Abstract: The invention relates to a resonance trap (8) for suppressing electromagnetic coupling phenomena for a line (1), which resonance trap includes a conductor (10) which extends parallel to and along a part of the length of the line (1). Conventional resonance traps (8) have the drawback that a direct connection exists between the RF line and the individual resonance traps (8). It is an object of the invention to provide a resonance trap (8) which enables a modular assembly on the line (1). The object is achieved by means of a resonance trap (8) of the kind set forth in which inner conductors (10) extend parallel to the line (1) and in which outer conductors (11) extend parallel to the inner conductors (10), said inner conductors (10) being arranged at a radial distance from the line (1) which is smaller than that at which the outer conductors (11) are arranged and the outer conductors (11) being arranged to cover at least partly the inner conductors (10) in the radial direction relative to the line (1).

Abstract: A reduced length filter including a housing having a female connector end and an opposed male connector end, and a circuit board positioned within the housing. The circuit board has first and second filter sections positioned on upper and lower surfaces thereof, and a ground plane positioned therebetween. The first filter section is in electrical communication with the second filter section. A first isolation shield is provided in electrical communication with the ground plane, and extends from the upper surface of the circuit board in a direction substantially perpendicular thereto and proximate one of first and second ends of the circuit board, and a second isolation shield is provided in electrical communication with the ground plane, and extends from the lower surface of the circuit board in a direction substantially perpendicular thereto and proximate the other one of the first and second ends of the circuit board.

Abstract: In a multiple phase system for supplying power from an AC source to nonlinear loads, a device for substantially eliminating currents in a neutral wire. The device includes a completely-passive parallel resonant circuit having three passive electrical branches connected in parallel tuned to a third harmonic frequency of the AC source. The three branches comprise a first branch consisting of a capacitor, a second branch consisting of a reactor, and a third branch consisting of a resistor. The resonant circuit is connected to the neutral wire.

Abstract: A new type of frequency-tunable active notch filter achieves frequency selectivity through interaction among input derived signal components that are passed through parallel signal channels in a forward-only direction. The notch filter differs from earlier channelized notch filters by using multiple, instead of just one, bandpass channels that maintain required forward signal flow in the main, passband-determining signal path without signal distortion at passband frequencies. The new approach has been experimentally verified with a hybrid-integrated three-channel filter whose 40-dB-deep band-reject notch can be continuously tuned, with the help of voltage-controlled variable-capacitance elements, from 9.5 to 10.5 GHz.

Abstract: An apparatus and method are provided for attenuating an undesired frequency (f1) relative to a desired frequency (f0) in a signal transmitted from an out-put (220) of an active element (210). Generally, the apparatus includes a parallel-resonant trap (145) coupled to the output of the active element (210), the trap including a network of reactive elements (235).

Abstract: An apparatus is disclosed wherein a dual directional harmonics dissipation filter includes an input terminal coupled to a RF power amplifier providing a radio frequency signal in a predetermined frequency range, an output terminal for providing the radio frequency signal to a load at the predetermined frequency range, a low pass filter connected between the input terminal and the output terminal, and a plurality of high pass filters coupled to the low pass filter wherein the plurality of high pass filters receive and dissipate signals in excess of the predetermined frequency range and wherein the plurality of high pass filter's effect on the impedance is offset at the input and output of the low pass filter.

Abstract: Two LC resonance circuits, each including a parallel combination of an inductor and a capacitor and both magnetically coupled, are connected between an input terminal and an output terminal, and a parallel resonance trap circuit including a parallel combination of an inductor and a capacitor is connected in series between at least either the input terminal, the output terminal and the LC resonance circuit.

Abstract: A spurious signal reduction circuit which is connected to a main signal line. The spurious signal reduction circuit comprises a resistor having a terminal connected to the main signal line, an LC parallel resonance circuit and an LC series resonance circuit. The parallel resonance circuit has a resonance frequency which is equal to a main signal frequency and has a terminal connected to another terminal of the resistor. The series resonance circuit has a resonance frequency which is equal to a spurious signal frequency and has a terminal connected to the other terminal of the resistor.

Abstract: An image rejecting microwave photonic downconverter uses a microwave sub-carrier modulation technique without concern for image frequency interference in the shifted signal, thereby allowing telecommunications systems to downconvert densely multiplexed communications channels into a low frequency band where conventionqal electronics can perform signal-processing functions. The image rejecting microwave photonic downconveter incoming microwave signals can be processed without ambiguity in direction finding applications, allowing remotable, multioctave microwave signal processing for frequency and phase determination.

