Background technology
Power amplifier is as the core component in the analog communication system, and the high efficiency design in other words of its low power dissipation design is a hot issue always.The distortion information that the utilization of digital baseband pre-distortion method feeds back is sending the digital end nonlinear characteristic of compensated amplifier in advance, and the nonlinear compensation than being easier to realize self adaptation and high bandwidth becomes one of first-selection of pre-distortion method.
According to the type of feedback information, predistorter can be divided into vector method and scalar method.
So-called vector method is that amplitude and the phase information with the distorted signal by amplifier keeps fully, by with not through the primary signal time delay of amplifier align do poor, the generated error signal.As cost function, adopt adaptive algorithm to generate the predistorter coefficient error signal.This method requires height, feedback loop more complicated to the linearity of feedback loop.
The scalar rule is with the signal processing through amplifier, and power ratio inside and outside out-of-band power or the band also can be adopted adaptive algorithm as cost function, perhaps selects one as the predistorter coefficient in a plurality of fixed tables.This method does not need quadrature demodulation, and feedback loop is simple than vector method, but convergence rate may be slower.
The inventor is by the existing scalar method predistorter of investigation, and the feedback loop of finding present scalar method predistorter still exists analog feedback loop complexity, problem that analog-to-digital conversion speed is high.
For example, Fig. 1 and 2 shows the known feedback loop structure that is used for the scalar method predistorter at present respectively.
As shown in Figure 1, power amplification device 100 comprises predistorter 101, digital to analog converter (DA) 102, upconverter 103, power amplifier 104, coupler 105, low-converter 106, band pass filter (BPF) 107, power calculator 108, low pass filter (LPF) 109, analog to digital converter (AD) 110 and coefficient updating controller 111, wherein is made of the feedback loop of predistorter 101 low-converter 106, BPF 107, power calculator 108, LPF 109, AD 110 and coefficient updating controller 111.
Predistorter 101 can be used for input signal is carried out predistortion, the output pre-distorted signals.The pre-distorted signals that DA 102 can be used for that predistorter 101 is exported is converted to analog signal (for baseband signal).Upconverter 103 can be used for the baseband signal from DA 102 outputs is up-converted to radiofrequency signal.Power amplifier 104 can be used for the radiofrequency signal of upconverter 103 output is carried out output signal after power amplification and power output are amplified.Coupler 105 can be used for the output of power amplifier 104 is branched into two paths of signals, and one road signal sends via the antenna (not shown) as output signal, and another road signal is input in the feedback loop as feedback signal.Low-converter 106 can be used for the feedback signal of coupler 104 outputs is down-converted to baseband signal.BPF 107 can be used for that low-converter 106 is carried out the resulting baseband signal of down-conversion and carry out filtering, to suppress master tape signal wherein.Power calculator 108 can be used to calculate the power that BPF 107 carries out the resulting signal of filtering, as out-of-band power.The out-of-band power that LPF 109 can be used for power calculator 108 is calculated carries out low-pass filtering, to obtain the average band external power.AD 110 can be used for the average band external power from LPF109 output is carried out analog-to-digital conversion.Coefficient updating controller 111 can be used for carrying out the resulting digital averaging out-of-band power of analog-to-digital conversion according to AD 110, upgrades the coefficient of predistorter 101.
In feedback loop shown in Figure 1, the analog circuit device is many, in addition to rejection in the band of BPF 107 strict (such as requiring 60dB in the inhibition zone), shown in Fig. 3 (a).The analog filter that so just needs high-order has the big shortcoming of circuit scale.
In addition, as shown in Figure 2, power amplification device 200 comprises predistorter 101, digital to analog converter (DA) 102, upconverter 103, power amplifier 104, coupler 105, low-converter 106, analog to digital converter (AD) 201, Fourier transformation unit (FFT) 202, power calculator 203 and coefficient updating controller 111, wherein is made of the feedback loop of predistorter 101 low-converter 106, AD 201, FFT 202, power calculator 203 and coefficient updating controller 111.Except AD 201, FFT 202, power calculator 203, remaining each unit function with corresponding units shown in Figure 1 respectively is identical, and represents with identical Reference numeral, omits its detailed description at this.
