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建立了包括光源、马赫曾德尔调制器、掺铒光纤放大器和光电探测器的双音调制星间微波光子链路模型。利用贝塞尔函数展开、傅里叶变换/反变换和Graf加法定理,推导出探测器输出信号的严格通用解析解,考虑三阶交调失真的影响,得出信号噪声失真比(SNDR)的表达式。着重分析了在不同调制方式下SNDR、基波和三阶交调信号功率随射频输入功率的变化情况。数值计算结果表明:SNDR、基波和三阶交调信号功率随射频输入功率的增大先增大后减小,存在最优的射频输入信号功率使SNDR达到最大。相同射频输入功率条件下,双边带调制SNDR大于单边带调制,适合星间微波光子链路应用。
A dual-tone interstellar microwave photonic link model including a light source, a Mach-Zehnder modulator, an erbium-doped fiber amplifier, and a photodetector is established. Using the Bessel function expansion, Fourier transform / inverse transform and Graf addition theorem, a rigorous general analytical solution of the detector output signal is derived. Taking into account the influence of third-order intermodulation distortion, the signal noise distortion ratio (SNDR) expression. The changes of power of SNDR, fundamental wave and third-order inter-modulation signal with RF input power under different modulation modes are emphatically analyzed. The numerical results show that the power of SNDR, fundamental wave and third-order intermodulation signal firstly increases and then decreases with the increase of RF input power, and the optimal RF input signal power has the maximum SNDR. The same RF input power conditions, double-sideband modulation SNDR greater than single-sideband modulation, suitable for inter-satellite microwave photonic link applications.