Abstract: A time delay filter comprising a substrate; four coupled LC resonators, each having a coupling point; a first capacitor that electrically couples the first coupling point to the second coupling point; a second capacitor that electrically couples the second coupling point to the third coupling point; and a third capacitor that electrically couples the third coupling point to the fourth coupling point; the filter group delaying a signal output at the fourth coupling point relative to a signal input at the first coupling point.

Abstract: A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

Abstract: A cavity filter that uses cross-coupling is disclosed, which includes: a housing, in which multiple cavities are formed, with the cavities being open towards a first direction; multiple resonators held respectively in the multiple cavities; and a coupling member arranged to pass through an aperture between a first cavity and a second cavity, from among the multiple cavities, such that the coupling member is positioned between a first resonator and a second resonator. Here, the coupling member includes a first extending portion and a second extending portion, the first extending portion is positioned closer to the first resonator than to the second resonator and extends towards one side of the housing along the first direction, and the second extending portion is positioned closer to the second resonator than to the first resonator and extends towards the other side of the housing along the first direction.

Abstract: A device for combining two or more tones generated by a measuring instrument for output to a port includes a combiner point, a transmission path extending from the combiner point to the port, two or more signal source filters each adapted to be connected to a respective signal source of the measuring instrument and one or more receiver filters each adapted to be connected to a receiver of the measuring instrument. Each of the signal source filters and receiver filters includes a cavity, a resonator arranged within the cavity and connected with the combiner point at a distance of one quarter of a wavelength of a signal having a center frequency of the passband of the filter, and a solid dielectric filter connected with the cavity.

Abstract: A method of removing common mode noise in a vehicle includes: a radio frequency (RF) switch connecting a feeder cable ground to a common mode (CM) filter or a digital signal processor (DSP) according to a selection signal of an amplitude modulation (AM) broadcast or a frequency modulation (FM) broadcast selected by a user and the CM filter increasing impedance of the feeder cable ground to remove the common mode noise.

Abstract: A device for producing a subwavelength hologram. The device comprises a metasurface layer attached to a substrate. The metasurface layer includes an array of plasmonic antennas that simultaneously encode both wavelength and phase information of light directed through the array to produce a hologram. The wavelength is determined by the size of the antennas, and the phase is determined by the orientation of the antennas.

Abstract: Disclosed is a two-capacitor-based filter design method comprising: determining a frequency f1 and a fractional bandwidth ratio FBW; selecting a first and a second capacitors according to f1 and FBW, in which a resonant frequency fC1 of the first capacitor is equal to f1×(1?N×FBW), a resonant frequency fC2 of the second capacitor is equal to f1×(1+M×FBW), and each of N and M is a positive number less than one; and determining a length of a first transmission line according to fC1 and a signal speed, and determining a length of a second transmission line according to fC2 and the signal speed. The first capacitor is coupled between a center of the first transmission line and ground, the second capacitor is coupled between a center of the second transmission line and ground, and the first and second transmission lines are connected in series.

Abstract: Disclosed herein are a RF resonator, a RF coil, and a magnetic resonance imaging (MRI) apparatus. The RF resonator includes a dielectric substance which is provided, on one surface thereof, with an electric conductor, and at least one conductor line which is installed on another surface of the dielectric substance so as to face the electric conductor and provided with a plurality of open-cut portions which are disposed in a plurality of rows.

Abstract: A dielectric resonator includes: two dielectric resonant cylinders and a metal cavity, wherein the dielectric resonant cylinders are located within the metal cavity; and it also includes: a fastener and a connector, wherein bottoms of the dielectric resonant cylinders are connected via the connector to form a U-shaped structure, and the connector is fixed on the metal cavity via the fastener. With the dielectric resonator of the embodiments of the present invention, a good close contact between the dielectric resonant cylinders and the metal cavity can be guaranteed, thereby improving the resonant performance of the dielectric resonator.

