Envelope tracking system

Abstract: A multimode envelope tracking (ET) circuit and related apparatus is provided. The multimode ET circuit is configured to provide an ET voltage(s) to an amplifier circuit(s) for amplifying a radio frequency (RF) signal(s) that may correspond to a wider range of modulation bandwidth. In this regard, the multimode ET circuit is configured to switch dynamically and opportunistically between different operation modes based on the modulation bandwidth of the RF signal(s). In examples discussed herein, the multimode ET circuit is configured to support a single amplifier circuit in a high-modulation-bandwidth mode and an additional amplifier circuit(s) in a mid-modulation-bandwidth mode and a low-modulation-bandwidth mode. By switching dynamically and opportunistically between different operation modes, it may be possible to reduce undesired series resonance that may cause distortion in the ET voltage(s), thus helping to improve efficiency and performance of the amplifier circuit(s) supported by the multimode ET circuit.

Abstract: An envelope tracking (ET) integrated circuit (IC) (ETIC) is provided. The ETIC is configured to generate an ET voltage based on a supply voltage(s) and provide the ET voltage to an amplifier circuit(s) for amplifying a radio frequency (RF) signal(s). Notably, the RF signal(s) may be modulated in different modulation bandwidths and the amplifier circuit(s) may correspond to different load-line impedances. Accordingly, the ETIC may need to adapt the ET voltage such that the ETIC and the amplifier circuit(s) can operate at higher efficiencies. In examples discussed herein, the ETIC is configured to determine a time-variant peak of the ET voltage and adjust the supply voltage(s) accordingly. As a result, it may be possible to improve operating efficiency of the ETIC in face of a wide range of bandwidth and/or load-line requirements.

Abstract: A group delay optimization circuit is provided. The group delay optimization circuit receives a first signal (e.g., a voltage signal) and a second signal (e.g., a current signal). Notably, the first signal and the second signal may experience different group delays that can cause the first signal and the second signal to misalign at an amplifier circuit configured to amplify a radio frequency (RF) signal. The group delay optimization circuit is configured to determine a statistical indicator indicative of a group delay offset between the first signal and the second signal. Accordingly, the group delay optimization circuit may minimize the group delay offset by reducing the statistical indicator to below a defined threshold in one or more group delay optimization cycles. As a result, it may be possible to pre-compensate for the group delay offset in the RF signal, thus helping to improve efficiency and linearity of the amplifier circuit.

Abstract: An adaptive frequency equalizer for wide modulation bandwidth envelope tracking (ET) is provided. In this regard, an ET integrated circuit (ETIC) provides an ET power signal for one or more power amplifiers (PAs). A voltage error can occur in the ET power signal due to variable impedance sources, such as a variable load impedance at the PA and a variable trace inductance between the ETIC and the PA. The adaptive frequency equalizer disclosed herein works to adaptively correct for such voltage errors to provide improved overall power signal tracking at the PA, especially where there is a large trace inductance from the ETIC being located several centimeters (cm) away from the PA. Thus, embodiments of the adaptive frequency equalizer enhance ET performance for radio frequency (RF) systems having a modulation bandwidth of 100 megahertz (MHz) or above.

Abstract: A dual-input envelope tracking (ET) integrated circuit (ETIC) and related apparatus are provided. The dual-input ETIC includes an ET voltage circuit configured to generate an ET voltage based on an ET voltage and a first set of parameters. The ET voltage may be provided to a power amplifier circuit(s) for amplifying a radio frequency (RF) signal(s) in an ET power range. The dual-input ETIC also includes a target voltage processing circuit configured to generate the ET target voltage based on a second set of parameters. The dual-input ETIC further includes a control circuit configured to determine the first set of parameters and the second set parameters based at least on the ET power range of the power amplifier circuit(s). As such, it may be possible to optimize the dual-input ETIC performance in a wide-range of modulation bandwidth, thus helping to improve linearity and efficiency of the power amplifier circuit(s).

Abstract: 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.

Abstract: Apparatus and methods for envelope tracking are disclosed. In one embodiment, a power amplifier system including a power amplifier and an envelope tracker is provided. The power amplifier is configured to amplify a radio frequency (RF) signal, and the envelope tracker is configured to control a supply voltage of the power amplifier using an envelope of the RF signal. The envelope tracker includes a buck converter for generating a buck voltage from a battery voltage and a digital-to-analog conversion (DAC) module for adjusting the buck voltage based on the envelope of the RF signal to generate the supply voltage for the power amplifier.

Abstract: 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.

Abstract: An improved charge pump circuit includes one switch element driven by a ramp waveform to precisely control the output voltage. The circuit includes a switch group (130) having one or more switch elements for transferring a charge to one or more capacitors (C1), a feedback circuit having an error amplifier (126) for amplifying a difference between a divided output voltage and a reference voltage (V ref), a compensation circuit (131, 132) for phase compensating the feedback network, an oscillator (127) for generating the ramp waveform, and a control circuit (128) for driving the one or more switch elements. At least one of the switch elements has a resistance that can be adjusted externally and is driven by the ramp waveform such that its resistance varies with time. Accordingly, the charge transferred from a power source (VDD) to the one or more capacitors (C1) can easily be adjusted. When the charge transferred is small, the on-time of the ramp waveform is short and the average value of the resistance is large. The average resistance of the switch group varies when the voltage of the power source varies, so that an output with a fixed voltage and low ripple voltage can be obtained.

Abstract: An integrated circuit is described for providing a power supply to a radio frequency (RF) power amplifier (PA). The integrated circuit includes a low-frequency power supply path including a switching regulator and a high-frequency power supply path arranged to regulate an output voltage of a combined power supply at an output port of the integrated circuit for coupling to a load. The combined power supply is provided by the low-frequency power supply path and high-frequency power supply path. The high-frequency power supply path includes: an amplifier including a voltage feedback and arranged to drive a power supply signal on the high-frequency power supply path; and a capacitor operably coupled to the output of the amplifier and arranged to perform dc level shifting of the power supply signal.