Inductor assembly, impedance matching network, and system including inductor assembly

Abstract

The present disclosure relates to an inductor assembly, an impedance matching network, and a system including the inductor assembly. An inductor assembly (100) includes: a fixed element (102) having a central core (104) and a support structure (106) coupled to and projecting outwardly from the central core, each of the support structures having an outer edge (108) having a notched profile with a recess (110) extending toward the central core; and a spiral inductor (112) having a plurality of turns located in the recesses of the at least two support structures. The support structures are spaced equidistantly from each other around the central core by air gaps (308). The inductor assembly can be incorporated into an impedance matching network (1100), and one or more impedance matching networks can be incorporated into a defrost system (100). The impedance matching network can be a single-ended network (1100) or a double-ended network (1300).

Description

Technical Field

[0001] The present invention relates generally to inductors and, more particularly, to an inductor assembly for use in an impedance matching network and a system for defrosting a load including the inductor assembly. Background Art

[0002] Conventional capacitive food defrosting (or thawing) systems include large, planar electrodes housed within a heating compartment. A food load is placed between the electrodes, making contact with them. Low-power electromagnetic energy is then supplied to the electrodes to gently heat the food load. As the food load thaws during defrosting, its impedance changes. Consequently, the power delivered to the food load also changes during the defrost operation. The duration of the defrost operation can be determined, for example, based on the weight of the food load, and a timer can be used to control the cessation of the operation.

[0003] Although good defrosting results can be obtained using such systems, the dynamic changes in the food load impedance may result in inefficient defrosting. Therefore, the defrost system may implement a matching network to enable impedance matching between the radio frequency (RF) signal source of the defrost system and the cavity plus the load impedance. Air-core inductors are widely used as part of such impedance matching networks due to their high inductance capabilities with low losses (e.g., high Q characteristics), and the impedance matching network is very sensitive to the inductance of these air-core inductors. For example, small inductance changes may introduce large differences in the matching circuit. Air-core inductors can be formed as a spiral constructed using copper wire or copper tape coated with silver. The inductance is determined by its radius, wire diameter, number of turns, and the gap or spacing between the turns. Unfortunately, relatively large and heavy air-core inductors may have poor inductance consistency and poor vibration resistance because they are typically mounted to a substrate (e.g., a printed circuit board) at two solder points. Summary of the Invention

[0004] Various aspects of the disclosure are defined in the following claims.

[0005] In a first aspect, an inductor assembly is provided, comprising: a fixed element comprising a central core and support structures coupled to and protruding outward from the central core, each of the support structures having an outer edge with a recessed notch profile extending toward the central core; and a spiral inductor having a plurality of turns, the turns being located in the recesses of the at least two support structures.

[0006] In a second aspect, an impedance matching network is provided, comprising a first input node, a first output node, and a first variable component and a first inductor assembly, the first variable component and the first inductor assembly being coupled in series between the first input node and the first output node, the value of the first variable component being adjustable to affect the impedance transformation provided by the impedance matching network. The first inductor assembly comprises: a fixed element comprising a central core and a support structure coupled to and projecting outwardly from the central core, each of the support structures having an outer edge with a recessed notch profile extending toward the central core; and a spiral inductor having a plurality of turns located in the recess of the support structure, the spiral inductor having an input coupled to the output of the first variable component and an output coupled to the first output node.

[0007] In a third aspect, a heat addition system coupled to a cavity configured to accommodate a load is provided, the heat addition system comprising: a radio frequency (RF) signal source configured to supply an RF signal; a transmission path electrically coupled between the RF signal source and first and second electrodes positioned at opposite ends of the cavity; and an impedance matching network electrically coupled along the transmission path. The impedance matching network comprises: a first input node; a first output node; and a first variable component and a first inductor assembly, the first variable component and the first inductor assembly being coupled in series between the first input node and the first output node, the value of the first variable component being adjustable to affect the impedance transformation provided by the impedance matching network. The first inductor assembly includes: a fixed element, the fixed element including a central core and a support structure, the support structure coupled to the central core and protruding outward from the central core, each of the support structures having an outer edge, the outer edge having a recessed notch profile extending toward the central core; and a spiral inductor, the spiral inductor having a plurality of turns, the turns being located in the recess of the support structure, the input end of the spiral inductor being coupled to the output of the first variable component, and the output end being coupled to the first output node. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings are used to further illustrate various embodiments and to explain various principles and advantages of the present invention. In the individual views of the drawings, like reference numerals refer to identical or functionally similar elements. The drawings are not necessarily drawn to scale. The drawings, together with the following detailed description, are incorporated into and form a part of this specification.

[0009] Figure 1shows a side view of an inductor assembly according to an embodiment;

[0010] Figure 2A shows a perspective view of a spiral inductor;

[0011] Figure 2B shows a side view of a spiral inductor;

[0012] Figure 2C An end view of a spiral inductor is shown;

[0013] Figure 3A shows a perspective view of a fixing element of an inductor assembly according to an example embodiment;

[0014] Figure 3B Shown Figure 3A an end view of a fixing element;

[0015] Figure 3C Shown Figure 3A A side view of a fixing element;

[0016] Figure 4 Shown include Figure 1 a plate assembly of an inductor assembly;

[0017] Figure 5 shows a side view of a solid cylindrical fixing element according to an example embodiment;

[0018] Figure 6A shows a perspective view of a fixing element according to another example embodiment;

[0019] Figure 6B Shown Figure 6A A side view of a fixing element;

[0020] Figure 7A shows a perspective view of a fixing element according to another example embodiment;

[0021] Figure 7B Shown Figure 7A an end view of a fixing element;

[0022] Figure 8 shows a perspective view of a defroster appliance according to an example embodiment;

[0023] Figure 9 shows a perspective view of a refrigerator / freezer appliance including another example embodiment of a defrost system;

[0024] Figure 10 shows a simplified block diagram of an unbalanced defrost system according to an example;

[0025] Figure 11shows a schematic diagram of a single-ended variable capacitance matching network according to an example;

[0026] Figure 12 shows a simplified block diagram of a balanced defrost system according to an example; and

[0027] Figure 13 A schematic diagram of a two-terminal variable impedance network with a variable capacitor according to another example is shown. DETAILED DESCRIPTION

[0028] In general, the present disclosure relates to an inductor assembly, an impedance matching network including the inductor assembly, and a system including at least one impedance matching network and at least one inductor assembly. The system can be a defrost (or thawing) system that implements one or more impedance matching networks. The inductor assembly includes a fixing element that supports a spiral inductor having multiple turns. The fixing element includes multiple support structures surrounding a central core, and each support structure includes an outer edge with a recessed notch profile. The turns of the spiral inductor are located in the recesses of the support structures. The recesses in the support structures extend evenly along the support structures to ensure that the gap between each turn of the spiral inductor is uniform. In addition, the fixing element retains all the turns of the spiral inductor so that the turns cannot deviate freely, and the fixing element can be directly attached to a substrate, such as a printed circuit board (PCB). Therefore, the fixing element can ensure the consistency of the inductance of the spiral inductor and can also provide a firm support for the spiral inductor to enable good anti-vibration performance.

[0029] The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the words "exemplary" and "example" mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" or example is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, the present invention is not intended to be bound by any expressed or implied theory presented in the preceding technical field, background, or the following detailed description.

[0030] Embodiments of the subject matter described herein relate to solid-state defrost devices that can be incorporated into stand-alone appliances or other systems. As described in more detail below, embodiments of solid-state defrost devices include both "unbalanced" defrost devices and "balanced" devices. For example, an exemplary "unbalanced" defrost system is implemented using: a first electrode disposed in a cavity; a single-ended amplifier arrangement (including one or more transistors); a single-ended impedance matching network coupled between the output of the amplifier arrangement and the first electrode; and a measurement and control system that can detect when the defrost operation is complete. In contrast, an exemplary "balanced" defrost system is implemented using: a first electrode and a second electrode disposed in the cavity; a single-ended or double-ended amplifier arrangement (including one or more transistors); a double-ended impedance matching network coupled between the output of the amplifier arrangement and the first electrode and the second electrode; and a measurement and control system that can detect when the defrost operation is complete. In various embodiments, the impedance matching network includes a variable impedance matching network that can be adjusted during the defrost operation to improve the match between the amplifier arrangement and the cavity.

[0031] Generally, the term "defrost" means raising the temperature of a frozen load (e.g., a food load or other type of load) to a temperature at which the load is no longer frozen (e.g., a temperature at or near 0 degrees Celsius). As used herein, the term "defrost" more broadly refers to a process in which the heat energy or temperature of a load (e.g., a food load or other type of load) is increased by providing RF power to the load. Thus, in various embodiments, a "defrost operation" can be performed on the load at any initial temperature (e.g., any initial temperature above or below 0 degrees Celsius), and the defrost operation can be stopped at any final temperature above the initial temperature (e.g., including a final temperature above or below 0 degrees Celsius). That is, the "defrost operation" and "defrost system" described herein may alternatively be referred to as a "heat increase operation" and "heat increase system." The term "defrost" should not be interpreted as limiting the application of the present invention to methods or systems that can only raise the temperature of a frozen load to a temperature at or near 0 degrees Celsius.

[0032] It should be understood that the use of relational terminology (if any, such as first and second, top and bottom, etc.) is solely used to distinguish entities or actions from one another and does not necessarily require or imply any actual relationship or order between such entities or actions. Additionally, any connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and / or physical couplings between the various elements.

[0033] Figure 1A side view of an inductor assembly 100 according to an embodiment is shown. The inductor assembly 100 includes a fixed element 102 having a central core 104 and a support structure 106 coupled to and protruding outward from the central core 104. Each of the support structures 106 has an outer edge 108 with a notched profile of a recess 110 extending toward the central core 104. The inductor assembly 100 further includes a spiral inductor 112 having a plurality of turns 114, wherein the turns 114 are located in the recess 110 of the support structure 106.

