Short-wave transmitter for inhibiting intermodulation and harmonic distortion based on digital pre-distortion method

Abstract

The utility model belongs to the technical field of wireless communication, and particularly discloses a short wave transmitter for inhibiting intermodulation and harmonic distortion based on a digital pre-distortion method, which comprises a digital pre-distortion algorithm module, an orthogonal up-conversion module, a digital-to-analog converter, a power amplifier, an analog-to-digital converter and an orthogonal down-conversion module, a first input end of the digital pre-distortion algorithm module is connected with a baseband signal, a second input end is connected with an output end of the orthogonal down-conversion module, an output end of the digital pre-distortion algorithm module is connected with an input end of the orthogonal up-conversion module, an output end of the orthogonal up-conversion module is connected with an input end of the DAC, an output end of the DAC is connected with an input end of the PA, an output end of the PA is connected with an input end of the ADC, and an output end of the ADC is connected with an output end of the ADC. And the output end of the ADC is connected with the input end of the orthogonal down-conversion module. The short wave transmitter provided by the utility model not only realizes suppression of intermodulation distortion and harmonic distortion, but also improves the linearity of the power amplifier.

Description

Technical Field

[0001] The utility model belongs to the technical field of wireless communication, relates to the application of an adaptive digital predistortion technology, and specifically is a shortwave transmitter which suppresses intermodulation and harmonic distortion based on a digital predistortion method. Background Art

[0002] In the field of wireless communications, shortwave is widely used in various communication fields due to its unique skywave propagation mode, lack of expensive infrastructure, and strong survivability. Shortwave transmitters are key components of communication systems, and the power amplifier is a core component. To achieve optimal output performance, power amplifiers are typically operated near saturation. However, this can lead to nonlinear distortion in the output signal, primarily intermodulation distortion and harmonic distortion, which significantly affects the signal quality and communication performance of shortwave transmitters.

[0003] To correct nonlinear distortion in power amplifiers (PAs), numerous linearization techniques have been applied in practical engineering. Digital predistortion (DPD) is a preferred solution for this purpose. However, traditional DPD primarily suppresses intermodulation distortion (IMD) within PAs. Harmonic distortion suppression relies on bulky analog filter banks. However, this approach suffers from bulkiness, high cost, and high power consumption in practical applications, hindering the miniaturization and low power requirements of shortwave transmitter systems. Furthermore, analog filter banks have limited performance, making it difficult to completely eliminate harmonic distortion, which impacts signal quality and communication performance.

[0004] Therefore, using analog filter banks to suppress harmonic distortion is clearly not conducive to achieving miniaturization and low power consumption in transmitters. In recent years, DPD technology has been applied to harmonic distortion suppression. Existing harmonic cancellation methods fall into two main categories: one uses baseband signals for harmonic cancellation, where the DPD algorithm module uses complex signals before upconversion; the other uses digital RF signals for harmonic cancellation, where the DPD algorithm uses real signals after upconversion. Harmonic cancellation using baseband signals offers several advantages over digital RF signals, including higher signal processing accuracy, greater algorithm design flexibility, easier system integration and debugging, and more efficient resource utilization. Therefore, using baseband signals to achieve harmonic elimination is becoming a trend. For example, Chinese patent application CN114826298A, entitled "A shortwave transmitter harmonic suppression device and method," uses baseband signals to achieve harmonic elimination. However, in the preprocessing module, this solution requires the received digital harmonic signal to be digitally separated and extracted, aligned with the input baseband signal, and spectrum shifted. Each harmonic must undergo this complex process, which increases the system's computational complexity and processing time, and also increases the requirements for hardware equipment, which to a certain extent affects the system's efficiency and stability.

[0005] In view of this, this utility model is proposed. Utility Model Content

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a shortwave transmitter based on a digital predistortion method to suppress intermodulation and harmonic distortion. It is mainly used to solve the problems of bulky size, high cost, high power consumption and limited performance caused by the traditional technology of suppressing harmonic distortion through analog filter groups, and the complex process of using baseband signals to achieve harmonic elimination in the prior art, which affects the efficiency and stability of the communication system.

