CN109428610A - Feedback circuit unit, ROF wireless transmitter and the method for eliminating non-linear distortion - Google Patents

Feedback circuit unit, ROF wireless transmitter and the method for eliminating non-linear distortion Download PDF

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Publication number
CN109428610A
CN109428610A CN201710759323.2A CN201710759323A CN109428610A CN 109428610 A CN109428610 A CN 109428610A CN 201710759323 A CN201710759323 A CN 201710759323A CN 109428610 A CN109428610 A CN 109428610A
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China
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signal
digital
unit
feedback
link
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CN201710759323.2A
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CN109428610B (en
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包红强
韦前华
张慧剑
程琪
韩冬
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02Transmitters
    • H04B1/04Circuits
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02Transmitters
    • H04B1/04Circuits
    • H04B1/0475Circuits with means for limiting noise, interference or distortion
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02Transmitters
    • H04B1/04Circuits
    • H04B2001/0408Circuits with power amplifiers
    • H04B2001/0433Circuits with power amplifiers with linearisation using feedback

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Optical Communication System (AREA)
  • Transmitters (AREA)

Abstract

The embodiment of the present application discloses a kind of feedback circuit unit, ROF wireless transmitter and the method for eliminating non-linear distortion, for realizing the linearisation of ROF wireless transmitter.A kind of feedback circuit unit provided by the embodiments of the present application includes: digital analog converter ADC, digital processing element and the first non-linear unit;ADC obtains digital feedback signal for receiving the analog feedback signal being coupled out from transmitting link, and by analog feedback signal progress digital-to-analogue conversion, to be output to digital processing element;Digital processing element is handled as digital baseband signal for computer equipment use for receiving the digital feedback signal of ADC output, and by digital feedback signal, and is exported to the first nonlinear block;First nonlinear block for receiving the digital baseband signal of digital processing element output, and is transferred to DPD processing unit.

Description

Feedback circuit unit, ROF wireless transmitter and the method for eliminating non-linear distortion
Technical field
This application involves the communications field more particularly to a kind of feedback circuit unit, ROF wireless transmitter and eliminate non-linear The method of distortion.
Background technique
It is either wireless in traditional radio transmission rack structure or light carrier radio communication (radio-over-fiber, ROF) It all can include power amplifier (power amplifier, PA) in RRU, for signal to be amplified to suitable function in transmitter Rate.In traditional radio transmission rack structure, PA is most important nonlinear elements, does not generate mistake in signal amplification process to allow Very it is necessary to PA progress linearization process, wherein digital pre-distortion (digital is commonly used for the linearization process of PA Pre-distortion, DPD) scheme, real-time sampling is carried out to the output signal of PA, to sample obtained feedback signal to main letter Number correction is compensated, this sample circuit constitutes feed circuit.
As shown in Figure 1, being existing wireless transmitter framework, baseband signal (101) reduces (crest by crest factor Factor reduction, CFR) and DPD processing unit (102) after, by digital analog converter (digital to Analog converter, DAC) (103) be converted into analog signal, using up-conversion and low level signal amplification unit (104), mould Quasi- signal enters PA (105), in a part of signal of PA output coupling, by down coversion and feedback unit (108), then by simulation number Analog signal is converted to digital signal by word converter (analog to digital converter, ADC) (107), by CFR And DPD processing unit (102) is handled.It receives signal and then passes through down coversion and receiving unit (110), using receives link ADC (109) be converted to digital signal, be sent in baseband signal and handled.
However, for existing ROF wireless transmitter framework, on the basis of existing wireless transmitter framework, uplink Link and downlink both increase ROF circuit and fiber section, referring to Fig. 2, due to ROF and optical fiber in feedback circuit unit For non-linear components, the signal being coupled out from PA (203) output end is then sent through at DPD after feedback circuit unit (204) It manages unit (201), at this moment signal will generate non-linear distortion, it can be understood as be sent in the signal of DPD processing unit (201) Non-linear component both included PA and downlink ROF and optical fiber generate non-thread sexual element, also include feedback circuit unit ROF and optical fiber in non-thread sexual element so that DPD processing unit cannot obtain PA output actual signal characteristic, lead to DPD Downlink cannot be distinguished when carrying out DPD processing to downlink (the ROF main fiber of PA and downlink) in processing unit It is non-linear or feedback link non-linear, so that system linearization effect is deteriorated, affect system performance.
Summary of the invention
The embodiment of the present application provides a kind of feedback circuit unit, ROF wireless transmitter and the side for eliminating non-linear distortion Method, for realizing the linearisation of ROF wireless transmitter.
The first aspect of the embodiment of the present application provides a kind of feedback circuit unit, is applied on ROF wireless transmitter, institute It states feedback circuit unit to be located on the feedback link of the ROF wireless transmitter, the feedback circuit unit includes: digital simulation Converter ADC, digital processing element and the first non-linear unit, first non-linear unit includes optical fiber;The ADC's is defeated Enter end to be connected with the transmitting link of the ROF wireless transmitter, the output of the input terminal of the digital processing element and the ADC End is connected, and the input terminal of first non-linear unit is connected with the output end of the digital processing element, and described first is non-thread Property unit output end be connected with the input terminal of digital predistorter DPD processing unit, the DPD processing unit is contained in described ROF wireless transmitter;The ADC, for receiving from the analog feedback signal that is coupled out of transmitting link, and by the simulation Feedback signal carries out digital-to-analogue conversion and obtains digital feedback signal, to be output to the digital processing element;The digital processing list Member is handled for receiving the digital feedback signal of the ADC output, and by the digital feedback signal as digital baseband letter Number for computer equipment use, and export to first nonlinear block;First nonlinear block, for receiving The digital baseband signal of digital processing element output is stated, and is transferred to the DPD processing unit.In the embodiment of the present application, feedback Circuit unit uses first analog-signal transitions as digital signal, then passes through the optical fiber and ROF module in the first nonlinear block Digital signal is sent to DPD processing unit, since digital signal transmits generated distortion by optical fiber, relative to analog signal Generated distortion is transmitted by optical fiber to be much smaller, and meets the requirement of system linearization, and be output to conversion from transmitting link For this section components of digital signal, linear original part can be used, ensure that the linear characteristic of feedback link.
