Patent Description:
One type of filter for RF applications is a resonator filter comprising a group of coaxial resonators. The overall transfer function of the resonator filter is a function of the responses of the individual resonators as well as the electromagnetic coupling between different pairs of resonators within the group.

<CIT> ("the '<NUM> patent") discloses different resonator filters having different configurations and topologies of resonators. For example, the '<NUM> patent discusses a six-stage resonator filter having a <NUM>-by-<NUM> array of cavities between an input terminal and an output terminal, where each cavity has a respective resonator therein. The resonator filter also includes a conductive housing, which defines a portion of the outer conductors of each of the resonators. The remainder of each resonator outer conductor is formed by interior common walls. The resonators may comprise, for example, either air-filled cavity resonators or dielectric-loaded coaxial resonators.

<FIG> of the present application shows a prior art RF filter <NUM> having resonators R that are inside a housing <NUM> and connector ports P that are on the outside of the housing <NUM>. For example, the filter <NUM> may include fourteen resonators R between the ports P. To simplify the illustration, however, only three resonators R are shown.

An interior wall <NUM> extends inside the housing <NUM> between groups of resonators R. An upper surface of the interior wall <NUM> includes holes <NUM> for screws for attaching a tuning cover to the interior of the filter <NUM>, and an upper surface of a perimeter defined by outer walls of the housing <NUM> includes holes <NUM> for screws for attaching an outer cover. The upper surface of the perimeter also includes a channel <NUM> for a gasket, such as an O-ring, that loops around the housing <NUM>.

The filter <NUM>, however, may be undesirably bulky and heavy. As an example, the filter <NUM> may have a length of <NUM> millimeters (mm) in a direction Y, a width of <NUM> in a direction X, and a height of <NUM> in a direction that is perpendicular to the directions X and Y.

Moreover, the filter <NUM> may have a volume of <NUM> liters and a weight of <NUM> kilograms (kg).

Patent document <CIT> discloses a coaxial cavity filter with a tuning cover and a housing outer cover.

Patent document <CIT> discloses the use of conductive adhesives to bond together the housing and the cover of a resonator cavity filter.

Patent document <CIT> discloses cleaning holes in the cover of a resonator cavity filter for removing debris from the filter interior.

A filter device, according to the embodiments of the invention, includes a housing. The filter device includes a plurality of resonators inside the housing. The filter device includes a wall inside the housing between a first of the resonators and a second of the resonators, and an average thickness of the wall is <NUM> or thinner. The filter device includes an outer cover on the housing. The filter device includes adhesive tape that attaches the outer cover to the housing. The filter device includes a tuning cover between the resonators and the outer cover. Moreover, the filter device includes a plurality of cleaning holes in the tuning cover.

In some embodiments, a lower surface of the outer cover may be attached to a flat upper surface of the housing by the adhesive tape. The outer cover and the flat upper surface of the housing may each free of any screw therein. Moreover, the adhesive tape may extend in a continuous loop on the flat upper surface of the housing.

According to some embodiments, the tuning cover may include a plurality of blind holes therein. A plurality of press-in standoffs may be in the blind holes, respectively. Moreover, the filter device may include a gas-discharge circuit. A first of the press-in standoffs may extend through a printed circuit board ("PCB") that includes the gas-discharge circuit.

In some embodiments, the filter device may include a plurality of non-debris tuning elements in the tuning cover. Moreover, the outer cover may be a flat metal sheet.

According to some embodiments, the average thickness of the wall may be <NUM> or thinner. The filter device may have fewer than fourteen of the resonators. The first and the second of the resonators may be configured to operate in a receive frequency band and a transmit frequency band, respectively. Moreover, a third of the resonators may be a broadband resonator that is configured to operate in both the receive frequency band and the transmit frequency band.

A filter device, according to some embodiments herein, may include resonators and a cover that is attached by double-sided adhesive tape to a housing that includes the resonators. In some embodiments, the double-sided adhesive tape may extend continuously around a perimeter of the housing.

