System and method for adjusting amplifier bias using envelope tracking - Patents.com

Abstract

A system and method comprising: receiving an input signal; and providing an output signal in response to the input signal by an amplifier circuit (1308), the output signal having an envelope. An envelope detection signal corresponding to the envelope of the output signal is generated. A bias current provided to the amplifier circuit (1308) is adjusted based on the envelope detection signal. The amplifier circuit (1308) includes an amplifier and a transformer (L1, L2), the transformer (L1, L2) configured to establish a magnetic coupling feedback loop from an output of the amplifier to an input of the amplifier.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of International Patent Application No. PCT / US2022 / 015863, filed February 9, 2022, and U.S. patent application Ser. No. 17 / 735,358, filed May 3, 2022, which is a continuation-in-part of U.S. patent application Ser. No. 17 / 668,298, filed February 9, 2022, and entitled “SYSTEM AND METHOD FOR ADJUSTING AMPLIFIER BIAS CURRENT BASED ON INPUT SIGNAL ENVELOPE TRACKING,” which was filed February 9, 2021, and which is a continuation-in-part of U.S. patent application Ser. No. 17 / 668,298, filed February 9, 2021, and entitled “SYSTEM AND METHOD FOR ADJUSTING AMPLIFIER BIAS CURRENT BASED ON INPUT SIGNAL ENVELOPE TRACKING.” This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 147,668, entitled "METHOD FOR COMPONENT TRACKING," the disclosure of which is incorporated herein by reference in its entirety for all purposes.This application is a continuation of U.S. patent application Ser. No. 17 / 486,297, filed on September 27, 2021, entitled “AMPLIFIER LINEARIZATION USING MAGNETICALLY COUPLED FEEDBACK,” U.S. patent application Ser. No. 17 / 486,417, filed on September 27, 2021, entitled “METHOD OF IMPROVING LINEARITY OF AMPLIFIER CIRCUIT INCLUDING MAGNETICALLY COUPLED FEEDBACK LOOP BY INCREASING DC BIAS CURRENT WITHOUT IMPACTING AMPLIFIER GAIN,” U.S. patent application Ser. No. 17 / 486,517, filed on September 27, 2021, entitled “AMPLIFIER LINEARIZATION USING MAGNETICALLY COUPLED FEEDBACK LOOP BY INCREASING DC BIAS CURRENT WITHOUT IMPACTING AMPLIFIER GAIN,” and U.S. patent application Ser. No. 17 / 486,517, filed on September 27, 2021, entitled “METHOD OF IMPROVING LINEARITY OF AMPLIFIER CIRCUIT INCLUDING MAGNETICALLY COUPLED FEEDBACK LOOP BY INCREASING DC BIAS CURRENT WITHOUT IMPACTING AMPLIFIER GAIN.” No. 17 / 486,339, entitled "DIFFERENTIAL AMPLIFIER INCLUDING DUAL MAGNETICALLY COUPLED FEEDBACK LOOP," filed on September 27, 2021, U.S. patent application Ser. No. 17 / 486,367, entitled "DIFFERENTIAL AMPLIFIER INCLUDING DUAL MAGNETICALLY COUPLED FEEDBACK LOOPS," and U.S. patent application Ser. No. 17 / 486,386, entitled "AMPLIFIER INCLUDING MAGNETICALLY COUPLED FEEDBACK LOOP AND STACKED INPUT AND OUTPUT STAGES ADAPTED FOR DC CURRENT REUSE," filed on September 27, 2021, the disclosures of which are incorporated herein by reference in their entireties for all purposes.

[0002] Field This disclosure relates generally to power amplifier design and techniques for radio frequency operation. [Background technology]

[0003] background

[0003] Power amplifiers (PAs) for radio frequency (RF) operation are designed to amplify low input power of an RF signal to generate a higher power level of RF output by converting DC power from a DC power source into RF energy. The PA of a typical transmitter system is biased with a high DC voltage, thereby dissipating heat generated during operation. Therefore, design considerations for a PA include schemes for achieving an appropriate level of efficiency to minimize DC power consumption and to reduce heat dissipation.

