay caused by Mach-Zehnder electro-optic modulators?MZM?and fiber dispersion are carried out.The fiber dispersion effect is modeled and simulated by the VPI software,and the influencing factors are analyzed.The SSB modulation method to overcome the periodic fading is given.?2?The microwave photonic direction finding technology based on phase interferometer is studied,mainly using microwave photonic phase measurement technology to replace the phase measurement technology in traditional electronic domain.And a microwave photonic phase measurement based on dual polarization modulator?DPol-MZM?is proposed.A detailed theoretical derivation of the proposed method is studied,and a simulation is executed by the VPI software.The simulation results show that the phase difference is in the range of±180°,the phase error can be within±3°.Combined with the long baseline,and the multi-baseline deblurring technique,it is expected that the accuracy of the direction-finding can be controlled within 1°.?3?The microwave photonic direction finding technology based on phased array antenna is studied.The main method is to use microwave photonic phase shifter instead of traditional phase shifter in the electric domain.Combined with antenna beam scanning and direction finding principle,microwave photonic direction finding is implemented.A microwave photonic phase shifter based on DPol-MZM is proposed.Detailed theoretical analysis and experimental verification of the scheme are carried out.The experimental results show that the phase shift can be continuously tuned from-180°to 180°over the frequency range of10-33 GHz,and the magnitude variation is less than±3 dB.?4?Two microwave photonic link performance improvement schemes are proposed and experimentally demonstrated.One is a microwave photonic link with tunable carrier to sideband ratio?CSR?and balance detection.The experimental results show that the tunable CSR can be used to optimize the link gain and NF of the proposed link,balance detection can be used to improve the link gain,NF,SFDR₃,and especial SFDR₂.Experiments to demonstrate the frequency tunability of the proposed link are also carried out.The second is a single sideband?SSB?modulated microwave photonic link with tunable CSR.The SSB modulation is use to overcome the period power fading induced by fiber dispersion when fiber is used to realize the long-distance transmission.The tunable CSR can be used to optimize the link gain.The tunability of the CSR and the frequency tuning of the optical SSB modulation are showed in the experiment,which are consistent with the theoretical analysis.