CN105897188A - Method and system for nonlinear correction of power amplifier - Google Patents
Method and system for nonlinear correction of power amplifier Download PDFInfo
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- H—ELECTRICITY
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- 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
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
- H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
- H03F3/195—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only in integrated circuits
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- 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
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Abstract
The invention relates to a method and a system for nonlinear correction of a radio frequency power amplifier. The method comprises the following steps of: S1. carrying out negative feedback correction on an input signal according to a feedback signal and outputting a negative feedback signal; S2. carrying out pre-distortion correction on the negative feedback signal and outputting the signal subjected to pre-distortion to the radio frequency power amplifier; and S3. collecting the signal amplified through the radio frequency power amplifier, generating the feedback signal and returning to the step S1. The method and the system for nonlinear correction of the radio frequency power amplifier adopt a method of combining the pre-distortion correction and closed-loop negative feedback correction, and are realized in a digital domain; and in comparison with a conventional nonlinear correction method, the correction effect is more accurate, the dependence on a device is smaller and the system is more stable.
Description
Technical field
The present invention relates generally to power amplifier, particularly relate to the non-linear correction method of magnetic nuclear resonance radio frequency power amplifier, and correction system.
Background technology
In magnetic resonance system, input low level signal amplification is mainly high-power radiofrequency signal by radio-frequency power amplifier, it is provided that to radio-frequency coil, thus produce radio-frequency (RF) excited for imaging.For obtaining high-quality magnetic resonance image (MRI), it is good linear that magnetic resonance system requires that radio frequency has in bigger dynamic range.But radio-frequency power amplifier itself is nonlinear device, there is bigger non-linear distortion in output signal, is in particular in that the gain of radio-frequency power amplifier and phase place change along with the change of signal input power.Accordingly, it would be desirable to take way that the non-linear of radio-frequency power amplifier is processed.Figure 1 With 2Respectively illustrate the gain of radio-frequency power amplifier and curve that phase place changes with input power.
Additionally, the output of magnetic resonance radio frequency power amplifier is the biggest, sometimes up to more than tens of kilowatt level, when the band of operation of magnetic resonance radio frequency signal uses, the power tube junction temperature used by radio-frequency power amplifier can be caused to raise, thus cause the gain of radio-frequency power amplifier and phase place to change.This phenomenon is referred to as the hot memory effect of radio-frequency power amplifier.In the case of input signal envelope is constant, the envelope of output signal can elapse over time and progressively decline, and this is that the power tube junction temperature rising used by radio-frequency power amplifier causes the gain of this radio-frequency power amplifier to change the most therewith.
Therefore, owing to radio-frequency power amplifier is originally as nonlinear device, and the hot memory effect of radio-frequency power amplifier so that there is bigger non-linear distortion in the output signal of radio-frequency power amplifier, in order to ensure the quality of magnetic resonance image (MRI), it is necessary to solve above-mentioned nonlinear problem.
Summary of the invention
In order to solve the problems referred to above, the present invention provides a kind of method of radio-frequency power amplifier gamma correction, and described method includes:
S1: according to feedback signal, input signal is carried out negative feedback correction, export negative-feedback signal；
S2: described negative-feedback signal is carried out predistortion correction, exports predistorted signal to described radio-frequency power amplifier；
S3: gather the signal amplified through described radio-frequency power amplifier, and generate described feedback signal, be then back to step S1.
Optionally, described input signal includes digital medium-frequency signal or digital baseband signal.
Optionally, described step S1 farther includes: asks for the difference of input signal and feedback signal, and is corrected the negative feedback of input signal by PID control realization.
Optionally, previously according to described input signal and described feedback signal, parameter Kp, Ti, Td of PID are adjusted.
Optionally, described step S1 farther includes, and asks for the difference of input signal and feedback signal, and realizes the correction of the negative feedback to input signal by multiphase filter.
Optionally, described negative-feedback signal carry out predistortion correction include power based on radio-frequency power amplifier and/or phase place with input power change curve generate look-up table described negative-feedback signal is compensated.
Optionally, the described feedback signal of described generation, including: the signal amplified through described radio-frequency power amplifier collected is coupled as radiofrequency signal by a small margin.
Optionally, described negative feedback correction and/or predistortion correction realize in numeric field.
