Short wave transmitter and method for inhibiting intermodulation and harmonic distortion

Abstract

The invention belongs to the technical field of wireless communication, and particularly discloses a short-wave transmitter and method for inhibiting intermodulation and harmonic distortion, and the short-wave transmitter is designed based on a digital pre-distortion method, and 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 invention not only realizes suppression of intermodulation distortion and harmonic distortion at the same time, but also improves the linearity of the power amplifier.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communication, relates to the application of adaptive digital pre-distortion technology, and specifically relates to a shortwave transmitter and method for suppressing intermodulation and harmonic distortion. Background Art

[0002] In the field of wireless communications, shortwave is widely used in various communication fields due to its unique sky wave propagation mode, no need for expensive infrastructure, and strong survivability. Shortwave transmitters are key components of communication systems, and the power amplifier is one of the core components. In order to obtain better output performance, the power amplifier usually works near the saturation region, but this will cause nonlinear distortion in the output signal, mainly including intermodulation distortion and harmonic distortion, which greatly affects the signal quality and communication effect of the shortwave transmitter.

[0003] In order to correct the nonlinear distortion of power amplifiers, many linearization technologies have been applied in practical projects, among which digital predistortion (DPD) technology is a better solution for correcting the nonlinear distortion of power amplifiers. However, traditional DPD technology is mainly used to suppress the intermodulation distortion of power amplifiers, and a large analog filter group is used to suppress harmonic distortion. However, this method has problems such as large size, high cost and power consumption in practical applications, which is not conducive to the miniaturization and low power consumption requirements of shortwave transmitter systems. At the same time, the performance of analog filter groups is limited, and it is difficult to completely eliminate harmonic distortion, which affects the signal quality and communication effect of shortwave transmitters.

[0004] It can be seen that the practice of suppressing harmonic distortion through analog filter groups is obviously not conducive to the miniaturization and low power consumption of the transmitter. In recent years, DPD technology has been applied to the suppression of harmonic distortion. The existing harmonic elimination methods are mainly divided into two categories: one is to achieve harmonic elimination with baseband signals, and its DPD algorithm module uses complex signals before up-conversion; the other is to achieve harmonic elimination with digital RF signals, and its DPD algorithm uses real signals after up-conversion. Among them, the baseband signal has many advantages over the digital RF signal in terms of high signal processing accuracy, strong algorithm design flexibility, convenient system integration and debugging, and high resource utilization efficiency. Therefore, it is gradually becoming a trend to achieve harmonic elimination with baseband signals. For example, China's patent CN114826298A, entitled "A shortwave transmitter harmonic suppression device and method", uses baseband signals to achieve harmonic elimination. However, in the preprocessing module of this solution, the received digital harmonic signal needs to be digitally separated and extracted, aligned with the input baseband signal, and spectrum shifted in sequence. Each harmonic must go through the above complex process, which increases the system's computational complexity and processing time, and also increases the requirements for hardware equipment, which affects the system's efficiency and stability to a certain extent.

[0005] In view of this, this invention is proposed. Summary of the invention

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

[0007] The purpose of the present invention is to be solved by the following technical solutions:

[0008] The present invention provides a shortwave transmitter for suppressing intermodulation and harmonic distortion. The shortwave transmitter is based on a digital predistortion method and includes 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 pre-distortion 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, so as to solve the pre-distortion signal capable of suppressing 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 move 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 amplified 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] Wherein, the baseband signal used by the digital predistortion algorithm module and the signal output by the orthogonal down-conversion module both need to undergo preprocessing operations, and the preprocessing operations include amplitude alignment, delay alignment and frequency offset compensation.

[0016] Further, the digital predistortion algorithm module includes an intermodulation suppression submodule, a harmonic suppression submodule and an adder;

[0017] 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;

[0018] 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 pre-distortion signal that can suppress the harmonic distortion of the power amplifier;

[0019] 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 pre-distortion 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.

[0020] Further, the intermodulation suppression submodule includes an intermodulation suppression digital predistortion model and an intermodulation suppression digital predistortion model coefficient solving unit;

[0021] 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;

[0022] 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.

[0023] 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 the intermodulation distortion.

[0024] Furthermore, the intermodulation suppression digital predistortion model coefficient solving unit uses a least squares method to solve the model coefficients.

