Analog predistorter based on third-order intermodulation phase compensation and radio frequency communication system

Abstract

The invention provides an analog predistorter based on third-order intermodulation phase compensation and a radio frequency communication system. The analog predistorter comprises a pushing unit, a power division unit, a predistortion unit and a synthesis unit, the pushing unit comprises a first amplifier used for pre-amplifying an input radio frequency signal; the power division unit is used for dividing the pre-amplified signal into a first branch signal and a second branch signal in an equal-amplitude and in-phase manner; the predistortion unit is divided into two branches which are respectively connected with the first branch signal and the second branch signal, and comprises a second amplifier, a third amplifier and a phase shifter; the second amplifier and the third amplifier are respectively arranged on different branches and are used for adjusting three-order intermodulation component amplitudes of the two branches; the phase shifter is arranged on the branch where the second amplifier or the third amplifier is located and used for adjusting the phase difference of the third-order intermodulation components of the two branches; and the synthesis unit is connected with the two branches of the pre-distortion unit and is used for performing vector synthesis on the signals and outputting pre-distortion signals. The analog predistorter can realize real-time compensation of high-frequency signals, and is suitable for a broadband communication system.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to an analog predistorter and radio frequency communication system based on third-order intermodulation phase compensation. Background Technology

[0002] With the rapid development of wireless communication technology, especially the deployment of 5G and future 6G communication systems, higher demands are placed on the linearity and efficiency of radio frequency power amplifiers. As a key component in communication systems, the nonlinear characteristics of power amplifiers introduce harmonic distortion and intermodulation distortion, severely affecting signal quality and system performance. To meet the demands of modern communication systems for high data rates and spectral efficiency, it is essential to effectively suppress the nonlinear distortion of power amplifiers.

[0003] Linearization techniques directly affect the linearity, power, and efficiency of power amplifiers, thus directly impacting the performance of wireless communication systems. Linearity is typically characterized by third-order intercept point (IMD3). After years of research and development, various linearization techniques have been proposed, including predistortion, power back-off, and negative feedback. Among these, predistortion is a widely used linearization method that preprocesses the signal before it enters the power amplifier to counteract the nonlinear distortion introduced by the amplifier.

[0004] Digital predistortion is a type of predistortion technology that processes signals in the digital domain. It has the advantages of high flexibility and high precision. However, in ultra-high frequency or ultra-wideband scenarios, the complexity and delay of digital signal processing may become limiting factors for digital predistortion technology. Summary of the Invention

[0005] This application provides an analog predistorter and radio frequency communication system based on third-order intermodulation phase compensation to solve the limiting factors of digital predistortion technology in ultra-high frequency or ultra-wideband scenarios.

[0006] In a first aspect, embodiments of this application provide an analog predistorter based on third-order intermodulation phase compensation, comprising: a driving unit, a power dividing unit, a predistortion unit, and a synthesis unit;

[0007] The driving unit includes a first amplifier for pre-amplifying the input radio frequency signal;

[0008] The power divider unit is connected to the output terminal of the drive unit and is used to divide the pre-amplified signal into a first branch signal and a second branch signal with equal amplitude and in phase.

[0009] The predistortion unit is divided into two branches that are respectively connected to the first branch signal and the second branch signal, and includes: a second amplifier, a third amplifier and a phase shifter;

[0010] The second amplifier and the third amplifier are respectively set on different branches to adjust the amplitude of the third-order intermodulation components of the two branches; the phase shifter is set on the branch where the second amplifier is located or the branch where the third amplifier is located to adjust the phase difference of the third-order intermodulation components of the two branches.

[0011] The synthesis unit is connected to two branches of the predistortion unit and is used to vector synthesize the signals output from the two branches to output a predistortion signal.

[0012] In one possible implementation, the phase shifter is an adjustable phase shifter with a phase adjustment range of 0° to 180°, used to dynamically match the nonlinear characteristics of the power amplifier.

[0013] In one possible implementation, the phase shifter adjusts the phase difference between the third-order intermodulation components of the two branches to 180°.

