Research On Methods Of Microwave Photonic Frequency Mixing Based On Dual-Parallel Mach-zehnder Modulator

Microwave photonics,as a new interdiscipline,is mainly research on the interaction between the microwave optical signals.Owing to the inherent advantages,such as the broad bandwidth,low transmission loss and immunity to electromagnetic interference?EMI?,etc,microwave photonic system break through the bottleneck of electronics in conventional microwave system and it has huge development potential and wide application prospect in radio over fiber?RoF?system,optical controlled phased array radar and photonic generation of microwave and millimeter-wave,etc.In these applications,the frequency conversion of microwave signal are necessary to satisfy the frequency demand of the transmitter and receiver.Three methods of microwave photonic mixer are mainly studied in this paper.The research background and significance of microwave photonics and the research status of microwave photonic frequency mixing technology are firstly introduced.Next,the fundamental principles and characteristics of microwave photonic system are theoretically analyzed.Then,three methods of microwave photonic frequency mixing are proposed and the principles are mathematically analyzed.The corresponding experimental systems are built and the performances are tested.Finally,the conclusion of this paper and prospect of microwave photonic mixing technique are given.The main work in this paper is as fellow:1.An ultra-wideband microwave photonic frequency downconversion method is proposed.A dual-parallel Mach-Zehnder modulator?DPMZM?,an electrical 90°hybrid coupler and an optical bandpass filter?OBPF?are combined to realize carrier-suppressed single-sideband?CS-SSB?modulation of the ultra-wideband radio frequency?RF?and local oscillator?LO?signals from 2 to 40 GHz.The RF signal with sub-octave or multioctave bandwidth can be downconverted to intermediate frequency?IF?signal by using a LO signal with the corresponding frequency at photodetector?PD?.The operation principle of the proposed method is mathematically analyzed and the corresponding experimental system is built and tested.The output IF signal of system is pure enough with the spur suppression ratio of 40 dB.The second-order and third-order spurious free dynamic range?SFDR?of system are 71.0 dB-Hz^1/2 and 102.2 dB-Hz^2/3,respectively.2.A phase tunable microwave photonic frequency downconversion method is presented.The phase shifted RF and LO optical single-sideband signals are generated by using a DPMZM and an OBPF.The IF signal with phase shift is obtained by frequency beat at PD.The operation principle of the proposed method is theoretically analyzed and the corresponding experimental system is built and tested.It is demonstrated that the RF signal can be downconverted and its phase can be shifted simultaneously.The full range 360°phase shift with good stability can be easily achieved by adjusting a bias voltage of DPMZM.The conversion efficiency and SFDR of system are-33 dB and 100.2 dB-Hz^2/3,respectively.3.A microwave photonic mixer using frequency-doubled LO signal is reported.The+2nd-order LO sideband and-1st-order RF sideband are produced based on a dual-polarization DPMZM?DP-DPMZM?,an electrical 90°hybrid coupler and an OBPF.The corresponding upconverted IF signal is obtained after PD.The-1st-order RF sideband can be easily switched to+1st-order RF sideband by adjusting a bias voltage of DP-DPMZM to obtain downconverted IF signal.The operation principle of the proposed method is theoretically analyzed and the corresponding experimental system is built and tested.The up and down conversion efficiencies of system are-42.7 dB and-37.0 dB,respectively.The SFDR of the system is 96.5 dB-Hz^2/3.