Passive negative inductor and method of manufacturing passive negative inductor

Abstract

The present disclosure discloses a negative inductor device (300). The negative inductor arrangement comprises a negative inductor (200) comprising a ferromagnetic material (200) and a conductive material (203) disposed inside the ferromagnetic material. The negative inductor arrangement further includes a current limiting circuit (301) electrically coupled to the negative inductor and configured to supply a current (303) of magnitude within a range (307) defined by a first local minimum (121a) and a second local minimum (121b) of a current-energy curve of the ferromagnetic material.

Description

Technical Field

[0001] The present disclosure relates generally to circuits and, more particularly, to a negative inductor and a method of making the negative inductor. Background Art

[0002] An inductor is typically a passive two-terminal electrical component that stores energy in the form of a magnetic field when current flows through it. An exemplary implementation of a basic inductor is an insulated wire wound into a coil. When the current flowing through the coil varies, the time-varying magnetic field induces an electromotive force (emf) (voltage) in the coil, as described by Faraday's law of induction. Such an inductor is also referred to herein as a positive inductor to contrast such an inductor with a negative inductor.

[0003] At least in theory, negative inductors exhibit properties that are opposite to those of positive inductors. For example, in a positive inductor, the magnetic flux associated with the positive inductor increases as the current flowing through the positive inductor increases. However, in a negative inductor, this phenomenon is reversed, that is, the magnetic flux associated with the negative inductor decreases as the current flowing through the negative inductor increases. Similarly, a positive inductor has a "U" shaped energy versus current curve (U versus i), which gives the inductance value. In contrast, the energy versus current curve of a negative inductor is shaped like an inverted "U".

[0004] The effect of a negative inductor is evaluated based on the theory supported by an active negative inductor, such as a negative impedance converter (NIC). A NIC is an active circuit that injects energy into a circuit, compared to an ordinary load that consumes energy from the circuit. A NIC works by adding or subtracting a voltage that varies excessively in series with the voltage drop across an equivalent positive impedance. However, having an active negative inductor in a circuit requires extra energy and extra space, which is undesirable.

[0005] Therefore, a negative inductor is still required. Summary of the invention

[0006] It is an object of some embodiments to provide a composite material component that can be used as a negative inductor. It is another object of some embodiments to use passive components to manufacture a negative inductor to obtain a passive negative inductor. Additionally or alternatively, it is an object of some embodiments to provide such a negative inductor suitable for inclusion in an integrated circuit. Additionally or alternatively, it is an object of some embodiments to provide a method of manufacturing a negative inductor.

[0007] Some embodiments are based on the understanding that the properties of ferromagnetic materials can be used to construct negative capacitors. To this end, some embodiments aim to explore the properties of ferromagnetic materials to construct negative inductors. For example, some embodiments are based on the recognition that the current-energy curve of ferromagnetic materials is a "W" shaped curve. The current-energy curve of the ferromagnetic material includes two local minima, namely, a first local minimum and a second local minimum. Between the two local minima, near zero current, there is an inverted U-shape similar to the current-energy curve of a negative inductor. Therefore, the inverted U-shape of the current-energy curve of the ferromagnetic material has a negative curvature that results in a negative inductance. The region corresponding to the inverted U-shape of the current-energy curve of the ferromagnetic material is called the negative inductance region.

[0008] Some embodiments are based on the realization that since the negative inductance region has high energy, the ferromagnetic material will not stay in the negative inductance region and end up in either of the two local minima. In addition, ferromagnetic materials are not conductive, which hinders the realization of inductors.

[0009] Some embodiments are based on the recognition supported by simulations and experiments that if a conductive material is inserted into a ferromagnetic material to pass an electric current, the magnetic field of the conductive material passing the current interacts with the ferromagnetic material to produce negative inductor properties in the negative inductance region. This interaction allows the creation of an electrical component that acts as a negative inductor. To this end, a negative inductor can be constructed by arranging a conductive material inside a ferromagnetic material.

