Tunable interdigitated capacitor

Patent metadata

Field	Value
Publication number	US-9424994-B2
Application number	US-201414245033-A
Country	US
Kind code	B2
Filing date	Apr 4, 2014
Priority date	Dec 10, 2013
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

A tunable capacitor implemented as interdigitated arrays of finger elements arranged so that the spacing between finger arrays may be adjusted. The design has a number of advantages including high capacitance for a given circuit area, small area for a given desired capacitance, mechanical stability, high self resonance frequency, and high quality factor.

First claim

What is claimed is:

1. A variable capacitor apparatus comprising:
a first terminal section comprising a first main body portion with a first set of two or more fingers extending from the first main body;
a second terminal section comprising a second main body portion with a second set of two or more fingers extending from the second main body;
the fingers of the first and second terminal sections each arranged in a respective array including at least two rows and at least two columns and;
a support, for supporting the first terminal section and second terminal section in a position with respect to one another such that at least some of the first set of fingers and at least some of the fingers of the second set of fingers are interposed between one another and for maintaining a space between the fingers of the respective first and second set of fingers; and
a controller, arranged to control a distance between the first and second set of fingers, and to thereby effect a change in capacitance of the apparatus.

2. The apparatus of claim 1 wherein the first and second body portions are aligned with respect to one another to provide uniform spacing between vertical and lateral side surfaces of the fingers extending from the respective first and second body portions.

3. The apparatus of claim 1 wherein the controller additionally effects a change in capacitance by moving the first and second terminal sections with respect to one another.

4. The apparatus of claim 1 additionally comprising:
a dielectric layer disposed on at least one of the first and second set of fingers.

5. The apparatus of claim 4 wherein the controller effects a change in capacitance by changing a dielectric constant of the dielectric layer.

6. The apparatus of claim 5 wherein the dielectric layer is formed of a voltage sensitive material and the controller changes a voltage applied to the dielectric layer.

7. The apparatus of claim 6 wherein the dielectric layer is formed of barium strontium titanate.

8. The apparatus of claim 3 additionally comprising:
a piezoelectric actuator, coupled to the controller, to further effect movement between the first and second terminal sections.

9. The apparatus of claim 3 additionally comprising:
a lever, coupled to one of the first and second terminal sections and to the controller, and wherein the controller controls a position of the lever.

10. The apparatus of claim 4 wherein the controller additionally:
effects a coarse adjustment to the capacitance by moving one of the first and second terminal sections with respect to one another; and
effects a fine adjustment to the capacitance by adjusting a voltage applied to the dielectric layer.

11. The apparatus of claim 1 wherein the fingers are rectangular, trapezoidal, or some other defined shape.

12. The apparatus of claim 1 further implemented as part of a tunable filter apparatus, the tunable filter apparatus further comprising:
at least one other capacitive element including a first transmission line section disposed adjacent a first dielectric material section having a dielectric constant;
at least one other inductive element including a second transmission line section disposed adjacent a second dielectric material section having a dielectric constant; and
the variable capacitor apparatus providing at least one shunt variable capacitive element.

13. The apparatus of claim 1 wherein the variable capacitor is disposed as a shunt capacitor in a transmission-line filter circuit.

Assignees

• Tdk Corp

Inventors

• Cherif Bouchaib

Classifications

• H01G5/18

  due to change in inclination, e.g. by flexing, by spiral wrapping · CPC title

• H01G5/145

  with profiled electrodes · CPC title

• H01G5/16 Primary

  using variation of distance between electrodes · CPC title

• H01G5/14

  due to longitudinal movement of electrodes · CPC title