CN111193521B - Digital predistortion processing loop and method applied to civil aviation ground-air data link - Google Patents
Digital predistortion processing loop and method applied to civil aviation ground-air data link Download PDFInfo
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Abstract
The invention discloses a digital predistortion processing loop and a method applied to a civil aviation ground-air data link, wherein the digital predistortion processing loop comprises a digital predistortion module, an orthogonal modulator, a power amplifier, an attenuator and an orthogonal demodulator; the output end of the quadrature modulator of the digital predistortion loop is directly connected with the input end of the power amplifier, the output end of the power amplifier is connected with the attenuator, and the attenuator is directly connected with the quadrature demodulator. The invention simplifies the whole predistortion loop by adopting the joint estimator, solves the problems of complex circuit, high power consumption and the like of the traditional civil aviation ground-air data link digital predistortion method, and simultaneously does not need an additional observation loop; and the joint estimator is adopted to jointly estimate and compensate distortion problems such as amplitude imbalance, phase imbalance and direct current offset generated by the quadrature modulator and the quadrature demodulator, and the possibility of convergence to a local minimum value does not exist in the theory of a final estimation coefficient, so that the linear effect of the power amplifier is avoided from being unsatisfactory.
Description
Technical Field
The invention relates to the field of civil aviation communication, in particular to a digital predistortion processing loop and a digital predistortion processing method applied to a civil aviation ground-air data link.
Background
In order to relieve the pressure of the increasing air traffic flow on pipe manufacturing and make the application of new concepts and new technologies more standard in civil aviation air traffic management, civil aviation ground-air data links are proposed and increasingly popularized. The power amplifier linearization technology is a key technology in civil aviation ground-air data links.
The digital predistortion technology is often used for linearization of power amplifiers due to the characteristics of high stability, high precision, strong adaptive capacity, suitability for broadband communication and the like. The traditional civil aviation ground-air data link digital predistortion method usually adopts a secondary mixing structure, and the circuit structure is complex, the power consumption is high, and the miniaturization is not facilitated. The civil aviation ground-air data link digital predistortion method adopting the primary mixing structure reduces the power consumption, but needs an additional observation loop for compensating the distortion of the orthogonal modem, so the circuit structure is very complicated, and the miniaturization is not facilitated. In addition, the one-time mixing structure may cause the digital predistortion algorithm to converge to a local minimum value, which results in undesirable effects.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the traditional civil aviation ground-air data link digital predistortion method adopting a secondary mixing structure is complex in circuit structure and high in power consumption, and is not beneficial to miniaturization, while the civil aviation ground-air data link digital predistortion method adopting a primary mixing structure needs an additional observation loop for compensating the distortion of an orthogonal modem although the power consumption is reduced, so that the circuit structure is also very complex and is also not beneficial to miniaturization.
To solve the above technical problems.
The invention is realized by the following technical scheme:
the invention provides a digital predistortion processing loop applied to a civil aviation ground-air data link, which comprises a digital predistortion module, an orthogonal modulator, a power amplifier, an attenuator and an orthogonal demodulator; the digital predistortion circuit is characterized in that the output end of an orthogonal modulator of the digital predistortion circuit is directly connected with the input end of a power amplifier, the output end of the power amplifier is connected with an attenuator, and the attenuator is directly connected with the orthogonal modulator.
The digital predistortion module comprises:
the predistorter is used for carrying out predistortion processing on the input signal; the predistorter is also used for receiving the coefficient signals extracted by the coefficient extractor;
and the joint estimator is used for performing quick synchronous operation on the signal subjected to the predistortion processing and the feedback signal modulated by the orthogonal demodulator, estimating and compensating the distortion generated by the orthogonal demodulator, the power amplifier and the orthogonal demodulator on the feedback signal modulated by the orthogonal demodulator, and finally calculating the final estimation coefficient of the digital predistortion processing loop.
