CN1516493A - Power amplifier linearization method and linear power amplifier device - Google Patents
Power amplifier linearization method and linear power amplifier device Download PDFInfo
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- CN1516493A CN1516493A CNA031148751A CN03114875A CN1516493A CN 1516493 A CN1516493 A CN 1516493A CN A031148751 A CNA031148751 A CN A031148751A CN 03114875 A CN03114875 A CN 03114875A CN 1516493 A CN1516493 A CN 1516493A
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Abstract
The invention relates to a kind of linearization method of power amplifier in signal process field, the invention acquires the enveloped spectrum information of nonlinear distorted signal of power amplifier from front feedback signal counteraction loop, and feedbacks then to the input channel of power amplifier through degenerative feedback loop, and superimposes and modulates the enveloped spectrum, with the input signal, and forms the input signal pre-skewness, realizes the linear amplification of power amplifier. The device includes front feedback signal counteraction model, nonlinear skewness enveloped spectrum degenerative feedback model which is the enveloped spectrum information acquired from the front feedback signal counteraction model, and feedbacks it to the input channel of the power amplifier to be modulated into the enveloped spectrum.
Description
Technical field
The invention belongs to the signal processing field, particularly a kind of linearization technique of amplifier and device.
Background technology
Because Modern Mobile Communications Systems is to the rapid expansion of linear power amplifier demand, various linearization techniques and power amplifier linearization method are able to fast development.Main linearization technique and method comprises three types at present: feedforward (Feed-Forward), predistortion (Predistortion) and envelope feedback (Envelop-Feedback).They improve the linear index of power amplifier respectively from three angles.
Desirable amplifier is to provide a complete transparent transmission channel for radio-frequency carrier signal: to the input signal of any frequency in the working band, realize in full dynamic range that fixed ratio ground amplitude is amplified, phase deviation stably and time delay unchangeably, do not produce simultaneously the signal component of any other component, promptly input signal is carried out linear power amplification.But, because all there is nonlinear component in the transfer function of any amplifier in the reality, promptly in the amplification output of input radio frequency carrier signal, not only have the carrier wave composition that is exaggerated, but also exist harmonic wave, spuious, intermodulation (if incoming carrier is multitone (Muti-tone) modulation signal) distortion component, simultaneously indexs such as Amplifier Gain, phase shift and group delay also can be along with factors such as the frequency of signal, amplitude, ambient temperature, device aging change.So need to adopt the linear index of the linearisation means raising power amplifier that adds, to satisfy the basic demand of Modern Mobile Communications Systems.
Feedforward linearized method is to utilize feed-forward signal to offset loop to extract nonlinear distortion information in the main power amplifier output signal, and utilize another feed-forward signal to offset loop and offset the nonlinear distortion composition of eliminating in the main power amplifier output signal at system's output, realize the linearisation target of power amplifier.A kind of typical feedforward linearized method is provided in U.S. Pat 4389618.This method has very high linearisation and improves index (theoretical capability for correcting can reach 30dB, handle bandwidth can reach 25MHz), but complex structure, cost height.Such as U.S. US4389618, except two basic signal cancellation loop and adaptive tracing mechanism, for improving the adaptive ability of error loop (nonlinear distortion is offset ring), increased a signal cancellation loop in addition, to detect the gain and the phase-shift characterisitc of the neutralization effect departure amplification link of following the tracks of nonlinear properties, the complete dynamic linearity of assurance system is improved performance.Therefore, structure is very complicated.Simultaneously,, be difficult to reach ideal effect, so the system linearity improvement is difficult to the target of realizing ideal because the error loop realization is the neutralisation process of a weak signal (with respect to main signal).In addition, because the insertion power loss of main power amplifier output channel and the power consumption of other (except that main power amplifier) active circuit are used very difficult the acquisition than higher direct current-radio frequency conversion efficiency of linear power amplifier device that feedforward linearized method realizes.
As shown in Figure 1, input signal is through output such as power splitter 1 branch such as grade, and one road signal is sent into main power amplifier 2 and carried out power amplification, and back input and road device 9 are regulated through delay line 6, electrically controlled attenuator 7, voltage controlled phase shifter 8 in another road; After the output signal of main power amplifier 2 is taken a sample through sampling coupler 3, enter and road device 9 another inputs, carry out signal cancellation with the input signal of time-delay branch road, eliminate the input signal spectrum component in the main power amplifier output sampled signal, obtain representation signal---the error signal of the nonlinear distortion of power amplification introducing, and send into error amplifier 12 through electrically controlled attenuator 10, voltage controlled phase shifter 11; Error signal after the amplification enters the power amplifier output channel by directional coupler 5, carry out signal cancellation with the main power amplifier output signal of delaying time through delay line 4, eliminate non-linear distortion products wherein, obtain the very high high-power signal output of the linearity at the power amplifier output.