According to some embodiments, the housing may include four exterior walls that collectively surround the resonators. The four exterior walls may have respective flat upper surfaces that are each free of any opening therein. The double-sided adhesive tape may be on the respective flat upper surfaces of the four exterior walls and on an opposite, lower surface of the cover. Moreover, the filter device may include an interior wall that is inside the housing and is between a first of the resonators and a second of the resonators.

In some embodiments, a thickness of the cover may be <NUM> or thinner. Moreover, the cover may be an outer cover of the filter device, and the filter device may include a tuning cover between the resonators and the outer cover. The filter device may include a cleaning hole and/or a non-debris tuning element in the tuning cover.

A filter device, according to some embodiments herein, may include resonators and a tuning cover that overlaps the resonators and has cleaning holes therein. In some embodiments, the filter device may include a housing including the resonators and the tuning cover therein. The filter device may include an outer cover that is attached to the housing by double-sided adhesive tape. Moreover, the filter device may include a non-debris tuning element in a hole in the tuning cover, and each of the cleaning holes may have a diameter that is narrower than a diameter of the hole that the non-debris tuning element is in.

A filter device, according to some embodiments herein, may include a housing and a plurality of resonators inside the housing. Moreover, the filter device may include a wall inside the housing between a first of the resonators and a second of the resonators. An average thickness of the wall may be <NUM> or thinner.

In some embodiments, the average thickness of the wall may be <NUM>-<NUM>, <NUM>-<NUM>, or <NUM>-<NUM>. Moreover, the wall may be an interior wall, the housing may include four exterior walls that collectively surround the resonators and the interior wall, and the four exterior walls may have respective flat upper surfaces that are each free of any opening therein.

A method of manufacturing an RF filter device may include pressing a plurality of press-in standoffs into a plurality of blind holes, respectively, that are in an upper surface of a tuning cover. The method may include soldering a lower surface of the tuning cover that is opposite the upper surface to an interior of the RF filter device. The method may include cleaning, via a plurality of cleaning holes that extend through the tuning cover, the interior of the RF filter device after performing the soldering. Moreover, the method may include attaching, by adhesive tape, a lower surface of an outer cover to an upper surface of a housing of the RF filter device after performing the cleaning.

Pursuant to embodiments of the present inventive concepts, RF filter devices, such as diplexers or duplexers that include a plurality of resonators, are provided. Conventional RF filters, such as the filter <NUM> (<FIG>), may each have dozens of screws that fasten covers to the filters. In addition to the screws, conventional filters may each include an O-ring, such as a silicon O-ring in a channel <NUM> (<FIG>) of an upper surface of a housing <NUM> (<FIG>) of the filter <NUM>. To accommodate the screws and the O-ring, conventional filters may have relatively thick interior and exterior walls.

According to embodiments of the present inventive concepts, however, RF filters having reduced size are provided. For example, a filter may, in some embodiments, achieve thinner exterior walls by using (a) adhesive tape instead of (b) screws to attach an outer cover to a housing of the filter. Because screws are not necessary to attach the outer cover, holes <NUM> (<FIG>) may be omitted from a perimeter defined by upper surfaces of the exterior walls of the housing <NUM> of the conventional filter <NUM>, thus allowing the exterior walls to be thinner. Moreover, the tape may extend continuously around the upper surface to seal the filter and thus may replace the O-ring and its corresponding channel <NUM>, thereby further facilitating a thinning of the exterior walls. The thinner exterior walls can reduce both the dimensions and the weight of the filter.

The size of the filter can also be reduced by attaching a tuning cover to the inside of the filter primarily with solder rather than screws. As an example, solder may be used in place of some (or all) of the screws and corresponding holes <NUM> (<FIG>) of the interior wall <NUM> (<FIG>) of the conventional filter <NUM>. Solder may also be used in place of most of the screws and corresponding holes of perimeter walls that are between the exterior walls and the interior wall <NUM>. The interior and perimeter walls can thus be thinned, which can reduce both the dimensions and the weight of the filter.

