100 results about "Electrical length" patented technology

An antenna assembly, an electronic device main body, an electronic device, a storage medium and a control method of the electronic device, the antenna assembly comprises a circuit board, a main radiator, a parasitic radiator and a switching circuit, the main radiator is connected with a feed circuit of the circuit board, and the parasitic radiator is connected with the switching circuit. And the switching circuit is used for enabling the main radiator to feed the parasitic radiator under the conduction condition, and the switching circuit is used for enabling the main radiator not to feed the parasitic radiator under the turn-off condition. The parasitic radiator is controlled by the switching circuit, and the switching circuit can enable the main radiator to feed the parasitic radiator, so that the electrical length of the antenna assembly can be increased, and the antenna efficiency of the antenna assembly can be improved. In some application scenarios, if the parasitic radiator participates in radiation, the antenna performance is deteriorated, and the parasitic radiator can be controlled not to participate in radiation of wireless signals through the switching circuit, so that the antenna assembly can maintain better antenna performance in various application scenarios.

A Doherty amplifier according to the present disclosure comprises a main amplifier, an auxiliary amplifier, a distribution circuit that distributes signals to the main amplifier and the auxiliary amplifier, and a phase compensation circuit. The main amplifier has a first input matching circuit and a plurality of main amplification stages. The auxiliary amplifier has a second input matching circuit and a plurality of auxiliary amplification stages. The distribution circuit has a first line connected to the first input matching circuit and a second line connected to the second input matching circuit. The electrical length of the first line is such that the input impedance of the first line is higher than the characteristic impedance of the first line and the imaginary component is less than 10% of the real component when a small signal is input. The electrical length of the second line is such that the input impedance of the second line is higher than the characteristic impedance of the second line and the imaginary component is less than 10% of the real component when a small signal is input. The phase compensation circuit is provided in an inter-stage matching circuit of the plurality of main amplification stages or the plurality of auxiliary amplification stages.

The application discloses a terahertz metasurface reflection unit based on a MEMS switchable delay line, and belongs to the field of radio frequency front-end devices.The unit adopts a sandwich structure of upper and lower glass substrates and a middle bonded metal surface, and a metal radiation patch, a phase delay line and a MEMS switch are integrated on the upper surface.The core is to control the on-off state of the phase delay line through the MEMS switch: when the switch is turned off, the unit is in a reference electrical length;when the switch is turned on, the current path is lengthened, so that the reflection phase lags by about 180 degrees, thereby realizing 1-bit phase coding.The design ingeniously combines the MEMS switch and the delay line, has the advantages of low driving voltage, low reflection loss and high phase control precision in the terahertz frequency band, and provides a feasible hardware solution for the practical application of a reconfigurable intelligent surface in a terahertz communication system.

The invention discloses a quasi-true time delay broadband beam forming network with Chebyshev amplitude distribution. The quasi-true time delay broadband beam forming network comprises a 3 * 4 beam forming network, a 4 * 4 true time delay network, an input port, an output port and the like. The 3 * 4 beam forming network comprises first to tenth parallel double-line couplers, first to seventh open-short circuit stub loading transmission lines and first to fourth 50-ohm transmission lines; the 4 * 4 real time delay network comprises first to eleventh real time delay circuits and first to fourth connecting lines. Broadband Chebyshev amplitude output is obtained by setting different coupling coefficients of the first to tenth parallel double-line couplers. In-band flat phase difference output is obtained by setting phase shift values of the first to fourth 50-ohm transmission lines, phase shift values of the first to seventh open-short circuit stub loading transmission lines and impedance values and electrical lengths of the open-short circuit stubs; through controlling the first to eleventh true time delay circuits, the phase slope between the output ports has a frequency-dependent characteristic, and after the antenna is connected, a consistent beam direction in a broadband range is obtained.

Embodiments of the present application relate to an amplifying device and a transmitter. An amplifying device and a transmitter capable of compensating for a parasitic component of a circuit element without complicating a circuit structure are provided. The amplifying device includes a first amplifier that performs an amplifying operation on a signal; N-1 second amplifiers that perform an amplifying operation on the signal in sequence according to an amplitude of the signal in a case where the first amplifier performs the amplifying operation; N input networks connected to an input terminal that inputs the signal; N output networks connected between an output node of the first amplifier and a load connection node and connected between output nodes of the N-1 second amplifiers and the load connection node; and a first bias network that supplies a direct current bias voltage to at least one of the N output networks, an electrical length of the first bias network being less than 90 degrees.