[0007] The purpose of this utility model is to solve the problem through the following technical solutions:

[0008] The utility model provides a shortwave transmitter based on a digital predistortion method to suppress intermodulation and harmonic distortion, comprising a digital predistortion algorithm module, an orthogonal up-conversion module, a digital-to-analog converter, a power amplifier, an analog-to-digital converter, and an orthogonal down-conversion module;

[0009] The first input end of the digital predistortion algorithm module is connected to the baseband signal, and the second input end is connected to the output end of the orthogonal down-conversion module, and is used to solve the predistortion signal that can suppress the intermodulation distortion and harmonic distortion of the power amplifier;

[0010] The input end of the orthogonal up-conversion module is connected to the output end of the digital pre-distortion algorithm module, and is used to shift the frequency of the pre-distortion signal to the carrier frequency position and output a digital signal;

[0011] The input end of the digital-to-analog converter is connected to the output end of the orthogonal up-conversion module, and is used to convert the digital signal output by the orthogonal up-conversion module into an analog signal;

[0012] The input end of the power amplifier is connected to the output end of the digital-to-analog converter, and is used to power amplify the analog signal output by the digital-to-analog converter;

[0013] The input end of the analog-to-digital converter is connected to the output end of the power amplifier, and is used to convert the analog signal output by the digital-to-analog converter and after power amplification by the power amplifier into a digital signal;

[0014] The input end of the orthogonal down-conversion module is connected to the output end of the analog-to-digital converter, and is used to down-convert the digital signal output by the analog-to-digital converter to a low frequency.

[0015] Furthermore, the digital predistortion algorithm module includes an intermodulation suppression submodule, a harmonic suppression submodule and an adder;

[0016] The first input end of the intermodulation suppression submodule is connected to the baseband signal, and the second input end is connected to the output end of the orthogonal down-conversion module, and is used to solve the predistortion signal that can suppress the intermodulation distortion of the power amplifier;

[0017] The first input end of the harmonic suppression submodule is connected to the baseband signal, and the second input end is connected to the output end of the orthogonal down-conversion module, and is used to solve the predistortion signal that can suppress the harmonic distortion of the power amplifier;

[0018] The first input end of the adder is connected to the output end of the intermodulation suppression submodule, and the second input end is connected to the output end of the harmonic suppression submodule. The output end of the adder is connected to the input end of the orthogonal up-conversion module, and is used to add the solved predistortion signal for suppressing the intermodulation distortion and harmonic distortion of the power amplifier, so as to suppress the intermodulation distortion and harmonic distortion at the same time.

[0019] Furthermore, the intermodulation suppression submodule includes an intermodulation suppression digital predistortion model and an intermodulation suppression digital predistortion model coefficient solving unit;

[0020] The first input end of the intermodulation suppression digital predistortion model is connected to the baseband signal, the second input end is connected to the output end of the intermodulation suppression digital predistortion model coefficient solving unit, and the first output end of the intermodulation suppression digital predistortion model is connected to the first input end of the adder, for solving the predistortion signal capable of suppressing the intermodulation distortion of the power amplifier;

[0021] The first input end of the intermodulation suppression digital predistortion model coefficient solving unit is connected to the second output end of the intermodulation suppression digital predistortion model, and the second input end is connected to the output end of the orthogonal down-conversion, and is used to solve the model coefficients that can suppress the intermodulation distortion of the power amplifier and transmit them to the intermodulation suppression digital predistortion model.

[0022] Furthermore, the intermodulation suppression digital predistortion model and the intermodulation suppression digital predistortion model coefficient solving unit adopt a polynomial model or a neural network model to characterize intermodulation distortion.

[0023] Furthermore, the intermodulation suppression digital predistortion model coefficient solving unit adopts a least square method to solve the model coefficients.

