I'm working with UWB IR transmitter design., for that , many peoples uses Gaussian pulses to relate the UWB pulses ..... i need a clear idea , whythey relate gaussian pulses , and why they go for 5 th derivative, and some research papers says taking first 15 derivatives for generating a pulses in the range of 3.1 to 10.6GHz.... i know the FCC emission mask... but i need a idea why and what for need of gaussian pulse and derivatives of that..??????