As seen from Figure 1, feed forward type linear power amplifier comprises two basic signal cancellation loop---main ring and error loop.
What main ring carried out is the neutralisation process of two main signals: through main power amplifier 2 amplify and by after 3 samplings of sampling coupler be exaggerated main signal with through the incoming host signal of time-delay with road device 9 in anti-phase addition.When two-way main signal amplitude equates, offset during 180 ° of phase phasic differences and reach ideal effect (eliminating the main signal composition in the main power amplifier 2 output sampled signals fully), but the gain of main power amplifier 2 and phase-shift characterisitc can be along with input powers, operating frequency, factor such as ambient temperature and device aging and changing, for dynamically guaranteeing the good counteracting of main signal, in the time-delay branch road, amplitude and phase adjusted parts one electrically controlled attenuator 7 and voltage controlled phase shifter 8 have been inserted, and in conjunction with the self-adapting detecting controlling unit that adds, the gain of dynamic tracking master's power amplifier 2 and phase shift variations.Because participating in the two paths of signals of counteracting all is the suitable large-signals of amplitude, can by directly detect offset result or indirectly relatively the amplitude of two paths of signals and phase error realize that the adaptive tracing of offsetting loop controls, and then guarantee good neutralization effect.
Error loop is to be coupled into main channel and the anti-phase addition of main power amplifier 2 output signals of delaying time through delay line 4 by directional coupler 5 through the error signal that error amplifier 12 amplifies, offset the nonlinear distortion signal of eliminating wherein, realize the target that system linear improves.Be gain and the phase shift unsteadiness that overcomes error amplifier 12, amplitude and phase place adjustment component-electrically controlled attenuator 11 and voltage controlled phase shifter 12 in its input channel, have been added, and in conjunction with the self-adapting detecting controlling mechanism that adds, dynamically revise the gain and the phase-shift phase of steady state error amplification channel, guarantee the good counteracting of nonlinear distortion signal.Because this loop is realized is to offset the process of eliminating small-signal in the composite signal that a large-signal (main signal after being exaggerated) adds small-signal (nonlinear distortion signal) formation with a small-signal (error signal), the two paths of signals amplitude differs bigger on the one hand, large-signal in the composite signal is that small-signal is offset the unavoidable strong interference of detection link on the other hand, therefore error loop can't realize actual offseting signal self-adapting detecting and the control mode and the corresponding mechanism of similar main ring, so signal cancellation always is difficult to reach ideal effect, that is to say that feedforward linearized means can't reach Molded Line property improvement target.
Predistortion is to utilize at the amplifier front end to insert non-linear (non-linear behaviour is opposite with amplifier nonlinearity characteristic quadrature) parts (predistorter), suppress to revise nonlinear component in its transfer function by in amplifier input signal, directly introducing distorted signal, reach the target of power amplifier linearization.This method owing to need not add in the power amplifier output channel does not have the parts that insert loss, does not need the active power consumption circuit of error amplifier and so on simultaneously yet, and not only simple in structure but also direct current-radio frequency conversion efficiency is than higher.But, owing to the predistorter that can not realize mating fully with the nonlinear characteristic of power amplifier, and the nonlinear characteristic of power amplifier can change along with factors such as operating frequency, input power, ambient temperature and device agings, so this linearization technique improve index lower (Molded Line property improvement index can reach 3 ~ 7dB (add adaptation mechanism then can reach 20dB), handles bandwidth and can reach 25MHz).In addition, because the insertion loss that predistorter brings need compensate by increasing the Amplifier Gain index, improved the Design of Amplifier difficulty.This method can retrieve in U.S. Pat 4992754.
As shown in Figure 2, by in amplifier 22 input channels, inserting the rugged change of envelope in advance that predistorter 21 causes input signal 20, because the rugged change characteristic of predistorter 21 is opposite with the nonlinear distortion characteristics quadrature of amplifier 22, signal 23 through amplifier 22 back outputs will recover the original envelope characteristic of input signal 20, thereby reach amplifier 22 linearizing targets.Because can not directly find the predistorter 21 that mates fully with amplifier 22 distorted characteristics, and the distorted characteristic of amplifier 22 can change with factors such as operating frequency, input power, ambient temperature and device agings, and this linearization technique can't reach good effect.
Summary of the invention
The invention provides a kind of power amplifier linearization method and linear power amplifier device,, complex structure accurately not high in the prior art and insecure problem of working to solve.
