This paper describes a novel and simple design technique for windows in the form of a weighted sum of cosine terms. First, it is made clear that not only does there not exist a basic difference between the Blackman-Harris windows and the Z-window proposed by Zhong and colleagues, there is just a difference in mathematical expression, because the coefficients of both window families can be interconverted easily. Next, by focusing on the limitation of the duration time which is the essential property of windows, a novel and simple windows design technique based on the frequency domain sampling theorem is explained. Windows designed using most conventional design techniques have as a parameter the sample number N, because these conventional design techniques basically use the discrete Fourier transform (DFT). On the other hand, the design technique proposed in this paper can realize windows for an arbitrary purpose, which need not include Nas a parameter. (C) 1999 Scripta Technica.