The utility model discloses a microstrip patch antenna which comprises a dielectric substrate and a radiation patch. The radiation patch is arranged on the dielectric substrate, the radiation patch is E-shaped, the parallel edge of the E-shaped radiation patch is defined as a first sub-radiation patch, the vertical edge of the E-shaped radiation patch is defined as a second sub-radiation patch, and the length of the first sub-radiation patch is larger than or equal to 2.1 mm and smaller than or equal to 2.5 mm. The E-shaped structure enables the current to bypass between the first sub radiation patch and the second sub radiation patch, which is equivalent to increasing the electrical length of the radiation patch and reducing the resonant frequency of a fundamental mode, so that the low-frequency band bandwidth is broadened; the edges of the first sub-radiation patch and the second sub-radiation patch can generate strong electromagnetic field coupling to excite an additional parasitic resonance mode, so that the frequency band is further widened, and the bandwidth of the microstrip patch antenna is effectively widened. Wherein the first sub radiation patch of 2.1 mm to 2.5 mm enables the resonant frequency of the microstrip patch antenna to range from 43.7 Ghz to 55.1 Ghz, the relative bandwidth is 23%, and high bandwidth is achieved.

Embodiments of the present application provide a calibration device, a differential clamp, and related devices and systems. The calibration device includes a non-equivalent length reflection calibration piece for calibrating a scattering parameter of a differential signal obtained based on the differential clamp. The non-equivalent length reflection calibration piece includes a first line and a second line. An electrical length of the first line is not equivalent to an electrical length of the second line. A difference between a length of the first line and a length of the second line is within a preset range. The preset range is determined based on a bandwidth of the differential signal. Embodiments of the present application can accurately obtain the scattering parameter of the differential signal in the case of using the differential clamp.

The invention belongs to the field of superconducting receiving, and provides an HTS filter based on a full-wavelength resonator in order to improve the power capacity of the HTS filter, the HTS filter comprises a dielectric substrate, an HTS film is deposited on the first surface of the dielectric substrate, and a grounding metal layer is arranged on the second surface opposite to the first surface; the microstrip resonant structure is formed on the HTS thin film of the dielectric substrate and comprises at least two full-wavelength resonators, the adjacent full-wavelength resonators realize electromagnetic coupling through a gap, and the equivalent electrical length of each full-wavelength resonator is a waveguide wavelength corresponding to the working center frequency of the HTS filter; and the input port and the output port are respectively coupled with the full-wavelength resonator on the outermost side in the micro-strip resonant structure through micro-strip feeder lines. According to the technical scheme, the full-wavelength resonator structure with the equivalent electrical length as the waveguide length is adopted, so that the radio-frequency current can be redistributed along a longer resonance path, and the power capacity of the HTS filter is improved on the premise that the device size and the manufacturing complexity are not remarkably increased.

Provided is an electronic device including an antenna for performing wireless communication, a noise source that causes generation of radiation current, and a conductive member that is disposed on a propagation path of the radiation current from the noise source to the antenna and has a projecting portion projecting from the propagation path. An electrical length to a tip end of the projecting portion is equal to or larger than one-eighth but equal to or smaller than three-eighths of a wavelength used in the wireless communication.

The application discloses a balanced-to-balanced coaxial line impedance transformer, and belongs to the electronic technical field.The coaxial line impedance transformer is composed of four coaxial lines with the same characteristic impedance and electrical length, the coaxial line has an inner conductor and an outer conductor, the coaxial line impedance transformer has two balanced radio frequency ports Z L and Z H , and the 2.25:1 Z H / Z L impedance transformation ratio is realized by connecting the inner conductor and the outer conductor between different ports of the four coaxial lines.The application breaks through the minimum impedance transformation ratio of 4:1 that can be realized by the prior art, can satisfy the impedance transformation requirement below 4:1, can be combined with other impedance transformers to realize the impedance transformation ratio with smaller discrete value, is helpful to the miniaturization, low insertion loss and multi-path power synthesis scheme, and can satisfy the high power and high efficiency application demand above 2kW.

