\documentclass{scrartcl}
\usepackage{color}
\usepackage{multicol}
\usepackage[final]{graphicx}
\usepackage{pst-plot,pstricks}
	\input{pstplot-logarithmic-axes}
\begin{document}
	\psset{xunit=2cm,yunit=2cm}
	\begin{pspicture}(-1.5,-0.7)(1.5,0.7)
		\psaxes[Dx=1,Dy=0.25]{->}(0,0)(-1.5,-0.7)(1.5,0.7)
		\psplot[plotstyle=curve,linecolor=green]{-1.5}{-0.0001}{1.5 x 1 atan 180 div sub}
		\psplot[plotstyle=curve,linecolor=green]{0.0001}{1.5}{0.5 x 1 atan 180 div sub}
		\rput[l](1.6,0){$\frac{\omega}{\omega_0}$}
		\rput[r](-0.2,0.8){$\frac{\Theta}{\pi}$}
	\end{pspicture}
\end{document}
