CN102118334A - Method and device for processing digital predistortion - Google Patents

Abstract

The invention discloses a method and device for processing digital predistortion. The method comprises the steps of: respectively filtering a radio-frequency signal of each frequency band; collecting the nonlinear intermodulation distortion of each frequency band; synchronizing the nonlinear intermodulation distortion of each frequency band with the input signal of the frequency band; and updating digital predistortion factors by utilizing the synchronized signals. In the invention, through respectively filtering the radio frequency of each frequency band and carrying out common digital predistortion processing on digits, a high efficient digital predistortion processing effect of the digital predistortion can be achieved under the condition of low-complicated hardware.

Description

A kind of digital pre-distortion processing method and device

Technical field

The present invention relates to signal processing technology, particularly a kind of digital pre-distortion processing method and device.

Background technology

Frequency range according to China Mobile's planning is divided into four frequency ranges of F/A/D/E, following expression meaning:

Table: F/A/D/E four frequency ranges planning

Following wideband RRU (Radio Remote Unit, the Remote Radio Unit) demand is to satisfy the common antenna of these four frequency ranges, and the common hardware platform of A+F frequency range is greatly saved hardware cost and hardware design complexity.But present industry is only accomplished the application of 30MA+F, and D frequency range/continuous 50MHz of E frequency range does not also have formal product.

The application of wideband RRU adopts mixed mode will inevitably become main flow, and promptly TD (Time Division, time-division) and LTE (Long Term Evolution, Long Term Evolution) are total to platform.Can introduce the demand of bigger bandwidth for the application of E frequency range 50M and follow-up D frequency range.Mixed mode promptly needs TD and TD-LTE (TD-SCDMA Long Term Evolution, TD-SCDMA Long Term Evolution; TD-SCDMA:TimeDivision Synchronized Code Division Multiple Access, TD SDMA inserts) be total to platform, for the band applications of 50M, be that the LTE of 2 20M and the TD of 1 10M share frequency band.Perhaps be that for example the LTE of 2 20M and the LTE of 1 10M share the 50MHz frequency band to the LTE signal entirely.

Widebandization is the clear and definite developing direction of industry carrier frequency technology, relates to whole industry chains such as device (intermediate frequency chip), power amplifier (wideband power tube), complete machine.Reason is that network operator's wireless cellular network multiband is disposed and the LTE technology is introduced for setting up the lifting significantly of supporting bandwidth fully, and the concrete condition brief introduction is as follows.

Main flow Virtual network operator (VDF/TIM/Orange/AT﹠amp; T) the broadband demand of RRU:

American-European mainstream carrier just proposes strong demand for the RRU radio-frequency module is broadband many years ago.Target be injection frequently path realize 200MHz or high bandwidth more.Do not need to piece together, be unfavorable for that like this power and the carrier resource between the frequency range shared with a plurality of narrow radio frequency modules, the many poor reliability of components and parts, volume/weight is big; Perhaps the wideband of the above signal of 50MHz is handled continuously.

Wideband RRU technology comprises two aspect technical schemes for this reason:

(1) enlargement technology of one-segment bandwidth of operation for example expands to 40～50MHz from present supported 30MHz bandwidth of operation, and for example the D/E frequency range adopts continuous 50MHx～60MHz;

(2) multiband adopts the single section of striding power amplifier mode.Just the shared power amplifier of F+A has determined that like this FA merges at numerical portion.

Industry supports that generally the average output power spectrum density is 10W/10MHz now simultaneously, and TD-SCDMA and TDD-LTE are consistent substantially, the signal power of the signal of 50MHz bandwidth output just needs 50W so, export large-signal power like this and be bound to adopt DPD (Digital PreDistortion, digital pre-distortion) technology, how making good use of the DPD technology among the wideband RRU also is the difficult problem that industry faces.

The deficiencies in the prior art are:

Prior art is difficult to solve feedback problem, and for example the feedback of A+F generally need adopt ZIF (Zero-IF, zero intermediate frequency) mode or adopt 500MHZ non real-time ADC (Analog-DigitalConverter, analog to digital converter) to carry out signals collecting.But adopt the unbalanced problem of the general difficult solution I/Q of ZIF, and adopt 500MHZ non real-time ADC to carry out signals collecting, this kind of ADC can't be shared with normal receive path on the one hand, and one side price comparison costliness makes whole RRU product price be unable to come down in addition.

Summary of the invention

Technical problem solved by the invention is to provide a kind of digital pre-distortion processing method and device, in order to guarantee DPD performance among the wideband RRU when simplifying the RRU design.