The method applied in the present invention is: this power amplifier linearization method, in the amplification system that comprises feed-forward signal counteracting loop, offset the nonlinear distortion signal envelope spectrum information that loop obtains power amplifier from feed-forward signal, and utilize negative feedback loop that it is presented input channel to power amplifier in real time, with its envelope frequency spectrum of input signal superposition modulated, cause the input signal predistortion, realize that power amplifier linearization amplifies;
Described feed-forward signal is offset amplitude difference and the phase difference of loop by the input and output signal of detection power amplifier, generate the gain of feedforward cancellation loop gain and phase control, through dynamic tuning, make main signal obtain good the counteracting, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier;
Described nonlinear distortion envelope frequency spectrum is followed gain and the phase-shift phase of adjusting negative feedback loop through power detection, makes nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum;
This linearization technique adopts following controlled step:
Step 1: detect feedforward cancellation loop two-way and participate in offseting signal amplitude difference Δ G and phase difference P;
Step 2: utilize Δ G and Δ P to generate the gain-controlled voltage V of feedforward cancellation loop gain and phase controller
GWith phase control voltage V
P
Step 3: negative feedback nonlinear distortion envelope frequency spectrum sampled signal ingoing power amplifier input channel;
Step 4: detect and control the negative feedback parameter and make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
Comprise following control procedure in the described step 1:
At first, make up feed-forward signal and offset loop, the input and output signal of sample-power amplifier respectively, and they are sent into the signal cancellation device simultaneously, form feed-forward signal and offset loop;
Secondly, the two-way input signal of sampled signal Canceller;
Then, detect the amplitude difference Δ G of two-way sampled signal: the two-way sampled signal is carried out magnitude demodulator respectively, and obtain to participate in the amplitude difference Δ G of offseting signal through subtracter;
At last, detect the phase difference P of two-way sampled signal: utilize phase discriminator to detect the phase difference P that obtains to participate in offseting signal.
Comprise following control procedure in the described step 2:
At first, set up feedforward cancellation loop gain control voltage V
G: adopt V
G=-K
GThe control structure of Δ G+G1 obtains gain-controlled voltage V
G, and control in real time is arranged in the gain controller of power amplifier input channel;
Secondly, set up feedforward cancellation loop phase control voltage V
P: adopt V
P=-K
PThe control structure of Δ P+P1 obtains phase control voltage V
P, and control in real time is arranged in the phase controller of power amplifier input channel;
Then, tuning K
G, G1, K
P, P1: dynamic tuning K
G, G1, K
P, P1, make Δ G and Δ P minimum, and then guarantee the good counteracting of main signal, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier.
Comprise following control procedure in the described step 3:
At first, nonlinear distortion envelope frequency spectrum sampled signal is introduced the power amplifier input channel: with the nonlinear distortion envelope frequency spectrum sampled signal that obtains, after controlled gain amplification and adjustable phase shift, the input channel of power amplifier is sent in coupling;
Then, pre-distorting power amplifier input signal: power amplifier is given in nonlinear distortion envelope frequency spectrum signal that coupling is introduced and input signal stack, carries out power amplification.
Comprise following control procedure in the described step 4:
At first, detect nonlinear distortion envelope frequency spectrum power: utilize power-sensing circuit, monitoring feedforward cancellation loop is offset the nonlinear distortion envelope frequency spectrum sampled signal amplitude of output;
Then, closed-loop control predistortion effect: follow gain and the phase-shift phase of adjusting negative feedback loop, make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
The linear power amplifier device of this realization said method, comprise feed-forward signal cancellation module 81, also comprise nonlinear distortion envelope frequency spectrum negative feedback module 84, this nonlinear distortion envelope frequency spectrum negative feedback module 84 is obtained the nonlinear distortion signal envelope spectrum information of power amplifier by feed-forward signal cancellation module 81, and with input channel and the input signal superposition modulated envelope frequency spectrum of its negative feedback to power amplifier;
Described feed-forward signal cancellation module 81 comprises coupler 8101, coupler 8102, gain controller 8103, phase controller 8104, power amplifier 8105 and coupler 8106, and the formation main channel that links to each other successively; Also comprise delay line 8110 and coupler 8111, and the input and output signal of coupler 8107 difference received power amplifiers; Described two paths of signals is transported to amplitude-phase detector 8109 by coupler 8107 and coupler 8111 respectively, again by adaptive cancellation controller 8108, be connected to gain controller 8103 and phase controller 8104, and described two paths of signals outputs signal to signal cancellation device 8112;
Described amplitude-phase detector 8109 comprises amplitude-phase detection module 91 and computing module 92; Wave detector 911,912 detecting signal amplitudes in the amplitude-phase detection module 91, and by the computing circuit 921 of subtracter 913 output amplitude difference Δ G to the computing module 92; The computing circuit 922 of phase discriminator 914 phase difference output Δ P in the amplitude-phase detection module 91 to the computing module 92;
Described nonlinear distortion envelope frequency spectrum negative feedback module 84 comprises coupler 8401, controlled amplifier 8403 and phase shifter 8404, and link to each other successively, nonlinear distortion signal envelope spectrum information is fed back to the input channel of power amplifier;
Described nonlinear distortion envelope frequency spectrum negative feedback module 84 also comprises power detector 8402 and adaptive line controller 8405, power detector 8402 monitoring nonlinear distortion envelope frequency spectrum sampled signal amplitudes are followed adjustment by 8405 pairs of phase shifters 8404 of adaptive line controller and controlled amplifier 8403.