[0014] In one possible implementation, the output power of the second amplifier differs from the output power of the third amplifier and the power at the 1dB compression point.

[0015] In one possible implementation, the output power of the second amplifier and the power at the 1dB compression point are both higher than those of the third amplifier.

[0016] In one possible implementation, the power divider unit is a broadband power divider that supports signal distribution from the S-band to the millimeter-wave band.

[0017] In one possible implementation, the gate voltage and drain voltage of the second and third amplifiers are adjustable to adjust the power of the two third-order intermodulation signals.

[0018] In one possible implementation, the power difference between the third-order intermodulation components of the two branches is less than 3 dB.

[0019] Secondly, embodiments of this application provide a radio frequency communication system, including an analog predistorter based on third-order intermodulation phase compensation as described in the first aspect or any possible implementation of the first aspect, wherein the analog predistorter is connected to the input of a power amplifier for compensating for the nonlinear distortion of the power amplifier.

[0020] In one possible implementation, the system operates in the frequency range of 2 GHz to 40 GHz.

[0021] This application provides an analog predistorter and RF communication system based on third-order intermodulation phase compensation. The analog predistorter includes a driver unit, a power divider unit, a predistortion unit, and a synthesis unit. The driver unit pre-amplifies the input RF signal, the power divider unit splits the signal into two paths with equal amplitude and phase, and the predistortion unit uses a second amplifier and a third amplifier to generate main signals and third-order intermodulation components of different amplitudes in different branches. A phase shifter adjusts the phase difference between the two third-order intermodulation components, and the synthesis unit finally performs vector synthesis. By adjusting the gate voltage and drain voltage of the second and third amplifiers and the phase of the phase shifter, the amplitudes of the two third-order intermodulation components are made similar, and the phase difference is close to or equal to 180°, thus achieving an inverse cancellation effect after synthesis and significantly reducing the nonlinear distortion of the output signal. This application embodiment can achieve real-time compensation of high-frequency signals and is suitable for delay-sensitive broadband communication systems. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the structure of an analog predistorter based on third-order intermodulation phase compensation provided in an embodiment of this application;

[0024] Figure 2a This is a schematic diagram of the frequency domain distribution of the two branch signals and intermodulation components of a predistortion unit according to an embodiment of this application;

[0025] Figure 2b This is a schematic diagram of the frequency domain distribution of the combined signal and intermodulation components output by the synthesis unit in an embodiment of this application;

[0026] Figure 3a and 3b This is a schematic diagram showing the third-order intermodulation test results before and after adding a simulated predistorter based on third-order intermodulation phase compensation, according to an embodiment of this application. Detailed Implementation

[0027] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0028] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0029] Predistortion techniques include digital predistortion techniques and analog predistortion techniques.

[0030] Digital predistortion, by processing signals in the digital domain, offers advantages such as high flexibility and precision. However, in ultra-high frequency or ultra-wideband scenarios, the complexity and latency of digital signal processing can become limiting factors. In contrast, analog predistortion technology processes signals directly in the analog domain, effectively addressing the challenges of high-frequency and wideband signals, and is particularly suitable for scenarios with high real-time requirements.

[0031] Digital predistortion technology utilizes digital signal processing to calculate and process the signal fed back from the output of a power amplifier, and uses software to implement nonlinear compensation. This technology is costly to implement and faces severe limitations in sampling rate, processing latency, and power consumption. Furthermore, group delay in the digital domain feedback path can lead to predistortion mismatch.

[0032] Analog predistortion technology processes signals directly in the analog domain, effectively addressing the challenges of high-frequency and broadband signals, and is particularly suitable for scenarios with high real-time requirements. However, current analog predistortion techniques have limited adjustable parameters, generate a limited number of nonlinear signals, and involve a cumbersome debugging process.

[0033] Based on research on S-band analog predistortion technology, this application provides an analog predistorter to improve the degree of nonlinear distortion of solid-state power amplifiers and enhance the applicability and design efficiency of the predistorter.