A kind of digital pre-distortion processing method is provided in the embodiment of the invention, has comprised the steps:

Respectively the radiofrequency signal of each frequency range is carried out filtering;

Gather the Nonlinear Intermodulation Distortion of each frequency range;

The Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Signal after utilizing synchronously upgrades the DPD coefficient.

A kind of digital predistortion process apparatus also is provided among the present invention, has comprised:

Filtration module is used for respectively the radiofrequency signal of each frequency range being carried out filtering;

Acquisition module is used to gather the Nonlinear Intermodulation Distortion of each frequency range;

Synchronization module is used for the Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Update module, the signal after being used to utilize synchronously upgrades the DPD coefficient.

Beneficial effect of the present invention is as follows:

In the technical scheme that the embodiment of the invention provides, by each frequency range radio frequency is distinguished filtering, the processing of the common DPD of numeral makes DPD can obtain DPD treatment effect efficiently under low complicated hardware condition.

Description of drawings

Fig. 1 is a digital pre-distortion processing method implementing procedure schematic diagram in the embodiment of the invention;

Fig. 2 be in the embodiment of the invention power amplifier output the F+A signal schematic representation;

Fig. 3 is the F-band signal schematic representation behind the intermediate frequency feedback frequency overlapped-resistable filter in the embodiment of the invention;

Fig. 4 is the A frequency band signals schematic diagram behind the intermediate frequency feedback frequency overlapped-resistable filter in the embodiment of the invention;

Fig. 5 is intermediate-freuqncy signal and the synchronous amplitude adjustment of a feedback signal amplitude comparison afterwards schematic diagram in the embodiment of the invention;

Fig. 6 is a digital predistortion process apparatus structural representation in the embodiment of the invention;

Fig. 7 is digital predistortion process apparatus mode one structural representation in the embodiment of the invention;

Fig. 8 is digital predistortion process apparatus mode two structural representations in the embodiment of the invention;

Fig. 9 is F-band and an A frequency range intermodulation information schematic diagram in the embodiment of the invention;

Figure 10 is for shunt in the embodiment of the invention or close the DPD effect schematic diagram on road;

Figure 11 is the signal of the spectrogram before and after the predistortion in the embodiment of the invention.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described.

Provide a kind of in the embodiment of the invention at the DPD hardware corridor design of striding the frequency band signals feedback.In scheme, adopt and respectively radiofrequency signal to be carried out filtering, gather the Nonlinear Intermodulation Distortion of frequency range separately then, from frequency range separately respectively filtering to frequency range collection separately, synchronously after, carry out the renewal of DPD coefficient again.

Fig. 1 is a digital pre-distortion processing method implementing procedure schematic diagram, as shown in the figure, can comprise the steps:

Step 101, respectively the radiofrequency signal of each frequency range is carried out filtering;

Step 102, gather the Nonlinear Intermodulation Distortion of each frequency range;

Step 103, the Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Signal after step 104, the utilization synchronously upgrades the DPD coefficient.

Below mainly come concrete enforcement of each step described with the example that is treated to of F/A frequency range, but, essence by the scheme implementation that discloses in the specification and obtain effect, those skilled in the art also should know and how to implement in the frequency range of other combinations, the processing of F/A frequency range only is used to instruct those skilled in the art specifically how to implement the present invention, but do not mean that technical scheme that the embodiment of the invention provides only can be used for the processing of F/A frequency range, can need determine in corresponding frequency range combination, to adopt the technological means that is equal to realize same effect in conjunction with practice in the implementation process.

In step 101, when respectively the radiofrequency signal of each frequency range being carried out filtering, can comprise:

The radiofrequency signal of obtaining each frequency range respectively is set by switch;

Each frequency band signals that obtains is respectively entered frequency mixer;

Signal after the mixing is fed back frequency overlapped-resistable filter through intermediate frequency.

The example that is treated to the F/A frequency range, feedback path F/A carries out radio frequency analog filtering respectively, only obtain F-band radiofrequency signal or A frequency range radiofrequency signal each time by the switch setting, the F-band that obtains respectively/A frequency band signals enters shared frequency mixer subsequently, the anti-aliasing intermediate-frequency filter of intermediate frequency amplifier and intermediate frequency.Wherein, intermediate frequency amplifier can be thought the part of fader.

When obtaining the radiofrequency signal of each frequency range respectively, with the example that is treated to of F/A frequency range, the signal separately of F-band and A frequency range can adopt the mode of acquisition time, the signal of system acquisition F-band at first just, and then gather the signal of A frequency range.

