An apparatus includes a filter. The filter includes a metal structure forming a cavity and includes a ceramic block, which is suspended in the cavity. The ceramic block has two removed portions, the removed portions removed from two opposing sides of the ceramic block. The ceramic block further has one or more slots that that span a region of ceramic between the two removed portions and connects chambers formed by the two regions with chambers formed by the one or more slots, wherein a combined structure of the ceramic block, cavity, and metal structure supports multiple fundamental TM modes and one fundamental TE mode. The filter comprises multiple coupling structures to couple radio frequency signals into and out of the filter. The apparatus may include multi-cavity filters including one and typically multiple ones of the filters.

When a plurality of RF signals having different frequency bands are output at the same time by carrier aggregation, a switch element allows parallel connection between two capacitance elements such that a low pass filter has a first cut-off frequency that is lower than the frequency of an intermodulation distortion signal generated by the carrier aggregation. When an RF signal of a frequency band is output, the switch element releases parallel connection between the two capacitance elements such that the low pass filter has a second cut-off frequency that is higher than the first cut-off frequency.

When a plurality of RF signals having different frequency bands are output at the same time by carrier aggregation, a switch element allows parallel connection between two capacitance elements such that a low pass filter has a first cut-off frequency that is lower than the frequency of an intermodulation distortion signal generated by the carrier aggregation. When an RF signal of a frequency band is output, the switch element releases parallel connection between the two capacitance elements such that the low pass filter has a second cut-off frequency that is higher than the first cut-off frequency.

An RF filter includes: an electrical conductor defining an outer sphere; a dielectric material defining an inner sphere disposed within the conductor outer sphere; and at least a first electrical probe and a second electrical probe. Each probe extends through the conductor and is electrically insulated from it. A spherical shape of one or both of the inner and outer spheres is interrupted by: a) a first localized discontinuity in said spherical shape disposed along a first axis passing through a geometric center of the one or both of the inner and outer spheres; and b) a second localized discontinuity in said sphere form disposed along a second axis passing through the geometric center, the second axis perpendicular to the first axis. There can be more than these two discontinuities, implemented as chamfers, tuning screws, and the like. Series and parallel coupling of the spheres is detailed.

An RF filter includes: an electrical conductor defining an outer sphere; a dielectric material defining an inner sphere disposed within the conductor outer sphere; and at least a first electrical probe and a second electrical probe. Each probe extends through the conductor and is electrically insulated from it. A spherical shape of one or both of the inner and outer spheres is interrupted by: a) a first localized discontinuity in said spherical shape disposed along a first axis passing through a geometric center of the one or both of the inner and outer spheres; and b) a second localized discontinuity in said sphere form disposed along a second axis passing through the geometric center, the second axis perpendicular to the first axis. There can be more than these two discontinuities, implemented as chamfers, tuning screws, and the like. Series and parallel coupling of the spheres is detailed.

A radio frequency filter with a cavity structure is provided. The radio frequency filter includes a housing having an inner hollow portion to have a cavity and open from one side of the housing, a cover sealing the open side of the housing, and a resonant element disposed inside the hollow housing. A through hole is formed at a part of the cover, corresponding to the resonant element, and a tuning element is installed covering the through hole, for frequency tuning. The tuning element is formed of a material having a different thermal expansion coefficient from a thermal expansion coefficient of a material of the cover.

A radio frequency filter with a cavity structure is provided. The radio frequency filter includes a housing having an inner hollow portion to have a cavity and open from one side of the housing, a cover sealing the open side of the housing, and a resonant element disposed inside the hollow housing. A through hole is formed at a part of the cover, corresponding to the resonant element, and a tuning element is installed covering the through hole, for frequency tuning. The tuning element is formed of a material having a different thermal expansion coefficient from a thermal expansion coefficient of a material of the cover.

A rod-switched tunable resonator includes a housing defining a cavity, a first rod disposed within the cavity, a second rod disposed within the cavity, and a switch connected to the first rod and to the second rod to tune the resonator to one of a plurality of frequencies by connecting or disconnecting one or both of the first and second rods to the housing. A tunable filter may be fabricated using two or more such resonators. The rod-switched tunable resonator may be a combline resonator, coaxial resonator, waveguide resonator, or dielectric resonator.

A rod-switched tunable resonator includes a housing defining a cavity, a first rod disposed within the cavity, a second rod disposed within the cavity, and a switch connected to the first rod and to the second rod to tune the resonator to one of a plurality of frequencies by connecting or disconnecting one or both of the first and second rods to the housing. A tunable filter may be fabricated using two or more such resonators. The rod-switched tunable resonator may be a combline resonator, coaxial resonator, waveguide resonator, or dielectric resonator.

The present disclosure relates to a dielectric coupling sleeve configured to capacitively couple a first electrical conductor to a second electrical conductor. The dielectric coupling sleeve includes a first sleeve section and a second sleeve section. The first sleeve section has a first diameter. A receiving space is closed on one side and formed in the first sleeve section. The receiving section is configured to receive an insertion of the first electrical conductor. The second sleeve section has a second diameter. The second diameter is smaller than the first diameter. The second sleeve section is configured for insertion into the conductor cavity of the second electrical conductor.