GB2463511A - A class E amplifier with power supply modulation and a predistorted input signal - Google Patents
A class E amplifier with power supply modulation and a predistorted input signal Download PDFInfo
- Publication number
- GB2463511A GB2463511A GB0817101A GB0817101A GB2463511A GB 2463511 A GB2463511 A GB 2463511A GB 0817101 A GB0817101 A GB 0817101A GB 0817101 A GB0817101 A GB 0817101A GB 2463511 A GB2463511 A GB 2463511A
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- Prior art keywords
- input signal
- predistortion
- power amplifier
- amplifier
- circuitry
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- 238000000034 method Methods 0.000 claims description 20
- 230000018199 S phase Effects 0.000 abstract 1
- 230000010363 phase shift Effects 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
- H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
- H03F1/0211—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers with control of the supply voltage or current
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
- H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
- H03F1/0211—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers with control of the supply voltage or current
- H03F1/0216—Continuous control
- H03F1/0222—Continuous control by using a signal derived from the input signal
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
- H03F1/3258—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits based on polynomial terms
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
- H03F1/3282—Acting on the phase and the amplitude of the input signal
- H03F1/3288—Acting on the phase and the amplitude of the input signal to compensate phase shift as a function of the amplitude
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/217—Class D power amplifiers; Switching amplifiers
- H03F3/2176—Class E amplifiers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Algebra (AREA)
- General Physics & Mathematics (AREA)
- Mathematical Analysis (AREA)
- Mathematical Optimization (AREA)
- Pure & Applied Mathematics (AREA)
- Amplifiers (AREA)
Abstract
The amplitude of the input signal Vin for a class E power amplifier 20 with power supply modulation 18 is adjusted by a predistorter 22 in order to achieve either optimum linearity or power added efficiency. Optimum efficiency is achieved by avoiding underdriving or overdriving of the amplifier 20. Optimum linearity is achieved by adjusting the amplitude of Vin to achieve a linear relation between the output signal magnitude and the supply voltage Vds. The predistorter 22 may alternatively or additionally adjust the phase of Vin to correct the amplifier's phase response. The predistorter 22 may use a lookup table or polynomial equation. An amplitude limiter 16 may be arranged before the predistorter.
Description
POWER AMPLIFIER ENVELOPE MODULATION
TECHNICAL FIELD
This invention relates to power amplifiers, and in particular to a system for operating a power amplifier with high efficiency and linearity.
BACKGROUND OF THE INVENTION
Power amplifiers are known, in which the amplifier can be operated most efficiently when it is switched fully on or fully off. Amplifiers of this type are referred to as switching amplifiers. In order to amplify a complex modulated signal with a switching amplifier, the phase variation of the complex modulated signal is applied as a fixed amplitude input to the switching amplifier, with the amplitude variation of the complex modulated signal being used to vary the supply bias of the switching amplifier. The result is that the switching amplifier is switched fully on or fully off, and thus can operate highly efficiently, although at relatively low linearity.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a power amplifier system, comprising: an input, for receiving an input signal; a power amplifier; a voltage supply circuit, for providing a power supply voltage to the power amplifier, the power supply voltage being derived from an envelope of the input signal; and predistortion circuitry, for predistorting the input signal to form a power amplifier input signal, and for applying the power amplifier input signal to an input of the power amplifier to form an amplifier output signal.
According to a second aspect of the present invention, there is provided a method of operation of an amplifier system, the method comprising: This has the advantage that the amplifier can be operated with maximum efficiency, or maximum linearity, or a desirable compromise between efficiency and linearity.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a schematic diagram, illustrating a power amplifier according to a first aspect of the invention.
Figure 2 illustrates the relationship between an amplifier output signal and input signal, for various values of an amplifier supply voltage.
Figure 3 illustrates a particular relationship between an amplifier output signal and an amplifier supply voltage, and a relationship between an amplifier input signal and an amplifier supply voltage required to achieve this.
Figure 4 illustrates the relationship between the power added efficiency of the amplifier and the amplifier input signal, for various values of an amplifier supply voltage.
Figure 5 illustrates two different possible relationships between the amplifier output signal and an amplifier supply voltage.