A coefficient extractor for extracting final estimation coefficients of the digital pre-distortion processing loop;
and the subtracter is used for comparing the error between the input signal after the predistortion processing and the operation output signal of the joint estimator.
The joint estimator comprises: a controller, a memory, and an arithmetic unit;
the memory comprises a subprogram which is executed by a controller control arithmetic unit and is used for carrying out quick synchronous operation on an input signal x (n) after the predistortion treatment and a feedback signal r (n) after the demodulation of an orthogonal demodulator, and the calculation formula is
Θ(k)＝R*(k)gX(-k)
In the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes the complex conjugation.
The memory comprises a computation subprogram which is executed by the controller control arithmetic unit and used for estimating and compensating the feedback signal after the demodulation of the orthogonal demodulator, and the estimation and compensation operation formulas of x (n) and r (n) are as follows:
in the formula:
c is a DC offset estimation value;
p(n)＝[ω(n),ω*(n),c]estimating a coefficient for the final estimation of the civil aviation ground-air data link digital predistortion method;
[Φ(s(n)),Φ*(s(n)),1]Polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator.
A further preferred technical solution is that, the memory includes a final estimation coefficient operation subprogram of the digital predistortion processing loop executed by the controller control arithmetic unit, and the final estimation coefficient p (n) is obtained by using a recursive least square algorithm and estimation and compensation operation formulas of x (n) and r (n) by the joint estimator, and by participating in multiple iterations with an error e (n).
The invention provides a digital predistortion processing loop applied to a civil aviation ground-air data link, wherein the output end of an orthogonal modulator is directly connected with the input end of a power amplifier, the output end of the power amplifier is connected with an attenuator, and the attenuator is directly connected with the orthogonal demodulator. Compared with an observation loop additionally arranged for compensating the distortion of the orthogonal modem in the traditional structure, the digital predistortion processing loop circuit provided by the invention has a simpler structure and is beneficial to miniaturization. The invention adopts a rapid synchronization method to realize the synchronization of an input signal x (n) after the predistortion processing and a feedback signal r (n) after the demodulation of a demodulator, adopts a joint estimator to realize the joint estimation of the distortion (comprising amplitude imbalance, phase imbalance, direct current offset and the like) generated by an orthogonal modulator and an orthogonal demodulator, and adopts the joint estimator to calculate the final estimation coefficient of a digital predistortion processing loop. The memory in the joint estimator contains three subprograms, firstly the controller controls the arithmetic unit to execute a fast synchronous operation subprogram for the input signal x (n) after the predistortion treatment and the feedback signal r (n) after the demodulation of the orthogonal demodulator, then the controller controls the arithmetic unit to execute an operation subprogram for estimating and compensating the feedback signal after the demodulation of the orthogonal demodulator, and finally the controller controls the arithmetic unit to execute a final estimation coefficient operation subprogram of the digital predistortion treatment loop. In the digital predistortion method used in the traditional civil aviation ground-air data link, whether the estimator used in the digital predistortion module in the digital predistortion loop adopting the primary mixing structure or the secondary mixing structure, the memory of the estimator also comprises the three subprograms; however, in the second sub-routine of the estimator of the digital predistortion loop with the traditional structure, only the distortion generated by devices except the quadrature modem in the loop can be estimated and compensated, and the distortion generated by the quadrature modem can be estimated and compensated only by adding other loops. The key point of the invention is that the whole digital predistortion loop is simplified by improving the subprogram in the combined estimator, and the whole circuit structure is simpler and is beneficial to miniaturization; in addition, because the traditional one-time mixing structure digital predistortion loop comprises two observation loops, a controller in the estimator needs to control the arithmetic unit to carry out operation of three subprograms on output signals of each loop, and thus the arithmetic unit executes six times of operation to ensure that the processing time and the power consumption are higher; the controller in the joint estimator only needs to calculate the feedback signal once by subprogram, namely three times of operation, so that the power consumption of the whole circuit is reduced.
