A linear voltage regulator includes a pass transistor, an error amplifier, a buffer, a load capacitor and a pair of components coupled in series between the output node of the error amplifier and the regulated output voltage node. The buffer is coupled between the error amplifier and the pass transistor. The buffer is a unity voltage-gain buffer, has a wide bandwidth and provides higher current drive to the control terminal of the pass transistor. A first component of the pair of components is provided to decrease loop gain as output current increases so as to provide frequency compensation, but reduces a speed at which the regulator can respond to output voltage transients. A second component of the pair of components is designed to at least partially negate the operation of the first component during an output voltage transient, and thereby enables the regulator to respond quickly to the transient.

Aspects of this disclosure relate to acoustic wave devices on stacked die. A first die can include first acoustic wave device configured to generate a boundary acoustic wave. A second die can include a second acoustic wave device configured to generate a second boundary acoustic wave, in which the second die is stacked with the first die. The first acoustic wave resonator can include a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and high acoustic velocity layers on opposing sides of the piezoelectric layer. The high acoustic velocity layers can each have an acoustic velocity that is greater than a velocity of the boundary acoustic wave.

The described technology is generally directed towards a sensor signal multiplexer and digitizer with analog notch filter and optimized sample frequency, and corresponding methods of use and manufacture. In some examples, the disclosed technologies can be used to reduce vibration sensitivity of an inertial measurement unit (IMU). The disclosed sensor signal multiplexer can sample sensor inputs on multiple input channels at a first, higher frequency, and integrate samples for each channel in order to generate lower frequency sensor outputs. The lower frequency sensor outputs can be converted to digital form.

A filtering method and apparatus are provided, and the method includes: performing spectrum shifting on a first signal to obtain a second signal, where the first signal includes a first valid signal band and a first to-be-suppressed signal band, a demarcation point of the first valid signal band and the first to-be-suppressed signal band in the first signal is a first boundary point, the first boundary point corresponds to a second boundary point in the second signal, a frequency of the second boundary point is equal to a frequency of a first side frequency point of the filter, and a frequency range corresponding to the first valid signal band in the second signal falls within a frequency range corresponding to a passband of the filter (S301); and filtering the second signal by using the filter, to obtain the first valid signal band (S302).

A radio frequency module includes: a module board that includes a first principal surface and a second principal surface on opposite sides of the module board; a power amplifier; and a first circuit component. The power amplifier includes: a first amplifying circuit element; a second amplifying circuit element; and an output transformer that includes a primary coil and a secondary coil. An end of the primary coil is connected to an output terminal of the first amplifying circuit element. Another end of the primary coil is connected to an output terminal of the second amplifying circuit element. An end of the secondary coil is connected to an output terminal of the power amplifier. The first amplifying circuit element and the second amplifying circuit element are disposed on the first principal surface. The first circuit component is disposed on the second principal surface.

Carrier aggregation (CA) may cause interference between operation on two or more carriers within a user equipment (UE). This interference can degrade signal quality on one or more of the carriers involved in the carrier aggregation, which may be referred to as “desensing” one or more carriers. One or more isolating buffers may be coupled at a down-conversion mixer at a point where the down-conversion mixer receives a signal from a transmission line for isolating the transmission line from other transmission lines. The isolating buffer may reduce the effect of interference between multiple transmission lines carrying different carriers during carrier aggregation (CA) operation. The isolating buffers may be used in an RF transceiver supporting both 5G sub-7 GHz and 5G mmWave wireless networks and carrier aggregation across sub-7 GHz and mmWave bands.

Examples of the disclosure relate to a carrier aggregation circuit including a first path, a second path, and a switch assembly. The first path has a first filter configured to provide a matched impedance in a first frequency band. The second path has an adjustable matching network and a terminal for coupling to an external filter configured to provide a matched impedance in the second frequency band. The switch assembly is configured to adjust the adjustable matching network to provide a mismatched impedance in the first frequency band. Related methods for carrier aggregation, radio-frequency modules, and wireless devices are also provided.

A multiplexer includes filters and low pass filters. A second frequency band and a third frequency band are partially different. A first frequency band does not overlap the second frequency band and the third frequency band. One end of the filter is connected to a common terminal and the other end is connected to an input/output terminal. The low pass filter is connected in one end to the common terminal and in the other end to one end of the filter. The other end of the filter is connected to one end of the low pass filter. The other end of the low pass filter is connected to the input/output terminal. One end of the filter is connected to a node between the other end of the low pass filter and one end of the filter and the other end of the filter is connected to the input/output terminal.

A radio chain arrangement comprising at least two levels of radio chain entities. Each of the levels of radio chain entities is associated with a respective frequency range encompassing at least one radio frequency band each. At least two radio chain entities of a lower level of radio chains are comprised in a radio chain entity of a next higher level. Each radio chain entity of the at least two levels of radio chain entities comprises a respective radio transceiver arrangement that is connected to at least a respective one of a number of antenna multiplexers. For all radio chain entities except a lowest level, the respective radio transceiver arrangement is connected to the antenna multiplexers via a splitter arrangement. An active antenna system comprising such radio chain arrangements and a method for its operation is also disclosed.

An elastic wave device includes an LiNbO.sub.3 substrate, a first elastic wave resonator including a first IDT electrode and a first dielectric film, and a second elastic wave resonator including a second IDT electrode and a second dielectric film. A Rayleigh wave travels along at least one surface of the elastic wave device. A thickness of the first dielectric film differs from a thickness of the second dielectric film. A propagation direction of an elastic wave in the first elastic wave resonator coincides with a propagation direction of an elastic wave in the second elastic wave resonator. Euler angles of the LiNbO.sub.3 substrate fall within a range of (0°±5°, θ, 0°±10°).