[0010] In an embodiment, a conductive material is arranged inside a ferromagnetic material so that most of the conductive material is inside the ferromagnetic material and two opposite ends of the conductive material protrude to the surface or outside of the ferromagnetic material. The two ends of the conductive material form terminals of a negative inductor for electrical connection with other devices or circuits. In an alternative embodiment, the conductive material is arranged inside the ferromagnetic material so that the entire conductive material is completely surrounded by the ferromagnetic material. In such an embodiment, in order to allow electrical connection, the terminals are separately formed of a material different from the conductive material and are electrically connected to the opposite ends of the conductive material.

[0011] Furthermore, some embodiments are based on the recognition that, in order to operate in the negative inductance region, the negative inductor must be supplied with a current whose magnitude falls within a range defined by a first local minimum and a second local minimum of the current-energy curve of the ferromagnetic material. In order to supply a current whose magnitude is within a range defined by the first local minimum and the second local minimum of the current-energy curve of the ferromagnetic material, the negative inductor is connected to a current limiting circuit. The negative inductor and the current limiting circuit together form a negative inductor device.

[0012] The current limiting circuit is configured to supply a current "i" having a magnitude within a range defined by a first local minimum and a second local minimum of a current-energy curve of the ferromagnetic material. For example, the current "i" corresponding to the first local minimum 1 " and the current "i corresponding to the second local minimum 2 "Limit the range of current size (i 1 to i 2 The current limiting circuit supply size falls within this range (i 1 to i 2 ) within the current “i”.

[0013] According to an embodiment, the scope of the negative inductance region depends on the type of ferromagnetic material and / or the mutual arrangement of the conductive material within the ferromagnetic material. For example, in some embodiments, the ferromagnetic material is in the shape of a slab and the conductive material is a lead twisted into a spiral. The cross-section of the lead includes one or a combination of circular, semicircular, rectangular and semi-rectangular shapes. The plate-shaped ferromagnetic material surrounds the spiral conductive material so that the geometric center of the plate-shaped ferromagnetic material coincides with the geometric center of the spiral conductive material. These shapes and arrangements of ferromagnetic materials and conductive materials are advantageous, for example, using a spiral conductive material to increase the inductance of the negative inductor. Since the negative inductor is constructed using passive elements such as ferromagnetic materials and conductive materials, the negative inductor is referred to as a passive negative inductor.

[0014] In some embodiments, the types of ferromagnetic material and conductive material are selected mutually or independently based on the application of the negative inductor. Examples of conductive materials used in different embodiments include copper, aluminum, steel, iron, etc. Examples of ferromagnetic materials used in different embodiments include various ferromagnetic oxides, cobalt, magnetite, dysprosium, nickel, gadolinium, tungsten, permalloy, etc.

[0015] Some embodiments are based on the recognition that it is advantageous to connect a negative inductor in parallel or in series with a positive inductor. For example, a negative inductor may be connected in parallel with a positive inductor for inductor amplification. In addition, negative inductors may be used in different circuits, such as microwave circuits, monolithic microwave integrated circuits (MMICs), radio frequency integrated circuits (RFICs), power electronic circuits, and the like. For example, in RFICs, implementing an inductor consumes considerable chip area. Therefore, it is desirable to manufacture an inductor that consumes less chip area. According to an embodiment, by consuming less chip area, a negative inductor can be used to amplify the value of a positive inductor in an RFIC. In addition, in some embodiments, a negative inductor may be used as a non-Foster element (e.g., a non-Foster broadband antenna, a non-Foster artificial magnetic conductor) in various devices and components to eliminate the narrowband resonant behavior inherent in the above-mentioned devices.

[0016] In addition, some embodiments provide a method for manufacturing a negative inductor. The method includes providing a substrate. The substrate includes, but is not limited to, silicon (Si), silicon carbide (SiC), diamond, gallium nitride (GaN), etc. For illustration, consider a Si substrate. The Si substrate may be cleaned according to a piranha cleaning method and / or an RCA cleaning method. In addition, a ferromagnetic oxide is deposited on the cleaned Si substrate using a deposition method (e.g., a pulsed laser deposition method).

[0017] After the ferromagnetic oxide is deposited, the sample can be annealed in an oxygen environment. In addition, a metal spiral is formed on the surface of the ferromagnetic oxide using, for example, photolithography and a lift-off process. In addition, another layer of ferromagnetic oxide is deposited so that the metal spiral is completely immersed in the ferromagnetic oxide. Another layer of ferromagnetic oxide is deposited using a pulsed laser deposition method.

