114 results about "Lc resonant circuit" patented technology

The invention discloses a method and device for preventing inverter harmonic waves from affecting operation of an electric energy meter, and the method comprises the following steps: a harmonic attenuation device is installed on an inverter line bus, and the harmonic attenuation device comprises an LC resonance circuit and a control circuit; dynamically matching the winding inductor and the safety capacitor based on the harmonic frequency spectrum characteristic of the inverter; a temperature sensing module is integrated on the body of each power resistor branch; the MCU microcontroller judges whether to trigger power resistor branch switching or not based on the temperature data and a preset temperature control strategy; after a relay switching action is triggered, a dynamic compensation strategy is generated to dynamically adjust inductance, capacitance and resistance topology so as to realize frequency stabilization and impedance matching; and executing closed-loop feedback optimization and health assessment based on the harmonic suppression effect after dynamic compensation and the system operation state. The invention has the following advantages and effects: the dynamic tracking of the LC resonant frequency on the harmonic dominant frequency is realized, and the thermal runaway problem of the harmonic energy absorption unit is synchronously solved.

The utility model provides an electromagnetic heating system. The system comprises a filtering module, a rectification module, a current sampling module, an LC filtering module, an LC resonance circuit module, an IGBT switch tube, a zero-crossing signal generation module, a DC power supply voltage stabilization module, an MCU module and a display control module. According to the utility model, the power starting current can be reduced, and the instantaneous loss and electromagnetic noise of the switch tube can be reduced. During actual work, the zero-crossing signal generation module outputs a zero-crossing signal by detecting a zero-crossing point of an input alternating-current power supply, the MCU module outputs two discharge pulses directly generated by the MCU module to the IGBT switching tube at a falling edge of the zero-crossing signal, the LC resonant circuit module discharges, reduces IGBT-C pole voltage and then starts power, so that power starting current can be reduced, and power starting efficiency is improved. And the instantaneous loss and electromagnetic noise of the switching tube are reduced.

The invention relates to a DC / DC converter (1) for charging a battery (4) in a boost mode, wherein the DC / DC converter (1) has a primary side (P) and a secondary side (S), wherein on the primary side (P) and on the secondary side (S) a capacitance (CX_P, CX_S) is electrically coupled between a respective positive potential (HV+1, HV+2) and a respective negative potential (HV-1, HV-2), wherein - the primary side (P) and the secondary side (S) each have at least two half-bridges (HB1, HB2, HB3, HB4), each with a high-side switch designed as a semiconductor switch (S1, S3, S5, S7, D) and a low-side switch designed as a semiconductor switch (S2, S4, S6, S8), - LC resonant circuits (2.1, 2.2) designed as series resonant circuits are arranged between center taps of the half-bridges (HB1, HB2) on the primary side (P) and center taps of the half-bridges (HB3, HB4) on the secondary side (S), wherein exactly one of the potentials (HV+1, HV-1) of the primary side (P) is galvanically connected to the opposite pole potential (HV-2, HV+2) of the secondary side (S), wherein the other potential (HV-1, HV+1) of the primary side (P) is galvanically connected to a same pole battery terminal of the battery (4).

The invention relates to a DC / DC converter (1) comprising: - a primary side (P) with at least two half-bridges (HB1, HB2), each with a high-side switch designed as a semiconductor switch (S1, S3) and a low-side switch designed as a semiconductor switch (S2, S4), - a secondary side (S) with at least two half-bridges (HB3, HB4), each with a high-side switch designed as a semiconductor switch (S5, S7, D) and a low-side switch designed as a semiconductor switch (S6, S8, D), - at least one LC resonant circuit (2.1, 2.2) designed as a series resonant circuit, which is arranged between a center tap of one of the half-bridges (HB1, HB2) on the primary side (P) and a center tap of one of the half-bridges (HB3, HB4) on the secondary side (S), - at least one further LC resonant circuit (2.1, 2.2) designed as a series resonant circuit or a capacitor (C1, C2) which is arranged between a center tap of another of the half-bridges (HB1, HB2) on the primary side (P) and a center tap of another of the half-bridges (HB3, HB4) on the secondary side (S).