[0034] Now refer to Figure 2A 、 2B and 2C, Figure 2A shows a perspective view of the spiral inductor 112, Figure 2B A side view of spiral inductor 112 is shown, and Figure 2C An end view of spiral inductor 112 is shown. Typically, spiral inductor 112 is an air-core coil that does not use a core made of ferromagnetic material. Spiral inductor 112 can be formed as a spiral made of, for example, copper wire or silver-coated copper tape. The inductance of spiral inductor 112 is determined by its radius 200R, wire diameter 202W, spacing 204S between turns 114, and the number of turns 114.

[0035] The mechanism used to manufacture spiral inductors, such as spiral inductor 112, can effectively produce spiral inductors having the same radius 200 and wire diameter 202. However, due to the flexibility of the conductive material used to produce the spiral inductor, the manufacturing mechanism may not produce a consistent spacing width 204 between each of the turns in turns 114. This situation may cause the inductance in the spiral inductor to vary. In addition, a side effect that may occur in air-core coils is that mechanical vibration of the turns 114 during operation may cause the inductance to vary. As will be discussed in detail below, the problems associated with the inductance variation in the spiral inductor 112 can be alleviated by supporting the spiral inductor 112 on the fixed element 102.

[0036] Now refer to Figure 3A 、 3B and 3C, Figure 3A An inductor assembly 100 ( Figure 1 ) is a perspective view of the fixing element 102, Figure 3B An end view of the fixing element 102 is shown, and Figure 3C A side view of the fixing element 102 is shown. Figures 3A-3CIn the example shown in FIG. 1 , the fixed element 102 includes a total of four support structures 106. Specifically, the fixed element 102 includes a first support structure 300, a second support structure 302, a third support structure 304, and a fourth support structure 306 that are equally spaced apart from one another around the central core 104. In addition, the first support structure 300, the second support structure 302, the third support structure 304, and the fourth support structure 306 are spaced apart from one another around the central core 104 by air gaps 308.

[0037] First support structure 300 includes a first group 310 of recesses 110 extending toward center core 104. Second support structure 302 includes a second group 312 of recesses 110 extending toward center core 104. Third support structure 304 includes a third group 314 of recesses 110 extending toward center core 104. Fourth support structure 306 includes a fourth group 316 of recesses 110 extending toward center core 104. Generally, each recess in the first group 310, second group 312, third group 314, and fourth group 316 of recesses 110 exhibits a first width, referred to herein as a recess width 318 (see FIG. 1 ). Figure 3C ), parallel to the longitudinal dimension 320 of the fixed element 102. For each groove in the groove 110, the groove width 318 is generally the same and corresponds to the turns 14 ( Figure 2C ) is a cross-sectional width of one turn of the wire, such as the wire diameter 202 ( FIG. 2 ). Additionally, the recesses 110 for each of the first group 310 , the second group 312 , the third group 314 , and the fourth group 316 are spaced apart from each other by a spacing 322 . For each of the spacings 322 , the spacings 322 exhibit a generally identical spacing width 324 . Thus, when the spiral inductor 112 ( Figure 1 ) resides in the recess 110, the spacing width 204 (FIG. 2) between the individual turns 114 of the spiral inductor 112 remains consistent to thereby reduce inductance variations.

[0038] exist Figure 3C As can be particularly observed in FIG, the recesses 110 in the first group 310, the second group 312, the third group 314, and the fourth group 316 can be offset relative to each other in the longitudinal dimension 320 to accommodate the coil configuration of the spiral inductor 112. For example, the offset configuration can produce recesses 110 in the first group 310 that are directly opposite the spacing 322 of the third group 314. Figure 5 The fabrication of the fixation element 102 to achieve the offset configuration of the recess 110 is discussed in greater detail.

[0039] The central core 104 of the fixed element 102 exhibits a first length, such as a longitudinal dimension 320 in the present example, that is greater than a second length 326 of the support structure 106, such that a first end 328 and a second end 330 of the central core 104 extend longitudinally beyond corresponding ends 332, 334 of the support structure 106. The first end 328 and the second end 330 are configured to be attached to a substrate.

[0040] Figure 4 A board assembly 400 including the inductor assembly 100 is shown. The board assembly 400 includes a substrate, such as a printed circuit board 402 (PCB). A plurality of active and passive components can be coupled to the PCB 400. The active and passive components are represented by rectangles surrounding smaller rectangles and circles. The various components can be electrically connected via conductive traces (not shown) on the PCB 400. These active and passive components can be any of a variety of electronic structures required to implement the specific functions of the board assembly 400, such as resistors, capacitors, processing elements, etc.

[0041] In the example, the opening 402 extends through the PCB 400. The inductor assembly 100 is positioned in the opening 402, and the first end 328 and the second end 330 of the fixing element 102 are coupled to the PCB 400 using, for example, an adhesive, a fastener, or any other suitable method. One or more conductive traces formed in the PCB 400 can be formed to suitably electrically interconnect the spiral inductor 112 of the inductor assembly 100 to active components and / or passive components of the PCB 400. Thus, the fixing element 102 of the inductor assembly 100 can be used to provide a secure support for the spiral inductor 112 and provide a secure coupling of the spiral inductor 112 to the PCB 400 to produce effective anti-vibration performance during operation.

[0042] Figure 5 A side view of a solid cylindrical fixing element 500 according to an example embodiment is shown. To design fixing element 102 ( FIG. 3 ), example techniques can be used to create solid cylinder 502 with spiral grooves 504 cut into its surface to accommodate spiral inductor 112 ( FIG. 2 ). Additionally, mounting holes 506 can be formed at opposite ends of solid cylinder 202.

[0043] In some embodiments, the solid cylindrical fixing element 500 (and Figure 1The fixing element 102 in and other fixing elements described below) can be formed from a thermally stable material having a thermal stability greater than, for example, two hundred degrees Celsius. As used herein, a thermally stable material is a material that is capable of resisting irreversible changes in its physical structure at relatively high temperatures. A less commonly used term may be "thermostable plastic," which may refer to a thermosetting plastic that cannot be reshaped when heated. One example material may be polytetrafluoroethylene (PTFE), although other thermally stable materials may alternatively be used.

[0044] An inductor assembly comprising a solid cylindrical fixing element 500 (instead of fixing element 102) can be mounted to a PCB and can therefore effectively support a spiral inductor in some applications. However, since the thermally stable material completely fills the spacing between each turn of the spiral inductor's turns, the parasitic capacitance of the spiral inductor may be undesirably increased compared to an air-core inductor of the same size. Therefore, such fixing elements may result in a reduction in inductance relative to an air-core inductor. In addition, the self-resonant frequency of the spiral inductor may be lowered. Still further, the solid cylindrical fixing element 500 may be undesirably heavy and may consume an undesirably large amount of thermally stable material, thereby resulting in higher costs.

[0045] To overcome the issues with the solid cylindrical fixture element 500, material is effectively removed from a design such as the solid cylindrical fixture element 500 to form the fixture element 102 (FIG. 3) described above having the first support structure 302, the second support structure 304, the third support structure 306, and the fourth support structure 308 (FIG. 3). The absence of some thermoplastic material (relative to the fixture element 500) significantly reduces the weight of the fixture element 102 relative to the fixture element 500 and creates a parasitic capacitance similar to that of an air-core inductor because only four thinner support structures 302, 304, 306, 308 are involved to facilitate the increased parasitic capacitance. However, the four thinner support structures 302, 304, 306, 308 can still effectively support the spiral inductor 112.

[0046] Now refer to Figure 6A and 6B , Figure 6A shows a perspective view of a fixing element 600 according to another example embodiment, and Figure 6B A side view of the fixing element 600 is shown. Figure 6A and Figure 6BIn the example of FIG. 6 , the fixed element 600 includes a total of four support structures. Specifically, the fixed element 600 includes a first support structure 602, a second support structure 604, a third support structure 606, and a fourth support structure 608 that are equally spaced apart from each other around the central core 610. In addition, the first support structure 602, the second support structure 604, the third support structure 606, and the fourth support structure 608 are spaced apart from each other around the central core 610 by an air gap 612. Each of the first support structure 602, the second support structure 604, the third support structure 606, and the fourth support structure 608 includes a support structure configured to support the spiral inductor 112 ( Figures 2A-2C ) of the corresponding group of recesses 614 (combined with the above Figures 3A-3C similar to those described).

[0047] according to Figures 6A-6B In the illustrated embodiment, each of the first support structure 602, the second support structure 604, the third support structure 606, and the fourth support structure 608 includes one or more openings 616 extending therethrough. The fixing element 600 can effectively support the spiral inductor 112 ( Figure 1 ) and enables secure mounting to PCB 402 ( Figure 4 ), while further reducing relative to the fixed element 102 ( Figure 3A 、 Figure 3B 、 Figure 3C ) weight and material cost.

[0048] Figure 7A shows a perspective view of a fixing element 700 according to another example embodiment, and Figure 7B An end view of the fixing element 700 is shown. Figure 7A and Figure 7B In the example of FIG. 7 , the fixed element 700 includes a total of three support structures. Specifically, the fixed element 700 includes a first support structure 702, a second support structure 704, and a third support structure 706 that are equally spaced apart from each other around the central core 710. In addition, the first support structure 702, the second support structure 704, and the third support structure 706 are spaced apart from each other around the central core 710 by an air gap 712. Each of the first support structure 702, the second support structure 704, and the third support structure 706 includes a support structure configured to support the spiral inductor 112 ( Figures 2A-2C ) of the corresponding group of recesses 714 (combined with the above Figures 3A-3C similar to those described).

[0049] according to Figures 7A-7BIn the illustrated embodiment, each of the first support structure 702, the second support structure 704, and the third support structure 706 includes one or more openings 716 extending therethrough. The fixing element 700 may be constructed with only three support structures ( Figure 1 ) effectively supports the spiral inductor 112 and enables secure mounting to the PCB 402 ( Figure 4 ), while further reducing the weight and material costs relative to the fixing element 102, 600.

