A multiplexer includes: a first terminal; a second terminal; a third terminal; a first filter connected between the first and second terminals, including a first capacitor, a first inductor, and one or more first acoustic wave resonators, and having a first passband; a second filter connected between the first and third terminals, including a second capacitor, a second inductor, and one or more second acoustic wave resonators, and having a second passband higher than the first passband; a substrate having a surface on which at least one first acoustic wave resonator of the one or more first acoustic wave resonators and at least one second acoustic wave resonator of the one or more second acoustic wave resonators are located; and a metal structure located on the surface and located between the at least one first acoustic wave resonator and the at least one second acoustic wave resonator.

A formation method of a filter device includes: forming a first layer by providing a first substrate and forming a resonance device preprocessing layer with a first side and a second side opposite to the first side, wherein the first substrate is located on the first side; forming a second layer by providing a second substrate and forming a first passive device with a third side and a fourth side opposite to the third side, wherein the second substrate is located on the third side; connecting the first layer located on the fourth side and the second layer located on the second side; removing the first substrate; and forming at least one first resonance device based on the resonance device preprocessing layer. The resonance device and the passive device are integrated in one die to form a filter device, which requires less space in an RF front-end chip.

A diplexer includes dielectric layers stacked in a lamination direction. The diplexer includes a reference surface extending in a direction orthogonal or substantially orthogonal to the lamination direction, a common terminal on the reference surface, a high-pass circuit including a capacitor, a low-pass circuit including an inductor, a common line connecting the common terminal and a branch portion, a first via connecting the branch portion and the capacitor in the high-pass circuit, and a second via connecting the branch portion and the inductor in the low-pass circuit. The first via extends along the lamination direction from a first layer where the branch portion is located to a second layer where the capacitor in the high-pass circuit is located.

A frontend module includes a first filter having a passband of a first frequency band, a second filter having a passband of a second frequency band, the second frequency band being higher than the first frequency band, a third filter having a passband of a third frequency band, the third frequency band being higher than the second frequency band, and a sub-filter, connected to the second filter, configured to provide attenuation characteristics for the first frequency band, wherein the second filter comprises a plurality of parallel LC resonance circuits arranged between a ground and different nodes, from among a plurality of nodes between a first terminal and a second terminal, wherein an inductor is connected to a portion of the plurality of parallel LC resonance circuits.

A filter assembly is disclosed that includes a monolithic filter having a surface and a heat sink coupled to the surface of the monolithic filter. The heat sink includes a layer of thermally conductive material that can have a thickness greater than about 0.02 mm. The heat sink may provide electrical shielding for the monolithic filter. In some embodiments, the filter assembly may include an organic dielectric material, such as liquid crystalline polymer or polyphenyl ether. In some embodiments, the filter assembly may include an additional monolithic filter.

A variable filter for an RF circuit has a signal loop comprising a signal input port and a signal output port, and a plurality of circuit elements connected within the signal loop. The plurality of circuit elements comprise a multi-pole resonator comprising a plurality of frequency tunable resonators and an adjustable scaling block that applies a gain factor. Adjacent frequency tunable resonators within the multi-pole resonator are reciprocally coupled. A controller is connected to tune the multi-pole resonator and to adjust the gain factor of the adjustable scaling block such that the signal loop generates a desired bandpass response.

A system of at least two units that transmit and/or receive a signal at a first or a second frequency, respectively, each of the units being individually connected to the antenna, which is common to a first branch and to a second branch, respectively. The first branch or the antenna includes first passive electronics preventing passage of the signal at the second frequency to the first unit and allowing passage of the signal at the first frequency to the antenna. The second branch or the antenna includes second passive electronics preventing passage of the signal at the first frequency to the second unit and allowing passage of the signal at the second frequency to the antenna.

Examples provide a wideband filter structure and apparatus, a radio transceiver, a mobile terminal, and a method for filtering a radio signal. The wideband filter structure (10) for a radio signal comprises a combination of at least one acoustic resonator (12) and at least one analog resonator (14). The acoustic resonator (12) is coupled to the analog resonator (14). The wideband filter structure (10) comprises a further component (16), which is coupled to the combination of the acoustic resonator (12) and the analog resonator (14).

A frontend module includes a first filter having a passband of a first frequency band, a second filter having a passband of a second frequency band, the second frequency band being higher than the first frequency band, a third filter having a passband of a third frequency band, the third frequency band being higher than the second frequency band, and a sub-filter, connected to the second filter, configured to provide attenuation characteristics for the first frequency band, wherein the second filter comprises a plurality of parallel LC resonance circuits arranged between a ground and different nodes, from among a plurality of nodes between a first terminal and a second terminal, wherein an inductor is connected to a portion of the plurality of parallel LC resonance circuits.

A method for reducing a quantity of cable runs to antennas can include the step of providing a circuit of reactive elements coupled between an input terminal and at least two output terminals. The circuit can be used to separate a broadband signal into two or more disjoint expected frequency ranges. The circuit can match the impedance at the at least two output terminals to the impedance expected by the antennas. The elements of the circuit can have reactances and arrangement so that when a broadband RF signal is applied at the input terminal, two or more disjoint expected frequencies can be applied to the respective output terminals. The power at each output terminal can sufficiently match the antennas' expected power, and insertion losses can be minimized.