The invention belongs to the technical field of induction cookers, and discloses a low-power continuous electromagnetic heating technology and an induction cooker, the resonant frequency of an LC resonant circuit is designed to be greater than 18kHz, and a SiC MOSFET device works at a switching frequency higher than the resonant frequency, so that the low-power continuous electromagnetic heating technology is realized. The intermittent heating problem of'stop-start-stop-start 'caused by too small duty ratio during low-power heating of the existing induction cooker is effectively solved; according to the technical scheme, the power-duty ratio mapping data is obtained through the MCU module, and the duty ratio and the pulse width of the PWM signal are accurately calculated according to the target power, the target switching frequency and the timer clock frequency, so that continuous and stable energy output is realized under low power; the electromagnetic oven can effectively solve the problems of intermittent heating, unstable circuit work, increased energy consumption and noise of the existing electromagnetic oven during low-power heating.

An inductor for use as a passive electronic component. The inductor has a hollow ceramic tube, a metal target rod located inside the hollow ceramic tube, a coil wound on the outside of the hollow ceramic tube and including a first end and a second end, and a first terminal engaging the first end of the coil and a second terminal engaging the second end of the coil. The metal target rod is fixed relative to the coil at a position so that the inductor has a zero temperature coefficient. Also provided is an LC resonant circuit including the inductor.

The application discloses a bidirectional DCDC circuit and a photovoltaic energy storage inverter. The photovoltaic energy storage inverter is used for connecting a photovoltaic module, a battery and an alternating current end. The bidirectional DCDC circuit comprises a first direct current end, a second direct current end, a transformer, a first full-bridge circuit connected between the first direct current end and a primary side of the transformer, a second full-bridge circuit connected between a secondary side of the transformer and the second direct current end and a first capacitor. The first full-bridge circuit is directly connected with the primary side of the transformer and / or the second full-bridge circuit is directly connected with the secondary side of the transformer. The first capacitor is located between the second full-bridge circuit and the second direct current end and is connected with positive and negative poles of the second direct current end. The bidirectional DCDC circuit provided in the application uses leakage inductance of the primary side of the transformer and the first capacitor to form an LC resonant circuit instead of an LC resonant circuit arranged at two ends of the transformer, so that the function of the resonant circuit is realized while the number and volume of electrical elements of a topological structure are reduced, thereby reducing the cost.

The invention discloses a passive wireless temperature sensor with a bistable structure. The temperature sensor comprises a flexible porous dielectric layer, a metal electrode, a bistable structure beam, a beam end anchoring part, a bistable structure beam anchoring area, a metal wire, a planar inductor and a substrate. The bistable structural beam is bent upwards in an initial state and forms a plate capacitor with the metal electrode. And when the temperature reaches the lower limit temperature of the temperature interval, the bistable structural beam is changed into a downward bending shape from an upward bending shape. The sharp reduction of the distance between the bistable structural beam and the metal electrode causes the sharp increase of the capacitance value of the plate capacitor, so that the resonant frequency of an LC resonant circuit formed by the plate capacitor and the planar inductor suddenly changes, and the judgment of a temperature interval is realized. And in each temperature interval, the corresponding bistable structure beam continuously bends downwards and extrudes the flexible porous dielectric layer along with the rise of the temperature, so that the capacitance is changed, and the wide-range, temperature-zone-divided and high-precision continuous temperature measurement is realized.