[0004]

[0004] In state-of-the-art wireless communication technology, various wireless standards aimed at high communication throughput utilize complex modulation schemes by manipulating amplitude and / or phase components to generate RF signals. Examples of such modulation schemes include quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK). Such modulation may impose stringent linearity requirements on the PA in the system. The linearity of a PA is simply shown in a plot of output power as a function of input power, where the slope of the line is equal to the gain of the PA. Linearity is particularly important for systems that transmit large amplitude carrier signals with QAM or QPSK. For example, QAM for orthogonal frequency division multiple access (OFDMA) or code division multiple access (CDMA) generates RF signals with high peak-to-average power ratios (PAPR). In such high PAPR scenarios, the PA of the transmit chain often needs to be set to output a power lower than the peak output power until the linearity requirement is just met. This operation is called "power back-off". Without power back-off, the output RF signal will be distorted at high output PAPR points. The signal waveform can be restored by power back-off operation, which reduces the peak output power level. As a result, the overall efficiency will be significantly reduced, especially if the PA is designed to achieve maximum efficiency at the maximum power level. Therefore, it is difficult to achieve linearity and good efficiency simultaneously.

[0005]

[0005] In RF PA technology, power added efficiency (PAE) is defined as the ratio of the difference between the output power and the input power to the total DC power consumed, and efficiency is defined as the ratio of the output power to the input DC power. In a conventional transmitter system, a constant DC power is provided to maintain a given power level, whereby extra energy is wasted when the signal swings downward to a lower power level. One example of a known technique for improving efficiency is envelope tracking (ET), in which the power supply voltage applied to the RF PA is continuously adjusted to provide the DC power required at each time by tracking the envelope of the input signal. The envelope information is obtained from an IQ modem and passed to an envelope tracking power supply to provide the required voltage.

[0006]

[0006] Regarding linearity considerations, various PA linearization techniques have been devised, which usually involve comparing the amplitude and / or phase of the RF signal envelope at the output with that at the input in order to apply appropriate corrections by a feedback loop. Examples of conventional linearization techniques in PA architectures include feed-forward error correction, digital pre-distortion, envelope elimination and restoration, etc. Many of these linearization techniques in PA architectures are well known, and details can be found in various textbooks, scientific articles, and white papers. Summary of the Invention [Means for solving the problem]

[0007] overview

[0007] Disclosed herein are systems and methods for improving amplifier efficiency using envelope tracking (ET) techniques. In one aspect of the disclosed method, a bias current supplied to an amplifier having magnetically coupled feedback is continuously adjusted to supply the DC power required at each instant in time by tracking the envelope of an input signal applied to the amplifier.

[0008] In one aspect, a disclosed method includes receiving an input signal having an envelope and generating an envelope detection signal corresponding to the envelope. The method further includes adjusting a bias current provided to an amplification circuit based on the envelope detection signal, the amplification circuit including an amplifier and a transformer. The transformer is configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier. An output signal is provided by the amplification circuit in response to the input signal.

[0009]

[0009] The present disclosure is also directed to a system including an envelope detector configured to generate an envelope detection signal corresponding to an envelope of an input signal. An amplification circuit is coupled to the envelope detector and configured to provide an output signal in response to the input signal. The amplification circuit includes an amplifier and a transformer. The transformer is configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier. During operation of the system, a bias current provided to the amplification circuit is adjusted based on the envelope detection signal.

[0010]

[0010] Also disclosed herein is a method including receiving an input signal and providing, by an amplifier circuit, an output signal in response to the input signal. The output signal has an envelope, and the amplifier circuit includes an amplifier and a transformer. The transformer is configured to establish a magnetic coupling feedback loop from an output of the amplifier to an input of the amplifier. The method further includes generating an envelope detection signal corresponding to the envelope of the output signal. Based on the envelope detection signal, a bias current provided to the amplifier circuit is adjusted.

[0011]

[0011] In another aspect, the present disclosure relates to a system including an amplifier circuit configured to provide an output signal having an envelope in response to an input signal. The amplifier circuit includes an amplifier and a transformer, the transformer configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier. The envelope detector is configured to generate an envelope detection signal corresponding to an envelope of the output signal, such that a bias current provided to the amplifier circuit is adjusted based on the envelope detection signal.

[0012]

[0012] The present disclosure also relates to a method including receiving an input signal having an envelope and generating an envelope detection signal corresponding to the envelope. A bias current provided to an amplifier circuit is adjusted based on the envelope detection signal, the amplifier circuit including an amplifier and a transformer. The transformer is configured to establish a magnetic coupling feedback loop from an output of the amplifier to an input of the amplifier. The amplifier includes a gate terminal, and the transformer includes a primary winding coupled to the output of the amplifier and a secondary winding coupled to the gate terminal. Adjusting the bias current further includes providing a control voltage corresponding to the envelope detection signal to the secondary winding to set an input voltage at the gate terminal. The output signal is provided by the amplifier circuit in response to the input signal.

