US20030210751A1 - Radio frequency transmitter and methods thereof - Google Patents
Radio frequency transmitter and methods thereof Download PDFInfo
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- US20030210751A1 US20030210751A1 US10/463,611 US46361103A US2003210751A1 US 20030210751 A1 US20030210751 A1 US 20030210751A1 US 46361103 A US46361103 A US 46361103A US 2003210751 A1 US2003210751 A1 US 2003210751A1
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- 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
- H03F1/0294—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers using vector summing of two or more constant amplitude phase-modulated signals
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- 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
-
- 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
- H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
- H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B2001/0408—Circuits with power amplifiers
- H04B2001/045—Circuits with power amplifiers with means for improving efficiency
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
Definitions
- FIG. 1 is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to an embodiment of the present invention
- FIGS. 2A and 2B are schematic illustrations of signal space diagrams, helpful in understanding the present invention.
- FIG. 3 is a schematic block-diagram illustration of an exemplary up-conversion chain, according to an embodiment of the present invention
- FIGS. 4A, 4B and 4 C are exemplary graphical illustrations of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 and of a conventional class-B power amplifier as a function of the instantaneous output signal power due to the amplitude of the modulating signal;
- FIG. 5 is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to another embodiment of the present invention.
- FIG. 6A is an exemplary graphical illustration of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 for a constant envelope signal as a function of the output signal power, according to another embodiment of the present invention.
- FIG. 6B is an exemplary graphical illustration of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 for a non-constant envelope signal as a function of the output signal power, according to a further embodiment of the present invention.
- the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuit disclosed herein may be used in many apparatuses such as in the transmitters of a radio system. Radio systems intended to be included within the scope of the present invention include, by way of example only, cellular radiotelephone communication systems, two-way radio communication systems, one-way pagers, two-way pagers, personal communication systems (PCS), and the like.
- Radio systems intended to be included within the scope of the present invention include, by way of example only, cellular radiotelephone communication systems, two-way radio communication systems, one-way pagers, two-way pagers, personal communication systems (PCS), and the like.
- Types of cellular radiotelephone communication systems intended to be within the scope of the present invention include, although are not limited to, Direct Sequence—Code Division Multiple Access (DS-CDMA) cellular radiotelephone communication systems, Wideband CDMA (WBCDMA) and CDMA2000 cellular radiotelephone systems, Global System for Mobile Communications (GSM) cellular radiotelephone systems, North American Digital Cellular (NADC) cellular radiotelephone systems, Time Division Multiple Access (TDMA) systems, Enhanced Data for GSM Evolution (EDGE) and Universal Mobile Telecommuniuications Systems (UMTS).
- DS-CDMA Direct Sequence—Code Division Multiple Access
- WBCDMA Wideband CDMA
- CDMA2000 Code Division Multiple Access
- GSM Global System for Mobile Communications
- NADC North American Digital Cellular
- TDMA Time Division Multiple Access
- EDGE Enhanced Data for GSM Evolution
- UMTS Universal Mobile Telecommuniuications Systems
- An RF transmitter 100 may comprise a digital signal processor (DSP) 102 , baseband (BB) to RF up-conversion chains 104 and 106 , RF preamplifiers 108 and 110 , a power amplifier 112 , an antenna 114 and a controller 116 .
- DSP digital signal processor
- BB baseband
- a BB input signal 118 may be provided to DSP 102 , which may convert it into two constant envelope vectors according to a method which will be described hereinbelow with respect to FIGS. 2A and 2B.
- the first constant envelope vector may be represented by baseband signals I 1 and Q 1
- the second constant envelope vector may be represented by baseband signals I 2 and Q 2 .
- Up-conversion chain 104 may convert signals I 1 and Q 1 into an RF signal RF 1 ; similarly up-conversion chain 106 may convert signals I 2 and Q 2 into an RF signal RF 2 .
- RF signals RF 1 and RF 2 have a common carrier frequency.
- An exemplary embodiment of up-conversion chains 104 and 106 is described hereinbelow with respect to FIG. 3, although the present invention is in no way limited to this particular exemplary embodiment.
- RF preamplifier 108 which has a variable gain, may amplify signal RF 1 to produce a signal RF IN-1 ; similarly RF preamplifier 110 , which has a variable gain, may amplify signal RF 2 to produce a signal RF IN-2 .
- Power amplifier 112 which may have reactive termination, may amplify and combine RF IN-1 and RF IN-2 to produce an output signal RF OUT for transmission by antenna 114 .