A signal-radiation device utilizes a metal portion of a connection port as a wireless antenna, including an equipment-connecting port, a resonant capacitor and a high frequency isolation inductor required under certain circuit conditions; wherein the equipment-connecting port is disposed with a metal portion, and one end of the resonant capacitor is connected to the metal portion, and another end of the resonant capacitor is electrically connected to an antenna pin of a piece of wireless equipment; the metal portion and the resonant capacitor together form an LC resonant circuit. By adjusting shapes of a metal wire connected to the connection port and adjusting the capacitance of the resonant capacitor, the LC resonant circuit has an LC resonant frequency equal to a wireless operating frequency, wireless signals can be radiated through the metal portion of the equipment-connecting port which is suitable for wireless equipment with very-small-sized equipment-connecting port.

The application provides a non-invasive implantable wall deformation volume sensor, and relates to the technical field of implantable biomedical sensors, which comprises an elastically deformable closed ring-shaped base, a conductive coil arranged on the ring-shaped base, a capacitor forming an LC resonant circuit with the conductive coil, an elastic support structure arranged in the ring-shaped base, and a biocompatible encapsulation layer covering the outside. The sensor controls the distribution ratio and mechanical rigidity of the support structure, so that the ring-shaped base produces controllable concave deformation under the action of the pressure of the inner wall of an organ, thereby changing the geometric parameters of the conductive coil and causing the resonant frequency to change, and the detection of the volume change of the organ is realized. In addition, the elastic support structure and the ring-shaped base form a connection mode allowing relative sliding, so that the sensor can automatically expand by the elastic force after compression delivery. The application can respond to the overall geometric deformation, and has the advantages of simple structure and high mechanical compliance.

The invention discloses a wireless temperature sensor with a paper folding structure. The temperature sensor comprises a substrate, a planar inductor, a V-shaped beam, a substrate capacitor polar plate, a capacitor upper polar plate, a spring beam, the paper folding structure and a metal wire. When the temperature rises, thermal expansion of the V-shaped beam is caused, and then the capacitor upper polar plate is driven to move towards the two ends, so that the overlapping area between the capacitor upper polar plate and the substrate capacitor polar plate is increased, the capacitance value of the sensitive capacitor is increased, the resonant frequency of an LC resonant circuit formed by the sensitive capacitor and the planar inductor is reduced, and high-temperature measurement is realized. When the temperature is reduced, the V-shaped beam is contracted, the upper electrode plate of the driving capacitor moves towards the center, the paper folding structure protrudes upwards, the capacitance value of the sensitive capacitor is decreased, the resonant frequency of an LC resonant circuit composed of the sensitive capacitor and the planar inductor is increased, and low-temperature measurement is achieved. The temperature sensor has the advantages of simple structure, sensitive response, wide measuring range, process compatibility and the like.

The invention discloses an industrial power-saving system and method based on multi-frequency-band conflict avoidance and energy feedback, and relates to the technical field of industrial power-saving systems.The method comprises the steps that a power grid fundamental wave synchronizing signal is obtained through a zero-cross detection circuit, an integrating circuit is input to generate a slope time-base signal, and the time-base signal is used for controlling the triggering moment of a high-frequency modulation pulse; the method comprises the following steps: modulating a pulse to intensively act on wave crest and wave trough areas of an AC voltage waveform, exciting an LC resonant circuit connected to a DC side of an electric energy conversion device by the modulating pulse to enable the LC resonant circuit to enter a quasi-resonant state in a phase interval, and actively releasing energy to a load by an energy storage capacitor; the system is controlled to be switched on preferentially, power supply competition for a main power supply is formed, main current output is correspondingly reduced on the premise that load power is not changed, energy conservation and consumption reduction are achieved, and the system further improves electric energy quality and operation stability through unified clock synchronization, phase out-of-sequence control, energy local circulation and impedance frequency band avoidance.

