CN116405352A - System for improving power amplification efficiency of distributed antenna and calibration method thereof - Google Patents
System for improving power amplification efficiency of distributed antenna and calibration method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of phased array communication, and particularly relates to a system for improving the power amplification efficiency of a distributed antenna, which comprises a baseband signal coding module, a digital predistortion module, a DAC module, an up-conversion module, a phase array antenna unit, a matrix switch box, a down-conversion module, an ADC module, a data acquisition and processing unit and a far-field standard gain antenna; the baseband signal coding module, the digital predistortion module, the DAC module, the up-conversion module, the phase array antenna unit, the matrix switch box, the down-conversion module and the ADC module are sequentially connected, and the phase array antenna unit, the ADC module and the digital predistortion module are all connected with the data acquisition and processing unit and are also connected with the far-field standard gain antenna. According to the invention, based on the design of the digital predistortion module and the cooperation of the digital predistortion module and other modules, the effects of stronger antenna gain and better ACPR (advanced power supply) of the integrated effect can be realized by compensating the distortion on the common path and reducing the mutual interference among all branches through DPD (digital pre-distortion).
Description
Technical Field
The invention belongs to the technical field of phased array communication, and particularly relates to a system for improving power amplification efficiency of a distributed antenna and a calibration method thereof.
Background
5G and upcoming 6G communications (space-to-earth converged communications) will use a higher carrier frequency wireless communication system. High directivity antennas and analog beamforming with limited digital signal processing capabilities are being used in high directivity communication systems. To achieve the high rate communication requirements, very high communication bandwidths or high spectrum utilization are required. In the sub6GHz frequency band, 256QAM and higher modulation modes are applied, while in the millimeter wave frequency band 5G, the modulation modes only reach 64QAM, and in the traditional satellite communication application scene, the modulation modes of Ku and Ka frequency bands only reach 32QAM. Currently, in the field of Ku, ka, mmW communication, higher communication requirements for debug mode are already in the planning.
High modulation schemes and orthogonal frequency division multiplexing communication schemes require higher linearity for phased array transmitters to achieve low vector amplitude Errors (EVM). In contrast, the adjacent channel power ratio is widened and loosened within the criterion requirements of 5G communication. Factors affecting the linearity of the transmit chain are mainly: 1) Distortion of the beamformer of the common link portion; 2) Distortion of each distributed branch; 3) The mutual interference between the branches is distorted.
Therefore, how to solve the above-mentioned problems is important.
Disclosure of Invention
In order to achieve the above objective, the present invention is directed to provide a system for improving the power amplification efficiency of a distributed antenna, which compensates for distortion on a common path by DPD and reduces mutual interference between branches to achieve the effects of stronger antenna gain and better ACPR in the integrated effect.
In order to achieve the above object, the present invention has the following technical scheme.
The system for improving the power amplification efficiency of the distributed antenna is characterized by comprising a baseband signal coding module, a digital predistortion module, a DAC module, an up-conversion module, a phase array antenna unit, a matrix switch box, a down-conversion module, an ADC module, a data acquisition and processing unit and a far-field standard gain antenna;
the baseband signal coding module, the digital predistortion module, the DAC module, the up-conversion module, the phase array antenna unit, the matrix switch box, the down-conversion module and the ADC module are sequentially connected, the phase array antenna unit, the ADC module and the digital predistortion module are all connected with the data acquisition and processing unit, and the phase array antenna unit is also connected with the far-field standard gain antenna.
According to the invention, based on the design of the digital predistortion module and the cooperation of the digital predistortion module and other modules, the effects of stronger antenna gain and better ACPR (advanced power supply) of the integrated effect can be realized by compensating the distortion on the common path and reducing the mutual interference among all branches through DPD (digital pre-distortion).
