Bessel Functions of the First Kind

The amplitude of the $k^{\mbox{th}}$ sideband is given by $J_k(I)$, a Bessel function² of the first kind, of order $k$.

Figure 11: Bessel functions of the first kind, plotted for orders 0 through 5.

Notice that higher order Bessel functions, and thus higher order sidebands, do not have significant amplitude when $I$ is small.

Higher values of $I$ therefore produce higher order sidebands.

In general, the highest-ordered sideband that has significant amplitude is given by the approximate expression $k = I + 1.$