Principle of the present invention and beneficial effect are: the envelope feedback is a kind of special case of self-adapted pre-distortion linearization technique, also is a special case of amplifier negative-feedback technology.It is by the sampling amplifier output signal, and utilizes the envelope of its envelope trait modulation modification amplifier input signal, and then utilizes the correction of amplifier nonlinearity envelope modulation transmission characteristic to recover the original envelope trait of input signal.This mode is very useful for the linearisation of CDMA (code division multiple access) and so on broadband envelope modulated signal amplifier, because the CDMA signal is exactly the rugged change of envelope of frequency spectrum diffusion through the non-linear amplification most typical distortion in back, so with this rugged change characteristic input channel that transmission enters amplifier through negative feedback loop, modulation changes the spectrum envelope of input CDMA signal, because this modulated process is to carry out according to amplifier nonlinearity distorted characteristic quadrature feedback fully, so import the original envelope characteristic of CDMA by revising recovery behind the amplifier in real time, thereby reach effect to the linear power amplification of CDMA signal.
The detection controlling unit that the present invention adopts variable predistorter of performance and combination to add realizes the adaptation function of distortion linearizing method, fully improves its linearity and improves ability.From the another one angle, the distortion result that has only amplifier to cause is only with the distorted characteristic of himself mates fully, that is to say, by corresponding processing links the distortion component in the amplifier output signal is fed back to its input, and then the predistortion of introducing is the most rational, it also is near ideal value that linearity is improved effect, therefore, the present invention provides this power amplifier linearization method with mechanism and the perfect adaptation of envelope feedback theory by good main signal counteracting (in main ring) extraction amplifier nonlinearity distorted signal in the feed-forward technique, this power amplifier linearization method has not only been inherited pre-distortion technology and has been constituted simple, the advantage that direct current-the radio frequency conversion efficiency is high, and because need not cause the amplitude loss of input signal at amplifier input channel insertion predistorter, so do not increase Amplifier Gain design burden, simultaneously owing to increased the negative feedback loop of output to input, thereby Amplifier Gain stability and phase shift linear index are fully improved, thus, the present invention is accurately high, simple in structure and reliable operation is applicable to mobile communication system.
Specifically, the present invention has following excellent results:
The first, self-adaptive controlled making mechanism is more complete.The present invention adopts the adaptive control function of the system of actual signal reference pattern realization completely, the detection sensitivity height, control accurately, therefore the sampling of nonlinear distortion envelope frequency spectrum is extracted accurately accurate, the envelope feedback element linearity is fine simultaneously, the second-order distortion of introducing is lower, and predistortion performance and non-linearity of power amplifier matching ratio are better, so linear improvement degree is more near desired result;
The second, system realizes that difficulty is smaller.Linear power amplifier device provided by the invention all adopts general circuit and design, does not need special-purpose device or realization technology, so system design realization difficulty is smaller, and development and production risk are lower;
The 3rd, realize that product is reliable, stable.On the one hand, in linear power amplifier device embodiment provided by the invention, there is not power loss (the straight-through loss of coupler 8106 can be ignored) in power amplifier 8105 output channels, simultaneously, other peripheral components does not have the too device of power consumption, therefore the product that adopts this embodiment to realize can reach than higher direct current one radio frequency conversion efficiency, and system power dissipation is lower, and reliability is corresponding to be improved; On the other hand, the envelope feedback path among the present invention has degenerative effect to power amplifier 8105, and its working stability degree and noise, spuious rejection are fully improved.
Description of drawings
Fig. 1 is for adopting the linear power amplifier principle of device frame diagram of feedforward linearized method;
Fig. 2 is for adopting the linear power amplifier principle of device frame diagram of distortion linearizing method;
Fig. 3 is a method overview flow chart of the present invention;
Fig. 4 is the concrete control procedure schematic diagram of step 1 of the present invention;
Fig. 5 is the concrete control procedure schematic diagram of step 2 of the present invention;
Fig. 6 is the concrete control procedure schematic diagram of step 3 of the present invention;
Fig. 7 is the concrete control procedure schematic diagram of step 4 of the present invention;
Fig. 8 is a linear power amplifier device embodiment frame diagram of the present invention;
Fig. 9 is the embodiment frame diagram of amplitude-phase detector and adaptive cancellation controller in the linear power amplifier device of the present invention;
Figure 10 handles the gain of front and back power amplifier with input power change curve comparison diagram for adopting linearization technique of the present invention;
Figure 11 handles the phase shift of front and back power amplifier with input power change curve comparison diagram for adopting linearization technique of the present invention.
