A method for tuning an envelope tracking (ET) system includes: determining a setting combination from a plurality of setting available to the ET system, wherein determining the setting combination from the plurality of setting available to the ET system includes: determining, by a processing module, a first setting in a plurality of first settings included in the plurality of settings, and configuring the ET system by the first setting; and after the ET system is configured by the first setting, determining, by the processing module, a second setting in a plurality of second settings included in the plurality of settings, and configuring the ET system by the second setting. In addition, the setting combination includes the first setting and the second setting.

An electronic circuit includes a differential output circuit that produces a differential output signal at a differential output. A primary winding of a balun has a first balun terminal coupled to a first differential output terminal, and a second balun terminal coupled to a second differential output terminal. A configurable harmonic reduction circuit includes first and second configurable shunt capacitance circuits coupled between the first differential output terminal or the second differential output terminal, respectively, and a ground reference node. A control circuit receives tuning data associated with a calibrated tuning state. The tuning data indicates a first and second calibrated capacitance values, which are unequal, for the first and second configurable shunt capacitance circuits, respectively. The control circuit controls the first configurable shunt capacitance circuit to have the first calibrated capacitance value, and controls the second configurable shunt capacitance circuit to have the second calibrated capacitance value.

A wireless communication device includes an antenna array with multiple antenna elements, an array of power amplifiers, and an array of phase shifters. Each antenna element is coupled to a power amplifier and a phase shifter. The device also includes transmitter circuitry coupled to the antenna array to encode a constant amplitude signal, which includes a power amplifier enable code to indicate which power amplifiers are to run in a subsequent data sample and a beam direction code to control beam direction of each phase shifter of the array of phase shifters in the subsequent data sample. The constant amplitude signal is then provided to the array of antenna elements and amplitude and phase modulation is combined over an air interface into a composite modulated signal.

A controller having a wireless transmission interface is provided. The controller includes an amplifier, an analog-to-digital converter, a digital filter, a processor, and a radio frequency signal transceiver. The amplifier is coupled to the wireless transmission interface, and generates an amplification signal according to an input signal. The analog-to-digital converter is coupled to the amplifier, and configured to convert the amplification signal into a digital format. The digital filter is coupled to the analog-to-digital converter, and configured to filter the amplification signal in the digital format to generate a filtered signal. The processor is coupled to the digital filter, and configured to perform a calculation on the filtered signal to generate a calculation result. The radio frequency signal transceiver is coupled to the processor, and obtains received information according to the calculation result and the filtered signal.

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.

A radio frequency module includes a radio frequency filter (10), and the radio frequency filter (10) includes a terminal (11), a terminal (12), an impedance element (Z) disposed in series on a path (13) connecting the terminal (11) and the terminal (12), and a parallel arm resonator (P) connected between a node (N) on the path (13) and a ground. The impedance element (Z) is a capacitor or an inductor, and a wiring length A.sub.1 between the node (N) and the parallel arm resonator (P) is shorter than a wiring length B.sub.1 between the impedance element (Z) and a terminal (terminal (11), for example) out of the terminal (11) and the terminal (12) having a shorter wiring length to the impedance element (Z).

Radio frequency (RF) systems with tunable filters are provided herein. In certain embodiments, an RF system includes a first RF processing circuit configured to process a first frequency band of a first communication standard and a second frequency band of a second communication standard. The first frequency band and the second frequency band are close in frequency and/or partially overlapping in frequency. The first RF processing circuit includes a tunable filter for changing the bandwidth of the first RF processing circuit to enhance the robustness of the first RF processing circuit to blocker or jammer signals of a third frequency band.

Disclosed is receiver for a noise limited system. A front-end circuit amplifies and band-limits an incoming signal. The amplification increases the signal swing but introduces both thermal and flicker noise. A low-pass band limitation reduces the thermal noise component present at frequencies above what is necessary for correctly receiving the transmitted symbols. This band limited signal is provided to the integrator circuit. The output of the integrator is equalized to reduce the effects of inter-symbol interference and then sampled. The samples are used to apply low frequency equalization (i.e., in response to long and/or unbalanced strings of symbols) to mitigate the effects of DC wander caused by mismatches between the number of symbols of each kind being received.

Multi-mode power amplifier systems are described. In certain embodiments, a multi-mode power amplifier system shares a power amplifier chain for different communication modes, where the power amplifier chain has a split output matching network with a first power amplifier transistor and a second power amplifier transistor. A bias circuit biases the power amplifier such that the first power amplifier transistor and the second power amplifier transistor are on in a first mode, and the first power amplifier transistor is on and the second power amplifier transistor is off in a second mode.

Multi-mode power amplifier systems are described. In certain embodiments, a multi-mode power amplifier system shares a power amplifier chain for different communication modes. A power amplifier amplifies a radio frequency signal in at least a first mode and a second mode. An output matching network is coupled to an output of the power amplifier, and a bias circuit provides a reference current with a first reference current level to the power amplifier in the first mode and a second reference current level to the power amplifier in the second mode, the multi-mode power amplifier system configured to adjust a power amplifier signal path for the second mode relative to the first mode.