[0024] Furthermore, the harmonic suppression submodule includes a harmonic suppression digital predistortion model, a harmonic suppression digital predistortion model coefficient solving unit and a multiplier;

[0025] The first input end of the harmonic suppression digital predistortion model is connected to the baseband signal, the second input end is connected to the harmonic suppression digital predistortion model coefficient solving unit, and the output end of the harmonic suppression digital predistortion model is connected to the second input end of the adder, for solving the predistortion signal capable of suppressing the harmonic distortion of the power amplifier;

[0026] The first input end of the harmonic suppression digital predistortion model coefficient solving unit is connected to the baseband signal, and the second input end is connected to the output end of the multiplier, and is used to solve the model coefficients capable of suppressing the harmonic distortion of the power amplifier and transmit them to the harmonic suppression digital predistortion model;

[0027] The first input terminal of the multiplier is a negative number (-λ), and the second input terminal is connected to the output terminal of the orthogonal down-conversion, and is used to invert and amplify the output signal of the orthogonal down-conversion by λ times.

[0028] Furthermore, the harmonic suppression digital predistortion model and the harmonic suppression digital predistortion model coefficient solving unit both use the following formula (1) to characterize the inverted harmonic distortion:

[0029]

[0030] Among them, H is the harmonic number represented, M is the memory depth of the harmonic, K is the nonlinear order of the harmonic, f c Indicates the carrier frequency, a h,m,k is the model coefficient.

[0031] Furthermore, the harmonic suppression digital predistortion model coefficient solving unit is used to adjust the hth harmonic model coefficient a h,m,k The positive and negative values can be adjusted to suit different harmonic characteristics.

[0032] Furthermore, the harmonic suppression digital predistortion model coefficient solving unit adopts a least square method to solve the model coefficients, and the harmonic suppression digital predistortion model coefficient solving unit has a function of saving the model coefficients so as to update the model coefficients during iteration.

[0033] Furthermore, the baseband signal used by the digital predistortion algorithm module and the output signal of the orthogonal down-conversion module need to undergo preprocessing operations, and the preprocessing operations include amplitude alignment, delay alignment and frequency offset compensation.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The shortwave transmitter provided by the present invention is mainly composed of a predistortion algorithm module, an orthogonal up-conversion module, a digital-to-analog converter, a power amplifier, an analog-to-digital converter, and an orthogonal down-conversion module. Compared with the existing technology, the shortwave transmitter has at least the following advantages:

[0036] First, it effectively addresses a series of issues raised by traditional analog filter banks for harmonic distortion suppression, such as bulk, high cost, high power consumption, and limited performance. This significantly contributes to the miniaturization and low power consumption goals of shortwave transmitter systems. Traditional analog filter banks not only occupy a large amount of space, increasing the size and weight of equipment and hindering miniaturization, but also have high production costs, increasing overall equipment production costs and subsequent maintenance and replacement costs. Furthermore, their high power consumption contradicts current low-power demands.

[0037] Second, the existing baseband signal harmonic elimination method has been optimized. Only one down-conversion and delay alignment operation is required, making the implementation process relatively easy. This avoids the complex operations required for each harmonic in existing technologies, thereby reducing the amount of computation and processing time, lowering hardware requirements, and significantly improving system efficiency and stability. Furthermore, through the synergistic effect of the various components in the digital pre-distortion algorithm module, intermodulation distortion and harmonic distortion can be suppressed simultaneously. The least squares method is used to solve and update the model coefficients, ensuring the long-term stable operation of the system, demonstrating good performance, and significantly improving the linearity of the shortwave transmitter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are incorporated into and constitute a part of this specification and, together with the description, are used to explain the principles of the present invention.

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0040] Figure 1 This is a schematic diagram of the structure of a shortwave transmitter that suppresses intermodulation and harmonic distortion based on a digital predistortion method of the present invention;

[0041] Figure 2 This is a schematic diagram of the structure of the intermodulation suppression submodule in the digital predistortion algorithm module of the utility model;

[0042] Figure 3 This is a schematic diagram of the structure of the harmonic suppression submodule in the digital pre-distortion algorithm module of the utility model;

[0043] Figure 4 This is a comparison diagram of the overall digital predistortion effect of the embodiment of the utility model;

[0044] Figure 5 This is a comparison diagram of the predistortion effect of the fundamental signal of the embodiment of the utility model;

[0045] Figure 6 This is a comparison diagram of the pre-distortion effect of the second harmonic of the embodiment of the utility model;

[0046] Figure 7 This is a comparison diagram of the pre-distortion effect of the third harmonic of the embodiment of the utility model;

[0047] Figure 8 This is a comparison diagram of the pre-distortion effect of the fourth harmonic of the embodiment of the utility model.