The present invention also provides for a kind of radio-frequency power amplifier gamma correction system, including:
Feedback controller, carries out negative feedback correction according to feedback signal to the signal being input to described feedback controller；
Predistorter, carries out predistortion correction to the signal being input to described predistorter；
Radio-frequency power amplifier, for carrying out power amplification to the signal through negative feedback correction and predistortion correction；And
Signal acquisition module, gathers the signal through power amplification, and generates feedback signal output to described feedback controller.
Optionally, described feedback controller farther includes PID controller or multiphase filter, according to described feedback signal and the difference of the described signal being input to feedback controller, is corrected the described signal being input to feedback controller.
The method and system of the radio-frequency power amplifier gamma correction of the present invention, have employed predistortion correction and close loop negative feedback corrects the method combined, wherein predistortion correction for realize due to power amplifier self-characteristic cause non-linear, and close loop negative feedback be mainly used in due to heat or other factors cause non-linear.And trimming process realizes in numeric field, compared with traditional non-linear correction method, rectification effect is more accurate, and the dependency for device is less, and system is the most stable.
Accompanying drawing explanation
Figure 1The curve that the gain of radio-frequency power amplifier changes with input power is shown.
Figure 2The curve that the phase place of radio-frequency power amplifier changes with input power is shown.
Figure 3Flow process according to the present invention one exemplary embodiment is shownFigure。
Figure 4System frame according to the present invention one exemplary embodiment is shownFigure。
Figure 5Illustrate that the i/q signal that uses according to the present invention one exemplary embodiment carries out the system frame processed as inputFigure。
Figure 6Illustrate that the employing amplitude/phase according to the present invention one exemplary embodiment carries out the system frame processed as inputFigure。
Figure 7Illustrate the predistorter that can process i/q signal according to the present invention one exemplary embodiment realizes example.
Figure 8Illustrate the predistorter that can process amplitude/phase according to the present invention one exemplary embodiment realizes example.
Figure 9Illustrate the feedback controller that can process amplitude/phase according to the present invention one exemplary embodiment realizes example.
Figure 10Illustrate the feedback controller that can process i/q signal according to the present invention one exemplary embodiment realizes example.
Detailed description of the invention
By referenceAccompanying drawingDescribe each embodiment in detail.In place of possible, identicalAccompanying drawingLabelling will pass throughAccompanying drawingFor referring to same or like part.To particular example andAccompanying drawing instituteQuoting of making is for illustrative purposes, and is not intended to limit the scope of the present invention or claim.Wording " exemplary " is used herein to mean that " as example, example or explanation ".Any realization here depicted as " exemplary " is not necessarily to be construed as realizing preferred or advantageous over other.
The present invention is directed to the above-mentioned of prior art and other relate to the nonlinear problem of magnetic resonance radio frequency power amplifier, it is proposed that for the method and system of stabilizing amplifier.The present invention includes at least one in following characteristics or its any combination: use digital signal input；In numeric field, the non-linear of power amplifier is corrected.
Gamma correction of the present invention can mainly include the way using digital pre-distortion and close loop negative feedback to combine.On the one hand in the exemplary embodiment, the solution of the present invention, in numeric field, uses predistortion to be corrected radio-frequency power amplifier with the non-linear of input signal, on the other hand uses negative feedback to carry out system mainly due to thermally-induced and non-linear is corrected.
Below in conjunction with various embodiments of the present invention, technical scheme is explained.It will be understood by those skilled in the art that following exemplary embodiment only provides for ease of description, and beneficial effects of the present invention is not all realized by any single embodiment.Various combinations, revise and replacement is those of ordinary skill in the art and is understood on the basis of the present invention.
Figure 3Illustrate according to the present invention with the method flow of exemplary embodimentFigure.In this exemplary embodiment, comprise the following steps: the method for radio-frequency power amplifier gamma correction, including:
S1: according to feedback signal, input signal is carried out negative feedback correction, export negative-feedback signal；
S2: described negative-feedback signal is carried out predistortion correction, exports predistorted signal to described radio-frequency power amplifier；
S3: gather the signal amplified through described radio-frequency power amplifier, and generate described feedback signal, be then back to step S1.
Below in conjunction with the structure of the system method to this exemplary embodiment, it is illustrated.
