Multi-stage envelope tracking system with separate dc and ac paths

Abstract

A multi-stage envelope tracking system with separate DC and AC paths is provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-DC converter that outputs a plurality of regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, an AC path filter coupled between an output of the MLS modulator and the power amplifier supply voltage, and a DC path filter coupled between a DC voltage and the power amplifier supply voltage.

Description

Technical Field

[0001] Various embodiments of the present invention relate to electronic systems, and more particularly to power amplifiers for radio frequency (RF) electronic devices. Background Technology

[0002] In RF communication systems, power amplifiers are used to amplify the RF signals transmitted via antennas. Managing the power of RF signal transmission to extend battery life and / or provide appropriate transmission power levels is important.

[0003] Examples of RF communication systems with one or more power amplifiers include, but are not limited to, mobile phones, tablets, base stations, network access points, customer premises equipment (CPE), laptops, and wearable electronic devices. For example, in wireless devices communicating using cellular standards, wireless local area network (WLAN) standards, and / or any other suitable communication standards, power amplifiers can be used to amplify RF signals. For fifth-generation (5G) communication in Frequency Range 1 (FR1), the RF signal can have frequencies ranging from approximately 30 kHz to 300 GHz, such as frequencies ranging from approximately 410 MHz to approximately 7.125 GHz. Summary of the Invention

[0004] In some embodiments, this disclosure relates to an envelope tracking system including a power amplifier configured to amplify a radio frequency (RF) signal and receive power from a power amplifier supply voltage; and an envelope tracker configured to generate the power amplifier supply voltage based on an envelope signal corresponding to the envelope of the RF signal. The envelope tracker includes: a DC-to-DC converter configured to output a plurality of regulated voltages; a modulator configured to generate a modulator output voltage based on the plurality of regulated voltages and the envelope signal; a first filter coupled between the modulator output voltage and the power amplifier supply voltage; and a second filter coupled between the DC voltage and the power amplifier supply voltage.

[0005] In various embodiments, the DC-DC converter is also configured to generate a DC voltage. According to several embodiments, the DC-DC converter is configured to generate a DC voltage having a different pulse width modulator sequence relative to each of a plurality of regulated voltages.

[0006] In several embodiments, the DC-DC converter is configured to receive a battery voltage and generate multiple regulated voltages and DC voltages based on the DC-DC conversion that provides the battery voltage.

[0007] In some embodiments, each of the plurality of regulated voltages has a different voltage level.

[0008] In various embodiments, the envelope tracker also includes a plurality of decoupling capacitors, each decoupling capacitor being coupled between ground and a corresponding one of a plurality of regulated voltages.

[0009] In several embodiments, the modulator includes a plurality of switches, each switch being coupled between a modulator output voltage and a corresponding one of a plurality of regulated voltages.

[0010] In some embodiments, the first filter includes at least one series inductor and at least one parallel capacitor. According to several embodiments, the first filter also includes a DC blocking capacitor connected in series between the modulator output voltage and the power amplifier supply voltage.

[0011] In various embodiments, the second filter includes at least one series inductor and at least one parallel capacitor.

[0012] In several embodiments, the envelope tracker further includes a controllable delay circuit configured to control the relative delay between the AC path through the first filter and the DC path through the second filter. According to several embodiments, the controllable delay circuit includes a plurality of controllable delay buffers, each configured to control the delay of a corresponding one of a plurality of regulated voltages.

[0013] In various embodiments, at least 75 percent of the energy supplied from the envelope tracker to the power amplifier is carried through the DC path of the second filter.

[0014] In some embodiments, this disclosure relates to an envelope tracker. The envelope tracker includes a power amplifier supply voltage terminal configured to output a power amplifier supply voltage, a DC-DC converter configured to output multiple regulated voltages based on regulated battery voltage, a modulator configured to generate a modulator output voltage based on the multiple regulated voltages and an envelope signal, an AC path filter coupled between the modulator output voltage and the power amplifier supply voltage, and a DC path filter coupled between the DC voltage and the power amplifier supply voltage.

[0015] In several embodiments, the DC-DC converter is also configured to generate a DC voltage. According to several embodiments, the DC-DC converter is configured to generate a DC voltage having a different pulse width modulator sequence relative to each of a plurality of regulated voltages.

[0016] In some embodiments, the DC-DC converter is configured to receive a battery voltage and generate multiple regulated voltages and DC voltages based on the DC-DC conversion that provides the battery voltage.

[0017] In various embodiments, each of the plurality of regulated voltages has a different voltage level.

[0018] In several embodiments, the envelope tracker also includes a plurality of decoupling capacitors, each decoupling capacitor being coupled between ground and a corresponding one of a plurality of regulated voltages.

[0019] In some embodiments, the modulator includes a plurality of switches, each switch being coupled between the modulator output voltage and a corresponding one of a plurality of regulated voltages.

[0020] In various embodiments, the AC path filter includes at least one series inductor and at least one parallel capacitor. According to several embodiments, the AC path filter also includes a DC blocking capacitor connected in series between the modulator output voltage and the power amplifier supply voltage.

[0021] In several embodiments, the DC path filter includes at least one series inductor and at least one parallel capacitor.

[0022] In various embodiments, the envelope tracker further includes a controllable delay circuit configured to control the relative delay between the AC path through the first filter and the DC path through the second filter. According to several embodiments, the controllable delay circuit includes a plurality of controllable delay buffers, each configured to control the delay of a corresponding one of a plurality of regulated voltages.

[0023] In some embodiments, the DC path filter carries at least 75 percent of the energy supplied from the envelope tracker to the power amplifier's power supply voltage terminals.

[0024] In some embodiments, this disclosure relates to a mobile device. The mobile device includes: a transceiver configured to generate a radio frequency (RF) transmit signal; front-end circuitry including a power amplifier configured to amplify the RF transmit signal and receive power from a power amplifier supply voltage; and power management circuitry including an envelope tracker configured to generate a power amplifier supply voltage based on an envelope signal corresponding to an envelope of the RF transmit signal. The envelope tracker includes: a DC-DC converter configured to output a plurality of regulated voltages; a modulator configured to generate a modulator output voltage based on the plurality of regulated voltages and the envelope signal; a first filter coupled between the modulator output voltage and the power amplifier supply voltage; and a second filter coupled between the DC voltage and the power amplifier supply voltage.

[0025] In some embodiments, the DC-DC converter is further configured to generate a DC voltage. According to several embodiments, the DC-DC converter is configured to generate a DC voltage having a different pulse width modulator sequence relative to each of a plurality of regulated voltages.

[0026] In several embodiments, the mobile device also includes a battery that provides a battery voltage, and a DC-DC converter is configured to generate multiple regulated voltages and DC voltages based on the DC-DC conversion that provides the battery voltage.

[0027] In some embodiments, each of the plurality of regulated voltages has a different voltage level.

