Design of a DS-UWB Transceiver

Abstract: Ultra Wide Band (UWB) is a new spectrum allocation which was recently approved by the Federal Communication Commission (FCC) and is under study in Europe and Asia. It has emerged as a solution to provide low complexity, low cost, low power consumption, and high-data-rate wireless connectivity devices entering the personal space. Any wireless system that has a fractional bandwidth greater than 20% and a total bandwidth larger than 500MHz enters in the UWB definition. At the emission level, UWB signals have a mask that limits its spectral power density to -41.3dBM/MHz between 3.1Ghz and 10.6GHz. There are two approaches that have been studied in order to use the 7.5Ghz allocated for UWB systems. First, OFDM techniques can be used to cover the entire spectrum; these techniques are called multi-band UWB. On the other hand, the second approach makes use of impulse radios which generate very-short-duration baseband pulses that occupy the whole spectrum. The objective of this thesis is to study, design, prototype, and test a UWB impulse radio using off-chip components. A Direct Sequence (DS) UWB transceiver architecture was selected. The transmitter uses first derivative Gaussian pulses that are modulated using a bi-phase modulation technique. The pulse rate of the system is 100MHz and the bit rates under investigation were 100Mbps, 50Mbps, 25Mbps, and 10Mbps. The transmitter and receiver were divided in functional blocks in order to execute system level simulations. The transmitter was implemented in both schematics and layout, and the UWB pulse generator block was constructed and tested in order to validate its functionality. On the other hand, the off-chip implementation of the receiver presented particular difficulties that made its construction not possible in this study. As a result, the blocks of the receiver were implemented in Matlab and the performance of the whole transceiver was estimated through numeric simulations. Finally, a case study for the multi-user capability of the system was presented.