Nelinurklaine

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

Nelinurklaine on üks põhilainekujudest.

Nelinurklaine valem on

${\begin{aligned}x_{\mathrm {nelinurklaine} }(t)&{}={\frac {4}{\pi }}\sum _{k=1}^{\infty }{\sin {\left([2k-1]2\pi ft\right)} \over (2k-1)}\\&{}={\frac {4}{\pi }}\left(\sin(2\pi ft)+{1 \over 3}\sin(6\pi ft)+{1 \over 5}\sin(10\pi ft)+\cdots \right)\end{aligned}}$