Though it may be difficult to remove the tuning cover to clean the filter after the tuning cover is soldered to the inside of the filter, the filter may be cleaned without removing the tuning cover. The tuning cover includes cleaning holes through which excess solder flux or other debris can be removed while the tuning cover is joined to the inside of the filter. Moreover, non-debris tuning elements and press-in standoffs may be used in the tuning cover to reduce/prevent metal debris (e.g., shavings) inside the filter. The cleaning holes, the non-debris tuning elements, and/or the press-in standoffs may help to reduce/prevent the generation of passive intermodulation ("PIM") distortion when the filter is operated.

Example embodiments of the present inventive concepts will be described in greater detail with reference to the attached figures.

<FIG> is an exploded top perspective view of an RF filter <NUM> according to embodiments of the present inventive concepts. The filter <NUM> is a device that includes resonators R (<FIG>) between ports P. The resonators R are inside a housing <NUM>, and may be covered by an outer cover <NUM> and by a tuning cover <NUM> that is between the resonators R and the outer cover <NUM>. The outer cover <NUM>, which may be a top exterior (i.e., outermost) lid on the filter <NUM>, may be attached to the housing <NUM> by adhesive tape <NUM>.

<FIG> is an enlarged exploded top perspective view of a portion of the filter <NUM> (<FIG>). As shown in <FIG>, the tape <NUM> may attach an upper surface 210U of the housing <NUM> to a lower surface of the outer cover <NUM> that is opposite the upper surface 210U. For example, the tape <NUM> may be double-sided tape, such as a high-strength, double-sided acrylic foam tape that can bond a variety of materials, including metal surfaces. An example is <NUM>™ VHB™ tape. In some embodiments, the tape <NUM> may be non-conductive. Moreover, an upper surface of the outer cover <NUM>, as well as all side surfaces of the outer cover <NUM> and all side surfaces of the housing <NUM>, may not be contacted by (i.e., may be free of) the tape <NUM>.

The upper surface 210U may be a flat upper surface of an exterior wall 210W of the housing <NUM>. For example, the housing <NUM> may have a generally rectangular shape that is provided by four of the exterior walls 210W, which have respective flat upper surfaces 210U that are coplanar (in an X-Y plane) with each other. Moreover, the coplanar flat upper surfaces 210U may be connected to each other to provide a continuous flat upper surface 210U that extends continuously around a perimeter of the housing <NUM>. As an example, the continuous flat upper surface 210U may provide a rectangular border with a thickness in the X-Y plane of <NUM>. The tape <NUM> may likewise extend in a continuous loop (<FIG>) on the continuous flat upper surface 210U, thus enhancing adhesion and sealing between the housing <NUM> and the outer cover <NUM>.

The outer cover <NUM> and the upper surface 210U may not include (i.e., may each be free of) any screw therein. Accordingly, in contrast with outer covers of conventional RF filters, such as the filter <NUM> (<FIG>), the outer cover <NUM> may be attached to the housing <NUM> by the tape <NUM> rather than by screws. Moreover, the outer cover <NUM> may have flat opposite upper and lower surfaces. For example, the outer cover <NUM> may be a flat metal sheet. As a result, the upper surface 210U may be thinner in the X-Y plane than it would be if it received screws, and the flat outer cover <NUM> may have a thickness 240T of only <NUM> or thinner in a direction Z, which may be perpendicular to the direction X and the direction Y. For example, the dimensions of the outer cover <NUM> may be <NUM> in length in the direction Y, <NUM> in width in the direction X, and <NUM> in height/thickness 240T in the direction Z. The flat outer cover <NUM> may thus be thinner than conventional ribbed outer covers.

In some embodiments, the filter <NUM> may provide a compact filter for small cell applications, such as small cell base stations, which are discussed in <CIT>. The filter <NUM> is not limited to small cell applications, however, and may, in some embodiments, be used for macro cell applications, such as macro cell base stations.

