The present invention breaks up the frequency bands which can be filtered by a simple low-loss band-pass or low pass filter. The second harmonic frequency is reduced by use of a non-linear clipper element which controls the driving waveform symmetry and can reduce the harmonics by as much as 5-15db which makes the filter much simpler and allows the amplifier to remain wide-band. The output waveform from the amplifier is symmetrical or nearly symmetrical.

In one embodiment a transmitter is disclosed. The transmitter comprises an envelope tracking amplifier circuit comprising a power amplifier; a radiofrequency path configured to couple a radiofrequency component of an input signal to an input of the power amplifier; an envelope path configured to modulate a supply voltage of the power amplifier with an envelope signal, the envelope path comprising an envelope shaping module configured to shape an envelope of the input signal using an envelope shaping function to obtain the envelope signal; and a delay block configured to vary the relative timing alignment of the radiofrequency path and the envelope path; storage for an indication of the envelope shaping function to be used by the envelope shaping module; and a processor operable to, iteratively search for a value of a first parameter of a generic envelope shaping function, by applying a test signal to the envelope tracking amplifier circuit and controlling the delay block over a sweep of the relative timing alignments between the radiofrequency path and the envelope path; determining an average measure of distortion of output of the envelope tracking amplifier circuit for the sweep of relative timing alignments; comparing the average measure of distortion of output of the envelope tracking amplifier circuit with an average measure of distortion of the output of the envelope tracking amplifier circuit for a previous iteration; and selecting for the envelope shaping function the value of the first parameter from the previous iteration if the average measure of distortion of the output of the envelope tracking amplifier circuit for the previous iteration is lower than the average measure of distortion of the output of the envelope tracking amplifier circuit determined; and storing an indication of the envelope shaping function with the selected value for the first parameter in the storage.

Improvement in linearity is achieved at low costs in a power amplifier module employing an envelope tracking system. The power amplifier module includes a first power amplifier circuit that amplifies a radio frequency signal and that outputs a first amplified signal, a second power amplifier circuit that amplifies the first amplified signal on the basis of a source voltage varying depending on amplitude of the radio frequency signal and that outputs a second amplified signal, and a matching circuit that includes first and second capacitors connected in series between the first and second power amplifier circuit and an inductor connected between a node between the first and second capacitors and a ground and that decreases a gain of the first power amplifier circuit as the source voltage of the second power amplifier circuit increases.

An apparatus for controlling the gain and phase of an input signal input to a power amplifier comprises a gain control loop configured to control the gain of the input signal based on power levels of the input signal and an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, and a phase control loop configured to obtain an error signal related to a phase difference between a first signal derived from the input and a second signal derived from the amplified signal, and control the phase based on the error signal, to obtain a predetermined phase of the amplified signal. The phase control loop delays the first signal such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. The apparatus may be included in a satellite.

An amplifier may include control circuitry that may track a first input signal parameter and, in response, adjust a value of a second input parameter. Input parameter tracking and adjustment may facilitate control of output parameters for the amplifier. For example, an envelope-tracking amplifier may track input signal amplitude and adjust other input parameters in response. The adjustments may facilitate control of output parameters, such as gain or efficiency. The amplifier may further include calibration circuitry to determine adjustment responses to various tracked input parameters.

An envelope tracking system for controlling a power amplifier supply voltage includes envelope circuitry and a feed forward digital to analog converter (DAC) circuitry. The envelope circuitry is configured to generate a target envelope signal based on a selected power amplifier supply voltage. The feed forward DAC circuitry includes a voltage source circuitry and a selector circuitry. The voltage source circuitry is configured to generate a plurality of voltages. The selector circuitry is configured to select one of the plurality of voltages based at least on the target envelope signal. The feed forward DAC circuitry is configured to provide the selected voltage to a supply voltage input of a power amplifier that amplifies a radio frequency (RF) transmit signal.

A variable load power amplifier that improves the performance of a power amplifier that provides both envelope tracking (ET) and average power tracking (APT). The variable load power amplifier can include a plurality of amplifiers that are each selectively connectable into one of a plurality of parallel combinations, each of the plurality of parallel combinations characterized by a corresponding load line. The variable load power amplifier can also include a plurality of control elements arranged to selectively connect one or more of the plurality of amplifiers into one of the plurality of parallel combinations, each of the plurality of control elements having a respective input terminal provided to receive a respective control signal, each of the plurality of control elements responsive to the respective control signal.

A power source circuit includes a linear regulator including: an amplifier configured to amplify an envelope signal for representing an envelope of an input signal input into a power amplifier, and an output stage including transistors, configured to output power output to be supplied to the power amplifier in accordance with amplified output of the amplifier; a monitor circuit configured to monitor the envelope signal; and a switched-capacitor circuit configured to generate a power source voltage higher than a voltage of the power output based on a monitoring result of the monitor circuit, wherein the switched-capacitor circuit does not supply the power source voltage to the amplifier, but supplies the power source voltage to the output stage.

An apparatus of a transmitter and method are provided, the apparatus comprising a processor that calculates a supply voltage (SV) value (SVV) to provide as an SV for a power amplifier (PA) of the transmitter for transmissions during a transmission time slot (TS). When the SV<an envelope tracking (ET) threshold (ETT), then the processor configures the PA to transmit a signal in an average power tracking (APT) mode that maintains the SV at the SVV during the TS. When the SV?ETT, and an APT condition is met, then the processor configures the PA to transmit the signal in the APT mode. When the SV?ETT, and the APT condition is not met, then the processor transmits by an adjustment to the SVV to track an amplitude modulation envelope during the TS in an ET mode.

The power amplifier circuit includes a first amplifier that amplifies a first signal and outputs a second signal, a second amplifier that amplifies the second signal and outputs a third signal, a power supply terminal that receives supply of a power supply voltage that varies as a function of an amplitude of the first signal, a first power supply line that supplies the power supply voltage from the power supply terminal to the first amplifier, a second power supply line that supplies the power supply voltage from the power supply terminal to the second amplifier, and a first delay circuit provided in the second power supply line.