Abstract: A method for implementing a TM dielectric resonator is provided, which includes: a dielectric resonant column component with a metal connecting plate is machined; a metal cavity with an opening at one end is machined; the metal connection plate of the dielectric resonant column component is fastened to the inner wall of the metal cavity by a screw; the opening of the metal cavity is covered with a prefabricated cover plate; and a prefabricated tuning screw is screwed from the cover plate into the metal cavity.

Abstract: A tunable filter element comprises a resonator unit that defines a longitudinal axis, the resonator unit includes an inner conducting portion defining an inner shorting end along the longitudinal axis and an inner capacitive end opposing the inner shorting end, an outer conducting portion arranged around the inner conductor defining an outer shorting end along the longitudinal axis and an outer capacitive end opposite to the outer shorting end. The inner and the outer conductors maintain an annular gap there-between, and are coupled to form a shorting end at one end and a capacitive end at the other. The filter element further comprises a ferrite insert disposed between the inner and the outer conducting portions and substantially filling the annular gap, the ferrite insert being configured to receive a bias magnetic field in a direction substantially parallel to the longitudinal axis.

Abstract: Provided is a channel filter for a communication apparatus. The channel filter includes a first resonator, a coupling element having a first longitudinal section and a second longitudinal section, and a first adjusting element. The coupling element is designed to couple the first resonator at least indirectly with an input or output of the channel filter. The first longitudinal section has a greater width than the second longitudinal section. The first adjusting element is disposed at least partially in the first longitudinal section and at least partially in the second longitudinal section.

Abstract: A coupling is provided for coupling non-adjacent resonators of a radio frequency filter. The coupling joins together non-adjacent resonators with a metal strip. The metal strip is physically connected to but electrically isolated from resonators located between the connected non-adjacent resonators. The metal strips include tabs the length of which may be varied. The coupling works with different resonator configurations including horizontally aligned resonators. The coupling allows for the jumping of an even number of resonators can produce zeros at high and low bands. A single coupling of this configuration enables two negative couplings.

Abstract: There is disclosed a mobile terminal including a housing comprising a first metal case, a second metal case and a first non-conductive case arranged between the first metal case and the second metal case, a battery embedded in the housing, a first coil arranged in an area covered by the first metal case inside the housing, a main board comprising a charging module implemented to recharge the battery using electric currents which flow in the first coil, and a first resonator arranged in an area covered by the first non-conductive case and comprising a first matching circuit corresponding to a first frequency, such that the examples of the mobile terminal in accordance with the present disclosure may enhance performance of the wireless communication unit and wireless charging performance, without design change of the housing having the metal case.

Abstract: A dielectric resonator which has a simple structure and is easy to manufacture, and a dielectric filter and a communication apparatus using the same are provided. In a dielectric resonator, a dielectric body includes a first portion having surfaces and a second portion having surfaces. A conductor surrounding the dielectric body includes inner surfaces facing the surfaces. A conductor is disposed between the surface and the inner surface. A conductor is disposed between the surface and the inner surface. The dielectric body includes a third portion which is not interposed between the conductors and a fourth portion which is not interposed between conductors.

Abstract: The inventive assembly comprises a hyperfrequency component of the surface-mounted component type including at least one first hyperfrequency transmission line, as well as a printed circuit board including at least one second hyperfrequency transmission line able to be put in contact with the first hyperfrequency transmission line. The component comprises an enclosure with a face in contact with the printed circuit board, which includes at least one cavity for confining a hyperfrequency signal, delimited by conductive surfaces of the enclosure, and by a conductive zone of the second hyperfrequency transmission line.

Abstract: A radiating system for transmitting and receiving signals in first and second frequency regions includes a radiating structure, a radiofrequency system, and an external port. The radiating structure has first and second isolated radiation boosters coupled to a ground plane layer. A first internal port of the radiating structure is between the first radiation booster and the ground plane layer, and a second internal port is between the second radiation booster and the ground plane layer. A distance between the two internal ports is less than 0.06 times a wavelength of the lowest frequency. The maximum size of the first and second radiation boosters is smaller than 1/30 times the wavelength of the lowest frequency. The radiofrequency system includes two ports connected respectively to the first and the second internal ports of the radiating structure, and a port connected to the external port of the radiating system.

