The use of the lower (left-hand) X-mode cutoff for measuring core to edge radial profiles of the perpendicular plasma velocity and radial electric field Er via microwave Doppler reflectometry/backscattering (DR) is demonstrated in the ASDEX Upgrade tokamak (AUG). With high toroidal magnetic fields T and core plasma densities m−3 the lower X-mode cutoff becomes accessible to the AUG low-field-side launch, V-band Doppler reflectometers. Example velocity profiles are presented for high-confinement H-mode plasmas, with and without edge-localized-modes, and are found to compare well with velocity measurements from Charge exchange recombination spectroscopy. With the aid of 2D full-wave numerical simulations of the actual experimental conditions, Er profile measurement errors, due to uncertainties in the DR probing wavenumber and backscatter location r, plus estimates of the minimum wavenumber and radial Δr error-bars, are obtained from the instrument response function. Some practical limitations and issues involving the lower X-mode cutoff for core tokamak/stellarator DR probing are also investigated using 2D full-wave and 3D ray/beam tracing codes.