[0028] In various embodiments, the envelope tracker also includes a plurality of decoupling capacitors, each decoupling capacitor being coupled between ground and a corresponding one of a plurality of regulated voltages.

[0029] In several embodiments, the modulator includes a plurality of switches, each switch being coupled between a modulator output voltage and a corresponding one of a plurality of regulated voltages.

[0030] In some embodiments, the first filter includes at least one series inductor and at least one parallel capacitor. According to several embodiments, the first filter also includes a DC blocking capacitor connected in series between the modulator output voltage and the power amplifier supply voltage.

[0031] In several embodiments, the second filter includes at least one series inductor and at least one parallel capacitor.

[0032] In various embodiments, the envelope tracker further includes a controllable delay circuit configured to control the relative delay between the AC path through the first filter and the DC path through the second filter. According to several embodiments, the controllable delay circuit includes a plurality of controllable delay buffers, each configured to control the delay of a corresponding one of a plurality of regulated voltages.

[0033] In some embodiments, at least 75 percent of the energy supplied from the envelope tracker to the power amplifier is carried through the DC path of the second filter.

[0034] In some embodiments, this disclosure relates to an envelope tracking method. The method includes: amplifying a radio frequency (RF) signal using a power amplifier; supplying power to the power amplifier using a power amplifier supply voltage; outputting a plurality of regulated voltages from a DC-DC converter; and generating a modulator output voltage using a modulator based on the plurality of regulated voltages and an envelope signal, the envelope signal corresponding to the envelope of the RF signal. The method further includes: controlling the power amplifier supply voltage using a first filter between the modulator output voltage and the power amplifier supply voltage; and controlling the power amplifier supply voltage using a second filter between a DC voltage and the power amplifier supply voltage.

[0035] In several embodiments, the method further includes using a DC-DC converter to generate a DC voltage. According to several embodiments, the method also includes generating a DC voltage having a different pulse width modulator sequence relative to each of a plurality of regulated voltages.

[0036] In various embodiments, the method also includes generating multiple regulated voltages and DC voltages based on a DC-DC conversion that provides the battery voltage.

[0037] In some embodiments, each of the plurality of regulated voltages has a different voltage level.

[0038] In several embodiments, the method further includes using a series-connected DC blocking capacitor of the first filter to provide DC blocking.

[0039] In various embodiments, the method further includes using a controllable delay circuit to control the relative delay between the AC path through the first filter and the DC path through the second filter. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a mobile device according to one embodiment.

[0041] Figure 2 This is a schematic diagram of one embodiment of an envelope tracking system for a power amplifier.

[0042] Figure 3A This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0043] Figure 3B This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0044] Figure 3C This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0045] Figure 3D This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0046] Figure 4 It is a graph of efficiency versus output power.

[0047] Figure 5 This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0048] Figure 6 This is a schematic diagram of another embodiment of an envelope tracking system for a power amplifier.

[0049] Figure 7 This is a schematic diagram of a mobile device according to another embodiment.

[0050] Figure 8 This is a schematic diagram of one embodiment of a communication system for transmitting radio frequency (RF) signals.

[0051] Figure 9 This is a schematic diagram of a multi-level power supply (MLS) modulation system according to one embodiment.

[0052] Figure 10 This is a schematic diagram of an MLS DC-DC converter according to one embodiment.

[0053] Figure 11 This is a schematic diagram illustrating an example of timing for MLS DC-DC conversion.

[0054] Figure 12 This is a schematic diagram of an example of MLS envelope tracking for continuous wave signals.

[0055] Figure 13 This is a schematic diagram illustrating an example of the envelope frequency distribution used for various signal waveforms. Detailed Implementation

[0056] The following detailed description of certain embodiments presents various descriptions of particular embodiments. However, the innovations described herein can be embodied in a variety of different ways, for example, as defined and covered by the claims. In this specification, reference is made to the accompanying drawings, wherein the same reference numerals may denote the same or functionally similar elements. It should be understood that the elements shown in the figures are not necessarily drawn to scale. Furthermore, it should be understood that some embodiments may include more elements than a subset of those shown in and / or shown in the figures. Additionally, some embodiments may incorporate any suitable combination of features from two or more figures.

[0057] Envelope tracking is a technique used to improve the power-added efficiency (PAE) of a power amplifier by efficiently controlling the voltage level of the power amplifier's supply voltage relative to the envelope of the radio frequency (RF) signal amplified by the power amplifier. Therefore, when the envelope of the RF signal increases, the voltage supplied to the power amplifier can be increased. Similarly, when the envelope of the RF signal decreases, the voltage supplied to the power amplifier can be decreased to reduce power consumption.

[0058] A multilevel envelope tracker may include a multilevel supply (MLS) DC-DC converter that generates two or more regulated voltages of different voltage levels, an MLS modulator that outputs a selected regulated voltage chosen from the regulated voltages, and a filter for filtering the output of the MLS modulator to generate a power amplifier supply voltage for a power amplifier.

[0059] Multistage envelope trackers can suffer from efficiency degradation when both DC and AC currents used to supply the power amplifier voltage flow through the switches of the MLS modulator and / or common filter. For example, power losses can occur in the DC resistance of the modulator's switches and / or the inductors of the filter.

[0060] While the DC resistance of the switch can be implemented to be low (e.g., a fraction of the DC load of a power amplifier), implementing the switch in this way results in a relatively large layout and / or significant switching losses. For example, when the required source impedance is around 0.2 ohms, the switch of an MLS modulator may be limited to achieving an on-resistance of less than 0.2 ohms, which leads to a relatively large switch layout.

[0061] A multi-stage envelope tracking system with separate DC and AC paths is provided. In some embodiments, an envelope tracking system for generating a power amplifier supply voltage is provided. The envelope tracking system includes: an MLS DC-DC converter that outputs multiple regulated voltages; an MLS modulator that controls the selection of the regulated voltages over time based on an envelope signal corresponding to the envelope of an RF signal amplified by the power amplifier; an AC path filter coupled between the output of the MLS modulator and the power amplifier supply voltage; and a DC path filter coupled between the DC voltage and the power amplifier supply voltage.

[0062] Enhanced efficiency of the envelope tracking system can be achieved by including a DC path through a DC path filter and a separate AC path through an AC path filter. For example, a low-frequency current, such as DC current, can be supplied through the DC path filter (e.g., via a filter inductor), thereby relaxing the size and / or DC resistance constraints of the modulator switches. Consequently, lower switching losses can be achieved in the AC path, thus improving overall system efficiency. In one example, the DC path carries at least 75% of the energy supplied by the envelope tracking system to the power amplifier.

[0063] Since fast envelope signals can have DC-centric energy content, the DC path can provide an efficient path for low-frequency energy content. Furthermore, DC path filters can include relatively small component sizes because the filter's inductors can operate without DC saturation. In one example, the DC path filter is implemented at approximately half the size of an AC path filter. In some implementations, the AC path filter includes a series DC blocking capacitor to assist in DC blocking through the AC path filter.