Below by the difference of spectrum distribution before and after the filtering processing of rf filtering is described, Fig. 2 for power amplifier export the F+A signal schematic representation, Fig. 2 is the spectrogram that is coupled and from power amplifier, has comprised the signal spectrum of F-band and A frequency range.

The F-band signal schematic representation of Fig. 3 after for intermediate frequency feedback frequency overlapped-resistable filter, the F/A frequency range respectively by the signal after the intermediate frequency feedback frequency overlapped-resistable filter compression separately as shown in Figure 3, passband is the signal spectrum of F-band among the figure, the signal that can find out the A frequency range is effectively compressed, complete reservation the signal and the intermodulation information of F-band.The A frequency band signals schematic diagram of Fig. 4 after for intermediate frequency feedback frequency overlapped-resistable filter, passband is the signal spectrum of A frequency range among the figure, can find out that the signal of F-band is effectively compressed, complete reservation the signal and the intermodulation information of A frequency range.

In step 102, when gathering the Nonlinear Intermodulation Distortion of each frequency range, can comprise:

ADC samples to filtered signal;

Each frequency band signals after the sampling is down-converted to zero-frequency;

Signal after the down-conversion is carried out filtering extraction.

In the enforcement, with the example that is treated to of F/A frequency range, what gather is that the F-band or the signal of A frequency range at first all are down-converted to fundamental frequency (zero-frequency), and the image signal that collects by the low pass filter filters out real number keeps useful signal then.Because the signal that ADC sampling obtains only has F-band/A frequency band signals, the signal of independent frequency range is down-converted to filtering extraction behind the zero-frequency, (the real number sampling causes to finish the inhibition of mirror image.In concrete the enforcement,, can reduce the requirement of ADC sampled signal speed because F/A is sampled respectively.

In step 103, carry out when synchronous at input signal the Nonlinear Intermodulation Distortion of each frequency range and this frequency range, the example that is treated to the F/A frequency range, the original F/A frequency band signals of the signal of the independent frequency range of F/A and input carries out related synchronization respectively, accurately adjust the synchronous of F/A signal, finish the gain adjustment of frequency band signals separately simultaneously.

In concrete the enforcement, establishing the correlation length that transmits and receive data is (length that sends tx_d and received signal fb_d all is) DEFAULT_XCORR_L, exemplary value 4096.

[max_value，position]＝xcorr(fb_d，tx_d)

Obtain the relevant present position position of greatest measure by related operation, delay delay_m in loop obtains transmitting:

delay_m＝positon-DEFAULT_XCORR_L

By postponing the delay_m size, just can make emission and feedback signals synchronous then to transmitting.Fig. 5 is the synchronous amplitude adjustment of an intermediate-freuqncy signal and feedback signal amplitude comparison afterwards schematic diagram, and Fig. 5 is illustrated as with the signal amplitude after the step calibration.

Adopt root mean square amplitude calibration algorithm to be:

$y=y\·\frac{\mathrm{RMS}\left(z\right)}{\mathrm{RMS}\left(y\right)}$

Wherein RMS (z) is as follows:

$\mathrm{RMS}\left(z\right)=\sqrt{\frac{\underset{i=1}{\overset{M}{\mathrm{\Σ}}}(\mathrm{zi}+\mathrm{zj})\·(\mathrm{zi}-\mathrm{zj})}{M}}$

The feedback signal and the use rms amplitude calibration method that transmits, make | y|=|z|, like this before self application filtering, the feedback signal and the amplitude basically identical that transmits, so the multinomial that assessment obtains is handled function | F () |=|| can't change the amplitude of signal.Fig. 5 has just shown feedback signal and the amplitude that transmits, the comparison of amplitude on the time domain after all obtaining synchronously calibrating.

In step 104, the signal after the utilization synchronously upgrades the DPD coefficient and can comprise dual mode, is respectively:

1, mode one

Finish amplitude calibration synchronously after each frequency band signals fed back respectively, form the feedback signal of F+A;

Each frequency band signals is carried out carrying out CFR (Crest FactorReduction, peak factor eliminates) processing after the information stack forms the F+A signal;

F+A signal and the F+A signal behind the CFR that power amplifier is fed back carry out the processing of DPD coefficient update;

With the coefficient after upgrading the DPD passage is upgraded.

In the enforcement, the example that is treated to the F/A frequency range, frequency band signals is by same step calibration separately, by the time after the signal of F-band and A frequency range is all gathered and is finished, and then be mixed to separately frequency range, and form the feedback digital signal of F+A, compare the adjustment of finishing gain with the F+A signal of input, simultaneously carry out same step calibration once more, finish the calculating of the DPD coefficient update of F+A subsequently.Concrete, the F/A signal of frequency range separately finishes respectively after the synchronization gain adjustment separately, the stack of F/A signal generates the signal of F+A, do the renewal of DPD coefficient handles with the F+A signal of input, generate the DPD coefficient of F+A, the DPD coefficient of F+A carries out pre-distortion to the F+A signal, finishes the digital pre-distortion of wideband F+A and handles.