Figure 4System frame according to the present invention one exemplary embodiment is shownFigure.In this exemplary embodiment, system 400 can include that derived digital signal 410, feedback controller 420, digital pre-distortion (Digital Pre-Distortion, DPD) device 430, transmitting signal produce digital module 440, launch signal generation analog module 450, radio-frequency power amplifier 460, feedback signal collection analog module 470, feedback signal collection digital module 480 and load 490.
?Figure 4Shown in system in, the input signal that derived digital signal 410 produces can be baseband I/Q two paths of signals or the I/Q two paths of signals being modulated Low Medium Frequency, can also be amplitude (Amp) and phase place (Phase) signal of base band, and loading 490 can be magnetic resonance radio frequency coil etc..
For the non-linear correcting function of radio-frequency power amplifier 460 by including that one or more part following realizes: feedback controller 420, digital predistorter 430, launch signal and produce digital module 440 and launch that signal produces analog module 450, feedback signal gathers digital module 470 and feedback signal gathers analog module 480.
Figure 4Shown in system can receive digital signal, and it can be inputed to together with digital feedback signal feedback controller 420.The exportable signal of feedback controller 420 is to digital predistorter 430, this digital predistorter 430 according to the power of radio-frequency power amplifier and/or phase place with the characteristic relation of input power, produce corresponding predistorted signal, relevant to radio-frequency power amplifier input power non-linear for correction.The object of feedback controller 420 correction can be the cascade of predistortion and power amplifier, this cascade system it is believed that essentially eliminated relevant to input power non-linear by the effect of digital predistorter 430, and therefore feedback controller 420 can be non-linear mainly for cause in heat effect and other factors.
Launch signal generation digital module 440 and the function launching signal generation analog module 450 main is that the digital predistortion signal of input is modulated analog radio frequency (RF) small-signal required for magnetic resonance, and export to radio-frequency power amplifier 460.
Radio-frequency power amplifier 460 carries out power amplification, to produce the high power required for loading coil to the analog radio frequency small-signal of input.Feedback signal gathers analog module 470 and feedback signal gathers digital module 480 and is acquired the radiofrequency signal by a small margin come from radio-frequency power amplifier 460 output coupling, and mixes down to and the base band corresponding to digital input signals or intermediate frequency.
According to further embodiment of the present invention, being I/Q or amplitude/phase for digital input signals to be dealt with, this system can have different implementations.Figure 5WithFigure 6Sets forth in the case of digital input signals to be dealt with is I/Q and digital input signals to be dealt with is that two kinds in the case of amplitude (Amp)/phase place (Phase) realize showing of exampleFigure。
Figure 5Illustrate that the i/q signal that uses according to the present invention one exemplary embodiment carries out the system frame processed as digital input signalsFigure。Figure 5In feedback controller 520 may correspond toFigure 4In feedback controller 420, it receives I/Q_input signal from derived digital signal 510, gathers digital module 580 from feedback signal and receives I/Q_feedback signal, and exports I/Q_feedback_out signal to digital predistorter 530.One exemplary rather than in determinate example, feedback controller 520 can be same or similar with classical cartesian feedback arrangement.
Digital predistorter 530 receives the I/Q_feedback_out from feedback controller 520 as input, and exports I/Q_DPD_out and produce digital module 540 to launching signal.
Figure 5In other parts input/output structure withFigure 4In corresponding part roughly the same, so repeating no more.
Figure 6Illustrate that the employing amplitude/phase according to the present invention one exemplary embodiment carries out the system frame processed as inputFigure.?Figure 6Exemplary embodiment in, the input/output of feedback controller 620 can be correspondingly amplitude and phase place.The input/output of digital predistorter 630 can also be correspondingly amplitude/phase.As the skilled person will be apparent, owing to can mutually change between I/Q and amplitude/phase, the input/output that therefore feedback controller is corresponding with digital predistorter and other involved assemblies can also be the combination of I/Q and amplitude/phase.Such as, the input of one assembly can be I/Q and export can be amplitude/phase, or input can be amplitude/phase and export can be I/Q, as long as it as input and/or provides output to mate as corresponding between another assembly of the input of this assembly to the output receiving this assembly.By as required and/or be designed with different input/output combination, the building form of this system is slightly different, but does not change the thought of whole design.
