CN110518885A - A kind of digital predistortion circuit and its spuious offset method - Google Patents
A kind of digital predistortion circuit and its spuious offset method Download PDFInfo
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- CN110518885A CN110518885A CN201910732047.XA CN201910732047A CN110518885A CN 110518885 A CN110518885 A CN 110518885A CN 201910732047 A CN201910732047 A CN 201910732047A CN 110518885 A CN110518885 A CN 110518885A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
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Abstract
The invention discloses a kind of digital predistortion circuit and its spuious offset method, it is related to field of communication technology, digital predistortion circuit includes predistortion device DPD, power amplifier PA and the coupler being sequentially connected, it is equipped with a weighting block between the predistortion device DPD and power amplifier PA, offsets signal generation module equipped with spuious between the weighting block and coupler；The spuious signal generation module that offsets generates signal identical as the spurious signal amplitude, opposite in phase for extracting spurious signal from the output signal of coupler, offsets signal as spuious；The weighting block is used to carry out vector superposed by the output signal of the predistortion device DPD and the spuious signal that offsets, and superimposed signal is sent to power amplifier PA.Digital predistortion circuit provided by the invention efficiently solves the problems, such as that local oscillator leakage is exceeded, DAC is spuious exceeded, and cost is relatively low, good product performance.
Description
Technical field
The present invention relates to fields of communication technology, and in particular to a kind of digital predistortion circuit and its spuious offsets method.
Background technique
With the development of linearity modulation technique, high order modulation technique can provide good spectrum efficiency, but due to PA
(Power Amplifier, power amplifier) it is non-linear, the fluctuation envelope signal generated after modulation can cause subsequent PA to produce
Raw IMD (Intermodulation Distortion, intermodulation distortion), intermodulation distortion IMD often show adjacent frequency interference, in
Interference phenomenon, therefore, it is necessary to carry out linearization process to power amplifier PA.
In order to carry out linearization process to power amplifier PA, produce pre-distortion technology, principle be in modulator and
A nonlinear device is inserted between power amplifier PA, using the nonlinear device as DPD (Digital Pre-
Distortion, predistortion device) so that predistortion device DPD and power amplifier PA as a whole from the point of view of, gain
Characteristic is linear.
Intermodulation component is an important factor for influencing power amplifier PA, and in a wireless communication device, the non-linear of device leads to
2 entered simultaneously or multiple high reject signals generation phase inter-modulation can often be made, and generate new frequency content, this phenomenon claims
For intermodulation.According to the signal order for generating intermodulation, intermodulation component be divided into IM2 (Second Order Intermodulation, two
Rank intermodulation component), IM3 (Third Order Intermodulation, third-order intermodulation product), IM4 (Fourth Order
Intermodulation, quadravalence intermodulation component) and IM5 (Fifth Order Intermodulation, fifth order intermodulation component),
And odd-multiple component will affect larger.
Influence due to third-order intermodulation product IM3 and fifth order intermodulation component IM5 to power amplifier PA is bigger, and three ranks
Intermodulation component IM3 and fifth order intermodulation component IM5 can be by second order intermodulation product IM2 and quadravalence intermodulation component IM4 and former base band signal
Modulation generates, as long as therefore control second order intermodulation product IM2 that predistortion device DPD is generated and four intermodulation component IM4 be
Number, the third-order intermodulation product IM3 for generating it with power amplifier PA and former modulates baseband signals and fifth order intermodulation component IM5 phase
Position makes on the contrary, theoretically then can be very big or fully cancel whole third-order intermodulation product IM3 and fifth order intermodulation component IM5
Linearisation is presented in power amplifier PA, to significantly inhibit harmonic intermodulation, reduce inband distortion.
Shown in Figure 1, existing digital predistortion circuit uses reaction type adaptive technique, is estimated by DPD coefficient
Module and predistortion device DPD generate pre-distorted signals, form feedback loop via coupler.
However, due to introducing predistortion device DPD, digital predistortion circuit is easy to appear that local oscillator leakage is exceeded, DAC is miscellaneous
The problems such as exceeded is dissipated, causes spuious problem more serious.