<FIG> is a top view of the inside of the filter <NUM>. As shown in <FIG>, the filter <NUM> may include a first group of resonators R-TX1 through R-TX5 and a second group of resonators R-RX1 through R-RX6. An interior wall <NUM> may extend inside the housing <NUM> (<FIG>) between the first and second resonator groups, thus defining different cavities inside the housing <NUM> for the two groups, which may be configured to operate in different respective frequency bands.

For example, the resonators R-TX1 through R-TX5 may be configured to operate in a transmit frequency band, such as <NUM>-<NUM> megahertz ("MHz") or a portion thereof, and the resonators R-RX1 through R-RX6 may be configured to operate in a receive frequency band, such as <NUM>-<NUM> or a portion thereof. As an example, the filter <NUM> may be a diplexer or duplexer 200D in which the resonators R-TX1 through R-TX5 provide a transmit-only filter and the resonators R-RX1 through R-RX6 provide a receive-only filter. Moreover, the filter <NUM> may, in some embodiments, include a broadband resonator R-B that is configured to operate in both the receive frequency band and the transmit frequency band. Collectively, the resonators R-B, R-TX1 through R-TX5, and R-RX1 through R-RX6 may be referred to herein as resonators R.

The resonators R may have circular conductive upper surfaces in the X-Y plane. As an example, the resonators R may be steel and may be electrically connected to one or more ports P via conductive lines, such as copper strip lines.

The resonators R-B and R-TX1 through R-TX5 may provide two transmission zeros in the receive frequency band. Moreover, the resonators R-B and R-RX1 through R-RX6 may provide three transmission zeros in the transmit frequency band.

In both the receive frequency band and the transmit frequency band, the filter <NUM> may typically have an insertion loss of <NUM> decibels ("dB") and a maximum insertion loss of <NUM> dB. The filter <NUM> may typically have a return loss in the receive frequency band and the transmit frequency band of <NUM> dB and a minimum return loss of <NUM> dB. Moreover, the filter <NUM> may typically have rejection of <NUM> dB and a minimum rejection of <NUM> dB, in both the receive frequency band and the transmit frequency band.

In the receive frequency band, the filter <NUM> may typically have a group delay of <NUM> nanoseconds ("ns") and a maximum group delay of <NUM> ns. In the transmit frequency band, the filter <NUM> may typically have a group delay of <NUM> ns and a maximum group delay of <NUM> ns.

<FIG> also illustrates that the tape <NUM> may extend in a continuous loop on the housing <NUM>, which may define a rectangular perimeter that surrounds the resonators R. For example, four exterior walls 210W (<FIG>) of the housing <NUM> may collectively surround the resonators R, and the tape <NUM> may be on respective flat upper surfaces 210U (<FIG>) of the four exterior walls 210W. The flat upper surfaces 210U may each be free of any opening therein, as they include neither the holes <NUM> (<FIG>) nor the channel <NUM> (<FIG>) of the conventional housing <NUM> (<FIG>). As a result, the housing <NUM> may be thinner, and thus more lightweight, than the conventional housing <NUM>.

In some embodiments, the housing <NUM> may be a metal housing. For example, a single machined or die-cast piece may, in some embodiments, comprise the exterior walls 210W and/or a bottom surface of the housing <NUM>. Accordingly, the flat upper surfaces 210U may be metal surfaces. Moreover, the ports P may be on the exterior walls 210W. As an example, the ports P may include two ports that protrude outward from a first of the exterior walls 210W in the direction Y and one port that protrudes outward from an opposite second of the exterior walls 210W. The two ports on the first of the exterior walls 210W may be electrically connected to the first group of resonators R-TX1 through R-TX5 and the second group of resonators R-RX1 through R-RX6, respectively.

Though five resonators R are shown in the first group and six resonators R are shown in the second group, more (i.e., six, seven, or more) or fewer (e.g., three, four, or five) resonators R may be included in either group. In some embodiments, the weight and dimensions of the filter <NUM> may be advantageously reduced relative to the conventional filter <NUM> (<FIG>) by having fewer than fourteen total resonators R. For example, by having a total of twelve resonators R in the filter <NUM> rather than fourteen, the weight and volume of the filter <NUM> may each be reduced by at least five percent.

