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马赫-曾德尔调制器的非线性会严重恶化星上微波光子系统的性能。建立了包括光源、马赫-曾德尔调制器和光电探测器的双音调制理论模型,利用傅里叶级数展开、傅里叶变换和Gegenbauer加法定理,推导出了调制器非线性失真的严格通用解析解。根据该解析解,可精确地预计不同调制方式下星上微波光子系统的非线性失真,优化系统性能。分析结果表明,双边带和单边带调制条件下,将调制器输出信号保留至二次谐波能较好地近似计算三阶交调失真比和三阶交调截点,三阶交调失真比随调制系数的增大先增大后减小。当调制系数小于1.4674时,单边带调制三阶交调失真比至少比双边带调制小6dB,适合于星上微波光子系统的应用。
The Mach-Zehnder modulator nonlinearity can seriously deteriorate the performance of on-board microwave photonic systems. The theoretical model of dual-tone modulation including light source, Mach-Zehnder modulator and photodetector has been established. Using the Fourier series expansion, Fourier transform and Gegenbauer addition theorem, the strict generalization of modulator nonlinear distortion Analytic solution. According to the analytical solution, the nonlinear distortion of the microwave system can be accurately predicted under different modulation schemes, and the system performance can be optimized. The analysis results show that it is better to approximate the third-order intermodulation distortion ratio, the third-order intercept point and the third-order intermodulation distortion by keeping the modulator output signal to the second harmonic under the condition of double-sideband and single- Ratio increases with the modulation coefficient first increases and then decreases. When the modulation factor is less than 1.4674, the third-order intermodulation distortion of single-sideband modulation is at least 6dB less than that of double-sideband modulation and is suitable for the application of microwave photonic system on the satellite.