Envelope control bias for auxiliary transmitters of Doherty power amplifiers

Abstract

Disclosed are a transmitter and a Doherty power amplifier configured for envelope-controlled biasing of an auxiliary transmitter of the Doherty power amplifier. According to one aspect, a transmitter is provided having a main amplifier in a main signal path and an auxiliary amplifier in an auxiliary signal path. The auxiliary amplifier is configured to be activated only when the envelope of an input signal to the transmitter exceeds a power threshold. The transmitter also includes at least one component in the auxiliary signal path configured to be deactivated when the auxiliary amplifier is deactivated, the at least one component including at least one of a pre-power amplifier, a mixer, and a local oscillator buffer.

Description

Technical Field

[0001] The present invention relates to wireless communications, and more particularly to envelope control biasing of an auxiliary transmitter of a Doherty power amplifier. Background Art

[0002] Many radio systems, such as those compliant with the fourth-generation (4G, also known as Long Term Evolution (LTE)) and fifth-generation (5G, also known as New Radio (NR)) standards promulgated by the Third Generation Partnership Project (3GPP), use modulated signals with high peak-to-average ratios (PAR). This has the disadvantage of lowering overall efficiency at average output power, particularly for the power amplifier. Methods exist to improve overall efficiency when transmitting modulated signals with high PAR. One fundamental approach employed by Doherty power amplifiers (DPAs) is to use load modulation to achieve higher power-added efficiency (PAE) at average output power.

[0003] Figure 1 Figure 1 is a block diagram of a standard DPA 10a. Baseband data, typically in the form of in-phase and quadrature-phase signals (which may be converted from digital to analog by DAC 12), is filtered by filter 14. The filtered baseband data is fed to mixer 16, which mixes it with a local oscillator (LO) signal fed to mixer 16 via LO buffer 18. Mixer 16 provides an upconverted signal to pre-power amplifier (PPA) 20, which amplifies the signal from mixer 16. The amplified upconverted signal is fed to power splitter 22, which splits the amplified upconverted signal into a main path and an auxiliary path. Main amplifier 24 is in the main path, while auxiliary amplifier 26 is in the auxiliary path. The signal input to auxiliary amplifier 26 is phase-shifted by impedance 28a by 90+n*360 degrees (where n is an integer). Phase shifting can be achieved using a λ / 4 transmission line, where λ is the wavelength of the input signal's frequency. The output of main amplifier 24 is also phase-shifted by impedance 28b by 90+m*360 degrees (where m is an integer). This phase-shifted signal is input to auxiliary amplifier 26, which amplifies it. As the auxiliary amplifier amplifies its input signal, it generates load modulation at the output of the main amplifier through the impedance inversion of impedance 28b, which can be a λ / 4 transmission line. The output of auxiliary amplifier 26 is combined with the signal from impedance 28b and fed to load 30.

[0004] like Figure 1 As shown, the standard DPA 10a uses two power amplifiers (PAs) (a main power amplifier and an auxiliary power amplifier) ​​driven by a power splitter and a 90-degree phase shifter for the auxiliary input. A known technique for generating a 90-degree phase shift is to use two mixers, with the phase-shifted local oscillator (LO) signal going to one of the two mixers, such as Figure 2 As shown. Figure 2 In DPA 10b, the filtered baseband signal is split into a main path and a secondary path. In the main path, the filtered baseband signal is mixed with the LO signal from LO buffer 18a by mixer 16a, while in the secondary path, the filtered baseband signal is mixed with the LO signal from LO buffer 18b by mixer 16b. The outputs of mixers 16a and 16b are fed to pre-power amplifiers 20a and 20b, respectively.

[0005] In some cases, Figure 2 The architecture shown is Figure 1 The architecture shown has significant advantages. These include the ability to easily achieve a 90-degree phase shift over a wider frequency range, eliminating routing power losses in the power splitter, and eliminating the need to implement a λ / 4 transmission line that consumes valuable chip area. Another assumption when splitting the mixers 16 and / or pre-power amplifiers (PPAs) 20 is that each mixer 16 and / or PPA 20 only needs to deliver half the output power, thereby enabling each mixer 16 and / or PPA 20 to consume less power.

