This paper makes a detail discussion about some questions of discrete window. It has been found that the sample value of boundary points of discrete window are important to the frequency-domain behavior of window function and the correct results have been given when calculating the window sequence by sampling the continuous window. On this basis, a novel revised lords window which makes an improvement in both sidelobe amplitude and decaying rate has been presented. We also call attention to the common error in the calculation of time series of Chebyshev window by FFT algorithm and point out the correct formula. This paper also makes an analysis about the errors of FIR digital filter designed by window method. Finally, as an application, the method of denim digital interpolator by window has been presented. in appendix A-I, we provide some examples of FIR low pass filters designed by window method and its FORTRAN program.
修改评论