DETAILED DESCRIPTION
Figure 1 shows a power amplifier system 10, in accordance with an embodiment of the invention.
In the power amplifier system 10, a system input signal is applied to an input terminal 12. The system input signal may take any form, but the power amplifier system 10 is particularly intended to provide advantageous results when the system input signal is in the form of a complex modulated radio frequency carrier signal.
The system input signal is applied to a separator 14, which separates the input signal into the modulated carrier signal, which in this illustrated embodiment of the invention is applied to a limiter 16, and the envelope signal, which is applied to a high current voltage controlled voltage supply circuit 18.
The modulated carrier signal, received from the separator 14, therefore contains the phase variation of the system input signal, and the limiter 16 acts on this modulated carrier signal to form a version of the carrier signal, whose amplitude is limited. In other embodiments of the invention, the limiter 16 may be omitted, and an unlimited version of the carrier signal may be applied to the further processing circuitry.
The envelope signal, received from the separator 14, contains the amplitude variation of the system input signal, and so the voltage controlled voltage source circuit 18 generates a voltage VOS, whose value depends on the instantaneous magnitude of the envelope signal, and hence of the system input signal. Various voltage controlled voltage source circuits are known, and any suitable circuit may be used here.
The voltage VDS is then applied as a power supply voltage to a power amplifier 20. In this iflustrated embodiment, the power amplifier 20 is a Class E switching amplifier, of a type which is known in itself, but it will be appreciated that the invention can equally be applied to other switching amplifiers.
In one conventional power amplifier system, the amplitude-limited carrier signal is applied directly as an input to the power amplifier. Linearization can be achieved in this case by applying predistortion to the envelope signal, and hence to the power supply voltage of the amplifier.
However, in this embodiment of the present invention, the carrier signal, or the amplitude-limited carrier signal if the limiter 16 is present, is applied to predistortion circuitry 22, which applies a form of predistortion to form an amplifier input signal VIN, which is in turn applied as an input signal to the power amplifier 20.
The amplifier output signal VOUT will therefore be a high power complex modulated signal, which is a function of VIN and VDS, as will be generally understood by the person skilled in the art, and Figure 2 shows this relationship. Specifically, Figure 2 shows a series of curves 30a, 30b, 30c, 30d, 30e,, 30f, each representing the relationship between the envelope of the amplifier output signal VOUT and the envelope of the amplifier input signal VIN at a different value of the power supply voltage VDS, with the value of VDS increasing between each successive pair of the curves 30a, 30b, 30c, 30d, 30e, 30f.
It will be noted that each of the curves 30a, 30b, 30c, 30d, 30e, 30f has a first region, associated with lower values of the amplifier input signal, in which the amplifier output signal VOUT increases with increasing values of the amplifier input signal VIN, and a second region, associated with higher values of the amplifier input signal, in which increasing values of the amplifier input signal VIN do not result in any further increase in the amplifier output signal VOUT. A curved line 32 in Figure 2 represents the boundary between these regions.
In Figure 2, the curve 30f represents the relationship between the amplifier output signal VOUT and the amplifier input signal VIN at the maximum possible value of the power supply voltage VDS, namely VDSMAX. The value VIN(MIN) of the amplifier input signal VIN at the point where the curve 32 meets the curve 30f therefore represents the boundary between the first and second regions at VDSMAX. For values of the amplifier input signal VIN above the value VIN(MIN), the amplifier operation will be such that the amplifier output signal is always switching between the positive and negative supply rails, with the result that there will be a linear relationship between VOUT and VOS, but for values of the amplifier input signal V1 below the value VIN(MIN), the amplifier output signal will not always be switching between the positive and negative supply rails.
Figure 3 is a further plot, showing two different relationships, between the envelope of the amplifier output voltage and the power supply voltage, and between the amplifier input signal and the power supply voltage.
Thus, in Figure 3, a first curve 38 shows the relationship between the amplifier output signal VOUT and the power supply voltage VDS, when the amplifier is made to operate in the linear mode. It can therefore be seen that this is a straight line relationship, and any increase in the power supply voltage leads to a corresponding increase in the amplifier output signal. Conventionally, this relationship can be established by applying predistortion to vary the power supply voltage VDS, while applying a constant amplitude amplifier input signal.