In the prior art, above-mentioned spuious in order to solve the problems, such as, usually using transmission power is reduced, increase band outer filter etc.
Means.
But, on the one hand, the method for reducing transmission power can not play the ability of power amplifier, keep high power amplifier covert
It is used as low power amplifier, wastes cost, properties of product can be also decreased obviously, for example coverage area reduces, energy through walls
Power dies down；The spuious of part baseband portion simultaneously exceeded can not be solved by reducing the power of power amplifier.
On the other hand, increase band outer filter not only higher cost, and since filter is analog device, when needing to filter
When the spuious relatively passband removed, filter can not provide enough degree of suppression, thus can not effectively solve the problems, such as it is spuious, together
When, also can lead to the decline of properties of product because of filter bring excess loss, as transmission power is not up to standard, coverage area compared with
Ability small, through walls dies down.
Summary of the invention
In view of the deficiencies in the prior art, the purpose of the present invention is to provide a kind of digital predistortion circuits, effectively
Solve the problems, such as that local oscillator leakage is exceeded, DAC is spuious exceeded, cost is relatively low, good product performance.
To achieve the above objectives, the technical solution adopted by the present invention is that:
A kind of digital predistortion circuit, including predistortion device DPD, power amplifier PA and the coupler being sequentially connected,
It is equipped with a weighting block between the predistortion device DPD and power amplifier PA, is set between the weighting block and coupler
Have and spuious offsets signal generation module；
The spuious signal generation module that offsets for extracting spurious signal from the output signal of coupler, and generate with
The spurious signal amplitude is identical, opposite in phase signal, offsets signal as spuious；
The weighting block is used to fold the output signal of the predistortion device DPD and the spuious signal progress vector that offsets
Add, and superimposed signal is sent to power amplifier PA.
Based on the above technical solution, the spuious signal generation module that offsets includes:
Processing unit is used to successively carry out IQ demodulation low-pass filtering to the output signal of coupler, obtains spuious letter
Number, and AD sampling is carried out to spurious signal；
Detecting signal unit is used to detect the amplitude and phase of the spurious signal；
Converting unit is used to adjust the spurious signal according to the amplitude and phase that detect, obtain with it is described spuious
Signal amplitude is identical, opposite in phase spuious offsets signal.
Based on the above technical solution, it is equipped with DPD coefficient between the predistortion device DPD and coupler and estimates mould
Block, the DPD coefficient estimation module are used to calculate DPD coefficient according to the signal function model of power amplifier PA.
Based on the above technical solution, the DPD coefficient estimation module is also used to before calculating DPD coefficient, right
The output signal of coupler successively carries out analog filtering, IQ demodulation, low-pass filtering, AD sampling processing.
Based on the above technical solution, the weighting block is multiplier or simulated power synthesizer.
Based on the above technical solution, the coupler is that lumped parameter directional coupler or distribution parameter orient coupling
Clutch.
The present invention also provides a kind of the spuious of above-mentioned digital predistortion circuit to offset method, comprising steps of
Input signal Input successively passes through after predistortion device DPD and power amplifier PA, is exported by coupler,
Obtain output signal Output；
The spuious signal generation module that offsets extracts spurious signal from the output signal Output of coupler, and generates and be somebody's turn to do
Spurious signal amplitude is identical, opposite in phase signal, offsets signal as spuious；
Weighting block by the output signal of the predistortion device DPD and it is spuious offset signal carry out it is vector superposed, and will
Superimposed signal is sent to power amplifier PA.
Based on the above technical solution, described spuious to offset output signal of the signal generation module from coupler
Spurious signal is extracted in Output, and the specific steps for generating signal identical as the spurious signal amplitude, opposite in phase include:
IQ demodulation low-pass filtering is successively carried out to the output signal of coupler, obtains spurious signal, and to spurious signal
Carry out AD sampling；
Detect the amplitude and phase of the spurious signal；
The spurious signal is adjusted according to the amplitude and phase detected, obtains, phase identical as the spurious signal amplitude
Opposite spuious in position offsets signal.
Based on the above technical solution, the spuious of digital predistortion circuit offsets method, further comprises the steps of:
The DPD coefficient estimation module calculates DPD coefficient according to the signal function model of power amplifier PA, described pre-
Distortion device DPD carries out predistortion correction according to the DPD coefficient being calculated.