In feedback loop shown in Figure 2, out-of-band power calculating is moved to numeric field, wherein AD 201 can be used for that low-converter 106 is carried out the resulting baseband signal of down-conversion and carries out analog-to-digital conversion, FFT 202 can carry out Fourier transform by AD 201 is carried out the resulting digital signal of analog-to-digital conversion, thereby obtains signal spectrum.Power calculator 203 can be used for calculating out-of-band power according to the signal spectrum from FFT 202 outputs.Though this scheme analogue device is few, to having relatively high expectations of AD, shown in Fig. 3 (b).Dynamic range (if consideration 60dB to AD, the AD that then needs effective bit number (ENOB)=10 bit at least) and sampling rate (if consider 5 subharmonic distortions, then need 5 times on adopt speed) all have high requirements, such AD often involves great expense, simultaneously the clock rate height of numeric field.
Summary of the invention
Provided hereinafter about brief overview of the present invention, so that basic comprehension about some aspect of the present invention is provided.But, should be appreciated that this general introduction is not about exhaustive general introduction of the present invention.It is not that intention is used for determining key part of the present invention or pith, neither be intended to be used for limiting scope of the present invention.Its purpose only is to provide about some notion of the present invention with the form of simplifying, with this as the preorder in greater detail that provides after a while.
Said circumstances in view of prior art, the purpose of this invention is to provide a kind of signal feedback loop and the method for power amplifier pre-distortion device and power amplification device that comprises this signal feedback loop of being used for, it can solve one or more in the prior art problem.
To achieve these goals, according to an aspect of the present invention, a kind of signal feedback loop that is used for the power amplifier pre-distortion device is provided, and it comprises: low-converter is used for the feedback signal from power amplifier output is down-converted to baseband signal or intermediate-freuqncy signal; First filter is used for low-converter is carried out the resulting baseband signal of down-conversion or intermediate-freuqncy signal is carried out first filtering, so that wherein master tape signal is tentatively suppressed, thereby exports first filtering signal; Analog to digital converter is used for first filtering signal from the output of first filter is carried out analog-to-digital conversion; Second filter is used for that analog to digital converter is carried out the resulting digital signal of analog-to-digital conversion and carries out second filtering, so that wherein master tape signal is further suppressed, thereby exports second filtering signal; Power calculator is used for calculating the out-of-band power of feedback signal according to second filtering signal from the output of second filter; And coefficient updating controller, be used for the out-of-band power that basis is calculated by power calculator, upgrade the coefficient of predistorter.
Preferably, analog to digital converter carries out the low speed sampling to first filtering signal, makes n above harmonic wave partly or entirely superpose, and wherein n is the odd number more than or equal to 3.
According to a further aspect in the invention, also provide a kind of signal feedback method that is used for the power amplifier pre-distortion device, may further comprise the steps: will down-convert to baseband signal or intermediate-freuqncy signal from the feedback signal of power amplifier output; To carrying out first filtering, so that wherein master tape signal is tentatively suppressed, thereby export first filtering signal through the resulting baseband signal of down-conversion or intermediate-freuqncy signal; First filtering signal is carried out analog-to-digital conversion; To carrying out second filtering, so that wherein master tape signal is further suppressed, thereby export second filtering signal through analog-to-digital conversion resulting digital signal; According to second filtering signal, calculate the out-of-band power of feedback signal; And, upgrade the coefficient of predistorter according to the out-of-band power of calculating.
Preferably, first filtering signal is carried out analog-to-digital conversion comprise that first filtering signal is carried out low speed samples, make n above harmonic wave partly or entirely superpose, wherein n is the odd number more than or equal to 3.
According to a further aspect in the invention, also provide a kind of power amplification device, it comprises: predistorter is used for input signal is carried out predistortion the output pre-distorted signals; Digital to analog converter is used for the pre-distorted signals that predistorter is exported is converted to analog baseband signal; Upconverter is used for the analog baseband signal from digital to analog converter output is up-converted to radiofrequency signal; Power amplifier is used for the radiofrequency signal of upconverter output is carried out output signal after power amplification and power output are amplified; Coupler is used for the output of power amplifier is branched into two paths of signals, and one road signal is gone out via antenna transmission as output signal, and another road signal is input in the aforesaid signal feedback loop as feedback signal; And aforesaid signal feedback loop.
According to a further aspect in the invention, also provide the computer program that is used to realize above-mentioned signal feedback method.
According to a further aspect in the invention, also provide computer-readable medium, recorded the computer program code that is used to realize the signal feedback method on it.
According to technique scheme of the present invention,, greatly reduce the analog circuit complexity by partial simulation loop complexity being transferred to the method for numeric field and utilizing the secondary filter structure to reduce analog-to-digital dynamic range requirement.In addition, the spectral aliasing that utilizes low speed AD to produce greatly reduces the rate request to AD under the situation that does not influence performance.Under the situation that does not have to worsen in performance, further reduced the cost of feedback loop.