In a kind of possible design, in the first implementation of the embodiment of the present application first aspect, the feedback Circuit unit further includes down-converter unit, and the output end of the down-converter unit is connected with the input terminal of the ADC, the lower change The input terminal of frequency unit is connected with the transmitting link of the ROF wireless transmitter;The down-converter unit, for reducing the mould The carrier frequency of quasi- feedback signal.In this implementation, feedback circuit unit can also include down-converter unit, increase this Shen Please embodiment implementation.
In a kind of possible design, in second of implementation of the embodiment of the present application first aspect, the ROF without The transmitting link of line transmitter further includes power amplifier PA and the second non-linear unit, and second non-linear unit includes light Carrier radio communication ROF and optical fiber, the input terminal of the PA are connected with the output end of second non-linear unit;The ADC's It includes: the input terminal of the ADC and the output end phase of the PA that input terminal is connected with the transmitting link of the ROF wireless transmitter Even;Or, the input terminal of the ADC is connected with the output end of second non-linear unit;Or, input terminal and the institute of the ADC The output end for stating PA is connected, and the input terminal of the ADC is connected with the output end of second non-linear unit.This implementation In, the several ways that ADC is connected with transmitting link have been refined, have made the embodiment of the present application that more there is operability.
In a kind of possible design, in the third implementation of the embodiment of the present application first aspect, described first Nonlinear block further includes single fiber bi-directional receiving-transmitting secondary module BOSA, and the BOSA is used to complete turn of radiofrequency signal and optical signal It changes, so that the digital baseband signal transmits on the optical fiber.In this implementation, the interior of the first nonlinear block has been refined Hold, increases the implementation of the embodiment of the present application.
The second aspect of the embodiment of the present application provides a kind of ROF wireless transmitter, including feedback link, digital pre-distortion Device DPD processing unit and transmitting link, the transmitting link includes power amplifier PA and the second non-linear unit, and described second Non-linear unit includes light carrier radio communication ROF and optical fiber, the output of the input terminal of the PA and second non-linear unit End is connected, which is characterized in that the feedback link includes such as feedback circuit unit of any of claims 1-2, institute State transmitting link input terminal be connected with the output end of the DPD processing unit, the input terminal of the DPD processing unit with it is described The output end of feedback link is connected;The transmitting link, for receiving initial baseband signal, the initial baseband signal passes through institute Become distorted signal after stating the second non-linear unit;The feedback link, the distorted signal for being exported from the transmitting link In be coupled out analog feedback signal, and the analog feedback signal is handled to obtain digital baseband signal to export to described DPD processing unit;The DPD processing unit, for receiving the digital baseband signal of the feedback link output, and according to described Digital baseband signal carries out linear pre-distortion to the signal received from base band, obtains pre-distorted signals, and by the pre- mistake True signal is output to the transmitting link;The transmitting link is also used to receive the predistortion letter from the DPD processing unit Number, and handled the distorted signal for distortion free signal according to the pre-distorted signals, and the distortion free signal is passed through Antenna is emitted.In the embodiment of the present application, increased feedback circuit unit is used first analog-signal transitions as digital signal, Digital signal is sent to by optical fiber in the first nonlinear block and ROF module by DPD processing unit again, since digital signal is logical Distortion caused by optical fiber transmission is crossed, is much smaller relative to analog signal by being distorted caused by optical fiber transmission, is met and be The requirement of system linearisation, and be output to from transmitting link and be converted to this section components of digital signal, linear original part can be used, protect The linear characteristic of ROF wireless transmitter is demonstrate,proved.
In a kind of possible design, in the first implementation of the embodiment of the present application second aspect, the transmitting Link includes that analog-digital converter DAC, the second non-linear unit and power amplifier PA, second non-linear unit include Light carrier radio communication ROF and optical fiber;The input terminal of the DAC is connected with the output end of the DPD, second non-linear unit Input terminal be connected with the output end of the DAC, the input terminal of the PA is connected with the output end of second non-linear unit; The DAC, the digital signal for exporting the DPD processing unit carry out digital-to-analogue conversion and obtain analog signal, and will be described Analog signal output is to second non-linear unit;Second non-linear unit, for receiving described in the DAC output Analog signal, and give the analog signal transmission to the PA;The PA, the mould for exporting second non-linear unit Emitted after quasi- signal amplification by antenna.In this implementation, the connected several ways of ADC fish transmitting link have been refined, Make the embodiment of the present application that more there is operability.
In a kind of possible design, in second of implementation of the embodiment of the present application second aspect, the transmitting Link further includes upconverting unit, and the output end of the upconverting unit is connected with the input terminal of the DAC, the up-conversion list The input terminal of member is connected with the input terminal of second non-linear unit;The upconverting unit, for number described in Linear Amplifer The carrier frequency of word signal.In this implementation, transmitting link can also include down-converter unit, increase the embodiment of the present application Implementation.
