Radio frequency power amplifier signal predistortion method, system and product based on feedback transmission compensation

Abstract

The invention discloses a radio frequency power amplifier signal predistortion method, system and product based on feedback transmission compensation, and relates to the field of radio frequency signal control. The method comprises the following steps: S100, acquiring an original baseband signal; s200, outputting a pre-distortion signal to an uplink through a digital pre-distorter; s300, the uplink obtains a high-frequency analog signal and inputs the high-frequency analog signal to a power amplifier; s400, the power amplifier outputs a linearized amplification signal to a coupler; s500, the coupler outputs one path of antenna transmitting signal and one path of feedback signal to a downlink; s600, the downlink obtains a feedback baseband signal, and then phase alignment is carried out on the feedback baseband signal and the reference signal; and S700, comparing the phase alignment signal with the pre-distortion prediction signal to obtain a prediction error, and adjusting a preset pre-distortion coefficient of the digital pre-distorter based on the prediction error. According to the invention, the inherent deviation of the feedback link can be compensated adaptively with high precision, real-time signal alignment can be carried out, and the pre-distortion coefficient of the DPD model can be effectively corrected.

Description

Technical Field

[0001] This application relates to the field of radio frequency signal control, specifically to a method, system, and product for radio frequency power amplifier signal predistortion based on feedback transmission compensation. Background Technology

[0002] In the field of wireless communication technology, especially in high-frequency, high-bandwidth applications such as satellite communication and 5G communication, the radio frequency power amplifier (PA) is a key component in the transmitter system. Its function is to amplify the radio frequency signal to a sufficient power level for effective transmission. To ensure the amplifier efficiency of the PA, it is usually required that the PA operate in a near-saturation nonlinear region. At this point, the nonlinear characteristics of the PA will distort the amplified signal, resulting in nonlinear distortion of the signal.

[0003] Digital pre-distortion (DPD) is an effective technique for eliminating nonlinear distortion in power amplifiers (PAs). Its principle is to apply a pre-distortion, opposite to the nonlinear characteristics of the PA, before the baseband digital signal is input to the PA, making the cascaded system of the pre-distorter and power amplifier exhibit linear characteristics. This pre-distortion is obtained through a pre-configured pre-distortion model.

[0004] A typical DPD system extracts a portion of the power amplifier output signal through a coupler, compares it with the original transmitted signal via a feedback link, and thus adaptively updates the predistortion model parameters to cope with the continuous changes in the nonlinear characteristics of the PA during continuous operation.

[0005] However, in practical applications, technicians have found that there are unavoidable physical deviations in time and phase between the data obtained from the feedback channel and the original baseband signal at the transmitting end. The existence of these deviations causes the AM-AM (amplitude-amplitude) and AM-PM (amplitude-phase) characteristic curves of the power amplifier to diverge and fail to converge when the feedback signal is compared with the original reference signal. This makes it impossible to extract the nonlinear characteristics of the power amplifier, resulting in inaccurate adjustment of the subsequent predistortion coefficients and deterioration of the transmission performance of the radio frequency signal system. Summary of the Invention

[0006] The purpose of this application is to overcome the shortcomings of the prior art and provide a method, system and product for predistortion of radio frequency power amplifier signals based on feedback transmission compensation. This method can adaptively and accurately compensate for the inherent deviation of the feedback link and perform real-time signal alignment, thereby eliminating the divergence phenomenon of AM-AM / AM-PM curves and effectively correcting the predistortion coefficients of the DPD model, thereby improving the predistortion performance and signal transmission performance of high-speed data transmission terminals such as satellites.

[0007] In the first aspect, this application provides a method for predistorting radio frequency power amplifier signals based on feedback transmission compensation, the technical solution of which includes the following steps; S100: Acquire the raw baseband signal and input it into the digital predistorter; S200, the digital predistorter outputs a predistorted signal to the uplink based on a preset predistortion coefficient; S300, the uplink upconverts the predistorted signal to a high-frequency analog signal input to the power amplifier; S400, the power amplifier outputs a linearized amplified signal to the coupler; The S500 coupler outputs one antenna transmit signal and one feedback signal to the downlink; In S600, the downlink downconverts the feedback signal to the feedback baseband signal, then extracts the original baseband signal as the reference signal, calculates the phase difference between the feedback baseband signal and the reference signal, and shifts the phase of the feedback baseband signal according to the phase difference to obtain the phase-aligned signal. S700 compares the phase alignment signal with the predistortion prediction signal obtained by the digital predistorter based on the preset predistortion coefficient to obtain the prediction error, and adjusts the preset predistortion coefficient of the digital predistorter based on the prediction error.

[0008] By adopting the above technical solution, the feedback baseband signal obtained through the downlink is phase-aligned with the reference signal extracted from the original baseband signal. This eliminates the propagation delay of the original baseband signal through the digital predistorter, uplink, power amplifier output, and downlink. When the digital predistorter adjusts the preset predistortion coefficient through the feedback signal, it can align the original baseband signal with the feedback baseband signal by time delay calibration. This allows the nonlinear distortion characteristic curve of the power amplifier to converge, thereby enabling precise control of the preset predistortion coefficient of the digital predistorter.

