Research On Microwave Photonic Phase Shift And Image Rejection Mixer Based On Electro-Optic Modulation

Microwave photonics is a new subject produced by the combination of microwave technology and photonic technology.Its system has the advantages of strong immunity to electromagnetic interference ability,large bandwidth,low transmission loss and small volume.It has important applications in many fields.This paper mainly studies the microwave photonic mixer based on electro-optic external modulation to achieve phase shift and image suppression.The main research work is as follows:(1)A microwave photonic mixer based on cascaded polarization division multiplexing dual-parallel Mach-Zehnder modulator(PDM-DPMZM)and dualparallel Mach-Zehnder modulator(DPMZM)is proposed,and the up and down conversion systems are switched by adjusting the bias voltage.The results show that the scheme achieves full 360° phase shift,and the spurious suppression ratio of up and down conversion systems is 24.26 d B and 24.54 d B respectively.In order to reduce the demand of the system for the local oscillator,a reconfigurable microwave photonic mixer with local oscillator frequency doubling is proposed.The scheme uses the second-order sideband of the local oscillator to beat and changes the detection mode of the signal to realize single-ended,double-balanced,I/Q and image-reject mixer.(2)In order to avoid the interference of image signal in down conversion system,a microwave photonic image rejection mixer(IRM)based on a dual-polarization quadrature phase shift keying modulator(DP-QPSK)is proposed.In the scheme,two channels are produced by a polarization controller(PC)and a polarization beam splitter(PBS).The phase of two down conversion signals generated by the two channels are kept orthogonal by using the microwave photonic phase-shifting technology.After passing through an intermedia frequency quadrature coupler,the image suppression function is realized.The results show that the image rejection ratio is 45.57 d B in the range of 10-40 GHz,and the quadrature phase deviation and power ripple are less than1.7° and 0.19 d B respectively.(3)In order to solve the problems of DC offset and even harmonic distortion in IRM,an IRM system based on cascaded DP-QPSK and DPMZM is proposed.The scheme uses balanced photodetector(BPD)to beat,which can eliminate DC offset and even harmonic distortion.The signal is modulated by cascaded modulators to avoid the use of filter,so as to optimize the performance of the system.The results show that the maximum image rejection ratio is 54.4d B in the frequency range of 10-40 GHz,and the quadrature phase deviation and power ripple are less than 1.5° and 0.17 d B respectively.