[0064] In some implementations, the DC voltage is a regulated voltage from a DC-DC converter. For example, an MLS DC-DC converter can also be used to generate a DC voltage. In such implementations, the voltage level of the DC voltage may be the same as or different from the voltage level of one of the regulated voltages supplied to the MLS modulator.

[0065] Figure 1 This is a schematic diagram of a mobile device 70 according to one embodiment. The mobile device 70 includes a main antenna 1, a diversity antenna 2, a main antenna tuning circuit 3, a diversity antenna tuning circuit 4, a double-pole double-throw (DPDT) antenna diversity switch 5, a main front-end module 6, a diversity front-end module 7, a battery 8, an MLS envelope tracker 9, a transceiver 10, a baseband modem 11, and an application processor 12.

[0066] Although one embodiment of a mobile device has been shown, the teachings of this article are applicable to mobile devices implemented in a variety of ways. Therefore, other implementations are also possible.

[0067] In the illustrated embodiment, the main front-end module 6 includes a first power amplifier 21, a second power amplifier 22, a third power amplifier 23, a fourth power amplifier 24, a first low-noise amplifier 31, a second low-noise amplifier 32, a third low-noise amplifier 33, a duplexer 42, a transmit / receive band switch 41, a transmit filter 43, a first duplexer 45, a second duplexer 46, a third duplexer 47, a first receive filter 51, a second receive filter 52, a third receive filter 53, a first directional coupler 59, and a second directional coupler 60. Additionally, the diversity front-end module 7 includes a first low-noise amplifier 35, a second low-noise amplifier 36, a first receive filter 55, a second receive filter 56, a first receive band selection switch 61, and a second receive band selection switch 62.

[0068] While one embodiment of the front-end circuitry has been shown, other implementations of the front-end circuitry are possible. For example, the front-end circuitry may include a power amplifier (PA), a low-noise amplifier (LNA), a filter, a switch, a phase shifter, a duplexer, and / or other suitable circuitry for processing RF signals transmitted and / or received from one or more antennas. Example functions of the front-end include, but are not limited to, amplifying the signal for transmission, amplifying the received signal, filtering the signal, switching between different frequency bands, switching between different power modes, switching between transmit and receive modes, duplexing the signal, multiplexing the signal (e.g., dual-signal or triple-signal), or some combination thereof.

[0069] Therefore, other implementations can be used, such as a main front-end module, a diversity reception front-end module, antenna selection, and / or antenna tuning.

[0070] like Figure 1As shown, the MLS envelope tracker 9 is used to generate one or more power amplifier supply voltages for the power amplifier used in the mobile device 70 to amplify the RF signal used for wireless transmission. In the illustrated embodiment, the MLS envelope tracker 9 receives a battery voltage V from the battery 8. BATT And generate the first power amplifier supply voltage V for the first power amplifier 21. PA1 and the second power amplifier supply voltage V for the second power amplifier 22 PA2 Although an example of the MLS envelope tracker 9 generating two power amplifier supply voltages has been shown, the MLS envelope tracker 9 can generate more or fewer power amplifier supply voltages.

[0071] MLS envelope tracker 9 controls the supply voltage V of the first power amplifier. PA1 To track the envelope of the first RF signal amplified by the first power amplifier 21. Additionally, the MLS envelope tracker 9 controls the supply voltage V of the second power amplifier. PA2 The MLS envelope tracker 9 tracks the envelope of the second RF signal amplified by the second power amplifier 22. In some embodiments, the MLS envelope tracker 9 receives one or more envelope signals from the baseband modem 11. For example, the MLS envelope tracker 9 may receive a first envelope signal indicating the envelope of the first RF signal and a second envelope signal indicating the envelope of the second RF signal.

[0072] Battery 8 can be any suitable battery used in mobile device 70, including, for example, a lithium-ion battery. Battery voltage V BATT The DC-DC converter of the MLS envelope tracker 9 is regulated to produce a regulated voltage for multi-stage envelope tracking in accordance with the teachings of this document.

[0073] Transceiver 10 generates RF signals for transmission and processes input RF signals received from main antenna 1 and diversity antenna 2. It should be understood that various functions associated with the transmission and reception of RF signals can be implemented through... Figure 1 The RF signal is typically represented as one or more components of transceiver 10. In one example, separate components (e.g., separate circuits or chips) may be provided to handle certain types of RF signals.

[0074] The baseband modem 11 provides a digital representation of the transmitted signal to the transceiver 10, which processes the transmitted signal to generate an RF signal for transmission. The baseband modem 11 also processes a digital representation of the received signal provided by the transceiver 10.

[0075] like Figure 1As shown, the baseband modem 11 is coupled to the application processor 12, which provides primary application processing in the mobile device 70. The application processor 12 can provide a variety of functions, such as providing system capabilities suitable for supporting applications, including but not limited to memory management, graphics processing, and / or multimedia decoding.

[0076] Although the mobile device 70 illustrates an example of an RF system including a multi-level envelope tracker, a wide variety of RF systems may include multi-level envelope trackers implemented in accordance with the teachings of this document.

[0077] Figure 2-3C Figures 5 and 6 illustrate schematic diagrams of various embodiments of an envelope tracking system for a power amplifier. However, the teachings herein apply to envelope trackers implemented in a variety of ways. Therefore, other implementations are possible.

[0078] Figure 2 This is a schematic diagram of one embodiment of an envelope tracking system 100 for a power amplifier 71. The envelope tracking system 100 includes an MLS DC-DC converter 72, a DC path filter 73, an MLS modulator 81, and an AC path filter 91. The MLS DC-DC converter 72 is also referred to herein as a switching regulator.

[0079] Power amplifier 71 amplifies the RF input signal. IN To generate RF output signal RF OUT The MLS modulator 81 receives the signal relative to the RF input signal RF. IN The envelope signal (ENVELOPE) varies with the envelope of the signal. The envelope signal can be analog or digital.

[0080] In the illustrated embodiment, the MLS DC-DC converter 72 receives the battery voltage V. BATT It also provides DC-DC conversion to generate various regulated voltages V at different voltage levels. MLSa V MLSb V MLSc ...V MLSn Although four MLS voltages are depicted as examples, as shown in the ellipse, the MLS DC-DC converter 72 can produce more or less MLS voltage. In this embodiment, the MLS DC-DC converter 72 also regulates the battery voltage V. BATT To generate DC voltage V DC DC voltage V DC It can have the same voltage as the adjustable voltage V MLSa V MLSb V MLSc ...V MLSn One is the same or different voltage level.

