A system provides post-match control of microwaves in a radial waveguide. The system includes the radial waveguide, and a signal generator that provides first and second microwave signals that have a common frequency. The signal generator adjusts a phase offset between the first and second signals in response to a correction signal. The system also includes first and second electronics sets, each of which amplifies a respective one of the first and second microwave signals. The system transmits the amplified, first and second microwave signals into the radial waveguide, and matches an impedance of the amplified microwave signals to an impedance presented by the waveguide. The system also includes at least two monitoring antennas disposed within the waveguide. A signal controller receives analog signals from the monitoring antennas, determines the digital correction signal based at least on the analog signals, and transmits the correction signal to the signal generator.