A surgical generator configured to output a high-frequency alternating voltage to a surgical ultrasound instrument. An oscillator generates a driving oscillation for an inverter generating high-frequency voltage being for the surgical instrument. A matching-coil emulation device includes a correction device acting on the driving oscillation. The correction device includes a mixing unit and a feedback circuit, modifying the driving oscillation supplied to the inverter. An estimator calculates a virtual current which would flow in the emulated matching-coil if it were present, based on this and a measured output voltage an artificial phase shift is determined for steering of the oscillator. Thereby, the transfer function is reshaped mimicking that of a physical matching coil. Accordingly, a bulky matching coil that must be precisely tuned to the ultrasound instrument and restricts use of newer and different ultrasound instruments is no longer needed.