Fluid Dielectric Variable Capacitor

Abstract

The variable capacitor includes an enclosure having a first conductive collar and a second conductive collar separated by an electrically insulating intermediate element. A movable capacitor plate assembly is electrically coupled to the first conductive collar, and a stationary capacitor plate assembly is electrically coupled to the second conductive collar. An actuator extends into the enclosure to advance and retract the movable capacitor plate assembly relative to the stationary capacitor plate assembly. A hermetically sealed volume within the enclosure includes a fluid dielectric that acts as a dielectric between the capacitor plates of the movable capacitor plate assembly and the capacitor plates of the stationary capacitor plate assembly. A flexible structure is provided to accommodate the displaced fluid dielectric when the movable capacitor plate assembly is advanced relative to the stationary capacitor plate assembly.

Description

[Background technology]

[0001] This application claims priority to U.S. Provisional Patent Application No. 17 / 739,595, filed May 9, 2022, the contents of which are incorporated herein by reference.

[0002] Variable capacitors are used in a variety of applications, particularly those involving high frequency, high power signals. For example, variable capacitors may be used in oscillator circuits for high frequency radio transmission, high frequency power supplies for semiconductor manufacturing equipment, and impedance matching networks where the impedance of a time-dependent, high frequency load is matched to the impedance of a generator.

[0003] A capacitor essentially consists of two spaced apart capacitor plates with an insulator or dielectric material disposed between them. As used herein, the terms "dielectric," "dielectric material," and "dielectric medium" are used interchangeably to refer to a material (i.e., solid, liquid, or gas) that is polarizable in the presence of an electric field, typically expressed in terms of the material's electric susceptibility, χ.

[0004] In a vacuum variable capacitor, the two capacitor plates are placed in high vacuum (e.g., 10 -6 Torr or less. In some vacuum variable capacitors, the capacitor plates may be configured as multiple interdigitated concentric cylindrical coil plates, and the tunability of the capacitor may be achieved through physically adjusting the interdigitated overlap length.

[0005] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 illustrates an exterior side view of a liquid dielectric variable capacitor, according to one or more examples. [Figure 2] FIG. 2 is a cross-sectional perspective view of the liquid dielectric variable capacitor of FIG. 1. [Figure 3] 2 is a cross-sectional side view of the liquid dielectric capacitor of FIG. 1, with the capacitor plates in a first positional relationship. [Figure 4] 2 is a cross-sectional side view of the liquid dielectric variable capacitor of FIG. 1, with the capacitor plates in a second position; [Figure 5] FIG. 2 is an exploded perspective view of a fixed capacitor plate assembly and a movable capacitor plate assembly in the example of FIG. 1. [Figure 6] FIG. 1 is a schematic diagram of a matching network including a liquid dielectric variable capacitor, according to one or more examples. [Figure 7] FIG. 2 is an exploded perspective view of a fixed capacitor plate assembly and a movable capacitor plate assembly in the example of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0007] It is emphasized that, according to standard industry practice, various features are not drawn to scale. In fact, dimensions of various features may be arbitrarily increased or decreased for clarity of discussion or illustration.

[0008] Illustrative examples of the claimed subject matter are disclosed below. In the interest of clarity, not all features of an actual implementation are described in each example herein. It will be appreciated that in developing such an actual implementation, numerous implementation-specific decisions may be made to achieve the specific goals of the developers, which may vary from implementation to implementation, including, for example, compliance with system- and business-related constraints. It will be further appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0009] The terms "comprise" and "may comprise" as used in this disclosure indicate the presence of disclosed features, operations, and components, but do not limit the presence of one or more additional features, operations, and components. In this disclosure, terms such as "comprise" and / or "have" may be interpreted to indicate certain features, numbers, operations, components, or combinations thereof, but should not be interpreted to exclude the presence or possibility of one or more additional other features, numbers, operations, components, or combinations thereof.

