Combining the single-input and multiple-output (SIMO) technology with the frequency-modulated differential chaos shift keying (FM-DCSK) modulation, a novel SIMO FM-DCSK ultra-wideband (UWB) system is proposed in this paper. Single sub-stream signal based on high order Walsh function is adopted in the transmitter and two detection schemes are presented in the receiver. Simulations and analyses show that the proposed system with differential correlation detection possesses superior performance as well as relatively low complexity, thus is particularly suitable for the low rate and low power applications in wireless personal area networks (WPANs).