Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes an error amplifier that controls a voltage level of a power amplifier supply voltage of the power amplifier based on amplifying a difference between a reference signal and an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a multi-level switching circuit that generates an error amplifier supply voltage based on sensing a current of the error amplifier, and uses the error amplifier supply voltage to power the error amplifier.

Aspects of this disclosure relate to an acoustic wave resonator with transverse mode suppression. The acoustic wave resonator can include a piezoelectric layer, an interdigital transducer electrode, a temperature compensation layer, and a mass loading strip. The mass loading strip can be a conductive strip. The mass loading strip can overlap edge portions of fingers of the interdigital transducer electrode. A layer of the mass loading strip can have a density that is at least as high as a density of a material of the interdigital transducer electrode. The material of the interdigital transducer can impact acoustic properties of the acoustic wave resonator.

A system for adapting the voltage of a drain of a power stage includes at least two transmission paths T.sub.Xa, a transmission path comprising a resistive element (1.sub.n), a phase control module (2.sub.n), and a power stage (3.sub.n) at the output of which a radiating element (E.sub.n) is arranged, comprising at least: a device (5.sub.n) for determining the value of a reflected power P.sub.r, the value of an incident power P.sub.i in a power stage, and the ratio of the powers R, an analogue device (6.sub.n) configured so as to pulse width-modulate the difference signal, a switching cell (7.sub.n) receiving a low-power PWM signal and designed to generate a power signal PWM.sub.a that is transformed, by a low-pass filter (8.sub.n), into a bias signal for biasing the power stage in accordance with a predefined bias control law.

Systems and methods for improving output stability of an RFPA. The systems may obtain an initial radio frequency signal to be amplified by the RFPA. The systems may also generate a compensated radio frequency signal by performing, based on a preset compensation rule and a set of compensation parameters, a gain compensation operation for the initial radio frequency signal. The set of compensation parameters may include a supply voltage of the RFPA and a transistor junction temperature of the RFPA. The systems may further generate, by performing a non-linear correction operation on the compensated radio frequency signal, a corrected radio frequency signal, which is transmitted to the RFPA.

Loss in a low-pass filter is reduced. A radio-frequency module includes an antenna terminal, a power amplifier, a low-noise amplifier, and a low-pass filter. The low-pass filter is disposed on a transmit path between the antenna terminal and the power amplifier and on a receive path between the antenna terminal and the low-noise amplifier. The low-pass filter has multiple paths. Each of the paths forms a part of either one or both of the transmit path and the receive path. The paths include a first path and a second path. The second path has a smaller reactance than the first path.

A transmission/reception module includes a substrate including a transmission signal input terminal, a reception signal output terminal, and an antenna terminal, an antenna switch circuit provided on the substrate and configured to output a transmission signal input from the transmission signal input terminal to the antenna terminal and configured to output a reception signal input from the antenna terminal to the reception signal output terminal, and a first inductor included in an input/output filter circuit provided between the antenna switch circuit and the antenna terminal. The first inductor includes a conductor whose winding axis direction is orthogonal to the substrate.

A power amplifier circuit includes: an amplifier that amplifies an input signal; and a resonant circuit that is connected to an output terminal of the amplifier and that attenuates a harmonic wave of an amplified signal obtained by amplifying the input signal. The resonant circuit includes an inductor disposed between the amplifier and a ground, a capacitive element disposed between the amplifier and the ground and connected in series to the inductor, an inductor connected in parallel to the inductor, a switch connected in series to the inductor, and a switch that is connected in parallel to the switch and that is of an element size common to an element size of the switch.

Aspects of the disclosure include a power amplifier comprising an input to receive an input signal, an output to provide an amplified output signal, a balun coupled between the input and the output, at least one capacitor coupled to the balun, and a controllable load coupled to the at least one capacitor.

A power amplifier circuit includes an amplifier that amplifies an input signal RFin, a matching circuit that provides impedance matching between an output port of the amplifier and an output terminal, an input of the matching circuit being connected to the output port of the amplifier, an output of the matching circuit being connected to the output terminal, and a resonant circuit provided between ground and a signal path that connects the output port of the amplifier and the input of the matching circuit, the resonant circuit resonating at a resonant frequency greater than or equal to the frequency of a fourth harmonic wave of an amplified signal obtained by amplifying the input signal.

A radio frequency (RF) transmitter includes a radiating element, a chip and a phase shifting circuit. The radiating element is arranged to receive a plurality of electrical signals to produce an RF output signal. The chip includes an amplifier circuit. The amplifier circuit is configured to amplify an RF input signal to generate a plurality of amplified signals at a plurality of output terminals, respectively. The phase shifting circuit is located outside the chip, and coupled to the output terminals and the radiating element. The phase shifting circuit is arranged to phase shift the amplified signals, and accordingly generate the electrical signals fed to the radiating element. The phase shifting circuit and the radiating element are formed on a same substrate.