As an example, by having (a) twelve resonators R, (b) the thin interior wall <NUM>, and (c) the thin exterior wall 210W, the filter <NUM> may have a length of <NUM> in the direction Y, a width of <NUM> in the direction X, and a height of <NUM> in the direction Z. The filter <NUM> may also have a volume of <NUM> liters and a weight of <NUM>. Accordingly, the weight and volume of the filter <NUM> may each be reduced by at least forty percent relative to the conventional filter <NUM>.

In some embodiments, one of the twelve resonators R may be a broadband resonator R-B. Moreover, to achieve small dimensions, the twelve resonators R may be arranged along the direction Y in four rows that each have three resonators R. By contrast, if one of the rows instead has four resonators R, then the length and/or the width of the filter <NUM> may increase. For example, the filter <NUM> may have a length of <NUM>, a width of <NUM>, a height of <NUM>, a volume of <NUM> liters, and a weight of <NUM> if one of the rows has four resonators R arranged along the direction Y. Moreover, if fourteen resonators R are used instead of twelve, then the filter <NUM> may have a length of <NUM>, a width of <NUM>, a height of <NUM>, a volume of <NUM> liters, and a weight of <NUM>.

The filter <NUM> may include tuning elements <NUM>/<NUM>. For example, tuning elements <NUM> may be between a pair of adjacent resonators R, and tuning elements <NUM> may be in the resonators R. As an example, the tuning elements <NUM> may be in center portions (e.g., openings) of respective resonators R. The tuning elements <NUM>/<NUM> may be metal tuning elements or dielectric tuning elements, such as metal tuning screws or dielectric tuning screws. Both a dielectric tuning element and a metal tuning element can change capacitive coupling(s) (a) between resonators R and/or (b) between resonators R and the housing <NUM>.

Example tuning elements are discussed in <CIT> ("the '<NUM> application'). In some embodiments, the tuning elements <NUM>/<NUM> may be tuning elements that prevent/reduce metal debris formation, such as the tuning elements discussed in the '<NUM> application, and thus may be referred to herein as "non-debris" tuning elements. For example, a contact portion of each of the tuning elements <NUM>/<NUM> may be free of threading. In some embodiments, a diameter in the X-Y plane of a top surface of each tuning element <NUM> may be narrower than a diameter in the X-Y plane of a top surface of each tuning element <NUM>.

One or more PCBs <NUM> may be inside the filter <NUM> at a level in the direction Z that is above the resonators R. For example, the PCB(s) <NUM> may be attached to an upper surface 250U (<FIG>) of the tuning cover <NUM>. Though the tuning cover <NUM> is typically a metal (e.g., aluminum) lid that intervenes between the resonators R and the PCB(s) <NUM>, the tuning cover <NUM> is depicted transparently in <FIG> for ease of illustrating the underlying resonators R and interior wall <NUM>.

<FIG> is an enlarged top view of the interior wall <NUM> (<FIG>). As shown in <FIG>, the interior wall <NUM> may have an average thickness 220T in the X-Y plane. The average thickness 220T may be <NUM> or thinner. For example, the average thickness 220T may be <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, or <NUM> or thinner. In particular, the average thickness 220T may be thinner than a corresponding average thickness of the interior wall <NUM> (<FIG>) of the conventional filter <NUM> (<FIG>) because an upper surface of the interior wall <NUM> has fewer (or none) of the holes <NUM> (<FIG>) for screws, which may be in portions of the interior wall <NUM> that are at least <NUM> thick in the X-Y plane. For example, with the exception of a few locations where multiple branches of the interior wall <NUM> converge, the interior wall <NUM> may be free of any opening in an upper surface thereof. The reduced thickness of the interior wall <NUM> may advantageously facilitate smaller dimensions and a lighter weight of the filter <NUM>.