[0048] in,

[0049] 1 is the baseband signal;

[0050] 2 is a digital predistortion algorithm module; 21 is an intermodulation suppression submodule; 22 is a harmonic suppression submodule; 23 is an adder; 211 is an intermodulation suppression digital predistortion model; 212 is an intermodulation suppression digital predistortion model coefficient solving unit; 221 is a harmonic suppression digital predistortion model; 222 is a harmonic suppression digital predistortion model coefficient solving unit; 223 is a multiplier;

[0051] 3 is an orthogonal up-conversion module;

[0052] 4 is a digital-to-analog converter;

[0053] 5 is a power amplifier;

[0054] 6 is an analog-to-digital converter;

[0055] 7 is an orthogonal down-conversion module. DETAILED DESCRIPTION

[0056] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible implementations consistent with the present invention. Instead, they are merely examples consistent with certain aspects of the present invention as detailed in the appended claims.

[0057] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in further detail below with reference to the accompanying drawings.

[0058] See also Figures 1 to 8The embodiment of the present invention provides a shortwave transmitter that suppresses intermodulation and harmonic distortion based on a digital predistortion method, which is mainly composed of a digital predistortion algorithm module 2, an orthogonal up-conversion module 3, a digital-to-analog converter (DAC) 4, a power amplifier (PA) 5, an analog-to-digital converter (ADC) 6, and an orthogonal down-conversion module 7. Among them, the first input end of the digital predistortion algorithm module 2 is connected to the baseband signal 1, and the second input end of the digital predistortion algorithm module 2 is connected to the output end of the orthogonal down-conversion module 7, which is used to solve the predistortion signal that can suppress the intermodulation distortion and harmonic distortion of the power amplifier (PA) 5; the input end of the orthogonal up-conversion module 3 is connected to the output end of the digital predistortion algorithm module 2, which is used to shift the frequency of the predistortion signal to the carrier frequency position and output a digital signal; the input end of the digital-to-analog converter (DAC) 4 is connected to the output end of the orthogonal up-conversion module 3, which is used to convert the digital signal output by the orthogonal up-conversion module 3 into a baseband signal. analog signal; the input end of the power amplifier (PA) 5 is connected to the output end of the digital-to-analog converter (DAC) 4, and is used to power amplify the analog signal output by the digital-to-analog converter (DAC) 4; the input end of the analog-to-digital converter (ADC) 6 is connected to the output end of the power amplifier (PA) 5, and is used to convert the analog signal output by the digital-to-analog converter (DAC) 4 and after power amplification by the power amplifier (PA) 5 into a digital signal; the input end of the orthogonal down-conversion module 7 is connected to the output end of the analog-to-digital converter (ADC) 6, and is used to down-convert the digital signal output by the analog-to-digital converter (ADC) 6 to a low frequency.

[0059] It should be noted that the digital predistortion algorithm module 2 in the embodiment of the present invention includes an intermodulation suppression submodule 21, a harmonic suppression submodule 22 and an adder 23. Among them, the first input end of the intermodulation suppression submodule 21 is connected to the baseband signal 1, and the second input end is connected to the output end of the orthogonal down-conversion module 7, for solving a predistortion signal that can suppress the intermodulation distortion of the power amplifier 5; the first input end of the harmonic suppression submodule 22 is connected to the baseband signal 1, and the second input end is connected to the output end of the orthogonal down-conversion module 7, for solving a predistortion signal that can suppress the harmonic distortion of the power amplifier 5; the first input end of the adder 23 is connected to the output end of the intermodulation suppression submodule 21, and the second input end is connected to the output end of the harmonic suppression submodule 22. The output end of the adder 23 is connected to the input end of the orthogonal up-conversion module 3, for adding the solved predistortion signal that suppresses the intermodulation distortion and harmonic distortion of the power amplifier 5, so that the intermodulation distortion and harmonic distortion are suppressed at the same time.