Abstract: A balun filter utilized for a radio-frequency (RF) system includes a first terminal coupled to an antenna of the RF system for delivering an RF signal; a differential port has a second terminal and a third terminal for delivering a differential signal; a band pass filter coupled between the first terminal and the differential port has a plurality of resonators, each including a surrounding line substantially surrounding an area and forming a loophole on a side of the each resonator; and at least a line segment connected to the surrounding line and disposed separately within the area surrounded by the surrounding line.

Abstract: In some aspects, a resonator device for spin resonance applications is described. In some examples, the resonator device includes a substrate, terminals, and resonators. The terminals include a first terminal having first terminal segments disposed on a substrate surface, and a second terminal having second terminal segments disposed on the substrate surface opposite the first terminal segments. The resonators include conductors disposed on the substrate surface between the first and second terminals. Each conductor is disposed between one of the first terminal segments and a respective, opposite one of the second terminal segments.

Abstract: A microstrip line filter comprising a coupling mechanism arranged to couple a first resonator and a second resonator, wherein the coupling mechanism includes a shared metallic coupling member arranged to have a predetermined dimension associated with an operation characteristics of the first and second resonators.

Abstract: A method and structure for a radio frequency identification (RFID) sensor that may be used to monitor various environmental conditions. The environmental condition measured depends on a sensor material used in the RFID sensor. The sensor material is selected based on a flux in electrical conductivity relative to its saturation of the environmental condition being monitored. The sensor material is placed between adjacent electrically conductive structures of the RFID sensor. Upon a change in the environmental condition being measure, the electrical conductivity of the sensor material changes, thereby increasing or decreasing an amplitude of a response by the RFID sensor to an interrogation by an RFID reader.

Abstract: A filtering device includes at least one dielectric resonant element, which includes a dielectric block, an outer conductor, and an inner conductor, a terminal disposed in a through hole of the dielectric resonant element from a front surface, a plate-shaped circuit element electrically coupled with the at least one dielectric resonant element via the terminal, and a substrate on which the at last one dielectric resonant element and the plate-shaped circuit element are mounted. The outer conductor is disposed so as to cover the back surface besides the peripheral surface of the dielectric block. The first end surface of the dielectric block includes a first electrode-free portion that electrically isolates the inner conductor from the outer conductor, and a second electrode-free portion that electrically isolates the inner conductor from the outer conductor.

Abstract: A dielectric resonator and a dielectric filter are provided. The inner wall or the outer wall of the dielectric resonator is plated with silver. With the technical solution, it can be guaranteed that the volume of a dielectric resonant column of which the inner wall or the outer wall is plated with silver is reduced by about 35% as compared with the volume of an ordinary dielectric filter, or the volume of the dielectric resonator is reduced under the condition of the same cavity body. In addition, the dielectric resonator is stable and reliable in filtering performance, simple in production process, and overcomes the defect of large size of the universal dielectric resonator in the related art in the low communication frequency band.

Abstract: The present invention comprises: a conductive chassis having a cavity resonator; a conductive cover to cover the cavity resonator; a resonant element arranged in the cavity resonator, one end of the resonant element being connected with the chassis and the other end being open end; and a movable conductor arranged in a space between the open end of the resonant element and the conductive cover. As a result, a tunable band-pass filter which is inexpensive and of a simple structure and which can change a resonance frequency of a cavity resonator and the coupling amount between cavity resonators easily is realized.

Abstract: Radio frequency (RF) signal boosters are provided. A radio frequency signal booster can include a housing integrated with a base station antenna. The booster includes a mobile station antenna port, and downlink and uplink amplifiers within the housing. The base station antenna can receive wireless communications signals on one or more downlink channels and transmit wireless communications signals on one or more uplink channels. Also, the mobile station antenna port can be connected to an integrated or separate mobile station antenna, which can provide communications signals on one or more downlink channels and receive wireless communications on one or more uplink channels. An isolator in the form of a reflector integrated with the housing can isolate the mobile station antenna from the base station antenna.