Abstract: A switchable filter for passing one of a plurality of frequency bands has n bandpass filter sections coupled in parallel between a filter input terminal and a filter output terminal. Each of the n bandpass filter sections is arranged to pass a different frequency band. Each of n switches is coupled to a respective one of the n bandpass filter sections, and each of the n switches is operable in either an OFF state for activating a corresponding one of the n bandpass filter sections or an ON state for deactivating the corresponding one of the n bandpass filter sections. The n switches are arranged and controlled so that, when any one of then switches is operated to its off state, the remaining n−1 switches are operated to their ON states and form a series circuit for conducting a common current.

Abstract: An input trap circuit removes a predetermined frequency component included in an input signal and then outputs the input signal to a circuit at a later stage. The input trap circuit is provided with: a parallel oscillation circuit in which a pair of variable capacitance diodes are connected in series such that cathodes thereof are connected to each other at a junction portion and in which an inductance is connected in parallel to the variable capacitance diodes between anodes of the variable capacitance diodes at both ends thereof; a voltage applying device for applying a voltage to the junction portion so as to vary capacitance values of the variable capacitance diodes on the basis of reverse voltage characteristics of the variable capacitance diodes respectively; and a variable capacitor element connected between the junction portion and a ground.

Abstract: An antenna (24) for minimizing reception of undesirable signals below a predetermined frequency band includes a first and a second terminal (A, A′) connectable to at least a receiver (22). The antenna components are connected to the first and second terminals, and a filter (26) is integrally connected across the first and second terminals (A, A′). The filter matches an impedance value of the antenna components with an impedance value of the receiver. Moreover, the filter effectively forms a short circuit at the undesirable frequency to minimize reception of undesirable signals below the predetermined frequency band.

Abstract: An input trap circuit removes a predetermined frequency component included in an input signal and then outputs the input signal to a circuit at a later stage. The input trap circuit is provided with: a parallel oscillation circuit in which a pair of variable capacitance diodes are connected in serial such that cathodes thereof are connected to each other at a junction portion and in which an inductance is connected in parallel to the variable capacitance diodes between anodes of the variable capacitance diodes at both ends thereof; a voltage applying device for applying a voltage to the junction portion so as to vary capacitance values of the variable capacitance diodes on the basis of reverse voltage characteristics of the variable capacitance diodes respectively; and a variable capacitor element connected between the junction portion and a ground.

Abstract: A passive bandpass tracking filter tracks the frequency of an RF input signal received within a radio receiver's tracking range of RF frequencies. The bandpass filter includes parallel inductor and capacitor circuits connected in shunt between the input and output filter ports. A tracking control signal is selectively applied to change the capacitance of the LC circuits in order to shift the filter's frequency characteristics/profile as the filter tracks through the tracking band. The filter attenuates half-IF, receiver IF, and image spurious signals. In particular, the filter substantially attenuates the image spurious signal throughout the tracking frequency range by 50 dB or more below the filter output signal level. The filter also attenuates the half-IF spurious signal throughout the tracking frequency range by well over 10 dB or more below the filter output signal level. The receiver IF spurious signal is attenuated about 40 dB.

Abstract: A spurious signal reduction circuit which is connected to a main signal line. The spurious signal reduction circuit comprises a resistor having a terminal connected to the main signal line, an LC parallel resonance circuit and an LC series resonance circuit. The parallel resonance circuit has a resonance frequency which is equal to a main signal frequency and has a terminal connected to another terminal of the resistor. The series resonance circuit has a resonance frequency which is equal to a spurious signal frequency and has a terminal connected to the other terminal of the resistor.

Abstract: Two LC resonance circuits, each including a parallel combination of an inductor and a capacitor and both magnetically coupled, are connected between an input terminal and an output terminal, and a parallel resonance trap circuit including a parallel combination of an inductor and a capacitor is connected in series between at least either the input terminal, the output terminal and the LC resonance circuit.

Abstract: A microwave amplifier includes a bias circuit including a micro-strip line and a capacitor for biasing an output line of a FET with a DC voltage, and a filter block implemented by a low-pass-filter or a band-rejection-filter and a capacitor serially connected between the output line and the ground. The filter block passes a beat frequency generated by two of the carrier signals included in the input signal of the FET while maintaining the carrier signals on the output line.

