CN1333604C - Pulse width modulating method and device - Google Patents
Pulse width modulating method and device Download PDFInfo
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- CN1333604C CN1333604C CNB031218954A CN03121895A CN1333604C CN 1333604 C CN1333604 C CN 1333604C CN B031218954 A CNB031218954 A CN B031218954A CN 03121895 A CN03121895 A CN 03121895A CN 1333604 C CN1333604 C CN 1333604C
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Abstract
The present invention puts forward a pulse width modulation method suitable for the envelope elimination and restoration technology, and a device for realizing the method. Firstly, output signals obtained from input amplitude signals by PWM modulation are subtracted from the input amplitude singles to extract error signals; after the output signals obtained from the input amplitude signals by PWM modulation are amplified at high efficiency, filtration signals are obtained through low-pass filtration; the low frequency part of the amplified error signals is obtained after the error signals pass through inversion, low-pass filtration and auxiliary linear amplification; the filtration signals and the low frequency part of the error signals are added to obtain modulation signals. The present invention corrects nonlinearity caused by the PWM modulation, reduces the sampling rate of the PWM modulation, improves the linearity of the signals, reduces the design difficulty of signal restoration filters, and increases passage bandwidth. Thus, the design difficulty and the integrity of EER amplifiers can be enhanced.
Description
Technical field
The present invention relates to moving communicating field, relate in particular to modulation technique field in the mobile communication system.
Technical background
In recent years, mobile communication is flourish in worldwide, mobile subscriber number sharp increase, the unprecedented anxiety of radio frequency resources.In order to effectively utilize frequency spectrum resource more, many communication systems have also adopted the higher modulation system of the availability of frequency spectrum.These modulation systems are not only modulated the phase place of carrier wave, and therefore the amplitude of simultaneously also having modulated carrier wave can produce the non-permanent envelope modulated signal of bigger peak-to-average ratio.Bigger peak-to-average ratio has proposed higher linear requirement to post a letter the especially big dynamic number weighted-voltage D/A converter of passage, broadband sender and broadband power amplifier (BPA) part of broadband.This is because semiconductor device has inevitable nonlinear characteristic under large-signal, when the broadband power amplifier is operated in the inelastic region, can produce serious intermodulation and spuious component, causes spectrum leakage, brings the serious interference to other channel or system.For this reason, many communication systems have been stipulated strict radio-frequency (RF) index, and the linearity of broadband power amplifier (BPA) has been proposed high requirement.For mobile communication equipment, the product that profit is the highest is a base station equipment, and in the base station equipment manufacturing cost the highest surely belong to radio-frequency (RF) power amplification.Therefore reducing manufacturing cost at first just needs to reduce the cost of power amplifier.
The base station mainly contains the following aspects to the requirement of power amplifier:
The linearity is good: Linear Power Amplifier is more and more adopted in the base station;
Efficient height: the major part that usually occupies power consumption;
The reliability height: but often the reliability of power amplifier is the bottleneck of system reliability;
Cost is low: often the cost of power amplifier accounts for a big chunk ratio of base station system material;
Volume is little: the major part that generally occupies system;
Maintainable strong: many is modules independently, and the monitoring and protection function is arranged;
Easily produce: the difficulty that as far as possible reduces assembling and setting.
Wherein improving the linearity and reducing cost is the double-barreled question of pendulum in face of communications equipment manufacturer.
The linearization technique development all multi-schemes occurred so far, comprising: flute card ring (Cartesian Loop), limit ring (Polar Loop), envelope elimination and recovery (Envelope Elimination and Restore, EE﹠amp; R), utilize the linear amplification (LINC) of nonlinear device/combine analog lock ring overall situation modulator (CALLUM), feedforward (Feedforward), radio frequency/intermediate frequency analog predistortion (RF/IF Predistortion), base band predistortion (Baseband Predistortion) etc.Owing to reasons such as bandwidth constraints and practicality, above-mentioned many linearization techniques are not used widely, and linearization technique and efficient enhancement techniques classification are interrelated, and difficulty has clear and definite boundary line.
EE﹠amp; The R technology is a kind of radio frequency high efficiency linearization technology, can be used for radio frequency amplifier or complete linear transmitter.Adopt EE﹠amp; R technology and switching amplifier are realized a kind of high efficiency, the scheme of wide-band linearity power amplifier cheaply, it is the focus of industry research of communicating by letter at present, can make base station/terminal equipment use the less demanding high frequency power device of linear properties just can satisfy broadband power amplifier linearity index request, thereby reduce the cost of base station equipment significantly.