[0013]

[0013] In another aspect, the present disclosure is directed to a system including an envelope detector configured to generate an envelope detection signal corresponding to an envelope of an input signal. An amplifier circuit is coupled to the envelope detector and configured to provide an output signal in response to the input signal, the amplifier circuit including an amplifier and a transformer, the transformer configured to establish a magnetic coupling feedback loop from an output of the amplifier to an input of the amplifier. The amplifier also includes a gate terminal, the transformer including a primary winding coupled to the output of the amplifier and a secondary winding coupled to the gate terminal. The envelope detector generates a control voltage corresponding to the envelope detection signal. The control voltage is applied to the secondary winding such that a bias current provided to the amplifier circuit is adjusted based on the envelope detection signal.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when considered in conjunction with the drawings in which like reference characters identify correspondingly throughout. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a circuit-level diagram of a single-ended version of a CMOS-based implementation of the amplifier system. [Diagram 2]

[0016] FIG. 1 is a functional block diagram illustrating a current-mode envelope tracking amplifier system according to an embodiment. [Diagram 3]

[0017] FIG. 1 is a circuit-level diagram illustrating an example of a current-mode envelope tracking amplifier system in accordance with an embodiment. [Figure 4]

[0018] The output signal spectrum (dBm vs. frequency) with and without envelope tracking is shown in the right and left graphs, respectively. [Diagram 5]

[0019] With current mode envelope tracking enabled, output voltage versus time is shown in the top graph, and supply current versus time in the bottom graph. [Figure 6]

[0020] FIG. 1 is a simplified block diagram illustrating a first example of a conventional envelope tracking system. [Figure 7]

[0021] FIG. 2 is a simplified block diagram illustrating a second example of a conventional envelope tracking system. [Figure 8]

[0022] FIG. 1 is a block diagram showing a basic configuration of an envelope detector system. [Figure 9]

[0023] FIG. 1 is a circuit level diagram of a conventional diode detector. [Figure 10]

[0024] FIG. 1 is a simplified circuit-level diagram of an implementation that allows direct control of amplifier power supply current based on the output of an envelope detection circuit. [Figure 11]

[0025] FIG. 1 is a circuit-level diagram illustrating an example of a current-mode envelope tracking amplifier system that varies the amplifier bias current by controlling the gate voltage of a transistor. [Figure 12]

[0026] FIG. 1 is a functional block diagram illustrating a current-mode envelope tracking amplifier system according to an embodiment. [Figure 13]

[0027] FIG. 2 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system according to another embodiment. [Figure 14]

[0028] FIG. 13 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system according to yet another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Detailed Description

[0029] Disclosed herein are systems and methods for improving amplifier efficiency using a current-based envelope tracking (ET) technique. As described below, in embodiments of the disclosed method, the bias current supplied to an amplifier having magnetically coupled feedback is continuously adjusted to supply the DC power required at each instant in time by tracking the envelope of an input signal applied to the amplifier or an output signal generated by the amplifier.

[0017]

[0030] Attention is now directed to Figure 1, which is a circuit-level diagram of a single-ended version of a CMOS-based implementation of an amplifier system 100 in which the current-based ET technique may be utilized. The amplifier system 100 includes an amplifier circuit comprised of a power amplifier (PA) 102 and a transformer 104. As shown, the amplifier circuit's transformer 104 has an output load impedance R L The system 100 is coupled to a load arrangement 108 having a resonant circuit (R p , L o , C o etc.)

[0018]

[0031] As can be appreciated from the following description, the topology of amplifier system 100 paves the way for utilizing bias (power) current provided to the amplifier circuit for envelope tracking. Amplifier system 100 is also described in commonly owned U.S. Provisional Patent Application No. 63 / 084,497, filed Sep. 28, 2020, which discloses an amplifier linearization technique using magnetically coupled feedback, and is incorporated herein by reference.

[0019]

[0032] 1, the transformer 104 has a primary winding L1 connected in series with the output of the PA 102, and a secondary winding L2 coupled to the input of the PA 102. The primary winding L1 and secondary winding L2 are arranged such that a portion of the magnetic field generated by the primary winding L1 is coupled to the secondary winding L2 by a magnetic coupling feedback loop, thereby providing feedback from the output to the input of the PA 102.

[0020]

[0033] The PA 102 comprises transistors M1 and M2 in a cascode arrangement, which are powered by a supply voltage VDD that provides a supply current IDD to the drains of the transistors M1 and M2 through a primary winding L1 of a transformer 104. The input signal is supplied by a current source i s The transistor M1 receives the input voltage v at its gate. in Let g be the mutual conductance of M1. m The input current i s The output current i resulting from o is provided via a primary winding L1 of a transformer 104.