Abstract: An integrated radio frequency (RF) coupling scheme is provided for realizing low voltage RF integrated circuits. According to the invention, on-chip capacitively coupled resonant elements are used to DC isolate circuit block elements which are required to be connected in series and share a common DC current. The coupling scheme according to the present invention may be applied to several commonly used RF integrated circuit topologies such as low noise amplifiers and mixers.

Abstract: A power conditioning circuit for conditioning power supplied by a power source at a nominal frequency over line, neutral and ground conductors includes first, second and third impedances coupled to the line, neutral and ground conductors, respectively, and to output lines. Each of the impedances prevents power at frequencies greater than the nominal frequency from reaching the output lines.

Abstract: A method for designing a filtering device essentially comprising the steps of determining a desired response of the filtering device at a selected frequency; and selecting a circuit element that exhibits a parasitic effect at the selected frequency, wherein the parasitic effect results in the circuit element having the desired response at the selected frequency. A second method for designing a filtering device, similar to the first, but utilizes a field effect at the selected frequency, instead of a parasitic effect.A frequency converter comprising a notch filter which filters a first frequency and does not filter a second frequency. The notch filter comprises a lumped parameter element and a transmission line, wherein the transmission line is coupled to the lumped parameter element.

Abstract: Disclosed herein is a harmonic suppression circuit having a first microstrip line and a second microstrip line each having the same characteristic impedance. One end of the first microstrip line is electrically connected to a transmission line over which a signal having a predetermined frequency is transmitted, and one end of the second microstrip line is grounded. The length of the first microstrip line and the length of the second microstrip line are respectively set to the length corresponding to 1/8 of the wavelength with respect to the predetermined frequency. Series impedance means comprised of capacitance means and inductance means is electrically connected between the other end of the first microstrip line and the other end of the second microstrip line. The reactance of the capacitance means and the reactance of the inductance means at the predetermined frequency are respectively set to 3/4 of the characteristic impedance of each microstrip line.

Abstract: The invention provides a high-frequency composite unit, wherein: a two-terminal switch constituting a transmission section, an LC filter, and a notch filter are connected between a first terminal and a second terminal; and said two-terminal switch, said LC filter, and said notch filter are integrated into a layered structure in which a plurality of dielectric layers are stacked. The above high-frequency composite unit has high performance, which can handle high-frequency signals of multiple frequency bands that are relatively adjacent.

Abstract: The inventive bandstop filter is suitable for use in a multi-layer ceramic (MLC) structure. Specifically, the filter is a semi-lumped type, formed by lumped capacitors and distributed transmission lines. Preferably, transmission lines are used as equivalent inductors, instead of as J, K inverters or resonators. The bandstop filter preferably has attenuation poles very close to lower passband edge, which results in a very sharp rejection near the stopband. The inventive filter may be utilized as a transmitter-end filter in, e.g., duplexer applications or for miniaturized applications, such as portable communications.

Abstract: A filter comprises an inductor, a first variable capacitance diode, a second variable capacitance diode having nearly identical characteristic as the first variable capacitance diode, a control terminal for applying voltage to the first and the second variable capacitance diodes, an input terminal, an output terminal and a signal line between the input terminal and the output terminal. A cutoff frequency is controllable with the voltage applied to the control terminal. The variable frequency filter which can receive a large signal has reduced size due to a structure in which the first and the second variable capacitance diodes having nearly identical characteristics are connected either in series or in parallel with their polarities reversed against each other.

Abstract: An apparatus and method for substantially reducing zero sequence harmonic currents at the load-end of branch circuits that supply single-phase, non-linear loads. The invention includes a three-phase, six-terminal, zig-zag autotransformer which functions as the zero sequence filter. The first winding, which is located on the first core leg, is connected in series with the sixth winding, which is located on the third core leg. The third winding, which is located on the second core leg, is connected in series with the second winding, which is located on the first core leg. The fifth winding, which is located on the third core leg, is connected in series with the forth winding, which is located on the second core leg. In this configuration, the first winding is magnetically coupled to the second winding, the third winding is magnetically coupled to the forth winding and the fifth winding is magnetically coupled to the sixth winding.

