Studies Of Ultra-wideband (UWB) Narrow Pulse Generator

In the field of wireless communication, the research of ultra-Wideband (UWB) technology has become hot in recent years, many companies, research institutions, colleges are devoting themselves into this job. There are many branches of UWB technology: UWB radar, UWB wireless personal communication system, position identification UWB, and so on. Generally speaking, there are two sorts of UWB wireless communication: no carry wave UWB and carry wave modulated UWB. In the no carry wave UWB, narrow pulse generator is the most particular and important part. Large amount of researches and analysis of this kind of pulse generator has been done in this thesis, the following shows the main work of this thesis:The pulse waveform is necessary to be designed carefully because different pulse waveforms contain different frequency spectrums which decide the performances of communication systems. The characteristics of Gaussian pulse, UWB pulse based on sine wave, polynomial UWB Hermite pulse has been theoriticaly analysed. The waveforms and frequency spectrums of several kinds of pulses have been simulated through the Matlab 7. 0 code. Because the Gaussian pulse and its different order of differentials have the characteristics of UWB and can be produced easily and conveniently, they are widely used in UWB communication system. The Gaussian pulse and its different order of differentials can be generated from the UWB pulse generator designed in this thesis.There are many sorts of UWB pulse generators which have different elements. In this paper, the pulse generator circuits based on Tube Diode, avalanche transistor, Step Recovery Diode (SRD), digital method, filter method have been deeply analyzed and discussed. Based on the avalanche transistor and the filter method, two UWB pulse generators have been designed and simulated with the EWB 8. 0 simulator.Based on the avalanche characteristic of BJT-NPN, A UWB pulse generator with good performance is designed. Two inductors are added to the circuit in order to increase the output load, with almost the same pulse duration, the amplitude of the pulse is increased to 250% compared to the circuit with no inductor. A pulse with -38.299V amplitude, 663. 265ps pulse duration, 459. 184ps rise time and 969. 388ps fall time is got in the output. The selection of each component parameter in the circuit is detailed analysed and presented. It's suitable to be used in the UWB radar system. The pulse generator with different performance can be easily derived .through changing the parameters of the circuit components.The pulse generator based on filter is a new method to produce UWB pulse. The pulse shaping network is improved expressly. This thesis developed a high repetition frequency circuit which may generate a type of Gaussian pulse with 1.276ns pulse duration, 516. 455mV amplitude, 382. 653ps rise time and 1.658ns fall time. It's suitable to be used in UWB wireless communication system.The conclusion that the two circuits will be working stably in real circuits has been educed though the circuits stabilization analysis.