[0025] Further, the harmonic suppression submodule includes a harmonic suppression digital predistortion model, a harmonic suppression digital predistortion model coefficient solving unit and a multiplier;

[0026] The first input end of the harmonic suppression digital pre-distortion model is connected to the baseband signal, the second input end is connected to the harmonic suppression digital pre-distortion model coefficient solving unit, and the output end of the harmonic suppression digital pre-distortion model is connected to the second input end of the adder, for solving the pre-distortion signal capable of suppressing the harmonic distortion of the power amplifier;

[0027] The first input end of the harmonic suppression digital pre-distortion 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 pre-distortion model;

[0028] 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.

[0029] 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;

[0030]

[0032] Among them, H is the harmonic number represented, M is the memory depth of the harmonic, K is the nonlinear order of the harmonic, and f c Indicates the carrier frequency, a h,m,k is the model coefficient.

[0033] 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.

[0034] Furthermore, the harmonic suppression digital pre-distortion model coefficient solving unit adopts a least square method to solve the model coefficients, and the harmonic suppression digital pre-distortion model coefficient solving unit has a function of saving the model coefficients so as to update the model coefficients during iteration.

[0035] 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.

[0036] In addition, the present invention provides a method for suppressing intermodulation and harmonic distortion based on the above shortwave transmitter, which specifically includes the following steps:

[0037] Step 1: Processing the input baseband signal through a digital pre-distortion algorithm module to obtain a pre-distortion signal for solving a problem capable of suppressing intermodulation distortion and harmonic distortion of a power amplifier;

[0038] Step 2: The frequency of the predistortion signal is shifted to the carrier frequency position through an orthogonal up-conversion module, and a digital signal is output;

[0039] Step 3: Convert the digital signal into an analog signal through a digital-to-analog converter;

[0040] Step 4: amplifying the analog signal by a power amplifier;

[0041] Step 5: Convert the analog signal output by the digital-to-analog converter and amplified by the power amplifier into a digital signal through an analog-to-digital converter;

[0042] Step 6: Down-convert the digital signal output by the analog-to-digital converter to a low frequency through an orthogonal down-conversion module.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 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. The shortwave transmitter has at least the following advantages over the prior art:

[0045] First, it effectively solves a series of problems caused by suppressing harmonic distortion through analog filter groups in traditional technologies, such as large size, high cost, high power consumption and limited performance, which greatly helps the shortwave transmitter system to achieve the goal of miniaturization and low power consumption. Traditional analog filter groups not only take up a lot of space, increase the size and weight of the equipment, and hinder miniaturization design, but also increase the overall production cost of the equipment due to their high production cost, and the subsequent maintenance and replacement costs are also high. At the same time, the high power consumption characteristics are also contrary to the current low power consumption demand.

[0046] Second, the existing baseband signal harmonic elimination method has been optimized. Only one down-conversion and delay alignment operation is required, and the implementation process is relatively easy, avoiding the situation where complex operations are performed on each harmonic as in the prior art, thereby reducing the amount of calculation and processing time, reducing hardware requirements, and significantly improving system efficiency and stability. In addition, through the synergistic effect of various parts in the digital pre-distortion algorithm module, intermodulation distortion and harmonic distortion can be suppressed at the same time, and the least squares method is used to solve and update the model coefficients, ensuring the long-term stable operation of the system, showing good performance, and greatly improving the linearity of the shortwave transmitter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 It is a schematic diagram of the structure of a shortwave transmitter for suppressing intermodulation and harmonic distortion according to the present invention;

[0050] Figure 2 It is a schematic diagram of the structure of the intermodulation suppression submodule in the digital predistortion algorithm module of the present invention;

[0051] Figure 3 It is a schematic diagram of the structure of the harmonic suppression submodule in the digital predistortion algorithm module of the present invention;

[0052] Figure 4 is a comparison diagram of the overall digital pre-distortion effect of the embodiment of the present invention;

[0053] Figure 5 is a comparison diagram of predistortion effects of fundamental wave signals according to an embodiment of the present invention;

[0054] Figure 6 is a comparison diagram of the second harmonic predistortion effect of an embodiment of the present invention;

[0055] Figure 7 is a comparison diagram of the pre-distortion effect of the third harmonic in an embodiment of the present invention;

[0056] Figure 8 It is a comparison diagram of the fourth harmonic pre-distortion effect of the embodiment of the present invention.

