Ultra-wideband (UWB) communication is currently considered as a key technology of the next generation wireless personal area network (WPAN) and wireless local area network (WLAN). UWB operation do not require a spectrum license but UWB devices are required to share spectrum with licensed narrow band users. This paper presents a novel system for direct sequence (DS) UWB and the proposed dynamic bandwidth direct sequence (DBDS) system focuses on exploring a new idea rather than concentrating on impulse manipulation, provides a cognitive solution for DS-based UWB in a much simpler and more efficient way. The proposed system is able to transfer data under a fraction of original spread spectrum signal bandwidth and different spectral shapes while maintaining the same data rate. The system does not require generating specific impulse for working environment, therefore significantly reduces the system complexity. Simulation results demonstrate that the DBDS has a very exciting performance. Even received with different bandwidths and different spectral shapes, the data information can still be fully recovered at the same data rate.