Based on the above technical solution, the DPD coefficient estimation module further includes step before calculating DPD coefficient
It is rapid: analog filtering, IQ demodulation, low-pass filtering, AD sampling processing are successively carried out to the output signal of coupler.
Compared with the prior art, the advantages of the present invention are as follows: digital predistortion circuit of the invention is using vector superposed
Mode come realize it is spuious offset, efficiently solve that the local oscillator leakage being easy to appear in digital predistortion circuit is exceeded, DAC is spuious super
The problems such as mark；The ability for effectively playing power amplifier, is efficiently used high power power amplifier, has maximally utilized cost, and can subtract
Filter cost is lacked, so that cost is relatively low；Meanwhile it will not be worn because of the decline of properties of product caused by spuious eliminate, coverage area
Wall ability does not have obvious deterioration.
Detailed description of the invention
Fig. 1 is the structural block diagram of digital predistortion circuit in the prior art；
Fig. 2 is the structural block diagram of digital predistortion circuit in the embodiment of the present invention；
Fig. 3 is the spuious structural block diagram for offseting signal generation module in the embodiment of the present invention.
Specific embodiment
Invention is further described in detail with reference to the accompanying drawings and embodiments.
Shown in Figure 2, the embodiment of the present invention provides a kind of digital predistortion circuit, including the predistorter being sequentially connected
Part DPD, power amplifier PA and coupler are equipped with a weighting block between the predistortion device DPD and power amplifier PA,
Signal generation module is offseted equipped with spuious between the weighting block and coupler.
The spuious signal generation module that offsets for extracting spurious signal from the output signal of coupler, and generate with
The spurious signal amplitude is identical, opposite in phase signal, offsets signal as spuious；
The weighting block is used to fold the output signal of the predistortion device DPD and the spuious signal progress vector that offsets
Add, and superimposed signal is sent to power amplifier PA.
The working principle of the digital predistortion circuit of the embodiment of the present invention are as follows: it is described it is spuious offset signal generation module according to
The output signal of coupler, which is generated, identical with spurious signal amplitude, opposite in phase spuious offsets signal, the weighting block general
The output signal of the predistortion device DPD and it is spuious offset signal carry out it is vector superposed, can be by predistortion after vector superposed
Spurious signal in the output signal of device DPD offsets, then the signal after spuious offset is sent to power amplifier PA, finally
Realize the linearisation output of power amplifier PA.
The principle of spuious cancellation techniques in embodiments of the present invention is the synthesis superposition of signal phasor, and signal is sat in pole
A vector is characterized as under mark, using there is the constant amplitude reverse phase vector signal of identical information feature to synthesize therewith with the vector
Offset the signal.Digital predistortion circuit in the embodiment of the present invention realized by the way of vector superposed it is spuious offset, have
Effect solves the problems such as local oscillator leakage being easy to appear in digital predistortion circuit is exceeded, DAC is spuious exceeded.
On the one hand, the digital pre-distortion compared with the method for reducing transmission power in the prior art, in the embodiment of the present invention
Circuit effectively plays the ability of power amplifier, is efficiently used high power power amplifier, has maximally utilized cost.
On the other hand, compared with increasing the method with outer filter in the prior art, the number in the embodiment of the present invention is pre-
Distortion circuit reduces filter cost, and can form higher degree of suppression, to solve to connect when the spuious comparison that needs filter out
When nearly passband, the problem of analog filter can not provide enough degree of suppression.It will not be because under properties of product caused by spuious eliminate
Drop, coverage area, ability through walls do not have obvious deterioration.
Shown in Figure 3, further, the spuious signal generation module that offsets includes processing unit, signal detection
Unit and converting unit.
Processing unit is used to successively carry out IQ demodulation low-pass filtering to the output signal of coupler, obtains spurious signal,
And AD sampling is carried out to spurious signal；Detecting signal unit is used to detect the amplitude and phase of the spurious signal；Converting unit
For adjusting the spurious signal according to the amplitude and phase detected, phase phase identical as the spurious signal amplitude is obtained
It is anti-spuious to offset signal.