- Power amplifier 112 may comprise two branch amplifiers 120 and 122 connected in parallel, and shunt reactance elements 124 and 126 at the output of branch amplifiers 120 and 122 , respectively.
- B S denotes the shunt reactance of element 124
- ⁇ B S denotes the shunt reactance of element 126 .
- the efficiency of power amplifier 112 at a specific output signal power may be improved by adjusting the shunt reactance B S .
- Power amplifier 112 may also comprise a transmission-line-coupler 128 for combining the outputs of branch amplifiers 120 and 122 .
- Transmission-line-coupler 128 may comprise two transmission lines 130 and 132 connected to antenna 114 so that the sum of the branch currents goes through the load.
- Other combiner schemes yielding the same performance may be implemented instead, namely hybrid BALUN, center tap inductor, etc.
- Controller 116 may receive as input a targeted average output signal power level P.
- Targeted average output signal power level P may be selected from a range of power levels or may be selected from a discrete set of at least two power levels.
- Controller 116 may provide data related to P to any of DSP 102 , up-conversion chains 104 and 106 , and RF preamplifiers 108 and 110 , with the result that power amplifier 112 may produce an output signal whose average power is substantially equivalent to P.
- FIGS. 2A and 2B are schematic illustrations of signal space diagrams.
- the horizontal axis of the diagram represents the real (in-phase) component of a signal vector, while the vertical axis of the diagram represents the imaginary (quadrature) component.
- FIG. 2A Three concentric circles, 202 , 204 and 206 , are shown in FIG. 2A.
- a vector 208 from the center of the diagram to the largest circle 206 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal having a maximal instantaneous output signal power.
- This maximal instantaneous output signal power may be determined both by the maximum amplitude A MAX of input signal 118 (FIG. 1) and by the maximum average power P MAX that power amplifier 112 may be able to produce.
- a vector 210 from the center of the diagram to circle 202 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal at an instantaneous output signal power that may be determined both by the minimum amplitude A MIN of input signal 118 and by an average output signal power level P TH , the determination of which will be explained hereinbelow.
- controller 116 may provide DSP 102 with ⁇ (P) so that DSP 102 may represent a baseband vector 212 by two constant envelope vectors 214 and 216 . Since baseband vector 212 has an average amplitude controlled by ⁇ (P), baseband vector 212 may result, after up-conversion and amplification, in a signal at an average output signal power P and at an instantaneous output signal power determined both by the instantaneous amplitude A (t) of input signal 118 and by the targeted average output signal power level P.
- the radius of circle 204 is predetermined both by the maximum amplitude A MAX and by ⁇ (P MAX ).
- the data flow from controller 116 to DSP 102 is indicated in FIG. 1 by line 133 , and constant envelope vectors 214 and 216 are represented by the signals I 1 and Q 1 and I 2 and Q 2 , respectively.
- BB input signal 118 at time t is denoted s(t), with the real (in-phase) component denoted I(t) and the imaginary (quadratire) component denoted Q(t), then the following decomposition holds:
- a ⁇ ( t ) I 2 ⁇ ( t ) + Q 2 ⁇ ( t ) .
- I 2 ⁇ ( t ) ⁇ ⁇ ( P ) ⁇ ( I ⁇ ( t ) + Q ⁇ ( t ) ⁇ ⁇ ⁇ ( P MAX ) ⁇ A MAX 2 ⁇ ⁇ ( P ) ⁇ A 2 ⁇ ( t ) - 1 ) , (Eq.
- controller 116 may provide predetermined, fixed values to any amplification elements of up-conversion chains 104 and 106 and to RF preamplifiers 108 and 110 .
- the data flow from controller 116 to up-conversion chains 104 and 106 are indicated in FIG. 1 by lines 134 and 136 , respectively.
- Lines 138 and 140 indicate the data flow from controller 116 to RF preamplifiers 108 and 110 , respectively.
- FIG. 2B Three concentric circles, 202 , 204 and 218 , are shown in FIG. 2B. Circles 202 and 204 are the same or similar to those shown in FIG. 2A.
- a vector 220 from the center of the diagram to circle 218 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal at an instantaneous output signal power that may be determined both by the maximum amplitude A MAX , of input signal 118 (FIG. 1) and by the average output signal power level P TH .
