A pre-distorter that both accurately compensates for the non-linearities of a radio frequency transmit chain, and that imposes as few computation requirements in terms of arithmetic operations, uses a diverse set of real-valued signals that are derived from the input signal. The derived real signals are passed through configurable non-linear transformations, which may be adapted during operation, and which may be efficiently implemented using lookup tables. The outputs of the non-linear transformations serve as gain terms for a set of complex signals, which are functions of the input, and which are summed to compute the pre-distorted signal. A small set of the complex signals and derived real signals may be selected for a particular system to match the classes of non-linearities exhibited by the system, thereby providing further computational savings, and reducing complexity of adapting the pre-distortion through adapting of the non-linear transformations.

An envelope tracking (ET) bias circuit includes an envelope tracking (ET) bias circuit includes an envelope detection circuit, an envelope amplifier circuit, and an envelope output circuit. The envelope detection circuit is configured to detect an envelope of an input signal, and output an envelope signal based on the detected envelope of the input signal. The envelope amplifier circuit is configured to differentially amplify the envelope signal in response to a first control signal and cancel a direct current (DC) offset of the envelope signal to output an amplified signal from which the DC offset is canceled. The envelope output circuit is configured to generate an ET bias current by selecting either one of a negative signal of the amplified signal and a positive signal of the amplified signal in response to a second control signal.

A source follower with an input node and an output node includes a first transistor, a second transistor, and a DC (Direct Current) tracking circuit. The first transistor has a control terminal, a first terminal coupled to a first node, and a second terminal coupled to a second node. The second transistor has a control terminal, a first terminal coupled to a ground voltage, and a second terminal coupled to the first node. The DC tracking circuit sets the second DC voltage at the second node to a specific level. The specific level is determined according to the first DC voltage at the first node. The output node of the source follower is coupled to the first node.

Disclosed herein are front-end modules that support carrier aggregation. Wireless communication configurations are disclosed that include a plurality of such front-end modules to support uplink and/or downlink carrier aggregation. Individual front end modules include a power amplifier module to amplify signals received at a transceiver port and an envelope tracker to increase efficiency of the power amplifier module. The front-end modules include a multiplexer and an antenna switch module with a plurality of duplexers between them along a corresponding plurality of paths. One path includes a first duplexer configured to process frequency division duplex (FDD) signals and another path includes a second duplexer configured to process time division duplex (TDD) signals. The front-end modules also include a low noise amplifier module coupled to the second duplexer to amplify TDD signals while received FDD signals are directed off module for amplification.

An envelope tracking (ET) current bias circuit includes a rectifying circuit, a phase compensation circuit, and a voltage/current conversion circuit. The rectifying circuit is configured to detect an envelope voltage from a radio frequency (RF) signal. The phase compensation circuit is configured to compensate for a phase of the envelope voltage in which the phase thereof is delayed in the rectifying circuit to output a phase compensated enveloped voltage. The voltage/current conversion circuit is configured to convert the phase compensated envelope voltage into an ET bias current.

A multimode voltage tracker circuit is provided. The multimode voltage tracker circuit is configured to generate a modulated voltage for amplifying a radio frequency (RF) signal(s), which may be modulated in a wide range of modulation bandwidth. In one non-limiting example, the multimode voltage tracker circuit can be configured to operate in a low modulation bandwidth (LMB) mode to generate an average power tracking (APT) modulated voltage for amplifying the RF signal(s) when the RF signal(s) is modulated in a lower modulation bandwidth (e.g., <50 KHz). As such, the multimode voltage tracker circuit can be adapted to support lower bandwidth communications in an Internet-of-Things (IoT) network with improved efficiency, stability, and performance.

Embodiments of the present invention provide a power amplifier, a radio remote unit RRU, and a base station. A multiphase pulse width modulator performs modulation to generate N multiphase pulse-width modulation PWM signals. The multiphase pulse-width modulation PWMn signal may be amplified. The multiphase pulse-width modulation PWMn signal may be filtered and a combination may be performed at a drain or a collector of a power amplifier transistor. According to the new radio frequency amplifier in accordance with the disclosure, envelope feeding loop inductance can be effectively reduced, so that video bandwidth is increased and DPD correction performance is improved.

Embodiments described herein relate to an envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, or envelope tracking signal for brevity. In certain embodiments, the envelope tracking system can estimate or measure the amplitude of the baseband signal. The envelope tracking system can further estimate the amplitude of the envelope of the RF signal. The system can convert the amplitude of the envelope signal to a single-bit digital signal, typically at a higher, oversample rate. The single-bit digital signal can be transmitted in, for example, a low-voltage differential signaling (LVDS) format, from a transceiver to an envelope tracker. An analog-to-digital converter (ADC or A/D) can convert the single-bit digital signal back to an analog envelope signal. Moreover, a driver can increase the power of the A/D output envelope signal to produce an envelope-tracking supply voltage for a power amplifier.

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.

Envelope tracking power supply circuitry includes a look up table (LUT) configured to provide a target supply voltage based on a power envelope measurement. The target supply voltage is dynamically adjusted based on a delay between the power envelope of an RF signal and a provided envelope tracking supply voltage. The envelope tracking supply voltage is generated from the adjusted target supply voltage in order to synchronize the envelope tracking supply voltage with the power envelope of the RF signal.