This study addresses an important challenge of signal detection for the moving devices in cognitive radios over a general non-line-of-sight (NLOS) or line-of-sight (LOS) time-variant multipath fading channel, which is a practical environment for modern mobile communications. To this aim, we propose a new feature detector (FD) based on the likelihood-ratio test (LRT), which suggests us to employ the stationarity of received signals for the signal detection. As such, the detection performance can be greatly enhanced by the proposed technique without needing any channel equalization techniques on received signals. Additionally, two major synchronization impairments are considered which were often neglected in conventional detectors. According to simulation results, the performance of the proposed detector can achieve the detection probability of 0.9 under the false-alarm rate of 0.1 and vehicular speed of 100 km/hr.