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0035] Figure 1 This is a schematic diagram of the structure of an analog predistorter based on third-order intermodulation phase compensation provided in an embodiment of this application, as shown below. Figure 1 The diagram shows: a driving unit 10, a power dividing unit 20, a predistortion unit 30, and a synthesis unit 40.

[0036] The driving unit 10 includes a first amplifier U1, which is used to pre-amplify the input radio frequency signal.

[0037] The power divider unit 20 is connected to the output terminal of the drive unit 10 and is used to divide the pre-amplified signal into a first branch signal and a second branch signal with equal amplitude and phase.

[0038] The predistortion unit 30 is divided into two branches that are respectively connected to the first branch signal and the second branch signal, including: the second amplifier U2, the third amplifier U3 and the phase shifter E0.

[0039] The second amplifier U2 and the third amplifier U3 are respectively set on different branches to adjust the amplitude of the third-order intermodulation components of the two branches; the phase shifter E0 is set on the branch where the second amplifier U2 is located or the branch where the third amplifier U3 is located to adjust the phase difference of the third-order intermodulation components of the two branches. Figure 1 In the example shown, the phase shifter E0 is located in the branch where the second amplifier U2 is located.

[0040] The synthesis unit 40 is connected to two branches of the predistortion unit 30 and is used to vector synthesize the signals output from the two branches to output a predistortion signal.

[0041] From the perspective of suppressing third-order intermodulation, a dual-path unbalanced vector synthesis method is adopted. This method generates abundant third-order intermodulation components by adjusting the gate and drain voltages of the two branch amplifiers. The phase of the third-order intermodulation signal is controlled by adjusting the phase of the phase shifter E0 in the same path, adjusting the signal to a state where its third-order intermodulation power is equal to and its phase is opposite to that of the main signal. The synthesized third-order intermodulation signals cancel each other out after superposition, significantly reducing the third-order intermodulation amplitude of the synthesized signal and improving the linearity of the entire system. Figure 2a and Figure 2b The diagram illustrates the principle of the analog predistorter based on third-order intermodulation phase compensation in this application more intuitively. The third-order intermodulation components are superimposed in opposite phase in the frequency domain and cancel each other out.

[0042] like Figure 1 As shown, taking the use of the fewest components to achieve complex functions as the starting point, the RF link of the simulated predistorter is built with only 6 components. Although the link is simple, it has a variety of adjustable parameters that are flexible, including the gate voltage and drain voltage of the multiplexer, the phase control of the phase shifter E0, etc., so as to combine multiple synthesis states and select the optimal performance indicators through debugging.

[0043] In this embodiment, a third-order intermodulation phase compensation-based analog predistorter is constructed by a driving unit 10, a power divider unit 20, a predistortion unit 30, and a synthesis unit 40. The driving unit 10 pre-amplifies the input RF signal, the power divider unit 20 splits the signal into two equal-amplitude, in-phase paths, and the predistortion unit 30 uses the second amplifier U2 and the third amplifier U3 to generate main signals and third-order intermodulation components of different amplitudes in different branches. The phase difference between the two third-order intermodulation components is adjusted by the phase shifter E0, and finally, the synthesis unit 40 performs vector synthesis. By adjusting the gate voltage and drain voltage of the second amplifier U2 and the third amplifier U3, and the phase of the phase shifter E0, the amplitudes of the two third-order intermodulation components are made similar, and the phase difference is close to or equal to 180°, thus achieving an inverse cancellation effect after synthesis and significantly reducing the nonlinear distortion of the output signal. This embodiment can achieve real-time compensation of high-frequency signals and is suitable for delay-sensitive broadband communication systems.

[0044] In one possible implementation, the phase shifter E0 is an adjustable phase shifter E0 with a phase adjustment range of 0° to 180°, used to dynamically match the nonlinear characteristics of the power amplifier.

[0045] In this embodiment, by defining the phase shifter E0 as an adjustable phase shifter with a phase adjustment range of 0° to 180°, the nonlinear characteristics of different power amplifiers can be dynamically matched. When the nonlinear characteristics of the power amplifier shift due to changes in temperature, frequency, or load, the phase shifter E0 can adjust the phase difference in real time (e.g., to match to 180°) to ensure the continuous cancellation of third-order intermodulation components, improve the system's adaptability to different operating environments, and avoid compensation failure caused by a fixed phase difference.

