多载波输入时星间微波光子链路性能分析

Performance Analysis of Inter-satellite Microwave Photonic Link under Multiple Carriers Input

针对卫星通信中射频载波信号光学传输问题,建立了星间微波光子链路,利用两个并联双电极马赫-曾德尔电光调制器,以光载波抑制调制方式实现了星间微波信号的光域传输和下变频。利用贝赛尔函数展开推导了多载波输入情况下接收信号任意谐波和交调分量表达式,得到了输出信号噪声失真比与输入载波数关系,利用曲面投影法求得了不同载波数时电光调制器最佳调制系数,分析了载波数对最佳调制系数、光发射功率和最优信号噪声失真比的影响。结果表明,射频本振调制器的最佳调制系数在载波数变化时可以保持不变,射频信号调制器的最佳调制系数和最优信号噪声失真比随载波数增大而减小,光发射功率随载波数增大而增大。

To solve the optical handling of microwave signal problem in satellite communication, the inter-satellite microwave photonic link is presented. Two parallel dual-electrode Mach-Zetmder modulators are utilized to achieve the inter-satellite optical transmission and frequency down conversion of microwave signals based on optical carrier suppression modulation. The solution for any harmonic and intermodulation components of receiver signal is derived with Bessel expansion, and the relationship formula between carrier number and output signal to noise and distortion ratio （SNDR） is deduced. The optimum modulation indexes are obtained with curved surface projection method. The effects of carrier number to optimum modulation indexes, optical emission power and SNDR are analyzed. The results show that, the optimum modulation index of modulator with local oscillator can remain unchanged while the carrier number changes. When the carrier number increases, the optimum modulation index of modulator with signals and optimal SNDR both decrease and the optical emission power will increase.