Abstract: A power conditioning circuit for conditioning power supplied by a power source at a nominal frequency over line, neutral and ground conductors includes first, second and third impedances coupled to the line, neutral and ground conductors, respectively, and to output lines. Each of the impedances prevents power at frequencies greater than the nominal frequency from reaching the output lines.

Abstract: A microwave amplifier includes an FET, a DC bias voltage supply circuit, and a beat smoothing circuit. The FET amplifies a microwave signal including a plurality of carrier frequencies that are different from each other. The DC bias voltage supply circuit supplies a DC bias voltage to the FET. The beat smoothing circuit removes a beat frequency generated on a line connected to the FET due to a difference among the plurality of carrier frequencies. The beat smoothing circuit is constituted by a microstrip line having a low impedance with respect to the beat frequency, and a capacitor for short-circuiting to ground the beat frequency output from the filter means.

Abstract: A satellite broadcasting receiving tuner having a band-pass filter capable of adequately attenuating and removing disturbing wave components having frequencies in the vicinity of 480 MHz and capable of being easily tuned to the high-end frequency. The tuner has at least the band-pass filter for transmitting a down-converted received satellite broadcasting signal and a frequency converter section for converting the received satellite broadcasting signal transmitted through the band-pass filter into a signal having an intermediate frequency.

Abstract: A bandstop filter contains one or more resonant circuits connected by interconnecting transmission lines. The resonant circuits each have a transmission line connected between two capacitors. One capacitor is connected to the interconnecting transmission line and the other capacitor is connected to ground. The resonant circuits may have a helical coil of superconducting materials as the transmission line. The capacitors may be in the form of screws, which can be inserted into or removed from the center of the helix. The helix may be formed as a discrete structure and supported by a low-loss material within a housing.

Abstract: The present invention aims to provide a CATV converter which can receive both of analog and digital signals. The CATV converter comprises a second mixer (10) coupled with a first filter (13) which attenuates approximately equal frequency to an audio carrier of an upper adjacent channel and approximately equal frequency to a video carrier of a lower adjacent channel, a first amplifier (14) coupled with an output terminal of the first filter (13), and a second filter (15) coupled with the output terminal of the first amplifier (14). The second filter (15) attenuates a video carrier of the upper adjacent channel and an audio carrier of the lower adjacent channel. When an input signal is within a predetermined frequency range, the input signal fed to the input terminal (1) can short-circuit the input and output terminals of the second filter with a high frequency of the input signal.

Abstract: A multilayered frequency separator comprising a plurality of insulating layers, and having at least two notch circuits. The notch circuit is constituted by pattern electrodes formed on interfaces of each of the insulating layers which construct the multilayer structure, and comprises a capacitor component connected to an inductance component. The multilayered frequency separator is suitably used for branching the frequency bands for dual-band handy phone.

Abstract: A passive filter device for a capacitor in series with a substantially inductive transmission line of an electric transmission system is disclosed. The passive filter device comprises a double-loop RCL filter in parallel with the series capacitor. At power frequency, the filter device allows the power frequency current to pass through the series capacitor with minimum power losses. At sub-synchronous resonance frequencies, the passive filter device provides bypassing of the series capacitor with maximum selectivity of the RCL filter.

Abstract: In a trap circuit of the bridged-T type, having a delta RC circuit (RR, C1, C2) and a parallel resonant circuit (L, Cp), the capacitance Cp is constituted by variable capacitance diodes (D1, D2) connected via a resistor (8) to a control voltage (Vtone), and the resistor (RR) of the bridged-T circuit is constituted by a PIN diode whose current is controlled by the same control voltage (Vtone) via a resistor (9).

Abstract: An active microwave notch filter is formed by connecting a photonic bandgap crystal (PBC) in a feedback loop around a microwave amplifier. The PBC has an attenuation bandgap which establishes a frequency range of preferential amplification. Frequency selectivity can be achieved by applying signals to the dielectric members which form the PBC to vary their dielectric constants, and thus the bandgap, or by selecting among multiple parallel PBCs. Antennas are provided to transduce the electrical input to the PBC into electromagnetic radiation, and then back to an electrical signal after the radiation has been filtered by the PBC.

Abstract: A high-frequency composite component used for a multi-band system, includes first and second circuits connected in parallel, the first and second circuits having infinite input impedances respectively at first and second frequencies, corresponding to first and second bands. Each of the first and second circuits includes a phase shifter, and a trap circuit connected as a load of the phase shifter. The phase shifter of each of the first and second circuits includes a strip line having a length of .lambda./4, wherein .lambda. is a wavelength corresponding to one of the first and second frequencies. The trap circuit of each of the first and second circuits includes a series resonance circuit, and the trap circuit resonates at one of the first and second frequencies.

