基于修正快速傅里叶变换算法的仪表着陆系统信号干扰抑制与定量分析

Interference suppression and quantitative analysis of instrument landing system signal based on modified fast Fourier transformation algorithm

针对日益繁忙的机场空域和周边建筑对仪表着陆系统信号干扰的增加,以及传统模拟处理技术缺陷,提出一种基于修正快速傅里叶变换(FFT)频谱校正和最小均方差(LMS)算法自适应滤波器结合实现仪表着陆系统(ILS)信号鉴频分离的技术方案。该方案应用LMS自适应滤波器对ILS信号干扰进行抑制,完成滤波器的权值系数设定,并通过修正FFT技术在时域与频域内对ILS信号进行频谱分离与提取,修正其频谱幅值,以消除由于采样引起的频谱泄露和栅栏效应对信号的影响,使得提取信号逼近理想情况,提高调制度差(DDM)识别精度。针对ILS信号的干扰抑制与频域分离进行了仿真验证,结果表明所提出的信号处理系统技术方案能够有效地对干扰进行抑制,完成信号频域识别,为飞机着陆进近阶段提供准确可靠的导航信息。

For the problem of the increasing busy airport airspace and the surrounding buildings attaching disturbance to the Instrument Landing System （ILS） signal, and the defects of traditional analogue signal processing technology, a new method was given to realize the ILS signal frequency separation based on the modified Fast Fourier Transformation （FVI＇） spectrmn correction and Least Mean Square （LMS） adaptive filter. The LMS adaptive fiher was used to suppress ILS signal interference, with setting optimal weight filter coefficient. And the ILS signal spectrum was separated and extracted based on the modified FFT technique in time domain and frequency domain. The spectrum amplitude was corrected in order to eliminate the impact of the spectral leakage and picket fence effect caused by signal sample for improving the recognition accuracy of Difference in the Depth of Modulation （ DDM）. The simulation was carried out to verify the effect of interference suppression and frequency separation to the ILS signal. The results reveal that the proposed technical scheme of signal processing system can effectively suppress the interference and complete frequency domain identification, which can provide reliable and accurate navigation information in the aircraft landing approach.