Embodiment
With embodiment the present invention is described in further detail with reference to the accompanying drawings below:
According to Fig. 8 and Fig. 9, the present invention includes feed-forward signal cancellation module 81 and nonlinear distortion envelope frequency spectrum negative feedback module 84, this nonlinear distortion envelope frequency spectrum negative feedback module 84 is obtained the nonlinear distortion signal envelope spectrum information of power amplifier by feed-forward signal cancellation module 81, and with input channel and the input signal superposition modulated envelope frequency spectrum of its negative feedback to power amplifier.
Linearization technique of the present invention is: offset in the amplification system of loop at this feed-forward signal that comprises, offset the nonlinear distortion signal envelope spectrum information that loop obtains power amplifier from feed-forward signal, and utilize negative feedback loop that it is presented input channel to power amplifier in real time, with its envelope frequency spectrum of input signal superposition modulated, cause the input signal predistortion, realize that power amplifier linearization amplifies; Wherein, feed-forward signal is offset amplitude difference and the phase difference of loop by the input and output signal of detection power amplifier, generate the gain of feedforward cancellation loop gain and phase control, through dynamic tuning, make main signal obtain good the counteracting, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier; The nonlinear distortion envelope frequency spectrum is followed gain and the phase-shift phase of adjusting negative feedback loop through power detection, makes nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
As shown in Figure 3, the linearization technique among the present invention need carry out according to four basic steps:
As shown in Figure 4, comprise following concrete control procedure in the step 1:
The first step makes up feed-forward signal and offsets loop.Basic main ring principle according to feedforward linearized scheme constitutes framework and builds a signal cancellation loop, utilizes the carrier frequency composition in the input signal counteracting elimination power amplifier output sampled signal of taking a sample;
Second step, the two-way input signal of sampled signal Canceller.Utilize two directional couplers to take a sample respectively and participate in the two-way input signal of counteracting.
The 3rd step, the amplitude difference Δ G of detection two-way sampled signal.Obtain the amplitude difference that two-way is participated in offseting signal in conjunction with magnitude demodulator and subtraction.
The 4th step, the phase difference P of detection two-way sampled signal.Utilize phase discriminator to detect the phase difference that two-way is participated in offseting signal.
Step 2 utilizes Δ G and Δ P to generate the gain-controlled voltage V of feedforward cancellation loop gain and phase controller
GWith phase control voltage V
PThe peripheral controlling unit that detects is on the basis of amplitude difference Δ G that previous step obtains and phase difference P, by two formula algorithm V
G=-K
GΔ G+G1 and V
P=-K
PΔ P+P1 obtains gain and phase control voltage V
GAnd V
P, closed-loop control feedforward main signal neutralisation process, and at suitable manual tuning algorithm parameter K
G, G1, K
P, P1 the basis on, the amplitude and the phase place that make signal cancellation point participate in offseting signal remain matched well, reach dynamic best the counteracting;
As shown in Figure 5, comprise following concrete control procedure in the step 2:
The first step is set up feedforward cancellation loop gain control voltage V
GThe amplitude difference Δ G that obtains with step 2 is an input variable, by algorithm V
G=-K
GΔ G+G1 obtains the gain-controlled voltage V of feedforward cancellation loop
G
In second step, set up feedforward cancellation loop phase control voltage V
PThe phase difference P that obtains with step 2 is an input variable, by algorithm V
P=-K
P+ P1 obtains the phase control voltage V of feedforward cancellation loop
P
The 3rd step, tuning K
G, G1, K
P, P1.Real-time regulated gain feedback oscillator K
G, gain biasing G1 and phase feedback gain K
P, phase bias P1, make the gain inequality Δ G and the phase difference P minimum of the two paths of signals of participating in counteracting, and then well balance out carrier frequency composition in the power amplifier output sampled signal signal, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier.
Step 3, negative feedback nonlinear distortion envelope frequency spectrum sampled signal signal ingoing power amplifier input channel.After the nonlinear distortion envelope frequency spectrum sampled signal that the power amplifier that last two steps operation is obtained is introduced amplifies by certain adjustable gain and variable phase moves, the input channel of power amplifier is introduced in coupling, with the system input signal superposition modulated, the input signal that obtains predistortion is given power amplifier;
As shown in Figure 6, comprise following concrete control procedure in the step 3:
The first step is introduced the power amplifier input channel with nonlinear distortion envelope frequency spectrum sampled signal.After handling by controlled gain amplification, adjustable phase shift etc., the nonlinear distortion envelope frequency spectrum sampled signal that step 2 is obtained by a directional coupler is introduced the input channel of power amplifier;
Second step, the pre-distorting power amplifier input signal.After the nonlinear distortion envelope frequency spectrum signal that coupling is introduced superposes with input signal, ingoing power amplifier together, thus cause the predistortion effect of power amplifier input signal.