Abstract: In order to avoid filter excitations of subharmonics or intermediate harmonics, that is to say of oscillations in the frequency range between integral harmonics of the mains frequency (f.sub.N), in the case of an attenuation resistor (R1, R3, R3') in parallel with a series resonant circuit comprising a filter inductor (L1, L3) in series with a filter capacitor (C1, C31, C31'), the resistance is dimensioned in such a way that a current gain of the filter (F1-F3) at its frequency pole points with an AC mains (1) is not greater than 6-fold. Double low-pass filters (F1, F2) and high-pass filters (F3) with attenuation resistors (R1, R3, R3') are particularly suitable as filters (F1, F3).

Abstract: A band-reject filter includes a three port circulator having an input port, a second port connected to a bandpass filter terminated in a matched load, and a third output port. The loss of the band-reject filter is enhanced by controlling the amplitude and phase of a feed-forward signal, passing between the input port and output port, relative to the amplitude and phase of a reflected signal from the matched load.

Abstract: A radio frequency filter comprising several resonator circuits, such as duplex filter, is provides with a given passband. Signal frequencies generating spurious response, mirror frequencies, etc. can be effectively attenuated so that the filter comprises one more resonator circuit connected as a bandstop circuit. That comprises a transmission line resonator (Res), a series connection of an inductive element (MLIN2) and a capacitance diode (D), one end of the series connection being couples to a coupling point in the transmission line resonator, dividing it into two parts (TLIN1, TLIN2), and the other end being couples to the output connector (1) of the radio frequency filter. In addition, means are provided for carrying the direct voltage (V+) to the cathode of the capacitance diode, whereby the series resonance frequency changes according to the control voltage.

Abstract: The disclosed AC harmonic first circuit utilizes band pass and stop filters that have resonance frequencies close to but yet a few Hz or a small percent away from the harmonic frequencies intended to be attenuated, the difference being comparable to the Q factor of the respective filter. Thus, every circuit filter has a different resonance frequency, and the difference between the filter resonance and harmonic frequencies might be 0.2-5%. Each filter attenuates the energy of each harmonic by possibly 10-50%. A network filter having a resonance frequency corresponding to the AC power network frequency is in series in the hot line between the power network source and the harmonic filter circuit. The circuit uses only passive components in reducing disruptive harmonics from the AC power network.

Abstract: Lumped element electrical components, such as inductors and capacitors, are formed to include high temperature superconducting materials. In the preferred embodiment, thin film epitaxial high temperature superconductors are patterned to form capacitors and inductors on low loss substrates. Preferably, a ground plane is formed on the back side of the substrate, most preferably being formed of high temperature superconducting material, or other highly conductive materials such as gold or copper. Various advantageous structures include a planar spiral structure, a zig-zag serpentine structure, a single coil structure and a double coil structure. Single layer and multilayer structures are included. Improved narrow bandpass filters, bandreject filters and high Q resonator structures are formed. Chebyshev bandpass filters are formed from multiple series connected zig-zag filter structures.

Abstract: A dual stage filter providing a relatively deep notch whose attenuation versus frequency curve is asymmetrical. The filter consists of a helical transmission line one end of which is connected to electrical ground. The opposite end is connected to a variable piston capacitor whose remaining end is also connected to ground. The ungrounded junction of these two components is connected to an input connector through a series capacitor. An identical circuit is arranged and connected to the output connector. These two circuits are isolated from each other by a conductive partition and housing. A series inductor connects the input and output connector. A matching capacitor is connected in parallel across a portion of the series inductor.

Abstract: A ballast filter in which the ballast can operate at a total harmonic distortion of power line current of less than 10%. Power dissipated by the filter when at a THD of less than 10% is relatively low. The input impedance of the ballast is chosen to be no greater than twice the equivalent filter impedance of a front end filter and no less than the equivalent filter impedance/1.5. The filter includes a transformer having a core which at times operates within the non-linear region of its B-H curve under nominally rated ballast load conditions.