<FIG> is a top view of the inside of the filter <NUM> (<FIG>). The tuning cover <NUM> overlaps the resonators R (<FIG>) and includes tuning elements <NUM>/<NUM> that affect capacitive coupling(s) between the resonators R. In some embodiments, the tuning cover <NUM> may include cleaning holes <NUM> that facilitate cleaning of the filter <NUM> without needing to remove the tuning cover <NUM> from the housing <NUM>. For example, an ultrasonic machine may be used to inject and extract a cleaning liquid via the cleaning holes <NUM> to clean (e.g., to remove debris from) the filter <NUM>. By contrast, a conventional tuning cover must be removed to clean debris that may result from tuning (e.g., from rotating a tuning screw in the tuning cover) of the conventional filter <NUM> (<FIG>). Because the tuning elements <NUM>/<NUM> may be non-debris tuning elements, however, the cleaning holes <NUM> may, in some embodiments, be omitted.

In some embodiments, the tuning cover <NUM> may include both (i) cleaning holes <NUM> and (ii) non-debris tuning elements <NUM>/<NUM>. As an example, the cleaning holes <NUM> may advantageously facilitate cleaning of the filter <NUM> upon detecting a PIM failure, which may not necessarily be caused by the tuning elements <NUM>/<NUM>. Moreover, excess solder flux, which may result from joining the tuning cover <NUM> to the interior of the housing <NUM>, may be removed via the cleaning holes <NUM>.

Rather than using a large number (e.g., dozens) of screws to attach the tuning cover <NUM> inside the housing <NUM> (<FIG>), the tuning cover <NUM> may be joined to the interior of the filter <NUM> by heating various welding areas 250W of the tuning cover <NUM>. For example, the welding areas 250W may include a perimeter of the tuning cover <NUM> and a portion of the tuning cover <NUM> that overlaps the interior wall <NUM> (<FIG>). Accordingly, the tuning cover <NUM> may be welded/soldered to an interior perimeter of the filter <NUM> and to the interior wall <NUM>. Though referred to herein as "welding" areas 250W, the areas 250W may be welded, soldered, or otherwise heated to join the tuning cover <NUM> to the interior of the housing <NUM>. Examples of soldered connections are discussed in <CIT>.

In some embodiments, screws S may extend through the tuning cover <NUM> to inhibit movement of the tuning cover <NUM> that may otherwise occur during welding/soldering thereof. For example, one or more of the screws S may be in the welding areas 250W, and one or more others of the screws S may be in a middle portion of the tuning cover <NUM>. The tuning cover <NUM> may, in some embodiments, include a total of ten or fewer screws S. By contrast, the conventional filter <NUM> (<FIG>) may typically have <NUM>-<NUM> screws that fasten a tuning cover to the housing <NUM> (<FIG>). A top surface of each of the screws S may have a smaller diameter in the X-Y plane than a diameter in the X-Y plane of a top surface of each tuning element <NUM>/<NUM>.

<FIG> is an enlarged top view of a portion of the tuning cover <NUM> (<FIG>). As shown in <FIG>, the cleaning holes <NUM> may be adjacent a welding area 250W and/or a screw S. For example, corner regions of the tuning cover <NUM> may each include a pair of cleaning holes <NUM>, a welding area 250W, and a screw S.

A lower surface of the tuning cover <NUM> is the surface that is joined to the interior of the filter <NUM>. The depiction of the welding areas 250W in <FIG>, which show an upper surface 250U of the tuning cover <NUM> that is opposite the lower surface, thus represents locations on the upper surface 250U that are heated to join corresponding areas of the lower surface to the interior wall <NUM> (<FIG>) and to a perimeter wall <NUM> (<FIG>). For example, a stencil may be used to apply a low-temperature solder paste to upper surfaces of the interior wall <NUM> and the perimeter wall <NUM>, and/or to the lower surface of the tuning cover <NUM>. The welding areas 250W may then be heated to join the lower surface of the tuning cover <NUM> to the upper surfaces of the interior wall <NUM> and the perimeter wall <NUM> via the solder paste. The solder paste may increase galvanic contact between (a) the tuning cover <NUM> and (b) the interior wall <NUM> and the perimeter wall <NUM>.

