A power supply circuit in a wireless communications system includes an envelope tracking modulator coupled to a first power amplifier circuit and a second power amplifier circuit, so that the power supply circuit supplies power to the first power amplifier circuit and the second power amplifier circuit. When a transmit signal output by a processor is within a first bandwidth range, the power supply circuit supplies power to the first power amplifier circuit, and the first power amplifier circuit amplifies power of the transmit signal. When the transmit signal output by the processor meets a second bandwidth range, the power supply circuit supplies power to the second power amplifier circuit, and the second power amplifier circuit amplifies the transmit signal.

A power supply circuit in a wireless communications system includes an envelope tracking modulator coupled to a first power amplifier circuit and a second power amplifier circuit, so that the power supply circuit supplies power to the first power amplifier circuit and the second power amplifier circuit. When a transmit signal output by a processor is within a first bandwidth range, the power supply circuit supplies power to the first power amplifier circuit, and the first power amplifier circuit amplifies power of the transmit signal. When the transmit signal output by the processor meets a second bandwidth range, the power supply circuit supplies power to the second power amplifier circuit, and the second power amplifier circuit amplifies the transmit signal.

A transceiver is configured for a calibration mode of operation in which an impedance of a transmit chain is tuned responsive to a power measurement of a mixed RF calibration signal to form a tuned transmit chain. A direct conversion mixes an RF calibration signal with a DC offset signal to form the mixed calibration signal. During a normal mode of operation, a heterodyne mixer mixes an LO signal with an IF signal to produce an RF signal that is amplified through the tuned transmit chain.

A transceiver is configured for a calibration mode of operation in which an impedance of a transmit chain is tuned responsive to a power measurement of a mixed RF calibration signal to form a tuned transmit chain. A direct conversion mixes an RF calibration signal with a DC offset signal to form the mixed calibration signal. During a normal mode of operation, a heterodyne mixer mixes an LO signal with an IF signal to produce an RF signal that is amplified through the tuned transmit chain.

An apparatus is disclosed for analog-to-digital conversion. In an example aspect, the apparatus includes an analog-to-digital converter (ADC). The ADC includes a reference-crossing detector having an input and an output. The ADC also includes a ramp generator coupled between the output of the reference-crossing detector and the input of the reference-crossing detector. The ADC further includes a voltage shifter coupled between the output of the reference-crossing detector and the input of the reference-crossing detector.

A mobile terminal includes a housing having a front side, a rear side, and lateral sides, and including a metal rim formed of a metal material and at least one bending portion formed of a non-metal material. The mobile terminal includes a rear cover disposed on the rear side of the housing, a reflection sheet disposed on the cover and formed of a metal material, and an antenna module disposed between the rear cover and a front cover of the housing and configured to radiate a beamforming wireless signal, wherein a bending portion of the cover and a flat portion of the cover are configured to include a first region, a second region, and a third region, and a beamforming wireless signal of the first region may be reflected at the second region and the third region by the reflection sheet.

A mobile terminal includes a housing having a front side, a rear side, and lateral sides, and including a metal rim formed of a metal material and at least one bending portion formed of a non-metal material. The mobile terminal includes a rear cover disposed on the rear side of the housing, a reflection sheet disposed on the cover and formed of a metal material, and an antenna module disposed between the rear cover and a front cover of the housing and configured to radiate a beamforming wireless signal, wherein a bending portion of the cover and a flat portion of the cover are configured to include a first region, a second region, and a third region, and a beamforming wireless signal of the first region may be reflected at the second region and the third region by the reflection sheet.

A wireless multi-band device comprises a radiating system comprising a ground plane layer, a boosting element, and a radiofrequency system, wherein the radiofrequency system comprises a tunable reactive element.

A wireless multi-band device comprises a radiating system comprising a ground plane layer, a boosting element, and a radiofrequency system, wherein the radiofrequency system comprises a tunable reactive element.

Described herein are methods for amplifying radio-frequency signals using a variable-gain amplifier with a plurality of input nodes. The methods provide a plurality of gain modes with a low gain mode or bypass mode that follows a bypass path through the variable-gain amplifier and a plurality of higher gain modes that take advantage of tailored impedances for particular gain modes. The tailored impedances can be configured to improve linearity of the amplification process in targeted gain modes. The methods can selectively couple the bypass path to a reference potential node in the plurality of higher gain modes and can selectively decouple the input nodes from a degeneration switching block in the bypass mode.