[0010] As used herein, the article "a" or "an" is intended to have its ordinary meaning in the patent art, i.e., "one or more." As used herein, the term "about," when applied to a numerical value, generally means within the tolerance of the equipment used to generate the value, or in some instances, ±10%, or ±5%, or ±1%, unless otherwise expressly specified. Further, as used herein, the term "substantially," when used herein, means, for example, majority, or almost all, or all, or an amount ranging from about 51% to about 100%, etc. Furthermore, the examples herein are intended for illustration only and are presented for discussion and not limitation.

[0011] As used herein, to "provide" an item means to have ownership and / or control of the item. This may include, for example, forming (or assembling) some or all of the item from its constituent materials and / or obtaining ownership and / or control of an already formed item.

[0012] Unless otherwise defined, all terms, including technical and / or scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In addition, unless otherwise defined, all words defined in commonly used dictionaries may not be unduly interpreted.

[0013] The subject matter disclosed herein is directed to examples of variable capacitors incorporating a liquid dielectric material between the capacitor plates. The liquid dielectric material may increase the effective maximum capacitance of the variable capacitor for a given geometric shape of the capacitor plates. The liquid dielectric material may also increase the breakdown voltage of the capacitor for a given geometric shape of the capacitor plates. The liquid dielectric material may also provide additional dissipation of thermal energy within the variable capacitor, for example, compared to a vacuum capacitor, since the liquid dielectric may have a higher thermal conductivity than a vacuum.

[0014] FIG. 1 is an exterior side view of a liquid dielectric variable capacitor 100 according to one or more examples. The liquid dielectric variable capacitor 100 includes an enclosure 102 having an actuator end cap 104, which will be described below. In the example of FIG. 1, the enclosure 102 includes a first conductive collar 106 and a second conductive collar 108 that are electrically insulated from one another by an electrically insulating intermediate element 110. The electrically insulating intermediate element is hermetically bonded to the conductive collars 106 and 108. In examples, the conductive collars 106 and 108 can be metal, such as silver-plated copper, copper, brass, aluminum, or brazed aluminum. In examples, the electrically insulating intermediate element 110 can be substantially cylindrical and can be made of ceramic or other suitable insulating material.

[0015] The enclosure 102 further includes a downwardly enlarged housing 112 coupled to the lower portion of the second conductive collar 108 for housing a flexible liquid dielectric reservoir structure, described below. An upper end of an actuator 114 extends out of the actuator end cap 104. In some examples, the actuator 114 is threaded and may be rotated to advance and retract the movable capacitor assembly within the enclosure 102. In other examples, the actuator 114 may be advanced and retracted by a linear motor, an electromagnetic coil arrangement, or a hydraulic or pneumatic system. In examples, a conductive mounting plate 116 may be provided in electrical contact with the first conductive collar 106 to facilitate physical mounting of the liquid dielectric variable capacitor 100 in an operating environment. Additionally, the conductive mounting plate 116 may provide an external electrical connection for the liquid dielectric variable capacitor 100, as described below.

[0016] Figure 2 is a cross-sectional perspective view of a liquid dielectric variable capacitor 100 according to one or more examples. Figures 3 and 4 are front cross-sectional views of the liquid dielectric variable capacitor 100. As shown in Figures 2-4, a first capacitor plate assembly 118 and a second capacitor plate assembly 120 are housed within the enclosure 102. The first capacitor plate assembly 118 includes a first capacitor plate 122 coupled to a first electrode 124. The first electrode 124 of the first capacitor plate assembly 118 is coupled to the underside of a first mounting plate 126. The second capacitor plate assembly 120 includes a second capacitor plate 128 coupled to a second electrode 130. The second electrode of the second capacitor plate assembly 120 is mounted on top of a second mounting plate 132.

[0017] 5 is an exploded perspective view of first capacitor plate assembly 118 and second capacitor plate assembly 120, according to one or more examples. As shown in FIG. 5, first capacitor plate 122 and second capacitor plate 128 comprise wound concentric cylindrical coil capacitor plates, with first capacitor plate 122 electrically attached at a top end to a first electrode 124 configured as a cylindrical coil and second capacitor plate 128 attached at a bottom end to a second electrode 130 configured as a cylindrical coil.