[0081] MLS modulator 81 receives regulated voltage V MLSa V MLSb V MLSc ...V MLSn The MLS modulator 81 outputs an envelope signal and outputs the modulator output voltage to an AC path filter 91. In some embodiments, the MLS modulator 81 controls the output voltage by selecting an appropriate regulation voltage based on the envelope signal over time. For example, the MLS modulator 81 may include a set of switches for selectively connecting the regulation voltage V based on the value of the envelope signal. MLSa V MLSb V MLSc ...V MLSn To the output of the modulator.

[0082] DC path filter 73 and AC path filter 91 respectively filter the DC voltage V from MLS DC-DC converter 72 DC The output of the MLS modulator 81 is filtered to generate the power amplifier supply voltage V for the power amplifier 71. PA .

[0083] Enhanced efficiency of the envelope tracking system 100 can be achieved by including a DC path through DC path filter 73 and a separate AC path through AC path filter 91. For example, low-frequency current (including but not limited to DC current) can be provided through DC path filter 73, thereby relaxing the size and / or DC resistance constraints of the MLS modulator switches.

[0084] Therefore, lower switching losses in the AC path can be achieved, thereby improving overall system efficiency. In one example, the DC path bearer envelope tracking system 100 provides at least 75% of the energy to the power amplifier 71.

[0085] Figure 3A This is a schematic diagram of another embodiment of the envelope tracking system 140 for power amplifier 101. The envelope tracking system 140 includes an envelope tracking integrated circuit (IC) 102, a DC path filter 103, an AC path filter 104, a DAC circuit 105, an envelope filter 106, first to fourth decoupling capacitors 111-114, and an inductor 117, respectively.

[0086] although Figure 3A The diagram illustrates one embodiment of an envelope tracking system, but the teachings herein apply to envelope tracking systems implemented in various ways. Therefore, other implementations are possible.

[0087] In the illustrated embodiment, the envelope tracking IC 102 includes an MLS switching circuit 121, a digital control circuit 122, a baseband MLS modulator 123, and a modulator control circuit 124. Figure 3A The envelope tracking IC102 is described as having multiple pins or pads for providing features such as receiving battery voltage (V). BATT ), communicates via Serial Peripheral Interface (SPI), and outputs DC voltage V. DC It performs various functions, including receiving the envelope signal (ENVELOPE), connecting to decoupling capacitors 111-114, and connecting to inductor 117. The envelope tracking IC is also referred to herein as an envelope tracking semiconductor chip or chip.

[0088] MLS switching circuit 121 controls the current through inductor 117 to provide voltage regulation. For example, MLS switching circuit 121 may include a switch and a controller that uses any suitable regulation scheme (including, but not limited to, pulse width modulation) to turn the switch on and off to provide DC-DC conversion. In the illustrated embodiment, MLS switching circuit 121 outputs four different voltage levels of regulated MLS voltage and regulated DC voltage V. DC However, the MLS switching circuit 121 can be implemented to output more or less regulated voltage.

[0089] As shown in Figure 3A, the MLS switching circuit 121 is controlled by a digital control circuit 122. The digital control circuit 122 provides programmability to the MLS switching circuit 121, including but not limited to controlling one or more adjustable voltages output by the MLS switching circuit 121. Figure 3A As shown, the digital control circuit 122 is coupled to the SPI bus. In some embodiments, the digital control circuit 122 controls the MLS switching circuit 121 based on data received via the SPI bus and / or other chip interfaces.

[0090] The MLS switching circuit 121 can also be controlled by the modulator control circuit 124. In one example, the DC voltage V is adjusted. DC It is controlled at least in part by the modulator control circuit 124.

[0091] The baseband MLS modulator 123 includes an AC path filter 104 coupled to the power amplifier supply voltage V. PA The output of the modulator. In some embodiments, the baseband MLS modulator 123 includes a switch 104 coupled between each regulated MLS voltage and an AC path filter. Additionally, the switch of the modulator is selectively opened or closed by a modulator controller 124 based on the envelope signal.

[0092] In the illustrated embodiment, the DC path filter 103 includes a parallel capacitor 127 and a series inductor 128. Additionally, the AC path filter 104 includes a first series inductor 131, a second series inductor 132, a first parallel capacitor 135, and a second parallel capacitor 136. Although in Figure 3A The document describes example implementations of DC-path and AC-path filters, but the teachings herein apply to DC-path and AC-path filters implemented in various ways. Therefore, other implementations of the filters can be used in accordance with the teachings herein.

[0093] In some implementations, one or more components of the filter are controllable (e.g., digitally programmable and / or analog tuned) to provide enhanced flexibility and / or configurability. For example, in the illustrated embodiment, the first parallel capacitor 135 and the second parallel capacitor 136 are controllable. Although two examples of controllable filter components are shown, other filter components may be additionally or alternatively implemented as controllable.

[0094] Figure 3B This is a schematic diagram of another embodiment of the envelope tracking system 150 for power amplifier 101. Figure 3B The envelope tracking system 150 is similar to Figure 3A The envelope tracking system 140 differs from the envelope tracking system 150 in that it includes a different implementation of the AC path filter 144.

[0095] For example, with Figure 3A Compared to the AC path filter 104, Figure 3B The AC path filter 144 also includes a DC blocking capacitor 138 for isolating low-frequency currents passing through the AC path filter 144. In the illustrated embodiment, the DC blocking capacitor 138 is coupled to the output of the AC path filter 144.

[0096] By including the DC blocking capacitor 138, lower switching losses can be achieved in the AC path, thereby improving overall system efficiency. For example, including the DC blocking capacitor 138 can help increase the percentage of energy carried by the DC path through the DC path filter 103 relative to the energy carried by the AC path through the AC path filter 144. In one example, the DC path through the DC path filter 103 carries at least 75% of the energy supplied to the power amplifier 101 by the envelope tracking system 150.

[0097] Figure 3C This is a schematic diagram of another embodiment of the envelope tracking system 160 for power amplifier 101. Figure 3C The envelope tracking system 160 is similar to Figure 3BThe envelope tracking system 150 differs from the envelope tracking system of Figure 160 in that it includes different implementations of the AC path filter 154.

[0098] For example, with Figure 3B Compared to the AC path filter 144, Figure 3C The AC path filter 154 includes a DC blocking capacitor 138 coupled to the input of the filter. The DC blocking capacitor can be included in the path filter at various locations in the AC circuit, including, for example, at the input, the output, or along the signal path between the input and the output.

[0099] Figure 3D This is a schematic diagram of another embodiment of the envelope tracking system 170 for power amplifier 101. Figure 3D The envelope tracking system 170 is similar to Figure 3A The envelope tracking system 140 differs from the envelope tracking system 170 in that it includes an envelope tracking IC 102 that operates with two MLS regulating voltages. Furthermore, given the smaller number of MLS regulating voltages, decoupling capacitors 113 and 114 have been omitted.