[0021]

[0034] It should be noted that the circuit shown in FIG. 1 is only one example among many possible circuits that can be configured to realize the present amplifier system with magnetically coupled feedback according to an embodiment. Although the transistors M1 and M2 in FIG. 1 are shown to be field effect transistors (FETs), bipolar junction transistors (BJTs) and other types of transistors may alternatively be used to form the PA 102. As known to those skilled in the art, when the amplifier transistors are realized using BJTs, the gate, drain, and source terminals are replaced with base, collector, and emitter terminals, and the base current controls the BJT. Furthermore, while the circuit shown in FIG. 1 is an exemplary implementation based on silicon CMOS, other semiconductor fabrication technologies, such as pHEMT and HBT, may also be utilized.

[0022]

[0035] One particular technical feature associated with amplifier system 100 is that the gain of amplifier system 100 is substantially independent of the inherent gain characteristic of the cascode configuration. m (the transconductance of M1). In general, g m is highly dependent on temperature, bias current, semiconductor manufacturing technology, loading effects, and supply voltage variations. m The independency from , means that the gain of amplifier system 100 is substantially independent, particularly from bias (power supply) current. Thus, amplifier system 100, in accordance with the present disclosure, paves the way for manipulating power supply current without affecting gain.

[0023]

[0036] 2 is a functional block diagram illustrating a current-mode envelope tracking amplifier system 200 according to an embodiment. The envelope tracking loop comprises an envelope detector system 202 configured to detect the envelope of an input signal at the input of an amplifier system with magnetically coupled feedback 204 and vary a power supply current according to information related to the detected envelope. Specifically, the power supply current to the amplifier system 204 varies in time to track the envelope of the input signal so as to provide optimal DC power to the amplifier system 204 at each instant in time. This variation in DC power supply in time reduces the energy wasted under a constant DC power supply, thereby reducing heat dissipation and improving the efficiency and PAE of the amplifier.

[0024]

[0037] 3 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system 300 according to an embodiment. As shown, the current mode envelope tracking system 300 is comprised of an envelope detector system 304 and an amplifier system 308 with magnetically coupled feedback, which may be substantially similar or identical to the amplifier system 100 of FIG. 1. The envelope detector system 304 detects a current source i s During operation of the amplifier system 308, the input signal (i s In response to the output current i o is generated. The output current i o is applied to the load R at the output 320 of the amplifier system 308. L This results in an output voltage being generated across

[0025]

[0038] The implementation and simulation of the present envelope tracking amplifier system has been carried out for both differential and single-ended versions. As an example, an 80 MHz wide 1 GHz OFDM modulated signal with 255 subcarriers is used as the input signal. Figure 4 shows the output signal spectrum (dBm vs. frequency) with and without envelope tracking in the right and left graphs, respectively. As can be seen from this comparison, the output signal spectrum is not affected by the present current mode envelope tracking scheme, and therefore the original gain and linearity are also substantially unaffected. This is because, as mentioned above, the gain of the amplifier system with magnetic coupling feedback is substantially independent of the bias (power supply) current.

[0026]

[0039] Figure 5 shows the output voltage vs. time with current mode envelope tracking enabled in the top graph and the supply current vs. time in the bottom graph. As can be seen, both the output voltage and the supply current vary with substantially the same envelope as the input signal. Because the supply current varies to track the envelope, the wasted DC power is reduced and the PAE increases from 30% to 56% in some cases. High frequency ripple on the envelope can be eliminated by optimizing the filters in the system.

[0027]

[0040] Generally, the carrier signal of an RF system before being upconverted to an RF frequency can be seen in the envelope of the modulated RF signal. Since the amplifier system including the PA amplifies the modulated RF signal, the same envelope can be observed at both the input and output voltages of the amplifier system. The present envelope tracking system is configured to detect the envelope of the modulated RF signal just output from the modulator at the input of the amplifier system. Thus, the present current mode tracking loop can be implemented on-chip with the amplifier system without the need to use a separate chip, thereby reducing complexity and cost. Furthermore, the present current mode envelope tracking is configured to function independently of the modulator (e.g., IQ modem), thereby enabling a self-contained and compact amplifier package.

[0028]

[0041] As mentioned above, various conventional techniques for envelope tracking have been utilized to improve efficiency / PAE in various communication systems. In these conventional systems, the power supply voltage applied to the RF PA is continuously adjusted to provide the DC power required at each instant by tracking the envelope of the input signal. The envelope information is usually obtained from an IQ modem and passed to an envelope tracking power supply to provide the required power supply voltage.