Figure 7Illustrate the predistorter processing i/q signal according to the present invention one exemplary embodiment realizes example.Figure 7Exemplary embodiment in digital predistorter 700 can such as correspond toFigure 4In digital predistorter 430, and such as can serve asFigure 5In digital predistorter 530.Figure 7The input of exemplary digital predistorter 700 can be intermediate frequency or baseband I/Q signal, it can be divided into two-way, and a road is through plural number modulo block 710, then to searchingTable (LUT)720.SearchTable (LUT) parameter relevant to radio-frequency power amplifier model can be placed in 720.Herein, searchTable (LUT) 720 can also be replaced by the calculating of radio-frequency power amplifier model formation.SearchTable (LUT) 720 output signal I1/Q1 with additionally lead up to time delay module 730 by input i/q signal time delay obtain carry out complex multiplication through time delayed signal I2/Q2, export predistorted Iout/Qout signal.One exemplary rather than in determinate embodiment, this complex multiplier 740 can be carried out according to (I1+jQ1) * (I2+jQ2), thus Iout=I1*I2-Q1*Q2, and Qout=I1*Q2+I2*Q1.Time delay in the present embodiment carries out plural number time of modulus and signal through searching equal to signal through plural number modulo block 710Table (LUT) the time sum of 720.
Figure 8Illustrate the predistorter that can process amplitude/phase according to another exemplary embodiment of the present invention realizes example.Figure 8Exemplary embodiment in digital predistorter 800 can such as correspond toFigure 4In digital predistorter 430, and such as can serve asFigure 6In digital predistorter 630.Figure 8The input of exemplary digital predistorter 800 can be amplitude and phase signal.WithFigure 7Digital predistorter 700 the most different,Figure 8In, the range signal Amp_in of input is divided into two-way, and a road directly arrives lookupTable (LUT) 820 and export Amp_Lut_out and Phase_Lut_out to vector multiplier 840.Another road Amp_in obtains through time delayed signal Amp_delay and Phase_delay through time delay module 830 together with the phase signal Phase_in of input and is input to vector multiplier 840.Vector multiplier 840 is to from lookupTable (LUT) 820 Amp_Lut_out and Phase_Lut_out and from time delay module 830 after time delayed signal Amp_delay and Phase_delay carries out vector multiplication export Amp_out and Phase_out.This time delay is that signal entered lookupTable (LUT) time of 820.As exemplary and indefiniteness example, this vector multiplication can include such as:
Amp_out=Amp_delay*Amp_Lut_out；
Phase_out=Phase_delay+Phase_Lut_out.
The one exemplary rather than determinate embodiment of the present invention relates to generating the lookup being available in predistorter usingTable (LUT).As previously described, because can change between I/Q and amplitude/phase, so the look-up table the most only used with the predistorter processing i/q signal explains orally.Those of ordinary skill in the art can be readily derived the generation method of the look-up table of predistorter being applicable to process amplitude/phase.
This sentence multinomial to radio-frequency power amplifier model as a example by, the generation process of look-up table is described.As skilled person will appreciate that, it is also possible to other modeling pattern are without departing from the scope of the present invention.This process can include following one or more steps.
(1) input radio frequency baseband signal, is designated as Y=Iy+jQy, produces the radiofrequency signal of amplitude scan, is input to power amplifier；
(2) gather the output signal of power amplifier, and be demodulated to base band, be designated as X=Ix+jQx；
(3) multinomial is usedThis power amplifier is modeled；
(4) by (1) and the data of (2), selected fitting criterion, such as but not limited to lowest mean square criterion, determine polynomial coefficient in (3)With exponent number N；
(5) by determining all coefficientsFormula with exponent number NGenerate look-up table.
In the exemplary of above step (1) in nonlimiting examples, the radiofrequency signal of amplitude scan refers to amplitude radiofrequency signal from small to large, it may include following at least one:
Qy=0, Iy start to be incremented to 32767 from 1；Or
Iy=0, Qy start to be incremented to 32767 from 1；Or
Qy=Iy starts to be incremented to 32767 from 1.
Those of ordinary skill in the art understand, and above scheme and numerical value are exemplary rather than determinate, according to design be actually needed, can use other scheme and numerical value, within they all fall within the scope of the present invention.
In another exemplary rather than in determinate embodiment, replace as it was previously stated, look-up table can also be calculated by radio-frequency power amplifier model formation.If realizing with formula, then (5) in this modeling process change into directly by formula to be calculated output data.The method that formula calculates is compared with loop up table, and when exponent number N is higher, amount of calculation is bigger.
