A simple method using aided sliding rectangular windows for synchronization in energy detector (ED) receiver is proposed for impulse-based ultra wideband radios (IR-UWB) under binary pulse position modulation (PPM), therefore grants an attractive solution for gaining low complexity while the accompanying performance loss in terms of UWB signal reception is comparatively low. Also, a method is developed to suppress noise through accumulation of integrated results before synchronization point is reached. This proposed method can effectively reduce the impact of one of the major performance-degrading factors in ED receivers, i.e., noise caused by heightened noise floor due to large bandwidth product. Our theoretic work on this improved synchronization performance and relevant simulations are conducted on IEEE 802.15.4a channel models, and results show that the proposed design scheme can effectively decrease both the probability of false alarm and probability of missed detection.