[0018] In an example, first capacitor plate assembly 118 and second capacitor plate assembly 120 are configured such that first mounting plate 126 and second mounting plate 132 can be positioned relative to one another such that first capacitor plate 122 can be concentrically interdigitated with second capacitor plate 128. In an example, first capacitor plate 122 and second capacitor plate 128 do not directly contact one another, although the distance between first mounting plate 126 and second mounting plate 132 can be adjusted as described herein to vary the length of concentric overlapping interdigitation between first capacitor plate 122 and second capacitor plate 128, thereby adjusting the effective capacitance established between first capacitor plate 122 and second capacitor plate 128. In an example, first capacitor plate 122 and second capacitor plate 128 may be fabricated from materials traditionally used for such structures in vacuum variable capacitors (e.g., oxygen-free copper or copper-plated brass).

[0019] 2-4, and with particular reference to FIGS. 3-4, in one or more examples, flexible structure 134 is sealingly mounted between a top surface 136 of first mounting plate 126 and an inner top portion 138 of first collar 106. First electrode 124 is mechanically and electrically coupled to a bottom surface 142 of first mounting plate 126.

[0020] A flexible liquid dielectric reservoir structure 140 is sealingly attached to a bottom surface 144 of the second mounting plate 132 and has a closed bottom end 146. The second electrode 130 is mechanically and electrically coupled to a top surface 148 of the second mounting plate 132.

[0021] In the examples herein, flexible structure 134 and flexible liquid dielectric reservoir structure 140 are implemented as flexible bellows that can expand or contract in length, thereby changing their respective internal volumes. It is contemplated that other flexible structures can be implemented to achieve the functionality of flexible structure 134 and flexible liquid dielectric reservoir structure 140 described herein.

[0022] 2-4 , the actuator 114 extends through one or more gaskets 150 in the actuator end cap 104, through an aperture 152 in the first collar 106, and partially into the flexible structure 134. In one or more examples, the actuator 114 threads a thrust assembly including the thrust collar 154 into an extension coupling 156 secured to the first mounting plate 126.

[0023] With continued reference to Figures 2-4, multiple distinct volumes are defined within enclosure 102. With particular reference to Figures 3 and 4, a first volume 158 is defined within actuator end cap 104 and inside flexible structure 134. (Multiple reference numerals 158 appear in Figures 3 and 4 to indicate the extent of first volume 158.)

[0024] A second volume 160 is defined within the enclosure 102. (Again, multiple reference numerals 158 appear in FIGS. 3 and 4 to indicate the extent of the second volume 160.) As shown in FIGS. 3 and 4 , the second volume 160 is defined outside the flexible structure 134, within the electrically insulating intermediate element 110, within the second collar 108, between the first capacitor plate 122 and the second capacitor plate 128, and inside the second flexible structure 140. In the example, the second volume 160 extends into the second flexible structure 140 due to the presence of an aperture 162 in the second mounting plate 132. A third volume 164 may be defined between the outside of the second flexible structure 140 and the downwardly extended housing 112.

[0025] In the example, first volume 158 may be at or near external atmospheric pressure, potentially due to a nominal seal between actuator 114 and gasket 150 as the actuator enters actuator end cap 104, while second volume 160 is hermetically sealed (i.e., vacuum and liquid tight) due to the sealed attachment, e.g., by brazing, of flexible structure 134 to first collar 106 and first mounting plate 126, and again due to the fixed attachment, e.g., also by brazing, of second flexible structure 140 to second mounting plate 132. Third volume 164 may be at or near atmospheric pressure or vacuum, depending on the construction method.

[0026] According to one or more examples, second volume 160 may be filled with a liquid dielectric that acts as a dielectric material between first capacitor plate 122 and second capacitor plate 128. In examples, a pinch port 166 may be provided to introduce the fluid dielectric into second volume 160. Pinch port 166 may then be retracted closed to hermetically seal second volume 160. In examples, the fluid dielectric may be a fluid with high dielectric breakdown characteristics, i.e., a fluid with a dielectric constant of 1 (1.0) or greater, such as fluids used in high-voltage transformers, etc. In one example, the fluid dielectric may be Xiameter® PMX-200 Silicone Fluid, available from Dow Chemical Company. Also, in examples, the fluid dielectric provides better thermal conductivity than other dielectric materials, such as the vacuum in a vacuum capacitor.

