Research On Microwave Photonic Frequency Mixing Using Dual-Parallel Mach-Zehnder Modulator

Traditional frequency mixing technology has the shortcomings of limitations on bandwidth and susceptibility to electromagnetic interference,which can not comply with the trend of higher frequencies of wireless communication.Considering microwave photonic technology has the advantages of big bandwidth,high communication capacity,good security and low loss,it has attracted much attention in recent years.The introduction of microwave photonic technology into frequency mixing system can overcome the bottleneck in traditional mixing technology,and can achieve higher isolution and better electromagnetic interference immunity.Moreover,with the increasing number of applications and requirements of high performance,multi-functional and high-performance microwave potonics system has become a research hotspot.In this paper,by introducing frequency-doubling technology and chromatic dispersion compensation technology to the microwave photonic frequency mixing system,the proposed method can compensate for the periodic decline of output signal caused by chromatic dispersion in the long-distance transmission link while reducing the frequency of local oscillator and lowering hardware requirements.This scheme based on dual-parallel Mach-Zehnder modulators,realize above mentioned functions by adjusting the bias voltage of the modulators to introduce phase shift between the local oscillator sidebands and radiofrequency sidebands.The traditional scheme and proposed scheme are analyzed and compared,supplemented by formula deduction.The effectiveness and reliability of proposed scheme is verified by comparison simulations and experiments.The experimental results show that:First,at the maximum point of power fading,the system gain of the proposed scheme is improved by more than 40 dB compared with the traditional scheme,and the spurious-free dynamic range is increased by more than 20dB.Second,when the transmission distance is within 80 km,a certain local oscillator signal and radiofrequency signal remain unchanged,with the increase of transmission distance,the compensation effect also increases.In this paper,the microwave photonic integrated radiofrequency transceiver front-end system is also studied.By analyzing the performance of traditional schemes and investigating the requirements of integrated transceiver system inmodern applications,this paper proposes a scheme by substituting dual parallel Mach-Zehnder modulators for the Mach Zehnder modulators and phase modulators in traditional scheme.The reliability of the system is verified by simulating experiments.The simulation results show that the isolution and stray suppression of the system both exceed 40dB.