[0060] Specifically, such as Figure 2As shown, in the embodiment of the present invention, the intermodulation suppression submodule 21 includes an intermodulation suppression digital predistortion model 211 and an intermodulation suppression digital predistortion model coefficient solving unit 212. Among them, the first input end of the intermodulation suppression digital predistortion model 211 is connected to the baseband signal 1, the second input end is connected to the output end of the intermodulation suppression digital predistortion model coefficient solving unit 212, the first output end of the intermodulation suppression digital predistortion model 211 is connected to the first input end of the adder 23, and is used to solve the predistortion signal that can suppress the intermodulation distortion of the power amplifier 5; the first input end of the intermodulation suppression digital predistortion model coefficient solving unit 212 is connected to the second output end of the intermodulation suppression digital predistortion model 211, and the second input end is connected to the output end of the orthogonal down-conversion, and is used to solve the model coefficient that can suppress the intermodulation distortion of the power amplifier 5 and transmit it to the intermodulation suppression digital predistortion model 211.

[0061] In an embodiment of the present invention, the intermodulation suppression digital predistortion model 211 and the intermodulation suppression digital predistortion model coefficient solving unit 212 can use a polynomial model or a neural network model to characterize intermodulation distortion. Preferably, the polynomial model includes, but is not limited to, a polynomial (MP) model, a generalized memory polynomial (GMP) model, and the like. Furthermore, the intermodulation suppression digital predistortion model coefficient solving unit 212 can use an algorithm such as a least squares method to solve the model coefficients.

[0062] It is particularly important to emphasize that the harmonic suppression submodule 22 in the embodiment of the present invention includes a harmonic suppression digital predistortion model 221, a harmonic suppression digital predistortion model coefficient solving unit 222 and a multiplier 223, and the connection structure thereof is as follows: Figure 3 Specifically, the first input end of the harmonic suppression digital predistortion model 221 is connected to the baseband signal 1, the second input end is connected to the harmonic suppression digital predistortion model coefficient solving unit 222, and the output end of the harmonic suppression digital predistortion model 221 is connected to the second input end of the adder 23, for solving a predistortion signal capable of suppressing the harmonic distortion of the power amplifier 5; the first input end of the harmonic suppression digital predistortion model coefficient solving unit 222 is connected to the baseband signal 1, and the second input end is connected to the output end of the multiplier 223, for solving the model coefficient capable of suppressing the harmonic distortion of the power amplifier 5 and transmitting it to the harmonic suppression digital predistortion model 221; the first input end of the multiplier 223 is a negative number (-λ), and the second input end is connected to the output end of the orthogonal down-conversion, for inverting and amplifying the output signal of the orthogonal down-conversion by λ times.

[0063] The harmonic suppression digital predistortion model 221 and the harmonic suppression digital predistortion model coefficient solving unit 222 may both use the following formula (1) or other models to characterize the inverted harmonic distortion:

[0064]

[0065] Where H is the harmonic order, M is the memory depth of the harmonic, K is the nonlinear order of the harmonic, and f is the c Indicates the carrier frequency, a h,m,k is the model coefficient.

[0066] Furthermore, the harmonic suppression digital predistortion model coefficient solving unit 222 is used to adjust the hth harmonic model coefficient a h,m,k The positive and negative values can be adjusted to suit different harmonic characteristics.

[0067] Preferably, the harmonic suppression digital predistortion model coefficient solving unit 222 can use the least square method to solve the model coefficients, and the harmonic suppression digital predistortion model coefficient solving unit 222 has the function of saving the model coefficients so as to update the model coefficients during iteration. Among them, the least square method is a mathematical optimization technique that finds the best function match for the data by minimizing the sum of squares of the errors. In the harmonic suppression digital predistortion model, the model coefficients are determined by minimizing the sum of squares of the errors between the actual power amplifier output signal and the model predicted output signal. Specifically, first, a digital predistortion model is established based on the input signal and the known power amplifier characteristics; then, the actually measured power amplifier output signal is compared with the model predicted output signal to calculate the error; and the sum of squares of the errors is minimized by continuously adjusting the model coefficients.

[0068] In addition, the baseband signal 1 used by the digital predistortion algorithm module 2 and the output signal of the orthogonal down-conversion module 7 in the embodiment of the present invention need to undergo preprocessing operations, which include amplitude alignment, delay alignment, and frequency offset compensation.

