Research On Microwave Photon Phase Shifter Based On Electro-Optic External Modulation

Microwave photonics technology based on the combination of microwave millimeter wave technology and photonics technology is expected to be used in the fields of phased array radar,satellite communications,signal processing and phase encoding technology.The phase shifter plays an important role in the field of phased array radar and signal processing.Based on microwave photonics technology,this paper proposes a microwave photonic phase shifter based on Mach-Zehnder modulator(MZM)and a microwave photon frequency conversion phase shifter based on DP-DPMZM,this paper consists of the following four parts:1.A photonic microwave phase shifter capable of 360°phase shift based on Mach-Zehnder modulator(MZM)and Faraday rotating mirror(RFM)is proposed.The MZM,FBG and FRM generate orthogonally polarized optical carrier and+1 order sideband,a polarization modulator(PolM)is used to introduce phase shifts between two optical signals,and the phase shift of the microwave signal has a linear relationship with the DC drive voltage of the PolM.The power of the generated microwave signal remains constant during the phase shift;the simulation results show that the phase shift can be tuned from 0°to 360°with only one DC bias voltage,and the operating bandwidth is 4 to 43 GHz.2.A 360°microwave photonic phase shifter based on dual parallel Mach-Zehnder modulator(DPMZM)and phase modulator(PM)is proposed.The carrier-suppressed single sideband(CS-SSB)optical signal is generated by DPMZM;the bias voltage of the PM to introduce any linear phase shift to the carrier signal.The phase-shifted optical carrier and the CS-SSB sideband detected by a photodiode(PD).The phase shift of the generated microwave signal is linearly related to the DC bias voltage of the PM,and the amplitude of the microwave signal remains constant during the entire phase shift of the microwave signal,which increases the stability of the system.The simulation results show that the microwave signal in this scheme can achieve a phase shift of 0-360°,and the phase shift has a linear relationship with the DC bias voltage,and the power variation is within ±0.5dBm.3.A microwave photonic frequency-tunable phaser based on cascaded dual parallel Mach-Zehnder modulator(DPMZM)and phase modulator(PM)is proposed.The RF signal and LO signal drive DPMZM1 and DPMZM2 to achieve RF signal down/up-conversion;PM is used to introduce an arbitrary linear phase shift into optical carrier;The phase-shifted optical carrier and RF down/up-conversion signal detected by a photodiode(PD).This scheme only needs to change one DC voltage of DPMZM2 to realize up-conversion to down-conversion,and the phase of the frequency-conversion phase shift signal will not be affected.Simulation results show that the phase shift range of this scheme exceeds 360°,and the DC voltage is linearly related to the phase shift;the power of the up/down conversion signal remains constant.4.We propose and numerically simulate a microwave photonic phase-tunable frequency converter(MPPTFC)without optically filtering to realize both frequency up-and down-conversion and a full 360°phase-shift for the microwave signal based on a DP-DPMZM.In the proposed scheme,both microwave RF signal and frequency-tunable local oscillator(LO)are modulated on the lightwave by single-sideband carrier suppression(SSB-CS)modulation to generate optical orthogonally polarized optical tones carrying RF signal with up-or down-converted frequency.A PolM that can support lightwave modulation with opposite modulation indices in transverse electric(TE)and transverse magnetic(TM)modes is used to introduce a phase difference between the two modes.Then the orthogonally polarized optical tones are aligned into a single polarized state by a polarizer(Pol)and detected by a photodiode(PD),a frequency-converted and phase-shifted microwave signal can be obtained.Simulation results demonstrate that the proposed MPPTFC can up-/down-convert the microwave signal with a tunable frequency shift of LO frequency and realize a 360°continuously tunable phase shift via the DC bias voltage of the PolM simultaneously.