[0050] The preceding discussion addresses various embodiments of a mounting element for securely supporting an air-coil spiral inductor. Inductor assemblies comprising a mounting element and a spiral inductor can be incorporated into a variety of circuits and systems. According to the embodiments discussed below, one or more of the inductor assemblies are implemented in an impedance matching network for a heat-increasing system (e.g., a defrost system).

[0051] Figure 8 A perspective view of a defrost appliance 800 according to an example embodiment is shown. The defrost appliance 800 (alternatively referred to herein as a defrost system 800) includes a defrost chamber 802, a control panel 804, one or more radio frequency (RF) signal sources (not visible), a power supply (not visible), a first electrode 806, a second electrode 808, an impedance matching circuit system (not visible), a power detection circuit system (not visible), and a system controller (not visible). The defrost chamber 802 is defined by the inner surfaces of a top chamber wall 810, a bottom chamber wall 812, side chamber walls 814, 816, and a rear chamber wall 818, and the inner surface of a door 820. When the door 820 is closed, the defrost chamber 802 defines an enclosed air cavity. As used herein, the term "air cavity" can refer to an enclosed area that contains air or other gas (e.g., the defrost chamber 802).

[0052] According to the "unbalanced" configuration, the first electrode 806 is arranged close to a cavity wall (e.g., top wall 810), the first electrode 806 is electrically isolated from the remaining cavity walls (e.g., walls 812, 814, 816, 818 and door 820), and the remaining cavity walls are grounded. In such a configuration, the system can be simply modeled as a capacitor, where the first electrode 806 acts as one conductive plate (or electrode), the grounded cavity walls (e.g., walls 812, 814, 816, 818 and door 820) act as the second conductive plate (or electrode), and the air cavity (including any load contained therein) acts as the dielectric between the first and second conductive plates. Although not described in Figure 8 Although not shown in FIG, a non-conductive barrier may also be included in the defrost system 800 and may be used to electrically and physically isolate the load from the bottom wall 812. Figure 8The first electrode 806 is shown proximate to the top wall 812 , but alternatively, the first electrode 806 may be proximate to any of the other walls 812 , 814 , 816 , 818 , as shown by electrodes 822 , 824 , 826 , 828 .

[0053] According to the "balanced" configuration, the first electrode 806 is arranged near a first cavity wall (e.g., top wall 810), the second electrode 808 is arranged near an opposing second cavity wall (e.g., bottom wall 812), and the first electrode 806 and the second electrode 808 are electrically isolated from the remaining cavity walls (e.g., walls 814, 816, 818 and gate 820). In such a configuration, the system can also be simply modeled as a capacitor, where the first electrode 806 acts as one conductive plate (or electrode), the second electrode 808 acts as a second conductive plate (or electrode), and the air cavity (including any load contained therein) acts as a dielectric between the first and second conductive plates. Although not described in Figure 8 Although not shown in FIG, a non-conductive barrier may also be included in the defrost system 800 and may be used to electrically and physically isolate the load from the second electrode 808 and the bottom cavity wall 812. Figure 8 The first electrode 806 is shown as being near the top wall 810 and the second electrode 808 is shown as being near the bottom wall 812, but alternatively, the first electrode 806 and the second electrode 808 may be near other opposing walls (e.g., the first electrode may be electrode 824 near wall 816 and the second electrode may be electrode 826 near wall 814).

[0054] According to an example, during operation of the defrost system 800, a user (not shown) may place one or more loads (e.g., food and / or liquid) in the defrost chamber 802 and, optionally, may provide input specifying characteristics of the one or more loads via the control panel 804. For example, the specified characteristics may include the approximate weight of the load. Additionally, the specified load characteristics may indicate one or more materials forming the load (e.g., meat, bread, liquid). In alternative examples, the load characteristics may be obtained by some other means, such as by scanning a barcode on the load packaging or receiving a radio frequency identification (RFID) signal from an RFID tag on or embedded in the load. In either case, as will be described in greater detail later, information regarding such load characteristics enables the system controller to establish an initial state of the system's impedance matching network at the start of the defrost operation, wherein the initial state may be relatively close to an optimal state for achieving maximum RF power transfer to the load. Alternatively, the load characteristics may not be entered or received before the defrost operation begins, and the system controller may establish a default initial state for the impedance matching network.

[0055] To initiate a defrost operation, a user may provide input via the control panel 804. In response, the system controller causes one or more RF signal sources to supply an RF signal to the first electrode 806 in an unbalanced embodiment or to both the first electrode 806 and the second electrode 808 in a balanced embodiment, and the one or more electrodes accordingly radiate electromagnetic energy into the defrost chamber 802. The electromagnetic energy increases the thermal energy of the load (i.e., the electromagnetic energy causes the load to heat up).

[0056] During a defrost operation, the impedance of the load (and therefore the total input impedance of the defrost chamber 802 plus the load) changes as the thermal energy of the load increases. The impedance change changes the RF energy absorbed into the load and, therefore, changes the magnitude of the reflected power. According to an example, the power detection circuitry continuously or periodically measures the reflected power along the transmission path between the RF signal source and the one or more electrodes 806, 808. Based on these measurements, the system controller can detect the completion of the defrost operation, as will be described in detail below. According to another embodiment, the impedance matching network is variable, and based on the reflected power measurement results (or both the forward and reflected power measurement results), the system controller can change the state of the impedance matching network during the defrost operation to increase the absorption of the incident RF power by the load.

[0057] Figure 8 The defrost system 800 is embodied as a countertop appliance. In other configurations, the defrost system 800 may also include components and functions for performing microwave cooking operations. Alternatively, the components of the defrost system may be incorporated into other types of systems or appliances.

[0058] Figure 9 A perspective view of a refrigerator / freezer appliance 900 is shown that includes other example embodiments of defrost systems 902, 904. More specifically, defrost system 902 is shown as being incorporated into a freezer compartment 906 of appliance 900, and defrost system 904 is shown as being incorporated into a refrigerator compartment 908 of appliance 900. An actual refrigerator / freezer appliance will likely include only one of defrost systems 902, 904, but both are shown. Figure 9 The two embodiments are concisely conveyed in FIG.

[0059] Similar to the defrost system 800, each of the defrost systems 902, 904 includes a defrost chamber, a control panel 910, 912, one or more RF signal sources, a power supply, a first electrode, a second electrode, impedance matching circuitry, power detection circuitry, and a system controller (all of which are in Figure 9(not visible in the drawing). For example, the defrost cavity can be defined by the inner surfaces of the bottom, side, front, and rear walls of the drawer and the inner top surfaces of the fixed shelves 914 and 916 under which the drawer slides. When the drawer is fully slid under the shelves, the drawer and shelves define the cavity as a closed air cavity. In various embodiments, the components and functions of the defrost systems 902 and 904 can be substantially the same as those of the defrost system 800.

[0060] In addition, each defrost system in the defrost system 902, 904 can be sufficiently thermally connected to the freezer compartment 906 or the refrigerator compartment 908, respectively, with the system 902 being placed in the freezer compartment 906 and the system 904 being placed in the refrigerator compartment 908. In such embodiments, after the defrost operation is completed, the load can be maintained at a safe temperature (i.e., a temperature that delays food spoilage) until the load is removed from the system 902, 904. More specifically, when the defrost operation is completed by the defrost system 902 based on the freezer, the cavity that holds the defrost load can be thermally connected to the freezer appliance 906, and if the load is not removed from the cavity in time, the load can be re-frozen. Similarly, when the defrost operation is completed by the defrost system 904 based on the refrigerator, the cavity that holds the defrost load can be thermally connected to the refrigerator compartment 908, and if the load is not removed from the cavity in time, the load can be maintained in a defrosted state at a temperature within the refrigerator compartment 908.

[0061] Based on the description herein, those skilled in the art will appreciate that embodiments of the defrost system may also be incorporated into systems or appliances having other configurations. Thus, the above-described embodiments of the defrost system in stand-alone appliances, microwave appliances, freezers, and refrigerators are not intended to limit the use of the embodiments to only those types of systems.

[0062] While the defrost systems 800, 902, 904 are shown with their components particularly oriented relative to one another, it should be understood that the various components may be oriented differently. Furthermore, the physical configuration of the various components may be different. For example, the control panels 804, 910, 912 may have more, fewer, or different user interface elements, and / or the user interface elements may be arranged differently. Furthermore, while Figure 8 , the defrost chamber 802 is shown as being substantially cubic, but it should be understood that in other embodiments, the defrost chamber may have a different shape (e.g., cylindrical, etc.). Additionally, the defrost systems 800, 902, 904 may include Figure 8 and Figure 9 Additional components not specifically depicted (e.g., fans, fixed or rotating plates, trays, cords, etc.).

[0063] Figure 10 An unbalanced defrost system 1000 (eg, Figure 8 Defrost system 800, Figure 9 In one embodiment, the defrost system 1000 includes an RF subsystem 1002, a defrost chamber 1004, a user interface 1006, a system controller 1008, an RF signal source 1010, a power supply and bias circuitry 1012, a variable impedance matching network 1014, an electrode 1016, a containment structure 1018, and a power detection circuitry 1020. It should be understood that for purposes of explanation and ease of description, Figure 10 is a simplified representation of the defrost system 1000 , and actual embodiments may include other devices and components to provide additional functionality and features, and / or the defrost system 1000 may be part of a larger electrical system.

[0064] The user interface 1006 may correspond to a control panel (eg, Figure 8 Control panel 804, Figure 9 The user interface may include a control panel 910, 912 that enables a user to provide input to the system regarding parameters of the defrost operation (e.g., characteristics of the load to be defrosted, etc.), start and cancel buttons, mechanical controls (e.g., door / drawer latches), etc. In addition, the user interface may be configured to provide user-perceivable output indicating the status of the defrost operation (e.g., a countdown timer, visual indicia indicating progress or completion of the defrost operation, and / or an audible tone indicating completion of the defrost operation) and other information.