[0069] In order to further verify the effectiveness of the shortwave transmitter of the utility model, the utility model author conducted the following specific tests:

[0070] In this experiment, the baseband signal generation and the implementation of the digital predistortion algorithm were completed in MATLAB. The baseband signal was a two-tone signal with a 24kHz interval, a carrier frequency of 2MHz, and a sampling rate of 15MHz. The signal was first downloaded to a vector signal generator (ESG4438C) and then injected into the power amplifier. The output signal of the power amplifier was attenuated and then captured by an oscilloscope (MSO5104B). The intermodulation suppression digital predistortion model and the intermodulation suppression digital predistortion model coefficient solution unit adopted the model of the following formula (2), where M is the memory depth representing the intermodulation, K represents the nonlinear order representing the intermodulation, and b m,k and c m,k The harmonic suppression digital predistortion model and the harmonic suppression digital predistortion model coefficient solving unit adopt the model of the above formula (1). The overall intermodulation and harmonic elimination results are as follows: Figure 4 As shown in the figure, it can be seen that the shortwave transmitter proposed by the present invention can suppress intermodulation and harmonic distortion at the same time.

[0071]

[0072] Will Figure 4 The fundamental wave, second harmonic, third harmonic and fourth harmonic in the image can be amplified separately to obtain Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 As can be seen from the figure, compared to the original power amplifier output, after digital pre-distortion processing, the power amplifier output's third-order intermodulation, fifth-order intermodulation, and seventh-order intermodulation suppression capabilities can be improved by 31.69dB, 12.21dB, and 14.35dB, respectively. The second harmonic, third harmonic, and fourth harmonic suppression capabilities can be improved by 48.91dB, 56.09dB, and 45.36dB, respectively. This test is sufficient to demonstrate that the shortwave transmitter provided by the present utility model simultaneously suppresses intermodulation distortion and harmonic distortion, improving the linearity of the power amplifier.

[0073] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0074] It should be understood that the present invention is not limited to the above description and that various modifications and changes can be made without departing from the scope of the present invention. The scope of the present invention is limited only by the appended claims.

Claims

1. A shortwave transmitter based on digital predistortion method to suppress intermodulation and harmonic distortion, characterized in that: It includes a digital predistortion algorithm module (2), an orthogonal up-conversion module (3), a digital-to-analog converter (4), a power amplifier (5), an analog-to-digital converter (6), and an orthogonal down-conversion module (7); The first input end of the digital predistortion algorithm module (2) is connected to the baseband signal (1), and the second input end is connected to the output end of the orthogonal down-conversion module (7), and is used to solve a predistortion signal capable of suppressing intermodulation distortion and harmonic distortion of the power amplifier (5); The input end of the orthogonal up-conversion module (3) is connected to the output end of the digital pre-distortion algorithm module (2), and is used to shift the frequency of the pre-distortion signal to the carrier frequency position and output a digital signal; The input end of the digital-to-analog converter (4) is connected to the output end of the orthogonal up-conversion module (3), and is used to convert the digital signal output by the orthogonal up-conversion module (3) into an analog signal; The input end of the power amplifier (5) is connected to the output end of the digital-to-analog converter (4) and is used to perform power amplification on the analog signal output by the digital-to-analog converter (4); The input end of the analog-to-digital converter (6) is connected to the output end of the power amplifier (5), and is used to convert the analog signal output by the digital-to-analog converter (4) and after power amplification by the power amplifier (5) into a digital signal; The input end of the orthogonal down-conversion module (7) is connected to the output end of the analog-to-digital converter (6) and is used to down-convert the digital signal output by the analog-to-digital converter (6) to a low frequency.

2. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 1, characterized in that: The digital predistortion algorithm module (2) includes an intermodulation suppression submodule (21), a harmonic suppression submodule (22) and an adder (23); The intermodulation suppression submodule (21) has a first input end connected to the baseband signal (1) and a second input end connected to the output end of the orthogonal down-conversion module (7), and is used to obtain a predistortion signal capable of suppressing intermodulation distortion of the power amplifier (5); The first input end of the harmonic suppression submodule (22) is connected to the baseband signal (1), and the second input end is connected to the output end of the orthogonal down-conversion module (7), and is used to solve a predistortion signal capable of suppressing harmonic distortion of the power amplifier (5); The first input end of the adder (23) is connected to the output end of the intermodulation suppression submodule (21), and the second input end is connected to the output end of the harmonic suppression submodule (22). The output end of the adder (23) is connected to the input end of the orthogonal up-conversion module (3). The adder is used to add the solved predistortion signal for suppressing the intermodulation distortion and harmonic distortion of the power amplifier (5) so as to suppress the intermodulation distortion and harmonic distortion at the same time.

3. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 2, characterized in that: The intermodulation suppression submodule (21) includes an intermodulation suppression digital predistortion model (211) and an intermodulation suppression digital predistortion model coefficient solving unit (212); The first input end of the intermodulation suppression digital predistortion model (211) is connected to the baseband signal (1), and the second input end is connected to the output end of the intermodulation suppression digital predistortion model coefficient solving unit (212); the first output end of the intermodulation suppression digital predistortion model (211) is connected to the first input end of the adder (23), and is used to solve a predistortion signal capable of suppressing intermodulation distortion of the power amplifier (5); The intermodulation suppression digital predistortion model coefficient solving unit (212) has a first input end connected to the second output end of the intermodulation suppression digital predistortion model (211), and a second input end connected to the output end of the orthogonal down-conversion, and is used to solve the model coefficients capable of suppressing the intermodulation distortion of the power amplifier (5), and transmit the coefficients to the intermodulation suppression digital predistortion model (211).

4. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 3, characterized in that: The intermodulation suppression digital predistortion model (211) and the intermodulation suppression digital predistortion model coefficient solving unit (212) use a polynomial model or a neural network model to characterize intermodulation distortion.

5. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 3, characterized in that: The intermodulation suppression digital predistortion model coefficient solving unit (212) uses a least square method to solve the model coefficients.

6. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 2, characterized in that: The harmonic suppression submodule (22) includes a harmonic suppression digital predistortion model (221), a harmonic suppression digital predistortion model coefficient solving unit (222) and a multiplier (223); The first input end of the harmonic suppression digital predistortion model (221) is connected to the baseband signal (1), and the second input end is connected to the harmonic suppression digital predistortion model coefficient solving unit (222); the output end of the harmonic suppression digital predistortion model (221) is connected to the second input end of the adder (23), and is used to solve a predistortion signal capable of suppressing harmonic distortion of the power amplifier (5); The harmonic suppression digital predistortion model coefficient solving unit (222) has a first input end connected to the baseband signal (1) and a second input end connected to the output end of the multiplier (223), and is used to solve the model coefficients capable of suppressing the harmonic distortion of the power amplifier (5) and transmit the coefficients to the harmonic suppression digital predistortion model (221); The multiplier (223) has a first input terminal that is a negative number λ and a second input terminal that is connected to the output terminal of the orthogonal down-conversion, and is used to invert and amplify the output signal of the orthogonal down-conversion by λ times.

7. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 6, characterized in that: The harmonic suppression digital predistortion model (221) and the harmonic suppression digital predistortion model coefficient solving unit (222) both use the following formula (1) to characterize the inverted harmonic distortion: Among them, H is the harmonic number represented, M is the memory depth of the harmonic, K is the nonlinear order of the harmonic, f c Indicates the carrier frequency, a h,m,k is the model coefficient.

8. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 7, characterized in that: The harmonic suppression digital predistortion model coefficient solving unit (222) is used to adjust the hth harmonic model coefficient a h,m,k The positive and negative values can be adjusted to suit different harmonic characteristics.

9. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on the digital predistortion method according to claim 6, characterized in that: The harmonic suppression digital predistortion model coefficient solving unit (222) uses a least square method to solve the model coefficients, and the harmonic suppression digital predistortion model coefficient solving unit (222) has the function of saving the model coefficients so as to update the model coefficients during iteration.

10. The shortwave transmitter for suppressing intermodulation and harmonic distortion based on a digital predistortion method according to any one of claims 1 to 9, characterized in that: The baseband signal (1) used by the digital predistortion algorithm module (2) and the output signal of the orthogonal down-conversion module (7) both need to undergo preprocessing operations, and the preprocessing operations include amplitude alignment, time delay alignment, and frequency offset compensation.

Images