Abstract: Examples of the disclosure include an amplifier system comprising an amplifier having an input to receive an input signal, and an output to provide an amplified output signal, the amplifier having a power level indicative of at least one of the input signal power and the amplified output signal power, and a linearizer coupled to the amplifier and having a plurality of modes of operation including a fully disabled mode and a fully enabled mode, the linearizer being configured to determine the power level of the amplifier, select a mode of operation of the plurality of modes of operation based on the power level of the amplifier, determine one or more linearization parameters corresponding to the selected mode of operation, and control linearization of the amplified output signal based on the determined one or more linearization parameters.

Abstract: Apparatus and methods for front-end systems with directional couplers and a shared back switch are provided. In certain configurations, a method includes transmitting a first transmit signal from a first transmit port to an antenna port, generating a first coupled signal in response to the first transmit signal using a first directional coupler, providing the first coupled signal to a receive port by way of a first loopback selection switch and a shared back switch, transmitting a second transmit signal from a second transmit port to the antenna port, generating a second coupled signal in response to the second transmit signal using a second directional coupler, and providing the second coupled signal to the receive port by way of a second loopback selection switch and the shared back switch.

Abstract: Examples of the disclosure include an amplifier system comprising an amplifier having an input to receive an input signal, and an output to provide an amplified output signal, the amplifier having a power level indicative of at least one of the input signal power and the amplified output signal power, and a linearizer coupled to the amplifier and having a plurality of modes of operation including a fully disabled mode and a fully enabled mode, the linearizer being configured to determine the power level of the amplifier, select a mode of operation of the plurality of modes of operation based on the power level of the amplifier, determine one or more linearization parameters corresponding to the selected mode of operation, and control linearization of the amplified output signal based on the determined one or more linearization parameters.

Abstract: Apparatus and methods for front-end systems with directional couplers and a shared back switch are provided. In certain configurations, a method includes transmitting a first transmit signal from a first transmit port to an antenna port, generating a first coupled signal in response to the first transmit signal using a first directional coupler, providing the first coupled signal to a receive port by way of a first loopback selection switch and a shared back switch, transmitting a second transmit signal from a second transmit port to the antenna port, generating a second coupled signal in response to the second transmit signal using a second directional coupler, and providing the second coupled signal to the receive port by way of a second loopback selection switch and the shared back switch.

Abstract: Apparatus and methods for front-end systems with directional couplers and a shared back switch are provided. In certain configurations, a method includes transmitting a first transmit signal from a first transmit port to an antenna port, generating a first coupled signal in response to the first transmit signal using a first directional coupler, providing the first coupled signal to a receive port by way of a first loopback selection switch and a shared back switch, transmitting a second transmit signal from a second transmit port to the antenna port, generating a second coupled signal in response to the second transmit signal using a second directional coupler, and providing the second coupled signal to the receive port by way of a second loopback selection switch and the shared back switch.

Abstract: Circuits, devices and methods are disclosed, including radio-frequency circuitry comprising a polar modulator configured to invert a sampled transmitted signal into an inverted sampled transmitted signal, a signal combiner configured to combine the inverted sampled transmitted signal with a received signal and a control logic circuit coupled to the polar modulator, the control logic circuit configured to adjust one or more tuning parameters of the polar modulator for inverting the sampled transmitted signal.

Abstract: Circuits, devices and methods are disclosed, including a phase shifter comprising a first node and a second node, and a first transmission line element having an inductance and a variable capacitance on each side of the inductance, the variable capacitance configured to provide a plurality of capacitance values to yield corresponding phase shift values based on an increment having a magnitude that is less than 90 degrees. In some implementations, the phase shifter further comprises a second transmission line element in series with the first transmission line element, the second transmission line element having an inductance and a variable capacitance on each side of the inductance configured to extend an overall phase shift range provided by the phase shifter.

Abstract: A variable capacitor is disclosed, having a variable capacitance between a first node and a second node. The variable capacitor comprises a switch having a first terminal and a second terminal, the impedance between the first terminal and the second terminal being controllable via a control node. The variable capacitor further includes a first capacitor coupled between the first terminal and the first node, and a second capacitor coupled between the second terminal and the second node.

Abstract: Apparatus and methods for front-end systems with directional couplers and a shared back switch are provided. In certain configurations, a method includes transmitting a first transmit signal from a first transmit port to an antenna port, generating a first coupled signal in response to the first transmit signal using a first directional coupler, providing the first coupled signal to a receive port by way of a first loopback selection switch and a shared back switch, transmitting a second transmit signal from a second transmit port to the antenna port, generating a second coupled signal in response to the second transmit signal using a second directional coupler, and providing the second coupled signal to the receive port by way of a second loopback selection switch and the shared back switch.