Abstract: Non-coaxial conductors, such as direct current power conductors, may be inserted into, or separated from, a central section of a radio frequency (RF) coaxial conductor that is supplying RF signals.

Abstract: A dielectric resonator, an assembly method thereof and a dielectric filter enable are provided. The dielectric resonator includes the dielectric resonant column, the metal cavity, a sealing cover plate and a tuning screw, wherein the dielectric resonant column is located in the metal cavity, the sealing cover plate is located on an upper end face of the metal cavity, and the tuning screw is located on the sealing cover plate. The dielectric resonator also includes an insulating fixed module located between the lower end face of the sealing cover plate and the upper end face of the dielectric resonant column, and the insulating fixed module is high enough to ensure that a pressure is formed between the sealing cover plate and the dielectric resonant column, so that the dielectric resonant column is fixed at the bottom of the metal cavity.

Abstract: A resonator having increased isolation includes a first resonator having first characteristics, and configured to resonate with another resonator having the first characteristics; and a second resonator having second characteristics, and configured to resonate with another resonator having the second characteristics; wherein the resonator has an arrangement and a structure that minimizes a coupling between the first resonator and the second resonator.

Abstract: The dielectric resonator includes a sealing cover, a dielectric resonant column, a metal cavity, and an electrically-conductive elastic structure body. The dielectric resonant column is located within the metal cavity, wherein the sealing cover is connected to an upper surface of the dielectric resonant column. The sealing cover is located at the upper end face of the metal cavity and is configured to seal the metal cavity. The metal cavity is provided with a groove at the bottom. The electrically-conductive elastic structure body is located within the groove and is configured to support the dielectric resonant column. The depth of the groove causes a lower surface of the dielectric resonant column to be lower than an inner bottom surface of the metal cavity after the sealing cover seals the metal cavity. A lower end face of the dielectric resonant column is in contact with the electrically-conductive elastic structure body.

Abstract: A radio frequency (RF) dielectric resonator filter includes at least a first cavity and a second cavity, each cavity being loaded with a dielectric resonator. The first cavity is separated from the second cavity by a common wall, the common wall including a first and second aperture that couple an electromagnetic field between the first cavity and the second cavity. A first externally adjustable tuning screw extends from the second aperture, a portion of the tuning screw being external to the filter. The first aperture is an iris disposed in a central portion of the wall and the second aperture is disposed proximate to a perimeter of the wall. The second aperture has an effective area that is adjustable by the first externally adjustable tuning screw.

Abstract: A reconfigurable RF filter, which includes a first resonator, a second resonator, and a first coupling circuit, is disclosed. The first coupling circuit is coupled between the first resonator and the second resonator. The reconfigurable RF filter operates in one of a group of operating modes, which include a first operating mode and a second operating mode. During the first operating mode, the reconfigurable RF filter is a bandpass filter having a first bandwidth and a first insertion loss via the first resonator. During the second operating mode, the reconfigurable RF filter is a bandpass filter having a second bandwidth and a second insertion loss via the first resonator, such that the first bandwidth is greater than the second bandwidth and the first insertion loss is less than the second insertion loss.

Abstract: The present invention is related to an adjustable harmonic filtering device, mainly comprising a first connecting port, a second connecting port, a harmonic filtering unit, and an adjusting unit, in which a passive network is presented between the first connecting port and the second connecting port, as well as the harmonic filtering unit is connected to the passive network. The harmonic filtering unit comprises a first inductor and a first capacitor. The adjusting unit is adjacent to the first inductor of the harmonic filtering unit, and induced electromagnetically therewith. Thus, frequency-band of the harmonic, to be filtered out by the harmonic filtering unit, may be changed, allowing for reducing loss of signal occurring in the process of transmission between the first connecting port and the second connecting port effectively.

