Electronic components comprising adjustable-capacitance micro-electro-mechanical capacitors

• US 20060267558A1
• Filed: 02/17/2004
• Published: 11/30/2006
• Est. Priority Date: 02/18/2003
• Status: Active Grant

• Current Assignee: Agence Spatiale Europeenne
• Original Assignee: Agence Spatiale Europeenne
• Inventors: Petz, Felix, Wittig, Manfred
• Granted Patent: US 7,495,882 B2
• Time in Patent Office: Days
• US Class Current: 320/166
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 5/38 Multiple capacitors, e.g. ganged
• CPC Class Codes: H03J 2200/39 Variable capacitors implemented using microelectro-mechanical systems [MEMS]
• CPC Class Codes: H03J 3/185 with varactors, i.e. voltage variable reactive diodes

Abstract

Electronic component comprising at least one micro-electromechanical capacitor with adjustable capacitance comprising two electrodes free to move with respect to each other, and a control circuit (30) comprising measurement means (32) to measure the capacitance of the capacitor, means (35) of determining a capacitance difference between the measured capacitance of the capacitor and a set capacitance value, means (35 to 38) for injecting an electrical charge in a control electrode so as to create an electrostatic force capable of moving one of the two electrodes with respect to the other electrode and thus adjusting the capacitance of the capacitor, the injected electrical charge being determined as a function of the capacitance difference. This component is suitable for making an adjustable delay line, an adjustable quarter wave impedance transformer or for measuring the voltage, the power or the average intensity of an electrical signal.

Claims

1. Electronic component comprising at least one micro-electromechanical capacitor with adjustable capacitance comprising two electrodes (3, 4;

10, 11;

45, 46;

44, 47;

61, 62) free to move with respect to each other,

characterised in that it comprises a control circuit (30) comprising measurement means (32) to measure the capacitance of the capacitor (3, 4;

10, 11;

45, 46;

44, 47;

61, 62), means (35) of determining a capacitance difference between the measured capacitance of the capacitor and a set capacitance value, means (35 to 38) of injecting an electric charge into a control electrode (4, 10, 44, 62) so as to create an electrostatic force capable of moving one of the two electrodes (4, 10, 45, 44, 62) with respect to the other electrode (3, 11, 46, 47, 61) and thus adjusting the capacitance of the capacitor, the injected electric charge being determined as a function of the difference in capacitance.

2. Electronic component according to claim 1, characterised in that the means of measuring the capacitance of the capacitor comprise an alternating current source (32).

3. Electronic component according to claim 1 or 2, characterised in that the injection means of an electric charge comprise a pulsed current source (35 to 38)

4. Electronic component according to any one of claims 1 to 3, characterised in that it is integrated with the control circuit (30) in an integrated circuit.

5. Electronic component according to any one of claims 1 to 4, characterised in that the control electrode is one of the two electrodes (4, 10, 62) of the capacitor.

6. Electronic component according to claim 5, characterised in that the respective frequencies of the alternating current source (32) and the pulsed current source (35 to 38) are lower than and remote from the frequencies of signals processed by the component.

7. Electronic component according to claims 1 to 4, characterised in that the control electrode (44) is mechanically coupled to one of the two electrodes (45) and electrically isolated from this electrode.

8. Electronic component according to any one of claims 1 to 7, characterised in that it comprises a plurality of micro-electromechanical capacitors with adjustable capacitance each comprising a first and a second electrode (3, 4) free to move with respect to each other, the first electrodes of the capacitors being interconnected in series by conducting tracks (5) in the form of a winding and each forming an inductance so as to form a chain of electrodes, the ends of which are connected to two corresponding connection terminals of the component through two corresponding conducting tracks (6) in the form of a winding, each forming an inductance, the second electrodes of the capacitors being connected to a ground plane.

9. Electronic component according to any one of claims 1 to 7, characterised in that one of the two electrodes (10) has two connection terminals (13, 14) and a length (1) between the two connection terminals equal to a quarter of the wavelength of the signals processed by the component, so as to form a quarter wave impedance transformer.

10. Electronic component according to any one of claims 1 to 7, characterised in that this component comprises a plurality of micro-electromechanical capacitors (15, 16, 17, 18) with adjustable capacitance comprising two electrodes (10, 11) free to move with respect to each other, one of the mobile electrodes in each of the capacitors having two connection terminals (13, 14) connected to corresponding connection terminals of the component (20) and the corresponding lengths (1) between the two connection terminals being different from each other, so as to form a set of quarter wave impedance transformers connectable in series, so as to adapt the total length of the capacitors interconnected in series to the wavelength of the signals processed by the component.

11. Electronic component according to any one of claims 1 to 7, characterised in that it is used to measure at least one characteristic of a signal applied to one (45, 62) of the two electrodes (45, 46;

61, 62) of the capacitor, the control circuit (30) being designed to keep the distance (d) between the electrodes of the capacitor constant, independently of the signal applied to one of the two electrodes.

12. Electronic component according to claim 11, characterised in that the control circuit (30) is coupled to means (58) of measuring the voltage applied to the control electrode (44, 62), that is proportional to the average voltage of the signal applied to one of the two electrodes.

13. Electronic component according to either claim 11 or 12, characterised in that the distance between the two electrodes (45, 62) is balanced in the absence of a signal, the control circuit including means of keeping the distance between the electrodes at a value other than the equilibrium value.

14. Electronic component according to any one of claims 11 to 13, characterised in that this component is used to measure the average power of the signal applied to one of the two electrodes (45, 46;

61, 62).

15. Electronic component according to any one of claims 11 to 14, characterised in that this component is used to measure the average intensity of the signal applied to one of the two electrodes (45, 46;

61, 62).