Cognitive radio (CR) has been proposed as a promising and effective technology to improve radio spectrum utilization. The primary objective of the CR is to handle the non-interference rules with any primary users (PUs). Highly sensitive and optimal spectrum sensing detectors are required in order to avoid harmful interference to PUs. Multitaper spectrum seems to be the most appealing one for spectrum sensing CR because of its accurate identification and estimation and low computational complexity. Mulitaper uses small set of tapers and multiple orthogonal prototype filters to reduce the variance. The Fourier transform of a Slepian sequence, originally known as discrete prolate spheroidal sequences (DPSS), gives maximum energy density inside a given bandwidth and less spectral leakage with better specifications has been investigated in this paper and shows that no other window in signal processing can satisfy this property