This invention discloses an electrically tuned high-power telescopic antenna system and method for use in an electromagnetic reverberation chamber. The system includes a base unit with a telescopic antenna rod slidably connected to it. The telescopic antenna rod's electrical length can be adjusted by changing its extension length to accommodate resonance requirements at different test frequencies. An electrically driven mechanism is installed within the base unit, with its power output connected to the telescopic antenna rod. The telescopic antenna rod is electrically connected to an RF feed unit for feeding external RF power into the telescopic antenna rod. A position feedback sensor is installed in the base unit. A control unit is optically connected to the electrically driven mechanism and the position feedback sensor, forming a closed-loop control based on the signal from the position feedback sensor. This invention achieves good impedance matching within the 30MHz–80MHz frequency band, solving the problem of severe mismatch in this band with existing antennas. It provides precise tuning, good matching, and ensures that the VSWR meets test requirements across the entire frequency band.

The low-profile dual-polarized omnidirectional full-duplex antenna comprises a vertical omnidirectional antenna unit, a horizontal omnidirectional antenna unit and a second horizontal dielectric substrate, wherein a metal floor is printed on the lower surface of the second horizontal dielectric substrate; a first radiation arm and a second radiation arm which are connected through metalized via holes are printed on two plate surfaces of two crossed dielectric substrates in the vertical omnidirectional antenna unit respectively; a plurality of rectangular grooves which are arranged in a radial manner are etched in the metal floor; the horizontal omnidirectional antenna unit is connected with the metal floor through four metal columns. The four metal columns can enable coupling current generated by the vertical omnidirectional antenna unit to the horizontal omnidirectional antenna unit to be short-circuited to the metal floor, the electrical length of the vertical omnidirectional antenna unit is increased, meanwhile, a plurality of rectangular grooves which are formed in the metal floor in a radioactive mode are etched, radial surface current can be blocked, and the coupling current is reduced. Omnidirectivity of the horizontal antenna is guaranteed, the profile height of the antenna is reduced, and the radiation arms on the two surfaces of the two vertical dielectric substrates improve isolation between antenna ports.

A retroreflective antenna according to one embodiment includes: an antenna main body for retroreflecting incoming radio waves; and a passive notch filter, in which the antenna main body includes a plurality of pairs of antenna elements, and a plurality of transmission lines provided corresponding to the plurality of pairs of antenna elements, each pair of antenna elements in the plurality of pairs of antenna elements is disposed point-symmetrically with respect to a reference point in the antenna main body, each of the plurality of transmission lines connects corresponding pair of antenna elements among the plurality of pairs of antenna elements, electrical lengths of the plurality of transmission lines are the same, and the passive notch filter is provided in at least one transmission line among the plurality of transmission lines.

An antenna radiation arm, an antenna radiation unit and a multi-frequency array antenna, each pair of dipoles of the antenna radiation unit comprises two oppositely arranged antenna radiation arms, the antenna radiation arms have a ring-shaped conductive structure, and an inductive circuit structure is arranged on the conductive structure to extend the electrical length of the conductive structure, which realizes the miniaturization of the physical size on the one hand, and enables the antenna to pass through the first frequency band signal and filter out the second frequency band signal on the other hand, reduces the mutual coupling between the array elements in the design environment with limited array height and space, and reduces the influence of the low-frequency antenna on the high-frequency antenna radiation performance. The antenna radiation arm comprises a driving arm and a parasitic arm, the driving arm is connected to a feed balun and has two radiation branches; the two ends of the parasitic arm are opposite to the two radiation branches of the driving arm, and enclose the ring-shaped conductive structure; the two radiation branches of the driving arm are coupled to the two ends of the parasitic arm through a capacitive structure, and form a resonance to the first frequency band signal, thereby widening the impedance bandwidth.

Tunable distributed oscillators (DOs) with flexible electrical length and associated systems, components, and devices are disclosed. In one aspect, a DO may include a plurality of DO units coupled in series. An individual DO unit includes a transmission-line segment having first and second ends and a middle portion between the first end and the second end. The DO unit further includes a first oscillator coupled with the first end, a second oscillator coupled with the second end, a first inductive matching circuit coupled between the first oscillator and the middle portion, and a second inductive matching circuit coupled between the second oscillator and the middle portion. By tuning the inductance or effective reactance of the first and second inductive matching circuits, the phase response of the DO unit may be adjusted so that the effective electrical length of the transmission-line segment is shortened relative to its physical length.