Step 4 detects and control negative feedback parameter makes nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.Pre-distorted signals is through the linear amplification and the nonlinear transport of power amplifier, obtain the system input signal and the nonlinearity product that are exaggerated at its output, the nonlinear distortion envelope frequency spectrum sampled signal power that monitoring was obtained by the first step and second step, and the gain of dynamic tuning negative feedback channel and phase-shift phase, make it to minimize, the nonlinearity product that is power amplifier keeps the minimum radius power spectrum, and then realizes the linearisation target of power amplifier.
As shown in Figure 7, comprise following concrete control procedure in the step 4:
The first step detects nonlinear distortion envelope frequency spectrum power.The spectrum power value that is coupled and takes a sample and obtain the nonlinear distortion envelope frequency spectrum signal of step 2 acquisition by magnitude demodulator;
Second step, closed-loop control predistortion effect.Continuous monitoring nonlinear distortion envelope frequency spectrum performance number, and adjust the gain and the phase-shift phase of nonlinear distortion envelope negative feedback loop in real time, make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum, realize best predistortion linear effect.
As shown in Figure 8, feed-forward signal cancellation module 81 comprises coupler 8101, coupler 8102, gain controller 8103, phase controller 8104, power amplifier 8105 and coupler 8106, and the formation main channel that links to each other successively; Also comprise delay line 8110 and coupler 8111, and the input and output signal of coupler 8107 difference received power amplifiers; Described two paths of signals is transported to amplitude-phase detector 8109 by coupler 8107 and coupler 8111 respectively, again by adaptive cancellation controller 8108, be connected to gain controller 8103 and phase controller 8104, and described two paths of signals outputs signal to signal cancellation device 8112; As shown in Figure 9, amplitude-phase detector 8109 comprises amplitude-phase detection module 91 and computing module 92; Wave detector 911,912 detecting signal amplitudes in the amplitude-phase detection module 91, and by the computing circuit 921 of subtracter 913 output amplitude difference Δ G to the computing module 92; The computing circuit 922 of phase discriminator 914 phase difference output Δ P in the amplitude-phase detection module 91 to the computing module 92.
As shown in Figure 8, nonlinear distortion envelope frequency spectrum negative feedback module 84 comprises coupler 8401, controlled amplifier 8403 and phase shifter 8404, and link to each other successively, nonlinear distortion signal envelope spectrum information is fed back to the input channel of power amplifier; This nonlinear distortion envelope frequency spectrum negative feedback module 84 also comprises power detector 8402 and adaptive line controller 8405, power detector 8402 monitoring nonlinear distortion envelope frequency spectrum sampled signal amplitudes are followed adjustment by 8405 pairs of phase shifters 8404 of adaptive line controller and controlled amplifier 8403.
As shown in Figure 8, input signal 80 enters feed-forward signal cancellation module 81 by coupler 8101, the coupling sampled signal is sent to delay line 8110, through connect signal carries out power amplification through coupler 8102 amplitude, phase adjusted ingoing power amplifiers 8105 straight-through and gain controller 8103 and phase controller 8104, its output signal through coupler 8106 straight-through output system output signals 82, is then given coupler 8107 by its coupling sampling on the one hand on the other hand; The processing of leading directly to and take a sample of 8107 output sampled signals of coupler with power amplifier 8105, sampled signal Sm sends into amplitude-phase detector 8109, and through connect signal entering signal Canceller 8112 is participated in main signals and is offset; Input sampled signal by delay line 8110 time-delays passes through coupler 8111 samplings and straight-through, sampled signal Ss enters amplitude-phase detector 8109, through connect signal is sent into signal cancellation device 8112, offset the main signal composition of eliminating wherein with power amplifier 8105 output sampled signals, obtain nonlinear distortion envelope frequency spectrum sampled signal 83 and send into nonlinear distortion envelope frequency spectrum negative feedback module 84; Signal Sm and Ss relatively detect their amplitude difference Δ G and phase difference P by the amplitude-phase detector, and present to adaptive cancellation controller 8108, generate the closed-loop control voltage V of gain controller 8103 and phase controller 8104
GAnd V
P, the self-adapting detecting controlled function of realization main signal neutralisation process; Nonlinear distortion envelope frequency spectrum sampled signal 83 is through coupler 8401 straight-through, samplings, through connect signal is through the linear amplification of controlled amplifier 8403 and the phase adjusted of phase shifter 8404, output nonlinear distortion envelope frequency spectrum feedback signal 85 is given feed-forward signal cancellation module 81, and pass through the input channel that coupler 8102 is introduced power amplifiers 8105, realize predistortion with input signal 80 superposition modulated; The coupling output signal ingoing power detector 8402 of coupler 8401 is measured the nonlinear distortion sample of signal envelope frequency spectrum energy P that power amplifier 8105 produces, then by the control voltage V of adaptive line controller 8405 according to controlled amplifier 8403 and phase shifter 8404 in the tuning negative feedback channel of P value
G1And V
P1, tuning target is that the P value is lower than threshold value, and then guarantees the nonlinear distortion signal envelope spectrum power minimum in the system output signal 82.