However, as also shown in Figure 3, a linear relationship between the amplifier output signal VOUT and the power supply voltage VDS can alternatively be established by manipulating the envelope of the amplifier input signal VIN, varying it as a function of VDS, as shown by the second curve 40.
In general, it is desirable to operate the amplifier in a linear mode. However, it is also necessary to take into account the efficiency of the amplifier, and it is not usuaUy possible to operate an amplifier with maximum linearity and maximum efficiency.
Rather, there is often a need to reach a compromise between these desirable goals.
Figure 4 shows a series of curves 44a, 44b, 44c, 44d, each representing the relationship between the power added efficiency (PAE) of the amplifier system, and the amplifier input signal VIN at a different value of the power supply voltage VDS, with the value of V05 increasing between each successive pair of the curves 44a, 44b, 44c, 44d.
It will be noted that each of the curves 44a, 44b, 44c, 44d has a maximum value. That is, the amplifier operates relatively inefficiently at low signal values, with the efficiency increasing towards a peak value, and then declining again at signal values that are greater than the signal values that are required to achieve full rail switching.
A curve 46 is shown in Figure 4, representing the amplifier input envelope voltage V1 that is required for maximum efficiency at each value of the power supply voltage VDS.
This can be understood by considering that, in the region to the left of the line 46 in Figure 4, i.e. at lower input signal values, the input signal is not large enough to fully switch the output value from rail-to-rail, and so the amplifier 20 is not operating at its maximum efficiency. However, in the region to the right of the line 46, i.e. at higher values of the amplifier input signal VIN, although the amplifier will be switched from rail-to-rail, more input power is being supplied than was necessary to achieve this. The region to the right of the line 46 in Figure 4 corresponds essentially to the region to the right of the line 32 in Figure 2. As shown in Figure 2, increasing the value of the input signal VIN beyond the point necessary to achieve rail-to-rail switching does not produce any change in the amplitude of the output signal, and so the power added efficiency (PAE) reduces.
Figure 5 shows two lines 50a, 50b, each representing a possible relationship between the amplifier output signal VOUT and the power supply voltage VDS. Specifically, the line 50a is a straight line, showing the operation of the amplifier with maximum linearity, where increasing the power supply voltage VDS produces as nearly as possible a directly corresponding increase in the output signal VOUT. This is achieved by manipulating the value of the input signal VIN in accordance with the curve 40 shown in Figure 3. The line 50b shows the operation of the amplifier with maximum power added efficiency, and this is achieved by manipulating the value of the input signal VIN in accordance with the curve 46 shown in Figure 4.
The predistortion circuitry 22 therefore applies the required amplitude control to its input signal, so that the amplifier input signal VIN causes the amplifier 20 to operate at maximum linearity, as shown by the curve 50a in Figure 5, or at maximum efficiency, as shown by the curve 50b in Figure 5, or with a desirable compromise between maximum tinearity and maximum efficiency, in the region between the curves 50a and 50b.
Specifically, the predistortion may be applied by operating on the input signal of the predistortion circuitry 22. For example, in one embodiment of the invention, the response of the power amplifier 20 is measured, and the coefficients of a polynomial equation are derived. Then, based on the magnitude of the envelope signal, this polynomial equation generates a carrier signal VIN that has reduced envelope variations, and can be applied to the amplifier 20.
In another embodiment of the invention, the elements of a look-up table can be derived based on the measured response of the power amplifier 20. Then, based on the magnitude of the envelope signal, this look-up table is used to produce a desired carrier signal V1w that can be applied to the amplifier 20.
In some embodiments of the invention, a desired predistortion function, for example in the form of a polynomial equation or a look-up table as described above, can be implemented. The desired predistortion function can be set such that the linearity of the amplifier is maximized, or such that the efficiency of the amplifier is maximized, or such that some desirable compromise between linearity and efficiency is achieved.
This arrangement is useful when the operating conditions of the amplifier are known in advance.
In order to provide an appropriate predistortion function, the response of the power amplifier can be characterized over a range of values for its input parameters. More specifically, the magnitude of the output signal can be determined for a range of values for each of the input power (or, equivalently, the magnitude of the input signal VIN), and the power supply voltage VDS.
