Find a parametric representation of a cone

Find a parametric representation of the cone: $\displaystyle z=\sqrt{3x^2 + 3y^2}$ in terms of the parameters $\displaystyle \rho$ and $\displaystyle \theta$ where $\displaystyle \rho$, $\displaystyle \theta$, and $\displaystyle \Phi$ are spherical coordinates of a point on the surface. I know the conversions for rectangular coordinates to spherical coordinates and vice versa, but for some reason I'm blanking out on how to do this, and how to get rid of the $\displaystyle \rho$s in particular. Thanks in advance!