2, mode two

With each frequency range after synchronously signal and the input signal of this frequency range carry out the DPD coefficient update respectively;

The input signal of each frequency range is carried out the CFR processing respectively;

Coefficient after signal behind each frequency range CFR and the renewal of this frequency range is carried out DPD to be upgraded.

Under this mode, F-band and A frequency range are carried out DPD coefficient update separately.

In the enforcement, each frequency range feedback adopts different Nyquist (Nyquist) districts.

With the example that is treated to of F/A frequency range, F-band feedback adopts a Nyquist district, and A frequency range feedback adopts the 2nd Nyquist district, and transmitting and receiving like this can a shared LO, saving device number.

Based on same inventive concept, a kind of digital predistortion process apparatus also is provided in the embodiment of the invention, because the principle that these equipment are dealt with problems is similar to the digital pre-distortion processing method, so the enforcement of these equipment can repeat part and repeat no more referring to the enforcement of method.

Fig. 6 is the digital predistortion process apparatus structural representation, as shown in the figure, can comprise in the device:

Filtration module 601 is used for respectively the radiofrequency signal of each frequency range being carried out filtering;

Acquisition module 602 is used to gather the Nonlinear Intermodulation Distortion of each frequency range;

Synchronization module 603 is used for the Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Update module 604, the signal after being used to utilize synchronously upgrades the DPD coefficient.

In the enforcement, the enforcement of filtration module, acquisition module, synchronization module can be the same, and the signal after update module utilization synchronously can comprise dual mode when the DPD coefficient is upgraded, therefore the structural representation of two embodiment is provided, be respectively: Fig. 7 is digital predistortion process apparatus mode one structural representation, Fig. 8 is digital predistortion process apparatus mode two structural representations, is that example describes the execution mode that installs with two figure below.

In the enforcement, filtration module is used for respectively the radiofrequency signal of each frequency range being carried out filtering; Its concrete structure can for:

Switch is used to control passing through of each frequency range radiofrequency signal;

Frequency mixer links to each other with switch, and the signal that passes through is carried out mixing;

Intermediate frequency feedback frequency overlapped-resistable filter links to each other with frequency mixer, and the signal after the mixing is carried out filtering.

In the enforcement, the radiofrequency signal of obtaining each frequency range respectively is set by switch; Then each frequency band signals that obtains is respectively entered frequency mixer; At last the signal after the mixing is fed back frequency overlapped-resistable filter through intermediate frequency.

In the enforcement, acquisition module is used to gather the Nonlinear Intermodulation Distortion of each frequency range; Its concrete structure can for:

ADC is used for filtered signal is sampled;

Low-converter is used for each frequency band signals after the sampling is down-converted to zero-frequency;

Filter is used for the signal after the down-conversion is carried out filtering extraction.

In the enforcement, the signal after update module 604 is used to utilize synchronously upgrades the DPD coefficient; Its concrete structure can be following two kinds:

1, as shown in Figure 7:

The power amplifier ultramagnifier is finished amplitude calibration after being used for each frequency band signals fed back respectively synchronously, forms the feedback signal of F+A;

Stack and CFR processor are used for each frequency band signals is carried out carrying out the CFR processing after the information stack forms the F+A signal;

Coefficient updating module, the F+A signal and the F+A signal behind the CFR that are used for power amplifier is fed back carry out the processing of DPD coefficient update;

The passage update module is used for the coefficient after upgrading the DPD passage being upgraded.

2, as shown in Figure 8:

Coefficient updating module, be used for each frequency range after synchronously signal and the input signal of this frequency range carry out the DPD coefficient update respectively;

The CFR processor is used for the input signal of each frequency range is carried out CFR respectively;

The frequency range update module is used for that the coefficient after signal behind each frequency range CFR and the renewal of this frequency range is carried out DPD and upgrades.

Fig. 9 is F-band and A frequency range intermodulation information schematic diagram, as shown in the figure, in above-mentioned implementation process, the mutual intermodulation information of F-band and A frequency range fall in the mutual band or near.No matter adopt which kind of embodiment, all need effectively to gather F+A intermodulation information separately, reason is as follows:

If power amplifier to the transfer function of F+A signal is: two signal f1 of F-band and f2, two signal a1 of A frequency range and a2 then have:

S _OUT＝f(S _f+S _a)＝f(S _f1+S _f2+S _a1+S _a2)＝C ₀+C ₁×(S _f1+S _f2+S _a1+F _a2)+C ₂×(S _f1+S _f2+S _a1+S _a2) ²+C ₃×(S _f1+S _f2+S _a1+S _a2) ³+.....

