The field of the invention is amplifiers.
The following background discussion includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Among other uses, Doherty amplifiers are widely used in wireless communications to amplify digitally modulated signals having non-constant envelopes. Under these signals, traditional Doherty amplifiers waste driver power at lower envelope power levels by generally splitting the driver output power between main and auxiliary amplifiers even when the auxiliary amplifier is not enabled. Unfortunately, this generally results in degradation of the Doherty amplifier's efficiency.
U.S. pat. publ. no. 2012/0025915 to Ui and U.S. Pat. No. 8,115,546 to Hong, et al. discuss various configurations of Doherty amplifiers are known in the art that have improved efficiencies over traditional Doherty amplifiers. In addition, EPO patent appl. no. 2372905 to Alcatel Lucent and U.S. Pat. No. 7,893,770 to Yamauchi et al. discuss various devices and arrangements that vary the voltage to main and auxiliary amplifiers to increase the Doherty amplifier's efficiency. Finally, the article “A High-Efficiency 100-W GaN Three-Way Doherty Amplifier for Base-Station Applications” discusses using GaN technology for 3-way Doherty amplifiers to increase efficiency.
However, in all of the references, a proportion of the driver's power directed between the main and auxiliary amplifiers remains constant, and does not depend on the input signal's envelope magnitude. In addition, none of the references known to Applicant contemplate individually driving first and second inputs of a hybrid coupler using first and second drivers to dynamically distribute driver output power between main and auxiliary amplifiers as a function of an input signal's envelope.
Thus, there is still a need for high efficiency Doherty amplifiers configured to dynamically distribute driver output power between main and auxiliary amplifiers.
The inventive subject matter provides apparatus, systems and methods for increasing the efficiency of symmetrical or asymmetrical Doherty amplifiers. In especially preferred embodiments, the Doherty amplifiers operate under digitally-modulated signals with non-constant envelopes, such as those used by various wireless communication standards (e.g., CDMA, LTE, WiMAX, etc.). Preferred Doherty amplifiers include an input hybrid coupler having first and second inputs, and first and second drivers that individually drive the first and the second inputs of the hybrid coupler, respectively.
Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
One should appreciate that the disclosed techniques provide many advantageous technical effects including increasing the efficiency of Doherty amplifiers, especially when used with digitally modulated signals having non-constant envelopes.
The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
In
In a traditional Doherty amplifier, the proportion of driver output power directed between the main and auxiliary amplifiers 150 and 152 is constant regardless of the input signal's envelope magnitude. This static distribution of power wastes the driver's output power directed to the auxiliary amplifier 152 when the input power level is below a predetermined threshold because the auxiliary amplifier 152 of the Doherty amplifier 100 remains closed. This is especially problematic when the Doherty amplifier 100 is used with digitally modulated signals having high peak-to-average ratios because a substantial amount of the output power of the driver 110 (typically about 40-60%) is fed into the auxiliary amplifier 152 that is often closed. The wasted power results in a degradation of the amplifier's efficiency.
Doherty amplifier 200 includes an input power divider, which is preferably a hybrid coupler 202 although a directional coupler or a splitter could alternatively be used. The hybrid coupler 202 receives an input signal from directional coupler 201 and produces first and second inputs, which can be fed to first and second signal modulators 206 and 208. The first and second signal modulators 206 and 208 can be configured to adjust a phase of one or both of the first and second inputs, as needed. The first and second inputs can then be individually fed to first and second drivers 211 and 212, respectively (collectively driver 210).
In such embodiments, the first driver 211 can be configured to receive the first input signal that has a first input phase and a first input amplitude, and the second driver 212 can be configured to receive a second input signal that has a second input phase and a second input amplitude. Advantageously, the first and second drivers 210 and 211 can be configured and disposed within the Doherty amplifier 200, such that the drivers 210 and 211 can individually drive the first and second inputs of hybrid coupler 202. Because multiple signal modulators 206 and 208 are utilized in the Doherty amplifier 200, it is contemplated that the first and second input signals can have different input phases and/or amplitudes from one another.