Abstract: A switching device is presented for the transmission of telecommunication signals between a telephone network exchange and at least one subscriber connected thereto, where the exchange is able to transmit metering pulses, in addition to the voice signal. The signals are transmitted as digital signals between the exchange and the subscriber via a two-wire line, Which is connected with the exchange through a hybrid switching unit. To prevent the metering pulses from interfering with the voice signals, a parallel resonant circuit consisting of an inductance and a capacitor is connected to the two-wire system of the hybrid switching unit, and the receiving branch of the hybrid switching unit has an active and a passive filter connected in series. The passive filter is adjusted for the metering pulse frequency, and a filter that is tuned to the passive filter is used as the active filter, which compensates for a decrease in the NF (low frequency) level caused by the passive filter, with a corresponding increase.

Abstract: A filter structure of inexpensive design that reliably prevents rotation of a filter housing with respect to an outer sleeve of the filter structure is disclosed. More specifically, a connector portion of an end cap of the filter structure is keyed with an opening provided in a receiving end of the outer sleeve to prevent rotation of the filter housing with respect to the outer sleeve. Keying is preferably accomplished by forming the connector portion of the end cap in the shape of a "Double-D", although other shapes may be readily employed.

Abstract: An automatically tuned filter apparatus having as input a signal of constant or slowly varying but unknown frequency superimposed on a second signal of rapidly varying frequency with a first output attenuating the first signal by implementation of a narrow band rejection filter and the second output rejecting all but the first signal by implementation of a narrow band pass filter in which the characteristics of both filters are controlled by the relative amplitudes and phase differences of the two outputs.

Abstract: The object of this invention is to provide an electrical signal filter for improving electrical characteristics and reliability of the electrical signal filter for use in a cable television by protecting it from moisture. In an electrical signal filter having a filter portion provided inside a cylinder-shaped shield case, the filter portion includes a first filter circuit and a second filter circuit respectively mounted on circuit boards, and a shield member arranged between the first filter and the second filter. In the electrical signal filter, a moisture-proof material is applied to an entire surface of the filter portion and a contact area where the cylinder-shaped shield case containing the circuit boards and the filter portion therein contacts external components.

Abstract: A digital-to-analog conversion device for converting a digital signal to an analog signal for amplification by an audio amplifier. The conversion device has a solid state digital-to-analog converter and a filter connected to the output of the digital-to-analog converter. The filter comprises n passive components where n is a number of at least two, arranged so as to form an nth order filter for reducing the quantization of the output of the digital-to-analog converter.

Abstract: An electrical power distribution system of an industrial plant or a commercial building and having a capacity for delivering at least 500 KVA, includes a voltage step-down transformer connected between an AC source of electrical energy and a pair of power distribution line conductors across which there is connected a pulsed inductive load, such as a motor with a thyrister speed controller. The power factor of the system is corrected by a power factor correction capacitor connected directly across the system power distribution line conductors. Pulsed inductive loads tend to excite large harmonic currents in such systems having both a transformer and a power factor correction capacitor directly across the distribution line conductors. A filter, made up of a filter capacitor and a filter inductor tuned exactly to one harmonic, are connected in a series circuit branch that is connected directly across the system power distribution line conductors.

Abstract: An automatic tracking notch filter system tracks a large-magnitude narrow band signal through frequency effectively eliminating it. A frequency variable notch filter is responsive to a control input at which is applied a small amplitude AC dither signal. The resulting fluctuation in frequency of the notch filter causes corresponding fluctuations in the magnitude of the notch filter output. The output signal is rectified and band pass filtered around the dither frequency before being demodulated with the dither signal to provide a DC error signal indicating the magnitude and direction in frequency of the filter misalignment. The error signal is integrated and input to the control input of the notch filter with the dither signal such that the notch filter tracks the narrow band signal in response to the feedback signal provided at its control input.

Abstract: An antenna sharing device having a transmission filter connectable between a branch node of an antenna and a transmitter and a reception filter connectable between the branch node and a receiver. At least one of the transmission filter and the reception filter includes: a first parallel resonance circuit having a capacitor and a coil connected in parallel; a second parallel resonance circuit magnetically coupled to the first parallel resonance circuit; and a capacitor serially connected to the first parallel resonance circuit. One of the first and second parallel resonance circuits has a first resonance frequency, the other of the first and second parallel resonance circuits has one of the first resonance frequency and a second resonance frequency, and a combination of the first and second parallel resonance circuits and the capacitor forms an equivalent circuit providing a small insertion impedance at a third resonance frequency.