Abstract: Systems and methods for duplexer circuits having signal leakage cancellation are provided. In one aspect, a duplexer circuit includes a transmit path splitter configured to split a radio frequency transmit signal into a pair of radio frequency transmit signals, and a receive path splitter configured to combine a pair of radio frequency receive signals. The duplexer circuit also includes an antenna path splitter configured to combine a pair of radio frequency transmit signals and split a radio frequency receive signal into the pair of radio frequency receive signals, and first and second duplexers. The first duplexer is coupled to a first leg of each of the transmit path splitter, the receive path splitter, and the antenna path splitter, and the second duplexer is coupled to a second leg of each of the transmit path splitter, the receive path splitter, and the antenna path splitter.

Abstract: Systems and methods for diplexer circuits with leakage cancellation are provided. In one aspect, a diplexer circuit including first and second radio frequency transceiver terminals and a first antenna terminal, and first and second parallel communication paths extending between the first radio frequency transceiver terminal and the first antenna terminal, and third and fourth parallel communication paths extending between the second radio frequency transceiver terminal and the first antenna terminal. The circuit also includes a first phase shifter configured to apply a first phase shift to a first radio frequency transmit signal on the first communication path, a second phase shifter configured to apply a second phase shift to a second radio frequency on the second communication path, and a third phase shifter configured to apply a third phase shift to the first radio frequency transmit signal on the third communication path.

Abstract: Apparatus and methods for diplexing by antenna structure are provided. In certain embodiments, a mobile device includes a front end system and an antenna structure. The front end system includes a first signal conditioning circuit configured to condition a first radio frequency signal of a first frequency, and a second signal conditioning circuit configured to condition a second radio frequency signal of a second frequency that is lower than the first frequency. The antenna structure is configured to diplex the first radio frequency signal and the second radio frequency signal, and includes a first antenna configured to handle the first radio frequency signal and a second antenna electromagnetically coupled to the first antenna and configured to handle the second radio frequency signal.

Abstract: Systems and methods for duplexer circuits having signal cancellation paths are provided. In one aspect, a duplexer circuit includes a first transmit filter configured to receive a first radio frequency transmit signal from a power amplifier, and a first receive filter configured to receive the first radio frequency transmit signal from the first transmit filter. The circuit also includes a first low-noise amplifier configured to receive the first radio frequency transmit signal from the first receive filter and amplify the first radio frequency transmit signal and a cancellation path configured to receive a second radio frequency transmit signal from the power amplifier. The circuit further includes a phase shifter configured to apply a phase shift to one or both of the first and second radio frequency transmit signals, and a second low-noise amplifier configured to amplify the second radio frequency transmit signal.

Abstract: Apparatus and methods for radio frequency front-ends are provided. In certain configurations, a radio frequency front-end includes ultrahigh band (UHB) transmit and receive modules employed for both transmission and reception of UHB signals via at least two primary antennas and at least two diversity antennas, thereby supporting both 4×4 receive MIMO and 4×4 transmit MIMO with respect to one or more UHB frequency bands, such as Band 42, Band 43, and/or Band 48. The radio frequency front-end can operate with carrier aggregation using one or more UHB carrier frequencies to provide flexibility in widening bandwidth for uplink and/or downlink communications.

Abstract: Apparatus and methods for wirelessly communicating using antennas are disclosed. In certain embodiments, an antenna system includes a first radio frequency signal conditioning circuit configured to condition a first radio frequency signal of a first frequency, a plurality of second radio frequency signal conditioning circuits configured to condition a plurality of second radio frequency signals of a second frequency that is greater than the first frequency, a plurality of switches operable in a first mode and a second mode, and an antenna array of including a plurality of antenna elements interconnect by the plurality of switches. The antenna array is operable to handle the first radio frequency signal in the first mode, and to handle the plurality of second radio frequency signals in the second mode.

Abstract: Average power tracking (APT) systems with fast transient settling are disclosed. In certain embodiments, an APT system is used to provide a power amplifier supply voltage to a power amplifier that amplifies a radio frequency (RF) signal. The APT system controls the power amplifier supply voltage to track an average power of the RF signal, and generates a first regulated voltage based on a first average power tracking voltage level and a second regulated voltage based on a second average power tracking voltage level. The APT system includes a DC switch configured to receive the first regulated voltage and the second regulated voltage, and operable to change state to transition the power amplifier supply voltage from the first average power tracking voltage level to the second average power tracking voltage level.

Abstract: Average power tracking (APT) systems with fast transient settling are disclosed. In certain embodiments, an APT system is used to provide a power amplifier supply voltage to a power amplifier that amplifies a radio frequency (RF) signal. The APT system controls the power amplifier supply voltage to track an average power of the RF signal, and includes a DC-to-DC converter that is assisted by an error amplifier in transitioning from one power amplifier supply voltage level to another power amplifier supply voltage level. Thus, the combination of a DC-to-DC converter with a fast changing error amplifier can swing enough AC voltage with a low enough slew rate to be able to rapidly transition the power amplifier supply voltage from one APT voltage level to another APT voltage level.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker system includes a first power amplifier that amplifies a first radio frequency (RF) signal and receives power from a first supply voltage, a second power amplifier that amplifies a second RF signal and receives power from a second supply voltage, and an envelope tracker including a first modulator that generates a first output current based on an envelope of the first RF signal and a plurality of regulated voltages, a second modulator that generates a second output current based on an envelope of the second RF signal and the regulated voltages, a first combiner that combines a first DC voltage with the first output current to generate the first supply voltage, and a second combiner that combines a second DC voltage with the second output current to generate the second supply voltage.

