Cognitive radio is a system which improves the utilization of the spectrum by sensing the white spaces in its vicinity. This sensed information will be utilized by the Secondary User (SU) to transmit the data. But some of the malicious users attacks the system by generating the signal same as that of the primary transmitter. The attack caused by generating the signal same as that of the primary transmitter is called as Primary User Emulation Attack (PUEA). In this paper the Signal Activity Pattern Acquisition and Reconstruction System (SPARS) is used to detect the attack. But this system suffers from low True Positive Rate. To increase the True positive rate or sensitivity a new technique was proposed called as Weighted Sequential Probability Ratio Test (WSPRT). By improving the true positive rate or sensitivity, the detection capability of the system will be improved.