As Fig. 8 and shown in Figure 9, amplitude-phase detector 8109 is responsible for detecting two-way is participated in offseting signal in signal cancellation device 8112 amplitude difference Δ G and phase difference P, its relies on the amplitude of wave detector 911 in amplitude-phase detection module 91 and 912 detecting signal Sm and Ss and detects the amplitude difference Δ G of Sm and Ss by the subtraction that subtracter 913 is realized, relies on the phase difference P of phase discriminator 914 acquisition Sm and Ss simultaneously; Adaptive cancellation controller 8108 among Fig. 8 is realized V by the computing circuit 921 in the computing module 92 and 922
G=-K
GΔ G+G1 and V
P=-K
PΔ P+P1 algorithm obtains the control voltage V of gain controller 8103
GControl voltage V with phase controller 8104
P
As shown in Figure 10 and Figure 11, shown adopt linearization technique of the present invention handle before and after the gain of power amplifier and phase-shift phase with input power change curve comparison diagram.At present widely used category-A or AB power-like amplifier all have the characteristic that the gain shown in the solid line and phase shift change with input power among Figure 10 and Figure 11 in the communication system, promptly there are linear zone, expansion regions and compressional zone, in expansion regions and compressional zone, compressional zone particularly, power amplifier exists very strong AM-AM (amplitude modulation-amplitude modulation) and AM-PM (amplitude modulation-phase modulation) nonlinear distortion.Shown in Figure 8 the invention provides among the linear power amplifier device embodiment, one side is well offset in order to guarantee main signal, adaptive cancellation detection and controlling mechanism by loop cooperate gain controller 8103 and the phase controller 8104 that is serially connected with in the system signal transmission main channel, closed-loop adjustment control makes the gain of main channel and phase-shift characterisitc and time-delay passage, and (input signal is through coupler 8101, delay line 8110 and coupler 8111 are to signal cancellation device 8112) gain consistent with the phase-shift characterisitc coupling, and the time-delay passage is formed by passive device, have the good gain and the phase shift linearity, so the control result will make the gain and the phase shift linearisation of main channel, that is to say to make power amplification circuit have AGC (automatic gain control) and APC (automatic phase control) function that its gain and phase-shift phase will be corrected for Figure 10 and curve shown in dotted lines in Figure 11 with the variation characteristic of input power; On the other hand, because the predistortion linear of system improves ability, AM-AM and the AM-PM distortion that makes power amplifier in expansion regions and compressional zone obtained thoroughly or partly revising.Therefore, to improve effect be many-sided to the linearity of power amplifier linearization method provided by the invention and linear power amplifier device embodiment.
Claims (13)
1. power amplifier linearization method, it is characterized in that: in the amplification system that comprises feed-forward signal counteracting loop, offset the nonlinear distortion signal envelope spectrum information that loop obtains power amplifier from feed-forward signal, and utilize negative feedback loop that it is presented input channel to power amplifier in real time, with its envelope frequency spectrum of input signal superposition modulated, cause the input signal predistortion, realize that power amplifier linearization amplifies.
2. power amplifier linearization method according to claim 1, it is characterized in that: described feed-forward signal is offset amplitude difference and the phase difference of loop by the input and output signal of detection power amplifier, generate the gain of feedforward cancellation loop gain and phase control, through dynamic tuning, make main signal obtain good the counteracting, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier.
3. power amplifier linearization method according to claim 2, it is characterized in that: described nonlinear distortion envelope frequency spectrum is through power detection, follow gain and the phase-shift phase of adjusting negative feedback loop, make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
4. according to claim 1 or 2 or 3 described power amplifier linearization methods, it is characterized in that: it adopts following controlled step:
Step 1: detect feedforward cancellation loop two-way and participate in offseting signal amplitude difference Δ G and phase difference P;
Step 2: utilize Δ G and Δ P to generate the gain-controlled voltage V of feedforward cancellation loop gain and phase controller
GWith phase control voltage V
P
Step 3: negative feedback nonlinear distortion envelope frequency spectrum sampled signal ingoing power amplifier input channel;
Step 4: detect and control the negative feedback parameter and make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
5. power amplifier linearization method according to claim 4 is characterized in that: comprise following control procedure in the described step 1:
At first, make up feed-forward signal and offset loop, the input and output signal of sample-power amplifier respectively, and they are sent into the signal cancellation device simultaneously, form feed-forward signal and offset loop;
Secondly, the two-way input signal of sampled signal Canceller;
Then, detect the amplitude difference Δ G of two-way sampled signal: the two-way sampled signal is carried out magnitude demodulator respectively, and obtain to participate in the amplitude difference Δ G of offseting signal through subtracter;
At last, detect the phase difference P of two-way sampled signal: utilize phase discriminator to detect the phase difference P that obtains to participate in offseting signal.