So-called EE﹠amp; The R technology is meant that a signal transforms to polar coordinate system earlier, is decomposed into amplitude and phase place two parts.Respectively amplitude and phase place are amplified, merge the process that reverts to original signal then.The theory diagram of EER power amplifier is as shown in Figure 1:
At first, input signal is decomposed into amplitude and phase place two parts of signals.The amplitude tributary signal is through ovennodulation, amplification, and phase signal is called the radio-frequency carrier signal of being with phase information through phase modulation, and amplitude and carrier wave synthesize the radio frequency output signal at main power amplifier.
Wherein, the amplitude modulation(PAM) of amplitude branch road has several different methods.EE﹠amp; What use always among the R is pulse width modulation (Pulse Wide Modulation, PWM) method.
The width that PWM is meant the sampled value control impuls carrier wave that utilizes modulation signal is linear change thereupon, and that pulse amplitude keeps is constant.Simply, be with certain frequency output duty cycle and the linear continuous impulse of input signal.Fig. 2 is the legend and the parameter schematic diagram of PWM modulation.
The PWM modulation needs two input parameters: pulse frequency and pulse duty factor.Wherein, pulse frequency is similar to sampling frequency, influences the bandwidth of whole PWM passage; Pulse duty factor, the quantization error after the similar sampling of its precision.
Pulse-width modulator becomes pulse width modulating signal with non-permanent envelope amplitude conversion of signals, and this is two level switch signals of a permanent envelope, but service efficiency very high switching amplifier amplification in back recovers amplitude by a low pass filter then.For raising the efficiency, carrier signal is also carried out amplitude limit, becomes the square-wave signal of phase modulation.Main power amplifier also is a high efficiency switch amplifier.Obviously, compare traditional Linear Power Amplifier, the power supply signal of its close power amplifier no longer is constant DC source, but the envelope signal after amplifying.This system has the incomparable higher efficiency of traditional power amplifier.
EE﹠amp; Why the R technology brings high efficiency advantage, is because it with signal decomposition and be modulated to permanent envelope and amplitude on off state and phase signal, can use the high efficiency switch amplifier.
Though EE﹠amp; The R technology has so many advantage, and the difficulty of a lot of reality is arranged when still realizing, has influenced its application.Amplitude and PHASE SEPARATION make the amplitude-phase signal spectrum that very big expansion all be arranged, and require the bandwidth ratio broad of two branch roads.In addition, the PWM modulation has two characteristics: one, and the PWM modulation comes down to the process that the paired pulses phase place is modulated, and is a kind of nonlinear transformation, so it is not enough that the recovery primary signal only relies on low pass filter or integrator, also needs the nonlinear inverse conversion (being similar to) by correspondence.Its two, if PWM modulation realizes that with digital form then clock frequency equals the resolution * pulse frequency of pulse, this value is quite high.
Institute thinks that the assurance linearity, present measure are to adopt very high PWM modulation sampling rate.Simultaneously, owing to need to suppress the harmonic wave that the PWM modulation brings, it is also difficult to need maintenance amplitude and back to be used to recover to amplify the Design of Filter of back range signal again, low pass filter bandwidth constraints, the linear index of the synthetic back of influence signal.
Summary of the invention
Purpose of the present invention proposes a kind of envelope that is applicable to exactly and eliminates and recovery technology (EnvelopeElimination and Restore, EE﹠amp; R) pulse width modulation in (Pulse Wide Modulation, PWM) method and the device of realizing this method.The non-linear correction that modulation causes to PWM reduced PWM modulation sampling rate, improves the linearity of signal, reduces signal and recovers the Filter Design difficulty, increases bandwidth chahnel.Can make EE﹠amp thus; R Design of Amplifier difficulty and overall performance are improved.
A kind of pulse-width modulation method is applicable to envelope elimination and recovery technology (Envelope Eliminationand Restore, EE﹠amp; R) in, may further comprise the steps:
A, input range signal A (t) is subtracted each other the extraction error signal by output signal and the input range signal A (t) that PWM modulation obtains;
After b, the output signal that input range signal A (t) is obtained by PWM modulation are amplified through high efficiency, by low-pass filtering, picked up signal Ap (t);
C, with error signal negate described in the step a, through low-pass filtering, auxiliary linear amplification, obtain the error signal low frequency part Ek (t) that amplifies;
D, with described signal Ap of step b (t) and the described signal Ek of step c (t) addition, picked up signal Aout (t).