[0018] Thus, one embodiment discloses a negative inductor device. The negative inductor device includes a negative inductor including a ferromagnetic material and a conductive material disposed inside the ferromagnetic material. The negative inductor device also includes a current limiting circuit electrically coupled to the negative inductor and configured to supply a current within a range defined by a first local minimum and a second local minimum of a current-energy curve of the ferromagnetic material.

[0019] Therefore, another embodiment discloses a negative inductor. The negative inductor device includes: a ferromagnetic material; and a conductive material partially surrounding the ferromagnetic material so that opposite ends of the conductive material protrude from the ferromagnetic material, wherein the opposite ends of the conductive material protruding from the ferromagnetic material correspond to terminals of the negative inductor.

[0020] Therefore, another embodiment discloses a method for manufacturing a negative inductor. The method includes the following steps: depositing a first layer of ferromagnetic material on a substrate; forming a metal spiral on a surface of the first layer of ferromagnetic material; and depositing a second layer of ferromagnetic material on the first layer of ferromagnetic material and the metal spiral. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [ Figure 1A ] Figure 1A A schematic diagram depicting the current-flux characteristics of a negative inductor according to some embodiments of the present disclosure is shown.

[0022] [ Figure 1B ] Figure 1B A schematic diagram depicting the current-energy characteristics of a negative inductor according to some embodiments of the present disclosure is shown.

[0023] [ Figure 1C ] Figure 1C An energy landscape diagram of a ferromagnetic material according to some embodiments of the present disclosure is shown.

[0024] [ Figure 2 ] Figure 2 A negative inductor according to some embodiments of the present disclosure is shown.

[0025] [ Figure 3A ] Figure 3A Schematic diagram showing a negative inductor device according to some embodiments of the present disclosure.

[0026] [ Figure 3B ] Figure 3B A range of current magnitudes defined by a first local minimum and a second local minimum of a current-energy curve of a ferromagnetic material is shown according to some embodiments of the present disclosure.

[0027] [ Figure 3C ] Figure 3C A circuit diagram for implementing a current limiting circuit according to some embodiments of the present disclosure is shown.

[0028] [ Figure 4A ] Figure 4A Schematic diagram showing a negative inductor according to some other embodiments of the present disclosure.

[0029] [ Figure 4B ] Figure 4B Showing some other embodiments according to the present disclosure Figure 4A Different stereograms of the negative inductor.

[0030] [ Figure 5A ] Figure 5A A circuit diagram including a negative inductor and a positive inductor connected in parallel is shown according to some other embodiments of the present disclosure.

[0031] [ Figure 5B ] Figure 5B A circuit diagram including a negative inductor and a positive inductor connected in series according to some other embodiments of the present disclosure is shown.

[0032] [ Figure 6 ] Figure 6 A schematic diagram showing a method of manufacturing a negative inductor according to some other embodiments of the present disclosure.

[0033] Embodiments of the present disclosure will be further described with reference to the accompanying drawings. The drawings shown are not necessarily to scale, emphasis generally being placed upon illustrating the principles of embodiments of the present disclosure. DETAILED DESCRIPTION

[0034] In the following description, for the purpose of illustration, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other cases, the devices and methods are shown only in block diagram form to avoid obscuring the present disclosure.

[0035] As used in this specification and claims, the terms "for example" and "such as" and the verbs "include," "have," "comprises," and other verb forms thereof, when used in conjunction with a list of one or more components or other items, should each be interpreted as open-ended, meaning that the list should not be viewed as excluding other additional components or items. The term "based on" means based at least in part on. In addition, it will be understood that the phraseology and terminology employed herein are for descriptive purposes and should not be viewed as limiting. Any headings utilized within this description are for convenience only and have no legal or limiting effect.

[0036] It is an object of some embodiments to provide a composite material component that can be used as a negative inductor. In addition, it is an object of some embodiments to use passive components to manufacture the negative inductor to obtain a passive negative inductor. Additionally or alternatively, it is an object of some embodiments to provide such a negative inductor suitable for inclusion in an integrated circuit.

