A thermal increase system comprising: a radio frequency, RF, signal source configured to produce an RF signal; a first electrode that is electrically coupled to the RF signal source and that is configured to receive the RF signal from the RF signal source and to responsively radiate electromagnetic energy into a cavity positioned next to the first electrode; a conductive structure that is disposed a distance from the first electrode, wherein the conductive structure overlaps and is capacitively coupled to a portion of the first electrode; and a ground reference structure that is electrically coupled to the conductive structure, wherein: the first electrode has a first side and a second side opposite the first side; the cavity is positioned next to the first side of the first electrode; the conductive structure is disposed the distance from the second side of the first electrode; and the first electrode and the conductive structure form a parallel plate capacitor, the thermal increase system further comprising: a transmission path electrically coupled between an output of the RF signal source and the first electrode, wherein the RF signal has a forward signal power along the transmission path; and an impedance matching network electrically coupled along the transmission path between the output of the RF signal source and the first electrode, wherein the impedance matching network comprises a variable inductance network (710, 711). a radio frequency, RF, signal source configured to produce an RF signal; a first electrode that is electrically coupled to the RF signal source and that is configured to receive the RF signal from the RF signal source and to responsively radiate electromagnetic energy into a cavity positioned next to the first electrode; a conductive structure that is disposed a distance from the first electrode, wherein the conductive structure overlaps and is capacitively coupled to a portion of the first electrode; and a ground reference structure that is electrically coupled to the conductive structure, the first electrode has a first side and a second side opposite the first side; the cavity is positioned next to the first side of the first electrode; the conductive structure is disposed the distance from the second side of the first electrode; and the first electrode and the conductive structure form a parallel plate capacitor, the thermal increase system further comprising: a transmission path electrically coupled between an output of the RF signal source and the first electrode, wherein the RF signal has a forward signal power along the transmission path; and an impedance matching network electrically coupled along the transmission path between the output of the RF signal source and the first electrode, wherein the impedance matching network comprises a variable inductance network (710, 711). a transmission path electrically coupled between an output of the RF signal source and the first electrode, wherein the RF signal has a forward signal power along the transmission path; and an impedance matching network electrically coupled along the transmission path between the output of the RF signal source and the first electrode, wherein the impedance matching network comprises a variable inductance network (710, 711).