The invention further preferably adopts the technical scheme that the invention provides a digital predistortion processing method applied to a civil aviation ground-air data link, and the method comprises the following implementation steps:
(1a) the predistorter carries out predistortion treatment on an input complex signal s (n) to obtain x (n), the orthogonal modulator modulates the x (n) and sends the modulated signal into a power amplifier, the power amplifier amplifies and outputs the modulated signal into y (n), the y (n) enters a feedback loop firstly, is attenuated by an attenuator and is demodulated by an orthogonal demodulator to obtain r (n); r (n) is input to the joint estimator;
(2a) the predistorter carries out predistortion treatment on an input complex signal s (n) to obtain x (n), and the x (n) is directly input into the joint estimator;
(3a) fast synchronization operation is carried out on x (n) and r (n) by a joint estimator, the joint estimator carries out estimation compensation on the distortion generated by the orthogonal modulator, the power amplifier and the orthogonal demodulator after the synchronization, and the output of the joint estimator is
Inputting the data into a subtracter;
(4a) by subtracter to x (n) and
making difference comparison to obtain error e (n), and inputting the error into the joint estimator;
(5a) e (n) back to the joint estimator, e (n) participates in the calculation of the final estimation coefficients p (n) by the joint estimator;
(6a) the coefficient extractor extracts coefficients p (n) from the joint estimator, and finally p (n) is input into the predistorter;
a further preferred technical solution is that, the digital predistortion processing method applied to civil aviation ground-air data link is characterized in that the attenuator attenuates the y (n) entering the feedback loop by G times, where G is the gain of the power amplifier;
further preferably, the digital predistortion method applied to civil aviation ground-air data link is characterized in that the fast synchronization operation of the joint estimator on x (n) and r (n) is as follows:
Θ(k)＝R*(k)gX(-k)
in the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes complex conjugation;
a further preferred technical solution is that, in the digital predistortion method applied to civil aviation ground-air data link, the estimation and compensation operations performed by the joint estimator on x (n) and r (n) are as follows:
in the formula:
c is a DC offset estimation value;
p(n)＝[ω(n),ω*(n),c]estimating a coefficient for the final estimation of the civil aviation ground-air data link digital predistortion method;
[Φ(s(n)),Φ*(s(n)),1]Polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator.
The memory of the digital predistortion module estimator in the digital predistortion loop with the traditional structure comprises the following three steps:
the method comprises the following steps: the feedback signal r (n) demodulated by the demodulator and the input signal x (n) pre-distorted by the pre-distortion processor are synchronously operated, and the formula used is as follows:
Θ(k)＝R*(k)gX(-k)
in the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes complex conjugation;
step two: estimating and compensating the input signal x (n) and the feedback signal r (n) after the synchronization in the step one;
the operation formula is as follows:
x(n)＝ξT(n)Φ(s(n))
wherein: ξ (n) is an estimation coefficient of the traditional digital predistortion;
the polynomial model of the power amplifier is shown, and K is the order; t denotes transposition.
Step three: the controller controls the operator to calculate a final estimation coefficient ξ (n).
For the civil aviation ground-air data link digital predistortion method with the traditional structure, an estimator can only compensate the distortion of a power amplifier, namely, an operation formula for estimating and compensating the synchronized input signal x (n) and the feedback signal r (n) is shown in the specification:
x(n)＝ξT(n)Φ(s(n))
The scheme performs estimation and compensation operations on x (n) and r (n):
in the expression [ phi (s (n)) ], phi*(s(n)),1]Polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator. The scheme realizes distortion (packet) generated by the orthogonal modulator and the orthogonal demodulator through the joint estimatorIncluding amplitude imbalance, phase imbalance, and dc offset, etc.).
The further preferable technical scheme is that the final estimation coefficient p (n) is obtained by using a recursive least square algorithm and estimation and compensation operation formulas of x (n) and r (n) by a joint estimator and participating in multiple iterations through an error e (n).