The utility model discloses a multifunctional microminiature constant-amplitude in-phase high-speed integrated connector, which comprises a shell, a mounting plate, N coaxial assemblies, a base, a shielding reed and a mounting screw, a shielding groove is formed in the front surface of the shell, interface mounting holes are formed in two ends of the shielding groove, a shell convex groove is formed in the middle of the shielding groove, and one end of the shell convex groove adopts large-arc transition while the other end adopts small-arc transition as a dual anti-misplug design; the mounting plate is arranged in the convex groove of the shell and is used for fixing the coaxial assembly; a shielding reed is arranged in a shielding groove of the shell; the base and the shell are connected through mounting screws to form a high-speed integrated connector; the user panel is fixed at the front end of the shell through mounting screws; coaxial contact pieces of different coaxial assemblies are connected in a bending mode through semi-rigid cables with the same physical length and the same electrical length, so that the equal-amplitude in-phase performance of the connector is guaranteed. The connector can realize transmission of multiple paths of high-speed serial differential signals or radio frequency integrated signals, and has the characteristics of integration, high density, strong shock resistance and high rate.

This invention belongs to the field of cable assembly phase matching technology, specifically relating to a method for precise phase synchronization of radio frequency cable assemblies. The invention includes steps such as initially calculating the cable length and cutting the cable; determining the accurate value of the dielectric constant of the cable insulation medium; and assembling the assembly and precisely adjusting the phase matching. This invention ensures that the electrical length and phase remain consistent after the phase matching operation, and can be precisely adjusted according to system design requirements.

This invention discloses a method for operating in a circular waveguide TE 11 This invention relates to a millimeter-wave high-power rotating reflective waveguide phase shifter, belonging to the field of millimeter-wave transmission technology. It comprises a rectangular waveguide wide-side slot 3dB coupler, a rectangular-circular waveguide transition section, and a rotating circular waveguide phase shifting section, with its central plane divided into two symmetrical microwave channels. Electromagnetic waves are first injected through the first port of the rectangular waveguide wide-side slot 3dB coupler, then split into two paths entering the rectangular-circular waveguide transition section through the third and fourth ports of the coupler, and subsequently injected into the rotating circular waveguide phase shifting section. After propagating a certain distance within the two phase shifting waveguides, the waves are reflected by a rotating metal plate piston and finally output from the second port of the rectangular waveguide wide-side slot 3dB coupler. This invention modulates the phase at the output end by changing the electrical length of the electromagnetic wave propagating within the phase shifting section by rotating the position of the metal plate piston. Within the same operating frequency band, it possesses advantages such as high power capacity, compact structure, high phase shifting accuracy, and a large phase shifting range.

An EDA method, device and equipment based on Smith gradual transmission line, the scheme firstly acquires the matching path on the Smith circle diagram, discretizes the matching path, then adopts the generalized reflection coefficient circle to fit the discretized matching path, determines the characteristic impedance and electrical length of the transmission line corresponding to the generalized reflection coefficient circle based on the center coordinates of each generalized reflection coefficient circle obtained by fitting and the intersection of the generalized reflection coefficient circle and the matching path, finally cascades the characteristic impedance and electrical length of the transmission line corresponding to each generalized reflection coefficient circle obtained by fitting, takes the cascaded result as the gradual transmission line and outputs. In the scheme, the calculation mode of the transmission line is realized based on the Smith circle diagram, and the Smith circle diagram can be easily constructed in the EDA design tool, which greatly facilitates the design work of the technical personnel.

The application relates to the technical field of microwave radio frequency devices, in particular to an ultra-wideband miniaturized balun based on an integrated defect ground structure. The balun comprises top layer metal, upper layer dielectric, middle layer metal, lower layer dielectric and bottom layer metal which are stacked in sequence from top to bottom, wherein the top layer metal is a signal transmission and function realization layer, is used for forming a single-ended input microstrip feed network and a symmetrical differential output microstrip structure, and comprises a step impedance section and a local patch to adjust the equivalent electrical length and the wideband amplitude and phase consistency. Through the stacked architecture of "top layer step impedance resonator-middle layer dielectric integrated defect ground structure slow wave unit-bottom layer complete ground", while maintaining the realization possibility of the planar PCB process, the dielectric integrated defect ground structure is introduced to constrain and slow the electromagnetic field, so that the equivalent electrical length is significantly compressed and the realization efficiency of the wideband balanced conversion is improved.

