Tuned resonant circuits

A method of using a self-adaptive reactive element in a resonant circuit, said self-adaptive reactive element comprising a non-linear capacitor and having a reactive impedance which automatically adjusts to a frequency of a signal applied to said resonant circuit to bring a resonant frequency of said resonant circuit into alignment with said frequency of said applied signal, said reactive impedance of said self-adaptive reactive element varying between a maximum and a minimum value, the method comprising:

• deriving a power supply from said resonant circuit;
• using said power supply to switch additional reactive impedance in or out of said resonant circuit until said maximum or minimum value of said reactive impedance of said self-adaptive reactive element is reached, such that said self-adaptive element behaves substantially as a non-adaptive reactive element;
• and
• switching a capacitance of the non-linear capacitor to one value and to another, different value according to an instantaneous value of a resonant signal of the resonant circuit and during a cycle of the resonant signal, to thereby determine a duty cycle of said capacitance switching.

A tuned circuit component comprising:

• a first capacitor;
• a first MOSFET;
• at least one second MOSFET;
• a second capacitor (C3) coupled in series with said first MOSFET, said series coupled second capacitor and first MOSFET being coupled in parallel with said first capacitor;
• at least one third capacitor coupled in series with said at least one second MOSFET, said series combination of said third capacitor and said second MOSFET being coupled in parallel with said first capacitor;
• and
• a plurality of said third capacitors each coupled in series with a respective said second MOSFET, each said series combination of said third capacitor and said second MOSFET being coupled in parallel with said first capacitor.

A self-powered resonant circuit, the circuit comprising:

• at least one self-adaptive resonant circuit comprising a non-linear capacitor, said self-adaptive resonant circuit having a resonant frequency which automatically tunes to a frequency of a signal applied to said self-adaptive resonant circuit;
• a power supply circuit to coupled to said self-adaptive resonant circuit to derive a power supply from a resonant signal in said self-adaptive resonant circuit;
• a plurality of switched reactive elements each coupled to said self-adaptive resonant circuit;
• and
• a controller to selectively switch said switched reactive elements into said selfadaptive resonant circuit until said self-adaptive resonant circuit has reached substantially a limit of a range of said automatic tuning,
• wherein the self-powered resonant circuit is configured to switch a capacitance of the non-linear capacitor to one value and to another, different value according to an instantaneous value of a resonant signal of the resonant circuit and during a cycle of the resonant signal, to thereby determine a duty cycle of said capacitance switching.