6. power amplifier linearization method according to claim 4 is characterized in that: comprise following control procedure in the described step 2:
At first, set up feedforward cancellation loop gain control voltage V
G: adopt V
G=-K
GThe control structure of Δ G+G1 obtains gain-controlled voltage V
G, and control in real time is arranged in the gain controller of power amplifier input channel;
Secondly, set up feedforward cancellation loop phase control voltage V
P: adopt V
P=-K
PThe control structure of Δ P+P1 obtains phase control voltage V
P, and control in real time is arranged in the phase controller of power amplifier input channel;
Then, tuning K
G, G1, K
P, P1: dynamic tuning K
G, G1, K
P, P1, make Δ G and Δ P minimum, and then guarantee the good counteracting of main signal, obtain the nonlinear distortion envelope frequency spectrum sampled signal of power amplifier.
7. power amplifier linearization method according to claim 4 is characterized in that: comprise following control procedure in the described step 3:
At first, nonlinear distortion envelope frequency spectrum sampled signal is introduced the power amplifier input channel: with the nonlinear distortion envelope frequency spectrum sampled signal that obtains, after controlled gain amplification and adjustable phase shift, the input channel of power amplifier is sent in coupling;
Then, pre-distorting power amplifier input signal: power amplifier is given in nonlinear distortion envelope frequency spectrum signal that coupling is introduced and input signal stack, carries out power amplification.
8. power amplifier linearization method according to claim 4 is characterized in that: comprise following control procedure in the described step 4:
At first, detect nonlinear distortion envelope frequency spectrum power: utilize power-sensing circuit, monitoring feedforward cancellation loop is offset the nonlinear distortion envelope frequency spectrum sampled signal amplitude of output;
Then, closed-loop control predistortion effect: follow gain and the phase-shift phase of adjusting negative feedback loop, make nonlinear distortion envelope frequency spectrum sampled signal amplitude minimum.
9. linear power amplifier device of realizing the described method of claim 1, comprise feed-forward signal cancellation module (81), it is characterized in that: also comprise nonlinear distortion envelope frequency spectrum negative feedback module (84), this nonlinear distortion envelope frequency spectrum negative feedback module (84) is obtained the nonlinear distortion signal envelope spectrum information of power amplifier by feed-forward signal cancellation module (81), and with input channel and the input signal superposition modulated envelope frequency spectrum of its negative feedback to power amplifier.
10. linear power amplifier device according to claim 9, it is characterized in that: described feed-forward signal cancellation module (81) comprises coupler (8101), coupler (8102), gain controller (8103), phase controller (8104), power amplifier (8105) and coupler (8106), and the formation main channel that links to each other successively; Also comprise delay line (8110) and coupler (8111), and the input and output signal of coupler (8107) difference received power amplifier; Described two paths of signals is transported to amplitude-phase detector (8109) by coupler (8107) and coupler (8111) respectively, again by adaptive cancellation controller (8108), be connected to gain controller (8103) and phase controller (8104), and described two paths of signals outputs signal to signal cancellation device (8112).
11. linear power amplifier device according to claim 10 is characterized in that: described amplitude-phase detector (8109) comprises amplitude-phase detection module (91) and computing module (92); Wave detector (911) in the amplitude-phase detection module (91), (912) detecting signal amplitude, and by the computing circuit (921) of subtracter (913) output amplitude difference Δ G to the computing module (92); The computing circuit (922) of phase discriminator (914) phase difference output Δ P in the amplitude-phase detection module (91) to the computing module (92).
12. linear power amplifier device according to claim 9, it is characterized in that: described nonlinear distortion envelope frequency spectrum negative feedback module (84) comprises coupler (8401), controlled amplifier (8403) and phase shifter (8404), and link to each other successively, nonlinear distortion signal envelope spectrum information is fed back to the input channel of power amplifier.
13. linear power amplifier device according to claim 12, it is characterized in that: described nonlinear distortion envelope frequency spectrum negative feedback module (84) also comprises power detector (8402) and adaptive line controller (8405), power detector (8402) monitoring nonlinear distortion envelope frequency spectrum sampled signal amplitude is followed adjustment by adaptive line controller (8405) to phase shifter (8404) and controlled amplifier (8403).
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| CNA031148751A CN1516493A (en) | 2003-01-10 | 2003-01-10 | Power amplifier linearization method and linear power amplifier device |
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