- controller 116 may provide DSP 102 with the power ⁇ (P TH ) so that DSP 102 may represent a baseband vector 222 by two constant envelope vectors 224 and 226 , where the size of constant envelope 204 is the same or similar to that used in FIG. 2A.
- Constant envelope vectors 224 and 226 may be represented by signals I 1 and Q 1 , and I 2 and Q 2 , respectively, where Equations 1A, 1B, 2A and 2B are used with ⁇ (P TH in place of ⁇ (P).
- controller 116 may reduce the amplitudes of signals I 1 and Q 1 , and I 2 and Q 2 , or may reduce the gain of any of variable amplification elements in up-conversion chains 104 and 106 and RF preamplifiers 108 and 110 , or a combination thereof, with the result that power amplifier 112 may produce an output signal whose average power is substantially equivalent to P.
- the predetermined average output signal power level P TH may act as a threshold between two modes of operation of the RF transmitter, according to some embodiments of the present invention.
- the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of a baseband input signal and from the targeted average output signal power level P, and by up-converting at a fixed gain.
- the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of the baseband input signal and from the predetermined average output signal power level P TH , and by up-converting at a variable gain which is dependent on the targeted average output signal power level P and which is lower than the fixed gain of the first mode.
- the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of the baseband input signal and from the predetermined average output signal power level P TH , and whose amplitudes have been reduced in the baseband according to the targeted average output signal power level P, so that the average power of the output signal is substantially equivalent to the targeted average output signal power level P.
- FIG. 3 is a schematic block-diagram illustration of an exemplary up-conversion chain, according to an embodiment of the present invention.
- the up-conversion chain may comprise an intermediate frequency (IF) local oscillator (LO) 300 and an RF local oscillator 302 , IQ modulators 304 and 306 , and phase lock loops (PLL) 308 and 310 .
- IF intermediate frequency
- LO local oscillator
- PLL phase lock loops
- IQ modulator 304 may comprise mixers 312 and 314 and combiner 316 .
- Mixer 312 may receive as input I 1 and sin( ⁇ 1F t), where ⁇ 1F denotes the frequency generated by IF LO 300 and t denotes time.
- Mixer 314 may receive as input Q 1 and cos( ⁇ 1F t).
- Combiner 316 may combine the outputs of mixers 312 and 314 , and provides the combination to PLL 308 .
- IQ modulator 306 may comprise mixers 318 and 320 and combiner 322 .
- Mixer 318 may receive as input I 2 and sin( ⁇ 1F t).
- Mixer 320 may receive as input Q 2 and cos( ⁇ 1F t).
- Combiner 322 may combine the outputs of mixers 318 and 320 , and provides the combination to PLL 310 .
- PLL 308 may comprise a phase detector (PD) 324 , a loop filter 326 and a voltage-controlled oscillator (VCO) 328 .
- PLL 308 may also comprise a mixer 330 , mixing the output of VCO 328 with the signal produced by RF LO 302 , and providing an IF modulated signal to PD 324 .
- PLL 310 may comprise a PD 334 , a loop filter 336 and a VCO 338 .
- PLL 310 may also comprise a mixer 340 , mixing the output of VCO 338 with the signal produced by RF LO 302 , and providing an IF modulated signal to PD 334 .
- the up-conversion chain may comprise variable amplifiers (not shown) that amplify the input signals I 1 and Q 1 , and I 2 and Q 2 , prior to their modulation by IQ modulators 304 and 306 , respectively.
- the gain of these variable amplifiers may be reduced by controller 116 (not shown) when the targeted average output signal power level P is less than the predetermined power level P TH .
- FIGS. 4A, 4B and 4 C are exemplary graphical illustrations of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 (indicated by a solid line) and of a conventional class-B power amplifier (indicated by a dotted line) as a function of the output signal power.
- the average output signal power (indicated by a circle) is P MAX
- the instantaneous output signal power (indicated by the solid and dotted lines) varies according to the amplitude of the input signal.
- the average output signal power is P TH
- FIG. 4C the average output signal power is less than P TH .
- the average current consumption of the RF transmitter of FIG. 1 may be appreciably improved with respect to that of class-B power amplifiers.
- P TH is chosen to be the average output signal power at which the efficiency has a peak value.
- the threshold P TH may be chosen by minimizing the current consumption according to the output signal power probability distribution and the amplitude distribution of the baseband input signal.
- FIG. 5 is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to another embodiment of the present invention.