[0100] Figure 3D The envelope tracking system 170 has the advantage of low complexity. Furthermore, the envelope tracking system 170 is well-suited for applications using symbol-by-symbol tracking applicable to high-bandwidth modulation. For example, when using symbol-by-symbol tracking, two MLS voltages can be programmed and used continuously at a symbol rate (e.g., 16 µs). Therefore, the MLS modulator 123 can change the voltage used to generate the power amplifier supply voltage by switching to a new voltage-holding capacitor.

[0101] When using symbol tracking for tracking, less filtering can be used, but AC / DC separation is still beneficial and avoids the need for series switches.

[0102] Figure 4 This is a graph showing efficiency versus output power. The graph includes three combined power amplifiers and curves showing the efficiency versus output power of the envelope tracker under different simulated scenarios. For example, the first curve 171 corresponds to a simulation where a 0.1-ohm switching resistor is included in the DC path, the second curve 172 is LTE efficiency, and the third curve 173 corresponds to a simulation where a 1.0-ohm switching resistor is included in the DC path. Improved efficiency can also be achieved by providing lower DC path resistance through separate AC and DC paths.

[0103] although Figure 4The diagram shows a specific example of simulation results for an envelope tracking system, but other simulation results are possible. For example, simulation results can vary based on a variety of factors, including but not limited to simulation parameters (including operating frequency), circuit topology, and / or manufacturing process.

[0104] Figure 5 This is a schematic diagram of another embodiment of the envelope tracking system 180 used for power amplifier 71. Figure 5 The envelope tracking system 180 is similar to Figure 2 The envelope tracking system 100 differs from the envelope tracking system 150 in that it also includes a controllable delay circuit 98.

[0105] In the illustrated embodiment, the envelope tracking system 180 operates with a DC path delay t1 from the MLS DC-DC converter 72 through the DC path filter 73 to the power input of the power amplifier 71. Furthermore, the envelope tracking system 180 operates with an AC path delay t2 from the MLS DC-DC converter 72 through the controllable delay circuit 98, the MLS modulator 81, and the AC path filter 91 to the power input of the power amplifier 71.

[0106] By including a controllable delay circuit 98, the relative delay between the AC path and the DC path can be controlled to improve the efficiency of the envelope tracking system 180. In some embodiments, the delay of the controllable delay circuit 98 is operated such that the desired phase shift is substantially matched with the DC path delay t1 and the AC path delay t2 to improve efficiency.

[0107] For example, without compensation for the delay difference, currents in the AC and DC paths will conflict because the control bandwidth of the DC path is smaller than that of the AC path. In this example, the AC path is delayed by a controllable delay circuit 98 to control the relative delay of the DC path seen by the load. In some implementations, a phase shift of approximately 90 degrees over the bandwidth where the combination occurs provides relatively high efficiency. In some implementations, a digital state machine or other suitable control circuitry operates to provide control that achieves a phase delay of approximately 90 degrees.

[0108] Figure 6 This is a schematic diagram of another embodiment of the envelope tracking system 200 for power amplifier 101. Figure 6 The envelope tracking system 200 is similar to Figure 3A The envelope tracking system 140 differs from the envelope tracking system in Figure 200, which includes different implementations of the envelope tracking IC 182.

[0109] For example, with Figure 3A Compared to the envelope tracking IC 102, Figure 6The envelope tracking IC 182 also includes controllable delay buffers 191-194. For example... Figure 3A As shown, the controllable delay buffers 191-194 provide a controllable delay for each MLS regulated voltage generated by the MLS switching circuit 121, thereby allowing relative adjustment of the AC path delay t2 relative to the DC path delay t1.

[0110] In this embodiment, the delay of the controllable delay buffers 191-194 can be controlled separately by the digital control circuit 122, thereby providing increased flexibility in taking into account any variations in delay between various MLS regulated voltage paths.

[0111] Figure 7 This is a schematic diagram of a mobile device 800 according to another embodiment. The mobile device 800 includes a baseband system 801, a transceiver 802, a front-end system 803, an antenna 804, a power management system 805, a memory 806, a user interface 807, and a battery 808.

[0112] The mobile device 800 can be used to communicate using a variety of communication technologies, including but not limited to 2G, 3G, 4G (including LTE, LTE-Advanced and LTE-Advanced Pro), 5G, WLAN (e.g., Wi-Fi), WPAN (e.g., Bluetooth and ZigBee), WMAN (e.g., WiMax) and / or GPS technology.

[0113] Transceiver 802 generates RF signals for transmission and processes input RF signals received from antenna 804. It should be understood that various functions associated with the transmission and reception of RF signals can be implemented through one or more [unclear - possibly a specific function or interface]. Figure 7 The components represented together as transceiver 802 are implemented. In one example, separate components (e.g., separate circuits or chips) may be provided to handle certain types of RF signals.

[0114] The front-end system 803 assists in regulating signals transmitted to and / or received from the antenna 804. In the illustrated embodiment, the front-end system 803 includes a power amplifier (PA) 811, a low-noise amplifier (LNA) 812, a filter 813, a switch 814, and a duplexer 815. However, other implementations are also possible.

[0115] For example, the front-end system 803 can provide a variety of functionalities, including but not limited to amplifying the signal for transmission, amplifying the received signal, filtering the signal, switching between different frequency bands, switching between different power modes, switching between transmit and receive power modes, signal duplexing, signal multiplexing (e.g., dual-signal or triple-signal), or some combination thereof.

[0116] In some implementations, the mobile device 800 supports carrier aggregation, providing flexibility to increase peak data rates. Carrier aggregation can be used for both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) and can be used to aggregate multiple carriers or channels. Carrier aggregation includes contiguous aggregation of consecutive carriers within the same operating frequency band. Carrier aggregation can also be non-contiguous and can include carriers with separated frequencies in a common frequency band or different frequency bands.

[0117] Antenna 804 may include antennas for various communication types. For example, antenna 804 may include antennas associated with transmitting and / or receiving signals associated with various frequencies and communication standards.

[0118] In some implementations, antenna 804 supports MIMO communication and / or switching diversity communication. For example, MIMO communication uses multiple antennas to transmit multiple data streams on a single radio frequency channel. Due to spatial multiplexing differences in the radio environment, MIMO communication benefits from higher signal-to-noise ratios, improved coding, and / or reduced signal interference. Switching diversity refers to communication that selects a specific antenna to operate at a specific time. For example, a switch can be used to select a specific antenna from a set of antennas based on multiple factors such as observed bit error rate and / or signal strength indicators.

