A digital high-speed load pull tuner comprises a slide screw automatic tuner in a traditional reflection configuration and an active forward injection loop using a digital tuner in a transmission configuration. The forward active injection loop comprises two compact signal couplers of which at least one is adjustable, a digital tuner, circulator, feedback power amplifier; the passive tuner comprises one or more remotely controlled mobile carriages sliding along the slabline and carrying metallic tuning probes, used to create passive reflection factors. The incoming signal is sampled, modulated in amplitude and phase by the digital tuner and fed back into the slabline synchronizing with the passive reflected signal, to create a partially virtual load presented to the DUT.