In a kind of possible design, in the third implementation of the embodiment of the present application second aspect, the ROF without Line transmitter includes at least one described transmitting link, at least one described transmitting link is corresponding with a feedback link. In this implementation, the scene that ROF wireless transmitter may include multiple transmitting links is provided, the embodiment of the present application is increased Realization scene.
The third aspect of the embodiment of the present application provides a kind of method for eliminating non-linear distortion, and the method is applied to The transmitting link of ROF wireless transmitter, which is characterized in that the transmitting link receives initial baseband signal, by the transmitting The transmission of first nonlinear block of link obtains distorted signal, is coupled out analog feedback signal from the distorted signal, It is characterized in that, comprising: the analog feedback signal received progress digital-to-analogue conversion is obtained into digital feedback signal;The number is anti- Feedback signal is handled to obtain digital baseband signal;It is optical signal to be transmitted on optical fiber by the digital baseband transmission system; Pre-distorted signals are calculated according to the digital baseband signal, the pre-distorted signals are sent to the transmitting link, with So that the transmitting link carries out power compensation to the initial baseband signal according to the pre-distorted signals.
It is described to connect in the first implementation of the embodiment of the present application third aspect in a kind of possible design Before the analog feedback signal progress digital-to-analogue conversion received obtains digital feedback signal, the method also includes: reduce the mould The carrier frequency of quasi- feedback signal.In this implementation, the mode for reducing carrier frequency has been added, so that the embodiment of the present application Realization process is more abundant.
As can be seen from the above technical solutions, the embodiment of the present application has the advantage that feedback circuit unit using first handle Analog-signal transitions are digital signal, then digital signal is sent to DPD by optical fiber in the first nonlinear block and ROF module Processing unit is produced relative to analog signal by optical fiber transmission since digital signal transmits generated distortion by optical fiber Raw distortion is much smaller, and meets the requirement of system linearization, and be output to from transmitting link and be converted to this part of digital signal Linear original part can be used in component, ensure that the linear characteristic of feedback link.
Detailed description of the invention
Fig. 1 is the possible existing wireless transmitter framework of one kind provided by the embodiments of the present application;
Fig. 2 is a kind of DPD schematic diagram of possible ROF wireless transmitter provided by the embodiments of the present application;
Fig. 3 is the DPD schematic diagram of the possible existing wireless transmitter of one kind provided by the embodiments of the present application;
Fig. 4 is a kind of architecture diagram of possible ROF wireless transmitter provided by the embodiments of the present application;
Fig. 5 is a kind of embodiment architecture diagram of possible feedback circuit unit provided by the embodiments of the present application;
Fig. 6 is the embodiment architecture diagram of alternatively possible feedback circuit unit provided by the embodiments of the present application;
Fig. 7 is a kind of architecture diagram of possible ROF wireless transmitter provided by the embodiments of the present application;
Fig. 8 is a kind of possible predistortion principle figure provided by the embodiments of the present application;
Fig. 9 is the architecture diagram of alternatively possible ROF wireless transmitter provided by the embodiments of the present application;
Figure 10 is the architecture diagram of alternatively possible ROF wireless transmitter provided by the embodiments of the present application;
Figure 11 is the embodiment flow chart of the possible method for eliminating non-linear distortion of one kind provided by the embodiments of the present application.
Specific embodiment
The embodiment of the present application provides a kind of feedback circuit unit, ROF wireless transmitter and the side for eliminating non-linear distortion Method, for realizing the linearisation of ROF wireless transmitter.
Below in conjunction with the attached drawing in the embodiment of the present application, technical solutions in the embodiments of the present application carries out clear, complete Site preparation description, it is clear that described embodiments are only a part of embodiments of the present application, instead of all the embodiments.It is based on Embodiment in the application, those skilled in the art's every other implementation obtained without making creative work Example, shall fall in the protection scope of this application.
It include uplink (link from antenna to base band) and downlink in traditional wireless transmitter framework Uplink in practical application, can also be known as receives link, downlink from the angle of base band by (link from base band to antenna) Link is known as emitting link, in specific the application without limitation.Remote Radio Unit in traditional wireless transmitter framework (remote radio unit, RRU) is converted to digital signal circuit comprising radio frequency analog signal circuit and analog signal, and Optical fiber used by the framework transmits digital signal, remote interconnection mode are as follows: uplink first first turns radio frequency analog signal Digital signal is turned to, then by ROSA and optical fiber, digital signal is transported to central server (central server, CS) In, signal is handled by CS;And for downlink, then it is to send digital signal in RRU by ROSA and optical fiber, Digital signal is converted into the radio frequency analog signal that RRU is handled again in RRU, during this, optical fiber just play it is long-range mutually Effect even.It must include digital signal processing unit in RRU however, this radio frequency sending set framework, and Digital Signal Processing Unit not only increases the circuit volume of RRU, also increases power consumption, is unfavorable for the trend of RRU miniaturization.Such case will be in future Especially prominent in 5G wireless communications application, the following 5G system uses M-MIMO scheme, and number of active lanes is more, the output work in single channel Rate will be greatly reduced, with the reduction of single channel output power, the power consumption of digital circuit in RRU proportion can substantially on It rises, is less useful for the miniaturization of RRU.
ROF wireless transmitter framework is by the way that analog signal is first converted into as a kind of novel radio transmitter architecture Optical signal, then remotely conveyed by optical fiber, to big destination after be converted into same analog signal from optical signal again, reach Directly transport the purpose of analog signal.Relative to traditional wireless transmitter framework, the advantage of ROF wireless transmitter framework is exactly Digital circuits section in legacy wireless communication system RRU is transferred to the end CS, such RRU kind no longer needs at complicated number Module is managed, the power consumption and volume of RRU is reduced, is advantageously implemented the miniaturization of RRU.