[0065] Some embodiments of the defrost system 1000 may include one or more temperature sensors, one or more IR sensors, and / or one or more weight sensors 1022. The one or more temperature sensors and / or one or more IR sensors may be positioned so that the temperature of the load 1024 can be sensed during the defrost operation. When provided to the system controller 1008, the temperature information enables the system controller 1008 to vary the power of the RF signal supplied by the RF signal source 1010 (e.g., by controlling the bias and / or supply voltage provided by the power and bias circuitry 1012) to adjust the state of the variable impedance matching network 1014 and / or determine when the defrost operation should be terminated. One or more weight sensors are positioned beneath the load 1024 and are configured to provide the system controller 1008 with an estimate of the weight of the load 1024. The system controller 1008 may use this information, for example, to determine a desired power level for the RF signal supplied by the RF signal source 1010, determine an initial setting for the variable impedance matching network 1014, and / or determine an approximate duration for the defrost operation.

[0066] In an example, the RF subsystem 1002 includes a system controller 1008, an RF signal source 1010, a first impedance matching circuit 1026 (referred to herein as the "first matching circuit"), power supply and bias circuitry 1012, and power detection circuitry 1020. The system controller 1008 may include one or more general-purpose or special-purpose processors (e.g., microprocessors, microcontrollers, application-specific integrated circuits (ASICs), etc.), volatile and / or non-volatile memory (e.g., random access memory (RAM), read-only memory (ROM), flash memory, various registers, etc.), one or more communication buses, and other components. According to an embodiment, the system controller 1008 is coupled to the user interface 1006, the RF signal source 1010, the variable impedance matching network 1014, the power detection circuitry 1020, and the sensor 1022 (if included). The system controller 1008 is configured to receive signals indicative of user input received via the user interface 1006 and to receive signals indicative of the RF signal reflected power (and possibly the RF signal forward power) from the power detection circuitry 1020. In response to the received signals and measurements, and as will be described in greater detail later, the system controller 1008 provides control signals to the power supply and bias circuitry 1012 and the RF signal generator 1028 of the RF signal source 1010. In addition, the system controller 1008 provides control signals to the variable impedance matching network 1014, which cause the network 1014 to change its state or configuration.

[0067] The defrost chamber 1004 includes a capacitive defrost arrangement having a first parallel plate electrode and a second parallel plate electrode separated by an air cavity within which a load 1024 to be defrosted may be placed. For example, the first electrode (e.g., electrode 1016) may be positioned above the air cavity, and the second electrode may be provided by a portion of the containment structure 1018. More specifically, the containment structure 1018 may include a bottom wall, a top wall, and side walls, the inner surfaces of the bottom wall, the top wall, and the side walls defining the defrost chamber 1004 (e.g., Figure 8 According to an embodiment, the defrost chamber 1004 may be sealed (e.g., with Figure 8 The door 820 or by sliding in Figure 9The system 1000 may include one or more interlocking mechanisms to ensure that the seal is intact during the defrost operation. If one or more of the interlocking mechanisms indicates that the seal is broken, the system controller 1008 may stop the defrost operation. According to an example, the containment structure 1018 is at least partially formed of a conductive material, and one or more conductive portions of the containment structure 1018 may be grounded. Alternatively, at least the portion of the containment structure 1018 corresponding to the bottom surface of the defrost chamber 1004 may be formed of a conductive material and grounded. In either case, the containment structure 1018 (or at least the portion of the containment structure 1018 parallel to the first electrode 1016) acts as the second electrode of the capacitive defrost arrangement. To avoid direct contact between the load 1024 and the grounded bottom surface of the defrost chamber 1004, a non-conductive barrier 1030 may be positioned above the bottom surface of the defrost chamber 1004.

[0068] Essentially, the defrost chamber 1004 includes a capacitive defrost arrangement having a first parallel plate electrode 1016 and a second parallel plate electrode 1018 (e.g., the portion of the containment structure 1018 parallel to the first electrode 1016) separated by an air cavity within which a load 1024 to be defrosted may be placed. In an example, the first electrode 1016 is positioned within the containment structure 1018 to define a distance 1032 between the electrode 1016 and an opposing surface of the containment structure 1018 (e.g., a bottom surface serving as the second electrode), wherein the distance 1032 renders the defrost chamber 1004 a sub-resonant cavity.

[0069] In various examples, distance 1032 is in the range of approximately 0.10 meters to approximately 1.0 meters, although distance 1032 can be smaller or larger. According to an example, distance 1032 can be less than one wavelength of the RF signal generated by RF subsystem 1002. In other words, as described above for defrosting, defrost chamber 1004 is a sub-resonant cavity. In some examples, distance 1032 can be less than approximately half a wavelength of the RF signal, distance 1032 can be less than approximately one-quarter a wavelength of the RF signal, distance 1032 can be less than approximately one-eighth a wavelength of the RF signal, distance 1032 can be less than approximately one-fiftieth a wavelength of the RF signal, or distance 1032 can be less than approximately one-hundredth a wavelength of the RF signal.

[0070] Typically, a defrost system 1000 designed for a lower operating frequency (e.g., a frequency between 10 MHz and 100 MHz) can be designed to have a distance 1032 that is a smaller fraction of a wavelength. For example, when the system 1000 is designed to generate an RF signal having an operating frequency of approximately 10 MHz (corresponding to a wavelength of approximately 30 meters) and the distance 1032 is selected to be approximately 0.5 meters, the distance 1032 is approximately one-sixtieth of a wavelength of the RF signal. Conversely, when the system 1000 is designed for an operating frequency of approximately 300 MHz (corresponding to a wavelength of approximately 1 meter) and the distance 1032 is selected to be approximately 0.5 meters, the distance 1032 is approximately half a wavelength of the RF signal.

[0071] When the operating frequency and distance 132 between the electrode 1016 and the containment structure 1018 are selected to define a sub-resonant inner defrost chamber 1004, the first electrode 1016 and the containment structure 1018 are capacitively coupled. More specifically, the first electrode 1016 can be analogized as the first plate of a capacitor, the containment structure 1018 can be analogized as the second plate of the capacitor, and the load 1024, the barrier 1030, and the air within the defrost chamber 1004 can be analogized as the capacitor dielectric. Therefore, the first electrode 1016 may alternatively be referred to herein as the "anode," and the containment structure 1018 may alternatively be referred to herein as the "cathode."

[0072] Essentially, the voltage across the first electrode 1016 and the containment structure 1018 heats the load 1024 within the defrost chamber 1004. According to various embodiments, the RF subsystem 1002 is configured to generate an RF signal to produce a voltage between the electrode 1016 and the containment structure 1018 in a range of approximately 90 volts to approximately 3,000 volts in one example, or in a range of approximately 3,000 volts to approximately 10,000 volts in another example, although the system can also be configured to produce lower or higher voltages between the electrode 1016 and the containment structure 1018.

[0073] In an example, the first electrode 1016 is electrically coupled to the RF signal source 1010 via a first matching circuit 1026, a variable impedance matching network 1014, and a conductive transmission path. The first matching circuit 1026 is configured to perform an impedance transformation from the impedance of the RF signal source 1010 (e.g., less than approximately 10 ohms) to an intermediate impedance (e.g., 50 ohms, 75 ohms, or some other value). According to an example, the conductive transmission path includes a plurality of conductors 1034-1, 1034-2, and 1034-3 connected in series and collectively referred to as a transmission path 1034. According to an example, the conductive transmission path 1034 is an "unbalanced" path configured to carry an unbalanced RF signal (i.e., a single RF signal referenced to ground). In some embodiments, one or more connectors (not shown, but each having a male connector portion and a female connector portion) can be electrically coupled along the transmission path 1034, and a portion of the transmission path 1034 between the connectors can include a coaxial cable or other suitable connector.

[0074] The variable impedance matching network 1014 is configured to perform an impedance transformation (e.g., on the order of several hundred or several thousand ohms, such as about 1000 ohms to about 4000 ohms or greater) from the aforementioned intermediate impedance to the input impedance of the defrost chamber 1004 as modified by the load 1024. The variable impedance matching network 1014 may include a network of passive components (e.g., inductors, capacitors, resistors).

[0075] The variable impedance matching network 1014 may include a plurality of variable capacitance networks (eg, Figure 11 ), the variable capacitance network can be located inside or outside the defrost chamber 1004. The capacitance value provided by each of the capacitance networks is established using a control signal from the system controller 1008. By changing the state of the variable impedance matching network 1014 during the defrost operation to dynamically match the changing chamber input impedance, the amount of RF power absorbed by the load 1024 can be maintained at a high level despite the changes in load impedance during the defrost operation.

[0076] RF signal source 1010 includes an RF signal generator 1028 and a power amplifier (e.g., including one or more power amplifier stages 1036 and 1038). In response to a control signal provided by system controller 1008 via connection 1040, RF signal generator 1028 is configured to generate an oscillating electrical signal with a frequency in the ISM (Industrial, Scientific, and Medical) band, although the system can also be modified to support operation in other frequency bands. In various embodiments, RF signal generator 1028 can be controlled to generate oscillating signals at different power levels and / or different frequencies. For example, RF signal generator 1028 can generate a signal oscillating in the range of approximately 10.0 megahertz (MHz) to approximately 100 MHz and / or approximately 100 MHz to approximately 3.0 gigahertz (GHz). Some desirable frequencies may be, for example, 13.56 MHz (+ / - 5%), 27.125 MHz (+ / - 5%), 40.68 MHz (+ / - 5%), and 2.45 GHz (+ / - 5%). In one specific example, the RF signal generator 1028 can generate a signal oscillating in the range of about 40.66 MHz to about 40.70 MHz and having a power level in the range of about 10 decibel-milliwatts (dBm) to about 15 dBm. Alternatively, the oscillation frequency and / or power level can be lower or higher.

