A dipole oscillation tank circuit includes a first capacitive structure, an inductive structure, and a second capacitive structure connected in series. The tank circuit transfers electric energy back and forth between the capacitive structures in dipole oscillation cycles. A renewal circuit injects energy into the tank circuit to replenish energy lost during the oscillation cycles. A switch is connected in parallel across the first capacitive structure and in parallel across the inductive structure and the second capacitive structure. During one phase of the oscillation cycles, the switch is opened for current to flow through the first capacitive structure and the inductive structure, and then closed to bypass the first capacitive structure. During another phase of the oscillation cycles, the switch is closed to bypass the first capacitive structure and then opened for current to flow through the first capacitive structure and the inductive structure.