[0119] In some embodiments, the mobile device 800 may operate using beamforming. For example, the front-end system 803 may include a phase shifter having a variable phase controlled by the transceiver 802. Additionally, the phase shifter is controlled to provide beamforming and directivity for transmitting and / or receiving signals using the antenna 804. For example, in the case of signal transmission, the phase of the transmitted signal supplied to the antenna 804 is controlled such that the radiated signal from the antenna 804 uses a combination of constructive and destructive interference to generate a converged transmitted signal exhibiting beam-like quality that propagates with greater signal strength in a given direction. In the case of signal reception, the phase is controlled such that more signal energy is received when the signal arrives at the antenna 804 from a particular direction. In some embodiments, the antenna 804 includes one or more arrays of antenna elements to enhance beamforming.

[0120] Baseband system 801 is coupled to user interface 807 to facilitate the processing of various user inputs and outputs (I / O), such as voice and data. Baseband system 801 provides a digital representation of the transmitted signal to transceiver 802, which processes the transmitted signal to generate an RF signal for transmission. Baseband system 801 also processes a digital representation of the received signal provided by transceiver 802. Figure 7 As shown, the baseband system 801 is coupled to a memory 806 that facilitates operation of the mobile device 800.

[0121] The memory 806 can be used for a variety of purposes, such as storing data and / or instructions to facilitate the operation of the mobile device 800 and / or providing storage of user information.

[0122] The power management system 805 provides multiple power management functions for the mobile device 800. The power management system 805 may include an MLS envelope tracker 860 implemented according to one or more features of this disclosure.

[0123] like Figure 7 As shown, the power management system 805 receives battery voltage from the battery 808. The battery 808 can be any suitable battery used in the mobile device 800, including, for example, a lithium-ion battery.

[0124] Figure 8 This is a schematic diagram of one embodiment of a communication system 950 for transmitting RF signals. The communication system 950 includes a battery 901, an MLS envelope tracker 902, a power amplifier 903, a directional coupler 904, a duplex and switching circuit 905, an antenna 906, a baseband processor 907, a signal delay circuit 908, a digital pre-distortion (DPD) circuit 909, an I / Q modulator 910, an observation receiver 911, an intermodulation detection circuit 912, an envelope delay circuit 921, a coordinate rotation digital computation (CORDIC) circuit 922, a shaping circuit 923, a digital-to-analog converter 924, and a reconstruction filter 925.

[0125] Figure 8 The communication system 950 illustrates an example of an RF system that may include an envelope tracking system implemented according to one or more features of this disclosure. However, the teachings herein apply to RF systems implemented in a variety of ways.

[0126] The baseband processor 907 operates to generate in-phase (I) and quadrature-phase (Q) signals, which correspond to the signal components of a sine wave or signals having desired amplitude, frequency, and phase. For example, the I and Q signals provide an equivalent representation of a sine wave. In some embodiments, the I and Q signals are output in digital format. The baseband processor 907 can be any suitable processor for processing baseband signals. For example, the baseband processor 907 may include a digital signal processor, a microprocessor, a programmable core, or any combination thereof.

[0127] Signal delay circuit 908 provides adjustable delays to the I and Q signals to assist in controlling the differential envelope signals ENV_p and ENV_n provided to the MLS envelope tracker 902 and the RF signal RF provided to the power amplifier 903. IN The relative alignment between them. The amount of delay provided by the signal delay circuit 908 is controlled based on the amount of intermodulation in adjacent frequency bands detected by the intermodulation detection circuit 912.

[0128] The DPD circuit 909 operates to provide digital shaping to the delayed I and Q signals from the signal delay circuit 908 to generate digitally predistorted I and Q signals. In the illustrated embodiment, the DPD provided by the DPD circuit 909 is controlled based on the amount of intermodulation detected by the intermodulation detection circuit 912. The DPD circuit 909 is used to reduce the distortion of the power amplifier 903 and / or increase the efficiency of the power amplifier 903.

[0129] The I / Q modulator 910 receives digitally predistorted I and Q signals, which are processed to generate an RF signal. IN For example, the I / Q modulator 910 may include a DAC configured to convert digitally predistorted I and Q signals into analog format, a mixer for upconverting analog I and Q signals to radio frequency, and a converter for combining the upconverted I and Q signals into an RF signal. IN The signal combiner. In some embodiments, the I / Q modulator 910 may include one or more filters configured to filter the frequency content of the signal processed therein.

[0130] Envelope delay circuit 921 delays the I and Q signals from baseband processor 907. Additionally, CORDIC circuit 922 processes the delayed I and Q signals to generate a representation of the RF signal RF. IN The digital envelope signal of the envelope. Although Figure 8 The implementation using the CORDIC circuit 922 is shown, but the envelope signal can also be obtained in other ways.

[0131] Shaping circuit 923 operates to shape the digital envelope signal to enhance the performance of communication system 950. In some embodiments, shaping circuit 923 includes a shaping table that maps each level of the digital envelope signal to a corresponding shaped envelope signal level. Envelope shaping can help control the linearity, distortion, and / or efficiency of power amplifier 903.

[0132] In the illustrated embodiment, the shaped envelope signal is a digital signal converted into a differential analog envelope signal by the DAC 924. Additionally, the differential analog envelope signal is filtered by a reconstruction filter 925 to generate differential envelope signals ENV_p and ENV_n suitable for use by the differential envelope amplifier of the MLS envelope tracker 902. In some implementations, the reconstruction filter 925 includes a differential low-pass filter.

[0133] Although an example of envelope signaling has been shown, the teachings of this paper apply to envelope signaling implemented in various ways. For example, in another example, the DAC 924 and reconstruction filter 925 are omitted to facilitate the provision of digital envelope data to the MLS envelope tracker 902.

[0134] Continue to refer to Figure 8 The MLS envelope tracker 902 receives the envelope signal from the reconstruction filter 925 and the battery voltage V from the battery 901. BATT The differential envelope signals ENV_p and ENV_n are used to generate a signal RF relative to the voltage power amplifier 903. IN The power amplifier supply voltage V varies with the envelope. CC_PA In this example, power amplifier 903 receives RF signal RF from I / Q modulator 910. IN The amplified RF signal is then converted to a signal via a duplex and switching circuit 905. OUT Provided to antenna 906.

[0135] A directional coupler 904 is located between the output of power amplifier 903 and the input of duplex and switching circuit 905, thereby allowing measurement of the output power of power amplifier 903, excluding the insertion loss of the duplex and switching circuit. The sensed output signal from directional coupler 904 is provided to observation receiver 911, which may include a mixer for providing down-conversion to generate down-converted I and Q signals, and a DAC for generating I and Q observation signals from the down-converted I and Q signals.

[0136] Intermodulation detection circuit 912 determines the intermodulation product between the observed I and Q signals and the I and Q signals from baseband processor 907. Furthermore, intermodulation detection circuit 912 controls the delay provided by DPD circuit 909 and / or signal delay circuit 908 to control the differential envelope signals ENV_p, ENV_n, and RF signal RF. IN The relative alignment between them. In another embodiment, the intermodulation detection circuit 912 additionally or alternatively controls the delay of the signal delay circuit 921.