[0077] exist Figure 10 In the example of FIG. 1 , the power amplifier includes a driver amplifier stage 1036 and a final amplifier stage 1038. The power amplifier is configured to receive an oscillating signal from the RF signal generator 1028 and amplify the signal to produce a significantly higher power signal at the output of the power amplifier. For example, the power level of the output signal can range from about 100 watts to about 400 watts or more. The gain applied by the power amplifier can be controlled using a gate bias voltage and / or a drain supply voltage provided to each amplifier stage 1036, 1038 by the power supply and bias circuitry 1012. More specifically, the power supply and bias circuitry 1012 provides bias voltages and supply voltages to each RF amplifier stage 1036, 1038 based on control signals received from the system controller 1008.

[0078] Each amplifier stage 1036, 1038 can be implemented as a power transistor, such as a field effect transistor (FET), having an input terminal (e.g., a gate or control terminal) and two current-carrying terminals (e.g., a source terminal and a drain terminal). An impedance matching circuit (not shown) can be coupled to the input (e.g., gate terminal) of the driver amplifier stage 1036, coupled between the driver amplifier stage 1036 and the final amplifier stage 1038, and / or coupled to the output (e.g., drain terminal) of the final amplifier stage 1038. Each transistor of the amplifier stages 1036, 1038 can include a laterally diffused metal oxide semiconductor FET (LDMOSFET) transistor. However, it should be noted that the transistors are not intended to be limited to any particular semiconductor technology, and in other embodiments, each transistor can be implemented as a gallium nitride (GaN) transistor, another type of MOSFET transistor, a bipolar junction transistor (BJT), or a transistor utilizing another semiconductor technology.

[0079] exist Figure 10 , the power amplifier arrangement is depicted as including two amplifier stages 1036, 1038 coupled to other circuit components in a particular manner. In other embodiments, the power amplifier arrangement can include other amplifier topologies and / or the amplifier arrangement can include only one amplifier stage or more than two amplifier stages. For example, the power amplifier arrangement can include various embodiments of a single-ended amplifier, a Doherty amplifier, a switch-mode power amplifier (SMPA), or another type of amplifier.

[0080] The defrost chamber 1004 and any load 1024 positioned therein (e.g., food, liquid, etc.) present a cumulative load to the electromagnetic energy (or RF power) radiated into the chamber 1004 via the first electrode 1016. More specifically, the defrost chamber 1004 and load 1024 present an impedance to the system, referred to herein as the "cavity input impedance." During defrost operation, the cavity input impedance changes as the temperature of the load 1024 increases. The cavity input impedance directly affects the magnitude of the reflected signal power along the conductive transmission path 1034 between the RF signal source 1010 and the electrode 1016. In most cases, it is desirable to maximize the amount of signal power delivered to the defrost chamber 1004 and / or minimize the ratio of reflected to forward signal power along the conductive transmission path 1034.

[0081] To at least partially match the output impedance of the RF signal generator 1028 to the cavity input impedance, a first matching circuit 1026 can be electrically coupled along the transmission path 1034. The first matching circuit 1026 can have any of a variety of configurations. According to an example, the first matching circuit 1026 includes fixed components (i.e., components with non-variable component values), but the first matching circuit 1026 can include one or more variable components. For example, the first matching circuit 1026 can include any one or more networks selected from the following: an inductor / capacitor (LC) network, a series inductor network, a parallel inductor network, or a combination of a bandpass circuit, a highpass circuit, and a lowpass circuit. Basically, the first impedance matching circuit 1026 is configured to raise the impedance to a level intermediate between the output impedance of the RF signal transmitter 1028 and the cavity input impedance.

[0082] The impedance of many types of food loads changes with respect to temperature in a somewhat predictable manner as the food load transitions from a frozen state to a defrosted state. Therefore, based on reflected power measurements (and in some examples forward power measurements) from the power detection circuitry 1020, the system controller 1008 is configured to identify a point during the defrost operation when the rate of change of the cavity input impedance indicates that the load 1024 is approaching 0 degrees Celsius, at which point the system controller 1008 can terminate the defrost operation.

[0083] According to an example, power detection circuitry 1020 can be coupled along transmission path 1034 between the output of RF signal source 1010 and electrode 1016. In a specific example, power detection circuitry 1020 forms part of RF subsystem 1002 and can be coupled to conductor 1034-2 between the output of first matching circuit 1026 and the input of variable impedance matching network 1014. Alternatively, power detection circuitry 1020 can be coupled to portion 1034-1 of transmission path 1034 between the output of RF signal source 1010 and the input of first matching circuit 1026 or to portion 1034-3 of transmission path 1034 between the output of variable impedance matching network 1014 and first electrode 1016.

[0084] Regardless of where coupled, the power detection circuitry 1020 is configured to monitor, measure, or otherwise detect the power of a reflected signal (i.e., a reflected RF signal traveling in a direction from the electrode 1016 to the RF signal source 1010) traveling along the transmission path 1034 between the RF signal source 1010 and the electrode 1016. The power detection circuitry 1020 is also configured to detect the power of a forward signal (i.e., a forward RF signal traveling in a direction from the RF signal source 1010 to the electrode 1016) traveling along the transmission path 1034 between the RF signal source 1010 and the electrode 1016. The power detection circuitry 1020 supplies a signal to the system controller 1008 via connection 1042 that communicates the magnitude of the reflected signal power (and, in some examples, the forward signal power) to the system controller 1008. When both the forward signal power magnitude and the reflected signal power magnitude are communicated, the system controller 1008 can calculate a reflected to forward signal power ratio, or an S11 parameter. When the reflected signal power magnitude exceeds a reflected signal power threshold or the reflected to forward signal power ratio exceeds an S11 parameter threshold, this indicates that the defrost system 100 is insufficiently matching the cavity input impedance and that energy absorption by the load 1024 within the defrost cavity 1004 may be suboptimal. In such a situation, the system controller 1008 can orchestrate a process for altering the state of the variable matching network 1014 to drive the reflected signal power or S11 parameter closer to or below a desired level (e.g., below a reflected signal power threshold and / or a reflected to forward signal power ratio threshold), thereby re-establishing an acceptable match and promoting better energy absorption by the load 10024.

[0085] More specifically, system controller 1008 may provide control signals to variable matching circuit 1014 via control path 1044, which cause variable matching circuit 1014 to change the inductance, capacitance, and / or resistance of one or more components within the circuit, thereby adjusting the impedance transformation provided by circuit 1014. Adjusting the configuration of variable matching circuit 1014 is expected to reduce the magnitude of the reflected signal power, which corresponds to reducing the magnitude of the S11 parameter and increasing the power absorbed by load 1024.

[0086] As discussed above, the variable impedance matching network 1014 is used to match the input impedance of the defrost chamber 1004 plus the load 1024 to maximize the RF power delivered to the load 1024 to the greatest extent possible. At the start of a defrost operation, the initial impedances of the defrost chamber 1004 and the load 1024 may not be precisely known. Furthermore, the impedance of the load 1024 changes during the defrost operation as the load 1024 heats up. Therefore, the system controller 1008 can provide a control signal to the variable impedance matching network 1014 that causes the state of the variable impedance matching network 1014 to be modified. This enables the system controller 1008 to establish an initial state of the variable impedance matching network 1014 at the start of a defrost operation, which has a relatively low reflected-to-forward power ratio and, therefore, a relatively high RF power absorbed by the load 1024. Furthermore, this enables the system controller 1008 to modify the state of the variable impedance matching network 1014 so that adequate matching can be maintained throughout the defrost operation despite the changing impedance of the load 1024.

[0087] The variable matching network 1014 can have any of a variety of configurations. In an embodiment, the variable matching network 1014 can include a single-ended network (e.g., Figure 11 100). The inductance, capacitance, and / or resistance values ​​provided by the variable matching network 1014 can be established using control signals from the system controller 1008, which in turn affect the impedance transformation provided by the network 1014. By changing the state of the variable matching network 1014 during the defrost operation to dynamically match the changing impedance of the defrost chamber 1004 plus the load 1024 within the chamber 1004, system efficiency can be maintained at a high level throughout the defrost operation.

[0088] Figure 11 A single-ended variable capacitance matching network 1100 (eg, Figure 10 The single-ended variable capacitance matching network 1110 is used as a variable impedance matching network and is therefore interchangeably referred to herein as a variable impedance matching network 1100. The single-ended variable impedance matching network 1100 may be used in a defrost system (e.g., Figure 8 Defrost system 800, Figure 9 Defrost system 902, 904, Figure 10 1000).

[0089] The variable impedance matching network 1100 includes an input node 1102 and an output node 1104. A variable component in the form of a first capacitor network 1106 and at least one inductor assembly 1108 are coupled in series between the input node 1102 and the output node 1104. The inductor assembly 1108 includes a fixed element 1110 (e.g., Figure 1 3, the fixing element 102, the fixing element 600, any one of the fixing element 700 of FIG. 7) and the spiral inductor 1112 supported by the fixing element 1110 (eg, Figure 1 2 ). Spiral inductor 1112 has an input 1114 coupled to the output of first variable impedance network 1106 and an output 1116 coupled to first output node 1104.

[0090] exist Figure 11 The fixed element 1110 and spiral inductor 1112 of the inductor assembly 1108 are shown in a highly simplified form in the schematic diagram of FIG. However, it should be understood that the fixed element 1110 includes a central core and a support structure, the support structure being coupled to and projecting outwardly from the central core, and the support structure having an outer edge with a recess extending toward the central core. In addition, the support structures are spaced apart from each other around the central core by air gaps. The spiral inductor 1112 includes a plurality of turns, the plurality of turns being located in the recesses of the support structure. In addition, the first end and the second end of the central core are configured to be attached to a substrate (e.g., Figure 4 PCB 402). Figure 1 Various details and embodiments of the fixed element 1110 and the spiral inductor 1112 are discussed in detail in FIG. 7 and are not repeated herein for the sake of brevity.

