Research On Microwave Photonic Frequency Conversion Based On Carrier-suppression Signle-sideband Modulation

Microwave photonics,as a new interdiscipline subject combining microwave communication and optical fiber communication,is mainly used to study and solve the problem of mutual conversion between microwave signal and optical signal.With the rapid increasement of wireless communication band,the present low frequency band can not meet the demand of actual needs.Due to the broad bandwidth,low loss and anti-electromagnetic interference of the microwave photonic link,it has become a promising technique for radio over fiber?RoF?system,deep space detection,optical controlled phased array radar and other applications.Microwave photonic frequency conversion as a necessary part of the transmitter and receiver,can effectively break through the electronic difficulties of the raditional frequency conversion,and it has been extensively investigated for the past years.This paper mainly includes five parts.Firstly,the research background and the research status of microwave photonic frequency conversion technology is introduced.Next,the main performance parameters of the microwave photonic frequency conversion system are briefly described and the microwave photonic conversion model based on MZM,cascade MZM and DPMZM is theoretically analyzed.Then,three microwave photonic frequency conversion methods based on carrier-suppressed single sideband?CS-SSB?modulation are proposed respectively.The feasibility of the propose system is theoretically analyzed and the performance of the system is tested and verified by experiments.Finally,the summary and the outlook of this paper is given.The proposed microwave photonic frequency conversion methods is as follows:1.A microwave photonic mixer based on a dual-polarization quadrature phase shift keying?DP-QPSK?modulator is proposed.The radio frequency?RF?and local oscillator?LO?signals were loaded to the modulator via two 90°hybrid couplers,respectively.The CS-SSB modulation was achieved by adjusting the DC voltages of the modulator.A photodetector?PD?is applied to obtain the up-conversion or down-conversion signal by frequency beating.Experiments result shows that the output electrical spectrum is very pure in both up-conversion and down-conversion modes,and the frequency up-conversion and down-converison can be switched by changing DC bias.The suppression ratio of all undesired mixing spurs is high?³0dB?.Since the RF and LO signals respectively drive the DP-QPSK modulator through two electrical 90°hybrid couplers,the RF/LO isolation reaches 49.1 dB.The spurious free dynamic range?SFDR?of system reaches 103.5 dB·Hz^2/3.2.A microwave photonic up-converter with LO doubling is proposed based on CS-SSB modulation.The+1st-order LO sideband and the-1st-order intermediate frequency?IF?sideband with secondary modulaiton are generated by a Mach-Zehnder modulator?MZM?,fiber bragg grating?FBG?,a dual-parallel Mach-Zehnder modulator?DPMZM?and a electrical 90°hybrid coupler.The upconverted LO doubling up-conversion signal can be detected by a PD.It can been seen from the experiments result that the CS-SSB modulation is well achieved and the spurious suppression ratio reaches 17.3 dB.The electrical spectrum of the spur suppression ratios of the up-converter signal reaches 23.6 dB.The conversion efficiency is flat with a fluctuation of less than 1 dB over 10 GHz.The constellation diagram remains clear under 16 quadrature amplitude modulation?QAM?and 64 QAM modulation formats.The SFDR of the LO doubling up-conversion reaches 96.1 dB·Hz^2/3.3.A reconfigurable microwave photonic frequency up-converter with LO doubling or LO quadrupling is proposed based on CS-SSB modulation.The LO doubling and quadrupling up-conversion can be switched by tuning the DC biases of the first DPMZM.The experiments result shows that the spur suppression ratios of the up-converter with LO doubling and quadrupling are 21.3 dB and 11.3 dB,respectively.The error vector magnitude?EVM?is less than 6%under 16 QAM and 64 QAM in both LO doubling or LO quadrupling up-conversion.The SFDR of the LO doubling and LO quadrupling up-conversion reaches 96.0 dB·Hz^2/3 and 91.5 dB·Hz^2/3,respectively.