The Research And Design Of The Pulse-Based Ultra-Wideband System

With the growing request on wireless data transfer, how to improve its rate has become a serious problem. The present of UWB(Ultra-Wideband) has offered an effective way to resolve the contradiction between growing message capacity and limited frequency resource. It has unique value on application in many fields such as public security, military efficiency, aviation safety, medicinal use, consumer products and services.The first problem for UWB to solve is avoiding interference with other communication systems, and the basic standard is its energy radiation should be restricted within the limit by FCC(Federal Communications Commission). The radiation of the UWB pulse in pulse-based UWB system is determined by the impulse waveform. It's a challenging task to find a pulse signal which is band-limited, time-limited and has a high spectrum utilization rate to satisfy the spectrum occultation of FCC. Meanwhile, designing low power chips of transceiver systems has become a hotpot on UWB research.This paper introduced the technical characters and current research situation of UWB at first. Then the application technology of UWB had been analyzed and the modulation, multiple access, interference and coexistence in each method had been compared. Based on that, a research on UWB pulse wave had been made, which was mainly on two sides, time-domain and frequency-domain. On the time-domain side, this paper mainly analyzed the power spectrum density of existing UWB signal pulse and combined-pulse based on Gaussian function; on the frequency-domain, designed Raised Cosine Pulse and Quadratic Root Raised Cosine Pulse after a study on a new pulse designing method, direct time-domain method, and then got the expressions of those pulses on time-domain. The performance of the pulse designed in this paper was proved to be better than the classic ones. These laid a theoretical foundation for designing pulse shaping filter.A transceiver module based on direct sequence UWB system was designed and implemented in this paper. At the stage of design, the plan based on FPGA direct sequence UWB system was got, of which the module was established under AWGN channel. A simulation of this system was made using Matlab and the bit error rate was calculated. At the stage of implementation, the baseband signal processing module, pulse shaping filter and direct sequence UWB system were implemented with FPGA. Then every single module and the whole system were tested under hardware environment. The experiment result shows the advantage of this system, which is low power, low time delay, compared with the traditional modeling technique, and its value to be widely popularized.