[0091] When incorporated into a defrost system (e.g. Figure 10 ), the input node 1102 of the matching network 1110 is electrically coupled to an RF signal source (eg, Figure 10 RF signal source 1010), and the output node 1104 is electrically coupled to the defrost chamber (eg, Figure 10 The electrodes (eg, Figure 10 first electrode 1016).

[0092] An intermediate node 1118 is positioned between the first variable capacitance network 1106 and the inductor assembly 1108. In one embodiment, a second variable component in the form of a second variable capacitance network 1120 is coupled between the intermediate node 1118 and a ground reference terminal (eg, Figure 10In an embodiment, the spiral inductor 1112 can be designed for relatively low frequency (e.g., about 40.66 MHz to about 40.70 MHz) operation and relatively high power (e.g., about 50 W to about 500 W) operation, and its size and inductance value are relatively large. For example, the value of the spiral inductor 1112 can be in the range of about 200 nH to about 600 nH, but in other embodiments, the value of the spiral inductor 1112 can be lower and / or higher. According to an embodiment, the spiral inductor 1112 is a fixed value lumped inductor (e.g., an air coil). The fixing element 1110 is adapted to locally support the spiral inductor 1112 to achieve inductance consistency and enable secure attachment to a substrate (e.g., Figure 4 PCB 402) to produce effective anti-vibration performance during operation.

[0093] The first variable capacitance network 1106 is coupled between the input node 1102 and the intermediate node 1118. The first variable capacitance network 1106 can be configured to match the input node 1102 to the intermediate node 1118. Figure 10 The first matching circuit 1026) modifies the RF signal source (e.g., Figure 10 The impedance of the RF signal source 1010) or more specifically matched as by a first matching circuit (e.g., Figure 10 The final power amplifier (eg, Figure 10 Therefore, the first variable capacitance network 1106 can be referred to as the “RF signal source matching portion” of the variable impedance matching network 1100.

[0094] In an example, the first variable capacitance network 1106 includes a first fixed-value capacitor 1122 coupled in parallel with a first variable capacitor 1124. The capacitance of the first fixed-value capacitor 1122 can be in the range of about 1 picofarad (pF) to about 100 pF. The first variable capacitor 1124 can include a network of capacitive components that can be selectively coupled to provide a capacitance in the range of 0 pF to about 100 pF. As such, the total capacitance provided by the first variable capacitance network 1106 can be in the range of about 1 pF to about 200 pF, although this range can also be extended to lower or higher capacitance values.

[0095] The "cavity matching portion" of the variable impedance matching network 1100 is provided by a second variable capacitance network 1120, which is coupled between node 1118 (located between the first variable capacitance network 1106 and the spiral inductor 1112) and the ground reference. In an example, the second variable capacitance network 1120 includes a second fixed-value capacitor 1126 coupled in parallel with a second variable capacitor 1128. The capacitance value of the second fixed-value capacitor 1126 can be in the range of approximately 1 pF to approximately 100 pF. The second variable capacitor 1128 can include a network of capacitive components that can be selectively coupled to provide a capacitance in the range of 0 pF to approximately 100 pF. As such, the total capacitance value provided by the second variable capacitance network 1120 can be in the range of approximately 1 pF to approximately 200 pF, although the range can also be extended to lower or higher capacitance values. The states of the first variable capacitance network 1106 and the second variable capacitance network 1120 may be changed to provide a plurality of capacitance values, and thus the states may be configurable to load the cavity (eg, Figure 10 The impedance of the defrost chamber 1004 plus the load 1024) is the same as the impedance of the RF signal source (e.g., Figure 10 RF signal source 1010) is best matched.

[0096] and Figure 10-11 The associated description discusses in detail an "unbalanced" defrost device in which an RF signal is applied to one electrode (e.g., Figure 10 1016) and place another "electrode" (e.g., Figure 10 As mentioned above, alternative embodiments of defrost devices include "balanced" defrost devices. In such devices, a balanced RF signal is provided to the two electrodes.

[0097] Figure 12 A balanced defrost system 1200 (eg, Figure 8 Defrost system 800, Figure 9 12 is a simplified block diagram of a defrost system 902, 904. In one embodiment, the defrost system 1200 includes an RF subsystem 1202, a defrost chamber 1204, a user interface 1206, a system controller 1208, an RF signal source 1210, power supply and bias circuitry 1212, a variable impedance matching network 1214, two electrodes 1216, 1217 (spaced a distance 1232 across the chamber 1204), and power detection circuitry 1220. In addition, in other embodiments, the defrost system 1200 may include one or more temperature sensors, one or more infrared (IR) sensors, and / or one or more weight sensors 1222, although some or all of these sensor components may not be included.

[0098] In the example, the RF subsystem 1202 includes a system controller 1208, an RF signal source 1210, a first impedance matching circuit 1226 (hereinafter referred to as the "first matching circuit"), a power supply and bias circuitry 1212, and a power detection circuitry 1220. The system controller 1208 is operatively and communicatively coupled to the user interface 1206, the RF signal source 1210, the power supply and bias circuitry 1212, the power detection circuitry 1220, the variable impedance matching network 1214, the power detection circuitry 1220, and the sensor 1222 (if included). The system controller 1208 is configured to receive signals indicating user input received via the user interface 1206 and to receive signals indicating RF signal reflected power (and possibly RF signal forward power) from the power detection circuitry 1220. In response to the received signals and measurements, and as will be described in greater detail later, the system controller 1208 provides control signals to the power supply and bias circuitry 1212 and the RF signal generator 1228 of the RF signal source 1210. Additionally, the system controller 1208 provides control signals to a variable matching subsystem 1246 (via a control path 1244 ) that causes the subsystem 1246 to change the state or configuration of the variable impedance matching network 1214 of the subsystem 1246 .

[0099] When the operating frequency and distance 1232 between electrodes 1216, 1217 are selected to define a sub-resonant inner defrost chamber 1204, first electrode 1216 and second electrode 1217 are capacitively coupled. More specifically, first electrode 1216 can be analogized as the first plate of a capacitor, second electrode 1217 can be analogized as the second plate of a capacitor, and load 1224, non-conductive barrier 1230, and the air within defrost chamber 1204 can be analogized as the capacitor dielectric. Therefore, first electrode 1216 may alternatively be referred to herein as the "anode," and second electrode 1217 may alternatively be referred to herein as the "cathode." Essentially, the voltage across first electrode 1216 and second electrode 1217 heats load 1224 of chamber 1204. According to various embodiments, RF subsystem 1202 is configured to generate an RF signal to produce a voltage across electrodes 1216, 1217.

[0100] The output of the RF signal source 1210 of the RF subsystem 1202 is electrically coupled to the variable matching subsystem 1246 via a conductive transmission path that includes a plurality of conductors 1234-1, 1234-2, 1234-3, 1234-4, and 1234-5 connected in series and collectively referred to as a transmission path 1234. According to an embodiment, the conductive transmission path 1234 includes an “unbalanced” portion and a “balanced” portion, wherein the “unbalanced” portion is configured to carry an unbalanced RF signal (i.e., a single RF signal referenced with respect to ground) and the “balanced” portion is configured to carry a balanced RF signal (i.e., two signals referenced with respect to each other). The "unbalanced" portion of the transmission path 1234 can include an unbalanced first conductor 1234-1 and an unbalanced second conductor 1234-2 within the RF subsystem 122, one or more connectors 1248, 1250 (each having a male connector portion and a female connector portion), and an unbalanced third conductor 1234-3 electrically coupled between the connectors 1248, 1250. The third conductor 1234-3 comprises a coaxial cable, but the electrical length can also be shorter or longer. In alternative embodiments, the variable matching subsystem 1246 can be housed with the RF subsystem 1202, and in such embodiments, the conductive transmission path 1234 can exclude the connectors 1248, 1250 and the third conductor 1234-3. In either case, the "balanced" portion of the conductive transmission path 1234 includes a balanced fourth conductor 1234-4 within the variable matching subsystem 1246 and a balanced fifth conductor 1234-5 electrically coupled between the variable matching subsystem 1246 and the electrodes 1216, 1217.

[0101] like Figure 12As shown, variable matching subsystem 1246 houses a device configured to: receive an unbalanced RF signal from RF signal source 1210 at the device's input via an unbalanced portion of the transmission path (i.e., the portion including unbalanced conductors 1234-1, 1234-2, and 1234-3); convert the unbalanced RF signal into two balanced RF signals (e.g., two RF signals with a phase difference of between 120 and 240 degrees, such as approximately 180 degrees); and generate the two balanced RF signals at the device's two outputs. For example, the conversion device may be balun 1252. The balanced RF signal is transmitted to variable impedance matching network 1214 via balanced conductor 1234-4 and ultimately to electrodes 1216 and 1217 via balanced conductor 1234-5. As will be described in more detail below, the variable impedance matching network 1214 is a two-terminal variable matching circuit that is configured to receive a balanced RF signal (e.g., via connection 1234-4), perform an impedance transformation corresponding to the current configuration of the two-terminal variable impedance matching network 1214, and provide a balanced RF signal to the first electrode 716 and the second electrode 717 via connection 1234-5.

[0102] RF signal source 1210 includes an RF signal generator 1228 and a power amplifier 1238 (e.g., including one or more power amplifier stages). In response to control signals provided by system controller 1208 via connection 1240, RF signal generator 1228 is configured to generate an oscillating electrical signal with a frequency in the ISM (Industrial, Scientific, and Medical) band, although the system can be modified to support operation in other frequency bands. RF signal generator 1228 can be controlled to generate oscillating signals at different power levels and / or different frequencies.