[0027] According to the present example, the interdigitated overlap of first capacitor plate 122 and second capacitor plate 128 can be adjusted through rotation of actuator 114. Rotation of actuator 114, for example by a stepper motor or servo motor (not shown), causes threaded actuator 114 to raise or lower thrust collar 154 and extension coupling 156, thereby raising or lowering first mounting plate 126 relative to second mounting plate 132. That is, in these examples, first mounting plate 126, which carries first capacitor plate assembly 118, is movable relative to second mounting plate 132, which carries second capacitor plate assembly 120.

[0028] 3 and 4, Figure 3 shows the liquid dielectric variable capacitor in a first operating configuration. In the first operating configuration, the thrust collar 154 and extension coupling 156 are advanced to their maximum extent within the enclosure 102 so as to maximize the interdigitated overlap between the first capacitor plate 122 and the second capacitor plate 128. Because the interdigitated overlap is maximized, this maximizes the capacitance between the first capacitor plate 122 and the second capacitor plate 128.

[0029] In an example, the first mounting plate 126, flexible structure 134, extension coupling 156, thrust collar 154, and mounting plate 116 are electrically conductive (e.g., metallic) and provide a low resistance conductive path between the first electrode 124, the first collar 106, and the mounting plate 116. This may serve as a first external electrical contact for the liquid dielectric variable capacitor 100. The second electrode 130 is coupled to a second mounting plate, which may be integrated with (or electrically coupled to) the second collar, thereby allowing the second collar to serve as a second electrical connection for the liquid dielectric variable capacitor 100. In an example, an electrode plate (not shown) may be attached to the bottom of the second collar 108 to serve as an electrode for the liquid dielectric variable capacitor 100. A threaded socket 170 may be provided on the second collar 108 to facilitate attachment of the electrode plate.

[0030] In an example, when actuator 114 is rotated in a first direction to advance thrust collar 154, extension coupling 156, and first mounting plate 126 toward second mounting plate 132, this advancement effectively decreases the volume of second volume 160. To accommodate this volume decrease, second flexible structure 140 may expand (as shown in FIG. 3 ) and act as a reservoir for the displaced liquid dielectric. Meanwhile, actuator 114 may alternatively be rotated in an opposite second direction to retract thrust collar 154, extension coupling 156, and first mounting plate 126 away from second mounting plate 132. This retraction effectively increases the volume of second volume 160, thereby contracting second flexible structure 140 so that any liquid dielectric present within second flexible structure 140 may be maintained throughout volume 160.

[0031] One or more liquid dielectric variable capacitors, such as the example liquid dielectric variable capacitor 100 of Figures 1-5 herein, can be utilized to tune and control a matching network of a radio frequency plasma processing device. Broadly, radio frequency (RF) plasma-enhanced processes are used in semiconductor manufacturing to etch different types of films, deposit thin films at low to medium processing temperatures, and perform surface treatment and cleaning. One feature of such processes is the use of plasma, i.e., partially ionized gases, which are used to generate neutral species and ions from precursors in a reaction chamber, provide energy for ion bombardment, and / or perform other functions. Radio frequency plasma-enhanced processes are performed by what are known as radio frequency processing devices.

[0032] The RF processing device may include a RF generator that transmits a signal to the plasma reaction chamber. A RF matching device, which may have a variable impedance, may be disposed between the RF generator and the plasma reaction chamber. The RF matching device may be controlled or adjusted by changing the impedance of the RF matching device. Adjusting the RF matching device may reduce power reflection from the plasma reaction chamber and / or the RF matching device, thereby increasing the power delivered from the RF generator to the plasma reaction chamber for plasma processing. During operation, the RF generator may be energized to form a plasma in the reaction chamber. The plasma may be generated after a source gas is injected into the reaction chamber and power is delivered into the reaction chamber by the RF generator.