The invention discloses a real-time self-driven wireless sensor based on a friction nano-generator. The real-time self-driven wireless sensor comprises the friction nano-generator, a discharging device, a sliding capacitive displacement sensor, an inductance coil and a receiving circuit, the sliding capacitive displacement sensor and the inductance coil form a parallel LC resonance circuit, and the friction nano generator supplies power to the LC resonance circuit through the discharge device; the sliding capacitive displacement sensor comprises an upper conductive flat plate and a lower conductive flat plate which are oppositely arranged, and at least one dielectric material layer located between the upper conductive flat plate and the lower conductive flat plate; the upper conductive flat plate is connected with a to-be-measured structure, the lower conductive flat plate is connected with the fixed end, and when the two conductive flat plates relatively displace, capacitance formed by the two conductive flat plates changes, so that the resonant frequency of the LC resonant circuit changes, and a mapping relation exists between the resonant frequency and displacement; the LC resonance circuit wirelessly transmits a resonance signal carrying displacement information, and the receiving circuit receives the resonance signal and analyzes the frequency to obtain the displacement information.

The invention relates to a double-pulse test method and a test circuit. The method comprises the following steps: providing a double-pulse test circuit; the double-pulse test circuit comprises an energy charging circuit and a resonance circuit, the resonance circuit is a half-bridge LC resonance circuit or a full-bridge LC resonance circuit, and the energy charging circuit comprises a power supply and a bus capacitor; the bus capacitor is charged through the power supply; in response to charging the bus capacitor to the target voltage, disconnecting the power supply from the bus capacitor and the resonant circuit; and applying a control voltage to the control ends of the upper bridge and the lower bridge in the resonant circuit, obtaining a gate-source voltage, a drain-source voltage and a drain-source current of each switching tube in the resonant circuit under the control voltage, and obtaining a test result according to the gate-source voltage, the drain-source voltage and the drain-source current. According to the invention, the characteristics of the MOS tube in the LLC converter during actual work can be analyzed. Based on the test result obtained by the method, an important reference basis can be provided for model selection of the primary MOS transistor of the LLC converter, and poor products caused by design errors and improper model selection are avoided.

A kind of planetary gearbox fault diagnosis method based on circuit resonator belongs to the field of planetary gearbox fault diagnosis. Including the following steps: piezoelectric sheet is connected in parallel with inductor, and an LC resonant circuit is formed. Then the piezoelectric sensor is pasted on the planetary gearbox shell, so that the piezoelectric sheet and the box are coupled as a whole. The time domain voltage signal between the capacitor ends in the resonant circuit when the planetary gearbox is running is collected, and then it is analyzed by resonance demodulation. No need to locate the resonance band through a series of algorithms, because the resonance frequency of the resonant circuit is known. The envelope order spectrum of the resonance band is obtained, and compared with various fault characteristic frequencies, so as to realize fault diagnosis. It can effectively avoid the interference of corresponding running of fixed shaft gear train and other components, and accurately extract the fault characteristics of planetary gear train.

This invention relates to an inductive sensor device for detecting changes in the position of an actuating element. The sensor device comprises: - an LC resonant circuit having an inductive element (L) and a capacitive element (C); - an excitation supply for exciting the LC resonant circuit by coupling an excitation voltage (U) to the LC resonant circuit; - a decoupling element arranged between the excitation supply and the LC resonant circuit; and - an evaluation device for evaluating signal attenuation in the resonant circuit. The invention also relates to an actuation device.

This invention relates to a circuit board for an ozone generator with frequency tracking functionality. The circuit board includes a frequency tracking circuit comprising an RC oscillation unit, an LC resonant unit, a current sampling unit, a comparison control unit, a voltage divider bias unit, and a frequency limiting protection unit. The LC resonant unit includes a resonant inductor T1 and a resonant capacitor C1, used to drive the ozone sensor. The current sampling unit includes a sampling resistor R8 connected in series in the LC resonant circuit, used to acquire the circuit current signal. The comparison control unit includes a comparator U1, a transistor Q1, a rectifier diode D2, and a filter capacitor C3. The voltage signal from the sampling resistor R8 is rectified by D2 and filtered by C3 before being input to the inverting input of U1. The voltage divider bias unit includes resistors R3 and R6. The RC oscillation unit is connected to the transistor Q1. This invention can adapt to capacitance changes during ozone sensor power-on and operation, automatically tracking the frequency and achieving resonance, while ensuring stable output power, extending device lifespan, and improving ozone generation efficiency and overall reliability.