C0 wherein, C1, C2, C3, C4...... are the temperature variant constant of power discharging device decision itself.Because device non-linear, can think C0, C1, C2, C3, C4 is not equal to 0, and it is that of C3 is to B that coefficient is only arranged as can be seen from the above equation ₁Or B ₂Contribution is arranged, makes a concrete analysis of as follows:

${(S_f+S_a)}^3=S_f^3+3\&times;{\mathrm{<figure-callout\; id="2"\; label="S\; f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f^{}\&times;S_a+3\&times;S_f\&times;S_a^2+S_a^3$

$={({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f+S_{f2})}^3+3\&times;{({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f+S_{f2})}^2\&times;(S_{a1}+S_{a2})+3\&times;({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f+S_{f2})\&times;{(S_{a1}+S_{a2})}^2+{(S_{a1}+S_{a2})}^3$

$={({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f+S_{f2})}^3+{(S_{a1}+S_{a2})}^3+3\&times;({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f^1+{\mathrm{<figure-callout\; id="2"\; label="S\; f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f^2+2*S_{f1}{S}_{f2})\&times;(S_{a1}+S_{a2})+$

$3\&times;(S_{a1}^2+S_{a2}^2+2*S_{a1}{S}_{a2})\&times;({\mathrm{<figure-callout\; id="1"\; label="S\; f"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f+S_{f2})$

Third order intermodulation between the F/A is distributed as:

${(S_f+S_a)}^3=S_f^3+3\&times;{\mathrm{<figure-callout\; id="2"\; label="S\; f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">S</figure-callout>}}_f^{}\&times;S_a+3\&times;S_f\&times;S_a^2+S_a^3$

It is as follows to drop near the interior or intermodulation information of F-band or A frequency range band

These intermodulation information be distributed in the signal or near, seriously influencing the DPD effect, have only the signal of power amplifier output F+A, these intermodulation information just can effectively be gathered.The DPD renewal is carried out near in the band intermodulation collection, and the coefficient that calculates just can effectively eliminate the influence of PA (power amplifier, power amplifier) third order intermodulation.

Figure 10 is for shunt or close the DPD effect schematic diagram on road, and Figure 11 is the spectrogram signal before and after the predistortion, as shown in the figure:

s _{FA_IF}(n)＝(I _F+jQ _F)·exp(jω _f(n))+(I _A+jQ _A)·exp(jω _a(n))

＝(I _{F_IF}+j _{QF_IF})+(I _{A_IF}+jQ _{A_IF})＝(I _{F_IF}+I _{A_IF})+j(Q _{F_IF}+Q _{A_IF})

Digital signal is modulated into radiofrequency signal fcos ω at radio frequency by quadrature modulator through after DAC and the low pass filter _f+ acos ω _a:

s _{FA_RF}(n)＝(I _{F_IF}+I _{A_IF})·cosω _lo-(Q _{F_IF}+Q _{A_IF})·sinω _lo

＝(I _{F_IF}·cosω _lo-Q _{F_IF}·sinω _lo)+(I _{A_IF}·cosω _lo-Q _{A_IF}·sinω _lo)

＝fcosω _f+acosω _a

The intermodulation that this F+A signal presents after by PA is as follows:

FA＝c1·(fcosω _f+acosω _a)+c3·(fcosω _f+acosω _a) ³+c5·(fcosω _f+acosω _a) ⁵+L

＝c1·S+c3·S ³+c5·S ⁵+L

$S^3={(f\cos {\mathrm{\&omega;}}_f+a\cos {\mathrm{\&omega;}}_a)}^3$

$=(f\cos {\mathrm{\&omega;}}_f+a\cos {\mathrm{\&omega;}}_a)\&CenterDot;({\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">f</figure-callout>}}^2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_f+a^2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_a+2f\&CenterDot;a\&CenterDot;\cos {\mathrm{\&omega;}}_f\&CenterDot;\cos {\mathrm{\&omega;}}_a)$

$=\cos {\mathrm{\&omega;}}_f\&CenterDot;(\frac{3f^3}{4}+\frac{3{\mathrm{<figure-callout\; id="2"\; label="fa"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">fa</figure-callout>}}^2}{2})+\cos {\mathrm{\&omega;}}_a\&CenterDot;(\frac{3a^3}{4}+\frac{3f^{2}a}{2})+L$