[0033] Under certain conditions, the power supplied to the reaction chamber may be reflected from the reaction chamber. One cause of power reflection may be a mismatch between the characteristic impedance of the system and the load created by the plasma in the reaction chamber. To help prevent power reflection, a matching network may be disposed between the radio frequency generator and the reaction chamber. Such a matching network may include multiple variable capacitors or other impedance elements. The variable capacitors may be adjusted so that the combined load impedance in the reaction chamber matches the impedance of the radio frequency generator.

[0034] While several methods for controlling or adjusting a matching network have been used, such methods may not provide reliable and effective results in impedance matching. The matching network may include a stepper motor, which has a specific number of steps that are a function of the specific stepper motor. During operation, the capacitor may be driven by the motor, which has a range between 0 and 100 percent, and as a result, the motor may have multiple clicks. Embodiments of the present disclosure may provide and / or enable a method for adjusting the capacitor position based, at least in part, on a "steps to percentage ratio."

[0035] Turning to FIG. 6, a schematic diagram of a matching network including a liquid dielectric variable capacitor is shown in accordance with one or more examples. In the example of FIG. 6, matching network 600 is shown having a matching branch 602 and a splitter branch 604. Matching branch 602 receives radio frequency (RF) power from a radio frequency (RF) input 606. A first variable capacitor 608 in matching branch 602 receives RF power from RF input 606. First variable capacitor 608 may be, for example, a liquid dielectric variable capacitor disclosed herein with reference to FIGS. 1-5 and may be estimated to be approximately 10-2000 pF.

[0036] 6, a first variable capacitor 608 is connected to a second capacitor 610 connected to ground. The second capacitor 610 is connected to a third variable capacitor 612. The third variable capacitor 612 may be, for example, a liquid dielectric variable capacitor as disclosed herein with reference to FIGS. 1-5 and may be estimated to be approximately 10-2000 pF. The third variable capacitor 612 is connected to an inductor 614, which is further connected to the splitter branch 604.

[0037] The splitter branch 604 receives RF power from the matching branch 602 and splits the received RF power between a fourth variable capacitor 616 and a fifth variable capacitor 618. Additionally, the fourth variable capacitor 616 and the fifth variable capacitor 618 may be liquid dielectric variable capacitors as disclosed herein with reference to Figures 1-5 and may be estimated to be approximately 10-2000 pF.

[0038] The fifth variable capacitor 618 is connected to the inner coil 620. One or more sensors 622 may be disposed between the fifth variable capacitor 618 and the inner coil 620. The sensor 622 may be used, for example, to measure the voltage between the fifth variable capacitor 618 and ground. Similarly, the fourth variable capacitor 616 is connected to the outer coil 624. One or more sensors 626 may be disposed between the fourth variable capacitor 616 and the outer coil 624. The sensor 626 may be used, for example, to measure the voltage between the fourth variable capacitor 616 and ground.

[0039] The inner coil 620 may further be connected to ground, and the outer coil 624 may be connected to a circuit including a sensor 628 and a sixth capacitor 630. The sensor 628 may be used, for example, to measure the voltage between the outer coil 624 and ground. The inner coil 620 and the outer coil 624 may be located outside the circuit of the matching network 600, as indicated by the dashed line 632 in FIG. 6 .

[0040] 6 may be used to adjust the first variable capacitor 608, the third variable capacitor 612, the fourth variable capacitor 616, and the fifth variable capacitor 618. By adjusting the first variable capacitor 608, the third variable capacitor 612, the fourth variable capacitor 616, and the fifth variable capacitor 618, the power supplied to the inner coil 620 and the outer coil 624 may be adjusted.

[0041] The above circuitry may be used as a current division ratio matching network in matching network 200 in one embodiment and may be controlled using a programmable logic controller (not shown) that may be located in or connected to matching network 600.

[0042] 2-5, and particularly FIG. 5, the example shown therein incorporates a first capacitor plate 122 and a second capacitor plate 128, each comprising a wound concentric cylindrical coil capacitor plate, where the first capacitor plate 122 is electrically attached at a top end to a first electrode 124 configured as a cylindrical coil, and the second capacitor plate 128 is electrically attached at a bottom end to a second electrode 130 configured as a cylindrical coil, although it should be contemplated that other examples may incorporate capacitor structures having different geometries.

