A notch filter and a multi-frequency notch filter. The notch filter includes at least one notch filtering unit, each of the at least one notch filtering unit includes an input port, an output port, at least three resonators and at least one inductive element, and the at least three resonators include at least two first resonators and at least one second resonator. The at least two first resonators are connected in series to each other, the at least two first resonators in series are connected in series between the input port and the output port, a first end of each of the at least one second resonator is connected to a connection point between two adjacent first resonators, and a second end of the each of the at least one second resonator is connected to a fixed potential end.

A radio frequency module includes a mount board, an acoustic wave filter, a temperature sensor, and a correction circuit. The mount board has a first principal surface and a second principal surface on opposite sides of the mount board. The acoustic wave filter is disposed on the first principal surface side of the mount board. The temperature sensor is disposed on the second principal surface side of the mount board. The correction circuit corrects a pass band of the acoustic wave filter in accordance with a temperature measured by the temperature sensor.

A radio frequency module includes a mount board, an acoustic wave filter, a temperature sensor, and a correction circuit. The mount board has a first principal surface and a second principal surface on opposite sides of the mount board. The acoustic wave filter is disposed on the first principal surface side of the mount board. The temperature sensor is disposed on the second principal surface side of the mount board. The correction circuit corrects a pass band of the acoustic wave filter in accordance with a temperature measured by the temperature sensor.

A combination filter comprises a notch filter formed of acoustic wave resonators and a cavity filter electrically in series with the notch filter to provide for the combination filter to operate at higher powers and frequencies.

A system for filter enhancement, preferably including one or more analog taps and a controller, and optionally including one or more couplers. The system is preferably configured to integrate with a filter, such as a passband filter or other frequency-based filter. The system can be configured to integrate with an RF communication system, an RF front end, or any other suitable RF circuitry. A method for filter enhancement, preferably including configuring one or more analog taps, and optionally including calibrating a system for filter enhancement and/or receiving temperature information.

A high-frequency module includes a high-frequency switch, filters (21 to 23), (31 to 33), and connection circuits (41 to 46). The high-frequency switch has filter-side terminals (Ps1 to Ps 6). The filters (21, 22, 23) each include a plurality of filters having characteristics different from each other. The filters (31, 32, 33) each include one type of filter. The connection circuits (41, 42, 43) connect the terminals (Ps1, Ps2, Ps3) of the high-frequency switch to the common terminals (Pc21, Pc22, Pc23) of the filters (21, 22, 23), respectively. The connection circuits (44, 45, 46) connect the terminals (Ps4, Ps5, Ps6) of the high-frequency switch to the filters (31, 32, 33), respectively. The connection circuits (41, 42, 43) are shorter than the connection circuits (44, 45, 46).

A high-frequency module includes a high-frequency switch, filters (21 to 23), (31 to 33), and connection circuits (41 to 46). The high-frequency switch has filter-side terminals (Ps1 to Ps 6). The filters (21, 22, 23) each include a plurality of filters having characteristics different from each other. The filters (31, 32, 33) each include one type of filter. The connection circuits (41, 42, 43) connect the terminals (Ps1, Ps2, Ps3) of the high-frequency switch to the common terminals (Pc21, Pc22, Pc23) of the filters (21, 22, 23), respectively. The connection circuits (44, 45, 46) connect the terminals (Ps4, Ps5, Ps6) of the high-frequency switch to the filters (31, 32, 33), respectively. The connection circuits (41, 42, 43) are shorter than the connection circuits (44, 45, 46).

A filter includes a ladder filter including a first parallel arm resonator and a second parallel arm resonator, a longitudinally coupled resonator filter electrically connected in series to the ladder filter, a first ground terminal electrically connected to the first parallel arm resonator, a second ground terminal electrically connected to the second parallel arm resonator, a third ground terminal electrically connected to the longitudinally coupled resonator filter, a third signal path electrically connected to a first node on a first signal path electrically connecting the second parallel arm resonator to the second ground terminal and a second node on a second signal path electrically connecting the longitudinally coupled resonator filter to the third ground terminal, and an inductor electrically connected between the first node on the first signal path and the second ground terminal or between the second node on the second signal path and the third ground terminal.

A filter includes a ladder filter including a first parallel arm resonator and a second parallel arm resonator, a longitudinally coupled resonator filter electrically connected in series to the ladder filter, a first ground terminal electrically connected to the first parallel arm resonator, a second ground terminal electrically connected to the second parallel arm resonator, a third ground terminal electrically connected to the longitudinally coupled resonator filter, a third signal path electrically connected to a first node on a first signal path electrically connecting the second parallel arm resonator to the second ground terminal and a second node on a second signal path electrically connecting the longitudinally coupled resonator filter to the third ground terminal, and an inductor electrically connected between the first node on the first signal path and the second ground terminal or between the second node on the second signal path and the third ground terminal.

An electrical device (100) that comprises at least one signal filter (104) comprising a plurality of mechanical resonators (106 108, 110) in a substrate (102) and at least one further mechanical resonator (112) in the substrate (102) configured to oscillate at a reference frequency of an oscillator signal. An electrical system (300) comprising an electrical oscillator (306) a transceiver (302) and an antenna (310), and an electrical device (100). A method (1300) for providing an electrical device (100).