Embodiment
To be described one exemplary embodiment of the present invention in conjunction with the accompanying drawings hereinafter.For clarity and conciseness, all features of actual execution mode are not described in specification.Yet, should understand, in the process of any this practical embodiments of exploitation, must make a lot of decisions specific to execution mode, so that realize developer's objectives, for example, meet and system and professional those relevant restrictive conditions, and these restrictive conditions may change to some extent along with the difference of execution mode.In addition, might be very complicated and time-consuming though will also be appreciated that development, concerning the those skilled in the art that have benefited from present disclosure, this development only is customary task.
At this, what also need to illustrate a bit is, for fear of having blured the present invention because of unnecessary details, only show in the accompanying drawings with according to closely-related apparatus structure of the solution of the present invention and/or treatment step, and omitted other details little with relation of the present invention.
Describe in detail with reference to the accompanying drawings according to the power amplification device of the embodiment of the invention and signal feedback loop wherein.
Fig. 4 shows according to the power amplification device 400 of the embodiment of the invention and the structured flowchart of signal feedback loop wherein.
As shown in Figure 4, power amplification device 400 comprises predistorter 101, digital to analog converter (DA) 102, upconverter 103, power amplifier 104, coupler 105, low-converter 106, first filter 401, AD 402, second filter 403, power calculator 404 and coefficient updating controller 111, wherein is made of the feedback loop of predistorter 101 low-converter 106, first filter 401, AD 402, second filter 403, power calculator 404 and coefficient updating controller 111.Except first filter 401, AD 402, second filter 403, power calculator 404, remaining each unit function with the corresponding units shown in Fig. 1 and 2 respectively is identical, and represents with identical Reference numeral, omits its detailed description at this.
First filter 401 can be used for low-converter 106 is carried out the resulting baseband signal of down-conversion or intermediate-freuqncy signal is carried out first filtering, wherein master tape signal is tentatively suppressed (such as suppressing master tape signal 25dB), thereby export first filtering signal, can reduce the dynamic range requirement of AD 402 like this.AD 402 can be used for first filtering signal from 401 outputs of first filter is carried out analog-to-digital conversion.Second filter 403 can be used for that AD 402 is carried out the resulting digital signal of analog-to-digital conversion and carry out second filtering, so that wherein master tape signal is further suppressed (such as suppressing master tape signal 35dB again), thereby exports second filtering signal.Power calculator 404 can be used for calculating the out-of-band power of feedback signal according to second filtering signal from 403 outputs of second filter.Because the just preliminary master tape signal that suppresses of first filter 401, than less demanding, first filter, 401 circuit scales are less to the master tape signal suppressing.After the dynamic range of AD reduced, the bit number of AD can reduce greatly.
Preferably, AD 402 can carry out the low speed sampling to first filtering signal, makes n above harmonic wave partly or entirely superpose, and wherein n is the odd number more than or equal to 3.Like this, the sampling rate of AD can reduce greatly.
For ease of understanding, at first recall sampling thheorem:
If analog signal (t), its corresponding frequency spectrum is X (f).If AD obtains signal after sampling with sample frequency fs
, its corresponding frequency spectrum is
Its corresponding frequency spectrum is:
Therefore the frequency spectrum of original analog has obtained periodic continuation with interval fs.When the relation of sample frequency fs and signal bandwidth X not simultaneously, the continuation situation difference of frequency spectrum is shown in Fig. 5 (a)~(c).The present invention has promptly utilized the situation of Fig. 5 (c), makes n (n is the odd number more than or equal to 3) inferior above harmonic wave all or part of stack after sampling of signal, and then calculates its power.
Only consider 5 subharmonic in the following legend, yet, it will be clear to one skilled in the art that for considering that the harmonic distortion more than 3 times still is suitable for.
Fig. 6 has provided 2 solution examples of digital intermediate frequency mode:
For digital intermediate frequency mode, low-converter 106 is made of frequency mixer 601 usually.
First example adopts digital intermediate frequency fif=2.5X.Adopt band stop filter that the master tape signal is tentatively suppressed, adopt the AD sampled signal of 2.5X then after, make 5 times and 3 subharmonic carry out partial stack that the high pass filter at numeric field employing cut-off frequency fc=X/2 leaches distorted signal at last.Calculate behind its power as cost function.