- An RF transmitter 500 may comprise DSP 102 , RF preamplifiers 108 and 110 , power amplifier 112 , antenna 114 and controller 116 . As in FIG. 1, BB input signal 118 may be provided to DSP 102 . RF transmitter 500 may also comprise IF local oscillator 300 , RF local oscillator 302 , IQ modulators 304 and 306 , and PLLs 308 and 310 .
- RF transmitter 500 may also comprise a feedback path to compensate for circuit imperfections that may occur in an open loop arrangement such as that of FIG. 1.
- DSP 102 may comprise a compensation module 502 .
- a small portion of the transmitted signal RF OUT may be taken through a directional coupler 504 via a step attenuator 506 .
- the state of step attenuator 506 may be controlled by controller 116 , as indicated by line 507 , in order to divide the entire dynamic range into several smaller regions.
- the output of step attenuator 506 passes through an image rejection mixer (IRM) 508 .
- IRM 508 down-converts the RF signal to IF.
- IRM 508 may receive as input, in addition to the RF signal, a signal from RF local oscillator 302 .
- the IF signal produced by IRM 508 may be demodulated by an I/Q demodulator 510 , which may receive as input a signal from IF local oscillator 300 .
- I/Q demodulator 510 may produce feedback signals I FB and Q FB , which may be provided to DSP 102 through analog-to-digital converters (not shown).
- controller 116 may provide DSP 102 with a power level ⁇ .
- a power level ⁇ As explained hereinabove, when the targeted average output signal power level P is in a first range of average output signal power levels, i.e. between P MAX and P TH , then the power level ⁇ is related to the targeted average output signal power level P. When the targeted average output signal power level P is in a second range of average output signal power levels, i.e. less than P TH , then the power level ⁇ is related to the predetermined average output signal power level P TH .
- Compensation module 502 may compare the input signal 118 , the feedback signals I FB and Q FB , the power level ⁇ and the state 507 of step attenuator 506 to create the compensated baseband signals I 1 and Q 1 , and I 2 and Q 2 .
- RF transmitter 500 may also comprise a power level measurement unit 512 that may take a small portion of the output of step attenuator 506 through a directional coupler 514 .
- Power level measurement unit 512 may provide a measured power level P FB to controller 116 .
- Controller 116 may compare the targeted output signal power level with measured power level P FB in order to set the targeted amplification values for RF preamplifiers 108 and 110 and for the amplification elements in the up-conversion chains.
- FIG. 6A an exemplary graphical illustration of the efficiency of the radio frequency transmitter of FIG. 1 as a function of the output signal power is shown in FIG. 6A, to which reference is now made.
- the efficiency has a peak at two output signal powers.
- the predetermined average output signal power level P TH may be set to be close to the lower of these output signal powers having a peak efficiency.
- the amplitudes of baseband signals I 1 and Q 1 , and I 2 and Q 2 are determined from the instantaneous amplitude A(t) of baseband input signal 118 , and the relative phase differences of baseband signals I 1 and Q 1 , and I 2 and Q 2 , are determined from the targeted output signal power.
- the average efficiency of the radio frequency transmitter of FIG. 1 for this embodiment as a function of the output signal power is shown in FIG. 6B.
Abstract
In one embodiment, the present invention provides a radio frequency transmitter that may have a processor and a controller that reduce current consumption of the power amplifier of the radio frequency transmitter.
Description
- This application is a continuation of U.S. patent application Ser. No. 09/769,444, filed on Jan. 26, 2001, now U.S. Pat. No. 6,587,511, issued on Jul. 1, 2003.
- Modern systems enable radio transmitters to transmit at reduced power for long periods of time. The modulating signal of these transmissions may have large peak-to-minimum amplitude variations. Since the efficiency of power amplifiers is generally reduced at less-than-maximum power levels, these two factors may increase the average current consumption of power amplifiers in radio transmitters.
- There is a continuing need to reduce the current consumption of power amplifiers in radio transmitters.
- The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:
- FIG. 1 is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to an embodiment of the present invention;
- FIGS. 2A and 2B are schematic illustrations of signal space diagrams, helpful in understanding the present invention;
- FIG. 3 is a schematic block-diagram illustration of an exemplary up-conversion chain, according to an embodiment of the present invention;
- FIGS. 4A, 4B and4C are exemplary graphical illustrations of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 and of a conventional class-B power amplifier as a function of the instantaneous output signal power due to the amplitude of the modulating signal;
- FIG. 5 is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to another embodiment of the present invention;
- FIG. 6A is an exemplary graphical illustration of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 for a constant envelope signal as a function of the output signal power, according to another embodiment of the present invention; and
- FIG. 6B is an exemplary graphical illustration of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 for a non-constant envelope signal as a function of the output signal power, according to a further embodiment of the present invention.