The invention provides a solid-state power source power amplifier fault isolation system and a superconducting accelerator, and belongs to the technical field of accelerators, the system comprises a radio frequency isolation synthesizer and a plurality of last-stage power amplifier modules; the radio frequency isolation synthesizer comprises a Gysel power synthesis network and a plurality of isolation loads; the final-stage power amplifier module is correspondingly connected with the synthesis input end, and the Gysel power synthesis network performs power synthesis on radio-frequency signals output by the final-stage power amplifier module and outputs the radio-frequency signals through the synthesis output end; the Gysel power synthesis network comprises a plurality of synthesis network branches, each synthesis network branch comprises a plurality of transmission lines with the same electrical length and quarter wavelength, and the characteristic impedances of the plurality of transmission lines are different from each other; the isolation load is correspondingly connected with the synthesis network branches, and the isolation load absorbs crosstalk radio frequency power from other synthesis network branches when the last-stage power amplifier module of the corresponding synthesis network branch breaks down. According to the invention, fault isolation is realized to prevent fault overflow and support safe hot plug.

The application provides an antenna regulation method, a micro pump, a device and related equipment, wherein the method comprises: obtaining first information under a current state of an antenna, the first information comprising at least one of a current return loss curve of the antenna and a current electrical length of the antenna; comparing the first information with reference information to obtain a comparison result; and regulating the electrical length of the antenna by the micro pump according to the comparison result. In this way, by comparing the first information under the current state of the antenna with reference information corresponding to target information, and regulating the electrical length of the antenna by the micro pump according to the comparison result, the terminal can realize multi-band coverage without placing multiple antennas, i.e. the internal space of the terminal device, which is already crowded, will not become more crowded due to the placement of multiple antennas of different frequency bands in the terminal, so that coupling between the antennas is avoided, thereby improving the communication performance of the terminal device.

The present application discloses an electronic device, comprising: a metal frame body and a second antenna radiator. A first side edge of the metal frame body is provided with a first break slit, a second side edge of the metal frame body is provided with a second break slit, and a part of the metal frame body between the first break slit and the second break slit forms a first antenna radiator, which is used to work in a first frequency band. The second antenna radiator is located on an inner side of the metal frame body, is disposed along the first side edge, and is used to work in a second frequency band. A coupling gap is provided between the second antenna radiator and the first antenna radiator. The first antenna radiator is provided with a first grounding point and a first feeding point, a radiator electrical length from the first feeding point to a first end being greater than an electrical length of the second antenna radiator. A radiator length from the first grounding point to the first end is less than a radiator length from the first feeding point to the first end. The first end is an end located at the first side edge, a second end is an end located at the second side edge, and the first side edge and the second side edge are adjacent to one another.

The present invention discloses a transmission line with electrical length markings, its continuous marking method, and a transmission line assembly. On the outer surface of the transmission line, a plurality of electrical length markings with intervals are formed along the length direction of the transmission line itself. The distance between adjacent markings corresponds to the propagation distance of the signal within a preset time unit d. The electrical length τ satisfies τ = (n - 1)·d + ε, where n is a natural number greater than or equal to 2, 0 ≤ ε < d, and the number of markings corresponds to the integer index n. During manufacturing, the continuous wire is placed on a production line with tension control, the displacement is measured by a grating, and the phase is measured by a non-contact capacitive probe in cooperation with a vector network analyzer. The electrical length at each position is calculated, and the marking module is driven at a d interval to continuously mark and shipped in rolls. In this way, the electrical length of the transmission line can be identified, recorded, and circulated. During assembly, it is cut according to the physical length or electrical length. The number of electrical length markings N of each wire segment is equal to each other, and the electrical length markings at both ends are aligned, so as to achieve the consistency of the propagation time between differential pairs and between multiple channels.

The utility model relates to the technical field of antennas, in particular to a single-layer single-feed double-frequency GPS antenna, which comprises a dielectric substrate, a radiation patch arranged on the upper layer of the dielectric substrate and a feed point arranged on the radiation patch, and is characterized in that the radiation patch is of a rectangular structure with the length of Y and the width of X, so that the radiation patch has the length direction Y and the width direction X; an L-shaped slot is formed in the radiation patch, the L-shaped slot comprises a first slot section extending in the X direction and a second slot section extending in the Y direction, the width of the slot is a, the L-shaped slot enables the propagation path of current in the X direction to be prolonged, the effective electrical length Z in the X direction is smaller than the physical width X, and the physical length Y in the Y direction is kept unchanged; the compact space layout of the GPS antenna is improved, the strict requirements of numerous novel electronic devices for compact space layout are met, the competitiveness of the product in the market is enhanced while the space utilization rate of the product is improved, and a new way is opened up for wide application of the GPS antenna in modern electronic devices.