[0137] By incorporating feedback paths from the output of power amplifier 903 and baseband, the I and Q signals can be dynamically adjusted to optimize the operation of communication system 950. For example, configuring communication system 950 in this way can assist in providing power control, compensating for transmitter impairments, and / or performing DPD.

[0138] Although illustrated as a single stage, power amplifier 903 may include one or more stages. Furthermore, the teachings herein apply to communication systems that include multiple power amplifiers.

[0139] Figure 9 This is a schematic diagram of an MLS modulation system 1050 according to one embodiment. The MLS modulation system 1050 includes a modulator control circuit 1020, an MLS DC-DC converter 1025, a modulator switch group 1027, and a decoupling capacitor group 1030.

[0140] Figure 9 The MLS modulation system 1050 illustrates one embodiment of an MLS modulator circuit suitable for integration into a multi-stage envelope tracker. However, other implementations of the MLS modulator circuit can be included in a multi-stage envelope tracker implemented according to the teachings herein.

[0141] The MLS DC-DC converter 1025 is based on providing battery voltage V. BATT DC-DC conversion to generate the first regulated voltage V MLS1 Second regulating voltage V MLS2 and the third regulating voltage V MLS3 Although an example with three regulated voltages is shown, the MLS DC-DC converter 1025 can produce more or fewer regulated voltages. In some embodiments, at least a portion of the regulated voltage is relative to the battery voltage V. BATT The voltage is increased. Additionally or alternatively, one or more regulating voltages are lower than the battery voltage V. BATT The voltage drop of the voltage.

[0142] The decoupling capacitor bank 1030 assists in stabilizing the regulated voltage generated by the MLS DC-DC converter 1025. For example, Figure 9 The decoupling capacitor bank 1030 includes a first regulating voltage V MLS1 The first decoupling capacitor 1031 is used for the second voltage regulator V. MLS2 The second decoupling capacitor 1032 and the third regulating voltage V MLS3 The third decoupling capacitor is 1033.

[0143] Continue to refer to Figure 9 The modulator switch group 1027 includes connections to the modulator output (MOD). OUT ) and the first regulating voltage V MLS1 The first switch 1041 is connected to the output of the modulator and the second regulated voltage V. MLS2 The second switch 1042 between, and the output of the modulator and the third regulated voltage V MLS3 The third switch 1043 is located between the two switches. The modulator controller 1020 operates to selectively open or close switches 1041-1043, thereby controlling the output of the modulator.

[0144] Figure 10This is a schematic diagram of an MLS DC-DC converter 1073 according to one embodiment. The MLS DC-DC converter 1073 includes an inductor 1075, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, and a sixth switch S6. The MLS DC-DC converter 1073 also includes control circuitry for opening and closing the switches to provide regulation. Figure 10 (Not shown in the image).

[0145] Figure 10 The MLS DC-DC converter 1073 illustrates an implementation of an MLS DC-DC converter suitable for incorporation into a multi-stage envelope tracker. However, other implementations of the MLS DC-DC converter may be included in a multi-stage envelope tracker implemented according to the teachings herein.

[0146] In the illustrated embodiment, the first switch S1 includes a component electrically connected to the battery voltage V. BATT The first terminal is electrically connected to the first terminal of the second switch S2 and the second terminal of the first terminal of the inductor 1075. The second switch S2 also includes a first or ground power supply V. GND The second end. Although Figure 10 The illustration shows a configuration of a DC-DC converter powered using ground and battery voltage, but the teachings herein apply to DC-DC converters powered using any suitable power source. Inductor 1075 also includes a second terminal electrically connected to the first terminal of each of the third through sixth switches S3-S6. The third switch S3 also includes an electrical connection to ground power supply V. GND The second terminal. Each of the fourth, fifth, and sixth switches S4-S6 includes a component configured to generate the first, second, and third regulated voltages V, respectively. MLS1 V MLS2 and V MLS3 The second end.

[0147] The first to sixth switches S1-S6 are selectively opened or closed to maintain the regulated voltage within a specific error tolerance of the target voltage level. Although an example with three regulated voltages is shown, the MLS DC-DC converter 1073 can be implemented to produce more or fewer regulated voltages.

[0148] In the illustrated embodiment, the MLS DC-DC converter 1073 operates as a buck-boost converter, operable to generate a voltage greater than the battery voltage V. BATT Adjust the boost voltage and / or lower it than the battery voltage V BATT The step-down voltage can be adjusted. However, other implementations are also possible.

[0149] Figure 11This is a schematic diagram illustrating an example of timing for MLS DC-DC conversion. As shown in Figure 11, the width of the regulation period can be used to control the voltage level of the regulated voltage generated by the MLS DC-DC conversion. For example, one MLS regulated voltage can be associated with period t1, while a second regulated voltage can be associated with a different period t2. Furthermore, the non-overlapping period tovlp can be used to avoid crossbar current between different voltage levels.

[0150] In some embodiments herein, one or more adjustment periods (e.g., t1 and / or t2) and / or one or more non-overlapping periods (e.g., tovlop) are digitally controllable. In some embodiments, the delay is controlled based on a digital state machine and / or other suitable circuitry.

[0151] The regulated voltage generated by the MLS DC-DC converter can be selectively supplied to the modulator output filter by the modulator. In the example shown, the modulator output filter is depicted as including parallel capacitors C1 and C2 and series inductors L1 and L2. However, other implementations of the modulator output filter are also possible.

[0152] Providing an AC path through the modulator output filter and a separate DC path bypassing the modulator offers improved efficiency. For example, by implementing an envelope tracking system in this way, the energy accumulated in the inductors (e.g., inductors L1 and / or L2) of the modulator's output filter can be reduced. This energy reduction, in turn, reduces overshoot entering the filter and / or reverse cross current entering the MLS switch.

[0153] In one embodiment, the MLS DC-DC converter generates two or more MLS voltages for a modulator that controls the power amplifier supply voltage, and generates a DC voltage that controls the power amplifier supply voltage via a DC path bypassing the modulator. Furthermore, the regulation of the DC voltage differs from the regulation of the MLS voltage. For example, the regulation period and / or non-overlapping period used for regulation may differ for the DC voltage relative to the MLS voltage. Therefore, the pulse width modulator (PWM) sequence for the DC path may differ from that of the AC path.

[0154] Figure 12 This is a schematic diagram illustrating an example of MLS envelope tracking for continuous wave signals. The example shown is for a continuous wave signal with a frequency of approximately 100 MHz and a corresponding period of approximately 10 ns. An example of the MLS voltage level applicable to the signal is shown.

[0155] Figure 13This is a schematic diagram illustrating an example of envelope frequency distribution for various signal waveforms. For each type of signal waveform, the graph depicts the percentage of DC envelope energy, AC envelope energy less than 1 MHz, and AC envelope energy greater than 1 MHz. Providing both an AC path through the modulator output filter and a separate DC path bypassing the modulator offers improved efficiency for various types of RF signal waveforms.