And in addition, x (n) needs to pass through an orthogonal modulator and a power amplifier, then is coupled by a directional coupler, is attenuated by G times, and is demodulated into r (n) by an orthogonal demodulator, and then reaches the joint estimator.
According to the formula x (n) ═ ω (n), ω*(n),c]T[Φ(s(n)),Φ*(s(n)),1]And obtaining the final p (n) through a plurality of iterations by using a recursive least square algorithm. Formula x (n) ═ ω (n), ω*(n),c]T[Φ(s(n)),Φ*(s(n)),1]The problems of amplitude imbalance, phase imbalance, direct current offset and the like caused by the quadrature modulator and the quadrature demodulator can be accurately estimated, and y (n) ═ Gs (n) can be simultaneously used, so that the linearization of the power amplifier is completed. Meanwhile, by using the formula (3) and the recursive least square method, theoretically, p (n) does not have a local minimum value, namely p (n) calculated by the method is necessarily an optimal solution.
The linearized output result of the whole power amplifier is y (n) ═ Gs (n).
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention provides a digital predistortion processing loop and a method applied to a civil aviation ground-air data link, which simplify the whole predistortion loop by adopting a joint estimator, solve the problems of complex circuit, high power consumption and the like of the traditional civil aviation ground-air data link digital predistortion method, and simultaneously do not need an additional observation loop;
2. the invention provides a digital predistortion processing circuit and a method applied to civil aviation ground-air data chains, which adopt a joint estimator and can jointly estimate and compensate the distortion problems such as amplitude imbalance, phase imbalance, direct current offset and the like generated by an orthogonal modulator and an orthogonal demodulator;
3. the invention provides a digital predistortion processing loop and a method applied to a civil aviation ground-air data link.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention.
In the drawings:
FIG. 1 is a schematic block diagram of a civil aviation ground-air data link digital predistortion method of the invention.
Reference numbers and corresponding part names in FIG. 1:
the method comprises the following steps of 1-a digital predistortion module, 2-an orthogonal modulator, 3-a power amplifier, 4-an attenuator, 5-an orthogonal demodulator, 6-a predistorter, 7-a coefficient extractor, 8-a joint estimator and 9-a subtracter.
Fig. 2 is a schematic block diagram of a civil aviation ground-air data link digital predistortion method of a conventional secondary mixing structure.
Reference numbers and corresponding part names in fig. 2:
10-a predistorter, 11-a subtracter, 12-an estimator, 13-a coefficient extractor, 14-a digital quadrature modulator, 15-a digital quadrature demodulator, 16-a first mixer, 17-a second mixer, 18-a power amplifier, 19-an attenuator and 20-a digital predistortion module.
Fig. 3 is a schematic block diagram of a civil aviation ground-air data link digital predistortion method of a conventional primary mixing structure.
21-predistorter, 22-estimator, 23-coefficient extractor, 24-orthogonal modulator, 25-orthogonal demodulator, 26-multiplexer, 27-power amplifier, 28-attenuator, and 29-digital predistortion module.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
The digital predistortion technology is often used for linearization of power amplifiers due to the characteristics of high stability, high precision, strong adaptive capacity, suitability for broadband communication and the like. However, the traditional digital predistortion method for civil aviation ground-air data link usually adopts a secondary frequency mixing structure, as shown in fig. 2, a first frequency mixer 16 and a second frequency mixer 17 are respectively arranged at two sides of a power amplifier in a digital predistortion loop, a digital quadrature modulator 14 and a digital quadrature demodulator 15 are used for the quadrature modulator and the quadrature demodulator, the digital quadrature modulator and the digital quadrature demodulator form a digital local oscillator, and the first frequency mixer 16 and the second frequency mixer 17 form an analog local oscillator, so that the circuit structure is complex, the power consumption is high, and the miniaturization is not facilitated.
