An improved electro acoustic RF filter (FC) is provided. The RF filter comprises an electro acoustic resonator (EAR) connected between an input port and an output port, an impedance element and a damping and/or dissipation element (DE) in mechanical contact to the impedance element. The damping and/or dissipation element is provided and configured to remove acoustic energy from the impedance element which has a similar construction as the resonator on the same substrate. With such a construction an acoustically inactive impedance element (AIIE) is obtained.

A filter circuit comprises a main operating unit (MU) arranged in the series signal line providing most of the filter function of the filter circuit. A micro acoustic last series resonator (RL.sub.s) as a last element of the main operating unit in the series signal line is prone to excite a spurious mode that is damped with a final series capacitance (CE.sub.s) circuited between the last element and the antenna terminal (AT).

A SAW transducer and a SAW resonator are proposed composed of consecutively arranged unit cells of length L. Slight geometry or material variations such as variations of the metallization ration or the unit cell length L affecting the pitch) between these unit cells result in improved spurious mode suppression while the main mode performance is unaffected.

A filter includes: a series-arm resonator; and a parallel-arm resonator. The series-arm resonator and the parallel-arm resonator each include: an interdigital transducer (IDT) electrode formed on a substrate and including a plurality of electrode fingers; and a protective film. The protective film included in the parallel-arm resonator is thinner than the protective film included in the series-arm resonator. The parallel-arm resonator has a first fractional bandwidth ((the higher-order resonance frequency−the resonant frequency)/the resonant frequency) greater than the first fractional bandwidth of the series-arm resonator. The parallel-arm resonator has a second fractional bandwidth ((the higher-order antiresonant frequency−the antiresonant frequency)/the antiresonant frequency) greater than the second fractional bandwidth of the series-arm resonator.

A multiplexer includes a filter arranged in a first path, a filter arranged in a second path, and a filter arranged in a third path, in which a frequency of intermodulation distortion (IMD) generated from a transmission signal in a pass band of the filter and a transmission signal in a pass band of the filter is included in a pass band of the filter. The filters includes one or more series arm resonant circuits arranged on the first path and one or more parallel arm resonant circuits arranged in a path connecting corresponding nodes on the first path and the ground, in which at least one resonant circuit among the resonant circuits closest to a common terminal in one or more series arm resonant circuits and one or more parallel arm resonant circuits is defined by a divided resonator group defined by multiple divided resonators connected in series.

A SAW element configured to suppress spurious emissions resulting from non-periodicity of an IDT electrode finger arrangement. In one example, the SAW element is a resonator comprising an IDT electrode including a first plurality of IDT electrode fingers connected to a first busbar and a second plurality of IDT electrode fingers connected to a second busbar, and reflectors having a plurality of reflector fingers. The pluralities of first and second IDT electrode fingers are alternatively connected to each busbar by either normal connections or reversed connections and include regions arranged by at least two different types of pitches. The normal connections are such that either the odd-numbered or even-numbered IDT electrode fingers connect to the first busbar, and the reversed connections are such that the opposite group of IDT electrode fingers connect to the first busbar.

A filter includes: a series-arm resonator; and a parallel-arm resonator. The series-arm resonator and the parallel-arm resonator each include: an interdigital transducer (IDT) electrode formed on a substrate and including a plurality of electrode fingers; and a protective film. The protective film included in the parallel-arm resonator is thinner than the protective film included in the series-arm resonator. The parallel-arm resonator has a first fractional bandwidth ((the higher-order resonance frequencythe resonant frequency)/the resonant frequency) greater than the first fractional bandwidth of the series-arm resonator. The parallel-arm resonator has a second fractional bandwidth ((the higher-order antiresonant frequencythe antiresonant frequency)/the antiresonant frequency) greater than the second fractional bandwidth of the series-arm resonator.

A multiplexer includes a filter arranged in a first path, a filter arranged in a second path, and a filter arranged in a third path, in which a frequency of intermodulation distortion (IMD) generated from a transmission signal in a pass band of the filter and a transmission signal in a pass band of the filter is included in a pass band of the filter. The filters includes one or more series arm resonant circuits arranged on the first path and one or more parallel arm resonant circuits arranged in a path connecting corresponding nodes on the first path and the ground, in which at least one resonant circuit among the resonant circuits closest to a common terminal in one or more series arm resonant circuits and one or more parallel arm resonant circuits is defined by a divided resonator group defined by multiple divided resonators connected in series.

A SAW element configured to suppress spurious emissions resulting from non-periodicity of an IDT electrode finger arrangement. In one example, the SAW element is a resonator comprising an IDT electrode including a first plurality of IDT electrode fingers connected to a first busbar and a second plurality of IDT electrode fingers connected to a second busbar, and reflectors having a plurality of reflector fingers. The pluralities of first and second IDT electrode fingers are alternatively connected to each busbar by either normal connections or reversed connections and include regions arranged by at least two different types of pitches. The normal connections are such that either the odd-numbered or even-numbered IDT electrode fingers connect to the first busbar, and the reversed connections are such that the opposite group of IDT electrode fingers connect to the first busbar.

A SAW element configured to suppress spurious emissions resulting from non-periodicity of an IDT electrode finger arrangement. In one example, the SAW element is a resonator comprising an IDT electrode including a first plurality of IDT electrode fingers connected to a first busbar and a second plurality of IDT electrode fingers connected to a second busbar, and reflectors having a plurality of reflector fingers. The pluralities of first and second IDT electrode fingers are alternatively connected to each busbar by either normal connections or reversed connections and include regions arranged by at least two different types of pitches. The normal connections are such that either the odd-numbered or even-numbered IDT electrode fingers connect to the first busbar, and the reversed connections are such that the opposite group of IDT electrode fingers connect to the first busbar.