Pulse-width scale of Fourier coefficients
= Pulse-width scale of Fourier coefficients
{title2=$n\sim T/w$}
For the <Fourier series of a periodic rectangular pulse>, the <sinc function> is nearly one when $nw/T\ll1$ and has its first zero at $nw/T=1$. Thus narrowing a pulse increases the range of significant <Fourier coefficients>. Only integer harmonic indices occur, so an envelope zero need not be an exactly vanishing coefficient.