基于光载波抑制调制的星间微波光子下变频研究

Research on inter-satellite microwave photonic frequency down conversion based on optical carrier suppression modulation

针对卫星通信中微波信号光学处理问题,建立了星间微波光子下变频系统模型,采用两个双电极马赫-曾德尔调制器(DE-MZM)并联形式,以光载波抑制(DCS)方式实现了星间微波信号的光域放大、传输和下变频。利用贝塞尔函数展开分析了下变频系统中信号和各噪声分量,对射频本振信号功率进行了优化,仿真研究了调制器直流偏置漂移、移相器相移误差和发射光功率对系统性能的影响。结果表明,调制器直流偏置相位漂移小于5℃时输出载噪比(CNR)恶化小于0.05 dB,移相器相移误差小于5℃时输出CNR恶化小于0.02 dB,系统具有较高稳定性;当发射功率为10.48 dB时,输出CNR达31.33 dB,系统能够满足输出CNR要求。

To solve the problem of optical handling of microwave signal in satellite communication, the in- ter-satellite microwave photonic frequency down conversion system is modeled, two parallel dual-elec- trode Mach-Zehnder modulators based on optical carrier suppression modulation are utilized to modulate the uplink microwave signal received by satellite and the local oscillator signal produced in satellite, re- spectively,and the microwave signal is optically amplified,transmitted and frequency-down converted in the inter-satellite optical link. The output signal and noise of system are analyzed with Bessel expansion, the local oscillator signal power is optimized, and the effects of modulator bias phase drift, phase shifter error and emission optical power on the system performance are simulated. The results show that the de- terioration of output carrier to noise ratio （CNR） is under 0. 05 dB while the modulator bias phase drift is less than 5 ~C, the output CNR deterioration is under 0.02 dB while the phase shifter error is less than 5℃, and the frequency down conversion system has high stability. When the emission optical power is 10.48 dB,the system output CNR is 31.33 dB,which can meet the practical requirement. The inter-sat- ellite microwave photonic frequency down conversion system can be applied to the optical handling of mi- crowave signal in the future satellite optical communications.