It should be noted that regardless of can all be wrapped in RRU in traditional radio transmission rack structure or ROF wireless transmitter PA containing power amplifier, for signal to be amplified to suitable power.PA is most important non-linear element, in order to allow signal to put Distortion is not generated during big it is necessary to carry out linearization process to PA, in current base station system, at the linearisation of PA It manages main using digital pre-distortion (DPD) scheme.Using the linearized solution of digital pre-distortion, main flow such as earlier figures 1 Shown, details are not described herein again.
For ease of understanding, referring to Fig. 3, being DPD working principle diagram.Before carrying out DPD processing, baseband signal passes through PA (302) non-linear due to PA when, it will lead to baseband signal distortion, output the signal of a distortion.The effect of DPD is exactly Before baseband signal is sent to PA output, in DPD processing unit, a place opposite with the characteristic of PA (302) is done to baseband signal Reason, such baseband signal is after DPD processing unit (301) and PA (302), and finally output obtains undistorted baseband signal, Maintain linear characteristic.
As shown in figure 4, be the architecture diagram of existing ROF wireless transmitter, relative to traditional wireless transmitter framework, on Downlink increases ROF and optical fiber, and uplink can be divided into uplink feedback link and uplink receiving link, wherein.Uplink Feedback link sends DPD processing unit (402) for the signal exported from ADC (408) and carries out DPD processing, uplink receiving link The signal exported from ADC (408) is sent directly to baseband signal (401), since ROF and optical fiber are non-linear element, therefore When system carries out DPD processing, need to consider simultaneously ROF and the introduced distortion of optical fiber.Existing ROF as shown in connection with fig. 2 without The DPD schematic diagram of line transmitter architecture, baseband signal pass through the ROF and optical fiber (202) of downlink before carrying out DPD processing With PA (203), then be coupled out a part of signal by uplink feedback link feed back to DPD processing unit (201), due to feedback link It also include ROF and optical fiber in the feedback circuit unit (204) of road, i.e. signal is passing through feedback circuit unit (204) Shi Yehui Cause to be distorted, when DPD processing unit (201) being caused to be received from the signal of feedback circuit unit (204), can not tell and connect The non-thread sexual element of the signal received is that downlink (uplink ROF and optical fiber, PA) introduces or uplink feedback link is introduced Non-thread sexual element, the genuine property of PA (203) and ROF and optical fiber (202) cannot be obtained by resulting in DPD processing unit (201), So that DPD processing unit fails correctly to carry out baseband signal according to the genuine property of PA (203) and ROF and optical fiber (202) Reverse process affects the linearisation effect of system.
In view of this, the embodiment of the present application provides a kind of feedback circuit unit, for realizing the line of ROF wireless transmitter Property, which is applied to ROF wireless transmitter, and is located on the feedback link of ROF wireless transmitter, wherein The feedback link is dedicated for transmission feedback signal.
Referring to Fig. 5, being a kind of structural schematic diagram of feedback circuit unit provided by the embodiments of the present application, wherein feedback Circuit unit (501) includes ADC (5011), digital processing element (5012) and the first non-linear unit (5013), and described first Non-linear unit (5013) includes ROSA and optical fiber, and, the input terminal of ADC (5011) and the transmitting link of ROF wireless transmitter (502) it is connected, the input terminal of digital processing element (5012) is connected with the output end of ADC (5011), the first non-linear unit (5013) input terminal is connected with the output end of digital processing element (5012), the output end of the first non-linear unit (5013) with The input terminal of DPD processing unit (503) in ROF wireless transmitter is connected, and the output end and hair of DPD processing unit (503) Link (502) are penetrated to be connected.Specifically, the signal for reflecting link output is known as distorted signal, coupler is from the distorted signal It is coupled out partial simulation feedback signal, and the analog feedback signal is analog signal, ADC (5011) receives analog feedback letter Number, and the analog feedback signal is subjected to digital-to-analogue conversion, that is, digital signal is converted analog signals into, digital feedback has been obtained Signal, and then the digital feedback signal is output to digital processing element (5012) by ADC (5011), digital processing element (5012) The digital feedback signal is handled, digital baseband signal is obtained, for computer equipment use, wherein in practical application The treatment process may include the following steps: set digital feedback signal as x (n);
Step 1 carries out odd even extraction to digital feedback signal x (n), obtains:
Step 2 carries out symbol adjustment, obtains I, Q two paths of signals:
Step 3, I, Q two paths of signals x "I(n)、x″Q(n) filtering wave by prolonging time, and two are carried out in filtering wave by prolonging time device respectively The frequency response of filter meets:
Wherein, ω is time domain variable n corresponding frequency variable in Fourier transformation in digital feedback signal x (n), with true Protect two paths of signals strict orthogonal;
Step 4, to I, Q two paths of signals x " after delayJ(n)、x″Q(n) it is demodulated, obtains digital baseband signal, for The equipment such as computer use.