As discussed above, the power supply voltage VDS is set based on the envelope magnitude, and so this characterization can be used to determine a best fit polynomial (for example, a cubic equation) that generates the input power (or the magnitude of the input signal VIN), that produces the optimum PAE for any signal envelope. Thus, the value of V0 is set based on the envelope magnitude, and the value of VIN is set to achieve the corresponding peak efficiency based on the curves of Fig. 4.
In a similar manner, the characterization can be used to determine a different best fit polynomial (for example, another cubic equation) that generates the input power (or the magnitude of the input signal VIN), that produces the optimum linearity for any signal envelope. Thus, the value of VOS is set based on the envelope magnitude, and the value of VIN is then set based on the curve 32 in Figure 3 For example, it might be known that it will always be the intention to operate the amplifier with maximum efficiency. In this case, it is necessary to determine only the predistortion function that produces the optimum PAE.
In other embodiments of the invention, two or more such predistortion functions can be implemented. Again, for example, one of the predistortion functions can favour the linearity of the amplifier over the efficiency of the amplifier, while another can favour the linearity over the efficiency. Then, the user can select which characteristic will be applied, and can alter this selection in use of the device.
In one embodiment of the invention, the calculation is carried out in a complex mode.
That is, it has been observed that, in many switching amplifiers, the amplifier has a phase response that varies with the amplitude of the input signal. That is, the magnitude of the delay across the power amplifier 20 is a function of the magnitude of the envelope of its input signal VIN.
Therefore, the phase of the carrier signal can be predistorted, so that the variation of the amplifier phase response with the amplitude of the input signal does not destroy the required phase information on the signal.
This can in principle be in addition to, or as an alternative to, the predistortion of the amplitude of the carrier signal described above.
However, when the amplitude is to be predistorted, the phase can also be predistorted so that the predistortion of the amplitude does not result in any unwanted change in the phase of the output signal.
The amplitude predistortion described above has the effect of reducing the peak-to-average-power-ratio (PAPR) of the signal, normalizing its amplitude so that the absolute value of the complex baseband signal is maintained over a relatively small range at the upper limit, and it is this complex signal that is used to apply the phase information to the RF carrier.
A characteristic of switching amplifiers is that their group delay (or phase shift) depends strongly on the RF input power, but only weakly on the power supply voltage. Thus, as the envelope of the signal varies over time, so does the RF input power to the amplifier, that is, the power of the signal output from the predistortion circuitry 22. The result is that there would be an undesirable phase shift in the output of the amplifier 20.
However, by measuring the phase relationship between the input signal and the output signal of the amplifier 20, it is possible to determine an appropriate counteracting phase shift, and this counteracting phase shift can be applied in the predistortion circuitry 22 in order to negate the undesirable variable phase delay of the switching amplifier.
There is thus provided an amplifier system that can be used to provide desired characteristics.
Claims (17)
- CLAIMS1. A power amplifier system, comprising: an input, for receiving an input signal; a power amplifier; a voltage supply circuit, for providing a power supply voltage to the power amplifier, the power supply voltage being derived from an envelope of the input signal; and predistortion circuitry, for predistorting the input signal to form a power amplifier input signal, and for applying the power amplifier input signal to an input of the power amplifier to form an amplifier output signal.
- 2. A power amplifier system as claimed in claim 1, further comprising: a limiter, for forming a voltage limited version of the input signal; wherein the voltage limited version of the input signal is applied to the predistortion circuitry, such that the power amplifier input signal is a predistorted version of the voltage limited version of the input signal.
- 3. A power amplifier system as claimed in claim 1, wherein the predistortion circuitry is adapted to predistort the amplitude of the input signal.
- 4. A power amplifier system as claimed in claim 1, wherein the predistortion circuitry is adapted to predistort the phase of the input signal.
- 5. A power amplifier system as claimed in claim 1, wherein the predistortion circuitry is adapted to predistort the amplitude and phase of the input signal, and wherein the predistortion circuitry is adapted to predistort the phase of input signal in such a way as to counteract any phase change that would occur in the power amplifier as a result of predistortion of the amplitude of the input signal.
- 6. A power amplifier system as claimed in any preceding claim, wherein the predistortion circuitry comprises a look-up table, for determining a predistortion to be applied to the input signal.
