This paper addresses the problem of scheduling real-time dwells in multi-function phase array radar systems. To keep track of targets, a radar system must meet its timing and energy constraints. We propose a new task model for radar dwells to accurately characterize their timing parameters. We develop an algorithm of transforming every dwell task as a semi-period task so the dwell task can meet its timing constraint and the interarrival times of the task may not a constant. We also develop an enhanced template-based scheduling algorithm to schedule such tasks to meet the timing and energy constraints. Simulation results show that this algorithm can significantly improve the resource utilization.