[0037] Negative inductors exhibit properties that are opposite to those of positive inductors (or normal inductors). For example, in a positive inductor, the magnetic flux associated with the positive inductor increases as the current through the positive inductor increases. However, in a negative inductor, this phenomenon is reversed, as shown below in Figure 1A Described in .

[0038] Figure 1A A schematic diagram depicting the current-flux characteristics of a negative inductor according to some embodiments of the present disclosure is shown 100. A current-flux curve 101 is drawn between the current 103 through the negative inductor and the magnetic flux 105 associated with the negative inductor. The current-flux curve 101 means that the magnetic flux associated with the negative inductor decreases as the current through the negative inductor increases.

[0039] Additionally, some embodiments are based on the understanding that the current-energy curve of a positive inductor is a U-shaped curve, while the current-energy curve of a negative inductor is an inverted U-shaped curve.

[0040] Figure 1B A schematic diagram 107 depicting the current-energy characteristics (or current-energy curve) of a negative inductor according to some embodiments of the present disclosure is shown. A current-energy curve 109 of the negative inductor is drawn between the current 111 through the negative inductor and the energy 113 of the negative inductor. The shape of the current-energy curve 109 of the negative inductor is an inverted U shape.

[0041] Some embodiments are based on the understanding that the properties of ferromagnetic materials can be used to construct Figure 1A and Figure 1B To this end, some embodiments aim to explore the properties of ferromagnetic materials to construct negative inductors.

[0042] Figure 1C An energy state diagram 127 of a ferromagnetic material according to some embodiments of the present disclosure is shown. A current-energy curve 115 of the ferromagnetic material is drawn between a current 117 passing through the ferromagnetic material and an energy 119 of the ferromagnetic material. The current-energy curve 115 includes two local minima, namely, a first local minimum 121a and a second local minimum 121b. Between the two local minima 121a and 121b, there is an inverted U-shape 123 similar to the current-energy curve 109 of the negative inductor near zero current. Therefore, the inverted U-shape 123 of the current-energy curve 115 of the ferromagnetic material has a negative curvature that results in a negative inductance. The region 125 corresponding to the inverted U-shape 123 of the current-energy curve 115 is referred to as a negative inductance region.

[0043] According to an embodiment, the negative inductance behavior can be understood from the Landau mean field theory. According to the Landau mean field theory, the Gibbs free energy of a ferromagnetic material is given by

[0044]

[0045] Here, a and c are material-based parameters. As long as the temperature is below the Curie temperature (usually >10,000 degrees Celsius), the material-based parameter "a" is negative, resulting in negative inductance.

[0046] Some embodiments are based on the realization that the ferromagnetic material will not stay in the negative inductance region 125, ending up in either of the two local minima 121a and 121b, due to the high energy of the negative inductance region 125. Furthermore, ferromagnetic materials are not conductive, which hinders the realization of inductors.

[0047] Some embodiments are based on the recognition supported by simulations and experiments that if a conductive material is inserted into a ferromagnetic material to pass a current, the magnetic field of the conductive material passing the current interacts with the ferromagnetic material to produce negative inductor properties within the negative inductance region 125. This interaction allows the creation of an electrical component that acts as a negative inductor. To this end, a negative inductor can be constructed by arranging a conductive material inside a ferromagnetic material. Such a negative inductor is Figure 2 Described in.

[0048] Figure 2A negative inductor 200 according to some embodiments of the present disclosure is shown. The negative inductor 200 includes a ferromagnetic material 201 and a conductive material 203 arranged inside the ferromagnetic material 201. In an embodiment, the conductive material 203 is partially surrounded inside the ferromagnetic material 201, so that most of the conductive material 203 is inside the ferromagnetic material 201, and two opposite ends of the conductive material 203: a first end 205a and a second end 205b protrude to the surface or outside of the ferromagnetic material 201. The first end 205a and the second end 205b of the conductive material 203 form terminals of the negative inductor 200 for electrical connection with other devices or circuits. Therefore, the first end 205a and the second end 205b are respectively referred to as the first terminal 205a and the second terminal 205b.

[0049] In an alternative embodiment, the conductive material 203 is arranged inside the ferromagnetic material 201 so that the entire conductive material 203 is completely surrounded by the ferromagnetic material 203. In such an embodiment, to allow electrical connection, the first terminal 205a and the second terminal 205b are separately formed of a material different from the conductive material 203 and are electrically connected to opposite ends of the conductive material 203, respectively.