The present application relates to the technical field of radio frequency power supplies, and to an improved class D power amplifier, a power amplifier control method, a radio frequency power supply, and a power supply method, for use in solving the problem of impedance matching. A circuit at an output end of the class D power amplifier comprises multiple stages of LC resonant circuits; the multiple stages of LC resonant circuits comprise at least one stage of LC resonant circuit in which a controlled switch is configured in two ways, i.e., connected in parallel to an inductor and connected in series to a capacitor; the LC resonant circuits connected to the class D power amplifier are controlled by controlling the switch state of the controlled switch, to perform output impedance matching of the class D power amplifier. According to the present application, related inductors and capacitors are enabled and shielded on the basis of power output requirements, to form LC single-stage or multi-stage resonant topology meeting different requirements, thereby achieving impedance matching of the class D power amplifier.

The invention discloses a low-profile band-pass frequency selective wave-absorbing surface with broadband wave absorption. The low-profile band-pass frequency selective wave-absorbing surface comprises a resistance loss layer, an air layer and a band-pass FSS transmission layer in sequence from top to bottom, the resistance loss layer comprises a first dielectric substrate, a central metal sheet is printed at the center of the upper surface of the first dielectric substrate, an etching groove is etched in the central metal sheet, a parallel LC resonance circuit is formed through the etching groove, the periphery of the central metal sheet is connected with metal bridge arms which are symmetrically distributed in a central rotation mode and extend outwards, and the metal bridge arms are connected with the first dielectric substrate. The tail end of each metal bridge arm is connected with a circular metal sheet which takes the midpoint of the tail end of the metal bridge arm as a circle center, and lumped resistors are loaded on the metal bridge arms; through the single resistance loss layer, loading of the lumped resistor and special slotting of the resistance loss layer, broadband wave absorption with a band-pass window can be realized by using a two-dimensional structure, and the broadband wave absorption device has the characteristics of low profile, easy processing, flexible regulation and control and the like.

The invention provides a high-suppression passive reconfigurable intermediate-frequency filter based on a GaAs process, which comprises a high-order reconfigurable low-pass filter unit and a high-order reconfigurable high-pass filter unit which are in cascade connection, and is characterized in that the high-order reconfigurable low-pass filter unit is designed based on a seven-order low-pass elliptic function prototype and comprises a series branch and a parallel branch; the parallel branch comprises an adjustable capacitor and an inductor connected in series, bandwidth mode switching is achieved by adjusting the position of a transmission zero point, a fixed LC resonance circuit is introduced into the series branch to generate a fixed transmission zero point, and out-of-band rejection is enhanced; the high-order reconfigurable high-pass filter unit is designed based on a seven-order high-pass elliptic function prototype and comprises a series capacitor and a parallel grounding branch, and the parallel grounding branch comprises an inductor and an adjustable capacitor which are connected in series and is used for introducing a transmission zero point of a low-frequency stop band. According to the scheme, low insertion loss is kept while bandwidth mode switching is achieved, and the far-end out-of-band rejection capacity is remarkably improved.

The invention relates to the technical field of communication equipment, and discloses a frequency hopping filter with a hopping transmission zero point, a hopping control method and communication equipment. At least one resonant inductor of an LC resonant circuit of the frequency hopping filter is connected with a radio frequency switch feedback capacitor array in parallel; the frequency of a transmission zero point at a higher harmonic of the frequency hopping filter is controlled by controlling the opening and closing of a channel where each feedback capacitor in the radio frequency switch feedback capacitor array is located, so that the frequency of the transmission zero point changes along with the center frequency of the frequency hopping filter; and finally, far-end suppression, relative bandwidth stability and frequency hopping accuracy in a wide frequency range are improved.