- It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
- In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
- It should be understood that the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuit disclosed herein may be used in many apparatuses such as in the transmitters of a radio system. Radio systems intended to be included within the scope of the present invention include, by way of example only, cellular radiotelephone communication systems, two-way radio communication systems, one-way pagers, two-way pagers, personal communication systems (PCS), and the like.
- Types of cellular radiotelephone communication systems intended to be within the scope of the present invention include, although are not limited to, Direct Sequence—Code Division Multiple Access (DS-CDMA) cellular radiotelephone communication systems, Wideband CDMA (WBCDMA) and CDMA2000 cellular radiotelephone systems, Global System for Mobile Communications (GSM) cellular radiotelephone systems, North American Digital Cellular (NADC) cellular radiotelephone systems, Time Division Multiple Access (TDMA) systems, Enhanced Data for GSM Evolution (EDGE) and Universal Mobile Telecommuniuications Systems (UMTS).
- Reference is now made to FIG. 1, in which an exemplary radio frequency (RF) transmitter in accordance with an embodiment of the present invention is described. An
RF transmitter 100 may comprise a digital signal processor (DSP) 102, baseband (BB) to RF up-conversion chains RF preamplifiers power amplifier 112, anantenna 114 and acontroller 116. - A
BB input signal 118 may be provided toDSP 102, which may convert it into two constant envelope vectors according to a method which will be described hereinbelow with respect to FIGS. 2A and 2B. For example, the first constant envelope vector may be represented by baseband signals I1 and Q1, while the second constant envelope vector may be represented by baseband signals I2 and Q2. Up-conversion chain 104 may convert signals I1 and Q1 into an RF signal RF1; similarly up-conversion chain 106 may convert signals I2 and Q2 into an RF signal RF2. RF signals RF1 and RF2 have a common carrier frequency. An exemplary embodiment of up-conversion chains -
RF preamplifier 108, which has a variable gain, may amplify signal RF1 to produce a signal RFIN-1; similarlyRF preamplifier 110, which has a variable gain, may amplify signal RF2 to produce a signal RFIN-2.Power amplifier 112, which may have reactive termination, may amplify and combine RFIN-1 and RFIN-2 to produce an output signal RFOUT for transmission byantenna 114. -
Power amplifier 112 may comprise twobranch amplifiers shunt reactance elements branch amplifiers element 124 and −BS denotes the shunt reactance ofelement 126. The efficiency ofpower amplifier 112 at a specific output signal power may be improved by adjusting the shunt reactance BS. Power amplifier 112 may also comprise a transmission-line-coupler 128 for combining the outputs ofbranch amplifiers coupler 128 may comprise twotransmission lines antenna 114 so that the sum of the branch currents goes through the load. Other combiner schemes yielding the same performance may be implemented instead, namely hybrid BALUN, center tap inductor, etc. -
Controller 116 may receive as input a targeted average output signal power level P. Targeted average output signal power level P may be selected from a range of power levels or may be selected from a discrete set of at least two power levels.Controller 116 may provide data related to P to any ofDSP 102, up-conversion chains RF preamplifiers power amplifier 112 may produce an output signal whose average power is substantially equivalent to P. The operation ofcontroller 116 and DSP 102 is better understood if reference is made additionally to FIGS. 2A and 2B, which are schematic illustrations of signal space diagrams. The horizontal axis of the diagram represents the real (in-phase) component of a signal vector, while the vertical axis of the diagram represents the imaginary (quadrature) component. - Three concentric circles,202, 204 and 206, are shown in FIG. 2A. A
vector 208 from the center of the diagram to thelargest circle 206 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal having a maximal instantaneous output signal power. This maximal instantaneous output signal power may be determined both by the maximum amplitude AMAX of input signal 118 (FIG. 1) and by the maximum average power PMAX thatpower amplifier 112 may be able to produce. Similarly, avector 210 from the center of the diagram tocircle 202 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal at an instantaneous output signal power that may be determined both by the minimum amplitude AMIN ofinput signal 118 and by an average output signal power level PTH, the determination of which will be explained hereinbelow. - According to some embodiments of the present invention, when the targeted average output signal power level P is between PMAX and PTH,