- 7. A power amplifier system as claimed in any preceding claim, wherein the predistortion circuitry comprises means for applying a predistortion in the form of a polynomial equation to be applied to the input signal.
- 8. A power amplifier system as claimed in any preceding claim, wherein the predistortion performed by the predistortion circuitry is controlled based on the envelope of the input signal.
- 9. A power amplifier system as claimed in any preceding claim, further comprising means for selecting between a plurality of predistortion functions to be performed by the predistortion circuitry.
- 10. A method of operation of a power amplifier system, wherein the power amplifier system comprises: an input, for receiving an input signal; a power amplifier; a voltage supply circuit, for providing a power supply voltage to the power amplifier, the power supply voltage being derived from an envelope of the input signal; and predistortion circuitry, for predistorting the input signal to form a power amplifier input signal, and for applying the power amplifier input signal to an input of the power amplifier to form an amplifier output signal, the method comprising: determining at least one predistortion function, such that the predistortion circuitry predistorts the input signal based on the predistortion function.
- 11. A method as claimed in claim 10, wherein the predistortion function is such that the predistortion circuitry predistorts the input signal based on the envelope of the input signal.
- 12. A method as claimed in claim 10, wherein the predistortion function is such that the power amplifier is caused to operate in an efficient mode.
- 13. A method as claimed in claim 10, wherein the predistortion function is such that the power amplifier is caused to operate in a linear mode.
- 14. A method as claimed in claim 10, wherein a first predistortion function is such that the power amplifier is caused to operate in an efficient mode, and a second predistortion function is such that the power amplifier is caused to operate in a linear mode.
- 15. A method as claimed in claim 14, further comprising selecting between the first predistor-tion function and the second predistortion function.
- 16. A method as claimed in one of claims 10 to 15, wherein the predistortion function causes predistortion of an amplitude of the input signal.
- 17. A method as claimed in claim 16, wherein the predistortion function causes predistortion of a phase of the input signal, the predistortion of the being such as to counteract any change in phase of the power amplifier output signal caused by predistortion of the amplitude of the input signal.Amendments to the claims have been filed as followsCLAIMS1. A method of operation of a power amplifier system, wherein the power amplifier system comprises: an input, for receiving an input signal; a power amplifier; a voltage supply circuit, for providing a power supply voltage to the power amplifier, the power supply voltage being derived from an envelope of the input signal; and predistortion circuitry, for predistorting the input signal to form a power amplifier input signal, and for applying the power amplifier input signal to an input of the power amplifier to form an amplifier output signal, the method comprising: determining at least one predistortion function, such that the predistortion circuitry predistorts the input signal based on the predistortion function, wherein the predistortion function is such that the power amplifier is caused to C\I operate in an efficient mode.2. A method of operation of a power amplifier system, wherein the power amplifier system comprises: an input, for receiving an input signal; a power amplifier; a voltage supply circuit, for providing a power supply voltage to the power amplifier, the power supply voltage being derived from an envelope of the input signal; and predistortion circuitry, for predistorting the input signal to form a power amplifier input signal, and for applying the power amplifier input signal to an input of the power amplifier to form an amplifier output signal, the method comprising: determining at least two predistortion functions, such that the predistortion circuitry predistorts the input signal based on one of the predistortion functions, wherein a first predistortion function is such that the power amplifier is caused to operate in an efficient mode, and a second predistortion function is such that the power amplifier is caused to operate in a linear mode.3. A method as claimed in claim 2, further comprising selecting between the first predistortion function and the second predistortion function.4. A method as claimed in claim 1 or 2, wherein the