To miniaturize a plurality of antennas to which power is supplied independently of each other.SOLUTION: The antenna includes a first conductor including a first end portion, an intermediate portion, and a second end portion, a second conductor including one end portion connected to the intermediate portion and the other end portion connected to a ground, a first feeding portion configured to input and output a first signal having a wavelength λ 1 to and from the first conductor at a first feeding position, and a second feeding portion configured to input and output a second signal having a wavelength λ 2 to and from the first conductor at a second feeding position. A first section from the second end portion to the other end portion via the intermediate portion has an electrical length of λ 1 * (1 / 8) or more and λ 1 * (3 / 8) or less, a second section from the second feed position to the other end portion via the intermediate portion has an electrical length of λ 2 * (1 / 8) or more and λ 2 * (5 / 8) or less, and the second conductor has a width of λ 1 * (1 / 16) or less.SELECTED DRAWING: Figure 2

The application relates to a system and method for plasma processing. The system comprises a base, a gas delivery device and a full-wavelength spiral resonance device; wherein the full-wavelength spiral resonance device comprises n reaction cavities, n induction coils and a radio frequency power source for generating resonance and providing uniform plasma distribution; wherein the induction coils are located in the reaction cavities and are electrically connected with the radio frequency power source, the n reaction cavities are sequentially connected, the n induction coils are connected in series, the sum of the electrical lengths of the induction coils is an integral multiple of the wavelength of the radio frequency signal emitted by the radio frequency power source, and three induction loop zones are formed inside the reaction cavities. Compared with the prior art, the application has the advantages of realizing zero total magnetic moment design, improving processing efficiency, improving stability and simplifying structure.

The utility model relates to a radio frequency coaxial load structure, and provides an adjustable high-precision equal-phase load structure in order to solve the problem that the existing radio frequency coaxial load is inconsistent in electrical length, and the adjustable high-precision equal-phase load structure comprises an outer shell, an insulating medium, an inner conductor, a load resistance tuning assembly and a rear cover, the rear end of the inner conductor extension section is provided with a blind hole, and an elastic body is arranged in the inner conductor extension section; the load resistor tuning assembly comprises a tuning bushing and a load resistor, the tuning bushing is of a horn structure, an elastic clamping seat is arranged on a through hole in the small end of the tuning bushing, the front end of the load resistor penetrates through the blind hole and then is connected with the inner conductor through an elastic body, and the rear end of the load resistor penetrates through the through hole in the small end of the tuning bushing and is connected with the elastic clamping seat; a tuning external thread is arranged on the circumferential face of the outer side of the tuning lining, a tuning internal thread matched with the tuning external thread is arranged on the inner wall of the outer shell, and the phase relation among the load resistor, the elastic body and the outer shell can be adjusted through the elastic clamping base.

The application provides a full-band terahertz harmonic mixer based on an improved grounding structure, and belongs to the technical field of terahertz devices. Double improved grounding structures are symmetrically arranged near the diode of a traditional mixer to replace a traditional radio frequency grounding circuit, so that the electrical length of a local oscillator signal input loop can be greatly reduced, the influence of a grounding structure parasitic effect on radio frequency input performance can be reduced, the divergence degree of an optimal embedded impedance curve of a local oscillator port can be reduced, the bandwidth of a mixing circuit can be improved, and the complexity of matching work of the mixing circuit can be reduced.

To reduce uneven heating and defrost frozen objects in a short time.SOLUTION: A high-frequency defrosting device includes a flat upper electrode and a flat lower electrode arranged in parallel. Multiple meanderline electrodes, formed in a meanderline pattern with the center of the upper electrode or the center of the lower electrode as the symmetry point, are arranged in point symmetry on each of the upper electrode and lower electrode. One end of each meanderline electrode is electrically connected to the upper electrode or the lower electrode, respectively. The other end of the meanderline electrode, positioned centrally on the upper electrode or the lower electrode, is not electrically connected to the upper electrode or the lower electrode. The electrical length of the meanderline electrodes is formed such that it is an integer multiple of one-quarter of the wavelength λ of the RF signal output by the high-frequency power source.SELECTED DRAWING: Figure 1