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 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: Circuits, devices and methods are disclosed, including a phase shifter configured to provide a bypass state, a single first-handed quarter-wave state, a double first-handed quarter-wave state, or a single second-handed quarter-wave state utilizing two or less inductors. In some implementations, a phase shifter is disclosed to provide a first node and a second node, a first switchable path having a first inductance and a second inductance arranged in series between the first and second nodes, a capacitive grounding path implemented on each side of each of the first and second inductances, at least one of the capacitive grounding paths configured as a switchable capacitive grounding path, and a reconfiguring circuit assembly configured to allow the phase shifter to provide a plurality of quadrant phase shifts utilizing the first and second inductances and the at least one switchable capacitive grounding path.

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 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: 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: Circuits, devices and methods are disclosed, including a phase shifter configured to provide a bypass state, a single first-handed quarter-wave state, a double first-handed quarter-wave state, or a single second-handed quarter-wave state utilizing two or less inductors. In some implementations, a phase shifter is disclosed to provide a first node and a second node, a first switchable path having a first inductance and a second inductance arranged in series between the first and second nodes, a capacitive grounding path implemented on each side of each of the first and second inductances, at least one of the capacitive grounding paths configured as a switchable capacitive grounding path, and a reconfiguring circuit assembly configured to allow the phase shifter to provide a plurality of quadrant phase shifts utilizing the first and second inductances and the at least one switchable capacitive grounding path.

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.