Further, in embodiments of the present invention, DPD coefficient is equipped between the predistortion device DPD and coupler
Estimation module, the DPD coefficient estimation module are used to calculate DPD coefficient according to the signal function model of power amplifier PA.
Further, the DPD coefficient estimation module is also used to before calculating DPD coefficient, the output to coupler
Signal successively carries out analog filtering, IQ demodulation, low-pass filtering, AD sampling processing.
In embodiments of the present invention, the weighting block is a kind of module that can be realized multiple signals synthesis, commonly
Weighting block has multiplier or simulated power synthesizer, and in practical applications, carrying out corresponding choose according to different scenes is
It can.In general, in the lower occasion of frequency, i.e. the frequency occasion that is lower than 1GHZ generally uses multiplier architecture, higher in frequency
Occasion, i.e. frequency are greater than the occasion of 1GHZ, generally use the structure of simulated power synthesizer.
In embodiments of the present invention, the coupler is a kind of to be widely used in penetrating for power distribution or power synthetic technique
Frequency microwave passive component, common coupler circuit structure include two class of lumped parameter device and distribution parameter device, that is, are divided into
Lumped parameter directional coupler and distribution parameter directional coupler.In practical applications, it is accordingly selected according to different scenes
It takes, in the lower occasion of frequency, i.e. occasion of the frequency lower than 1GHZ, lumped parameter directional coupler is generally used, in frequency
The higher occasion of rate, i.e. frequency are greater than the occasion of 1GHZ, generally use distribution parameter directional coupler.
The embodiment of the invention also provides offseting method based on the spuious of above-mentioned digital predistortion circuit, comprising steps of
S1: input signal Input successively passes through after predistortion device DPD and power amplifier PA, defeated by coupler
Out, output signal Output is obtained；
S2: the spuious signal generation module that offsets extracts spurious signal from the output signal Output of coupler, and generates
Signal identical as the spurious signal amplitude, opposite in phase, offsets signal as spuious；
S3: weighting block by the output signal of the predistortion device DPD and it is spuious offset signal carry out it is vector superposed, and
Superimposed signal is sent to power amplifier PA.
Closer, described spuious to offset output signal of the signal generation module from coupler in above-mentioned steps S2
Spurious signal is extracted in Output, and the specific steps for generating signal identical as the spurious signal amplitude, opposite in phase include:
IQ demodulation low-pass filtering is successively carried out to the output signal of coupler, obtains spurious signal, and to spurious signal
Carry out AD sampling；
Detect the amplitude and phase of the spurious signal；
The spurious signal is adjusted according to the amplitude and phase detected, obtains, phase identical as the spurious signal amplitude
Opposite spuious in position offsets signal.
Further, the spuious of above-mentioned digital predistortion circuit offsets method, further comprises the steps of: the DPD coefficient and estimates
Meter module calculates DPD coefficient according to the signal function model of power amplifier PA, constructs look-up table LUT, the predistorter
Part DPD carries out predistortion correction according to the DPD coefficient being calculated.
In embodiments of the present invention, the DPD coefficient estimation module further comprises the steps of: before calculating DPD coefficient
Analog filtering is successively carried out to the output signal of coupler, the low frequency spur signal and harmonic wave for getting rid of signal are believed
Number；
Zero intermediate frequency IQ demodulation is carried out to the signal after analog filtering；
Low-pass filtering is carried out to the signal after IQ demodulation, filters out the radio-frequency component of IQ demodulator output；
AD sampling is carried out to the signal after low-pass filtering.
Spuious in the embodiment of the present invention offset method by the way of vector superposed realize it is spuious offset, effectively solve
The problems such as local oscillator leakage being easy to appear in digital predistortion circuit is exceeded, DAC is spuious exceeded；Effectively play the energy of power amplifier
Power is efficiently used high power power amplifier, has maximally utilized cost, and can reduce filter cost so that cost compared with
It is low；Meanwhile will not be because of the decline of properties of product caused by spuious eliminate, coverage area, ability through walls do not have obvious deterioration.