<FIG> is an exploded top perspective view of a PCB <NUM> that is attached to the tuning cover <NUM> (<FIG>). In particular, <FIG> illustrates that each PCB <NUM> may be attached to the tuning cover <NUM> by one or more press-in standoffs <NUM>. The standoffs <NUM> may be pressed by a tool into respective blind holes 250BH that are in the upper surface 250U of the tuning cover <NUM> and that do not extend completely through the tuning cover <NUM>. By contrast, in the conventional filter <NUM> (<FIG>), a PCB may be fastened via conventional downward-facing threaded screws to a conventional tuning cover, thereby generating metal debris inside the filter <NUM>. The standoffs <NUM> and the blind holes 250BH can thus advantageously prevent/reduce metal debris that may otherwise be generated when penetrating a tuning cover with conventional threaded screws.

In some embodiments, the PCB <NUM> may comprise a gas-discharge circuit <NUM> adjacent each port P (<FIG>). Moreover, the standoffs <NUM> may extend through holes <NUM> in the PCB <NUM>.

<FIG> is a side perspective view of a press-in standoff <NUM> (<FIG>). As shown in <FIG>, the standoff <NUM> may be free of threading and thus may help to prevent/reduce metal debris inside the filter <NUM>. In some embodiments, the standoff <NUM> may comprise a metal alloy, such as brass.

<FIG> is a top perspective view of the tuning cover <NUM> (<FIG>) with tuning elements <NUM> and <NUM> (<FIG>) omitted from view. <FIG> illustrates press-in standoffs <NUM> that have been pressed into the upper surface 250U of the tuning cover <NUM>. Moreover, <FIG> illustrates holes <NUM> for the tuning elements <NUM> and holes <NUM> for the tuning elements <NUM>. Unlike the blind holes 250BH (<FIG>) that the standoffs <NUM> are pressed into, the holes <NUM> and <NUM> extend completely through the tuning cover <NUM>.

<FIG> is a top perspective view of the tuning cover <NUM> (<FIG>) with tuning elements <NUM> and <NUM> shown. The tuning elements <NUM> and <NUM> may extend completely through the tuning cover <NUM> via the holes <NUM> and <NUM> (<FIG>), respectively, to affect capacitive coupling(s) between, for example, resonators R (<FIG>). As discussed herein, however, the tuning elements <NUM> and <NUM> may be non-debris tuning elements that prevent/reduce metal debris inside the filter <NUM>.

<FIG> also shows cleaning holes <NUM>, as well as holes <NUM> for screws S (<FIG>). The cleaning holes <NUM> may, in some embodiments, have a wider diameter than the holes <NUM> and a narrower diameter than the holes <NUM> and <NUM>.

<FIG> is a top perspective view of the housing <NUM> (<FIG>). As shown in <FIG>, a perimeter wall <NUM> may be inside the housing <NUM> between the interior wall <NUM> and the exterior wall 210W. For example, the perimeter wall <NUM>, which is shorter in the direction Z than the exterior wall 210W, may, in some embodiments, be integrated with (e.g., attached to or formed from the same piece of metal as) the exterior wall 210W. The perimeter wall <NUM> may include holes <NUM> for screws S (<FIG>) that extend completely through the holes <NUM> (<FIG>) and into the holes <NUM> to fasten the tuning cover <NUM> (<FIG>) to the perimeter wall <NUM>.

Welding areas 250W (<FIG>) that are on a perimeter of the tuning cover <NUM> may be heated to join the lower surface of the tuning cover <NUM> to the upper surface of the perimeter wall <NUM>, and other welding areas 250W that are in a middle portion of the tuning cover 250W may be heated to join the lower surface of the tuning cover <NUM> to the upper surface of the interior wall <NUM>. For example, the upper surface of the perimeter wall <NUM> and the upper surface of the interior wall <NUM> may be coplanar with each other in the X-Y plane, and thus may provide a shelf/ledge for the tuning cover <NUM> inside the housing <NUM>. Moreover, the upper surface 250U (<FIG>) of the tuning cover <NUM> may be lower in the direction Z than the upper surface 210U of the exterior wall 210W of the housing <NUM>.