The digital baseband signal that processing obtains is sent the first non-linear unit (5013) by digital processing element (5012), Wherein the first non-linear unit (5013) includes single fiber bi-directional receiving-transmitting secondary module (bi-directional optical Subassembly, BOSA) (50131) and optical fiber (50132), BOSA (50131), which is used to receive and emit by optical fiber light, to be believed Number, in remote interconnection, both ends include at least a BOSA (50131), and are connected by optical fiber (50132), a BOSA (50131) digital baseband signal is received, digital baseband signal is converted into optical signal from radiofrequency signal, to pass through optical fiber (50132) it is transferred to another BOSA (50131), then the digital baseband signal for having been converted into optical signal is reduced into radio frequency letter Number, for transmission to DPD processing unit (503).It should be noted that in practical application, input terminal and digital processing element (5012) connected BOSA, may be replaced by light emitting secondary module (transmitting optical subassembly, TOSA), TOSA is used to digital baseband signal being converted to optical signal, output end and DPD processing unit (503) phase from radiofrequency signal BOSA even could alternatively be light-receiving secondary module (receiver optical subassembly, ROSA), and ROSA is used for will The digital baseband signal for having been converted into optical signal is reduced into radiofrequency signal, for transmission to DPD processing unit (503).Due to number Signal transmits generated distortion by optical fiber, transmits generated distortion by optical fiber relative to analog signal and is much smaller, Meet the requirement of system linearization.
In practical application, since the dynamic range of ADC (5011) is limited, so that the signal for inputing to ADC (5011) passes through Accurate digital signal cannot be obtained after sampling, therefore on the basis of Fig. 5, as shown in fig. 6, the feedback circuit unit (501) is also It may include down-converter unit (5014), the output end of the down-converter unit (5014) is connected with the input terminal of ADC (5011), institute The input terminal for stating down-converter unit (5014) is connected with reflection link (502).It should be noted that reflection link (502) includes Second non-linear unit (5021) and PA (5022), input terminal and reflection link (502) phase of the down-converter unit (5014) It is even specific can include: the input terminal of the down-converter unit is connected or described with the output end of the second non-linear unit (5021) The input terminal of down-converter unit is connected with the output end of PA (5022) or the input terminal of the down-converter unit and PA (5022) Output end is connected, and is also connected with the output end of the second non-linear unit (5021), and specific the embodiment of the present application is without limitation.Institute Down-converter unit (5014) is stated for reducing the carrier frequency for the analog feedback signal being coupled out from reflection link (502), with drop The carrier frequency sizes needed to system, improve the accuracy of the digital signal obtained after sampling.If it is defeated to reflect link (502) When the carrier frequency of analog feedback signal out meets the carrier frequency sizes of system needs, down-converter unit (5014) is then not required to It wants, therefore the component is selectable unit (SU).
It is understood that if when feedback circuit unit (501) does not include down-converter unit (5014), ADC's (5011) Input terminal is connected with reflection link (502), input terminal and reflection link (502) with the down-converter unit (5014) above-mentioned It is connected similar, specific details are not described herein again.
Since digital signal transmits generated distortion very little by optical fiber, it can satisfy the linear requirements of system, simultaneously It is output to from reflection link and is converted to this section components of digital signal, linear original part can be used, therefore can be by the embodiment of the present application The feedback circuit unit of offer integrally regards a linear unit as, and feedback signal will not cause additional when passing through feedback circuit unit Distortion, it is really characteristic that DPD processing unit, which can be obtained by reflection link output output signal, realizes ROF and wirelessly sends out Penetrate the linearisation of machine.
Fig. 7 is a kind of ROF wireless transmission provided on the basis of the embodiment of the present application feedback circuit unit shown in Fig. 5 The architecture diagram of machine, the ROF wireless transmitter include feedback circuit unit (701), transmitting link on feedback link (702), DPD processing unit (703) and receives link (704), wherein the transmitting link (702) includes PA (7022), second Non-linear unit (7021) and DAC (7023), second non-linear unit (7021) include ROF (70211) and optical fiber (70212), and the input terminal of DAC (7023) is connected with DPD processing unit (703), the input of the second non-linear unit (7021) End is connected with the output end of DAC (7023), and the input terminal of PA (7022) is connected with the output end of the second non-linear unit (7021), PA (7022) launches signal by antenna;Reflection link (702) is used to receive the initial base band letter handled without DPD Number, the initial baseband signal becomes distorted signal after second non-linear unit (7021), specifically, DAC (7023) initial baseband signal is received, and the initial baseband signal is converted into simulation letter from digital signal by digital-to-analogue conversion Number, analog baseband signal is obtained, and be output to the second non-linear unit (7021), i.e., in remote interconnection, analog baseband signal It is transferred to the ROF (70211) of the other end by optical fiber (70212) by the ROF (70211) of one end, and then is output to PA (7022), Since the second non-linear unit (7021) and PA (7022) are non-linear components, signal when non-linear components by that can generate Distortion, therefore analog baseband signal becomes distorted signal after non-linear components, and is output to feedback link.It is understood that It is that analog baseband signal becomes distorted signal after non-linear components, and is output to feedback link, it may include Analog Baseband letter Number become distorted signal after the second non-linear unit (7021) and is output to feedback link or analog baseband signal passes through Become distorted signal after second non-linear unit (7021) and PA (7022) and is output to feedback link or analog baseband signal It is just output to feedback link after the second non-linear unit (7021), and is output to feedback link again after PA (7022) Road, then timesharing is transported to DPD processing unit (703) again via feedback link, therefore analog baseband signal introduces the source tool of distortion Body the application is without limitation.
Optionally, emitting can also include upconverting unit, the input terminal and DAC of the upconverting unit in link (702) (7023) output end is connected, and the output end of the upconverting unit is connected with the input terminal of the second non-linear unit (7021), and The upconverting unit is used for the carrier frequency of Linear Amplifer analog baseband signal, to reach the carrier frequency sizes of system needs. If the carrier frequency of analog baseband signal meets the carrier frequency sizes of system needs, upconverting unit is not needed, therefore should Component is selectable unit (SU).