Another example adopts digital intermediate frequency fif=1.5X.Adopt band stop filter that the master tape signal is tentatively suppressed, adopt the AD sampled signal of 3X then after, make 5 times and 3 subharmonic carry out partial stack that the high pass filter at numeric field employing cut-off frequency fc=X leaches 3 order harmonic signal at last.Calculate behind its power as cost function.
Emulation shows the AD of the ENOB=10bit that adopts on the original use 5X, adopts the solution among Fig. 7 to use 2.5X/1.5X, and the AD of ENOB=4bit can obtain performance much at one.
Fig. 7 has provided 2 solution examples of zero intermediate frequency mode:
For the zero intermediate frequency mode, low-converter 106 is made of quadrature demodulator 701 usually, to obtain I/Q two paths of signals information.Quadrature demodulator 701 is compared complicated more with frequency mixer, be made of two-way frequency mixer cos (2 π f t)/sin (2 π f t).
First example adopts band stop filter that the master tape signal is tentatively suppressed, adopt the AD sampled signal of 2.5X then after, make 5 times and 3 subharmonic carry out partial stack that the high pass filter at numeric field employing cut-off frequency fc=X/2 leaches distorted signal at last.Calculate behind its power as cost function.
Second example adopts band stop filter that the master tape signal is tentatively suppressed, adopt the AD sampled signal of 1.5X then after, adopt the high pass filter of cut-off frequency fc=X/2 to leach 3 rd harmonic signal again.Calculate behind its power as cost function.
Describe in detail in conjunction with the accompanying drawings above according to the power amplification device of the embodiment of the invention and signal feedback loop wherein.Below in conjunction with the signal feedback method that be used for power amplifier pre-distortion device of accompanying drawing description according to the embodiment of the invention.
Fig. 8 shows the flow chart according to the signal feedback method that is used for the power amplifier pre-distortion device of the embodiment of the invention.
As shown in Figure 8, at first,, will down-convert to baseband signal or intermediate-freuqncy signal from the feedback signal of power amplifier output at step S801.
Next, at step S802, to carrying out first filtering, so that wherein master tape signal is tentatively suppressed, thereby export first filtering signal through the resulting baseband signal of down-conversion or intermediate-freuqncy signal.
Next, at step S803, first filtering signal is carried out analog-to-digital conversion.
Next, at step S804, to carrying out second filtering, so that wherein master tape signal is further suppressed, thereby export second filtering signal through analog-to-digital conversion resulting digital signal.
Next, at step S805,, calculate the out-of-band power of feedback signal according to second filtering signal.
At last, at step S806,, upgrade the coefficient of predistorter according to the out-of-band power of calculating at step S805.
Preferably, the analog-to-digital conversion process of step S803 comprises carries out the low speed sampling to first filtering signal, makes n above harmonic wave partly or entirely superpose, and wherein n is the odd number more than or equal to 3.
Detailed description had been made in the optional execution mode of other of the above-mentioned steps of this method front, in this no longer repeat specification.
In addition, obviously, also can realize in the mode that is stored in the computer executable program in the various machine-readable storage mediums according to each operating process of said method of the present invention.
And, purpose of the present invention also can realize by following manner: the storage medium that will store above-mentioned executable program code offers system or equipment directly or indirectly, and the said procedure code is read and carried out to the computer in this system or equipment or CPU (CPU).At this moment, as long as this system or equipment have the function of executive program, then embodiments of the present invention are not limited to program, and this program also can be a form arbitrarily, for example, the program carried out of target program, interpreter or the shell script that offers operating system etc.
Above-mentioned these machinable mediums include but not limited to: various memories and memory cell, semiconductor equipment, disk cell be light, magnetic and magneto optical disk for example, and other is suitable for the medium of stored information etc.
In addition, computer is by being connected to the corresponding website on the internet, and will download and be installed to according to computer program code of the present invention and carry out this program in the computer then, also can realize the present invention.
In apparatus and method of the present invention, obviously, each parts or each step can decompose and/or reconfigure.These decomposition and/or reconfigure and to be considered as equivalents of the present invention.And, carry out the step of above-mentioned series of processes and can order following the instructions naturally carry out in chronological order, but do not need necessarily to carry out according to time sequencing.Some step can walk abreast or carry out independently of one another.
Though more than describe embodiments of the invention in conjunction with the accompanying drawings in detail, should be understood that execution mode described above just is used to illustrate the present invention, and be not construed as limiting the invention.For a person skilled in the art, can make various changes and modifications above-mentioned execution mode and do not deviate from the spirit and scope of the invention.Therefore, scope of the present invention is only limited by appended claim and equivalents thereof.