[0156] in conclusion

[0157] The embodiments described above have provided examples relevant to mobile devices. However, the principles and advantages of these embodiments can be applied to any other system or device that requires envelope tracking.

[0158] Unless the context explicitly requires otherwise, throughout the specification and claims, the terms “comprising,” “including,” etc., shall be interpreted in an inclusive rather than exclusive or exhaustive sense; that is, in the sense of “including but not limited to.” As generally used herein, the term “coupled” refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Similarly, as generally used herein, the term “connected” refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Furthermore, when used in this application, the terms “here,” “above,” “below,” and similar terms shall refer to the entire application and not to any particular part of it. Where the context permits, singular or plural terms used in the foregoing details may also include the plural or singular, respectively. The term “or” refers to a list of two or more items, and this term encompasses all of the following interpretations of the term: any item in the list, all items in the list, and any combination of items in the list.

[0159] Furthermore, the conditional language used herein, such as “may,” “can,” “possibly,” “possibly,” “e.g.,” “for example,” “such as,” etc., unless otherwise specifically stated or otherwise understood as in the context in which they are used, is generally intended to convey that certain embodiments include certain features, elements, and / or states, while other embodiments do not. Therefore, such conditional language is not generally intended to imply that features, elements, and / or states are necessary in any way for one or more embodiments, or that one or more embodiments necessarily include logic for determining, with or without author input or prompting, whether such features, elements, and / or states are included or will be performed in any particular embodiment.

[0160] The foregoing detailed description of various embodiments of the present invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed above. Although specific embodiments and examples of the invention have been described above for illustrative purposes, those skilled in the art will recognize that various equivalent modifications can be made within the scope of the invention. For example, while processes or block diagrams are presented in a given order, alternative embodiments may execute routines with steps, or employ systems with block diagrams in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these processes or block diagrams can be implemented in various different ways. Furthermore, while processes or block diagrams are sometimes shown as being executed sequentially, these processes or block diagrams may alternatively be executed in parallel, or may be executed at different times.

[0161] The teachings of this invention provided herein can be applied to other systems, not necessarily those described above. Elements and actions of the various embodiments described above can be combined to provide further embodiments.

[0162] While certain embodiments of the invention have been described, these embodiments are presented by way of example only and are not intended to limit the scope of this disclosure. In fact, the novel methods and systems described herein may be embodied in many other forms; furthermore, various omissions, substitutions, and changes may be made to the form of the methods and systems described herein without departing from the spirit of this disclosure. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and spirit of this disclosure.

Claims

1. An envelope tracking system, comprising: A power amplifier configured to amplify radio frequency signals and receive power from the power amplifier supply voltage; and An envelope tracker configured to generate the power amplifier supply voltage based on an envelope signal corresponding to the envelope of the radio frequency signal, the envelope tracker comprising: a DC-DC converter configured to output a plurality of regulated voltages; a modulator configured to generate a modulator output voltage based on the plurality of regulated voltages and the envelope signal; a first filter coupled between the modulator output voltage and the power amplifier supply voltage; a second filter coupled between the DC voltage and the power amplifier supply voltage; and a controllable delay circuit configured to control the relative delay between an AC path through the first filter and a DC path through the second filter.

2. The envelope tracking system as described in claim 1, wherein, The DC-DC converter is also configured to generate the DC voltage.

3. The envelope tracking system as described in claim 1, wherein, Each of the plurality of regulated voltages has a different voltage level.

4. The envelope tracking system as described in claim 1, wherein, The modulator includes a plurality of switches, each switch being coupled between the modulator output voltage and a corresponding one of the plurality of regulated voltages.

5. The envelope tracking system as described in claim 1, wherein, The first filter includes at least one series inductor and at least one parallel capacitor.

6. The envelope tracking system as described in claim 5, wherein, The first filter also includes a DC blocking capacitor connected in series between the modulator output voltage and the power amplifier supply voltage.

7. The envelope tracking system as described in claim 1, wherein, The second filter includes at least one series inductor and at least one parallel capacitor.

8. The envelope tracking system as described in claim 1, wherein, The controllable delay circuit includes a plurality of controllable delay buffers, each of which is configured to control the delay of a corresponding one of the plurality of regulated voltages.

9. The envelope tracking system as described in claim 1, wherein, The DC path through the second filter carries at least 75 percent of the energy supplied from the envelope tracker to the power amplifier.

10. A mobile device, comprising: A transceiver configured to generate radio frequency transmit signals; The front-end circuitry includes a power amplifier configured to amplify the radio frequency transmitted signal and receive power from the power amplifier supply voltage; and A power management circuit includes an envelope tracker configured to generate a power amplifier supply voltage based on an envelope signal corresponding to the envelope of the radio frequency transmitted signal. The envelope tracker includes: a DC-DC converter configured to output a plurality of regulated voltages; a modulator configured to generate a modulator output voltage based on the plurality of regulated voltages and the envelope signal; a first filter coupled between the modulator output voltage and the power amplifier supply voltage; a second filter coupled between the DC voltage and the power amplifier supply voltage; and a controllable delay circuit configured to control the relative delay between an AC path through the first filter and a DC path through the second filter.

11. The mobile device of claim 10, wherein, The DC-DC converter is also configured to generate the DC voltage.

12. The mobile device of claim 10, further comprising a battery providing a battery voltage, the DC-DC converter being configured to generate the plurality of regulated voltages and the DC voltage based on a DC-DC conversion providing the battery voltage.

13. The mobile device of claim 10, wherein, The first filter includes at least one series inductor, at least one parallel capacitor, and a DC blocking capacitor connected in series between the modulator output voltage and the power amplifier supply voltage.

14. The mobile device of claim 10, wherein, The controllable delay circuit includes a plurality of controllable delay buffers, each of which is configured to control the delay of a corresponding one of the plurality of regulated voltages.

15. An envelope tracking method, the method comprising: Use a power amplifier to amplify the radio frequency signal; The power amplifier is powered using the power amplifier supply voltage; Outputs multiple regulated voltages from a DC-DC converter; Based on the plurality of adjusted voltages and envelope signals, a modulator output voltage is generated using a modulator, wherein the envelope signals correspond to the envelope of the radio frequency signal; The power amplifier supply voltage is controlled using a first filter between the modulator output voltage and the power amplifier supply voltage. The power amplifier supply voltage is controlled using a second filter between the DC voltage and the power amplifier supply voltage; and A controllable delay circuit is used to control the relative delay between the AC path through the first filter and the DC path through the second filter.

16. The method of claim 15, further comprising using the DC-DC converter to generate the DC voltage.

17. The method of claim 15, further comprising using a series DC blocking capacitor of the first filter to provide DC blocking.

Images