湍流折射率谱型对大气闪烁和相位起伏功率谱的影响

Influence of different refractive index spectrums on scintillation and phase fluctuation power spectrum of light wave propagation in atmosphere

基于Taylor湍流冻结假设理论,在不同湍流折射率谱型条件下,推导得出了光波闪烁和相位起伏频谱的表达式;数值计算了湍流谱型中折射率标度指数、内尺度以及外尺度变化时对光波频谱的影响。结果表明:随着折射率起伏标度指数的增大,闪烁频谱的低频段不再仅为常数,高频段下降的幂率逐渐增大,同时相位频谱在整个起伏频率段下降的幂率越来越大;湍流内尺度的增加将引起光波频谱的高频段下降的幂率越来越大;而随外尺度的减小,闪烁频谱低频段的振幅减小,这种影响在大口径接收时较为明显,相位谱的低频段幂率减小。

Based on Taylor＇s frozen turbulence hypothesis, analytical expressions of scintillation and phase fluctuation pow- er spectrum of the light wave propagation in atmosphere with different refractive index spectrum of turbulence were deduced. The influence of turbulent refractive index scaling exponent, inner scale together with outer scale on light wave power spectrum was discussed. Analytic results were summarized as follows. Firstly, with the increase of turbulent refractive index scaling exponent, the low-frequency spectrum of atmospheric scintillation isn＇t only a constant, the high-frequency spectrum obeys the power law with an increasing exponent, and the slope of phase fluctuation power spectrum is increasing in the whole frequency range. Sec- ondly, the bigger the turbulent inner scale is, the faster the high-frequency spectrum of scintillation and phase spectrum fall with frequency. Finally, when the turbulent outer scale decreases, the amplitude of scintillation spectrum at low frequency range de- creases especially with a lager aperture, the slope of low-frequency of phase fluctuation spectrum also decreases.