Patent ID: 7151408

Claim:
A method of generating a radio-frequency alternating voltage with an amplifier operating in a resonant mode, the method comprising: switching on and off at least one switching element of the amplifier at a basic frequency to supply power from a uniform power source into a resonant circuit connected to a variable-resistance load, wherein the resonant circuit comprises several interconnected components, including reactive elements, which form, in their interconnected state during certain operating states of the amplifier, one or more parasitic oscillating circuits within the amplifier having undesired resonance frequencies other than the basic frequency; identifying one or more of the parasitic oscillating circuits having resonance frequencies lower than the basic frequency that develop in different operating states of the amplifier that differ from a normal operating state of the amplifier, wherein the different operating states are due to at least one of a load resistance that differs from a normal load resistance, a supply voltage that differs from a normal supply voltage, or an output power that differs from a normal output power; and preventing oscillations in the identified one or more parasitic oscillating circuits from arising by modifying the identified one or more parasitic oscillating circuits within the amplifier.