[0057] in,

[0058] 1 is the baseband signal;

[0059] 2 is a digital pre-distortion algorithm module; 21 is an intermodulation suppression submodule; 22 is a harmonic suppression submodule; 23 is an adder; 211 is an intermodulation suppression digital pre-distortion model; 212 is an intermodulation suppression digital pre-distortion model coefficient solving unit; 221 is a harmonic suppression digital pre-distortion model; 222 is a harmonic suppression digital pre-distortion model coefficient solving unit; 223 is a multiplier;

[0060] 3 is an orthogonal up-conversion module;

[0061] 4 is a digital-to-analog converter;

[0062] 5 is a power amplifier;

[0063] 6 is an analog-to-digital converter;

[0064] 7 is an orthogonal down-conversion module. DETAILED DESCRIPTION

[0065] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0066] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0067] See also Figures 1 to 8 A shortwave transmitter for suppressing intermodulation and harmonic distortion provided by an embodiment of the present invention is designed based on a digital predistortion method, and 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, so as to solve a predistortion signal capable of suppressing 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, so as 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, so as 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.

[0068] 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, which is used to solve the 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, which is used to solve the 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, and the output end of the adder 23 is connected to the input end of the orthogonal up-conversion module 3, which is used to add the solved predistortion signal that suppresses the intermodulation distortion and harmonic distortion of the power amplifier 5, so that it can suppress the intermodulation distortion and harmonic distortion at the same time.

[0069] Specifically, Figure 2 As shown, the intermodulation suppression submodule 21 in the embodiment of the present invention 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, 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, which 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, which 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.

[0070] In the 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 the intermodulation distortion. Preferably, the polynomial model includes but is not limited to a polynomial (MP) model, a generalized memory polynomial (GMP) model, etc. In addition, 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.

[0071] 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 3As shown. 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, which is used to solve the predistortion signal that can suppress 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, which is used to solve the model coefficient that can suppress the harmonic distortion of the power amplifier 5, and transmit 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, which is used to invert and amplify the output signal of the orthogonal down-conversion by λ times.

[0072] 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:

[0073]

[0075] In the formula, H is the harmonic order, M is the memory depth of the harmonic, K is the nonlinear order of the harmonic, and f is c Indicates the carrier frequency, a h,m,k is the model coefficient.

[0076] 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.

[0077] Preferably, the harmonic suppression digital pre-distortion model coefficient solving unit 222 can use the least square method to solve the model coefficient, and the harmonic suppression digital pre-distortion model coefficient solving unit 222 has the function of saving the model coefficient so as to update the model coefficient 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 pre-distortion model, the model coefficient is 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 pre-distortion 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.

[0078] 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, including amplitude alignment, delay alignment, and frequency offset compensation.

[0079] On the other hand, the present invention provides a method for suppressing intermodulation and harmonic distortion based on the above shortwave transmitter, and the specific process is as follows:

[0080] 1) processing the input baseband signal 1 through the digital predistortion algorithm module 2 to obtain a predistortion signal for solving a problem capable of suppressing intermodulation distortion and harmonic distortion of a power amplifier (PA) 5;

[0081] 2) The frequency of the predistortion signal is moved to the carrier frequency position through the orthogonal up-conversion module 3, and a digital signal is output;

[0082] 3) Converting the digital signal into an analog signal through a digital-to-analog converter (DAC) 4;

[0083] 4) amplifying the power of the analog signal through a power amplifier (PA) 5;

[0084] 5) converting the analog signal output by the digital-to-analog converter (DAC) 4 and amplified by the power amplifier (PA) 5 into a digital signal through the analog-to-digital converter (ADC) 6;

[0085] 6) Down-converting the digital signal output by the analog-to-digital converter (ADC) 6 to a low frequency through an orthogonal down-conversion module (7).

[0086] Among them, the digital pre-distortion algorithm module 2 is composed of an intermodulation suppression submodule 21, a harmonic suppression submodule 22 and an adder 23, and the adder 23 is used to add the pre-distortion signal of the intermodulation distortion of the power amplifier (PA) 5 solved by the intermodulation suppression submodule 21 and the pre-distortion signal of the harmonic distortion of the power amplifier (PA) 5 solved by the harmonic suppression submodule 22, so as to suppress the intermodulation distortion and harmonic distortion at the same time. Compared with the prior art, which needs to add a digital pre-distortion module after up-conversion, the present invention realizes harmonic elimination on the baseband signal, and only needs to add a harmonic elimination module to the original system architecture based on digital pre-distortion to realize intermodulation distortion suppression, and does not need to change the position of the digital pre-distortion module, which is convenient for system design; in addition, the present invention believes that the pre-distortion signal that can suppress each harmonic is not necessarily inverse to the corresponding harmonics in the output signal of the power amplifier fed back. In addition, the present invention also relates to the suppression of intermodulation distortion, and can simultaneously achieve the suppression of intermodulation distortion and harmonic distortion.