[0050] Furthermore, some embodiments are based on the recognition that, in order to operate in the negative inductance region 125, a current having a magnitude falling within the range defined by the first local minimum 121a and the second local minimum 121b must be supplied to the negative inductor 200. In order to supply a current having a magnitude within the range defined by the first local minimum 121a and the second local minimum 121b, the negative inductor 200 is connected to a current limiting circuit 301. The negative inductor 200 and the current limiting circuit 301 together form a negative inductor device.

[0051] Figure 3A A schematic diagram of a negative inductor device 300 according to some embodiments of the present disclosure is shown. The negative inductor device 300 includes a negative inductor 200 and a current limiting circuit 301. The negative inductor 200 is electrically coupled to the current limiting circuit 301. For example, the current limiting circuit 301 is connected to the negative inductor 200 via a first terminal 205a and a second terminal 205b. The current limiting circuit 301 is configured to supply a current "i" 303 having a magnitude within a range defined by the first local minimum 121a and the second local minimum 121b.

[0052] For example, refer to Figure 3B , the current "i 1 " 305a and the current "i corresponding to the second local minimum 121b 2 ”305b defines the current range (i 1 to i 2) 307. The current limiting circuit 301 supplies a current "i" 303 whose magnitude falls within the range 307. Figure 3C An example implementation of the current limiting circuit 301 is described in .

[0053] Figure 3C A circuit diagram for implementing a current limiting circuit 301 according to some embodiments of the present disclosure is shown.

[0054] The current limiting circuit 301 includes bipolar transistors 309 and 311, a reference source 313, and a resistor 315. The bipolar transistors 309 and 311 form a current mirror circuit. According to an embodiment, the reference source 313 outputs a reference value defining the magnitude of the current flowing through the bipolar transistor 311 and the negative inductor 200. The reference source 313 outputs the reference value based on the range 307. The reference source 313 may output the reference value as a fixed value, or may output a variable reference value defining the magnitude of the current within the range 307. In addition, the current flowing through the bipolar transistor 309 is based on the current passing through the bipolar transistor 311.

[0055] Figure 3C The circuit configuration of the current limiting circuit 301 shown is only an example, and the current limiting circuit 301 of the present disclosure is not limited to Figure 3C The current limiting circuit 301 may have different circuit configurations.

[0056] According to an embodiment, the extent of the negative inductance region 125 depends on the type of ferromagnetic material 201 and / or the mutual arrangement of the conductive material 203 within the ferromagnetic material 201. For example, in some embodiments, the ferromagnetic material 201 has a first shape, the conductive material 203 has a second shape, and the first shape of the ferromagnetic material surrounds the second shape of the conductive material, so that the geometric center of the first shape coincides with the geometric center of the second shape. The first shape and the second shape are symmetrical or asymmetrical shapes. Such an embodiment is described below in Figure 4A and Figure 4B Described in.

[0057] Figure 4A A schematic diagram of a negative inductor 400 according to some other embodiments of the present disclosure is shown. Figure 4B A different perspective view 410 of a negative inductor 400 according to some other embodiments of the present disclosure is shown. The negative inductor 400 includes a ferromagnetic material 401 and a conductive material 403. The ferromagnetic material 401 is in a plate shape, and the conductive material 403 is a lead wire twisted into a spiral. The cross-section of the lead wire includes one or a combination of circular, semicircular, rectangular, and semi-rectangular shapes. The plate-shaped ferromagnetic material 401 surrounds the spiral-shaped conductive material 403, so that the geometric center F of the plate-shaped ferromagnetic material 401 is c and the geometric center C of the spiral conductive material 403 cThese shapes and arrangements of the ferromagnetic material 401 and the conductive material 403 are advantageous, for example, using the spiral conductive material 403 to increase the inductance of the negative inductor 400 .

[0058] The negative inductor 400 (or the negative inductor 200) is constructed using passive elements such as a ferromagnetic material 401 and a conductive material 403. Therefore, the negative inductor 400 (or the negative inductor 200) is referred to as a passive negative inductor.