Feedback link, for being coupled out analog feedback signal from the distorted signal that the transmitting link exports, and by institute It states analog feedback signal and is handled to obtain digital baseband signal to export to the DPD processing unit, wherein feedback link packet Include feedback circuit unit (701), and component in feedback circuit unit (701), connection relationship and effect please refer to Fig. 5 or Feedback circuit unit shown in fig. 6, specific details are not described herein again;
The DPD processing unit (703), for receiving the digital baseband signal of the feedback link output, and according to institute It states digital baseband signal and carries out linear pre-distortion to from the signal of Baseband Receiver, obtain pre-distorted signals, and will be described pre- Distorted signal is output to the transmitting link (702);Emit link (702) and receives the pre- mistake from DPD processing unit (703) True signal, and being handled the distorted signal for distortion free signal according to the pre-distorted signals, then by the distortion free signal Emitted by antenna, for ease of understanding, referring to FIG. 8, be a kind of possible predistortion principle figure provided by the present application, if Curve (a) is by DPD processing unit (703) treated characteristics of signals, and curve (b) is by PA (7022) treated letter Number characteristic, the opposite in phase of the two, compound third order beat (composite triple beat, CTB) is equal in magnitude, mutually offsets Undistorted characteristics of signals i.e. curve (c) is obtained after disappearing.Wherein, pre-distorted signals can be pre-distortion parameters, emit link (702) according to handling from the pre-distortion parameters that DPD processing unit (703) receives distorted signal, in the mistake of transmission The reason of generating distorted signal is offset in journey, obtains distortion free signal, alternatively, pre-distorted signals can also be handled directly for DPD The signal that unit (703) will be obtained according to pre-distortion parameters after initial base band signal process, and then after emitting link (702) It is reduced to the initial baseband signal, specifically herein without limitation.
Receives link (704) includes third non-linear unit (7041) and DAC (7042), wherein third non-linear unit It (7041) include ROF (70411) and optical fiber (70412), and, the input terminal and transmitting link of third non-linear unit (7041) (702) it is connected, the input terminal of DAC (7042) is connected with the output end of third non-linear unit (7041), the output of DAC (7042) End is connected with Base Band Unit, i.e., third non-linear unit (7041) receives the reception signal that transmitting link (702) is coupled out, then passes It is defeated to DAC (7042) and to be converted into digital signal, it is sent in Base Band Unit and is handled.
It optionally, can also include down-converter unit, the input terminal of the down-converter unit and transmitting in receives link (704) Link (702) is connected, and the output end of the down-converter unit is connected with the input terminal of third non-linear unit (7041), and the lower change Frequency unit is for reducing the carrier frequency for receiving signal, to reach the carrier frequency sizes of system needs.If receiving the load of signal When wave frequency rate meets the carrier frequency sizes of system needs, down-converter unit is not needed then, therefore the component is selectable unit (SU).
Optionally, in practical application, other than single pass scene, i.e., only one emits link and a reception chain Road, there is also the scenes of multichannel, as shown in figure 9, there are multiple transmitting links, including transmitting link 1 arrives transmitting link N, and Multiple receives links are corresponding with, including receives link 1 arrives receives link N, and emit link 1 and use same to transmitting link N Feedback link can be sent to DPD processing unit per the feedback signal that transmitting chain road uses all the way, wherein the feedback by time-sharing format Link includes Fig. 5 or feedback circuit unit shown in fig. 6.
Optionally, present invention also provides the scenes of a multiple channel groups, and as shown in Figure 10, transmitting link 11 arrives N1, Corresponding receives link 11 arrives N1, and emits link 11 and use feedback link 1 to N1 timesharing;Emit link 12 and arrives N2, it is corresponding to receive Link 12 arrives N2, and emits link 12 and use feedback link 2 to N2 timesharing;... transmitting link 1M to NM, corresponding receives link 1M to NM, and emit link 1M to NM timesharing and use feedback link M.It can be similar in each group of channel, N number of transmitting link A feedback link is shared, the feedback signal of the group is transported to DPD processing unit by feedback link, realizes the linear of system Change.
In the embodiment of the present application, on the basis of existing ROF wireless transmitter framework, increase linear feedback link, specially It is used for transmission feedback signal.A linear feedback link can be increased on single channel framework, it can also be on multichannel framework Increase by one or more feedback link, the radio frequency system framework of the following 5G, using M-MIMO mode, radio-frequency channel number is more, such as At this moment 64 channels or 128 channels etc. increase by one or more linear feedback channel, smaller on the increase of circuit area influence, It is more more superior than improving component linear arrangement in cost, complexity and realizability.
The embodiment of the present application also provides a kind of method for eliminating non-linear distortion, this method is applied to ROF wireless transmission The transmitting link of machine, please refers to Figure 11, for the schematic diagram of the method provided by the present application for eliminating non-linear distortion, comprising:
1101, the carrier frequency of analog feedback signal is reduced;
In ROF wireless transmitter, transmitting link receives the initial baseband signal handled without DPD, the transmitting link Similar to the transmitting link in embodiment shown in figure 7 above, specific details are not described herein again, and initial baseband signal is by transmitting link In non-linear components after, non-linear distortion can be generated, become distorted signal, coupler is coupled out part from the distorted signal Signal, that is, analog feedback signal, if the size of the carrier frequency of the analog feedback signal is big more than the carrier frequency that system needs It is small, then need to reduce the carrier frequency of the analog feedback signal, so that it meets the needs of system, it is to be understood that if should The size of the carrier frequency of analog feedback signal is the size of the carrier frequency for the signal that system needs, then does not need to reduce simulation The carrier frequency of feedback signal, therefore in practical application, which is optional step.
