428 results about "Envelope Tracking" patented technology

A novel apparatus and method of improving the power efficiency of a digital transmitter for non-constant-amplitude modulation schemes. The power efficiency improvement mechanism of the invention leverages the high efficiency of a switched-mode power supply (SMPS) that supplies the high DC current to the transmitter's power amplifier, while compensating for its limitations using predistortion. The predistortion may be achieved using any suitable technique such as digital signal processing, hardware techniques, etc. A switched mode power supply (i.e. switching regulator) is used to provide a slow form (i.e. reduced bandwidth) of envelope tracking (based on a narrower bandwidth distorted version of the envelope waveform) such that the switching regulator can use a lower switching rate corresponding to the lower bandwidth, thereby obtaining high efficiency in the switching regulator. The resulting AM-AM and AM-PM distortions in the power amplifier are compensated through predistortion of the digital amplitude modulating signal which dictates the envelope at the PA input. Similarly, the phase modulation is also compensated prior to the PA, such that once it undergoes the distortion in the PA, the end result is sufficiently close to the desired phase.

An amplifier system is provided that switches between a linear mode of operation, an envelope tracking mode of operation and a polar mode of operation. The amplifier system switches between modes of operation based upon a characteristic of an input signal relative to a first threshold level and a second threshold level. A mode selector selects the operation mode by transmitting an amplitude modulated signal plus a variable headroom voltage to a supply terminal of a power amplifier during the envelope tracking mode, an amplitude modulated signal to the supply terminal and phase modulated input signal during the polar mode and a substantially constant amplitude signal to the supply terminal during the linear mode.

Envelope tracking (ET) methods and systems for controlling the delivery of power to radio frequency power amplifiers (RFPAs). An exemplary ET system includes an RFPA and a wide bandwidth capable and power efficient envelope modulator that includes a first power supplying apparatus and a second power supplying apparatus. The first power supplying apparatus includes a switch-mode converter and a regulator. The first mode converter is operable to dynamically step down a fixed power supply voltage according to amplitude variations in an envelope signal received by the regulator, and use the resulting dynamic power supply signal to power the regulator. The second power supplying apparatus is connected in parallel with the first power supplying apparatus. Depending on a power of an output signal to be generated at an output of the power amplifier, power is supplied to the power amplifier from either or both of the first and second power supplying apparatuses.

A method for providing power management in a radio frequency power amplifier using adaptive envelope tracking is provided that includes receiving an input voltage. A power control signal is received. A feedback signal is received. An amplifier input signal is received. From the input voltage, a regulated power supply signal is generated based on the power control signal, the feedback signal, and the amplifier input signal.

High-efficiency envelope tracking (ET) methods and apparatus for dynamically controlling power supplied to radio frequency power amplifiers (RFPAs). An exemplary ET circuit includes a switch-mode converter coupled in parallel with a split-path linear regulator. The switch-mode converter is configured to generally track an input envelope signal Venv and supply the current needs of a load (e.g., an RFPA). The split-path linear regulator compensates for inaccurate envelope tracking by sourcing or sinking current to the load via a main current path. A current sense path connected in parallel with the main current path includes a current sense resistor used by a hysteresis comparator to control the switching of the switch-mode converter. The split-path linear regulator is configured so that current flowing in the current sense path is a lower, scaled version of the current flowing in the main current path.

Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can be an envelope tracking amplifier. Circuital arrangements to generate reference gate-to-source voltages for biasing of the gates of the transistors of the stack are also presented. Particular biasing for a case of an input transistor of the stack is also presented.

An amplifier system is provided that switches between a linear mode of operation, an envelope tracking mode of operation and a polar mode of operation. The amplifier system switches between modes of operation based upon a characteristic of an input signal relative to a first threshold level and a second threshold level. A mode selector selects the operation mode by transmitting an amplitude modulated signal plus a variable headroom voltage to a supply terminal of a power amplifier during the envelope tracking mode, an amplitude modulated signal to the supply terminal and phase modulated input signal during the polar mode and a substantially constant amplitude signal to the supply terminal during the linear mode.