[0059] Some embodiments are based on the recognition that it is advantageous to connect the negative inductor 400 in parallel or in series with the positive inductor. For example, the negative inductor 400 can be connected in parallel with the positive inductor for inductor amplification, as shown below Figure 5A Described in .

[0060] Figure 5A A circuit diagram 500 including a negative inductor 400 and a positive inductor 501 connected in parallel is shown according to some other embodiments of the present disclosure. Some embodiments are based on the understanding that when two positive inductors of inductances L1 and L2 are connected in parallel to each other, then the total inductance L is less than the inductance of the individual inductors.

[0061] L=L1||L2=L1*L2 / (L1+L2), where L <L1,L2。

[0062] However, if the negative inductor 400 is connected in parallel with the positive inductor 501, the total inductance of the parallel connection is greater than the individual inductances. For example, if L2 is negative, then L = (L1*-L2) / (L1-L2). Here, L will be positive if and only if |L2|>L1. In this way, the negative inductor 400 is used for inductor amplification. The first terminal 503a and the second terminal 503b are used to allow electrical connection with other circuits and devices.

[0063] Additionally or alternatively, in some embodiments, the negative inductor 400 and the positive inductor 501 may be connected in series. Figure 5B A circuit diagram 505 including a negative inductor 400 and a positive inductor 501 connected in series is shown according to some other embodiments of the present disclosure. The series connection of the negative inductor 400 and the positive inductor 501 is advantageous because such a series connection results in a higher size inductor with a smaller chip area. Various analog and radio frequency (RF) applications such as oscillators and power amplifiers require higher size inductors. The series connection of the negative inductor 400 and the positive inductor 501 not only saves chip area, but also results in an inductor with a high Q value.

[0064] In addition, the negative inductor 400 can be used in different circuits, such as microwave circuits, monolithic microwave integrated circuits (MMICs), radio frequency integrated circuits (RFICs), power electronic circuits, etc. For example, in RFICs, the implementation of the inductor consumes a considerable chip area. Therefore, it is desirable to manufacture an inductor that consumes less chip area. According to an embodiment, by consuming less chip area, the negative inductor 400 can be used to amplify the value of the positive inductor in the RFIC.

[0065] In addition, in some embodiments, the negative inductor 400 can be used as a non-Foster element in various devices and components such as broadband antennas and artificial magnetic conductors. Non-Foster circuit elements are elements that do not obey the Foster theorem. The negative inductor 400 can be used as a non-Foster element in a broadband antenna to eliminate the narrowband resonant behavior inherent in the broadband antenna.

[0066] In addition, the negative inductor 400 can be used to improve the impedance matching between the power amplifier (PA) and the antenna. For example, in a transmitter system, a passive matching network is inserted between the output of the power amplifier (PA) and the antenna to match the output impedance of the PA with the output impedance of the antenna. The passive matching network usually includes one or more capacitors and one or more inductors. The passive matching network receives power only from its source (usually the PA) without any external power supply. The passive matching network obeys the Foster reactance theorem and works well in matching the impedance of the PA with the impedance of the antenna at a single frequency. However, since inductors and capacitors in the real world are non-ideal, that is, they have resistance in addition to reactance, they are not perfect even at a single frequency. In addition, most practical applications require the transmitter to operate over a certain bandwidth, especially when using physically small antennas. It is often impossible to achieve acceptable or desirable impedance matching over an acceptable or desirable bandwidth using a Foster (passive) network. Impedance matching can be improved using a non-Foster (or active) network based on a negative inductor 400. The non-Foster network based on the negative inductor 400 may be referred to as a non-Foster impedance matching circuit.The non-Foster network based on the negative inductor 400 cancels the reactance of the antenna, which in turn improves the efficiency and bandwidth of the PA.

[0067] Additionally, in some embodiments, the negative inductor 400 can be used as a non-Foster element in an artificial magnetic conductor. An artificial magnetic conductor (AMC) is a metamaterial that simulates a magnetic conductor over a limited bandwidth. An AMC ground plane allows conformal antennas with current flowing parallel to the surface because the parallel image currents in the AMC ground plane enhance their source. An AMC can have a limited bandwidth. Its bandwidth is proportional to the substrate thickness and permeability. At VHF-UHF frequencies, the thickness and / or permeability required for a reasonable AMC bandwidth is too large for antenna ground plane applications.