Abstract: Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port, a receive port, an antenna switch configured to selectively provide a transmit signal from the transmit port to the antenna port, a low noise amplifier having an input electrically connected to the antenna port and an output electrically connected to the receive port, and a loopback circuit including a reactive loopback impedance and a back switch electrically connected in series between the antenna switch and the receive port. The reactive loopback impedance includes a plurality of capacitors in series with the back switch and operable to provide a portion of the transmit signal to the receive port when the back switch is activated.

Abstract: A power amplifier circuit includes a transistor having a first terminal that is configured to receive an input signal, a second terminal electrically coupled to ground, and a third terminal configured to transmit a combined amplified signal. The power amplifier circuit further includes a combining signal input path electrically coupled to the second terminal and configured to receive a combining signal and provide the combining signal to the second terminal of the transistor to generate, at least in part, the combined amplified signal.

Abstract: Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port, a receive port, an antenna switch configured to selectively provide a transmit signal from the transmit port to the antenna port, a low noise amplifier having an input electrically connected to the antenna port and an output electrically connected to the receive port, and a loopback circuit including a reactive loopback impedance and a back switch electrically connected in series between the antenna switch and the receive port. The reactive loopback impedance includes a plurality of capacitors in series with the back switch and operable to provide a portion of the transmit signal to the receive port when the back switch is activated.

Abstract: Apparatus and methods for front-end systems with multiple loopbacks and a shared back switch are provided. In certain configurations, a front-end system includes a first transmit path between a first transmit port and an antenna port, a second transmit path between a second transmit port and the antenna port, a first loopback path from the first transmit path to a receive port, and a second loopback path from the second transmit path to the receive port. The first and second loopback paths operate with a shared back switch to reduce area and/or complexity of the front-end system. Additionally, each loopback path includes a loopback selection switch that operates in combination with the back switch to select that particular loopback path.

Abstract: Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port operable to receive a transmit signal, a receive port, an antenna switch, a back switch, a transmit port DC blocking capacitor coupled between a first end of the antenna switch and the transmit port, an antenna port DC blocking capacitor coupled between a second end of the antenna switch and the antenna port, a receive port DC blocking capacitor coupled between a first end of the back switch and the receive port, and a reactive loopback impedance coupled between a second end of the back switch and the first end of the antenna switch. The reactive loopback impedance provides a portion of the transmit signal to the receive port when the back switch is activated.

Abstract: Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port operable to receive a transmit signal, a receive port, an antenna switch, a back switch, a transmit port DC blocking capacitor coupled between a first end of the antenna switch and the transmit port, an antenna port DC blocking capacitor coupled between a second end of the antenna switch and the antenna port, a receive port DC blocking capacitor coupled between a first end of the back switch and the receive port, and a reactive loopback impedance coupled between a second end of the back switch and the first end of the antenna switch. The reactive loopback impedance provides a portion of the transmit signal to the receive port when the back switch is activated.

Abstract: Circuits, devices and methods are disclosed, including radio-frequency circuitry comprising a polar modulator configured to invert a sampled transmitted signal into an inverted sampled transmitted signal, a signal combiner configured to combine the inverted sampled transmitted signal with a received signal and a control logic circuit coupled to the polar modulator, the control logic circuit configured to adjust one or more tuning parameters of the polar modulator for inverting the sampled transmitted signal.

Abstract: A power amplifier circuit includes a transistor having a first terminal that is configured to receive an input signal, a second terminal electrically coupled to ground, and a third terminal configured to transmit a combined amplified signal. The power amplifier circuit further includes a combining signal input path electrically coupled to the second terminal and configured to receive a combining signal and provide the combining signal to the second terminal of the transistor to generate, at least in part, the combined amplified signal.

Abstract: Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes a transmit port that receives a transmit signal, an antenna port, a receive port, and an antenna switch connected along a transmit path between the transmit port and the antenna port. The front-end system further includes a loopback circuit including a reactive loopback impedance and a back switch electrically connected in series in a loopback path between the transmit port and the receive port. The loopback circuit provides a portion of the transmit signal to the receive port when the back switch is activated. Using reactive loopback impedance in the loopback circuit reduces an insertion loss of the transmit path relative to a configuration using resistive loopback impedance.

Abstract: A radio-frequency module comprises a low-noise amplifier including a common source transistor having a gate node that receives a radio-frequency input signal and a drain node that transmits a combined radio-frequency output signal, and a correction signal input path configured to receive a correction signal and provide the correction signal to a source node of the common source transistor to generate, at least in part, the combined radio-frequency output signal.

Abstract: A variable capacitor is disclosed, having a variable capacitance between a first node and a second node. The variable capacitor comprises a switch having a first terminal and a second terminal, the impedance between the first terminal and the second terminal being controllable via a control node. The variable capacitor further includes a first capacitor coupled between the first terminal and the first node, and a second capacitor coupled between the second terminal and the second node.