1102, analog feedback signal progress digital-to-analogue conversion is obtained into digital feedback signal;
Analog feedback signal is analog signal, after carrying out digital-to-analogue conversion, has obtained digital feedback signal.
1103, digital feedback signal is handled to obtain digital baseband signal;
If digital feedback signal is x (n);Treatment process can comprise the following steps that
Step 1 carries out odd even extraction to digital feedback signal x (n), obtains:
Step 2 carries out symbol adjustment, obtains I, Q two paths of signals:
Step 3, I, Q two paths of signals x "I(n)、x″Q(n) filtering wave by prolonging time, and two are carried out in filtering wave by prolonging time device respectively The frequency response of filter meets:
Wherein, ω is time domain variable n corresponding frequency variable in Fourier transformation in digital feedback signal x (n), with true Protect two paths of signals strict orthogonal;
Step 4, to I, Q two paths of signals x " after delayJ(n)、x″Q(n) it is demodulated, obtains digital baseband signal, for The equipment such as computer use.
It 1104, is optical signal to be transmitted on optical fiber by digital baseband transmission system;
Digital baseband signal is converted to optical signal from radiofrequency signal by the BOSA of one end, to be transferred to separately by optical fiber The BOSA of one end, then radiofrequency signal is converted back by optical signal, to carry out DPD processing.
1105, pre-distorted signals are calculated according to digital baseband signal;
In practical application, look-up table (Look-Up Table, LUT) method can be used, i.e., by pre- mistake computed in advance True compensating parameter is stored in a table, then calculates the amount of the address in table according to the initial baseband signal of input, thus Compensating parameter is found, pre-distortion is carried out to signal, specifically can include:
Corresponding pre-distortion compensated is extracted in the upper LUT table once updated according to the different amplitudes of digital baseband signal Parameter;Digital baseband signal is handled according to the following formula to obtain pre-distorted signals:
Wherein, the pre-distorted signals after pre-distortion that z (n) the expression n moment exports, x (n) indicate that the n moment is defeated The initial baseband signal entered, n indicate digital baseband signal input time, l indicate pre-distorted signals the memory moment, a, b, c, D indicates that pre-distortion parameters, L indicate memory depth, k representative polynomial order, and K indicates that maximum polynomial order, * indicate signal Conjugation, | x (n) | indicate that the signal amplitude of digital baseband signal, x* (n) indicate the conjugated signal of digital baseband signal.
1106, pre-distorted signals are sent to transmitting link.
The pre-distorted signals are sent to the transmitting link, so that the transmitting link is believed according to the predistortion Number nonlinear compensation is carried out to the initial baseband signal.
In the embodiment of the present application, the linearization process of system is realized by the method for the elimination non-linear distortion.
It is apparent to those skilled in the art that for convenience and simplicity of description, the system of foregoing description, The specific work process of device and unit, can refer to corresponding processes in the foregoing method embodiment, and details are not described herein.
In several embodiments provided herein, it should be understood that disclosed system, device and method can be with It realizes by another way.For example, the apparatus embodiments described above are merely exemplary, for example, the unit It divides, only a kind of logical function partition, there may be another division manner in actual implementation, such as multiple units or components It can be combined or can be integrated into another system, or some features can be ignored or not executed.Another point, it is shown or The mutual coupling, direct-coupling or communication connection discussed can be through some interfaces, the indirect coupling of device or unit It closes or communicates to connect, can be electrical property, mechanical or other forms.
The unit as illustrated by the separation member may or may not be physically separated, aobvious as unit The component shown may or may not be physical unit, it can and it is in one place, or may be distributed over multiple In network unit.It can select some or all of unit therein according to the actual needs to realize the mesh of this embodiment scheme 's.
It, can also be in addition, each functional unit in each embodiment of the application can integrate in one processing unit It is that each unit physically exists alone, can also be integrated in one unit with two or more units.Above-mentioned integrated list Member both can take the form of hardware realization, can also realize in the form of software functional units.
If the integrated unit is realized in the form of SFU software functional unit and sells or use as independent product When, it can store in a computer readable storage medium.Based on this understanding, the technical solution of the application is substantially The all or part of the part that contributes to existing technology or the technical solution can be in the form of software products in other words It embodies, which is stored in a storage medium, including some instructions are used so that a computer Equipment (can be personal computer, server or the network equipment etc.) executes the complete of each embodiment the method for the application Portion or part steps.And storage medium above-mentioned include: USB flash disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), magnetic or disk etc. are various can store program The medium of code.
The above, above embodiments are only to illustrate the technical solution of the application, rather than its limitations;Although referring to before Embodiment is stated the application is described in detail, those skilled in the art should understand that: it still can be to preceding Technical solution documented by each embodiment is stated to modify or equivalent replacement of some of the technical features;And these It modifies or replaces, the spirit and scope of each embodiment technical solution of the application that it does not separate the essence of the corresponding technical solution.

Claims (10)

1. a kind of feedback circuit unit is applied on ROF wireless transmitter, it is wireless that the feedback circuit unit is located at the ROF On the feedback link of transmitter, the feedback circuit unit includes: digital analog converter ADC, digital processing element and first Non-linear unit, first non-linear unit includes optical fiber;
The input terminal of the ADC is connected with the transmitting link of the ROF wireless transmitter, the input terminal of the digital processing element It is connected with the output end of the ADC, the output end phase of the input terminal and the digital processing element of first non-linear unit Even, the output end of first non-linear unit is connected with the input terminal of digital predistorter DPD processing unit, at the DPD Reason unit is contained in the ROF wireless transmitter;
The ADC, for receiving from the analog feedback signal that is coupled out of transmitting link, and by the analog feedback signal into Line number mould is converted to digital feedback signal, to be output to the digital processing element;
The digital processing element for receiving the digital feedback signal of the ADC output, and the digital feedback is believed Number processing be digital baseband signal for computer equipment use, and export to first nonlinear block;
First nonlinear block for receiving the digital baseband signal of the digital processing element output, and is transferred to institute State DPD processing unit.