If the civil aviation ground-air data link digital predistortion method of the primary mixing structure is adopted, as shown in fig. 3, in order to compensate the distortion of the orthogonal modem, a multiplexer 26 is arranged at the output end of an attenuator 28 on the power amplifier input end and the feedback branch in the digital predistortion loop to form two observation loops, the observation loop 1 is output by the attenuator 28 and then reaches the multiplexer 26, the observation loop 2 directly reaches the multiplexer by the orthogonal modulator 24, and the two observation loops compensate the distortion of the orthogonal modulator 24 and the orthogonal demodulator 25, but the circuit structure is very complex, the operation process is also complex due to the complex circuit structure, and the miniaturization is not facilitated. In addition, the primary mixing structure may cause the digital predistortion algorithm to converge to a local minimum, which results in undesirable effects.
The method can solve the problems of complex circuit, high power consumption and the like of the traditional civil aviation ground-air data chain digital predistortion method, does not need an additional observation loop, can jointly compensate the distortion problems of amplitude imbalance, phase imbalance, direct current offset and the like generated by the quadrature modulator and the quadrature demodulator, and theoretically has no possibility of converging to a local minimum value.
The invention provides a digital predistortion processing loop applied to a civil aviation ground-air data link, which comprises a digital predistortion module 1, an orthogonal modulator 2, a power amplifier 3, an attenuator 4 and an orthogonal demodulator 5, wherein the digital predistortion processing loop comprises a digital predistortion module, a digital quadrature modulator, a digital quadrature demodulator and a digital quadrature demodulator; the output end of the quadrature modulator 2 of the digital predistortion loop is directly connected with the input end of the power amplifier 3, the output end of the power amplifier 3 is connected with the attenuator 4, and the attenuator 4 is directly connected with the quadrature demodulator 5.
The digital predistortion module 1 comprises:
a predistorter 6 for performing predistortion processing on an input signal; the predistorter 6 is also used for receiving the coefficient signals extracted by the coefficient extractor 7;
and the joint estimator 8 is used for performing quick synchronous operation on the signal subjected to the predistortion processing and the feedback signal modulated by the orthogonal demodulator 5, estimating and compensating the distortion generated by the orthogonal modulator 2, the power amplifier 3 and the orthogonal demodulator 5 on the feedback signal modulated by the orthogonal demodulator 5, and finally calculating the final estimation coefficient of the digital predistortion processing loop.
A coefficient extractor 7 for extracting final estimation coefficients of the digital predistortion processing loop;
and a subtracter 9 for comparing the input signal after the pre-distortion processing with the error between the output signals calculated by the joint estimator 8.
The digital predistortion processing loop applied to civil aviation ground-air data link, the joint estimator 8 includes: a controller, a memory, and an arithmetic unit;
the memory comprises a subprogram which is executed by a controller control arithmetic unit and is used for carrying out quick synchronous operation on an input signal x (n) after the predistortion treatment and a feedback signal r (n) after the demodulation of an orthogonal demodulator 5, and the calculation formula is
Θ(k)＝R*(k)gX(-k)
In the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes the complex conjugation.
The memory comprises a computation subprogram which is executed by a controller control arithmetic unit and is used for estimating and compensating the feedback signal modulated by the orthogonal demodulator 5, and the estimation and compensation operation formulas of x (n) and r (n) are as follows:
in the formula:
c is a DC offset estimation value;
p(n)＝[ω(n),ω*(n),c]estimating a coefficient for the final estimation of the civil aviation ground-air data link digital predistortion method;
[Φ(s(n)),Φ*(s(n)),1]Polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator.
The memory comprises a final estimation coefficient operation subprogram of the digital predistortion processing loop executed by a controller control arithmetic unit, and a final estimation coefficient p (n) is obtained by a joint estimator by utilizing a recursive least square algorithm and estimation and compensation operation formulas of x (n) and r (n) through an error e (n) participating in multiple iterations.