The utility model relates to a high-precision high-voltage charging control device, which comprises an LC filter circuit, a full-bridge inverter circuit, an LC resonance circuit, a boosting transformer, a rectifying circuit, a load, a voltage divider, a signal conditioning circuit, an AD sampling circuit, a processing chip and a driving circuit. The bus input end is connected with the full-bridge inverter circuit through the LC filter circuit, the full-bridge inverter circuit is connected with the step-up transformer through the LC resonant circuit, and the step-up transformer is connected with the load through the rectifying circuit. The voltage divider is connected with a load, the voltage divider is connected with the AD sampling circuit through the signal conditioning circuit, the AD sampling circuit is connected with the processing chip, and the processing chip is connected with the full-bridge inverter circuit through the driving circuit. According to the high-precision high-voltage charging control device, feedback control is performed on the charging circuit after feedback signals are processed through the processing chip, so that the load state is monitored in real time, charging parameters are automatically adjusted, the safety and the high efficiency of the charging process are ensured, and high-power and high-precision charging control is realized.

The invention discloses a wide-range passive wireless temperature sensor with a push-pull structure. The temperature sensor comprises a substrate, a planar inductor, a V-shaped beam, the push-pull structure, an interdigital capacitor and a metal wire. When the temperature rises, thermal expansion of the V-shaped beam is caused, then the push-pull structure driving rod is driven to output displacement in the X-axis direction, the honeycomb type hexagonal structure is expanded, the bow-tie type hexagonal structure is contracted, the capacitance value of the second interdigital capacitor is increased, the resonant frequency of an LC resonant circuit composed of the interdigital capacitors and the planar inductor is decreased, and high-temperature measurement is achieved. When the temperature is reduced, the V-shaped beam is contracted, the bow-tie-shaped hexagonal structure is expanded, the honeycomb-shaped hexagonal structure is contracted, the capacitance value of the first interdigital capacitor is reduced, the resonant frequency is increased, and low-temperature measurement is achieved. The temperature sensor has the advantages of simple structure, sensitive response, wide measuring range, process compatibility and the like.

The utility model provides a kind of RF and EMS common circuit, including high frequency radio frequency circuit, RFADC skin detection circuit, EMS circuit, EMS and RF isolation circuit, the RF power supply of high frequency radio frequency circuit is provided by DC-DC boost, high frequency radio frequency circuit receives the high frequency signal RFIN input by MCU, through MOS tube Q1 drive LC resonant circuit, in RF output point generation with the AC RF signal of RFIN same frequency, signal amplitude is decided by VCC-RF;RFADC skin detection circuit input end is connected with the output end of high frequency radio frequency circuit, whether contact skin is judged by detecting the voltage change of RFADC detection point when contact skin.The utility model has the beneficial effects that:1.The utility model's EMS and RF isolation circuit use inductance to isolate the interference of RF radio frequency circuit, to realize the common use of RF and EMS technology;2.It can realize 3MHZ above RF radio frequency.

The present disclosure provides a wireless power transmission device comprising an impedance matching circuit. The wireless power transmission device of the present disclosure may include: a transistor that outputs a signal corresponding to a set operating frequency based on an input signal and a driving voltage; a matching circuit connected to the transistor and converting the impedance of the signal corresponding to the operating frequency; a transmitting coil connected to the matching circuit; an LC resonant circuit connected in parallel between the transistor and the matching circuit and transmitting a signal corresponding to at least one harmonic frequency of the operating frequency; and an impedance sensing circuit connected to the LC resonant circuit and sensing the load impedance of the wireless power transmission device based on the signal corresponding to the at least one harmonic frequency transmitted through the LC resonant circuit. Various other embodiments of the wireless power transmission device comprising the impedance matching circuit of the present disclosure may be applied.