$S^5=S^3(\frac{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}(1+\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_f)+\frac{a^2}{2}(1+\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_a)+2\mathrm{fa}\cos {\mathrm{\&omega;}}_f\&CenterDot;\cos {\mathrm{\&omega;}}_a)$

$={\cos \mathrm{\&omega;}}_f\&CenterDot;(\frac{{5f}^5}{8}+\frac{{30f}^3{a}^2}{8}+\frac{{15\mathrm{fa}}^4}{8})+{\cos \mathrm{\&omega;}}_a\&CenterDot;(\frac{{5a}^2}{8}+\frac{{30f}^2{a}^3}{8}+\frac{{15f}^{4}a}{8})+K$

$\mathrm{FA}=\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;({f\cos \mathrm{\&omega;}}_f+a\cos {\mathrm{\&omega;}}_a)+c3\&CenterDot;{({f\cos \mathrm{\&omega;}}_f+{a\cos \mathrm{\&omega;}}_a)}^3+c5\&CenterDot;{({f\cos \mathrm{\&omega;}}_f+a{\cos \mathrm{\&omega;}}_a)}^5+L$

$=\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;S+c3\&CenterDot;S^5+c5\&CenterDot;S^5+L$

$=\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;(f\&CenterDot;{\cos \mathrm{\&omega;}}_f+a\&CenterDot;{\cos \mathrm{\&omega;}}_a)+c3\&CenterDot;[{\cos \mathrm{\&omega;}}_f\&CenterDot;(\frac{{3f}^3}{4}+\frac{{3\mathrm{<figure-callout\; id="2"\; label="fa"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">fa</figure-callout>}}^2}{2})+{\cos \mathrm{\&omega;}}_a\&CenterDot;(\frac{{3a}^2}{4}+\frac{{3f}^{2}a}{2})]+$

$c5\&CenterDot;[{\cos \mathrm{\&omega;}}_f\&CenterDot;(\frac{{5f}^5}{8}+\frac{{30f}^3{a}^2}{8}+\frac{{15\mathrm{fa}}^4}{8})+{\cos \mathrm{\&omega;}}_a\&CenterDot;(\frac{{5a}^5}{8}+\frac{{30f}^2{a}^3}{8}+\frac{{15f}^{4}a}{8})]+L$

$={\cos \mathrm{\&omega;}}_f\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;f+c3\&CenterDot;(\frac{{3f}^3}{4}+\frac{{3\mathrm{<figure-callout\; id="2"\; label="fa"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">fa</figure-callout>}}^2}{2})+c5\&CenterDot;(\frac{{5f}^5}{8}+\frac{{30f}^3{a}^2}{8}+\frac{{15\mathrm{fa}}^4}{8})]+$

$\cos {\mathrm{\&omega;}}_a\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;a+c3\&CenterDot;(\frac{{3a}^3}{4}+\frac{{3f}^{2}a}{2})+c5\&CenterDot;(\frac{{5a}^5}{8}+\frac{{30f}^2{a}^3}{8}+\frac{{15f}^{4}a}{8})]+L$

$=f\&CenterDot;{\cos \mathrm{\&omega;}}_f\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;c3\&CenterDot;({\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000034854060000012.png,HDA0000034854060000031.png"\; state="\{\{state\}\}">f</figure-callout>}}^2+{2a}^2)+c5\&CenterDot;(f^4+{6f}^2{a}^2+{3a}^4)]+$

$a\&CenterDot;{\cos \mathrm{\&omega;}}_a\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1+c3\&CenterDot;(a^2+{2f}^2)+c5\&CenterDot;(a^4+6f^2{a}^2+{3f}^4)]+L$

Come at ω as can be seen from top formula _fIn the frequency range, the fundamental frequency of F-band is arranged not only, three rank, five rank band informations also have the signal of A frequency range, and this is consistent with the conclusion that top F/A respectively sends 2 single-tones.Same ω _aIn the frequency range, the fundamental frequency of A frequency range is arranged not only, three rank, five rank band informations also have the signal of F-band, and the signal of F and A also falls in the corresponding frequency range simultaneously.