[0103] The power amplifier 1238 is configured to receive the oscillating signal from the RF signal generator 1228 and amplify the signal to produce a significantly higher power signal at the output of the power amplifier 1238. The power amplifier 1238 may include one or more amplifier stages. Figure 12 , power amplifier 1238 is depicted as including one amplifier stage coupled to other circuit components in a particular manner. In other embodiments, power amplifier 1238 may include other amplifier topologies and / or the amplifier arrangement may include only two or more than two amplifier stages.

[0104] The defrost chamber 1204 and any load 1224 positioned therein (e.g., food, liquid, etc.) present a cumulative load to the electromagnetic energy (or RF power) radiated into the chamber 1204 via the electrodes 1216, 1217. More specifically, and as previously described, the defrost chamber 1204 and load 1224 present an impedance to the system, referred to herein as the "chamber plus load impedance." Again, during defrost operation, the chamber plus load impedance changes as the temperature of the load 1224 increases. The chamber plus load impedance directly impacts the amount of reflected signal power along the conductive transmission path 1234 between the RF signal source 1210 and the electrodes 1216, 1217. In most cases, it is desirable to maximize the amount of signal power delivered to the chamber 1204 and / or minimize the ratio of reflected to forward signal power along the conductive transmission path 1234.

[0105] To at least partially match the output impedance of the RF signal generator 1228 to the cavity input impedance, a first matching circuit 1226 is electrically coupled along the transmission path 1234. The first matching circuit 1226 is configured to perform an impedance transformation from the impedance of the RF signal source 1210 (e.g., less than about 10 ohms) to an intermediate impedance (e.g., 50 ohms, 75 ohms, or some other value). The first matching circuit 1226 can have any of a variety of configurations to raise the impedance to an intermediate level between the output impedance of the RF signal generator 1228 and the cavity plus load impedance.

[0106] As described above, power detection circuitry 1220 is coupled along transmission path 1234 between the output of RF signal source 1210 and electrodes 1216, 1217. Power detection circuitry 1220 is configured to monitor, measure, or otherwise detect the power of a reflected signal traveling along transmission path 1234 between RF signal source 1210 and one or both of the one or more electrodes 1216, 1217. Power detection circuitry 1220 may also be configured to detect the power of a forward signal traveling along transmission path 1234 between RF signal source 1210 and one or more electrodes 1216, 1217.

[0107] The power detection circuitry 1220 supplies a signal to the system controller 1208 via connection 1242 that conveys a measured value of the reflected signal power and, in some embodiments, the forward signal power. When the reflected signal power magnitude exceeds a reflected signal power threshold or the reflected to forward signal power ratio exceeds an S11 parameter threshold, this indicates that the system 1200 is insufficiently matching the cavity plus load impedance and that the energy absorbed by the load 1224 within the cavity 1204 may be suboptimal. In such a situation, the system controller 1208 orchestrates a process for changing the state of the variable impedance matching network 1214 to drive the reflected signal power or S11 parameter closer to or below a desired level (e.g., below a reflected signal power threshold and / or a reflected to forward signal power ratio threshold), thereby re-establishing an acceptable match and promoting better energy absorption by the load 1224. For example, the system controller 1208 may provide a control signal to the variable impedance matching circuit 1214 via the control path 1244, causing the variable impedance matching circuit 1214 to change the inductance, capacitance, and / or resistance of one or more components within the circuit, thereby adjusting the impedance transformation provided by the variable impedance matching network 1214.

[0108] The variable impedance matching network 1214 can have any of a variety of configurations. For example, in various embodiments, the variable impedance matching network 1214 can include any one or more circuits selected from the group consisting of an inductor / capacitor (LC) network, an inductor-only network, a capacitor-only network, or a combination of a bandpass circuit, a highpass circuit, and a lowpass circuit. In embodiments where the variable impedance matching network 1214 is implemented in a balanced portion of the transmission path 1234, the variable impedance matching network 1214 is a two-terminal circuit having two inputs and two outputs. In an example, the variable impedance matching network 1214 includes a variable capacitor network (e.g., Figure 13 1204). However, in alternative embodiments, the variable impedance matching network 1214 may include both variable inductance and variable capacitance elements. The inductance, capacitance, and / or resistance values ​​provided by the variable impedance matching network 1214 may be established by control signals from the system controller 1208, which in turn affect the impedance transformation provided by the network 1214. By changing the state of the variable impedance matching network 1214 during processing operation to dynamically match the changing impedance of the cavity 1204 plus the load 1224 within the cavity 1204, system efficiency can be maintained at a high level throughout the defrost operation.

[0109] Figure 13 A two-terminal variable impedance matching network 1300 (eg, Figure 12The two-terminal variable impedance matching network 1300 can be used in a defrost system (e.g., Figure 8 Defrost system 800, Figure 9 Defrost system 902, 904, Figure 12 The two-terminal variable impedance matching network 1300 includes a network having fixed value and variable passive components.

[0110] The network 1300 includes a two-ended input having a first input node 1302 and a second input node 1304 and a two-ended output having a first output node 1306 and a second output node 1308. Figure 12 ), first input node 1302 can be connected to the first conductor of balanced conductor 1234-4, and second input node 1304 can be connected to the second conductor of balanced conductor 1234-4. Similarly, first output node 1306 can be connected to the first conductor of balanced conductor 1234-5, and second output node 1308 can be connected to the second conductor of balanced conductor 1234-5.

[0111] exist Figure 13 In the specific embodiment shown, circuit 1300 includes a first variable component in the form of a first capacitor network 1310 and a first inductor assembly 1312 coupled in series between a first input node 1302 and a first output node 1306. Circuit 1300 further includes a second variable component in the form of a second capacitor network 1314 and a second inductor assembly 1316 coupled in series between the second input node 1304 and a second output node 1308. First inductor assembly 1312 includes a first fixed element 1318 (e.g., Figure 1 3, the fixing element 102, the fixing element 600, the fixing element 700 of FIG. 7) and the first spiral inductor 1320 supported by the first fixing element 1318 (eg, Figure 1 2 and spiral inductor 112). Similarly, the second inductor assembly 1316 includes a second fixed element 1322 (e.g., Figure 1 3, the fixing element 102, the fixing element 600, the fixing element 700 of FIG. 7) and the second spiral inductor 1324 supported by the second fixing element 1322 (eg, Figure 1 and spiral inductor 112 in FIG. 2 ).

[0112] First spiral inductor 1320 has a first input 1326 coupled to the output of first capacitor network 1310 and a first output 1328 coupled to first output node 1302. Second spiral inductor 1324 has a second input 1330 coupled to the output of second capacitor network 1314 and a second output 1332 coupled to second output node 1308.

[0113] exist Figure 13 The schematic diagram of shows in highly simplified form the first fixed element 1318 and the first spiral inductor 1320 of the first inductor assembly 1312 and the second fixed element 1322 and the second spiral inductor 1324 of the second inductor assembly 1316. However, it should be understood that each of the first fixed element 1318 and the second fixed element 1322 includes a central core and a support structure, the support structure being coupled to and protruding outward from the central core, and the support structure having an outer edge, the outer edge having a recess extending toward the central core. In addition, the support structures are spaced apart from each other around the central core by an air gap. Each of the first spiral inductor 1320 and the second spiral inductor 1324 includes a plurality of turns, the plurality of turns being located in the recess of the support structure. In addition, the first end and the second end of the central core are configured to be attached to a substrate (e.g., Figure 4 PCB 402). Figure 1 Various details and embodiments of the first and second fixed elements 1318 and 1322 and the first and second spiral inductors 1320 and 1324 are discussed in conjunction with FIG. 7 and are not repeated herein for the sake of brevity.

[0114] In an embodiment, when first spiral inductor 1320 and second spiral inductor 1324 are designed for relatively low frequency operation (e.g., approximately 40.66 MHz to approximately 40.70 MHz) and relatively high power operation (e.g., approximately 50 W to approximately 500 W), the size and inductance of first spiral inductor 1320 and second spiral inductor 1324 are relatively large. For example, in other embodiments, first inductor 1320 and second inductor 1324 can each have a value in the range of approximately 100 nH to approximately 1000 nH (e.g., in the range of approximately 200 nH to approximately 600 nH), but the values ​​of the inductors can be lower and / or higher. According to an embodiment, inductors 1320, 1324 are fixed-value lumped air coil inductors. The first fixing element 1318 and the second fixing element 1322 suitably support the corresponding first spiral inductor 1320 and the second spiral inductor 1324 to achieve inductance consistency and enable secure attachment to a substrate (e.g., Figure 4 PCB 402) to produce effective anti-vibration performance during operation.

[0115] A first intermediate node 1334 is positioned between first variable capacitance network 1310 and first inductor assembly 1312, and a second intermediate node 1336 is positioned between second variable capacitance network 1314 and second inductor assembly 1316. In an embodiment, a third variable component in the form of a third variable capacitance network 1338 is coupled between first intermediate node 1334 and second intermediate node 1336.

[0116] First variable capacitance network 1310 and second variable capacitance network 1314 correspond to the "series matching portion" of matching network 1300. According to an embodiment, first variable capacitance network 1310 includes a first fixed-value capacitor 1340 coupled in parallel with a first variable capacitor 1342. First fixed-value capacitor 1340 may have a capacitance value in the range of approximately 1 pF to approximately 100 pF, and first variable capacitor 1342 may include a network of capacitive components that can be selectively coupled together to provide a capacitance in the range of 0 pF to approximately 100 pF. Similarly, second variable capacitance network 1314 includes a second fixed-value capacitor 1344 coupled in parallel with a second variable capacitor 1346. Second fixed-value capacitor 1344 may have a capacitance value in the range of approximately 1 pF to approximately 100 pF, and second variable capacitor 1346 may include a network of capacitive components that can be selectively coupled together to provide a capacitance in the range of 0 pF to approximately 100 pF.