Further, the phased array antenna unit includes 1: an N power division network and a plurality of antenna units; the antenna unit comprises a phase regulator, an adjustable gain amplifier (comprising an attenuator and a fixed gain amplifier), a PA (power amplifier), an antenna array element and a feed point near the antenna array element; the 1: the N power division network, the phase regulator, the adjustable gain amplifier, the PA and the antenna array element are connected in sequence.
Further, the feed point is a coupling feedback test point reserved near the antenna array element.
Further, the baseband signal coding module is used for generating baseband signals and performing coding mapping processing to generate code streams with different modulation modes; baseband signals such as pseudo-random sequence codes, etc.
The digital predistortion module carries out digital predistortion processing on code streams of different modulation modes, compensates dynamic nonlinear distortion and outputs the dynamic nonlinear distortion to the DAC module;
the DAC module converts the code stream after the digital predistortion treatment into a baseband analog signal;
the up-conversion module up-converts the baseband analog signals to a radio frequency band required by the phased array antenna unit; the up-conversion module is comprised of, but not limited to, a mixer/modulator, a phase locked loop, a gain module, and the like.
1: the N power division network receives the radio frequency signal output by the up-conversion module according to the following ratio of 1: the ratio of N is output to the phase regulator on average; the phase regulator carries out phase regulation processing on the radio frequency signal and outputs the radio frequency signal to the adjustable gain amplifier; the adjustable gain amplifier receives the radio frequency signal output by the phase regulator, carries out gain adjustment and outputs the radio frequency signal to the PA; the PA receives the radio frequency signal of the gain-adjustable amplifier, amplifies the power of the radio frequency signal and outputs the amplified radio frequency signal to the antenna array element; the antenna array element receives radio frequency signals output by the PA and radiates the radio frequency signals into space;
the matrix switch box is used for switching, connecting any one path, a plurality of paths or all-connected feed points near the antenna array elements of the multi-path antenna unit.
The down converter module down converts the tested radio frequency data output by the matrix switch box to zero frequency or an intermediate frequency band; the down-conversion template is composed of a phase-locked loop including but not limited to a mixer/demodulator, a local oscillator LO generation, a low noise gain module, etc.
The ADC is used for converting the analog data of zero frequency or intermediate frequency into digital signals and sending the digital signals to the data acquisition and processing unit;
and the data acquisition and processing unit is responsible for feed point and/or far-field OTA test data acquisition and comprehensive processing, compares and analyzes the acquisition difference, optimizes the fitting coefficient and issues a predistortion control command.
Further, the data acquisition and processing unit comprises a data acquisition unit and a data processing unit. The data acquisition unit and the like can use devices such as a frequency spectrograph, a comprehensive tester, an oscilloscope, an upper computer and the like. The data processing unit comprises a data analysis tool, an algorithm, control software, control hardware and the like.
Further, the digital predistortion module is composed of a lookup table or a polynomial.
Further, the complex gain predistortion method adopts two one-dimensional tables, namely an amplitude compensation table and a phase compensation table, to look up the predistortion of the tables; alternatively, a two-dimensional table indexed by orthogonal components is employed.
As a part of digital signal processing, the predistorter is realized by using an FPGA or a special IC, and is positioned in a baseband part, and the predistorter is realized by using a complex gain lookup table. The complex gain predistortion method uses two one-dimensional tables, an amplitude compensation table and a phase compensation table, to implement the look-up table predistortion, and sometimes uses two-dimensional tables indexed by orthogonal components. The predistorter has fewer table entries, and I component and Q component are stored in a lookup table to be respectively compensated, so that complex gain is formed. The final correction signal is obtained by complex multiplication from the input signal and the compensation of the entries. The principle diagram of the gain method is shown in the figure, and the predistorter is in the baseband processing of the FPGA.