predistortion function is such that the predistortion circuitry predistorts the input signal based on the envelope of the input signal.5. A method as claimed in claim 1 or 2, wherein the predistortion function is such that the power amplifier is caused to operate in a linear mode.6. A method as claimed in one of claims 1 to 5, wherein the predistortion function causes predistortion of an amplitude of the input signal.7. A method as claimed in claim 6, wherein the predistortion function causes predistortion of a phase of the input signal, the predistortion of the being such as to counteract any change in phase of the power amplifier output signal caused by predistortion of the amplitude of the input signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0817101A GB2463511A (en) | 2008-09-10 | 2008-09-10 | A class E amplifier with power supply modulation and a predistorted input signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0817101A GB2463511A (en) | 2008-09-10 | 2008-09-10 | A class E amplifier with power supply modulation and a predistorted input signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0817101D0 GB0817101D0 (en) | 2008-10-29 |
| GB2463511A true GB2463511A (en) | 2010-03-17 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0817101A Withdrawn GB2463511A (en) | 2008-09-10 | 2008-09-10 | A class E amplifier with power supply modulation and a predistorted input signal |
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| Country | Link |
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| GB (1) | GB2463511A (en) |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5861777A (en) * | 1997-07-02 | 1999-01-19 | Motorola, Inc. | Method and apparatus for compensation of phase distortion in power amplifiers |
| US6646501B1 (en) * | 2002-06-25 | 2003-11-11 | Nortel Networks Limited | Power amplifier configuration |
| WO2005027342A1 (en) * | 2003-09-15 | 2005-03-24 | Nortel Networks Limited | Power amplifier with improved linearity and efficiency |
| US20050118965A1 (en) * | 2003-12-02 | 2005-06-02 | Matsushita Electric Industrial Co., Ltd. | Signal transmitter |
| WO2005074125A1 (en) * | 2004-01-16 | 2005-08-11 | Qualcomm Incorporated | Amplifier predistortion and autocalibration method and apparatus |
| US20050227644A1 (en) * | 2004-04-09 | 2005-10-13 | Nikolai Maslennikov | Constant gain nonlinear envelope tracking high efficiency linear amplifier |
| EP1672783A1 (en) * | 2004-12-17 | 2006-06-21 | Andrew AG | A transmitter with an envelope tracking power amplifier utilizing digital predistortion of the signal envelope |
| US7091777B2 (en) * | 2002-09-30 | 2006-08-15 | Lucent Technologies Inc. | Controller for an RF power amplifier |
| EP1881597A1 (en) * | 2006-07-21 | 2008-01-23 | MediaTek Inc. | Multilevel LINC transmitter |
| US7340005B2 (en) * | 2003-06-12 | 2008-03-04 | Lg Electronics Inc. | Signal transmission apparatus and method |
| US20080130785A1 (en) * | 2006-12-04 | 2008-06-05 | Raytheon Company | Frequency and temperature dependent pre-distortion |
-
2008
- 2008-09-10 GB GB0817101A patent/GB2463511A/en not_active Withdrawn
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5861777A (en) * | 1997-07-02 | 1999-01-19 | Motorola, Inc. | Method and apparatus for compensation of phase distortion in power amplifiers |
| US6646501B1 (en) * | 2002-06-25 | 2003-11-11 | Nortel Networks Limited | Power amplifier configuration |
| US7091777B2 (en) * | 2002-09-30 | 2006-08-15 | Lucent Technologies Inc. | Controller for an RF power amplifier |
| US7340005B2 (en) * | 2003-06-12 | 2008-03-04 | Lg Electronics Inc. | Signal transmission apparatus and method |
| WO2005027342A1 (en) * | 2003-09-15 | 2005-03-24 | Nortel Networks Limited | Power amplifier with improved linearity and efficiency |
| US20050118965A1 (en) * | 2003-12-02 | 2005-06-02 | Matsushita Electric Industrial Co., Ltd. | Signal transmitter |
| WO2005074125A1 (en) * | 2004-01-16 | 2005-08-11 | Qualcomm Incorporated | Amplifier predistortion and autocalibration method and apparatus |
| US20050227644A1 (en) * | 2004-04-09 | 2005-10-13 | Nikolai Maslennikov | Constant gain nonlinear envelope tracking high efficiency linear amplifier |
| EP1672783A1 (en) * | 2004-12-17 | 2006-06-21 | Andrew AG | A transmitter with an envelope tracking power amplifier utilizing digital predistortion of the signal envelope |
| EP1881597A1 (en) * | 2006-07-21 | 2008-01-23 | MediaTek Inc. | Multilevel LINC transmitter |
| US20080130785A1 (en) * | 2006-12-04 | 2008-06-05 | Raytheon Company | Frequency and temperature dependent pre-distortion |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0817101D0 (en) | 2008-10-29 |
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