Abstract: A coupling is provided for coupling non-adjacent resonators of a radio frequency filter. The coupling joins together non-adjacent resonators with a metal strip. The metal strip is physically connected to but electrically isolated from resonators located between the connected non-adjacent resonators. The metal strips include tabs the length of which may be varied. The coupling works with different resonator configurations including horizontally aligned resonators. The coupling allows for the jumping of an even number of resonators can produce zeros at high and low bands. A single coupling of this configuration enables two negative couplings.

Abstract: Disclosed is a variable bandwidth RF filter. The disclosed filter comprises: a first filter unit having a first bandwidth and a variable-frequency structure; and a second filter unit having a second bandwidth and a variable-frequency structure. The first filter unit and the second filter unit are coupled to a cascade structure, and the bandwidth is adjusted by varying the frequency of the first filter unit and of the second filter unit. The disclosed filter is advantageous in that the variation of the bandwidth can be easily performed using a simple structure.

Abstract: In a high frequency filter, a multilayer structure includes a plurality of insulator layers, a first transmission line transmits an input signal, and a second transmission line is electromagnetic coupled with the first transmission line on the same insulator layer and transmits an output signal. A conductor layer defines capacitors with the first transmission line and the second transmission line with the insulator layer in between. A dielectric constant of the insulator layer that comes in contact with the first transmission line and the second transmission line is higher than a dielectric constant of an insulator layer other than the insulator layer.

Abstract: There are provided a dielectric filter with excellent electrical characteristics, a duplexer, and a communication device using the dielectric filter. A dielectric filter includes a dielectric block provided with first through holes; inner conductors disposed on inner surfaces of the first through holes; second through holes; a terminal electrode connected to an inner conductor located at on end; a terminal electrode connected to an inner conductor located at the other end; and an outer conductor surrounding the dielectric block, being connected to a reference potential, wherein the first through holes are located on a second main surface side, and the second through holes are located on a first main surface side with respect to the first through holes. A duplexer and a communication device use this dielectric filter.

Abstract: A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

Abstract: A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

Abstract: Devices and methods related to multiple-pole ceramic resonator filters. In some embodiments, a radio-frequency (RF) filter can include a first coaxial resonator in a first orientation and having an input tab on a first side of the filter, and an N-th coaxial resonator in the first orientation and having an output tab on the first side of the filter. The RF filter can further include second and (N?1)th coaxial resonators, each in a second orientation opposite the first orientation to form first and second interdigitations with the first and N-th resonators, respectively. The RF filter can further include at least two coaxial resonators in the first orientation and coupled between the second and (N?1)th resonators. The N resonators can be slot coupled between the first and N-th resonators. The first and second interdigitations can be configured to provide enhancement of the slot coupling between the first and N-th resonators.

Abstract: Provided is a dielectric filter that can be anchored in a stable manner without causing damage even when there is variation in the size of the parts. With this dielectric filter, one surface of washers has a concave part, which is equipped with an edge part formed at the perimeter of the one surface, a floor surface provided at a lower position than the edge part, and a tapered part formed between the edge part and the floor surface. The washers are arranged on the upper surface of and fastened by means of screws to dielectric bodies with the concave parts facing the dielectric bodies, with sheet metal therebetween.

Abstract: A resonator and a filter including the same are provided. The resonator includes a body formed of a dielectric material and including a through-hole formed in one direction, and a conductive film coupled to at least one of both side cross-sections of the body in a lengthwise direction and a wall surface of the through-hole.

Abstract: A resonance device and a filter including the same are provided. The resonance device includes a case having a first ground surface and a second ground surface which are facing each other, and a first conductive layer located in the case, and the first conductive layer includes a main part grounded via the first ground surface, and a protruding part which has a width different from that of the main part and is located to be spaced apart from the second ground surface.

Abstract: A radio-frequency (RF), base station notch filter includes an integral, conductive RF notch filter structure having one or more notch filter elements, where the notch filter elements may be circular in shape. The integral notch filter reduces insertion losses and passive intermodulation distortion.