[0068] The negative inductor 400 can be used as a non-Foster element to overcome the bandwidth limitation of the AMC. When the AMC is loaded with the negative inductor 400, its negative inductance is paralleled with the substrate inductance resulting in a larger net inductance, thus resulting in a larger AMC bandwidth. In addition, the negative inductor 400 can be used as a non-Foster element in the AMC to eliminate the narrow-band resonant behavior inherent in the AMC.

[0069] In some embodiments, the types of ferromagnetic material 401 and conductive material 403 are selected mutually or independently based on the application of negative inductor 400. Examples of conductive materials used in different embodiments include copper, aluminum, steel, iron, etc. Examples of ferromagnetic materials used in different embodiments include various ferromagnetic oxides, cobalt, magnetite, dysprosium, nickel, gadolinium, tungsten, permalloy, etc.

[0070] In an embodiment, the negative inductor 400 is formed by dipping the spiral conductive material 403 into a ferromagnetic oxide as a ferromagnetic material. Similarly, the negative inductor 200 is formed by dipping the conductive material 203 into the ferromagnetic oxide. The manufacturing method of the negative inductor 400 (or the negative inductor 200) is as follows. Figure 6 Detailed description in.

[0071] Figure 6 A schematic diagram of a method of manufacturing a negative inductor 400 according to some other embodiments of the present disclosure is shown. The method includes providing a substrate. The substrate includes, but is not limited to, silicon (Si), silicon carbide (SiC), diamond, gallium nitride (GaN), etc. For illustration, consider a Si substrate 601. The Si substrate 601 can be cleaned according to the Piranha cleaning method and / or American Radio Corporation (RCA) cleaning.

[0072] In addition, the method includes depositing 603 a first layer 605 of ferromagnetic material (e.g., ferromagnetic oxide) on the clean Si substrate 601 using a deposition method (e.g., a pulsed laser deposition (PLD) method). Alternatively, in some implementations, MBE (molecular beam epitaxy), MOCVD (metal organic chemical vapor deposition), CVD (chemical vapor deposition), sputtering, or electron beam evaporation may be used to deposit the first layer 605 of ferromagnetic material. After the ferromagnetic material is deposited, the sample 607 may be annealed in an oxygen environment.

[0073] Furthermore, the method includes forming 609 a metal spiral 611 on the surface of the first layer 605 of ferromagnetic material using, for example, photolithography and / or a lift-off process. Photolithography involves the use of light to create a finely patterned thin film of a suitable material over a substrate.

[0074] Additionally, the method includes depositing 613 a second layer 615 of ferromagnetic material on the first layer 605 and the metal spiral 611 to completely immerse the metal spiral 611 in the ferromagnetic material. The second layer 615 of ferromagnetic material is deposited 613 using a PLD method.

[0075] The PLD method is a physical vapor deposition method that allows non-equilibrium and versatile growth of complex stoichiometries. PLD combines the characteristics of both evaporation and sputtering. Thin film deposition can be achieved using the PLD method. Thin film deposition is achieved by focusing a laser pulse on a target of desired stoichiometry and generating a plume containing atomic species of the target material deposited on a substrate. For example, in PLD, the laser pulse is guided and focused by high-quality quartz optical components, which allows the energy density on the target to be between 2-3 J / cm 2 The target point hit by the laser pulse heats up quickly and evaporates, and the vapor absorbs more energy from the laser pulse to decompose into a dense plasma. The dense plasma absorbs any remaining energy from the laser pulse and expands to produce a plume perpendicular to the target surface, depositing on a substrate placed directly above the target. The substrate can be rotated during deposition to ensure uniformity and low roughness of the film surface, and the target can be rotated and rastered during laser ablation and deposition to ensure uniform ablation of the target.

[0076] The following description provides only exemplary embodiments and is not intended to limit the scope, applicability or configuration of the present disclosure. Instead, the following description of exemplary embodiments will provide a feasible description for implementing one or more exemplary embodiments to those skilled in the art. It is contemplated that various changes may be made to the functions and arrangements of the elements without departing from the spirit and scope of the disclosed subject matter set forth in the appended claims.