[0046] In one possible implementation, the phase shifter E0 adjusts the phase difference between the third-order intermodulation components of the two branches to 180°.

[0047] In this embodiment, the phase difference between the two third-order intermodulation components is adjusted to 180° using a phase shifter E0. Based on the wave interference principle, the cancellation effect is maximized using the principle of anti-phase superposition. When the amplitudes of the two third-order intermodulation components are similar and their phases are opposite, the total power after synthesis is reduced to a minimum, thereby directly improving the linearity of the output signal and achieving efficient suppression of nonlinear distortion.

[0048] In one possible implementation, the output power of the second amplifier U2 is different from the output power of the third amplifier U3 and the power at the 1dB compression point.

[0049] In this embodiment, the output power and 1dB compression point of the second amplifier U2 and the third amplifier U3 are different, resulting in a significant difference in the power of the two main signals (e.g., a difference greater than 10dB), while the amplitude difference of the third-order intermodulation components is small (a difference less than 3dB). The difference in the main signal power ensures the stability of the synthesized main signal power, while the similar amplitude of the intermodulation components provides the basis for phase cancellation, thereby specifically eliminating nonlinear distortion without affecting the main signal.

[0050] In one possible implementation, the output power of the second amplifier U2 and the power at the 1dB compression point are both higher than those of the third amplifier U3.

[0051] Among them, the second amplifier U2 is the main output device, and the branch containing the third amplifier U3 can generate a signal with low main signal power and high third-order intermodulation signal power, so as to achieve the purpose of large difference in amplitude between the two main signals and small difference in amplitude between the third-order intermodulation signals.

[0052] In this embodiment, the output power and the power at the 1dB compression point (i.e., the P-1 index) of the second amplifier U2 are both higher than those of the third amplifier U3, ensuring that the main signal power of the branch containing the second amplifier U2 is much higher than that of the branch containing the third amplifier U3, while the power of the two third-order intermodulation components is close. This unbalanced design avoids power loss of the main signal after synthesis by leveraging the strong dominance of the main signal, while achieving efficient cancellation through the low difference of the intermodulation components, thus optimizing the overall linearity of the predistorter.

[0053] In one possible implementation, the difference between the output power of the second amplifier U2 and the output power of the third amplifier U3 is greater than 10dB, and the difference between the power at the 1dB compression point of the second amplifier U2 and the power at the 1dB compression point of the third amplifier U3 is less than 3dB.

[0054] In one possible implementation, the power divider unit 20 is a broadband power divider that supports signal distribution from the S-band to the millimeter-wave band.

[0055] In this embodiment, a broadband power divider supporting S-band to millimeter-wave frequencies is employed to extend the operating frequency range of the predistorter. This design makes the analog predistorter suitable for the high-frequency requirements of 5G / 6G communication systems, solving the bandwidth limitation problem of traditional power dividers, while ensuring the amplitude and phase consistency of signal distribution, providing a fundamental guarantee for third-order intermodulation compensation in high-frequency scenarios.

[0056] In one possible implementation, the gate voltage and drain voltage of the second amplifier U2 and the third amplifier U3 are adjustable to adjust the power of the two third-order intermodulation signals.

[0057] In this embodiment, by adjusting the gate voltage and drain voltage of the second amplifier U2 and the third amplifier U3, the power of the two third-order intermodulation components can be controlled separately, adjusting them to a state where the amplitudes of the two third-order intermodulation signals differ slightly. For example, increasing the drain voltage of the second amplifier U2 can enhance its intermodulation component amplitude, while decreasing the gate voltage of the third amplifier U3 can suppress its intermodulation component, thereby achieving fine matching of the two intermodulation components. This parameter adjustment mechanism provides flexibility and accuracy for nonlinear compensation, and is particularly suitable for complex and variable radio frequency environments.

[0058] In one possible implementation, the power difference between the third-order intermodulation components of the two branches is less than 3 dB.