The present invention is not limited to the above-described embodiments, for those skilled in the art, is not departing from
Under the premise of the principle of the invention, several improvements and modifications can also be made, these improvements and modifications are also considered as protection of the invention
Within the scope of.The content being not described in detail in this specification belongs to the prior art well known to professional and technical personnel in the field.
Claims (10)
1. a kind of digital predistortion circuit, including predistortion device DPD, power amplifier PA and the coupler being sequentially connected,
It is characterized in that:
Be equipped with a weighting block between the predistortion device DPD and power amplifier PA, the weighting block and coupler it
Between be equipped with and spuious offset signal generation module；
The spuious signal generation module that offsets generates miscellaneous with this for extracting spurious signal from the output signal of coupler
Scattered signal amplitude is identical, opposite in phase signal, offsets signal as spuious；
The weighting block be used for by the output signal of the predistortion device DPD and it is spuious offset signal carry out it is vector superposed,
And superimposed signal is sent to power amplifier PA.
2. digital predistortion circuit as described in claim 1, which is characterized in that described spuious to offset signal generation module packet
It includes:
Processing unit is used to successively carry out IQ demodulation low-pass filtering to the output signal of coupler, obtains spurious signal, and
AD sampling is carried out to spurious signal；
Detecting signal unit is used to detect the amplitude and phase of the spurious signal；
Converting unit is used to adjust the spurious signal according to the amplitude and phase detected, obtain and the spurious signal
Amplitude is identical, opposite in phase spuious offsets signal.
3. digital predistortion circuit as described in claim 1, it is characterised in that: the predistortion device DPD and coupler it
Between be equipped with DPD coefficient estimation module, the DPD coefficient estimation module is based on the signal function model according to power amplifier PA
Calculate DPD coefficient.
4. digital predistortion circuit as claimed in claim 3, it is characterised in that: the DPD coefficient estimation module is also used to
Before calculating DPD coefficient, to the output signal of coupler successively carry out analog filtering, IQ demodulation, low-pass filtering, at AD sampling
Reason.
5. digital predistortion circuit as described in claim 1, it is characterised in that: the weighting block is multiplier or simulation function
Rate synthesizer.
6. digital predistortion circuit as described in claim 1, it is characterised in that: the coupler is lumped parameter directional couple
Device or distribution parameter directional coupler.
7. a kind of as the spuious of digital predistortion circuit as claimed in any one of claims 1 to 6 offsets method, which is characterized in that
Comprising steps of
Input signal Input successively passes through after predistortion device DPD and power amplifier PA, is exported, is obtained by coupler
Output signal Output；
The spuious signal generation module that offsets extracts spurious signal from the output signal Output of coupler, and generates spuious with this
Signal amplitude is identical, opposite in phase signal, offsets signal as spuious；
Weighting block by the output signal of the predistortion device DPD and it is spuious offset signal carry out it is vector superposed, and will superposition
Signal afterwards is sent to power amplifier PA.
8. a kind of the spuious of digital predistortion circuit as claimed in claim 7 offsets method, which is characterized in that described spuious right
The signal generation module that disappears extracts spurious signal from the output signal Output of coupler, and generates and the spurious signal amplitude phase
Together, the specific steps of the signal of opposite in phase include:
IQ demodulation low-pass filtering is successively carried out to the output signal of coupler, obtains spurious signal, and carry out to spurious signal
AD sampling；
Detect the amplitude and phase of the spurious signal；
The spurious signal is adjusted according to the amplitude and phase detected, obtains, phase phase identical as the spurious signal amplitude
It is anti-spuious to offset signal.
9. a kind of the spuious of digital predistortion circuit as claimed in claim 7 offsets method, which is characterized in that further include step
It is rapid:
The DPD coefficient estimation module calculates DPD coefficient, the predistortion according to the signal function model of power amplifier PA
Device DPD carries out predistortion correction according to the DPD coefficient being calculated.
10. a kind of the spuious of digital predistortion circuit as claimed in claim 9 offsets method, which is characterized in that the DPD system
Number estimation module further comprises the steps of: before calculating DPD coefficient and successively carries out analog filtering, IQ to the output signal of coupler
Demodulation, low-pass filtering, AD sampling processing.
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