controller 116 may provide DSP 102 with ρ(P) so that DSP 102 may represent abaseband vector 212 by twoconstant envelope vectors baseband vector 212 has an average amplitude controlled by ρ(P),baseband vector 212 may result, after up-conversion and amplification, in a signal at an average output signal power P and at an instantaneous output signal power determined both by the instantaneous amplitude A (t) ofinput signal 118 and by the targeted average output signal power level P. - The radius of
circle 204 is predetermined both by the maximum amplitude AMAX and by ρ(PMAX). The data flow fromcontroller 116 toDSP 102 is indicated in FIG. 1 byline 133, andconstant envelope vectors - If
BB input signal 118 at time t is denoted s(t), with the real (in-phase) component denoted I(t) and the imaginary (quadratire) component denoted Q(t), then the following decomposition holds: - s(t)=I(t)+jQ(t)
-
-
-
-
-
-
- It will also be appreciated by persons of ordinary skill in the art that the relative phase differences of these signals are determined from the instantaneous amplitude of
input signal 118 and from the targeted average output signal power level P. Clearly the present invention is not limited in any way to the exemplary equations given hereinabove in Equations 1A, 1B, 2A and 2B. Rather, any other set of equations yielding a constant envelope signal represented by signals I1 and Q1, and a constant envelope signal represented by signals I2 and Q2, is clearly also within the scope of the present invention. - According to some embodiments of the present invention, when the targeted average output signal power level P is between PMAX and PTH,
controller 116 may provide predetermined, fixed values to any amplification elements of up-conversion chains RF preamplifiers controller 116 to up-conversion chains lines Lines controller 116 toRF preamplifiers - Three concentric circles,202, 204 and 218, are shown in FIG. 2B.
Circles vector 220 from the center of the diagram tocircle 218 represents the amplitude and phase of a BB signal, which after up-conversion and amplification may produce a signal at an instantaneous output signal power that may be determined both by the maximum amplitude AMAX, of input signal 118 (FIG. 1) and by the average output signal power level PTH. - According to some embodiments of the present invention, when the targeted average output signal power level P is less than PTH,
controller 116 may provideDSP 102 with the power ρ(PTH) so thatDSP 102 may represent abaseband vector 222 by twoconstant envelope vectors constant envelope 204 is the same or similar to that used in FIG. 2A.Constant envelope vectors baseband vector 222, after up-conversion and amplification at fixed gain values, would produce an output signal at an average output signal power, which may be determined both by the instantaneous amplitude A(t) ofinput signal 118 and by the predetermined power level PTH, and which is higher than the targeted average output signal power level P. Therefore,controller 116 may reduce the amplitudes of signals I1 and Q1, and I2 and Q2, or may reduce the gain of any of variable amplification elements in up-conversion chains RF preamplifiers power amplifier 112 may produce an output signal whose average power is substantially equivalent to P. - The predetermined average output signal power level PTH may act as a threshold between two modes of operation of the RF transmitter, according to some embodiments of the present invention. In one mode, the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of a baseband input signal and from the targeted average output signal power level P, and by up-converting at a fixed gain. In another mode, the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of the baseband input signal and from the predetermined average output signal power level PTH, and by up-converting at a variable gain which is dependent on the targeted average output signal power level P and which is lower than the fixed gain of the first mode. Alternatively, in this other mode, the RF transmitter may control the instantaneous output signal power by combining constant envelope signals whose relative phase differences are determined from the instantaneous amplitude of the baseband input signal and from the predetermined average output signal power level PTH, and whose amplitudes have been reduced in the baseband according to the targeted average output signal power level P, so that the average power of the output signal is substantially equivalent to the targeted average output signal power level P.