[0059] In this embodiment, the power difference between the two third-order intermodulation components is less than 3dB, ensuring that the amplitudes of the two intermodulation signals are close and avoiding a decrease in phase cancellation effect due to excessive amplitude difference. For example, if the power difference between the two intermodulation components exceeds 3dB, even if the phase difference is 180°, the residual intermodulation components will still affect linearity. This implementation method ensures cancellation efficiency through parameter constraints, making the synthesized third-order intermodulation suppression effect stable and controllable.

[0060] To verify the effectiveness of the analog predistorter based on third-order intermodulation phase compensation provided in the embodiments of this application, its performance was verified, and the results were obtained. Figure 3a and 3b A schematic diagram of the results of the third-order intermodulation test.

[0061] Figure 3a and 3b The diagrams show the test results of third-order intermodulation before and after adding a simulated predistorter based on third-order intermodulation phase compensation, according to an embodiment of this application. The experimental results confirm that by adjusting the gate voltage and drain voltage of the two branch amplifiers and the phase of the phase shifter, the simulated predistorter can operate normally and exhibits excellent performance. With a 2dB back-off of saturated power output, the third-order intermodulation can be improved from -19.3dB to -41.9dB, achieving linearity optimization.

[0062] This application provides a radio frequency communication system, including an analog predistorter based on third-order intermodulation phase compensation as in any of the above possible embodiments. The analog predistorter is connected to the input of a power amplifier and is used to compensate for the nonlinear distortion of the power amplifier.

[0063] In one possible implementation, the system operates in the frequency range of 2 GHz to 40 GHz.

[0064] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An analog predistorter based on third-order intermodulation phase compensation, characterized in that, include: Drive unit, power distribution unit, predistortion unit, and synthesis unit; The driving unit includes a first amplifier for pre-amplifying the input radio frequency signal; The power divider unit is connected to the output terminal of the drive unit and is used to divide the pre-amplified signal into a first branch signal and a second branch signal with equal amplitude and in phase. The predistortion unit is divided into two branches that are respectively connected to the first branch signal and the second branch signal, and includes: a second amplifier, a third amplifier and a phase shifter; The second amplifier and the third amplifier are respectively set on different branches to adjust the amplitude of the third-order intermodulation components of the two branches; the phase shifter is set on the branch where the second amplifier is located or the branch where the third amplifier is located to adjust the phase difference of the third-order intermodulation components of the two branches. The synthesis unit is connected to two branches of the predistortion unit and is used to perform vector synthesis of the signals output from the two branches to output a predistortion signal.

2. The analog predistorter according to claim 1, characterized in that, The phase shifter is an adjustable phase shifter with a phase adjustment range of 0° to 180°, used to dynamically match the nonlinear characteristics of the power amplifier.

3. The analog predistorter according to claim 1, characterized in that, The phase shifter adjusts the phase difference between the third-order intermodulation components of the two branches to 180°.

4. The analog predistorter according to claim 1, characterized in that, The output power of the second amplifier is different from the output power and the power at the 1dB compression point of the third amplifier.

5. The analog predistorter according to claim 3, characterized in that, The output power and the power at the 1dB compression point of the second amplifier are both higher than those of the third amplifier.

6. The analog predistorter according to claim 1, characterized in that, The power divider unit is a broadband power divider that supports signal distribution from S-band to millimeter-wave frequency bands.

7. The analog predistorter according to claim 1, characterized in that, The gate voltage and drain voltage of the second and third amplifiers are adjustable to adjust the power of the two third-order intermodulation signals.

8. The analog predistorter according to claim 7, characterized in that, The power difference between the third-order intermodulation components of the two branches is less than 3dB.

9. A radio frequency communication system, characterized in that, Includes an analog predistorter based on third-order intermodulation phase compensation as described in any one of claims 1-8, wherein the analog predistorter is connected to the input of a power amplifier for compensating for the nonlinear distortion of the power amplifier.

10. The radio frequency communication system according to claim 9, characterized in that, The system operates in the frequency range of 2 GHz to 40 GHz.

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