Various envelope tracking amplifiers are presented that can be switched between an ET (envelope tracking) mode and a non-ET mode. Switches and / or tunable components are utilized in constructing the envelope tracking amplifiers that can be switched between the ET mode and the non-ET mode.

Switched-mode power supplies (SMPSs) and their control methods for radio frequency (RF) power amplifiers in battery-powered wireless transmitter devices involve a Boost-type SMPS and a Buck-type SMPS in cascade connection which are controlled so that high efficiency is maintained for various loads and transmission power levels. The Boost SMPS and the Buck SMPS can be controlled based on the mode of operation of the transmitter, such as the actual battery voltage, the needed output power, the selected frequency band, the selected RF power amplifier (PA), the selected modulation method of the transmission signal, and / or the selected PA voltage control method, such as the envelope elimination and restoration (EER) technique, the envelope tracking (ET) technique, or the power-level tracking (PT) technique.

An apparatus and a method for Envelope Tracking (ET) power amplification in a wireless communication system are provided. The apparatus includes a baseband signal controller for outputting an envelope signal in an envelope signal path and outputting a constant signal in a baseband signal path when measuring a time delay of the envelope signal path, and for outputting a constant signal in the envelope signal path and outputting a baseband signal in the baseband signal path when measuring a time delay of the baseband signal path, a time delay difference measurer for measuring a time delay of each path by calculating a correlation coefficient between the envelope signal path and the baseband signal path and a signal time controller for setting a time delay in a corresponding path using the time delay difference of each path and aligning times.

A transceiver comprises an amplifying circuit for amplifying an input signal to produce an output signal. A power supply is operable for varying the level of power supplied to the amplifying circuit in response to variation of an input signal envelope directed to the power supply. A processing circuit is operable for digitally detecting the input signal envelope to provide variation of the power supply level. The processing circuit is further operable for digitally delaying the digital input signal envelope to time align the power supply level with the input signal.

An envelope tracking radio frequency (RF) power amplifier having an adaptive envelope signal processing circuit is disclosed. An RF input voltage is sampled by the adaptive envelope signal processing circuit which provides control signals to the power supply which supplies voltages to RF power devices in order to simultaneously satisfy two operating conditions: a) provide best possible efficiency of the power amplifier stages depending on the input signal characteristics and b) provide compensation for RF transistor AM-AM and AM-PM distortion compensation across the power range. In particular, the voltage control provides for constant power amplifier gain across the input signal dynamic range, thus minimizing power amplifier amplitude distortions and extending the useful power amplifier linear dynamic range up to saturation point. The power amplifier thus exhibits better linearity and efficiency than offered by conventional techniques and topologies.

An apparatus and method for amplifying a Transmit (Tx) signal according to an Envelope Tacking (ET) scheme in a wireless communication system are provided. A transmitting end apparatus includes an envelope gain controller for controlling a gain of a digital baseband Tx signal in accordance with power control, a detector for detecting an envelope signal from the digital baseband Tx signal whose gain is controlled, and for shaping on the envelope signal, a first Digital to Analog Converter (DAC) for converting the shaped envelope signal into an analog signal, and an envelope modulator for generating a drain bias of a power amplifier that amplifies a Radio Frequency (RF) Tx signal by using the analog envelope signal. Accordingly, a digital-based ET scheme is implemented, and by using a plurality of shaping tables, efficiency of the ET scheme can be maximized in a transmitting end that uses power control.

Control systems and methods for power amplifiers operating in envelope tracking mode are presented. A set of corresponding functions and modules are described and various possible system configurations using such functions and modules are presented.

There is disclosed a method of controlling an input to an envelope modulated power supply of an envelope tracking amplification stage, comprising: generating an envelope signal representing the envelope of a signal to be amplified; applying a shaping function to the envelope signal to generate a shaped envelope signal, including: clipping the shaped envelope signal at high input envelope values; and providing the shaped envelope signal as an input signal to the envelope modulated power supply.