[0087] In order to further verify the efficacy of the shortwave transmitter of the present invention, the inventor conducted the following specific experiments:

[0088] In this experiment, the generation of baseband signals and the implementation of digital pre-distortion algorithms were completed in MATLAB. The baseband signal was a two-tone signal with a 24kHz interval, a carrier frequency of 2MHz, and a sampling frequency of 15MHz. The signal was first downloaded to a vector signal generator (ESG4438C) and then injected into a power amplifier. The output signal of the power amplifier was attenuated and then captured by an oscilloscope (MSO5104B). The intermodulation suppression digital pre-distortion model and the intermodulation suppression digital pre-distortion model coefficient solution unit adopt the model of the following formula (2), where M is the memory depth representing intermodulation, K represents the nonlinear order representing intermodulation, and b m,k and c m,k is the model coefficient. 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.

[0089]

[0090] 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 . It can be seen from the figure that compared with the original output of the power amplifier, after digital pre-distortion processing, the suppression capabilities of the third-order intermodulation, fifth-order intermodulation, and seventh-order intermodulation output of the power amplifier can be increased by 31.69dB, 12.21dB, and 14.35dB respectively, and the suppression capabilities of the second harmonic, third harmonic, and fourth harmonic can be increased by 48.91dB, 56.09dB, and 45.36dB respectively. This experiment is sufficient to illustrate that the use of the shortwave transmitter provided by the present invention can simultaneously suppress intermodulation distortion and harmonic distortion, and improve the linearity of the power amplifier.

[0091] The above description is only a specific embodiment of the present invention, so that those skilled in the art can 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 can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0092] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A shortwave transmitter for suppressing intermodulation and harmonic distortion, the shortwave transmitter is based on a digital predistortion method, characterized in that: It comprises a digital pre-distortion 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 pre-distortion 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 the pre-distortion signal capable of suppressing the 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 amplify the power of 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; The baseband signal (1) used by the digital predistortion algorithm module (2) and the signal output by the orthogonal down-conversion module (7) both need to undergo a preprocessing operation, and the preprocessing operation includes amplitude alignment, delay alignment and frequency offset compensation.

2. The shortwave transmitter for suppressing intermodulation and harmonic distortion according to claim 1, characterized in that: The digital pre-distortion algorithm module (2) comprises an intermodulation suppression submodule (21), a harmonic suppression submodule (22) and an adder (23); 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), 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 obtain 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), and is used to add up 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 according to claim 2, characterized in that: The intermodulation suppression submodule (21) comprises 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), the second input end is connected to the output end of the intermodulation suppression digital predistortion model coefficient solving unit (212), and the first output end of the intermodulation suppression digital predistortion model (211) is connected to the first input end of the adder (23), for solving a predistortion signal capable of suppressing 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 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 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 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 according to claim 2, characterized in that: The harmonic suppression submodule (22) comprises 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 pre-distortion model (221) is connected to the baseband signal (1), and the second input end is connected to the harmonic suppression digital pre-distortion model coefficient solving unit (222); the output end of the harmonic suppression digital pre-distortion model (221) is connected to the second input end of the adder (23), and is used to solve a pre-distortion signal capable of suppressing harmonic distortion of the power amplifier (5); The first input end of the harmonic suppression digital pre-distortion 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), and is used to solve the model coefficients capable of suppressing the harmonic distortion of the power amplifier (5), and transmit them to the harmonic suppression digital pre-distortion 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 according to claim 6, characterized in that: The harmonic suppression digital pre-distortion model (221) and the harmonic suppression digital pre-distortion model coefficient solving unit (222) both use the following formula (1) to characterize the reverse 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, and f c Indicates the carrier frequency, a h,m,k is the model coefficient.

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

10. A method for suppressing intermodulation and harmonic distortion, characterized in that: The method is based on the shortwave transmitter according to any one of claims 1 to 9, and specifically comprises the following steps: Step 1, processing the input baseband signal (1) through a digital predistortion algorithm module (2) to obtain a predistortion signal for solving a problem capable of suppressing intermodulation distortion and harmonic distortion of a power amplifier (5); Step 2: The frequency of the predistortion signal is shifted to the carrier frequency position by an orthogonal up-conversion module (3), and a digital signal is output; Step 3: converting the digital signal into an analog signal through a digital-to-analog converter (4); Step 4: amplifying the analog signal by a power amplifier (5); Step 5, converting the analog signal output by the digital-to-analog converter (4) and amplified by the power amplifier (5) into a digital signal through an analog-to-digital converter (6); Step 6: Down-convert the digital signal output by the analog-to-digital converter (6) to a low frequency through an orthogonal down-conversion module (7).

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