FSR-UWB (TR-UWB without the Delay Element): Effect of Impulse Dithering and Experimental Results

Recently, we have proposed a new transmitted reference (TR) ultra-wideband (UWB) radio scheme. Rather than separating the data and reference signals by a time delay as in a standard TR-UWB system, the new scheme uses a slightly frequency-shifted reference (FSR) that is orthogonal to the data-bearing signal over the symbol interval. It has been shown in our previous work that such a FSR-UWB system that employs a regular impulse train both achieves a simpler receiver architecture and outperforms a standard TR-UWB system. However, as noted briefly in this previous work, the employment of a regular impulse train will lead to distinct lines in the spectrum of the transmitter output, and, thus, in practice, the impulse train would need to be randomly dithered. In this paper, the spectral characteristics of the FSR-UWB system are examined in detail. After demonstrating that the spectrum of the originally proposed system does indeed exhibit spectral lines, a time-hopping (TH) code is added to dither the impulse train. It is demonstrated that the spectrum of the resulting system is the smooth spectrum desired and that there is nearly no performance loss caused by the employment of such a TH code. Finally, circuit diagrams for the implementation of the FSR-UWB system are provided, and experimental results are discussed