Step a comprises further input range signal A (t) is divided into two same signals that the PWM of leading up to modulation with another road signal subtraction, obtains error signal.
It is to be finished by switch power amplifier that high efficiency described in the step b is amplified.
A kind of device of realizing above-mentioned pulse-width modulation method, at least comprise a PWM modulator, a subtracter, a switch power amplifier, an auxiliary linear amplifier, two low pass filters, an adder, described PWM modulator is modulated the input range signal, described subtracter will obtain error signal through the signal and the former input range signal subtraction of PWM modulation, signal through the PWM modulation amplifies by described switch power amplifier again, send to first low pass filter, obtain signal Ap (t), the anti-phase error signal of obtaining after the described error signal negate is by behind second low pass filter, send to described auxiliary linear amplifier, obtain signal Ek (t), described adder obtains signal Aout (t) with signal Ap (t) and signal Ek (t) addition.
Adopt the present invention, it is non-linear to proofread and correct PWM, reduces the PWM sampling rate and requires and design difficulty, overcomes the amplitude bandwidth constraints of EER amplifier, realizes the radio frequency amplifier of high efficiency, high linearity.
Description of drawings
Fig. 1 is EE﹠amp; R digital power amplifier principle schematic;
Fig. 2 is a pwm signal waveform schematic diagram;
Fig. 3 is PWM modulation of the present invention and forward feedback correction schematic diagram;
Fig. 4 comprises EE﹠amp of the present invention; R amplifier architecture figure.
Embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described.
According to the analysis of front, the PWM of amplitude branch road modulation output comprises fundamental frequency part and abundant radio-frequency component, and the PWM modulation signal after the amplification relies on a low pass filter to recover the range signal characteristic.This has proposed very high requirement to filter characteristic, and the linearity of whole amplitude branch road is not ideal.
The present invention adopts feed-forward mode, and former amplitude signal and PWM output signal are subtracted each other, and extracts error signal.Then pwm signal is amplified with switching amplifier, and error signal is amplified with auxiliary nonlinear amplifier.At last, error signal is deducted from pwm signal, recovered range signal.
This execution mode step and apparatus structure are as shown in Figure 3.
At first, input signal A (t) enters PWM modulator 301, finishes pulse width modulation, exports two level pulse widths modulation signals, and the width of pulse comprises amplitude information.Subtracter 302 subtracts each other the output signal and the input signal A (t) of PWM modulator 301, obtains the error signal of PWM modulation back signal and A (t).Here with the output symbol negate of PWM modulator 301, that is to say that what subtracter 302 was exported is anti-phase error signal.Switch power amplifier 303 is used to amplify two level switch signals, and the output signal of PWM modulator 301 is after switch power amplifier 303 high efficiency are amplified, by a low pass filter 304 picked up signal Ap (t).
Anti-phase error signal behind low pass filter 305 filtering and auxiliary linear amplifier 306 linear amplification, error signal low frequency part Ek (t) input summer 307 that obtains amplifying.So just obtained signal Aout (t) in adder 307 and anti-phase error signal addition, characteristic is consistent with input signal A (t).
Because PWM modulation output Ap (t) contains abundant high fdrequency component, error signal E (t) is bigger.The effect of low pass filter 305 is the big high fdrequency components of filtering energy, keeps main low frequency component error.The pass band here can be than broad, and transition band requires also not strict.Ep (t) signal of low pass filter 305 outputs is exactly little error signal, through an auxiliary linear amplifier, can keep the good linearity.Synthetic in adder 307 Central Plains signal branch and error branch road, for guaranteeing the error counteracting effect, require time-delay, amplitude and the phase characteristic of two branch roads consistent.
PWM modulation of the present invention and forward feedback correction device are used for EE﹠amp; The R amplifier, whole device as shown in Figure 4.
Input signal Vin (t) is decomposed into amplitude A (t) and phase place Φ (t) through decomposing module 401, and amplitude A (t) is through foregoing PWM modulation and forward feedback correction module 402; Phase branches Φ (t) is modulated into carrier wave in carrier wave generation and amplitude limit module 403, and carries out amplitude limit.Owing to be constant envelope signal, main power amplifier can be high efficiency nonlinear amplifier.Output amplitude signal Aout (t) multiplies each other with carrier signal on main power amplifier 404 as power supply signal, obtains the radiofrequency signal Vout (t) that amplifies.