[0043] For example, Figure 7 is an exploded perspective view of a capacitor assembly 700 according to one or more alternative examples. The example of Figure 7 includes a first capacitor plate assembly 718 and a second capacitor plate assembly. The first capacitor plate assembly 718 includes a wound concentric cylindrical coil capacitor plate 722 and a first electrode 724. The second capacitor plate assembly 720 includes a wound concentric spiral capacitor plate 728 and a second electrode 730. Similar to capacitor plate assemblies 118 and 120 of the examples of Figures 1-5, capacitor plate assemblies 718 and 720 of the example of Figure 7 are movable relative to each other (e.g., it may be the case that capacitor plate assembly 718 is movable relative to capacitor plate assembly 720, thereby providing variability in capacitance).

[0044] 7, the height of capacitor plate 728 varies as a function of radius. This may allow the capacitance versus position curve achieved through moving capacitor plate assembly 718 relative to capacitor plate assembly 720 to deviate from a linear function and begin to approximate a power function. This, in turn, may change the impedance versus position curve achieved by assembly 700 from a power function to a linear function. In another example, not shown, the capacitor assembly may have a sinusoidal cross section.

[0045] In the above description, for purposes of explanation, specific nomenclature is used to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that specific details are not required to practice the systems and methods described herein. The above descriptions of specific examples are presented for purposes of illustration and description. The examples herein are not intended to be exhaustive or to limit the disclosure to the precise forms described. Many modifications and variations are possible in light of the above teachings. The examples are shown and described to best explain the principles and practical application of the present disclosure, and to thereby enable one skilled in the art to best utilize the disclosure and various examples, with numerous modifications appropriate to the particular uses contemplated. It is intended that the scope of the present disclosure be defined by the following claims and their equivalents.

Claims

1. A variable capacitor, wherein the variable capacitor is An enclosure having an interior part, A movable capacitor plate assembly disposed within the internal portion of the enclosure, the movable capacitor plate assembly comprising a first capacitor plate, a first electrode, and a first mounting plate, A first flexible structure having a first end sealed around the opening to the internal portion of the enclosure, and a second end sealed to the rear side of the first mounting plate, A fixed capacitor plate assembly positioned proximal to the movable capacitor plate assembly, wherein the fixed capacitor plate assembly comprises a second capacitor plate, a second electrode, and a second mounting plate. The actuator coupling assembly coupled to the rear side of the first mounting plate, An actuator having a longitudinal axis extending toward the opening and through the first flexible structure, wherein the distal end of the actuator engages with the actuator coupling assembly, and the actuator is for moving the movable capacitor plate assembly forward and backward relative to the fixed capacitor plate assembly, A second flexible structure, which is located on the rear side of the second mounting plate and seals around the aperture within the second mounting plate, A liquid dielectric is sealed within the volume portion of the enclosure which is outside the first flexible structure and inside the second flexible structure, and the liquid dielectric acts as a dielectric between the first capacitor plate and the second capacitor plate. Moving the movable capacitor plate assembly forward toward the fixed capacitor plate assembly displaces the volume portion of the liquid dielectric through the aperture in the second mounting plate into the second flexible structure, and expands the second flexible structure, and A variable capacitor in which retracting the movable capacitor plate assembly away from the fixed capacitor plate assembly draws the volume portion of the liquid dielectric out of the second flexible structure and reduces the size of the second flexible structure.

2. The variable capacitor according to claim 1, wherein the actuator is provided with threads for engaging the actuator coupling assembly, and rotating the actuator in a first direction advances the movable capacitor plate assembly toward the fixed capacitor plate assembly and expands the first flexible structure, and rotating the screw-type actuator in a second direction retracts the movable capacitor plate assembly away from the fixed capacitor plate assembly and reduces the first flexible structure.

3. The variable capacitor according to claim 1, wherein the first flexible structure and the second flexible structure are bellows structures.

4. The variable capacitor according to claim 1, wherein the first capacitor plate and the second capacitor plate each have a wound cylindrical coil, and the first capacitor plate and the second capacitor plate are mated to each other.