The intermodulation information of all frequencies can't all be calculated, and drops on the F/A interior intermodulation component of frequency band separately as long as consideration F/A asks mutually, and this component size is relevant with signal bandwidth.Though the F+A signal is numerous by frequency component after the power amplifier, but can represent by DPD coefficient and model, so the size of high order components such as interactional three rank of F/A, five rank all can be reacted in coefficient and model, following formula has shown the Mathematical Modeling of F+A intermodulation in the DPD passage;

z _FA(n)＝y _f(n)·[c1·+c3·(|y _f(n)| ²+2|y _a(n)| ²)+c5·(|y _f(n)| ⁴+6|y _f(n)| ²|y _a(n)| ²+|y _a(n)| ⁴)]

+y _a(n)·[c1·+c3·(|y _f(n)| ²+2|y _a(n)| ²)+c5·(|y _f(n)| ⁴+6|y _f(n)| ²|y _a(n)| ²+|y _a(n)| ⁴)]

If the Memorability of taking into account system, the derivation of hardware LUT (Look-Up-Table, look-up table) model is as follows:

$z_{\mathrm{FA}}\left(n\right)=$

$\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\begin{array}{c}{y}_f(n-k)\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;+c3\&CenterDot;({\left|y_f(n-k)\right|}^2+2{\left|y_a(n-k)\right|}^2)+c5\&CenterDot;({\left|y_f(n-k)\right|}^4+6{\left|y_f(n-k)\right|}^2{\left|y_a(n-k)\right|}^2+{\left|y_a(n-k)\right|}^4)]\\ y_a(n-k)\&CenterDot;[\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000034854060000031.png"\; state="\{\{state\}\}">c</figure-callout>}1\&CenterDot;+c3\&CenterDot;({\left|y_f(n-k)\right|}^2+2{\left|y_a(n-k)\right|}^2)+c5\&CenterDot;({\left|y_f(n-k)\right|}^4+6{\left|y_f(n-k)\right|}^2{\left|y_a(n-k)\right|}^2+{\left|y_a(n-k)\right|}^4)]\end{array}$

$=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}(y_f(n-k)\&CenterDot;{\mathrm{LUT}}_k|y_f(n-k)|+y_a(n-k)\&CenterDot;{\mathrm{LUT}}_k|y_a(n-k)\left|\right)$

$=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}(y_f(n-k)\&CenterDot;{\mathrm{LUT}}_k|y_f(n-k)\left|\right)+\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{y}_a(n-k)\&CenterDot;{\mathrm{LUT}}_k\left|y_a(n-k)\right|$

Through the derivation of these a series of formula, the model of the single relatively frequency range of the model of F+A only need increase a LUT table and each multiplier of many K.Other hardware resource and one-segment the same.

Certainly it is also conceivable that the influence of seven rank intermodulations, and the influence of even-order intermodulation, can finish according to similar derivation.

1, set input parameter M={K, P}, signal length is N

2, import reference signal z (n) and feedback signal y (n)

U＝[u ₁，L?u _kpL，u _KP] _N*KP，u _kp＝[u _kp(0)，L，u _kp(N-1)] ^T，

u _k1(n)＝y(n-k)，

u _k3(n)＝y(n-k)·(|y(n-k)| ²+2|y(n-k)| ²)，

u _k5(n)＝y(n-k)·(|y(n-k)| ⁴+6|y(n-k)| ²|y(n-k)| ²+|y(n-k)| ⁴)

M

z＝Uc，KP×KP

z＝[z(0)，L，z(N-1)] ^T，

$\hat{c}={\left(U^{H}U\right)}^{-1}{U}^H\&CenterDot;z$

After obtaining pre-distortion coefficients by top formula, just can design look-up table the F+A signal of input is carried out the DPD coefficient update.

As seen from the above-described embodiment, in the technical scheme that the embodiment of the invention provides, feedback path radio-frequency (RF) FEEDBACK filtering respectively respectively, Frequency Band Selection switch.The signal and the forward direction F+A signal that are merged into feedback F+A after respectively with step calibration once more compare, and obtain the DPD coefficient.

Concrete, feedback path F/A carries out radio frequency analog filtering respectively, only obtain F-band radiofrequency signal or A frequency range radiofrequency signal each time by the switch setting, the F-band that obtains respectively/A frequency band signals enters shared frequency mixer subsequently, the anti-aliasing intermediate-frequency filter of intermediate frequency amplifier and intermediate frequency.

Concrete, the signal that the ADC sampling obtains only has F-band/A frequency band signals (because F/A is sampled respectively, can reduce the requirement of ADC sampled signal speed), the signal of independent frequency range is down-converted to filtering extraction behind the zero-frequency, finish the inhibition (the real number sampling causes) of mirror image, the original F/A frequency band signals of the signal of the independent frequency range of F/A and input carries out related synchronization respectively, accurately adjusts the synchronous of F/A signal, finishes the gain adjustment of frequency band signals separately simultaneously.