A transmitter (70) generates a time-varying, detroughed, biasing signal (154) for an RF power amplifier (10) so that the RF power amplifier (10) is biased in accordance with an envelope tracking scheme. A trough-filling section (94) is responsive to an envelope tracking signal (86), which in turn is responsive to a magnitude signal (90) extracted from a complex baseband communication signal (76). The trough-filing section (94) includes a limiting stage (108) that forms a raw troughing signal (110) which expands the bandwidth of the envelope tracking signal (86). A filtering stage (116) reduces the bandwidth of the raw troughing signal (110) to form a trough-filling signal (122) that is combined back into the envelope tracking signal (86) using a linear process that maintains the bandwidth of the envelope tracking signal (86).

An envelope tracking power amplifier system time-aligns a supply voltage to an input signal to a power amplifier. The power supply operates in a static mode for low amplitude input signals and operates in a dynamic mode for high amplitude input signals. In the static mode, the power supply produces a substantially constant supply voltage independent of the amplitude of the input signal. In the dynamic mode the power supply produces a dynamically varying envelope tracking supply voltage based on the amplitude of the input signal. A first delay is determined based on portions of the input and output signals captured during static operation of the power supply and a second delay is determined based on portions of the input and output signals captured during dynamic operation. A delay mismatch is estimated based on a difference between the first and second delays.

A communication unit includes a radio frequency, RF, transmitter having: a power amplifier, PA, module; and an envelope tracking system operably coupled to the PA module and having a supply modulator arranged to variably control a supply voltage for the PA module in response to a number of input samples of an envelope signal; wherein the envelope tracking system further includes at least one slew rate module arranged to re-distribute a maximum slew rate across the number of input samples in a provision of a variable power supply to the PA module.

A Switch Node Assisted Linear architecture, including a linear amplifier in parallel with a switched converter, is configurable in two tracking modes: (a) a SMAL regulator in which the amplifier sets toad voltage with an envelope tracking bandwidth, and the switched converter is configured for current assist, and (b) a Switched Mode Power Supply configuration in which the amplifier is switch-decoupled, and the switcher circuit is switched configured with an output capacitor, operable as an SMPS providing load voltage with an adaptive tracking bandwidth that is less than the envelope tracking bandwidth. Staged switching effects substantially seamless transitions between tracking modes, with the amplifier holding the load voltage at a substantially constant envelope tracking voltage (CVET): (a) for ET-AT transitions, the CVET mode enables pre-charging the output capacitor to a target AT voltage, prior to switch-decoupling the amplifier; and (b) for AT-ET transitions, CVET mode enables discharging the output capacitor.

An envelope tracking power supply has a multiple-output DC / DC converter, a switch bank, an output voltage selector and an output filter. The DC / DC converter has an alternating current generating portion and a full rectifying portion. The alternating current generating portion, typically a LC circuit, can receive an input voltage and operate at zero voltage switching. The full rectifying portion includes at least one secondary winding and one voltage doubler output. Each voltage doubler has a first transistor, a second transistor, a first capacitor and a second capacitor. The transistors used as rectifier devices allow currents to flow bi-directionally and sink and source the currents from and to output capacitors to keep their voltage balance. Secondary windings and output capacitors are connected in series respectively. A switch bank selects a desired voltage from the series connected capacitors and connects it to the output filter. The switch bank receives an envelope tracking command from the voltage selector and provides a step voltage to the output. The output voltage is changed at switching speed to track a high bandwidth envelope signal.

A multi-mode radio transmitter for use in mobile radio cellular standards, such as 2G, 2.5G and 3G, and a method of operating the transmitter in which an input signal is modulated independently of controlling the drive of a power amplifier (PA) module (40). The transmitter comprises circuitry (12, 60) for extracting the phase (θ) and amplitude (R) components from envelope information in the input signal. A modulator (110) uses the phase component (θ) to produce a constant-envelope signal comprising a phase modulated real signal at the transmitter frequency. This signal is multiplied in a multiplier (72) with either a fixed bias voltage (Vg1) to produce a constant envelope signal or a low level envelope tracking signal derived from an amplitude component (R) by a first amplitude control circuit (78) to produce a signal modulated exactly by the amplitude component. An output from the multiplier is applied to the PA module (40) having a control input (41). The PA module is controllable in a plurality of manners dependent on the characteristics and the required output power of the signal being transmitted. These manners include applying a predetermined fixed voltage to the control input or a less precise envelope tracking signal which is derived by a second amplitude control circuit (120) from the amplitude component (R).