The scheme also provides a digital predistortion processing method applied to civil aviation ground-air data chains, and the method comprises the following implementation steps:
(1a) the predistorter 6 carries out predistortion treatment on an input complex signal s (n) to obtain x (n), the orthogonal modulator 2 modulates the x (n) and then sends the modulated signal into the power amplifier 3, the power amplifier 3 amplifies and outputs the modulated signal as y (n), the y (n) firstly enters the feedback loop, is attenuated by the attenuator 4 and then is demodulated by the orthogonal demodulator 5 to obtain r (n); r (n) is input to the joint estimator 8;
(2a) the predistorter 6 performs predistortion processing on an input complex signal s (n) to obtain x (n), and the x (n) is directly input into the joint estimator 8;
(3a) fast synchronization of x (n) and r (n) is performed by the joint estimator, the joint estimator 8 performs estimation compensation on the synchronized r (n) with respect to the distortion generated by the orthogonal modulator 2 and the orthogonal demodulator 5, and the output of the joint estimator 8 is
Input the subtracter 9;
(4a) x (n) and x are subtracted by a subtractor 9
Difference comparison is carried out to obtain an error e (n), and the error is input into the joint estimator 8;
(5a) e (n) back to the joint estimator 8, e (n) participates in the calculation of the final estimation coefficients p (n) by the joint estimator 8;
(6a) the coefficient extractor 7 extracts coefficients p (n) from the joint estimator, and finally p (n) is input into the predistorter;
the attenuator 4 attenuates y (n) entering a feedback loop by G times, wherein G is the gain of the power amplifier;
according to the estimation and compensation operation formulas performed on x (n) and r (n):
and obtaining the final p (n) through a plurality of iterations by using a recursive least square algorithm.
Formula (II)
The problems of amplitude imbalance, phase imbalance, direct current offset and the like caused by the quadrature modulator and the quadrature demodulator can be accurately estimated, an observation loop is not required to be additionally arranged, and y (n) ═ Gs (n) can be simultaneously used, so that the linearization of the power amplifier is completed. Meanwhile, by using the recursive least square method, theoretically, p (n) does not have local minimum, namely p (n) calculated by the method is necessarily the optimal solution.
The method solves the problems of complex circuit, high power consumption and the like of the traditional civil aviation ground-air data chain digital predistortion method, simultaneously needs no additional observation loop, can jointly compensate the distortion problems of amplitude imbalance, phase imbalance, direct current offset and the like generated by the quadrature modulator and the quadrature demodulator, and theoretically has no possibility of converging to a local minimum value.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A digital predistortion processing loop applied to civil aviation ground-air data link comprises a digital predistortion module (1), an orthogonal modulator (2), a power amplifier (3), an attenuator (4) and an orthogonal demodulator (5); the digital predistortion loop is characterized in that the output end of an orthogonal modulator (2) of the digital predistortion loop is directly connected with the input end of a power amplifier (3), the output end of the power amplifier (3) is connected with an attenuator (4), and the attenuator (4) is directly connected with an orthogonal demodulator (5);
the digital predistortion module (1) comprises:
a predistorter (6) for performing predistortion processing on the input signal; the predistorter (6) is also used for receiving the coefficient signals extracted by the coefficient extractor (7);
a joint estimator (8) which is used for carrying out fast synchronous operation on the signal after the predistortion treatment and the feedback signal after the demodulation of the orthogonal demodulator (5), then carrying out estimation compensation on the feedback signal after the demodulation of the orthogonal demodulator (5) about the distortion generated by the orthogonal modulator (2), the power amplifier (3) and the orthogonal demodulator (5), and finally calculating the final estimation coefficient of the digital predistortion treatment loop;
a coefficient extractor (7) for extracting final estimation coefficients of the digital pre-distortion processing loop;
a subtracter (9) for comparing the error between the input signal after the pre-distortion processing and the operation output signal of the joint estimator;
the joint estimator (8) comprises: a controller, a memory, and an arithmetic unit;
the memory comprises a subprogram which is executed by a controller control arithmetic unit and is used for carrying out quick synchronous operation on an input signal x (n) after the predistortion treatment and a feedback signal r (n) after the demodulation of an orthogonal demodulator (5), and the calculation formula is
Θ(k)＝R*(k)gX(-k)
In the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes complex conjugation;
the memory comprises a computation subprogram which is executed by a controller control arithmetic unit and used for estimating and compensating the feedback signal after being modulated by the orthogonal demodulator (5), and the estimation and compensation computation formulas of x (n) and r (n) are as follows:
in the formula:
c is a DC offset estimation value;
p(n)＝[ω(n),ω*(n),c]estimating a coefficient for the final estimation of the civil aviation ground-air data link digital predistortion method;
[Φ(s(n)),Φ*(s(n)),1]polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator.