[0006] Because DPA uses load modulation to track the envelope of the modulated output signal, it is used to improve efficiency as the output power of the transmitted signal decreases. However, even if the envelope decreases, the power consumption of the components before the PA remains unchanged, which reduces the overall efficiency of the transmitter. This is a problem for systems with many antennas, where the output power and efficiency of each PA are low, especially at very high frequencies. Summary of the Invention

[0007] Some embodiments advantageously provide a transmitter and a Doherty amplifier for envelope control biasing of the Doherty power amplifier aiding the transmitter.

[0008] In some embodiments, components preceding the auxiliary amplifier (ie, Figure 2 The power consumption of the auxiliary path (shown) is reduced by turning off these components to achieve low output power. The power consumption of the preceding components in the auxiliary signal path can be reduced by controlling their respective bias levels using, for example, a baseband (BB) envelope signal.

[0009] According to one aspect, a transmitter is provided having a main amplifier in a main signal path and an auxiliary amplifier in an auxiliary signal path. The auxiliary amplifier is configured to be activated only when the envelope of an input signal input to the transmitter exceeds a power threshold included in the transmitter. The transmitter also includes at least one component in the auxiliary signal path configured to be deactivated when the auxiliary amplifier is deactivated, the at least one component including at least one of a pre-power amplifier, a mixer, and a local oscillator buffer.

[0010] According to this aspect, in some embodiments, the transmitter includes a comparator configured to compare the envelope signal with an envelope threshold, and a bias current controller for adjusting the bias current of at least one component to deactivate the at least one component when the envelope signal does not exceed the envelope threshold. In some embodiments, adjusting the bias current includes gradually decreasing or increasing the bias current with respect to the envelope signal. In some embodiments, the transmitter also includes a digital-to-analog converter (DAC) configured to be deactivated when the auxiliary amplifier is turned off. In some embodiments, the DAC is configured to generate the envelope signal. In some embodiments, a mixer in the auxiliary signal path receives an input signal and receives an envelope signal to provide an adaptive bias to control the mixer. In some embodiments, the output of the mixer is input to a pre-power amplifier that also receives the envelope signal. In some embodiments, the transmitter also includes

[0011] A local oscillator buffer configured to receive an envelope signal. In some embodiments, a pre-power amplifier receives the envelope signal, and the envelope signal is used to adjust a gain of the pre-power amplifier, the adjustment tracking the envelope signal. In some embodiments, the pre-power amplifier, the mixer, and the local oscillator buffer are each shut down in response to the envelope signal exceeding a different envelope threshold for each of the pre-power amplifier, the mixer, and the local oscillator buffer.

[0012] According to another aspect, a Doherty amplifier is provided. The Doherty amplifier includes a main amplifier in a main signal path configured to receive an input signal. The Doherty amplifier also includes an auxiliary amplifier in an auxiliary signal path having components including an envelope detector configured to detect an envelope of the input signal to generate an envelope signal, and a mixer configured to mix the input signal with a local oscillator signal, the mixing being based at least in part on an adaptive bias provided by the envelope signal.

[0013] According to this aspect, the envelope detector includes a digital-to-analog converter (DAC). In some embodiments, the mixer is configured to receive an envelope signal to adaptively bias the mixer. In some embodiments, the output of the mixer is input to a preamplifier that also receives the envelope signal. In some embodiments, the component in the auxiliary signal path includes a preamplifier configured to receive the envelope signal, the envelope signal being used to adjust the gain of the preamplifier, the adjustment tracking the envelope signal. In some embodiments, the Doherty amplifier further includes a bias current controller configured to adjust the bias current of at least one component in the auxiliary signal path to deactivate the component in the auxiliary signal path when the envelope signal does not exceed an envelope threshold. In some embodiments, adjusting the bias current includes gradually reducing or increasing the bias current with respect to the envelope signal. In some embodiments, each component in the auxiliary signal path is deactivated separately in response to the envelope signal exceeding a different envelope threshold for each of the components in the auxiliary signal path.