A phase shifter controller 230 can be functionally coupled to the directional coupler 201 and the first and second signal modulators 206 and 208. The phase shift controller 230 preferably is configured to allow for dynamic adjustment of the phases of each of the first and second input signals using the first and second signal modulators 206 and 208. Preferred signal modulators include phase shifters, although vector modulators or any other commercially suitable signal modulator could be used. The phases of the first and second input signals can be adjusted across a dynamic range as a function of the input signal envelope power. In some contemplated embodiments, the dynamic range can be between about 5 dB to 15 dB, and more preferably between about 10 dB to 15 dB. However, the specific phases of the first and second input signals will likely depend on the parameters of the received input signal.
It is especially preferred that the adjustment to the first and second input phases across the dynamic range occurs such that a constant output signal phase is maintained across the dynamic range. An example of this is described below in reference to
φ1=φ0−f(Pinp); and
φ2=−φ1.
where φ0 is the initial phase value and f(Pinp) is the linear or non-linear function of the input power. Under these conditions:
P
inpMain
=P
inp
*Gd*Sin2(φ1);
P
inpAux
=P
inp
*Gd*Sin2(φ1);
φinpMain=φinp+φ0; and
φinpAux=φinp+φ0.
where Pinp is the amplifier input power, Gd is the Driver gain, PinpMain is the input power of the main amplifier, PinpAux is the input power of the main amplifier, φinpMain is the main amplifier input signal phase, φinpAux is the auxiliary amplifier input signal phase, φinp is the amplifier input signal phase, and φ0 is a constant value.
It is further contemplated that one or both of the first and second input amplitudes can also be dynamically adjusted.
The outputs of the first and second drivers 211 and 212 can be fed to a hybrid coupler 240 or other power divider, which thereby directs the driver outputs to a main amplifier 250 and an auxiliary amplifier 252. The driver output to the main amplifier 250 is first fed to a fixed phase shifter 242 that shifts the phase of the output signal by a predetermined amount. The output of the main amplifier 250 can then be summed with the output of the auxiliary amplifier 252 in a Doherty combiner 260 and outputted as an amplified signal.
Thus, using the above described Doherty amplifier 200, the proportion of the driver's power directed to the auxiliary amplifier 252 relative to the main amplifier 250 can be controlled as a function of the input signal's envelope. For example, at the back-off where the input signal's envelope voltage is low, a majority of the power of the driver 210, and preferably, all of the power of the driver 210, goes to the main amplifier 250. At full power where the input signal's envelope reaches its maximum value, the output power of the driver 210 is distributed between the main and auxiliary amplifiers 250 and 252. In such embodiments, the proportion of the power distribution between the main and auxiliary amplifiers 250 and 252 may be 1:1, 1:2, 1:3, or any other commercially suitable proportion, depending on the specific application. Such proportion can be determined by one of ordinary skill in the art taking into account the above relationships.
Dynamic redistribution of driver output power between main and auxiliary amplifiers 250 and 252 advantageously allows for a substantial decrease of the power wasted by the driver 210. Such reduction in waste is critical in many applications including, for example, cellular communications, as it can substantially increase the battery life of cellular phones, for example.
Another embodiment of an improved Doherty amplifier 400 is shown in
In some contemplated embodiments, the directional coupler value could fall within a range of between about −1 db to about −10 db range. The choice of the coupling value provides auxiliary amplifier phase correction across the dynamic range of the input signal, and could contribute to amplifier linearization. With respect to the remaining numerals in
Yet another embodiment of an improved Doherty amplifier 600 is presented in
Another embodiment is presented in
Still another embodiment is shown in
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously.
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the scope of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
This application claims the benefit of priority to U.S. provisional application having Ser. No. 61/699,590 filed on Sep. 11, 2012. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Number | Date | Country | |
---|---|---|---|
61699590 | Sep 2012 | US |