Concrete, the F/A signal of frequency range separately finishes respectively after the synchronization gain adjustment separately, the stack of F/A signal generates the signal of F+A, do the renewal of DPD coefficient handles with the F+A signal of input, generate the DPD coefficient of F+A, the DPD coefficient of F+A carries out pre-distortion to the F+A signal, finishes the digital pre-distortion of wideband F+A and handles.

Concrete, the F-band feedback adopts a Nyquist district, and A frequency range feedback adopts the 2nd Nyquist district, and transmitting and receiving like this can a shared LO, saving device number.

By the filtering respectively of this radio frequency, the processing of the common DPD of numeral makes DPD can obtain DPD treatment effect efficiently under low complicated hardware condition.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (11)

1. a digital pre-distortion DPD processing method is characterized in that, comprises the steps:

Respectively the radiofrequency signal of each frequency range is carried out filtering;

Gather the Nonlinear Intermodulation Distortion of each frequency range;

The Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Signal after utilizing synchronously upgrades the DPD coefficient.

2. the method for claim 1 is characterized in that, when respectively the radiofrequency signal of each frequency range being carried out filtering, comprising:

The radiofrequency signal of obtaining each frequency range respectively is set by switch;

Each frequency band signals that obtains is respectively entered frequency mixer;

Signal after the mixing is fed back frequency overlapped-resistable filter through intermediate frequency.

3. the method for claim 1 is characterized in that, when gathering the Nonlinear Intermodulation Distortion of each frequency range, comprising:

Analog to digital converter ADC samples to filtered signal;

Each frequency band signals after the sampling is down-converted to zero-frequency;

Signal after the down-conversion is carried out filtering extraction.

4. the method for claim 1 is characterized in that, when the signal after utilizing synchronously upgrades the DPD coefficient, comprising:

Finish amplitude calibration synchronously after each frequency band signals fed back respectively, form the feedback signal of F+A;

Each frequency band signals is carried out information stack to be formed and carries out peak factor behind the F+A signal and eliminate CFR and handle;

F+A signal and the F+A signal behind the CFR that power amplifier is fed back carry out the processing of DPD coefficient update;

With the coefficient after upgrading the DPD passage is upgraded.

5. the method for claim 1 is characterized in that, when the signal after utilizing synchronously upgrades the DPD coefficient, comprising:

With each frequency range after synchronously signal and the input signal of this frequency range carry out the DPD coefficient update respectively;

The input signal of each frequency range is carried out CFR respectively;

Coefficient after signal behind each frequency range CFR and the renewal of this frequency range is carried out DPD to be upgraded.

6. the method for claim 1 is characterized in that, each frequency range feedback adopts different Nyquist Nyquist districts.

7. a digital predistortion process apparatus is characterized in that, comprising:

Filtration module is used for respectively the radiofrequency signal of each frequency range being carried out filtering;

Acquisition module is used to gather the Nonlinear Intermodulation Distortion of each frequency range;

Synchronization module is used for the Nonlinear Intermodulation Distortion of each frequency range and the input signal of this frequency range are carried out synchronously;

Update module, the signal after being used to utilize synchronously upgrades the DPD coefficient.

8. device as claimed in claim 7 is characterized in that filtration module comprises:

Switch is used to control passing through of each frequency range radiofrequency signal;

Frequency mixer links to each other with switch, and the signal that passes through is carried out mixing;

Intermediate frequency feedback frequency overlapped-resistable filter links to each other with frequency mixer, and the signal after the mixing is carried out filtering.

9. device as claimed in claim 7 is characterized in that acquisition module comprises:

ADC is used for filtered signal is sampled;

Low-converter is used for each frequency band signals after the sampling is down-converted to zero-frequency;

Filter is used for the signal after the down-conversion is carried out filtering extraction.

10. device as claimed in claim 7 is characterized in that update module comprises:

The power amplifier ultramagnifier is finished amplitude calibration after being used for each frequency band signals fed back respectively synchronously, forms the feedback signal of F+A;

Stack and CFR processor are used for each frequency band signals is carried out carrying out the CFR processing after the information stack forms the F+A signal;

Coefficient updating module, the F+A signal and the F+A signal behind the CFR that are used for power amplifier is fed back carry out the processing of DPD coefficient update;

The passage update module is used for the coefficient after upgrading the DPD passage being upgraded.

11. device as claimed in claim 7 is characterized in that, update module comprises:

Coefficient updating module, be used for each frequency range after synchronously signal and the input signal of this frequency range carry out the DPD coefficient update respectively;

The CFR processor is used for the input signal of each frequency range is carried out CFR respectively;

The frequency range update module is used for that the coefficient after signal behind each frequency range CFR and the renewal of this frequency range is carried out DPD and upgrades.

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