[0014] According to another aspect, a Doherty amplifier includes a filter configured to receive and filter an input signal to be amplified by the Doherty amplifier to generate a filtered input signal; and a splitter circuit to split the filtered input signal into a main signal path and an auxiliary signal path. In the main signal path, a first mixer is configured to mix the filtered input signal with a local oscillator signal to generate a first mixer output signal. A first pre-power amplifier is configured to receive and amplify the first mixer output signal to generate a main amplifier input signal. The Doherty amplifier also includes a main amplifier, and in the auxiliary path, a second mixer is configured to mix the filtered input signal with a local oscillator signal to generate a second mixer output signal, the second mixer being activated and deactivated by the envelope of the input signal. A second pre-power amplifier is configured to receive and amplify the second mixer output signal to generate an auxiliary amplifier input signal, the second pre-power amplifier being activated and deactivated by the envelope of the auxiliary amplifier input signal. The Doherty amplifier also includes an auxiliary amplifier. In some embodiments, the Doherty amplifier further comprises a local oscillator buffer configured to buffer a local oscillator signal, the local oscillator buffer being activated and deactivated by an envelope of the amplifier input signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A more complete understanding of the present embodiments and its attendant advantages and features will be more readily appreciated by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0016] Figure 1 is a block diagram of a known Doherty amplifier within a transmitter;

[0017] Figure 2 is a block diagram of an alternative known Doherty amplifier within a transmitter;

[0018] Figure 3 is a graph of the baseband envelope;

[0019] Figure 4 is a graph illustrating an example of an upper limit on the maximum time that the auxiliary path can be shut down;

[0020] Figure 5 is a block diagram of an exemplary implementation of a transmitter constructed according to the principles set forth herein;

[0021] Figure 6 is a block diagram of an exemplary implementation of an alternative transmitter constructed according to the principles set forth herein;

[0022] Figure 7 is a schematic diagram of a baseband envelope detector; and

[0023] Figure 8 The performance of an implementation of a Doherty amplifier according to the principles disclosed herein is shown. DETAILED DESCRIPTION

[0024] Before describing the exemplary embodiments in detail, it should be noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to envelope control biasing of an auxiliary transmitter of a Doherty power amplifier. Accordingly, components are represented in the drawings by conventional symbols where appropriate, with only those specific details relevant to an understanding of the embodiments being shown so as not to obscure the present disclosure with details that would be apparent to one of ordinary skill in the art having the benefit of the description herein.

[0025] The relational terms used in this document (such as "first" and "second", "top" and "bottom", etc.) may be used solely to distinguish one entity or element from another entity or element and do not necessarily require or imply any physical or logical relationship or order between these entities or elements.

[0026] Some embodiments provide envelope controlled biasing of an auxiliary transmitter of a Doherty power amplifier.

[0027] Figure 3 An example of a baseband envelope is shown. Figure 3In the example shown, the baseband envelope is below the RMS+1dB level for 71% of the time. When the envelope of the modulated signal is low, the auxiliary amplifier in the DPA is effectively switched off. This means that power can also be saved by switching off components in the auxiliary path. When the auxiliary amplifier is switched on, the components in the auxiliary path should always be switched on, i.e. their input signal is guaranteed to be present when the auxiliary amplifier is switched on. This means that the components in the auxiliary path should be switched on at a lower power level than the auxiliary power amplifier. The lower the level, the shorter the time these components can be switched off. Therefore, a lower switch-on level reduces power consumption. Ideally, the symmetrical DPA is switched on at a maximum of Pout-6dB. Using this setting gives an upper limit on the maximum time the auxiliary path can be switched off, as Figure 4 shown.

[0028] When using a symmetrical DPA, adding an arbitrarily chosen 3dB margin for turning the auxiliary path on or off gives a -2dB root mean square (RMS) level at 47%, as shown in Figure 4 This means that Figure 2 The PPA, mixer, and LO-buffer in the auxiliary path shown can be turned off 47% of the time.