[0029]

[0042] FIG. 6 is a simplified block diagram showing a first example of a conventional envelope tracking system 400. The signals are originally in digital form and arrive at the modulator 402 as I (in-phase) or Q (quadrature) signals. In the modulator 402, each of the I and Q signals is separately applied to a digital-to-analog converter, a low-pass filter, and then passed to a mixer to be mixed with a local oscillator signal to convert to the required frequency (details are omitted, but in FIG. 6, it is shown by a dashed path). The two types of signals are then summed at 404 to generate an RF signal, which is then passed to an amplifier chain with a PA 406. For the purpose of envelope tracking, a delay line 408 is included at the early stage of the modulator 402, from which a signal for envelope shaping is provided and passed to an envelope shaping signal generation block 410. Block 410 comprises several elements for controlling the envelope tracking power supply 412 to change the supply voltage to the PA 406 according to envelope information obtained from the I and Q signals by the following calculation:

number

[0030]

[0043] The above envelope tracking scheme involves interaction with a modulator 402, e.g., an IQ modem. In contrast, the current-mode envelope tracking amplifier system embodiment of the present disclosure is configured to detect the RF input signal at the input of the amplifier system to obtain the envelope information, instead of interacting with a preceding modulator in the transmit chain. Thus, the present scheme of current-mode envelope tracking results in a system architecture with significantly reduced complexity. It should be noted that the present envelope tracking scheme can also use a centrally generated envelope signal.

[0031]

[0044] 7 is a simplified block diagram illustrating a second example of a conventional envelope tracking system 500. Unlike the first example of a conventional envelope tracking system described above, in system 500, a modulated input signal is detected at the input of PA 502. The supply voltage for PA 502 is adjusted as the envelope of the modulated input signal changes. The input signal power at each time point is detected in block 504 and passed through a shaping function in block 508 to determine the corresponding supply voltage. The shaping table is configured to operate PA 502 at constant gain, constant gain compression, or near the maximum efficiency point as the input power changes.

[0032]

[0045] In contrast, as described above, embodiments of the current-mode envelope tracking amplifier system are configured to vary the supply current, rather than the supply voltage, according to the envelope information. Furthermore, no shaping process is required in this case, since linearity and constant gain behavior are inherently established by the magnetically coupled feedback, which makes the gain substantially independent of the supply current. As a result, high efficiency is achieved with a relatively simple envelope tracking architecture.

[0033]

[0046] 8, a block diagram is provided illustrating a basic configuration of the envelope detector system 202. As shown, the envelope detector system 202 includes an envelope detector circuit 250 and an interface circuit 260. The envelope detector circuit 250 detects an input signal current, e.g., i s The outputted envelope information can then be passed to the interface circuit 260 for optimal processing to vary the power supply current, e.g., IDD in FIG. 3. In this way, the interface circuit 260 can be tailored to various specifications of the application and the overall system (e.g., power levels, transistor types, electrical / magnetic interference levels, filtering needs, etc.). Alternatively, the interface circuit 260 may be omitted if the envelope information outputted from the envelope detection circuit 250 can be directly utilized.

[0034]

[0047] Many envelope detection techniques are known and details can be found in various textbooks, scientific articles, and white papers. Figure 9 shows a circuit level diagram of a so-called diode detector, which is one of many simple envelope detection circuits. The diode detector includes a diode D that rectifies the input signal, thereby allowing current to flow in only one direction, and a capacitor C that provides filtering to remove high frequency ripple in the rectified signal and discharges it through a resistor Z, thereby generating an output voltage Vo(t) that has a time variation corresponding to the envelope of the input signal.

[0035]

[0048] The above diode detector is simple to implement. However, using the output voltage Vo(t) to vary the power supply current requires additional circuitry such as amplifiers, thereby necessitating a complex interface circuit 260 that includes such amplifiers.

[0036]

[0049] Figure 10 is a simplified circuit-level diagram of an example system 1000 that enables direct control of a power supply current IDD to an amplifier 1004 based on the output of an envelope detection circuit 1010. In the embodiment of Figure 10, the amplifier 1004 may be included in an amplifier system implemented substantially identically to the amplifier system 100 with magnetically coupled feedback shown in Figure 1. For clarity, Figure 10 shows only a portion of such an amplifier system, namely, the amplifier 1004 and the path of the power supply current IDD through transistors M1 and M2 of the amplifier 1004.

[0037]

[0050] The envelope detection circuit 1010 is configured as a CMOS version of a known envelope detector. The detection circuit 1010 includes two NMOS devices N1 and N2 coupled in a differential configuration to rectify an input signal. The rectified signal appears at a node to which the sources of the NMOS devices are connected. A capacitor C L provides filtering to remove high frequency ripple in the rectified signal, and the quiescent current I Qis derived for proper operation of the circuit. The envelope detection circuit 1010 outputs an output voltage Vo at a detector output node 1012 having a time variation corresponding to the envelope of the input signal. The output node 1012 of the envelope detection circuit 1010 is coupled through an interface circuit 1020 to a control node 1014 that sets the gate voltage of the transistor M1 in the amplifier 1004, thereby controlling the power supply current IDD. Since the voltage of the control node 1014 (i.e., the gate voltage of the transistor M1) also varies in time based on the envelope of the input signal, it can be seen that the present implementation is configured to directly make the power supply current IDD track the envelope of the input signal. In the particular example of FIG. 10, the interface circuit 1020 includes a low pass filter to further filter out high frequency components in the envelope, thereby increasing the accuracy of the envelope information for IDD control. In some embodiments, various peripheral components (not shown) may be further included in the interface circuit 1020 for fine tuning.