2. feedback circuit unit according to claim 1, which is characterized in that the feedback circuit unit further includes down coversion Unit, the output end of the down-converter unit are connected with the input terminal of the ADC, the input terminal of the down-converter unit with it is described The transmitting link of ROF wireless transmitter is connected;
The down-converter unit, for reducing the carrier frequency of the analog feedback signal.
3. feedback circuit unit according to claim 1, which is characterized in that the transmitting link of the ROF wireless transmitter It further include power amplifier PA and the second non-linear unit, second non-linear unit includes light carrier radio communication ROF and light Fibre, the input terminal of the PA are connected with the output end of second non-linear unit;
The input terminal of the ADC is connected with the transmitting link of the ROF wireless transmitter
The input terminal of the ADC is connected with the output end of the PA;Or,
The input terminal of the ADC is connected with the output end of second non-linear unit;Or,
The input terminal of the ADC is connected with the output end of the PA, and the input terminal of the ADC and second non-linear unit Output end be connected.
4. feedback circuit unit according to any one of claim 1 to 3, which is characterized in that first nonlinear model Block further includes single fiber bi-directional receiving-transmitting secondary module BOSA, and the BOSA is used to complete the conversion of radiofrequency signal and optical signal, so that institute Digital baseband signal is stated to transmit on the optical fiber.
5. a kind of ROF wireless transmitter, including feedback link, digital predistorter DPD processing unit and transmitting link, the hair Penetrating link includes power amplifier PA and the second non-linear unit, and second non-linear unit includes light carrier radio communication ROF And optical fiber, the input terminal of the PA are connected with the output end of second non-linear unit, which is characterized in that the feedback link Including feedback circuit unit such as of any of claims 1-2, the input terminal and the DPD of the transmitting link are handled The output end of unit is connected, and the input terminal of the DPD processing unit is connected with the output end of the feedback link;
The transmitting link, for receiving initial baseband signal, the initial baseband signal passes through second non-linear unit After become distorted signal;
The feedback link, for being coupled out analog feedback signal from the distorted signal that the transmitting link exports, and by institute Analog feedback signal is stated to be handled to obtain digital baseband signal to export to the DPD processing unit;
The DPD processing unit, for receiving the digital baseband signal of the feedback link output, and according to the digital baseband Signal carries out linear pre-distortion to the signal received from base band, obtains pre-distorted signals, and the pre-distorted signals are defeated The transmitting link is arrived out;
The transmitting link is also used to receive the pre-distorted signals from the DPD processing unit, and is believed according to the predistortion Number the distorted signal is handled as distortion free signal, and the distortion free signal is emitted by antenna.
6. ROF wireless transmitter according to claim 5, which is characterized in that the transmitting link includes that simulation numeral turns Parallel operation DAC, the second non-linear unit and power amplifier PA, second non-linear unit include light carrier radio communication ROF and Optical fiber;
The input terminal of the DAC is connected with the output end of the DPD, the input terminal and the DAC of second non-linear unit Output end be connected, the input terminal of the PA is connected with the output end of second non-linear unit;
The DAC, the digital signal for exporting the DPD processing unit carry out digital-to-analogue conversion and obtain analog signal, and will The analog signal output is to second non-linear unit;
Second non-linear unit, for receiving the analog signal of DAC output, and by the analog signal transmission To the PA;
The PA is emitted after the analog signal amplification for exporting second non-linear unit by antenna.
7. ROF wireless transmitter according to claim 6, which is characterized in that the transmitting link further includes up-conversion list Member, the output end of the upconverting unit are connected with the input terminal of the DAC, the input terminal of the upconverting unit and described the The input terminal of two non-linear units is connected;
The upconverting unit, the carrier frequency for digital signal described in Linear Amplifer.
8. ROF wireless transmitter according to any one of claims 5 to 7, the ROF wireless transmitter includes at least one A transmitting link, at least one described transmitting link are corresponding with a feedback link.
9. a kind of method for eliminating non-linear distortion, the method are applied to the transmitting link of ROF wireless transmitter, feature exists In the transmitting link receives initial baseband signal, and the transmission by the first nonlinear block of the transmitting link is lost True signal is coupled out analog feedback signal from the distorted signal characterized by comprising
The analog feedback signal received progress digital-to-analogue conversion is obtained into digital feedback signal;
It is handled the digital feedback signal to obtain digital baseband signal;
It is optical signal to be transmitted on optical fiber by the digital baseband transmission system;
Pre-distorted signals are calculated according to the digital baseband signal, the pre-distorted signals are sent to the transmitting chain Road, so that the transmitting link carries out power compensation to the initial baseband signal according to the pre-distorted signals.
10. according to the method described in claim 9, it is characterized in that, described carry out digital-to-analogue for the analog feedback signal received It is converted to before digital feedback signal, the method also includes:
Reduce the carrier frequency of the analog feedback signal.
CN201710759323.2A 2017-08-29 2017-08-29 Feedback circuit unit, ROF wireless transmitter and method for eliminating nonlinear distortion Active CN109428610B (en)

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