用窗函数法设计FIR滤波器的AtiveX控件，里面包含了基2的FFT,IFFT函数，窗函数可选，返回滤波器系数，并且画出所设计的滤波器的频谱图。-AtiveX control uing window function method to design FIR filter,in which there are also the FFT function.The ctrol returns the conficient of the filter and draws the spectrum of