[0038]

[0051] As mentioned above, the implementation of the present envelope tracking scheme can be made for various circuit topologies related to amplifier systems with both differential and single-ended versions, as well as magnetically coupled feedback, in accordance with the disclosure of the aforementioned U.S. Provisional Patent Application No. 63 / 084,497. The exemplary implementation shown in FIG. 10 includes a low pass filter as a major component of the interface circuit 1020. However, the interface circuit 1020 can be modified as necessary to optimize the performance of the overall system 1000 depending on the application and various specifications, such as power levels, transistor types, electrical / magnetic interference levels, filtering needs, etc.

[0039]

[0052] 11 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system 1100 that varies the amplifier bias current by controlling the gate voltage of a transistor. As shown, the current mode envelope tracking system 1100 is comprised of an envelope detector system 1104 and an amplifier system with magnetically coupled feedback 1108, which may be substantially similar or identical to the amplifier system 100 of FIG. 1. The envelope detector system 1104 detects a current source i s During operation of the amplifier system 1108, the input signal (i s In response to the output current i o is generated. The output current i o is applied to the load R at the output 1120 of the amplifier system 1108. L This results in an output voltage being generated across

[0040]

[0053] To vary the supply current IDD to track the envelope, the envelope detector system 1104 sets the gate voltage of transistor M1 in the amplifier system 1108, thereby controlling the supply current IDD. More specifically, the gate voltage of M1 is controlled by the output voltage from the detector system 1104. This output voltage from the detector system 1104 is fed to the gate of M1 at the ground side of L2. This approach is very simple in a differential implementation, since the ground side of L2 is a virtual ground whose DC level is the same as the gate voltage of M1.

[0041]

[0054] 12 is a functional block diagram illustrating a current-mode envelope tracking amplifier system 1200 according to an embodiment. The envelope tracking loop comprises an envelope detector system 1202 configured to detect the envelope of an output signal generated by an amplifier system 1204 with magnetically coupled feedback. The detector system 1202 operates to vary a power supply current to the amplifier system 1204 according to information related to the detected envelope of the output signal. Specifically, the power supply current to the amplifier system 1204 varies in time to track the envelope of the output signal in order to provide optimal DC power to the amplifier system 1204 at each point in time. This variation in DC power supply in time reduces the energy wasted under a constant DC power supply, thereby reducing heat dissipation and improving the efficiency and PAE of the amplifier.

[0042]

[0055] 13 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system 1300 according to an embodiment. As shown, the current mode envelope tracking system 1300 is comprised of an envelope detector system 1304 and an amplifier system with magnetically coupled feedback 1308, which may be substantially similar or identical to the amplifier system 100 of FIG. 1. The envelope detector system 1304 detects the envelope of the output signal at the output 1320 of the amplifier system 1308 and varies the power supply current IDD over time to track the envelope. During operation of the amplifier system 1308, an input signal (i s In response to the input current i o is generated. The output current i o is applied to the load R at the output 1320 of the amplifier system 1308. L This results in an output voltage being generated across

[0043]

[0056] 14 is a circuit level diagram illustrating an example of a current mode envelope tracking amplifier system 1400 in accordance with another embodiment. As shown, the current mode envelope tracking system 1400 is comprised of an envelope detector system 1404 and an amplifier system 1408 with magnetically coupled feedback. The envelope detector system 1404 detects the envelope of the output signal at the output 1420 of the amplifier system 1408. During operation of the amplifier system 1408, an input signal (i s In response to the input current i o is generated. The output current i o is applied to the load R at the output 1420 of the amplifier system 1408. L This results in an output voltage being generated across

[0044]

[0057] To vary the supply current IDD to track the envelope, the envelope detector system 1404 sets the gate voltage of transistor M1 in the amplifier system 1408, thereby controlling the supply current IDD. More specifically, the gate voltage of M1 is controlled by the output voltage from the envelope detector system 1404. This output voltage from the detector system 1404 is provided to the gate of M1 on the ground side of L2. This approach is very simple in a differential implementation, since the ground side of L2 is a virtual ground whose DC level is the same as the gate voltage of M1.

