A system and method for generating microwaves for microwave enhanced combustion (MEC) input to an MEC antenna of an internal combustion engine. The system uses a microwave generator and a directional coupler, which delivers the MEC input signal to the MEC antenna and receives a reflected signal from the MEC antenna. A feedback path determines a desired frequency for the MEC input signal, based on the reflected signal, and also determines a power feedback correction value. An open loop path determines desired power and timing for the MEC input signal, based on various engine conditions. The desired power is corrected with the power feedback correction value.