Studies On Microwave Photonics Phase Shift And Image Rejectioh Mixing Technology

Microwave photonics mixing technology uses photonic methods to perform frequency conversion processing on signal,the microwave photonics system has a small size,light weight,and outstanding anti-electromagnetic interference capability.It opens up a new solution to solve the "electronic bottleneck" problem of traditional electrical devices.Considering that current communication system requires the receive/transmit module to be a multi-functional mixer,and at the same time,it is required to reduce the frequency of the microwave local oscillator source.The paper focuses on the implementation of frequency conversion signal phase controllble and image rejection while the microwave photonics mixer completes sub-harmonic frequency conversion.The main research work in this paper is as follows:(1)A phase controllable sub-harmonic mixer scheme is proposed,which can achieve linear and continuous tuning of the phase while completing frequency up/down conversion of microwave signal.The two signal modulations in the scheme both suppress the carrier component,which improves the conversion efficiency of the mixer;and the modulation process is separated from the single control element that realizes phase tuning,making the system easy to use in phased array beamforming.The results show that the mixer realized by the scheme has good stability,the output frequency conversion signal has high purity,the maximum power ripple is 0.37 dB,and the phase deviation remains below 1.03°.(2)A sub-harmonic downconverter scheme with image rejection capability is proposed.Its system is designed based on microwave photonics phase shift technology,the parallel two-channel modulation process of traditional I/Q mixing isrealized in an integrated electro-optical modulator,which can maintain a 90° phase difference between the two downconverted signals in 20~30GHz,so as to realize image rejection.The results show that the quadrature phase deviation is less than1.54° and the average image rejection ratio is more than 45 dB.However,the system bandwidth is limited by the filtering characteristics of the wavelength division multiplexer,so wideband frequency tuning of the system is difficult to achieve.(3)All-optical,broadband sub-harmonic image-reject downconverter scheme is proposed.In response to the problems in the previous solution,a new electro-optical modulator is used to convert the modulation information to the orthogonal polarization state of the optical field to achieve polarization multiplexing to avoid the use of the wavelength division multiplexer.The results show that the quadrature phase deviation of the two downconverted signals within 10~40GHz is less than0.86°,and the average image rejection ratio exceeds 45 dB.In addition to the advantages of the previous scheme,it truly realizes all-optical ? broadband image rejection frequency down conversion of microwave signal.