[0029] Figure 5 and Figure 6 is a diagram showing two example DPA transmitter architectures 32a ( Figure 5 ) and 32b( Figure 6 These architectures provide the ability to control the bias current of one or more components in the auxiliary path (mixer 16b, LO-buffer 18b, and PPA 20b), such as Figure 5 and Figure 6 Mixer 16b, LO-buffer 18b, and PPA 20b can be any of a number of known (or to be developed) mixers, LO-buffers, and PPAs, respectively, but they are modified individually, as part of a group, or all together as a group to be deactivated (i.e., powered down) when the envelope signal falls below one or more thresholds (e.g., by adding comparators as described below).

[0030] The term "envelope signal" is used to characterize a signal that can be based on a smooth curve that outlines the extreme values ​​of a signal. For complex signals, the envelope signal may be different for positive and negative extreme values. The envelope signal can be generated by known methods or methods to be developed. Such methods for generating the envelope signal may include rectification or squaring. Several nonlinear operations may also be used to derive the envelope signal. Furthermore, the envelope does not have to be a linear mapping of the instantaneous amplitude of the signal; a monotonic mapping may suffice. For example, taking the square of the input signal produces an envelope that tracks the instantaneous signal power. Because squaring is a smooth and monotonic mapping, the square of the signal can be used as a representation of the envelope signal. The envelope signal can also be filtered to suppress unwanted spectral components or enhance certain parts of the envelope. Therefore, as used herein, the term "envelope signal" includes envelope signals generated by any known method or methods to be developed. The term "envelope" refers to a curve that outlines the extreme values ​​of the input signal.

[0031] exist Figure 5 In the example, we use the approximate function An envelope detector 34 generates an envelope signal from the baseband input signal. The output of the envelope detector 34 is fed to a buffer 36 which distributes the envelope signal to the components to be controlled in the auxiliary path. Figure 7 One possible implementation of the baseband envelope detector 34 is shown in FIG. Figure 7 The envelope detector circuit 34 includes transistors 40 and 42. The transistor 40 receives the I baseband signal and the Q baseband signal and generates an approximate function There are many possible ways to reduce the power consumption of the components, but a straightforward approach is to use a comparator and when the envelope signal is below a certain threshold level, the bias current from the buffer 36 input to the mixer 16b can be turned off. For envelope levels above the threshold level, the bias can be set to on. Another solution consists in gradually reducing or increasing the bias current with respect to the envelope signal. Figure 6 In the example of FIG, the envelope signal is received directly from the digital baseband by a dedicated envelope digital-to-analog converter (DAC) 38. The specification of the dedicated envelope DAC 38 can be constructed with fewer bits than the DAC that generates the IQ input signal.

[0032] The rise and fall times of the bias signal will depend on the bandwidth of the envelope signal. Slow bias networks require more margin to the auxiliary power amplifier turn-on threshold, thus limiting the energy saving potential. This can be partially compensated by adding time delays along the signal path, which can be implemented through wires, all-pass filters, and other known techniques. The bias threshold can be adjusted using the bias response speed to optimize performance.

[0033] Simulation Results

[0034] A schematic design for a 22nm fully depleted silicon-on-insulator (FD-SOI) process based on DPA transmitter architectures 32a and 32b operating at 22 GHz is implemented using separate mixers 16a and 16b for the main and auxiliary paths, each generating a 90-degree phase difference. Auxiliary amplifier 26 is turned on at approximately 6 dB below the maximum output power, and the auxiliary path is configured to turn on at 9 dB below the maximum output power, i.e., using a 3 dB margin as described above. Envelope detector 34 is designed to operate with a baseband input signal, generating an output signal that controls when the auxiliary path is turned on or off. For demonstration purposes, all auxiliary components, including components 16b, 18b, and 20b, are turned on at the same envelope level. However, the auxiliary components can be configured to turn on at their own levels to minimize power consumption. For simplicity, LO buffer 18b is not controlled by the envelope signal in this simulation.

