A receiver includes a low noise amplifier (LNA) configured to amplify an input RF signal using a first current supplied by a first current source, and a voltage controlled oscillator (VCO) for applying an oscillation frequency to the amplified signal by generating an oscillation signal using the first current.

There is disclosed an envelope tracking power supply arranged to generate a modulated supply voltage in dependence on a reference signal, comprising a first path for tracking low frequency variations in the reference signal and a second path for tracking high frequency variations in the reference signal, the second path including a linear amplifier, wherein the output of the linear amplifier comprises a current source and a current sink connected to the high frequency output, there further being provided a DC offset current at the high frequency output.

The present disclosure relates to envelope tracking with reduced circuit area and power consumption. In one embodiment, an envelope power converter includes a switching power converter configured to receive a supply voltage and provide an output based on a switching control signal. A holding inductor is coupled between the switching power converter and envelope power supply output node. An offset capacitor is coupled between the envelope power supply output node and control node. In response to a target envelope power supply output voltage, a control circuit is configured to generate the switching control signal and a control voltage to maintain envelope power supply signal at target voltage level. The control circuit is configured to generate switching control signal and control voltage such that supply voltage is provided by switching power converter to holding inductor and offset capacitor is charged to target level without changing voltage of envelope power supply signal.

A push-pull driver according to an example includes a push stage coupled via a first coupling capacitor to an output of the push-pull driver and a pull stage coupled via a second coupling capacitor to the output of the push-pull driver. Using an example may allow to improve a trade-off between saving energy, an overall complexity of a corresponding implementation, a robust and reliable operation and other parameters and design goals.

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.

The output of a Radio Frequency (RF) Power Amplifier (PA) is sampled and down-converted, and the amplitude envelope of the baseband feedback signal is extracted. This is compared to the envelope of a transmission signal, and the envelope tracking modulation of the RF PA supply voltage is adaptively pre-distorted to achieve a constant ISO-Gain (and phase) in the RF PA. In particular, a nonlinear function is interpolated from a finite number gain values calculated from the feedback and transmission signals. This nonlinear function is then used to pre-distort the transmission signal envelope, resulting in a constant gain at the RF PA over a wide range of supply voltage values. Since the gains are calculated from a feedback signal, the pre-distortion may be recalculated at event triggers, such as an RF frequency change.

An envelope tracking power supply arranged to generate a modulated supply voltage in dependence on a reference signal, comprising a first path for tracking low frequency variations in the reference signal and a second path for tracking high frequency variations in the reference signal, and further comprising a combiner having a low frequency combining element for the first path and a high frequency combining element for the second path, and for generating the modulated supply voltage, wherein there is further provided sensing circuitry for sensing a resonance signal in the low or high frequency combining element, and adjusting circuitry for adjusting a signal in the first path in dependence on the sensed resonance signal.

There is disclosed an envelope tracking modulated supply arranged to generate a modulated supply voltage in dependence on a reference signal, comprising a low frequency path for tracking low frequency variations in the reference signal and including a switched mode power supply, a correction path for tracking high frequency variations in the reference signal and including a linear amplifier, a feedback path from the output of the linear amplifier to the input of the linear amplifier, and a combiner for combining the output of the switched mode power supply and the output of the linear amplifier to generate a modulated supply voltage.

This application relates to Class D amplifier circuits (200). A modulator (201) controls a Class D output stage (202) based on a modulator input signal (Dm) to generate an output signal (Vout) which is representative of an input signal (Din). An error block (205), which may comprise an ADC (207), generates an error signal () from the output signal and the input signal. In various embodiments the extent to which the error signal () contributes to the modulator input signal (Dm) is variable based on an indication of the amplitude of the input signal (Din). The error signal may be received at a first input (204) of a signal selector block (203). The input signal may be received at a second input (206) of the signal selector block (203). The signal selector block may be operable in first and second modes of operation, wherein in the first mode the modulator input signal is based at least in part on the error signal; and in the second mode the modulator input signal is based on the digital input signal and is independent of the error signal. The error signal can be used to reduce distortion at high signal levels but is not used at low signal levels and so the noise floor at low signal levels does not depend on the component of the error block (205).

An RF PA is designed to operate efficiently for average powers when biased at the system supply voltage, and uses an envelope tracking power supply to boost the bias voltage to maintain good efficiency at higher powers. As a result, for a majority of the time when transmitting average power signals, the RF PA bias voltage is the system-wide supply voltage (e.g. 3.4V in cell phones), which eliminates the need for stepping down voltages. The bias voltage is boosted during the less frequent times when higher power is needed. As a result, only a boost type of DC voltage converter is needed. The efficiency of the RF PA is therefore increased because voltage conversion is required less frequently and only when higher power RF signals are transmitted.