The application provides a controller and an electromagnetic handwriting device. The controller comprises a rotating wheel assembly and a transceiving unit. The rotating wheel assembly comprises a rotating wheel. The transceiving unit comprises an LC resonant circuit. The transceiving unit is accommodated in the rotating wheel assembly, so that the rotating wheel drives the transceiving unit to rotate.

The invention discloses a floating type multi-parameter water quality monitoring microsystem and a preparation method thereof, and belongs to the technical field of water quality monitoring. The water quality monitoring microsystem sequentially comprises a functional floating carrier substrate, a flexible circuit module and an insulating packaging layer from bottom to top, the flexible circuit module comprises a flexible insulating dielectric layer, a planar spiral inductance coil is arranged on the upper surface of the flexible insulating dielectric layer, and a plurality of interdigital electrodes are arranged on the lower surface of the flexible insulating dielectric layer; each interdigital electrode is connected with the planar spiral inductance coil to form an LC resonant circuit of which the working frequencies are not overlapped; the surfaces of the interdigital electrodes are coated with ion sensitive membranes respectively; a through detection window is formed in the position, corresponding to the interdigital electrode, of the functionalized floating carrier substrate, so that the interdigital electrode can be directly contacted with a water body to be detected below through the detection window; and the insulating packaging layer completely covers the planar spiral inductance coil. The system can be used for monitoring water quality, and has the advantages of good real-time performance, high detection precision and the like.

The application discloses a structure for suppressing multiple reflections of radar internal beams, comprising at least one set of rectangular patch groups, which are arranged in three rows and three columns on an antenna board; the design method comprises the following steps: determining the in-phase reflection phase band gap position of the rectangular patch group structure according to a preset RCS frequency band; designing the initial size of the rectangular patch group structure according to an equivalent LC resonant circuit formula of the rectangular patch group structure and the geometric size of the antenna; ensuring that at least three complete rectangular patch groups are used; and optimizing the calculation of the in-phase reflection phase band gap of the rectangular patch group structure until the band gap completely covers the RCS reduction frequency band of the antenna. The application reduces the multiple reflections of the radar internal beams through the design of the rectangular patch group structure, and improves the signal-to-noise ratio of the radar; the rectangular patch group structure is simple and easy to process, and the problems of complex process and high cost caused by the grounding hole processing are overcome.

The invention provides a capacitance measurement method and a capacitance measurement system based on double LC resonance circuits, which are applied to the technical field of laser cutting, and are characterized in that a reference circuit and a measurement circuit are arranged in the same environment and are LC resonance circuits with the same structure; the capacitance value measuring method of the to-be-measured capacitor comprises the following steps: S1, collecting the oscillation frequency of a reference circuit; s2, based on the circuit structure of the reference circuit and the oscillation frequency of the reference circuit, calculating the actual value of the inductance in the resonant circuit of the reference circuit, namely obtaining the actual value of the inductance in the resonant circuit of the measuring circuit at the current temperature; and S3, calculating the actual value of the capacitor to be measured in the measuring circuit at the current temperature based on the circuit structure of the measuring circuit, the oscillation frequency and the actual value of the inductor in the resonant circuit of the measuring circuit. A double-LC resonance circuit is used and comprises a reference circuit and a measuring circuit, so that the problem that capacitance measured by a single oscillation circuit is inaccurate due to temperature excursion can be solved.

A filter circuit is located in a dielectric substrate and includes multiple dielectric layers and a pass band in a range higher than a predetermined frequency. The dielectric substrate includes first and second major surfaces facing each other. External terminals for connection with an external device are on the second major surface. The filter device includes a first terminal, a second terminal, and first and second resonant circuits. The first resonant circuit is connected between the first and second terminals. The second resonant circuit is connected between the first resonant circuit and a ground potential. Each of the first and second resonant circuits includes an LC resonant circuit including a capacitor and an inductor. In the dielectric substrate, a portion of an inductor in the second resonant circuit is on or in a dielectric layer between the first major surface and inductors included in the first resonant circuit.