A filter includes a series-arm resonator connected on a path connecting input/output terminals, and first and second parallel-arm resonators that are connected between the same node on the path and ground. A resonant frequency of the second parallel-arm resonator is higher than a resonant frequency of the first parallel-arm resonator, and an anti-resonant frequency of the second parallel-arm resonator is higher than an anti-resonant frequency of the first parallel-arm resonator. Each of the first and second parallel-arm resonators is defined by an acoustic wave resonator including an IDT electrode. The IDT electrode in the second parallel-arm resonator has a lower aspect ratio than the IDT electrode in the first parallel-arm resonator, where the aspect ratio is a ratio of an overlap width of electrode fingers to the number of pairs of electrode fingers.

An acoustic wave filter device includes a first band pass filter including a first acoustic wave resonator connected between an antenna terminal and a first signal terminal and having a first pass band, and a second band pass filter connected with the antenna terminal and having a second pass band on a higher side of the first pass band. The first acoustic wave resonator includes a substrate on a surface of which a piezoelectric thin film is provided, an IDT electrode provided on the substrate, and reflectors. At least a pitch of some electrode fingers is different from a pitch of other electrode fingers in at least one of the IDT electrode and the reflectors of the first acoustic wave resonator on a side closest to the antenna terminal.

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 microwave switched multiplexer having a bandpass At between frequencies f.sub.1 and f.sub.2, f=f.sub.1f.sub.2, the multiplexer comprising n signal channels, where n>1, each signal channel having a signal bandpass at a center frequency within M, the center frequencies of the signal channels being equally spaced apart by f/n; each signal channel comprising (a) a switch having first, second and third ports, the switch being adapted to be switched between a transmit position in Which the first port is connected to the second port, a receive position in which the first port is connected to the third port and an off position in which the first port is not connected to either second or third ports; (b) a common line extending from an antenna end to the first port, the common; line .Math. comprising an input resonator and a center resonator connected together in cascade, the center resonator being coupled between the resonator and the first port.

A flexible multi-path RF adaptive tuning network switch architecture that counteracts impedance mismatch conditions arising from various combinations of coupled RF band filters, particularly in a Carrier Aggregation-based (CA) radio system. In one version, a digitally-controlled tunable matching network is coupled to a multi-path RF switch in order to provide adaptive impedance matching for various combinations of RF band filters. Optionally, some or all RF band filters include an associated digitally-controlled filter pre-match network to further improve impedance matching. In a second version, some or all RF band filters coupled to a multi-path RF switch include a digitally-controlled phase matching network to provide necessary per-band impedance matching. Optionally, a digitally-controlled tunable matching network may be included on the common port of the multi-path RF switch to provide additional impedance matching capability. In a third version, CA direct mapped adaptive tuning networks include filter tuning blocks for selected lower frequency bands.

An analog to digital conversion circuit includes an analog to digital converter (ADC) circuit operable to convert an analog signal having an oscillation frequency into a first digital signal having a first data rate frequency, where the analog signal includes a set of pure tone components. The analog to digital conversion circuit further includes a digital decimation filtering circuit operable to convert the first digital signal into a second digital signal having a second data rate frequency. The analog to digital conversion circuit further includes a digital bandpass filter (BPF) circuit operable to convert the second digital signal into an outbound digital signal having a third data rate frequency, where the digital bandpass filter circuit is set to produce a bandpass region approximately centered at the oscillation frequency of the analog signal and having a bandwidth tuned for filtering a pure tone.

A filter circuit includes a pass band filter and a multipath interference mitigation leg. The pass band filter is disposed along a signal path between a provider-side port and a user-side port. The pass band filter is configured to pass a provider bandwidth signal received at the provider-side port and block at least a portion of a home network bandwidth signal received at the user-side port. A frequency spectrum of the home network bandwidth signal is distinct from, and higher than, a frequency spectrum of the provider bandwidth signal. The multipath interference mitigation leg is operatively branched to ground from the signal path. The multipath interference mitigation leg is configured to increase a return loss in the home network bandwidth signal.

A circuit includes a bandpass filter and a self-tracking circuit. The bandpass filter has a first input node configured to receive an input square wave signal and an output node configured to provide an output sine wave signal. The bandpass filter includes a first binary-weighted programmable resistor array. The self-tracking circuit includes a second input node coupled to the output node. The self-tracking circuit includes a counter, and the counter includes an output node coupled to the first binary weighted programmable resistor array.

A band-pass filter includes a main body, five resonators, a shield, and a partition. The main body is formed of a dielectric. The partition is formed of a conductor. The five resonators are configured so that capacitive coupling is established between every two of the resonators adjacent to each other in circuit configuration. Each of the five resonators includes a resonator conductor portion. A first stage resonator and a fifth stage resonator are magnetically coupled to each other although not adjacent to each other in circuit configuration. The partition extends to pass between the respective resonator conductor portions of the first stage resonator and the fifth stage resonator, and is electrically connected to the shield.

A power supply circuit according to an embodiment includes an driver, a control circuit, and a protection circuit. The driver includes a first transistor connected between a high-potential-side power supply and a node and a second transistor connected between a low-potential-side power supply and the node. The control circuit generates, according to an output voltage to a load connected to the node via a first low-pass filter circuit, first and second switching pulses for alternately switching the first and second transistors. The protection circuit outputs, when a voltage of the node via a second low-pass filter circuit exceeds a first reference voltage, an interruption signal for making at least the first transistor nonconductive.