The quadrature modulation input signal is divided into an I path and a Q path for predistortion correction, the predistortion signal is converted into a predistortion analog signal by digital-to-analog conversion, the predistortion analog signal is amplified by power amplification after up-conversion, and the predistortion analog signal is transmitted through an array antenna; the power signal output by a small amount of radio frequency is converted into a high intermediate frequency signal through coupling, the high intermediate frequency signal is converted into a low intermediate frequency signal, a digital signal is obtained after mixing, the digital signal becomes a feedback signal, and an error signal is obtained according to the processing of the feedback signal and an original input signal, so that the predistortion table entry coefficient can be updated according to the error signal and a corresponding self-adaptive algorithm. The initial coefficients in the predistorter table entry are all 1+j0, and when the signal enters for the first time, the signal does not carry out corresponding compensation. The corresponding table coefficients of the predistorter are mainly calculated according to the power amplifier output of the signal, and the table is divided into amplitude compensation and phase compensation.
A calibration method for improving the power amplification efficiency of a distributed antenna comprises the following steps:
s101, configuring a DPD predistortion calibration system of a phased array transmitter according to an initial frequency point f0 and standard signal power p0, configuring a predistortion module according to a default initial value, configuring each module of a phased array antenna unit according to an initial typical value, and normally configuring each module to start normally;
s102, the matrix switch box is sequentially connected with feedback points of FB1, FB2 … … FB (n-1) and FBn to provide corresponding feedback paths;
s103, a feedback data acquisition unit (the unit is a part of a data acquisition and processing unit) sequentially acquires data of a feed point according to the FB1, FB2 … … FB (n-1) and FBn paths of the feed point, and records corresponding amplitude and phase information to form a multidimensional data table;
s104, the data processing unit records according to the feedback data acquisition unit, and performs the respective marking of the phase offset of each radio frequency branch as
Meanwhile, recording gain values of all radio frequency branches, and recording the gain values as G1, G2..
S105, obtaining a phase shift mean value by using a least square method
Obtaining the phase shift and the phase shift average value of each branch>
Is a difference in (2); and debugging the phase control register of the phase shifter (i.e. phase adjuster) of each branch so that the offset is equal to or approximates the phase offset mean +.>
Similarly, the least square method is used to obtain the gain average value G of each branch rms The method comprises the steps of carrying out a first treatment on the surface of the Obtaining the gain of each branch and the gain average value G rms Is a difference in (2); and debugging the attenuation control register of the attenuator of each branch so that the gain is equal to or approximates to the gain average G rms The method comprises the steps of carrying out a first treatment on the surface of the Storing the phase compensation value, the gain compensation value and the corresponding frequency of each branch into a memory of the phased array transmitting system; the gain compensation value is obtained by a least square method. The gain of each branch is G1 and … … Gn, and the gain difference of each branch is G1-Grms and … … Gn-Grms; phase offset is similar to this.
S106, respectively debugging the PA_bias value of each branch, sequentially switching on the feedback points of FB1, FB2 … … FB (n-1) and FBn by the matrix switch box, and recording P by the data acquisition and processing unit pa vsValue pa_bias Curve and ACPR values for each branch; the values of Pa and Value and ACPR can be obtained according to a conventional test method in the industry.
S107 ACPR with the set ACPR value ref For reference, in>ACPR ref Is arranged in each branch P of (1) pa_max Minimum of (3)The value is denoted as P as normalized value pa_normalized The method comprises the steps of carrying out a first treatment on the surface of the Each branch is equal to or approximates P by setting the value of PA_bias pa_normalized Storing the compensation value and the corresponding frequency and temperature of each PA_bias into a system memory; thus, the consistency check of each branch is completed; methods for obtaining such data are known in the art.
