Slightly frequency-shifted reference ultra-wideband (UWB) radio: TR-UWB without the delay element

Recently, there has been significant interest in ultra-wideband (UWB) radio techniques. A promising UWB technique being widely considered for low data rate applications, such as those often encountered in sensor networks is the transmitted reference (TR) UWB scheme. However, the standard TR-UWB scheme, while often motivated by the simplicity of its receiver is still dogged by implementation concerns. In particular, the receiver requires an extremely wideband delay element, which is difficult to incorporate into low-power integrated systems. In this paper, a transmitted-reference scheme is proposed in which the separation between the data and reference signals, rather than being a time delay, is a slow rotation over the symbol interval. This provides a (slightly) frequency-shifted reference that, while orthogonal to the data-bearing pulse, still goes through a nearly equal channel. A detailed analysis of the proposed scheme is provided, and numerical results demonstrate that the proposed system not only achieves the primary goal of providing a much simpler receiver architecture, but also that it outperforms the standard TR-UWB system.