ok i know that bandwidth of pulse os infinity...let me convince u by what im saying..lets draw the pulse in the frequency domain..let the pulse width in time is T therfore the pulse in frequency is equal to sinc with first null equal to 1/T &extends to infinity..& since most of power exists in the main lobe( fisrt null to null) therefore we can assume that the bandwidth of the pulse is equal to 1/T ..u can review haykin for this..&by the way im a student in faculty of engineering &we took this method this year,,...i didn't invent it..
good luck