Predistortion according to all exemplary embodiments of the present invention can realize in numeric field, such that it is able to realize in all kinds of digital devices, the most flexible.If radio-frequency power amplifier model changes, lookup the most only need to be changedIn tableContent.Another one benefit is, by using the modeling in complex field, can realize the adjustment to amplitude and phase place simultaneously.Further, by using jumbo look-up table, such as in FPGA, digital pre-distortion can possess preferable calibration result, can significantly improve the gain after correction and phase fluctuation.
The another exemplary of the present invention rather than determinate embodiment relate to the feedback controller such as used in radio-frequency power amplifier gamma correction system.What the feedback controller of the present invention may be used for causing the factors such as temperature non-linear is corrected.The feedback controller of the present invention can also realize in numeric field.In the exemplary embodiment, feedback controller can realize in intermediate frequency or base band, the control method such as proportional-integral-differential (PID) etc. of classics can be used to realize, it is possible to use the wave filter of other forms, such as multiphase filter.Those of ordinary skill in the art understand, and the feedback controller using various realization is without departing from the scope of the invention.
Figure 9Illustrate the feedback controller that can process amplitude/phase according to the present invention one exemplary embodiment realizes example.This exemplary example that realizes can use amplitude and phase place to carry out negative feedback as input.And according to an exemplary rather than determinate example, feedback control can be with adoption rate-derivative-integral controller (hereinafter referred to as PID controller).Such as,Figure 9Feedback controller 900 may correspond toFigure 4In feedback controller 420, and can serve as exampleSuch as figure 6In feedback controller 620.
According to exemplary realization,Figure 9In feedback controller 900 receive amplitude/phase feedback signal (Amp/Phase_feedback) and amplitude/phase reference signal (Amp/Phase_input), calculate the difference of amplitude feedback signal and the difference of amplitude reference signal and phase-feedback signal and phase reference signal, and be input in PID.In feedback controller 900, parameter logistic COEFFICIENT K p, the Ti time of integration, Td derivative time of PID are adjusted by the amplitude that exports with radio-frequency power amplifier of amplitude/phase reference signal, the relation of phase-feedback signal previously according to input, determine the value of Kp, Ti, Td, the above-mentioned parameter of PID can use gather examination method realize: first adjust Proportional coefficient K p, by proportionality coefficient by little increase, meet the waveform of demand to output, i.e. can determine that proportionality coefficient；The most again the Ti time of integration, Td derivative time are successively adjusted, until output meets the waveform of demand.After PID processes, i.e. complete the nonlinear problem caused due to heat effect or other factors, these feedback controller 900 output amplitudes/phase feedback output Amp/Phase_feedback_out.
Figure 10Illustrate the feedback controller that can process i/q signal according to another exemplary embodiment of the present invention realizes example.According to an exemplary embodiment, this exemplary example that realizes can use Low Medium Frequency multiphase filter to realize.As those of ordinary skill in the art understand, it can be contained base band and realize.For ease of describing, following exemplary embodiment describes as a example by Low Medium Frequency, skilled person will appreciate that use base band when realizing the most suitably modified.
Such as,Figure 10Feedback controller 1000 may correspond toFigure 4In feedback controller 420, and can serve as exampleSuch as figure 5In feedback controller 520.
According to exemplary realization,Figure 10The signal of middle input is radio frequency transmissions I/Q_input and Low Medium Frequency feedback signal I/Q_feedback of Low Medium Frequency, and both enter multiphase filter after subtracting each other.As those of ordinary skill in the art understand, it can be contained base band and realize.According to one is exemplary and nonlimiting examples, the transmission function of this multiphase filter can be by formulaBeing given, wherein K is peak gain, wcCentered by frequency, w0Half for baseband waveform bandwidth.Above-mentioned formula is a kind of transmission function of multiphase filter.After this multiphase filter, i.e. complete the nonlinear problem caused due to heat effect or other factors.
The mode using Low Medium Frequency multiphase filtering at numeric field can possess at least one in following advantage or many persons.
A () can reduce the impact of feedback network DC component.Feedback network such as uses mixing schemes, then local-oscillator leakage can cause the appearance of DC component.
