<p>This paper presents a new family of cosine windows, which provides several options for the mainlobe width and the peak sidelobe for a given sidelobe decay. This is achieved by introducing an additional parameter in the argument of the cosine functions of the time domain window. The proposed cosine windows are designed for maximum asymptotic decay of sidelobes; so for applications requiring filters with good harmonic suppression, these windows can be employed to realize the desired filters.</p>