S108, switching the switch matrix box to a far-field standard gain antenna path, and sending a command of beam pointing by the phased array transmitting system according to the relative position of the phased array antenna unit and the far-field standard gain antenna (the relative position meets far-field test distance and is in the adjustable range of the beam pointing of the phased array antenna unit), so that a transmitting beam signal is received by the far-field standard gain antenna;
s109, performing predistortion compensation strategy estimation; the OTA data acquisition unit acquires data of far-field test, the data processing unit performs related operation according to the acquired data and the transmitted data, and phase distortion information and amplitude distortion information are extracted;
s110, the data processing unit performs debugging of phase compensation parameters in a certain range and amplitude distortion compensation in a certain range according to the phase distortion and amplitude distortion information; observing the changes of phase distortion and amplitude distortion in real time, determining phase distortion compensation parameters and amplitude distortion compensation parameters according to the data with minimum amplitude phase distortion, and storing and recording according to the corresponding relation with frequency and temperature;
s111, repeating the steps S101-S110 according to the step interval frequency to perform calibration operation;
s112, repeating the steps S101-S110 according to the temperature of the step interval in the working temperature range to perform calibration operation;
and S113, fitting the multiphase relation of amplitude and phase distortion compensation parameters, frequency and temperature, and selecting an adaptive distortion compensation strategy of the digital predistortion module.
According to the invention, on the basis of the existing electric scanning phased array transmitting architecture, the cost is obviously reduced by adding the antenna feed point of PCB coupling near the antenna array element, and the coupling relation is fixed. The antenna feed point replaces the near field probe test, so that the test cost is reduced, and the test is more accurate;
the DPD mode of the near field and the far field is more suitable for the practical application effect of the system, and the test result is more practical;
the DPD technology enables power generation to be higher, reduces unit power energy consumption and improves power amplification efficiency. Meanwhile, the signal quality IMD3 is improved, all ACPR are improved, a higher modulation mode can be supported, the frequency spectrum utilization rate is provided, and the system capacity is further optimized.
Drawings
Fig. 1 is a system architecture block diagram of the DPD predistortion calibration system of the present invention.
Fig. 2 is a block diagram of gain method DPD predistortion calibration.
Fig. 3 is a predistortion compensation strategy estimation block diagram.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
A system for improving the power amplification efficiency of a distributed antenna (namely a DPD predistortion calibration system) comprises a phased array antenna unit, a baseband signal coding module, a digital predistortion module, a DAC, an up-converter module, a phased array antenna unit standard antenna, a far-field standard gain antenna, a matrix switch box and a data acquisition and processing unit. The phased array antenna unit consists of 1: the power amplifier comprises an N power division network, a phase regulator, an adjustable gain amplifier, a PA (power amplifier) and an antenna array element. The adjustable gain amplifier includes an adjustable attenuator (attenuator) and a fixed gain amplifier. Wherein, 1: the N power division network receives the radio frequency signal output by the up-conversion module according to the following ratio of 1: the ratio of N is output to the phase regulator on average; the phase regulator carries out phase regulation processing on the radio frequency signal and outputs the radio frequency signal to the adjustable gain amplifier; the adjustable gain amplifier receives the radio frequency signal output by the phase regulator, carries out gain adjustment and outputs the radio frequency signal to the PA; the PA receives the radio frequency signal of the gain-adjustable amplifier, amplifies the power of the radio frequency signal and outputs the amplified radio frequency signal to the antenna array element; antenna array element receptionThe radio frequency signal output by the PA radiates into space. 1: the N power division network, the phase regulator, the adjustable gain amplifier, the PA and the antenna array element are sequentially connected. The phased array antenna unit is configured to perform a power processing on a signal output by the up-conversion module (as shown in a 1:n power division network of fig. 1), and send the processed signal to an antenna array element (as shown in ATENNA of fig. 1) through a phase adjuster (as shown in PS of fig. 1), an adjustable gain amplifier (as shown in VGA of fig. 1), and a PA (as shown in PA of fig. 1), where the phase adjuster, the adjustable gain amplifier, and the PA may be integrated into a multifunctional chip, or may be a separate device or a chip set with multiple functions combined or split. Wherein a coupling feedback test point, a feed point (shown as FB in fig. 1), is reserved near each antenna element. By adding the antenna feed points of the PCB coupling near the distributed array elements, the cost is obviously reduced, and the coupling relation is fixed. And a feedback path is selected by the matrix switch box, and the consistency of each radio frequency branch is checked by adjusting the values of the phase shifter and the attenuator of the phased array chip and the bias of the amplifier. And then combining the acquisition of far-field test feedback data of the standard gain horn antenna, and fitting and calculating the polynomial coefficients of the digital predistortion through a plurality of groups of training data. And carrying out digital predistortion treatment on the code streams with different modulation modes through the digital predistortion module to compensate dynamic nonlinear distortion. The placement distance d of the far-field standard gain antenna needs to meet the far-field test requirement: d > =2d 2 λ, wherein D is the horizontal or vertical length of the antenna element plane; lambda is the frequency at which the array element radiates into space.