[0077] Specific details are given in the above description to provide a thorough understanding of the embodiments. However, it will be appreciated by those of ordinary skill in the art that the embodiments may be practiced without these specific details. For example, the systems, processes, and other elements in the disclosed subject matter may be shown as components in block diagram form to avoid obscuring the embodiments in terms of unnecessary details. In other cases, well-known processes, structures, and techniques may be shown without unnecessary details to avoid obscuring the embodiments. In addition, similar reference numerals and designations in the various drawings indicate similar elements.

[0078] In addition, various embodiments may be described as processes, which are depicted as flow charts, data flow diagrams, structure diagrams, or block diagrams. Although flow charts may describe operations as sequential processes, many operations may be performed in parallel or simultaneously. In addition, the order of operations may be rearranged. A process may terminate when its operations are completed, but may have additional steps that are not discussed or included in the accompanying drawings. In addition, not all operations in any specifically described process may appear in all embodiments. A process may correspond to a method, a function, a program, a subroutine, a subprogram, etc. When a process corresponds to a function, the termination of the function may correspond to the function returning to the calling function or the main function.

[0079] Embodiments of the present disclosure may be embodied as a method, examples of which have been provided. The actions performed as part of the method may be ordered in any suitable manner. Thus, embodiments may be constructed that perform actions in an order different from that shown, which may include performing some actions simultaneously, although shown as sequential actions in the illustrative embodiments.

[0080] Although the present disclosure has been described with reference to certain preferred embodiments, it will be understood that various other adaptations and modifications may be made within the spirit and scope of the present disclosure. Therefore, the aspects of the appended claims cover all such changes and modifications that fall within the true spirit and scope of the present disclosure.

Claims

1. A negative inductor device, the negative inductor device include: a negative inductor comprising a ferromagnetic material and a conductive material disposed inside the ferromagnetic material; as well as A current limiting circuit is electrically coupled to the negative inductor and is configured to supply a current within a range defined by a first local minimum and a second local minimum of a current-energy curve of the ferromagnetic material.

2. The negative inductor device of claim 1, further comprising: include: A first terminal and a second terminal, the first terminal and the second terminal are electrically connected to the first end and the second end of the conductive material, respectively.

3. The negative inductor device according to claim 1, in, The ferromagnetic material has a first shape, the conductive material has a second shape, and the first shape of the ferromagnetic material surrounds the second shape of the conductive material such that a geometric center of the first shape coincides with a geometric center of the second shape.

4. The negative inductor device according to claim 3, in, Each of the first shape and the second shape is a symmetrical shape.

5. The negative inductor device according to claim 4, in, The first shape is a plate and the second shape is a spiral.

6. The negative inductor device according to claim 5, in, The cross-section of the lead wire includes one or a combination of circular, semicircular, rectangular and semi-rectangular shapes.

7. A negative inductor, the negative inductor include: Ferromagnetic materials; as well as A conductive material is partially enclosed in the ferromagnetic material such that opposite ends of the conductive material protrude from the ferromagnetic material, wherein the opposite ends of the conductive material protruding from the ferromagnetic material correspond to terminals of the negative inductor.

8. A negative inductor, the negative inductor include: Ferromagnetic materials; as well as A conductive material is arranged inside the ferromagnetic material.

9. A circuit comprising a positive inductor electrically connected in parallel with the negative inductor according to claim 8.

10. A circuit comprising a positive inductor electrically connected in series with the negative inductor according to claim 8.

11. A non-Foster impedance matching circuit, comprising the negative inductor according to claim 8 for impedance matching between a power amplifier (PA) and an antenna.

12. An artificial magnetic conductor comprising the negative inductor according to claim 8, the negative inductor according to claim 8 acting as a non-Foster element.

13. A method for manufacturing a negative inductor, the method comprising: The following steps are involved: depositing a first layer of ferromagnetic material on a substrate; forming a metal spiral on a surface of the ferromagnetic material of the first layer; as well as A second layer of the ferromagnetic material is deposited over the first layer of ferromagnetic material and the metal spiral.

14. The manufacturing method according to claim 13, in, The ferromagnetic material of the first layer and the ferromagnetic material of the second layer are deposited using pulsed laser deposition (PLD).

15. The manufacturing method according to claim 13, in, The metal spiral is formed on the surface of the ferromagnetic material of the first layer using photolithography.

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