B () can reduce the impact of feedback network image component, the frequency mixer in the middle of feedback network can cause the appearance of image component due to phase and amplitude imbalance.
(c) numeric field realize this wave filter compared to analog domain realize for, the impact of device parameters deviation is less.
According to the exemplary embodiment of the present invention, transmitting signal generator divides and feedback signal collecting part possesses multiple implementation.Such as, each of which can use frequency mixing method.
According to some exemplary embodiments, such as, during transmitting, Low Medium Frequency or the baseband digital signal of predistorter output can change into analogue signal through low speed digital-to-analogue conversion device, export to power amplifier with after local oscillator radio-frequency carrier signal analog frequency mixing afterwards.In this case, the feedback signal of corresponding radio-frequency power amplifier output mixes down to Low Medium Frequency or base band after being mixed in analog domain, then changes into digital signal through low speed modulus switching device.Such as, existFigure 4In the Exemplary System Embodiment of 6, Low Medium Frequency/baseband digital signal can be carried out by such as launching signal generation digital module 440,540,640 to the conversion of Low Medium Frequency/base-band analog signal, then can be carried out by launching signal generation analog module 450,550,650 with the analog frequency mixing of intrinsic radio-frequency carrier signal.Equally, feedback signal frequency reducing in analog domain can be gathered analog module 470,570,670 by feedback signal and carry out, and low speed analog digital conversion then can be gathered digital module 480,580,680 by feedback signal and carry out.Those of ordinary skill in the art understand, and above is only exemplary realization, other layout, arrange, deform and be also feasible and also fall within the scope of the present invention within.
According to other exemplary embodiments, it is possible to use transmitting to be directly synthesized the method directly sampled with feedback signal.Such as, during transmitting, in numeric field, complete the generation to radiofrequency signal of Low Medium Frequency or base band, then produce analogue signal through high-speed A/D converter part；During feedback, after analogue signal is filtered, directly by modulus switching device, radio frequency analog signal is changed into digital signal, in numeric field, then complete rf digital signal to Low Medium Frequency or the conversion of baseband signal.Such as, existFigure 4In the Exemplary System Embodiment of 6, can be carried out by such as launching signal generation digital module 440,540,640 from the raising frequency of Low Medium Frequency/base band to radio frequency in numeric field, high-speed digital-analog conversion the most then can be carried out by launching signal generation analog module 450,550,650.Equally, the analog digital conversion of feedback signal can be gathered analog module 470,570,670 by feedback signal and carry out, in numeric field from radio frequency to Low Medium Frequency/frequency reducing of base band then can gather digital module 480,580,680 by feedback signal and carry out.Those of ordinary skill in the art understand, and above is only exemplary realization, other layout, arrange, deform and be also feasible and also fall within the scope of the present invention within.
Later approach decreases analog frequency mixing link owing to carrying out raising frequency/frequency reducing in the digital domain, so launching and the noise level of feedback collection link being relatively low, and avoid the mirror image owing to using local oscillator to be caused and DC offset problem, additionally the time delay of feedback collection signal is the shortest, therefore, preferably, launch and feedback signal collection can use the method being directly synthesized and directly sampling.
The various embodiments of the method and system of the radio-frequency power amplifier of the present invention can have at least one in techniques below advantage or many persons.
I () radio frequency signal generating device, its input is modulated digital intermediate frequency or baseband signal, and thus produces analog radio-frequency signal.Compared with being carrier wave and envelope signal with input, the carrier signal change generation module relevant to magnetic resonance applications is simplified, decreases design difficulty.
(ii) in numeric field, the method using predistortion, relevant to input power non-linear to radio-frequency power amplifier is corrected；It can correct amplitude and phase nonlinear simultaneously.Which calibration result is good, and little to the dependency of device, and when radio-frequency power amplifier characteristic changes, amendment is convenient.
(iii) using feedback method, be corrected predistorted system, it is for by thermally-induced non-linear.Due to after predistortion, the relevant to input power non-linear of radio-frequency power amplifier has been corrected, and thermally-induced nonlinear time constant is bigger, therefore compared with directly using degenerative method, decrease the design complexities of degeneration factor, and improve the stability of degeneration factor.
It will be recognized by one of ordinary skill in the art that beneficial effects of the present invention is not all realized by any single embodiment.Various combinations, revise and replacement is those of ordinary skill in the art and is understood on the basis of the present invention.