Fig. 1 is a block diagram of a system for improving the power amplifier efficiency of a distributed antenna. The main function is that the input baseband signal is processed and modulated by a digital pre-coding matrix to obtain a symbol stream, the symbol stream is input to a digital pre-distorter to carry out digital pre-distortion treatment to compensate dynamic nonlinear distortion, the digital signal after the digital pre-distortion treatment is converted into an analog signal, the analog signal enters a phased array unit after going to a radio frequency band by an up-converter, consistency adjustment and feedback detection of amplitude, phase and the like are completed in the phased array unit, and finally the signal is respectively transmitted by each array element.
Specifically, the system for improving the power amplification efficiency of the distributed antenna only has a single-path digital baseband processing unit public circuit, and the structural block diagram is shown in fig. 1, and is mainly composed of 10 modules:
baseband signal coding module: the main function is to process the modulated symbol stream with a precoding matrix on the transmitted signal at the transmitting end of the downlink using clutter suppression interferometry csi (cluttersuppressioninterferometry) and input to a digital predistorter.
Digital predistorter: the system is composed of a lookup table or a polynomial, and has the main function of reprocessing the signals processed by the precoding matrix to compensate dynamic nonlinear distortion of the power amplifier and outputting the dynamic nonlinear distortion to the DAC module.
DAC module: the digital-to-analog converter DAC is used for converting the output signal of the digital predistorter into analog signal to form the baseband analog signal, which is output to the up-converter.
An up-converter: the device consists of a PLL and a mixer for generating local oscillation signals, and has the main functions of mixing and moving the analog signals output by d/a conversion to a radio frequency band and outputting the signals to a phased array unit.
Phased array antenna unit: the phase shifter, the power divider, the attenuator, the amplifier, the antenna array element, the feed point near the antenna and the like are used for adjusting the phase of the mixed output signal through the phase shifter, adjusting the amplitude through the attenuator, adjusting the radio frequency signal through the bias of the amplifier, achieving the purpose of adjusting the phase of the antenna transmitting signal, mainly radiating out the energy through the antenna array element, feeding back a small part of the energy through the feed point to the data acquisition circuit through the matrix switch, and calibrating the consistency problem of each branch.
Far field standard gain antenna: the method is used for testing the fixed gain antenna in the OTA far field and feeding back the effect of the far-field comprehensive wave beam. The distance from the antenna to the array surface meets the requirement of far-field test, is strongly related to the test frequency band, and is generally calculated and determined by selecting the low frequency band of the product.
Matrix switch box: the device can switch and connect any one, several or all-connected antenna feed points.
A down converter module: the tested radio frequency data output by the electronic switch is down-converted to a zero or intermediate frequency band including, but not limited to, a mixer/modulator, a phase locked loop, a low noise gain module, etc.
ADC: and converting the analog data with zero frequency or intermediate frequency into digital signals and sending the digital signals to a data acquisition and processing unit. The sampling rate is considered 6 times and above the bandwidth of the transmitted signal.