An envelope tracking amplifier having stacked transistors is presented. The envelope tracking amplifier uses dynamic bias voltages at one or more gates of the stacked transistors in addition to a dynamic bias voltage at a drain of a transistor.

There is disclosed an amplifier arrangement comprising a plurality of amplifiers each arranged to amplify one of a plurality of different input signals, the arrangement comprising an envelope tracking modulator for generating a common power supply voltage for the power amplifiers, and further comprising an envelope selector adapted to receive a plurality of signals representing the envelopes of the plurality of input signals, and adapted to generate an output envelope signal representing the one of the plurality of envelopes having the highest level at a particular time instant as the input signal for the envelope tracking modulator.

A method and device for improving the efficiency of an envelope tracking transmitter in which a power amplifier for coupling modulated signals in a carrier frequency to an antenna for transmission. The transmitter comprises a power supply for providing a supply voltage to the power amplifier, and a computation means for providing a waveform indicative of the envelope of the modulated signal to the power supply in order to modify the supply voltage. A lower limit is imposed to the waveform so that the supply voltage to the power supply is always greater than a predetermined value. Moreover, when information is transmitted in times slots which are started and ended by ramp periods, a constant signal, based on the root-mean-square value of the waveform, is used to modify the waveform so that the supply voltage to the power amplifier includes a constant voltage level in the ramp periods.

An apparatus comprises an amplifier having an input coupled to a radio frequency signal through a digital-to-analog circuit, an adaptive power supply having an output coupled to a bias voltage of the amplifier, wherein the output of the adaptive power supply is configured to have a shape similar to an envelope of the radio frequency signal and a feedback circuit comprising a sensing circuit and a mapping circuit, wherein the sensing circuit is configured to sense a current flowing from the adaptive power supply to the amplifier and sense the bias voltage of the amplifier, and wherein the mapping circuit is configured to sense the bias voltage of the amplifier, and wherein the mapping circuit is configured to generate a control signal for dynamically adjusting parameters of a low pass filter so as to stabilize the adaptive power supply.

There is disclosed a method of controlling an envelope tracking amplification stage comprising an envelope modulated power supply, the method comprising: determining a shaping function to be applied to an envelope signal for controlling the envelope modulated power supply in dependence on a system linearity objective in a region of operation of the amplifier in which the output power of the amplifier is dependent upon the supply voltage; and determining a pre-distortion function to be applied to an input signal to be amplified in dependence on a further linearity objective of the system, in a region of operation of the amplifier in which the output of the amplifier is dependent upon the input power to the amplifier.

An envelope tracking power amplifier system time-aligns a supply voltage to an input signal to a power amplifier. The power supply operates in a static mode for low amplitude input signals and operates in a dynamic mode for high amplitude input signals. In the static mode, the power supply produces a substantially constant supply voltage independent of the amplitude of the input signal. In the dynamic mode the power supply produces a dynamically varying envelope tracking supply voltage based on the amplitude of the input signal. A first delay is determined based on portions of the input and output signals captured during static operation of the power supply and a second delay is determined based on portions of the input and output signals captured during dynamic operation. A delay mismatch is estimated based on a difference between the first and second delays.

There is disclosed an envelope tracked power supply comprising a high bandwidth, low delay closed loop switch mode power supply stage comprising: a pulse width modulator for generating a width modulated pulse in dependence on an input signal and an output voltage of the switch mode power supply stage; a wideband transformer, having a winding of a first side connected to receive the modulated pulse, and a winding of a second side; and an output stage connected to the winding of the second side of the transformer, and for generating the output voltage in dependence on the modulated pulse induced in the winding of the second side.