Abstract: A frequency tunable microwave bandpass filter comprises a resonator, including: a cavity with conducting wall substantially cylindrical with axis Z having height H, and partially closed at both ends; and a dielectric element inside the cavity. The resonator resonates at two perpendicular polarizations having distributions of electromagnetic field in the cavity deduced from eachother by 90° rotation. The element rotates about an axis substantially perpendicular to axis Z, between a first and second position. The element comprises a first end wherein: in a first position the element is disposed substantially in a plane perpendicular to axis Z and the center of the first end is disposed at a height in the cavity corresponding substantially to an electric field minimum; and in a second position the element is substantially parallel to Z and the first end is disposed in a plane corresponding to an electric field maximum within +/?30%.

Abstract: A dielectric filter includes a receiving member with a plurality of receiving spaces and a cover. The cover is arranged to cover the receiving spaces in the receiving member. Each receiving space of the plurality of receiving spaces includes a rectangular cavity with a dielectric.

Abstract: Provided is a semi-coaxial resonator that reduces the insertion loss in the pass band and that is made to be compact, lightweight, and low in cost. A resonator is formed by fastening a cylindrical first element with a square and planar second element at an open end (one end) of the first element. A plurality of these resonators are disposed such that the square edges are brought close to each other and the other ends of the first elements are secured to the bottom of a box-shaped case. The open side of the case that accommodates the plurality of resonators is closed by a lid.

Abstract: A technique relates to a qubit readout system. A cavity-qubit system has a qubit and a readout resonator and outputs a readout signal. A lossless superconducting circulator is configured to receive the microwave readout signal from the cavity-qubit system and transmit the microwave readout signal according to a rotation. A quantum limited directional amplifier amplifies the readout signal. A directional coupler is connected to and biases the amplifier to set a working point. A microwave bandpass filter transmits in a microwave frequency band by passing the readout signal while blocking electromagnetic radiation outside of the microwave frequency band. A low-loss infrared filter has a distributed Bragg reflector integrated into a transmission line. The low-loss filter is configured to block infrared electromagnetic radiation while passing the microwave readout signal. The low-loss infrared filter is connected to the microwave bandpass filter to receive input of the microwave readout signal.

Abstract: A combination RF filter and printed circuit board assembly wherein the RF filter is defined by a block of dielectric material including at least first and second side surfaces. A metal bracket with a plurality of fingers is secured to each of the first and second side surfaces. The fingers on the brackets extend through respective apertures in the printed circuit board and are soldered to the printed circuit board. The brackets relieve and transfer the thermal and mechanical stresses that result from use of a filter and printed circuit board that are made of materials with different thermal and mechanical characteristics and reduce the risk of cracking or damage to the filter, the printed circuit board, and the solder joints during use.

Abstract: The present invention provides a dielectric waveguide input/output structure for connecting to a coaxial connector a plurality of dielectric waveguide resonators each comprising an approximately parallelepiped-shaped dielectric block, wherein the plurality of dielectric waveguide resonators include a first dielectric waveguide resonator and a second dielectric waveguide resonator each having an exterior coated with an electrically conductive film, except for a coupling window, wherein each of the coupling window is formed with a probe composed of an electrically conductive film, the probe having one end connected to a feeding point, and the other end connected to the electrically conductive film, and wherein the first dielectric waveguide resonator and the second dielectric waveguide resonator are arranged in such a manner that the one side surfaces thereof are located in opposed relation to each other.

Abstract: A cavity filter includes a first layer circuit board, a second layer circuit board and a middle layer circuit board locates between the first layer circuit board and the second layer circuit board. A plurality of resonators locates on the first layer circuit board. A plurality of resonating cavities is located on the second layer circuit board one-to-one corresponding to the resonators. A slot is defined on the middle layer circuit board. The resonators traverse through the slot and are placed in the resonating cavities to form a plurality of resonating units, and the plurality of resonating couple with the slot of the middle layer circuit board.