- Reference is now made to FIG. 3, which is a schematic block-diagram illustration of an exemplary up-conversion chain, according to an embodiment of the present invention. The up-conversion chain may comprise an intermediate frequency (IF) local oscillator (LO)300 and an RF
local oscillator 302,IQ modulators -
IQ modulator 304 may comprisemixers combiner 316.Mixer 312 may receive as input I1 and sin(ω1Ft), where ω1F denotes the frequency generated byIF LO 300 and t denotes time.Mixer 314 may receive as input Q1 and cos(ω1Ft).Combiner 316 may combine the outputs ofmixers PLL 308. Similarly,IQ modulator 306 may comprisemixers combiner 322.Mixer 318 may receive as input I2 and sin(ω1Ft).Mixer 320 may receive as input Q2 and cos(ω1Ft).Combiner 322 may combine the outputs ofmixers PLL 310. -
PLL 308 may comprise a phase detector (PD) 324, aloop filter 326 and a voltage-controlled oscillator (VCO) 328.PLL 308 may also comprise amixer 330, mixing the output ofVCO 328 with the signal produced byRF LO 302, and providing an IF modulated signal toPD 324. Similarly,PLL 310 may comprise aPD 334, aloop filter 336 and aVCO 338.PLL 310 may also comprise amixer 340, mixing the output ofVCO 338 with the signal produced byRF LO 302, and providing an IF modulated signal toPD 334. - Alternatively, the up-conversion chain may comprise variable amplifiers (not shown) that amplify the input signals I1 and Q1, and I2 and Q2, prior to their modulation by
IQ modulators - Reference is now made to FIGS. 4A, 4B and4C, which are exemplary graphical illustrations of the instantaneous efficiency of the radio frequency transmitter of FIG. 1 (indicated by a solid line) and of a conventional class-B power amplifier (indicated by a dotted line) as a function of the output signal power. In FIG. 4A the average output signal power (indicated by a circle) is PMAX, and the instantaneous output signal power (indicated by the solid and dotted lines) varies according to the amplitude of the input signal. In FIG. 4B the average output signal power is PTH, and in FIG. 4C the average output signal power is less than PTH. The average current consumption of the RF transmitter of FIG. 1 may be appreciably improved with respect to that of class-B power amplifiers.
- As shown in the exemplary graphical illustrations of FIGS. 4B and 4C, PTH is chosen to be the average output signal power at which the efficiency has a peak value. However, it will be appreciated that there are many other ways to select the threshold PTH, all of which are included in the scope of the present invention. For example, the threshold PTH may be chosen by minimizing the current consumption according to the output signal power probability distribution and the amplitude distribution of the baseband input signal.
- Reference is now made to FIG. 5, which is a schematic block-diagram illustration of an exemplary radio frequency transmitter, according to another embodiment of the present invention.
- An
RF transmitter 500 may compriseDSP 102,RF preamplifiers power amplifier 112,antenna 114 andcontroller 116. As in FIG. 1,BB input signal 118 may be provided toDSP 102.RF transmitter 500 may also comprise IFlocal oscillator 300, RFlocal oscillator 302,IQ modulators PLLs -
RF transmitter 500 may also comprise a feedback path to compensate for circuit imperfections that may occur in an open loop arrangement such as that of FIG. 1. In this embodiment,DSP 102 may comprise acompensation module 502. A small portion of the transmitted signal RFOUT may be taken through adirectional coupler 504 via astep attenuator 506. The state ofstep attenuator 506 may be controlled bycontroller 116, as indicated byline 507, in order to divide the entire dynamic range into several smaller regions. The output ofstep attenuator 506 passes through an image rejection mixer (IRM) 508.IRM 508 down-converts the RF signal to IF.IRM 508 may receive as input, in addition to the RF signal, a signal from RFlocal oscillator 302. The IF signal produced byIRM 508 may be demodulated by an I/Q demodulator 510, which may receive as input a signal from IFlocal oscillator 300. I/Q demodulator 510 may produce feedback signals IFB and QFB, which may be provided toDSP 102 through analog-to-digital converters (not shown). - As indicated by
line 133,controller 116 may provideDSP 102 with a power level ρ. As explained hereinabove, when the targeted average output signal power level P is in a first range of average output signal power levels, i.e. between PMAX and PTH, then the power level ρ is related to the targeted average output signal power level P. When the targeted average output signal power level P is in a second range of average output signal power levels, i.e. less than PTH, then the power level ρ is related to the predetermined average output signal power level PTH. -
Compensation module 502 may compare theinput signal 118, the feedback signals IFB and QFB, the power level ρ and thestate 507 ofstep attenuator 506 to create the compensated baseband signals I1 and Q1, and I2 and Q2. -
