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以无线光通信中的副载波调制技术为背景,研究了光强调制正交相移键控信号的循环自相关和循环谱密度函数,并对实际测得的信号的循环谱和循环自相关函数进行了分析。结果表明,无线光副载波信号经过大气传输,同时受到了加性白噪声和乘性窄带随机噪声的影响,有限强度的大气湍流并未破坏正交相移键控信号的循环平稳特性。影响接收信噪比的主要因素是有用信号功率与低频噪声功率之差,通过加时间窗的方法可以有效抑制低频噪声的影响,从而提高系统接收信噪比。
Taking the subcarrier modulation technology in wireless optical communication as the background, the cyclic autocorrelation and cyclic spectral density functions of the light intensity modulated quadrature phase shift keying signal are studied. The cyclic spectrum and cyclic autocorrelation function Analyzed. The results show that the wireless optical subcarrier signals propagate through the atmosphere and are affected by additive white noise and multiplicative narrow band random noise. The limited intensity atmospheric turbulence does not destroy the cyclostationarity of quadrature phase shift keying signals. The main factor that influences the received signal-to-noise ratio is the difference between the useful signal power and the low-frequency noise power. By adding a time window, the influence of low-frequency noise can be effectively suppressed, thereby improving the system reception SNR.