[0035] The simulation results are as follows Figure 8 As shown. Figure 8 , the simulated transmitter based on the DPA transmitters 32a, 32b generates nearly identical output signals with and without adaptive biasing on the components in the auxiliary path. For this particular example, the PPA (1.2 volt supply) and mixer (0.8 volt supply) save 60 milliwatts (mW) + 75 mW = 135 mW when turned off. These figures should then be multiplied by the time average of 47%, i.e., the orthogonal frequency division multiplexing (OFDM) signal is below the maximum output power (Pout) -9 dB threshold, resulting in an average power saving of 63 mW.

[0036] This particular transmitter based on the DPA transmitters 32a, 32b has a simulated output power of 87mW (19.4dBm) at Pavg (7dB back-off) and a power added efficiency (PAE) of 33%, resulting in a DPA power consumption of 264mW. The total transmitter PAE at Pavg is 14.8%, resulting in a power consumption of 588mW for the entire transmitter chain. From the above calculations, it can be seen that the average power saved using the proposed technique will be 135mW*47%=63mW, which should be set in comparison with the transmit power consumption of 588mW at Pavg.

[0037] When two separate mixers are used to generate a 90-degree phase shift at the input of the DPA, at least one of the components preceding the auxiliary amplifier of the DPA (PPA 20, mixer 16b, and LO-buffer 18b) is shut down for the output power level when the auxiliary amplifier 26 is effectively shut down. This can save power and improve overall transmitter efficiency at lower output powers. The envelope amplitude of the modulated OFDM signal output by envelope detectors 34 and 38 is used to control when to shut down components in the auxiliary path. Any one or more of the auxiliary components, including mixer 16b, LO-buffer 18b, and PPA 20b, can be shut down to optimize power consumption without degrading the desired output signal.

[0038] According to one aspect, a DPA transmitter 32a, 32b is provided that has a main amplifier 24 in a main signal path and an auxiliary amplifier 26 in an auxiliary signal path. The auxiliary amplifier 26 is configured to be activated only when the envelope of the input signal input to the DPA transmitter 32a, 32b exceeds a power threshold. The DPA transmitter 32a, 32b also includes at least one component in the auxiliary signal path that is configured to be deactivated when the auxiliary amplifier 26 is deactivated, the at least one component including at least one of a pre-power amplifier 20b, a mixer 16b, and a local oscillator buffer 18b.

[0039] According to this aspect, in some embodiments, the DPA transmitters 32a and 32b include a comparator configured to compare an envelope signal with an envelope threshold, and a bias current controller configured to adjust the bias current of at least one component to deactivate the at least one component when the envelope signal does not exceed the envelope threshold. The comparator and bias current controller act on a signal from a buffer 36 to control the bias current to the mixer 16b. In some embodiments, adjusting the bias current includes gradually decreasing or increasing the bias current relative to the envelope signal. In some embodiments, the DPA transmitters 32a and 32b also include a digital-to-analog converter (DAC) 38 configured to be deactivated when the auxiliary amplifier 26 is shut down. In some embodiments, the envelope DAC 38 is configured to generate an envelope signal. In some embodiments, the mixer 16b in the auxiliary signal path receives an input signal and an envelope signal to provide an adaptive bias to control the mixer 16b. In some embodiments, the output of the mixer 16b is input to the preamplifier 20b, which also receives the envelope signal. In some embodiments, the DPA transmitters 32a, 32b further include a local oscillator buffer 18b configured to receive an envelope signal. In some embodiments, the pre-power amplifier 20b receives the envelope signal, which is used to adjust the gain of the pre-power amplifier 20b, with the adjustment tracking the envelope signal. In some embodiments, in response to the envelope signal exceeding a different envelope threshold of each of the pre-power amplifier 20b, the mixer 16b, and the local oscillator buffer 18b, the pre-power amplifier 20b, the mixer 16b, and the local oscillator buffer 18b are each shut down.

[0040] According to another aspect, a Doherty amplifier 32a, 32b is provided. The Doherty amplifier 32a, 32b includes a main amplifier 24 in a main signal path configured to receive an input signal. The Doherty amplifier 32a, 32b also includes an auxiliary amplifier 26 in an auxiliary signal path having components including an envelope detector 34, 38 configured to detect an envelope of the input signal to generate an envelope signal, and a mixer 16b configured to mix the input signal with a local oscillator signal, the mixing being based at least in part on an adaptive bias provided by the envelope signal.