RF transmitter 500 may also comprise a powerlevel measurement unit 512 that may take a small portion of the output ofstep attenuator 506 through adirectional coupler 514. Powerlevel measurement unit 512 may provide a measured power level PFB tocontroller 116.Controller 116 may compare the targeted output signal power level with measured power level PFB in order to set the targeted amplification values forRF preamplifiers -
-
-
-
-
- That is, their amplitude depends on the amplitude of the input signal and the maximal average output signal power and does not depend on the average output signal power. These signals are constant envelope signals only if the input signal is a constant envelope signal. It will also be appreciated by persons of ordinary skill in the art that the relative phase differences of these signals are determined from the targeted average output signal power and not from the instantaneous amplitude of
input signal 118. - According to this embodiment, if the amplitude of
baseband input signal 118 is constant, an exemplary graphical illustration of the efficiency of the radio frequency transmitter of FIG. 1 as a function of the output signal power is shown in FIG. 6A, to which reference is now made. The efficiency has a peak at two output signal powers. The predetermined average output signal power level PTH may be set to be close to the lower of these output signal powers having a peak efficiency. - If the amplitude of
baseband input signal 118 is not constant, the amplitudes of baseband signals I1 and Q1, and I2 and Q2, are determined from the instantaneous amplitude A(t) ofbaseband input signal 118, and the relative phase differences of baseband signals I1 and Q1, and I2 and Q2, are determined from the targeted output signal power. The average efficiency of the radio frequency transmitter of FIG. 1 for this embodiment as a function of the output signal power is shown in FIG. 6B. - While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
Claims (1)
1. A method comprising:
when a targeted power level is below a predetermined power level:
generating baseband signals having relative phase differences, said relative phase differences determined from an instantaneous amplitude of an input signal and from said predetermined power level, the amplitude of said baseband signals being determined, at least in part, from said targeted power level; and
combining signals derived from said generated signals into an output signal having an average power that is substantially equivalent to said targeted power level, said derived signals having a common carrier frequency.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US10/463,611 US20030210751A1 (en) | 2001-01-26 | 2003-06-18 | Radio frequency transmitter and methods thereof |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/769,444 US6587511B2 (en) | 2001-01-26 | 2001-01-26 | Radio frequency transmitter and methods thereof |
US10/463,611 US20030210751A1 (en) | 2001-01-26 | 2003-06-18 | Radio frequency transmitter and methods thereof |
Related Parent Applications (1)
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US09/769,444 Continuation US6587511B2 (en) | 2001-01-26 | 2001-01-26 | Radio frequency transmitter and methods thereof |
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US20030210751A1 true US20030210751A1 (en) | 2003-11-13 |
Family
ID=25085464
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US09/769,444 Expired - Lifetime US6587511B2 (en) | 2001-01-26 | 2001-01-26 | Radio frequency transmitter and methods thereof |
US10/463,611 Abandoned US20030210751A1 (en) | 2001-01-26 | 2003-06-18 | Radio frequency transmitter and methods thereof |
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US09/769,444 Expired - Lifetime US6587511B2 (en) | 2001-01-26 | 2001-01-26 | Radio frequency transmitter and methods thereof |
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US (2) | US6587511B2 (en) |
CN (1) | CN1529946B (en) |
AU (1) | AU2002225305A1 (en) |
GB (1) | GB2389491B (en) |
TW (1) | TW561700B (en) |
WO (1) | WO2002060072A2 (en) |
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US20050136864A1 (en) * | 2003-12-17 | 2005-06-23 | Eliav Zipper | Radio frequency modulator and methods thereof |
US7356315B2 (en) | 2003-12-17 | 2008-04-08 | Intel Corporation | Outphasing modulators and methods of outphasing modulation |
US20080129386A1 (en) * | 2003-12-17 | 2008-06-05 | Eliav Zipper | Radio frequency modulator and methods thereof |
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WO2006039109A3 (en) * | 2004-09-30 | 2006-07-13 | Motorola Inc | Method and system for dynamic range power control |
US20080031384A1 (en) * | 2006-08-04 | 2008-02-07 | Yoshihiro Hara | Transmission circuit and communication device |
US7940859B2 (en) * | 2006-08-04 | 2011-05-10 | Panasonic Corporation | Transmission circuit and communication device |
Also Published As
Publication number | Publication date |
---|---|
GB2389491B (en) | 2004-10-13 |
AU2002225305A1 (en) | 2002-08-06 |
GB2389491A (en) | 2003-12-10 |
US6587511B2 (en) | 2003-07-01 |
CN1529946A (en) | 2004-09-15 |
WO2002060072A3 (en) | 2003-04-17 |
US20020131521A1 (en) | 2002-09-19 |
WO2002060072A2 (en) | 2002-08-01 |
TW561700B (en) | 2003-11-11 |
GB0318026D0 (en) | 2003-09-03 |
CN1529946B (en) | 2013-11-06 |
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