Additionally, term "or" is intended to indicate that inclusive "or" and nonexcludability "or".Can be clear that i.e., except as otherwise noted or from context, otherwise phrase " X uses A or B " is intended to indicate that any arrangement of naturally can holding concurrently.That is, phrase " X uses A or B " is met by example any in following instance: X uses A；X uses B；Or X uses A and B.It addition, article " " used in the application and appended claims and " certain " are typically to be understood as expression " one or more ", unless stated otherwise or can be apparent from from the context referring to singulative.
Various aspects or feature by with can include several equipment, assembly, module, and the like the form of system present.It should be understood that and understand, various systems can include optional equipment, assembly, module etc., and/or can not include combiningAccompanying drawing instituteThe armamentarium of discussion, assembly, module etc..The combination of these ways can also be used.
The various illustrative logical, logical block, module and the circuit that describe in conjunction with presently disclosed embodiment can realize with general processor, digital signal processor (DSP), special IC (ASIC), field programmable gate array (FPGA) or other PLD, discrete door or transistor logic, discrete nextport hardware component NextPort or its any combination being designed to carry out function described herein or perform.General processor can be microprocessor, but in alternative, processor can be the processor of any routine, controller, microcontroller or state machine.Processor is also implemented as the collaborative one or more microprocessors of the combination of calculating equipment, such as DSP and the combination of microprocessor, multi-microprocessor and DSP core or any other this type of configuration.Additionally, at least one processor can include may act on execution one or more steps described above and/or one or more modules of action.
Additionally, combine method or the step of algorithm that aspect disclosed herein describes and/or action can be embodied directly in hardware, in the software module performed by processor or implements in combination of the two.
The key element of the various aspects described in the whole text in the present invention is that equivalents in all structures that those of ordinary skill in the art are currently or hereafter known and functionally is clearly included in this by citation, and is intended to be intended to be encompassed by the claims.The most explicitly described additionally, any content disclosed herein is all not intended to contribute to the most such disclosure of the public.
Claims (10)
1. the method for radio-frequency power amplifier gamma correction, it is characterised in that including:
S1: according to feedback signal, input signal is carried out negative feedback correction, export negative-feedback signal；
S2: described negative-feedback signal is carried out predistortion correction, exports predistorted signal to described radio frequency
Power amplifier；
S3: gather the signal amplified through described radio-frequency power amplifier, and generate described feedback signal, so
Rear return step S1.
2. the method for claim 1, it is characterised in that described input signal includes digital medium-frequency signal
Or digital baseband signal.
3. the method for claim 1, it is characterised in that described step S1 farther includes: ask for
Input signal and the difference of feedback signal, and by PID control realization, the negative feedback of input signal is corrected.
4. method as claimed in claim 3, it is characterised in that previously according to described input signal and described instead
Parameter Kp, Ti, Td of PID are adjusted by feedback signal.
5. the method for claim 1, it is characterised in that described step S1 farther includes, and asks for
Input signal and the difference of feedback signal, and realize the correction of the negative feedback to input signal by multiphase filter.
6. the method for claim 1, it is characterised in that described negative-feedback signal is carried out predistortion school
Just including the look-up table that power based on radio-frequency power amplifier and/or phase place generate with the change curve of input power
Described negative-feedback signal is compensated.
7. the method for claim 1, it is characterised in that the described feedback signal of described generation, including:
The signal amplified through described radio-frequency power amplifier collected is coupled as radiofrequency signal by a small margin.
8. the method for claim 1, it is characterised in that described negative feedback correction and/or predistortion correction
Realize in numeric field.
9. radio-frequency power amplifier gamma correction system, it is characterised in that including:
Feedback controller, carries out negative feedback correction according to feedback signal to the signal being input to feedback controller；
Predistorter, carries out predistortion correction to the signal being input to described predistorter；
Radio-frequency power amplifier, for carrying out power amplification to the signal through negative feedback correction and predistortion correction；
And
Signal acquisition module, gathers the signal through power amplification, and generates feedback signal output to described feedback
Controller.
10. system as claimed in claim 9, it is characterised in that described feedback controller farther includes PID
Controller or multiphase filter, according to described feedback signal and the difference of the described signal being input to feedback controller,
The described signal being input to feedback controller is corrected.
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