[0041] According to this aspect, envelope detectors 34, 38 include digital-to-analog converters (DACs). In some embodiments, mixer 16b is configured to receive an envelope signal to adaptively bias mixer 16b. In some embodiments, the output of mixer 16b is input to a preamplifier 20b that also receives the envelope signal. In some embodiments, the components in the auxiliary signal path include a preamplifier 20b configured to receive the envelope signal, the envelope signal being used to adjust the gain of preamplifier 20b, with the adjustment tracking the envelope signal. In some embodiments, Doherty amplifiers 32a, 32b further include a bias current controller within buffer 36, the bias current controller being configured to adjust the bias current of at least one component in the auxiliary signal path to deactivate the component in the auxiliary signal path when the envelope signal does not exceed an envelope threshold. In some embodiments, adjusting the bias current includes gradually decreasing or increasing the bias current relative to the envelope signal. In some embodiments, each component in the auxiliary signal path is deactivated separately in response to the envelope signal exceeding a different envelope threshold for each of the components in the auxiliary signal path.

[0042] According to another aspect, the Doherty amplifiers 32a, 32b include a filter configured to receive and filter an input signal to be amplified by the Doherty amplifiers 32a, 32b to generate a filtered input signal; and a splitter circuit to split the filtered input signal into a main signal path and an auxiliary signal path. In the main signal path, a first mixer 16a is configured to mix the filtered input signal with a local oscillator signal to generate a first mixer output signal. A first pre-power amplifier 20a is configured to receive and amplify the first mixer output signal to generate a main amplifier input signal. The Doherty amplifiers 32a, 32b also include a main amplifier 24, and in the auxiliary path, a second mixer 16b is configured to mix the filtered input signal with a local oscillator signal to generate a second mixer output signal, the second mixer being activated and deactivated by the envelope of the main amplifier input signal. The second preamplifier 20b is configured to receive and amplify the second mixer output signal to generate an auxiliary amplifier input signal. The second preamplifier is activated and deactivated by the envelope of the auxiliary amplifier input signal. The Doherty amplifiers 32a, 32b also include an auxiliary amplifier 26. In some embodiments, the Doherty amplifiers further include local oscillator buffers 18a, 18b configured to buffer the local oscillator signal. The local oscillator buffers are activated and deactivated by the envelope of the amplifier input signal.

[0043] In conjunction with the above description and accompanying drawings, many different embodiments are disclosed herein. It will be understood that verbatim describing and illustrating every combination and subcombination of these embodiments would be unduly repetitive and obfuscating. Therefore, all embodiments may be combined in any manner and / or combination, and this specification, including the accompanying drawings, is to be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, as well as the manner and process of making and using them, and will support claims for any such combination or subcombination.

[0044] The abbreviations used in this article are as follows:

[0045] Abbreviation

[0046] DPA Doherty Power Amplifier

[0047] LO-Buffer Local Oscillator Buffer

[0048] OFDM Orthogonal Frequency Division Multiplexing

[0049] PA power amplifier

[0050] PPA Pre-Power Amplifier

[0051] Psat saturated output power

[0052] Those skilled in the art will recognize that the embodiments described herein are not limited to what has been specifically shown and described above. In addition, unless otherwise indicated above, it should be noted that all drawings are not drawn to scale. Various modifications and variations are possible in light of the above teachings without departing from the scope of the appended claims.

Claims

1. A transmitter having a main amplifier in a main signal path and an auxiliary amplifier in an auxiliary signal path, the auxiliary amplifier being configured to be activated only when an envelope of an input signal input to the transmitter exceeds a power threshold, the transmitter comprising: at least one component in the auxiliary signal path, the at least one component being configured to be deactivated when the auxiliary amplifier is deactivated, the at least one component comprising a mixer, The mixer in the auxiliary signal path receives the input signal and an envelope signal indicating the envelope, so as to provide an adaptive bias based on the envelope signal to control the mixer.