The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with the people of this technology in the disclosed technical scope of the present invention; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
Claims (4)
1, a kind of pulse width modulation (PWM) method is applicable to envelope elimination and recovery technology EE﹠amp; Among the R, it is characterized in that may further comprise the steps:
A, input range signal A (t) is subtracted each other the extraction error signal by output signal and the input range signal A (t) that PWM modulation obtains;
After b, the output signal that input range signal A (t) is obtained by PWM modulation are amplified through high efficiency, by low-pass filtering, picked up signal Ap (t);
C, with error signal negate described in the step a, through low-pass filtering, auxiliary linear amplification, obtain the error signal low frequency part Ek (t) that amplifies;
D, with described signal Ap of step b (t) and the described signal Ek of step c (t) addition, picked up signal Aout (t).
2, pulse-width modulation method as claimed in claim 1 is characterized in that, and: step a further comprises input range signal A (t) is divided into two same signals, and the PWM of leading up to modulation with another road signal subtraction, obtains error signal.
3, pulse-width modulation method as claimed in claim 1 or 2 is characterized in that: it is to be finished by switch power amplifier that the high efficiency described in the step b is amplified.
4, a kind of device of realizing the described pulse-width modulation method of claim 1, it is characterized in that: this device comprises a PWM modulator at least, a subtracter, a switch power amplifier, an auxiliary linear amplifier, two low pass filters, an adder, described PWM modulator is modulated the input range signal, described subtracter will obtain error signal through the signal and the former input range signal subtraction of PWM modulation, signal through the PWM modulation amplifies by described switch power amplifier again, send to first low pass filter (304), obtain signal Ap (t), the anti-phase error signal of obtaining after the described error signal negate is by behind second low pass filter (305), send to described auxiliary linear amplifier, obtain signal Ek (t), described adder obtains signal Aout (t) with signal Ap (t) and signal Ek (t) addition.
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| CNB031218954A CN1333604C (en) | 2003-04-17 | 2003-04-17 | Pulse width modulating method and device |
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| CNB031218954A CN1333604C (en) | 2003-04-17 | 2003-04-17 | Pulse width modulating method and device |
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| CN1333604C true CN1333604C (en) | 2007-08-22 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101090380B (en) * | 2006-06-04 | 2011-05-18 | 三星电机株式会社 | Systems and methods for linear envelope eliminating and recovering transmitters |
| CN103177699B (en) * | 2011-12-20 | 2015-12-09 | 上海天马微电子有限公司 | Data processing method in the sequence liquid crystal display device of field |
| US9054940B2 (en) * | 2013-10-25 | 2015-06-09 | Mitsubishi Electric Research Laboratories, Inc. | System and method for linearizing power amplifiers |
| CN104836574B (en) * | 2015-04-30 | 2018-03-30 | 中国科学院微电子研究所 | A kind of envelope tracking power amplifier structure of automatic aligning |
| CN105277801B (en) * | 2015-08-10 | 2018-08-07 | 工业和信息化部电信研究院 | A method of measuring modulation pulse parameter |
| CN109716681B (en) * | 2016-09-27 | 2021-02-12 | 华为技术有限公司 | Power amplifier, radio remote unit and base station |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001097384A2 (en) * | 2000-06-12 | 2001-12-20 | Cirrus Logic, Inc. | Real time correction of a digital pwm amplifier |
| EP1227579A2 (en) * | 2000-12-28 | 2002-07-31 | Nokia Corporation | Method and apparatus for providing digital error correction for a class D power stage |
| WO2003030373A1 (en) * | 2001-09-28 | 2003-04-10 | Sony Corporation | Delta-sigma modulation apparatus and signal amplification apparatus |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001097384A2 (en) * | 2000-06-12 | 2001-12-20 | Cirrus Logic, Inc. | Real time correction of a digital pwm amplifier |
| EP1227579A2 (en) * | 2000-12-28 | 2002-07-31 | Nokia Corporation | Method and apparatus for providing digital error correction for a class D power stage |
| WO2003030373A1 (en) * | 2001-09-28 | 2003-04-10 | Sony Corporation | Delta-sigma modulation apparatus and signal amplification apparatus |
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