[0045]

[0058] Where the above methodology indicates that certain events occur in a certain order, the ordering of certain events may be modified. Furthermore, some of the events may not only be performed sequentially as described above, but also simultaneously in a parallel process where possible. Accordingly, this specification is intended to cover all such modifications and variations of the disclosed embodiments that fall within the spirit and scope of the appended claims.

[0046]

[0059] In the above description, for purposes of explanation, specific names have been used to provide a thorough understanding of the claimed systems and methods. However, it will be apparent to one skilled in the art that specific details are not required to practice the systems and methods described herein. Thus, the above descriptions of specific embodiments of the described systems and methods are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed, and obviously, many modifications and variations are possible in light of the above teachings. The embodiments have been selected and described in order to best explain the principles of the described systems and methods and their practical applications, so that they will enable those skilled in the art to make the best use of the described systems and methods, as well as various embodiments with various modifications as appropriate for the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the systems and methods described herein.

[0047]

[0060] Also, various inventive concepts may be embodied as one or more methods, examples of which are provided. The acts performed as part of a method may be ordered in any suitable manner. Thus, while the illustrated embodiments show acts as sequential, embodiments may be constructed in which acts are performed in an order different from that shown, and may include performing some acts simultaneously.

[0048]

[0061] All definitions defined and used herein are understood to take precedence over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0049]

[0062] The indefinite articles "a" and "an," as used in the specification and claims, unless clearly indicated to the contrary, shall be understood to mean "at least one."

[0050]

[0063] The term "and / or" as used herein and in the claims shall be understood to mean "either or both" of the elements so conjointly connected, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and / or" shall be interpreted in the same manner, i.e., "one or more" of the elements so conjointly connected. Other elements may optionally be present other than the elements specifically identified by the "and / or" clause, whether related to the elements specifically identified or not. Thus, as a non-limiting example, a reference to "A and / or B", when used in conjunction with open-ended language such as "comprising", may refer in one embodiment to only A (optionally including elements other than B), in another embodiment to only B (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0051]

[0064] As used herein and in the claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be interpreted as being inclusive, i.e., including at least one of the elements or list of elements, but including more than one of the elements or list of elements, and optionally including items not in the further list. Only terms clearly indicating the contrary, such as "only one of," "exactly one of," or, when used in the claims, "consisting of," shall mean including exactly one element of the elements or list of elements. In general, the term "or" as used herein shall be interpreted as indicating exclusive alternatives (i.e., "one or the other, but not both") only when preceded by an exclusive term, such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," as used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0052]

[0065] As used herein and in the claims, the phrase "at least one" in reference to a list of one or more elements shall be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows that elements other than those specifically identified in the list of elements to which the phrase "at least one" refers may optionally be present, whether or not related to the specifically identified elements. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B" or, equivalently, "at least one of A and / or B") may refer in one embodiment to at least one (optionally including more than one) A with no B (and optionally including elements other than B), in another embodiment to at least one (optionally including more than one) B with no A (and optionally including elements other than A), in yet another embodiment to at least one (optionally more than one) A and at least one (optionally more than one) B (and optionally including other elements), etc.

[0053]

[0066] As in the specification above, in the claims, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "composed of," and the like, are to be understood to be open-ended, i.e., to mean including but not limited to. As provided for in the United States Patent Office Manual of Patent Examining Procedures 2111.03, only the transitional phrases "consisting of" and "consisting essentially of" shall be closed-ended or semi-closed-ended transitional phrases, respectively.

Claims

1. receiving an input signal; providing an output signal in response to the input signal by an amplifier circuit, the output signal having an envelope, the amplifier circuit including an amplifier and a transformer, the transformer configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier, the transformer having a primary winding connected in series with the output of the amplifier and a secondary winding coupled to the input of the amplifier; generating an envelope detection signal corresponding to the envelope of the output signal; adjusting a bias current (rather than a power supply voltage) provided to the amplifier circuit based on the envelope detection signal; A method comprising:

2. The generating step comprises: rectifying the output signal to generate a rectified signal; filtering the rectified signal; The method of claim 1 , comprising:

3. The method of claim 1 , wherein the envelope detection signal has a time variation that corresponds to the envelope of the output signal.

4. 2. The method of claim 1, wherein the amplifier includes a transistor having a gate terminal, the transformer includes a primary winding coupled to an output of the amplifier and a secondary winding coupled to the gate terminal, and the adjusting further includes applying a voltage comprising the envelope detection signal to the secondary winding to adjust the bias current based on the envelope detection signal.