Abstract: Apparatus and methods for modulation partition and transmission via multiple antennas for enhanced transmit power capability are provided herein. In certain embodiments, an RF communication system includes a transceiver that generates a first RF signal and a second RF signal corresponding to partitions of a modulated RF signal. For example, the first RF signal and the second RF signal can be associated with different RB allocations of one or more channels of a frequency band. The RF communication system further includes a first transmit chain that processes the first RF signal to generate a first RF output signal for transmission on a first antenna, and a second transmit chain that processes the second RF signal to generate a second RF output signal for transmission on a second antenna.

Abstract: Apparatus and the methods for stacked power amplifiers are provided. In certain embodiments, a mobile device includes a transceiver that generates a first radio frequency input signal and a second radio frequency input signal, and a front end system including a stacked power amplifier that receives power from a power high supply voltage and a power low supply voltage. The stacked power amplifier includes a first power amplifier that amplifies the first radio frequency input signal and a second power amplifier that amplifies the second radio frequency input signal. The first power amplifier and the second power amplifier are electrically connected in a stack between the power high supply voltage and the power low supply voltage and operate with a shared DC bias current.

Abstract: A switching circuit comprises a first filter, a second filter and a plurality of switches. The first filter is configured to filter a first frequency band, a second frequency band that is adjacent to the first frequency band and a gap band between the first frequency band and the second frequency band. The second filter is configured to filter the second frequency band. The plurality of switches is configured to route signals from an antenna through one of the first filter and second filter.

Abstract: Methods and systems for fast sounding reference symbol (SRS) antenna port switching for FDD. A mobile device can include a baseband processor and a front end including a transmit power amplifier, a first transmit path, and a second transmit path. The front end can be configurable in a first mode to transmit via the first transmit path within a transmit band of a frequency division duplex band. The front end can be further configurable in a second mode to transmit via the second transmit path within a receive band of the frequency division duplex band.

Abstract: Broadband feedforward power amplifiers are disclosed herein. In certain embodiments, a broadband feedforward power amplifier includes a power amplifier electrically connected between a radio frequency (RF) input and an RF output, and a feedforward compensation circuit including a first amplifier electrically connected in parallel with the power amplifier, a load impedance, and a second amplifier electrically connected between the radio frequency input and the load impedance. The feedforward compensation circuit generates a compensation signal based on sensing an output of the first amplifier and an output of the second amplifier, and provides the compensation signal to the radio frequency output to thereby compensate the power amplifier for non-linearity.

Abstract: 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.

Abstract: Cellular radios employing multiple power amplifiers for legacy communications are disclosed herein. In certain embodiments, a mobile phone includes a first antenna, a second antenna, and an RFFE including a first transmit path operable to transmit a first RF signal on the first antenna using a first communication standard in a first mode, and a second transmit path operable to transmit a second RF signal on the second antenna using the first communication standard in the first mode. Furthermore, in a second mode the RFFE is implemented to reuse the first transmit path and the second transmit path to synchronously transmit a third RF signal on the first antenna and the second antenna using a second communication standard.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker supplies power to a power amplifier that amplifies an RF signal. The envelope tracker includes a multi-level switching circuit that generates an output current based on an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a combiner that combines a DC voltage with the output current of the multi-level switching circuit to generate a power amplifier supply voltage for the power amplifier. Accordingly, the output current of the multi-level switching circuit and a DC voltage are combined to generate the power amplifier supply voltage. Implementing the envelope tracking system in this manner can provide enhanced efficiency and/or higher bandwidth relative to an envelope tracking system in which a multi-level switching circuit directly outputs a power amplifier supply voltage.

Abstract: Apparatus and methods for modulation partition and transmission via multiple antennas for enhanced transmit power capability are provided herein. In certain embodiments, an RF communication system includes a transceiver that generates a first RF signal and a second RF signal corresponding to partitions of a modulated RF signal. For example, the first RF signal and the second RF signal can be associated with different RB allocations of one or more channels of a frequency band. The RF communication system further includes a first transmit chain that processes the first RF signal to generate a first RF output signal for transmission on a first antenna, and a second transmit chain that processes the second RF signal to generate a second RF output signal for transmission on a second antenna.

Abstract: Radio frequency front end modules are provided. In one aspect, a front end system includes at least one power amplifier configured to amplify a transmit radio frequency signal, at least one low noise amplifier configured to receive a receive radio frequency signal, an output node coupled to an antenna. The front end system further includes at least one switch configured to selectively couple the output node to the at least one power amplifier during a transmit period and to the at least one low noise amplifier during a receive period, at least one transmit filter coupled between the power amplifier and the at least one switch, and at least one receive filter coupled between the low noise amplifier and the at least one switch.

Abstract: Radio frequency front end modules are provided. In one aspect, a front end system includes at least one power amplifier configured to amplify a transmit radio frequency signal, at least one low noise amplifier configured to receive a receive radio frequency signal, an output node coupled to an antenna. The front end system also includes a first switch configured to selectively couple the output node to the at least one power amplifier during a transmit period and to the at least one low noise amplifier during a receive period, at least one transmit filter coupled between the power amplifier and the at least one switch, and at least one receive filter coupled between the low noise amplifier and the at least one switch. The front end system further includes a transmit supplemental filter, a receive supplemental filter, and a second switch.