EISCAT3D is an ionospheric radar currently under construction in Northern Fenno-Scandinavia. The radar will make 3D measurements of the ionosphere at 50–1000 km altitudes. We show that the so-called multipurpose radar modulations and optimal data analysis can improve the time resolution of the measurements by more than an order of magnitude, and they enable one to measure ion-neutral collision frequencies, which are proportional to neutral particle density, in the lower ionosphere.