Data acquisition and processing unit: and the method is responsible for data acquisition and comprehensive processing such as feed point (near field) and far field OTA tests, compares and analyzes acquisition difference, optimizes fitting coefficients and issues predistortion control commands. The data acquisition and the like can use devices such as a frequency spectrograph, a comprehensive tester, an oscilloscope, an upper computer and the like. The data processing unit comprises a data analysis tool, an algorithm, control software, control hardware and the like. The near field feed point is used for verifying the consistency problem of the N radio frequency branches and carrying out compensation adjustment. The OTA far field test is used for eliminating the influence of mutual interference of public routes and radio frequency branches.
The final output signal can compensate dynamic nonlinear distortion and static nonlinear distortion of the power amplifier through theoretical analysis.
The embodiment also provides a calibration method for improving the power amplification efficiency of the distributed antenna, which comprises the following steps:
s101, configuring a DPD predistortion calibration system (shown in figure 1) of a phased array transmitter according to an initial frequency point f0 and standard signal power p0, configuring a predistortion module according to a default initial value, configuring each module of a phased array antenna unit according to an initial typical value (PA enable on, PA bias, phase shifter and attenuator are configured according to default values), and normally configuring each module to start normally.
S102, the matrix switch box is sequentially connected with feedback points of FB1, FB2 … … FB (n-1) and FBn to provide corresponding feedback paths;
and S103, a feedback data acquisition unit (the unit is a part of a data acquisition and processing unit) sequentially acquires data of a feed point according to the FB1, FB2 … … FB (n-1) and FBn paths of the on feedback, and records corresponding amplitude and phase information to form a multidimensional data table.
S104, a data processing unit (the unit is a part of the data acquisition and processing unit) for recording the phase offset of each radio frequency branch according to the feedback data acquisition unit
Meanwhile, the gain value of each radio frequency branch is recorded and respectively marked as G1, G2 … … G (n-1) and G (n);
s105, obtaining a phase shift mean value by using a least square method
Obtaining the phase shift and the phase shift average value of each branch>
Is a difference in (c). And debugging the phase control registers of the phase shifters of the branches so that the offset is equal to or approximates the phase offset mean +.>
Similarly, the least square method is used to obtain the gain average value G of each branch rms The method comprises the steps of carrying out a first treatment on the surface of the Obtaining the gain of each branch and the gain average value G rms Is a difference in (c). And debugging the attenuation control register of the attenuator of each branch so that the gain is equal to or approximates to the gain average G rms The method comprises the steps of carrying out a first treatment on the surface of the The phase compensation values, gain compensation values, and corresponding frequencies for each leg are stored in a memory of the phased array transmit system.
S106, respectively debugging the PA_bias value of each branch, sequentially switching on the feedback points of FB1, FB2 … … FB (n-1) and FBn by the matrix switch box, and recording P by the data acquisition and processing unit pa vsValue pa_bias Curve and ACPR values for each leg.
S107 ACPR with the set ACPR value ref For reference, in>ACPR ref Is arranged in each branch P of (1) pa_max The minimum value of (2) is denoted as P as the normalized value pa_normalized . Each branch is set with PA_bThe ias value is equal to or approximates P pa_normalized The compensation value of each pa_bias and the corresponding frequency and temperature are stored in a system memory. And thus, the consistency check of each branch is completed.
S108, switching the switch matrix box to a far-field standard gain antenna path, and issuing a command of beam pointing by the phased array transmitting system according to the relative positions of the phased array antenna unit and the far-field standard gain antenna (the relative positions meet far-field test distances and are in the adjustable range of the beam pointing of the phased array antenna unit), so that a transmitting beam signal is received by the far-field standard gain antenna.
And S109, performing predistortion compensation strategy estimation, as shown in fig. 3. The OTA data acquisition unit acquires data of far-field test, and the data processing unit performs related operation according to the acquired data and the transmitted data to extract phase distortion information and amplitude distortion information.