In some embodiments, the perimeter wall <NUM> may surround the resonators R. For example, the perimeter wall <NUM> may comprise four walls/sides that provide a rectangular perimeter around the resonators R. Moreover, the interior wall <NUM> may protrude from the perimeter wall <NUM> toward a middle portion inside the housing <NUM>.

<FIG> is a flowchart illustrating operations of manufacturing an RF filter device <NUM> (<FIG>). The operations may include pressing (Block <NUM>) a plurality of press-in standoffs <NUM> (<FIG>) into a plurality of blind holes 250BH (<FIG>), respectively, that are in an upper surface 250U (<FIG>) of a tuning cover <NUM> (<FIG>). The operations may include soldering (Block <NUM>), or otherwise using heat to join, a lower surface of the tuning cover <NUM> that is opposite the upper surface 250U to an interior of the filter <NUM>. The operations may include cleaning (Block <NUM>), via a plurality of cleaning holes <NUM> (<FIG>) that extend through the tuning cover <NUM>, the interior of the filter <NUM> after performing the soldering. Moreover, the operations may include attaching (Block <NUM>), by adhesive tape <NUM> (<FIG>), a lower surface of an outer cover <NUM> (<FIG>) to an upper surface 210U (<FIG>) of a housing <NUM> (<FIG>) of the filter <NUM> after performing the cleaning. In some embodiments, the operations may include adjusting tuning elements <NUM>/<NUM> (<FIG>) in the tuning cover <NUM> and/or performing a PIM test of the filter <NUM>.

An RF filter device <NUM> (<FIG>) according to embodiments of the present inventive concepts may provide a number of advantages. These advantages, relative to the conventional filter <NUM> (<FIG>), include reduced size (e.g., dimensions and weight) due to (a) attaching the outer cover <NUM> (<FIG>) to the upper surface 210U (<FIG>) of the housing <NUM> (<FIG>) via tape <NUM> (<FIG>) instead of screws, (b) soldering the tuning cover <NUM> (<FIG>) to the interior wall <NUM> (<FIG>) and/or to the perimeter wall <NUM> (<FIG>), (c) using an outer cover <NUM> that is flat rather than ribbed, and/or (d) having twelve or fewer resonators R (<FIG>) inside the filter <NUM>. Moreover, the present inventive concepts can reduce/prevent PIM by (i) including the cleaning holes <NUM> (<FIG>), (ii) the non-debris tuning elements <NUM>/<NUM> (<FIG>), and/or (iii) the press-in standoffs <NUM> (<FIG>) and blind holes 250BH (<FIG>) in the tuning cover <NUM>.

The present inventive concepts have been described above with reference to the accompanying drawings. The present inventive concepts are not limited to the illustrated embodiments. Rather, these embodiments are intended to fully and completely disclose the present inventive concepts to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

Spatially relative terms, such as "under," "below," "lower," "over," "upper," "top," "bottom," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. For example, if the device in the figures is turned over, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the example term "under" can encompass both an orientation of over and under.

Herein, the terms "attached," "connected," "interconnected," "contacting," "mounted," and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.

As used herein the expression "and/or" includes any and all combinations of one or more of the associated listed items.

Claim 1:
A filter device (<NUM>) comprising:
a housing (<NUM>);
a plurality of resonators (R) inside the housing;
a wall (<NUM>) inside the housing between a first of the resonators and a second of the resonators, wherein an average thickness of the wall is <NUM> or thinner;
an outer cover (<NUM>) on the housing;
adhesive tape (<NUM>) that attaches the outer cover to the housing;
a tuning cover (<NUM>) between the resonators and the outer cover; and
a plurality of cleaning holes (<NUM>) in the tuning cover.