[0117] To ensure that the signals provided to first output node 1306 and second output node 1308 are balanced, the capacitance values ​​of first variable capacitance network 1310 and second variable capacitance network 1314 are controlled to be substantially the same at any given time. For example, the capacitance values ​​of first variable capacitor 1342 and second variable capacitor 1346 can be controlled so that the capacitance values ​​of first variable capacitance network 1310 and second variable capacitance network 1314 are substantially the same at any given time. First variable capacitor 1342 and second variable capacitor 1346 operate in a paired manner, meaning that the capacitance values ​​of the first and second variable capacitors during operation are controlled at any given time to ensure that the RF signals delivered to first output node 1306 and second output node 1308 are balanced. In some embodiments, the capacitance values ​​of first fixed value capacitor 1340 and second fixed value capacitor 1344 can be substantially the same, but in other embodiments, the capacitance values ​​can be different.

[0118] The "parallel matching portion" of the variable impedance matching network 1300 is provided by the third variable capacitance network 1338 and the fixed first spiral inductor 1320 and the fixed second spiral inductor 1324. In an example, the third variable capacitance network 1338 includes a third fixed value capacitor 1348 coupled in parallel with a third variable capacitor 1350. The third fixed value capacitor 1348 can have a capacitance value in the range of approximately 1 pF to approximately 500 pF, and the third variable capacitor 1350 can include a network of capacitive components that can be selectively coupled together to provide a capacitance in the range of 0 pF to approximately 200 pF.

[0119] Because the state of the variable capacitance network 1310, 1314, 1338 can be changed to provide multiple capacitance values, the variable capacitance network 1310, 1314, 1338 can be configured to load the cavity (e.g., Figure 12 The impedance of the cavity 1204 plus the load 1224) is the same as that of the RF signal source (e.g., Figure 12 By changing the capacitance values ​​of the variable capacitors 1342, 1346, 1350 in the matching network 1300, the system controller (e.g., Figure 12 The system controller 1208 can increase or decrease the impedance transformation provided by the matching network 1300. It is desirable that the capacitance value change improves the overall impedance match between the RF signal source 1210 and the impedance of the cavity plus the load, which should result in a decrease in reflected signal power and / or a ratio of reflected to forward signal power. In most cases, the system controller 1208 can attempt to configure the matching network 1300 to achieve a maximum electromagnetic field strength in the defrost cavity 1204 and / or a maximum amount of power absorbed by the load 1224 and / or a minimum amount of power reflected by the load 1224.

[0120] It should be understood that Figure 11 and Figure 13 The variable impedance matching networks 1100, 1300 shown are two possible circuit configurations that can perform desired single-ended and double-ended variable impedance transformations. Other embodiments of single-ended and double-ended variable impedance matching circuits may include differently arranged inductive or capacitive networks or may include passive networks comprising various combinations of inductors, capacitors, and / or resistors, wherein some of the passive components may be fixed-value components and some of the passive components may be variable-value components (e.g., variable inductors, variable capacitors, and / or variable resistors). In any of these other embodiments, relatively large air-coil spiral inductors may be incorporated into inductor assemblies, each of which includes fixing elements such as those described above for supporting the spiral inductor to achieve inductance consistency and enable secure attachment to a substrate (e.g., Figure 4PCB 402) to produce effective anti-vibration performance during operation.

[0121] The foregoing description refers to elements, nodes, or features being "connected" or "coupled" together. As used herein, unless expressly specified otherwise, "connected" means that one element is directly, and not necessarily mechanically, joined to (or in direct communication with) another element. Similarly, unless expressly specified otherwise, "coupled" means that one element is directly or indirectly, and not necessarily mechanically joined to (or in direct or indirect communication with) another element. Thus, although the schematic diagrams shown in the accompanying drawings depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in embodiments of the depicted subject matter.

[0122] Embodiments disclosed herein require an inductor assembly, an impedance matching network including the inductor assembly, and a system including the impedance matching network and the inductor assembly. The system can be a defrost (or thawing) system that implements one or more impedance matching networks. The inductor assembly includes a fixing element that supports a spiral inductor having multiple turns. The fixing element includes multiple support structures surrounding a central core, and each support structure includes an outer edge with a recessed notch profile. The turns of the spiral inductor are located in the recesses of the support structures. The recesses in the support structures extend evenly along the support structures to ensure that the gap between each turn of the spiral inductor is uniform. In addition, the fixing element retains all the turns of the spiral inductor so that the turns cannot deviate freely, and the fixing element can be directly attached to a substrate, such as a printed circuit board (PCB). Therefore, the fixing element can ensure the consistency of the inductance of the spiral inductor and can also provide a firm support for the spiral inductor to enable good anti-vibration performance.

[0123] This disclosure is intended to explain how to design and use various embodiments according to the present invention and is not intended to limit the true, intended and reasonable scope and spirit of the present invention. The above description is not intended to be exhaustive or to limit the present invention to the exact form disclosed. In view of the above teachings, modifications or changes are possible. One or more embodiments have been selected and described in order to provide the best demonstration of the principles of the present invention and its practical application and to enable those skilled in the art to utilize the present invention in various embodiments and together with various modifications as are suitable for the specific purposes envisioned. When interpreted according to the scope of fairness, legality and reasonable authorization, all such modifications and changes are within the scope of the present invention as determined by the appended claims and all equivalents thereof that may be amended during the pendency of this patent application.

Claims

1. An inductor assembly, characterized in that: include: a securing element having a central core and first and second support structures coupled to and projecting outwardly from the central core, each of the first and second support structures having an outer edge with a concave notch profile extending toward the central core; as well as a spiral inductor having a plurality of turns, the turns being located in the recesses of the first and second support structures; Each of the first and second support structures includes an opening extending through the first support structure, the second support structure, and the central core.

2. The inductor assembly according to claim 1, wherein The first and second support structures are spaced apart from each other around the central core by an air gap.

3. The inductor assembly according to claim 1, wherein Each of the recesses exhibits a first width parallel to the longitudinal dimension of the fixing element, the first width being the same for each of the recesses and corresponding to a second width of one of the turns of the spiral inductor.

4. The inductor assembly according to claim 1, wherein said first support structure having a first set of said recesses extending towards said central core; and The second support structure has a second set of recesses extending toward the central core, wherein individual recesses of the second set of recesses are offset from individual recesses of the first set of recesses relative to the longitudinal dimension of the fixing element to accommodate the turns of the spiral inductor.

5. The inductor assembly according to claim 1, wherein Also includes: a third support structure; as well as a fourth support structure, wherein the first, second, third, and fourth support structures are equally spaced from one another around the central core, and the turns of the spiral inductor are located in the recesses of the first, second, third, and fourth support structures.

6. The inductor assembly according to claim 1, wherein The fixing element is formed of a thermally stable material having a thermal stability greater than two hundred degrees Celsius.

7. An impedance matching network, characterized in that: include: First input node; First output node; as well as a first variable impedance component and a first inductor assembly, the first variable impedance component and the first inductor assembly being coupled in series between the first input node and the first output node, the value of the first variable component being adjustable to affect an impedance transformation provided by the impedance matching network, and the first inductor assembly comprising: a fixed element having a central core and first and second support structures coupled to and projecting outwardly from the central core, each of the first and second support structures having an outer edge with a concave notch profile extending toward the central core, wherein each of the first and second support structures includes an opening extending through the first and second support structures and the central core; as well as A spiral inductor having a plurality of turns, the turns being located in the recess of the support structure, the input end of the spiral inductor being coupled to the output of the first variable impedance component, and the output end of the spiral inductor being coupled to the first output node.

8. The impedance matching network according to claim 7, wherein: Also includes: a first intermediate node located between the first variable impedance component and the first inductor assembly; Second input node; Second output node; a second variable impedance component and a second inductor assembly, the second variable impedance component and the second inductor assembly being coupled in series between the second input node and the second output node, a second value of the second variable impedance component being adjustable to affect an impedance transformation provided by the impedance matching network, and the second inductor assembly comprising: a second securing element having a second central core and a second support structure coupled to and projecting outwardly from the second central core, each of the second support structures having a second outer edge with a concave second notch profile extending toward the second central core, wherein each of the first and second support structures includes an opening extending through the first support structure, the second support structure, and the central core; and a second spiral inductor having a plurality of second turns, the second turns being located in the recess of the second support structure, a second input terminal of the second spiral inductor being coupled to the second output of the second variable impedance component, and a second output terminal of the second spiral inductor being coupled to the second output node; a second intermediate node located between the second variable impedance component and the second inductor assembly; and A third variable impedance component is coupled between the first intermediate node and the second intermediate node.

9. A heat addition system coupled to a cavity configured to accommodate a load, characterized in that The heat addition system comprises: a radio frequency (RF) signal source configured to supply an RF signal; a transmission path electrically coupled between the RF signal source and first and second electrodes positioned at opposite ends of the cavity; and an impedance matching network electrically coupled along the transmission path, wherein the impedance matching network comprises: First input node; a first output node; and a first variable impedance component and a first inductor assembly, the first variable impedance component and the first inductor assembly being coupled in series between the first input node and the first output node, the value of the first variable impedance component being adjustable to affect an impedance transformation provided by the impedance matching network, and the first inductor assembly comprising: a fixed element having a central core and first and second support structures coupled to and projecting outwardly from the central core, each of the first and second support structures having an outer edge with a concave notch profile extending toward the central core, each of the first and second support structures including an opening extending through the first and second support structures and the central core; and A spiral inductor having a plurality of turns, the turns being located in the recess of the support structure, the input end of the spiral inductor being coupled to the output of the first variable impedance component, and the output end of the spiral inductor being coupled to the first output node.

10. The heat addition system according to claim 9, wherein: said first support structure having a first set of said recesses extending towards said central core; and The second support structure has a second set of recesses extending toward the central core, wherein individual recesses in the second set of recesses are offset from individual recesses in the first set of recesses in a longitudinal direction relative to the spiral inductor to accommodate the turns of the spiral inductor.

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