And S110, the data processing unit performs debugging on the phase compensation parameter in a certain range and debugging on the amplitude distortion compensation in a certain range according to the phase distortion and the amplitude distortion information. And observing the changes of the phase distortion and the amplitude distortion in real time, determining phase distortion compensation parameters and amplitude distortion compensation parameters according to the data with the minimum amplitude phase distortion, and storing and recording according to the corresponding relation with frequency and temperature.
And S111, repeating the steps S101-S110 according to the step interval frequency to perform calibration operation.
And S112, repeating the steps S101-S110 according to the temperature of the step interval in the working temperature range to perform calibration operation.
And S113, fitting the multiphase relation of amplitude and phase distortion compensation parameters, frequency and temperature, and selecting an adaptive distortion compensation strategy of the digital predistortion module.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (8)
1. The system for improving the power amplification efficiency of the distributed antenna is characterized by comprising a baseband signal coding module, a digital predistortion module, a DAC module, an up-conversion module, a phase array antenna unit, a matrix switch box, a down-conversion module, an ADC module, a data acquisition and processing unit and a far-field standard gain antenna;
the baseband signal coding module, the digital predistortion module, the DAC module, the up-conversion module, the phase array antenna unit, the matrix switch box, the down-conversion module and the ADC module are sequentially connected, the phase array antenna unit, the ADC module and the digital predistortion module are all connected with the data acquisition and processing unit, and the phase array antenna unit is also connected with the far-field standard gain antenna.
2. The system for improving the power amplification efficiency of a distributed antenna as set forth in claim 1, wherein said phased array antenna unit comprises 1: an N power division network and a plurality of antenna units; the antenna unit comprises a phase regulator, an amplifier, an attenuator, an antenna array element and a feed point near the antenna array element; the 1: the N power division network, the phase regulator, the amplifier, the attenuator and the antenna array element are connected in sequence.
3. The system of claim 2, wherein the feed-back point is a coupling feedback test point reserved near an antenna element.
4. The system for improving the power amplification efficiency of a distributed antenna according to claim 2, wherein the baseband signal encoding module generates baseband signals and performs code mapping processing to generate code streams with different modulation modes;
the digital predistortion module carries out digital predistortion processing on code streams of different modulation modes, compensates dynamic nonlinear distortion and outputs the dynamic nonlinear distortion to the DAC module;
the DAC module converts the code stream after the digital predistortion treatment into a baseband analog signal;
the up-conversion module up-converts the baseband analog signals to a radio frequency band required by the phased array antenna unit;
1: the N power division network receives the radio frequency signal output by the up-conversion module according to the following ratio of 1: the ratio of N is output to the phase regulator on average; the phase regulator carries out phase regulation processing on the radio frequency signal and outputs the radio frequency signal to the amplifier; the amplifier receives the radio frequency signal output by the phase regulator, carries out gain adjustment and outputs the radio frequency signal to the attenuator; the attenuator receives the radio frequency signal of the amplifier, amplifies the power of the radio frequency signal and outputs the amplified radio frequency signal to the antenna array element; the antenna array element receives the radio frequency signal output by the attenuator and radiates the radio frequency signal into space;
the matrix switch box is used for switching and connecting any one, several or all the feed points near the antenna array elements of the multi-path antenna unit;
the down converter module down converts the tested radio frequency data output by the matrix switch box to zero frequency or an intermediate frequency band;
the ADC is used for converting the analog data of zero frequency or intermediate frequency into digital signals and sending the digital signals to the data acquisition and processing unit;
and the data acquisition and processing unit is responsible for feed point and/or far-field OTA test data acquisition and comprehensive processing, compares and analyzes the acquisition difference, optimizes the fitting coefficient and issues a predistortion control command.
5. The system for improving power amplifier efficiency of distributed antenna according to claim 4, wherein said data acquisition and processing unit comprises a data acquisition unit and a data processing unit.
6. A system for improving power amplifier efficiency of a distributed antenna according to claim 1, wherein the digital predistortion module is comprised of a look-up table or a polynomial.