5. The variable capacitor according to claim 1, wherein the first capacitor plate comprises a wound cylindrical coil, and the second capacitor plate comprises a wound helical coil, and the first capacitor plate and the second capacitor plate are mated to each other.

6. The variable capacitor according to claim 4, wherein moving the movable capacitor plate assembly forward and backward changes the range of overlapping mating between the first capacitor plate and the second capacitor plate, thereby changing the capacitance of the variable capacitor.

7. The variable capacitor according to claim 3, wherein the enclosure includes a first conductive collar that is in electrical contact with the movable capacitor plate assembly, a second conductive collar that is in electrical contact with the fixed capacitor plate assembly, and an electrically insulating intermediate element that separates the first conductive collar and the second conductive collar.

8. The variable capacitor according to claim 7, wherein the first flexible structure provides a conductive connection between the movable capacitor plate assembly and the first conductive collar.

9. A method for adjusting the capacitance of a variable capacitor, wherein the method is: To provide an enclosure having an interior part, To provide a movable capacitor plate assembly disposed within the internal portion of the enclosure, wherein the movable capacitor plate assembly comprises a first capacitor plate, a first electrode, and a first mounting plate. To provide a first flexible structure having a first end sealed around the opening to the internal portion of the enclosure, and a second end sealed to the rear side of the first mounting plate, To provide a fixed capacitor plate assembly positioned proximal to the movable capacitor plate assembly, wherein the fixed capacitor plate assembly comprises a second capacitor plate, a second electrode, and a second mounting plate. To provide an actuator coupling assembly coupled to the rear side portion of the first mounting plate, To provide an actuator having a longitudinal axis extending into the opening and through the first flexible structure, wherein the distal end of the actuator engages with the actuator coupling assembly, and the actuator is for moving the movable capacitor plate assembly forward and backward relative to the fixed capacitor plate assembly. To provide a second flexible structure, which is located on the rear side of the second mounting plate and seals around the aperture within the second mounting plate, To provide a liquid dielectric, which is sealed within the volume portion of the enclosure that is outside the first flexible structure and inside the second flexible structure, and which acts as a dielectric between the first capacitor plate and the second capacitor plate. The movable capacitor plate assembly is advanced toward the fixed capacitor plate assembly to increase the capacitance of the variable capacitor, wherein the advancement of the movable capacitor plate assembly causes the volume portion of the liquid dielectric to pass through the aperture in the second mounting plate into the second flexible structure, and expands the second flexible structure. A method comprising retracting the movable capacitor plate assembly away from the fixed capacitor plate assembly in order to reduce the capacitance of the variable capacitor, wherein retracting the movable capacitor plate assembly draws the volume portion of the liquid dielectric out of the second flexible structure and reduces the second flexible structure.

10. The method according to claim 9, wherein the actuator is provided with threads for engaging the actuator coupling assembly, and rotating the actuator in a first direction advances the movable capacitor plate assembly toward the fixed capacitor plate assembly and expands the first flexible structure, and rotating the screw-type actuator in a second direction retracts the movable capacitor plate assembly away from the fixed capacitor plate assembly and reduces the first flexible structure.

11. The method according to claim 9, wherein the first flexible structure and the second flexible structure are bellows structures.

12. The method according to claim 9, wherein the first capacitor plate and the second capacitor plate each have a cylindrical coil, and the first capacitor plate and the second capacitor plate are fitted together.

13. The method according to claim 9, wherein the first capacitor plate comprises a wound cylindrical coil, and the second capacitor plate comprises a wound helical coil, and the first capacitor plate and the second capacitor plate are fitted together.

14. The method according to claim 12, wherein moving the movable capacitor plate assembly forward and backward changes the range of overlapping mating between the first capacitor plate and the second capacitor plate, thereby changing the capacitance of the variable capacitor.

15. The method according to claim 11, wherein the enclosure includes a first conductive collar that is in electrical contact with the movable capacitor plate assembly, a second conductive collar that is in electrical contact with the fixed capacitor plate assembly, and an electrically insulating intermediate element that separates the first conductive collar and the second conductive collar.

16. The method according to claim 15, wherein the first flexible structure provides a conductive connection between the movable capacitor plate assembly and the first conductive collar.

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