Nelinurklaine

Nelinurklaine (inglise keeles square wave) on harmooniline liitheli, mis koosneb ainult paarituarvulistest osahelidest.

Nelinurklaine on üks põhilainekujudest.

Nelinurklaine valem on

$\begin{align} x_{\mathrm{nelinurklaine}}(t) & {} = \frac{4}{\pi} \sum_{k=1}^\infty {\sin{\left ([2k-1]2\pi ft \right )}\over(2k-1)} \\ & {} = \frac{4}{\pi}\left (\sin(2\pi ft) + {1\over3}\sin(6\pi ft) + {1\over5}\sin(10\pi ft) + \cdots\right ) \end{align}$