7. The system for improving power amplifier efficiency of distributed antenna according to claim 6, wherein the complex gain predistortion method uses two one-dimensional tables, an amplitude compensation table and a phase compensation table, respectively, to look up the table predistortion; alternatively, a two-dimensional table indexed by orthogonal components is employed.
8. The method for calibrating the power amplification efficiency of the distributed antenna comprises a DPD predistortion calibration system, and is characterized by comprising the following steps:
s101, configuring a DPD predistortion calibration system according to an initial frequency point f0 and standard signal power p0, configuring a predistortion module according to a default initial value, configuring each module of a phased array antenna unit according to an initial typical value, and normally configuring and starting each module;
s102, the matrix switch box is sequentially connected with feedback points of FB1, FB2 … … FB (n-1) and FBn to provide corresponding feedback paths;
s103, a data acquisition unit sequentially acquires data of a feed point according to the feedback-on FB1, FB2 … … FB (n-1) and FBn paths, and records corresponding amplitude and phase information to form a multi-dimensional data table;
s104, the data processing unit records according to the feedback data acquisition unit, and performs the respective marking of the phase offset of each radio frequency branch as
Meanwhile, recording gain values of all radio frequency branches, and recording the gain values as G1, G2..
S105, obtaining a phase shift mean value by using a least square method
Obtaining the phase shift and the phase shift average value of each branch>
Is a difference in (2); and debugging the phase control register of the phase adjuster of each branch so that the offset is equal to or approximates the phase offset mean +.>
Similarly, the least square method is used to obtain the gain average value G of each branch rms The method comprises the steps of carrying out a first treatment on the surface of the Obtaining the gain of each branch and the gain average value G rms Is a difference in (2); and is combined withTuning the attenuation control registers of the attenuators of the branches so that the gain is equal to or approximates the gain average G rms The method comprises the steps of carrying out a first treatment on the surface of the Storing the phase compensation value, the gain compensation value and the corresponding frequency of each branch into a memory of the system;
s106, respectively debugging the PA_bias value of each branch, sequentially switching on the feedback points of FB1, FB2 … … FB (n-1) and FBn by the matrix switch box, and recording P by the data acquisition and processing unit pa vsValue pa_bias Curve and ACPR values for each branch;
s107 ACPR with the set ACPR value ref For reference, in>ACPR ref Is arranged in each branch P of (1) pa_max The minimum value of (2) is denoted as P as the normalized value pa_normalized The method comprises the steps of carrying out a first treatment on the surface of the Each branch is equal to or approximates P by setting the value of PA_bias pa_normalized Storing the compensation value and the corresponding frequency and temperature of each PA_bias into a system memory; thus, the consistency check of each branch is completed;
s108, switching the switch matrix box to a far-field standard gain antenna channel, and issuing a beam pointing command by the system according to the relative positions of the phased array antenna unit and the far-field standard gain antenna so that a transmitting beam signal is received by the far-field standard gain antenna;
s109, performing predistortion compensation strategy estimation; the data acquisition unit acquires data of far-field test, the data processing unit operates according to the acquired data and the transmitted data, and phase distortion information and amplitude distortion information are extracted;
s110, the data processing unit performs debugging of phase compensation parameters in a certain range and amplitude distortion compensation in a certain range according to the phase distortion and amplitude distortion information; observing the changes of phase distortion and amplitude distortion in real time, determining phase distortion compensation parameters and amplitude distortion compensation parameters according to the data with minimum amplitude phase distortion, and storing and recording according to the corresponding relation with frequency and temperature;
s111, repeating the steps S101-S110 according to the step interval frequency to perform calibration operation;
s112, repeating the steps S101-S110 according to the temperature of the step interval in the working temperature range to perform calibration operation;
and S113, fitting the multiphase relation of amplitude and phase distortion compensation parameters, frequency and temperature, and selecting an adaptive distortion compensation strategy of the digital predistortion module.
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