5. The method of claim 1 , further comprising setting a loop gain of the magnetically coupled feedback loop by selecting a coupling coefficient and a turns ratio of the transformer.

6. the transformer having a primary winding connected in series with the output of the amplifier and a secondary winding coupled to the input of the amplifier, the primary winding and the secondary winding being arranged such that a portion of the magnetic field generated by the primary winding couples to the secondary winding to establish the magnetic coupling feedback loop; and the method further comprising: the secondary winding providing the output signal to a load configuration including a balun; The method of claim 1 further comprising:

7. 7. The method of claim 6, wherein a loop gain of the magnetic coupling feedback loop is substantially independent of the impedance of the load configuration and is defined at least in part by a coupling coefficient and a turns ratio of the transformer.

8. an amplifier circuit configured to provide an output signal in response to an input signal, the output signal having an envelope, the amplifier circuit including an amplifier and a transformer, the transformer configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier, the transformer having a primary winding connected in series with the output of the amplifier and a secondary winding coupled to the input of the amplifier; an envelope detector configured to generate an envelope detection signal corresponding to the envelope of the output signal; Equipped with A system in which a bias current (rather than a power supply voltage) provided to the amplifier circuit is adjusted based on the envelope detection signal.

9. The system of claim 8 , wherein the envelope detection signal has a time variation that corresponds to the envelope of the output signal.

10. 9. The system of claim 8, wherein the amplifier includes a transistor having a gate terminal, and the transformer includes a primary winding coupled to the output of the amplifier and a secondary winding coupled to the gate terminal, the secondary winding receiving a voltage from the envelope detector corresponding to the envelope detection signal to establish the voltage at the gate terminal, thereby varying the bias current based on the envelope detection signal.

11. The envelope detector one or more first circuit elements that rectify the input signal to generate a rectified signal; one or more second circuit elements for filtering the rectified signal; The system of claim 8 , comprising:

12. 9. The system of claim 8, wherein the transformer is configured with a selected coupling coefficient and turns ratio, and wherein a loop gain of the magnetic coupling feedback loop is set by the selected coupling coefficient and turns ratio.

13. 9. The system of claim 8, wherein the transformer has a primary winding connected in series with the output of the amplifier and a secondary winding coupled to the input of the amplifier, the primary winding and the secondary winding arranged such that a portion of the magnetic field generated by the primary winding couples to the secondary winding to establish the magnetic coupling feedback loop, and the system further includes a load arrangement coupled to the primary winding.

14. 14. The system of claim 13, wherein a loop gain of the magnetic coupling feedback loop is substantially independent of the impedance of a load included in the load configuration and is defined at least in part by a coupling coefficient and a turns ratio of the transformer.

15. 14. The system of claim 13, wherein the amplifier circuit is implemented as an integrated circuit, and the primary winding and the secondary winding are integrated on different metal layers of the integrated circuit.

16. The inductance of the secondary winding (L ２ ) is the resonant frequency (f ０ ) is a parasitic capacitance (C) between the input of the amplifier and ground so that resonance occurs at ｇ 14. The system of claim 13, wherein the system is selected in conjunction with

17. f ０ but, [Equation 1] 17. The system of claim 16, wherein:

18. The system of claim 13 , wherein the load configuration includes a balun connected between the primary winding and a load.

19. 20. The system of claim 18, wherein the primary winding has a first end connected to the output of the amplifier and a second end connected to a first end of the balun.

20. receiving an input signal having an envelope; generating an envelope detection signal corresponding to the envelope of the input signal; adjusting a bias current (rather than a power supply voltage) provided to an amplifier circuit based on the envelope detection signal, the amplifier circuit including an amplifier and a transformer, the transformer configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier, the amplifier including a gate terminal, the transformer including a primary winding coupled to the output of the amplifier and a secondary winding coupled to the gate terminal, the adjusting further including providing a control voltage corresponding to the envelope detection signal to the secondary winding to set an input voltage at the gate terminal; providing an output signal by the amplifier circuit in response to the input signal; A method comprising:

21. an envelope detector configured to generate an envelope detection signal corresponding to an envelope of the input signal; an amplifier circuit coupled to the envelope detector and configured to provide an output signal in response to the input signal, the amplifier circuit including an amplifier and a transformer, the transformer configured to establish a magnetically coupled feedback loop from an output of the amplifier to an input of the amplifier; Including, 1. A system wherein the amplifier includes a gate terminal, the transformer includes a primary winding coupled to an output of the amplifier and a secondary winding coupled to the gate terminal, the envelope detector generates a control voltage corresponding to the envelope detection signal, the control voltage being applied to the secondary winding to adjust a bias current (rather than a power supply voltage) provided to the amplifier circuit based on the envelope detection signal.

Images