Impulse Waveform Research And Design For UWB System

Ultra-wideband(UWB) communication has a lot of advantages, such as simple system structure, high system capacity, exceptional multi-path immunity, low power spectral densities(PSD), and safety in communication, high positioning accuracy,etc. However, two facts limit its development: extremely low emission power and spectrum sharing. As to the former one, it affects the communication distance of the UWB system, while the latter one interferes other wireless communication systems while sharing spectrum. Ultra-wideband pulse waveform designing is very suitable to solve above problems.In order to prevent interference with other systems, we need to limit the signal power of UWB system with strict restrictions, emission mask is used to limit the maximum power usually. In this paper, impulse waveform is designed based on radiation masking. We start from the gauss single pulse, firstly combination pulse that with more advantage is elicited in this paper, then looking for better performance of combination pulse method. Finally, the interference suppression is realized by the trap method.This paper studies the Gaussian function, and analyzes the function of the pulse waveform design method. We realized two kinds of pulse combination here: random coefficient combination and minimum mean square error, and separately use Gaussian derived function and cosine Gaussian function as the base functions to form combination, and analysis the simulation of each combination pulse. Through simulation we found that combination pulse of the random coefficient is better than a single Gaussian pulse in terms of spectrum utilization, the disadvantage is that the efficiency is low; combination pulse based on LES criterion is higher than single pulse in term of frequency spectrum utilization, but there is no guarantee that at each frequency point meet the requirements of radiation masking.In order to make each frequency point meet the demand of the emission mask, this paper proposes a method based on genetic algorithm(GA), the thought is combined pulse function and emission mask the minimum mean square error of fitness function, through the combination of pulse repeated optimization to get the highest fitness pulse. Then comparing the combination pulse with random coefficient and Five derivative Gaussian pulse from the spectrum efficiency, single link error rate, multiple access performance. Through simulation, we found that the combination of genetic algorithm to obtain the pulse, the spectrum utilization is higher than other pulses, and can satisfy the requirements of radiation masking at each frequency point. In the case of large signal noise ratio(SNR), error rate is lowest; Under the condition of the same number users, its performance is the best.In order to suppress the narrowband interferences and achieve the purpose of coexistence, this paper use the method of trap to pulse spectrum shaping. Starting from the transmitting terminal, to trap the firing pulse spectrum directly. Respectively from pulse power spectral density and transmission distance two aspects to compare the pulse before and after the notch. The results showed that did not reduce the whole spectrum of power spectrum, only has the notch effect near the interference spectrum. Trap can suppress interference of narrowband pulse and not affect its good transmission performance. This method implements the interference suppression and ensure the performance of pulse, so it achieves the research purpose. The pulse designed in this paper achieved the purpose of the study.