2. The digital predistortion processing loop for civil aviation ground-air data link as claimed in claim 1, wherein said memory comprises a final estimation coefficient operation subroutine of the digital predistortion processing loop executed by the controller control arithmetic unit; the final estimation coefficient p (n) is obtained by using a recursive least square algorithm and an estimation and compensation operation formula of x (n) and r (n) through an error e (n) participating in multiple iterations by a joint estimator.
3. A digital predistortion processing method applied to civil aviation ground-air data chains is characterized by comprising the following implementation steps:
(1a) the predistorter carries out predistortion treatment on an input complex signal s (n) to obtain x (n), the orthogonal modulator modulates the x (n) and sends the modulated signal into a power amplifier, the power amplifier amplifies and outputs the modulated signal into y (n), the y (n) enters a feedback loop firstly, is attenuated by an attenuator and is demodulated by an orthogonal demodulator to obtain r (n); r (n) is input to the joint estimator;
(2a) the predistorter carries out predistortion treatment on an input complex signal s (n) to obtain x (n), and the x (n) is directly input into the joint estimator;
(3a) fast synchronization operation is carried out on x (n) and r (n) by a joint estimator, the joint estimator carries out estimation compensation on distortion and power amplifier distortion generated by the orthogonal modulator and the orthogonal demodulator after the synchronization, and the output of the joint estimator is
Inputting the data into a subtracter;
(4a) by subtracter to x (n) and
making difference comparison to obtain error e (n), and inputting the error into the joint estimator;
(5a) e (n) back to the joint estimator, e (n) participates in the calculation of the final estimation coefficients p (n) by the joint estimator;
(6a) the coefficient extractor extracts coefficients p (n) from the joint estimator, and finally p (n) is input into the predistorter;
the estimation and compensation operation of the joint estimator on x (n) and r (n) is as follows:
in the formula:
c is a DC offset estimation value;
p(n)＝[ω(n),ω*(n),c]estimating a coefficient for the final estimation of the civil aviation ground-air data link digital predistortion method;
[Φ(s(n)),Φ*(s(n)),1]polynomial model representing the whole of power amplifier, quadrature modulator, quadrature demodulator.
4. The method of claim 3, wherein the attenuator attenuates the y (n) entering the feedback loop by a factor of G, where G is the power amplifier gain.
5. The method of claim 3, wherein the fast synchronization operation of the joint estimator on x (n) and r (n) is:
Θ(k)＝R*(k)gX(-k)
in the formula:
Θ (k) is the correlation value; the maximum value of theta (k) is the synchronization time;
r (k) represents the Fourier transform of r (n);
x (k) represents the Fourier transform of x (n);
denotes the complex conjugation.
6. The method as claimed in claim 3, wherein the final estimation coefficient p (n) is obtained by using a recursive least square algorithm and an estimation and compensation operation formula of x (n) and r (n) through an error e (n) to participate in multiple iterations by the joint estimator.
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| CN107770111A (en) * | 2017-12-08 | 2018-03-06 | 航天恒星科技有限公司 | Pulse-shaping combination digital pre-distortion suppresses OFDM peak-to-average ratio System and method for |
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