2. The transmitter according to claim 1, further comprising: a comparator configured to compare the envelope signal with an envelope threshold; as well as A bias current controller is configured to adjust a bias current of the at least one component when the envelope signal does not exceed the envelope threshold, so as to deactivate the at least one component.

3. The transmitter according to claim 2, wherein Adjusting the bias current includes gradually decreasing or increasing the bias current with respect to the envelope signal.

4. The transmitter according to claim 1, further comprising: The digital-to-analog converter (DAC) is configured to be deactivated when the auxiliary amplifier is turned off.

5. The transmitter according to claim 4, wherein The DAC is configured to generate the envelope signal. The transmitter according to claim 1 , wherein: The at least one component further includes a pre-power amplifier, to which the output of the mixer is input, the pre-power amplifier receiving the envelope signal.

7. The transmitter according to claim 6, wherein The at least one component also includes a local oscillator buffer configured to receive the envelope signal.

8. The transmitter according to claim 6, wherein The pre-power amplifier receives the envelope signal, and the envelope signal is used to adjust the gain of the pre-power amplifier.

9. The transmitter according to claim 7, wherein In response to the envelope signal exceeding a different envelope threshold of each of the pre-power amplifier, the mixer, and the local oscillator buffer, the pre-power amplifier, the mixer, and the local oscillator buffer are each respectively shut down.

10. A Doherty amplifier, comprising: a main amplifier in a main signal path, the main signal path configured to receive an input signal; an auxiliary amplifier in an auxiliary signal path, the auxiliary signal path having components including an envelope detector configured to detect an envelope of the input signal to generate an envelope signal, and a mixer configured to mix the input signal with a local oscillator signal, the mixing being based at least in part on an adaptive bias provided by the envelope signal; as well as A bias current controller is configured to adjust a bias current of at least one component in the auxiliary signal path to deactivate the component in the auxiliary signal path when the envelope signal does not exceed an envelope threshold.

11. The Doherty amplifier according to claim 10, wherein The envelope detector includes a digital-to-analog converter DAC.

12. The Doherty amplifier according to claim 10, wherein The mixer is configured to receive the envelope signal to adaptively bias the mixer based on the envelope signal.

13. The Doherty amplifier according to claim 12, wherein The output of the mixer is input to a pre-power amplifier which also receives the envelope signal.

14. The Doherty amplifier according to any one of claims 10 to 12, wherein The components in the auxiliary signal path include a pre-power amplifier configured to receive the envelope signal, the envelope signal being used to adjust a gain of the pre-power amplifier.

15. The Doherty amplifier according to claim 10, wherein Adjusting the bias current includes gradually decreasing or increasing the bias current with respect to the envelope signal.

16. The Doherty amplifier according to any one of claims 10 to 13, wherein In response to the envelope signal exceeding a different envelope threshold for each component in the auxiliary signal path, each component in the auxiliary signal path is individually deactivated.

17. A Doherty amplifier, comprising: a filter configured to receive and filter an input signal to be amplified by the Doherty amplifier to generate a filtered input signal; a splitter circuit for splitting the filtered input signal into a main signal path and an auxiliary signal path; In the main signal path: a first mixer configured to mix the filtered input signal with a local oscillator signal to generate a first mixer output signal; a first pre-power amplifier configured to receive and amplify the first mixer output signal to generate a main amplifier input signal; as well as Main amplifier; as well as In the auxiliary signal path: a second mixer configured to mix the filtered input signal with a local oscillator signal to generate a second mixer output signal, the second mixer being activated and deactivated by the envelope of the main amplifier input signal; a second pre-power amplifier configured to receive and amplify the second mixer output signal to generate an auxiliary amplifier input signal, the second pre-power amplifier being activated and deactivated by an envelope of the auxiliary amplifier input signal; and Auxiliary amplifier.

18. The Doherty amplifier of claim 17, further comprising: A local oscillator buffer is configured to buffer a local oscillator signal, the local oscillator buffer being activated and deactivated by an envelope of the pre-power amplifier input signal.

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