This document discusses a novel technique called double square energy detection (DSED) for spectrum sensing in cognitive radio networks. Spectrum sensing is used to detect unused spectrum bands that secondary users can opportunistically access without interfering with primary users. Energy detection is commonly used due to its simplicity but suffers from high false alarm rates. The proposed DSED technique passes the detected signal through a double square energy detector before measuring received energy over a time interval and comparing to a threshold. Simulation results show DSED has a very high probability of detection and low complexity while reducing distortion and false alarms compared to conventional energy detection.