[0009] Preferably, in S600, the phase-shifting of the feedback baseband signal to obtain the phase-aligned signal specifically includes the following steps: S601 preprocesses the reference signal x1(n) and the feedback baseband signal x2(n) by using a bandpass filter to remove noise and DC components outside the signal passband; S602, the cross-correlation function R(m) of the reference signal x1(n) and the feedback baseband signal x2(n) is calculated as follows: ; Where t represents the sampling time of the reference signal x1(n) and the feedback baseband signal x2(n), ∗ indicates taking the conjugate, and m is the time offset; the cross-correlation function R(m) characterizes the similarity between the reference signal x1(n) and the feedback baseband signal x2(n) under different relative delays m, and m=τ is used to calculate the maximum value of the cross-correlation function R(m). max , τ max This refers to the time delay of the feedback baseband signal relative to the reference signal; S603, calculate the phase difference Δϕ=2πfτ max , where f is the baseband signal frequency; the feedback baseband signal x2(n) is phase-shifted based on the phase difference Δϕ to obtain the phase-aligned signal y(n).

[0010] By adopting the above technical solution, the feedback baseband signal is phase-shifted to obtain a phase-aligned signal. The obtained alignment signal y(n) retains the nonlinear distortion characteristics of the power amplifier while achieving phase alignment with the reference signal x1(n).

[0011] As a preferred embodiment, adjusting the preset predistortion coefficient of the digital predistorter in S700 specifically includes the following steps: S701, the digital predistorter obtains the predistortion prediction signal y^(n|θ) based on the preset predistortion coefficients θ(n); S702, compare the phase alignment signal y(n) with the predistortion prediction signal y^(n|θ), and the prediction error is e(n)=y(n)- y^(n|θ); S703 employs the RPEM algorithm, updating the preset predistortion coefficients based on a recursive update formula, as follows: ; Where K(n) is the Kalman gain.

[0012] By adopting the above technical solution, the preset predistortion coefficient θ(n) can be updated based on the deviation between the phase alignment signal y(n) and the predistortion prediction signal y^(n|θ).

[0013] As a preferred embodiment, the predistortion method also includes S610, which performs calibration compensation on the downlink, specifically including the following steps; S611, injects a known high-frequency calibration signal into the downlink; S612, the downlink downconverts the known high-frequency calibration signal to the calibration baseband signal; S613 compares the calibration baseband signal with the ideal reference signal corresponding to the known high-frequency calibration signal to obtain the distortion characteristics of the downlink; S614 calibrates and compensates the preset predistortion coefficients of the digital predistorter based on the distortion characteristics of the downlink.

[0014] By adopting the above technical solution, the nonlinear distortion characteristics of the downlink are extracted, and the preset predistortion coefficient of the digital predistorter is calibrated and compensated accordingly, so that the interference of downlink distortion characteristics is eliminated when the preset predistortion coefficient is adjusted.

[0015] Preferably, in S614, the specific method for calibrating and compensating the preset predistortion coefficient of the digital predistorter is as follows: an inverse filter is constructed in the digital domain, whose characteristics are opposite to those of the downlink distortion characteristics; after the feedback baseband signal is input into the inverse filter, a correction feedback baseband signal is output; the phase difference between the correction feedback baseband signal and the reference signal is calculated to obtain a phase alignment signal; and the subsequent calibration and compensation of the preset predistortion coefficient is performed based on the phase alignment signal.

[0016] By adopting the above technical solution, an inverse filter is constructed based on the nonlinear distortion characteristics extracted from the downlink. The nonlinear distortion characteristics generated by the downlink are separated from the feedback baseband signal to obtain the correction feedback baseband signal, and the phase alignment signal is obtained accordingly. This can eliminate the influence of nonlinear distortion in the downlink, improve the correlation of the power amplifier nonlinear distortion characteristics in the phase alignment signal, and thus improve the calibration compensation accuracy and reliability of the preset predistortion coefficient.

[0017] Preferably, S610 includes switching control for downlink calibration compensation. If the downlink is occupied, S610 is switched off and no downlink calibration compensation is performed; if the downlink is idle, S610 is switched on and downlink calibration compensation is performed to update the parameters of the inverse filter.

[0018] By adopting the above scheme, the downlink calibration compensation is switched on and off, which avoids the conflict between the generated feedback baseband signal and the downlink calibration compensation, and utilizes the downlink idle time to perform downlink calibration compensation calculation.

[0019] Preferably, the digital predistorter employs a memory polynomial model.

[0020] By adopting the above technical solution, the accuracy and computational efficiency of the digital predistorter can be balanced, effectively realizing the predistortion of the baseband signal.

[0021] Secondly, this application provides a predistortion system for radio frequency power amplifier signals based on feedback transmission compensation, which adopts the following technical solution: It includes a raw baseband signal module, a digital predistorter module, an uplink module, a power amplifier, a coupler, a downlink module, and a delay compensation module; The original baseband signal module sends the original baseband signal to the digital predistorter module; The digital predistortion module includes a predistortion unit and a parameter calibration unit. The predistortion unit performs predistortion modulation on the original baseband signal based on the preset predistortion coefficient provided by the parameter calibration unit and outputs a predistortion signal. The uplink module includes a digital-to-analog converter and an upconversion unit. The predistorted signal is upconverted to a high-frequency analog signal by the uplink module and then input to the power amplifier. The power amplifier outputs a linearized amplified signal to the coupler; The coupler outputs one antenna transmit signal and one feedback signal to the downlink module; The downlink module includes an analog-to-digital conversion unit and a downconversion unit. The feedback signal is downconverted to a feedback baseband signal by the downlink module and then input to the delay compensation module. The delay compensation module extracts the original baseband signal as a reference signal, calculates the phase difference between the feedback baseband signal and the reference signal, and shifts the phase of the feedback baseband signal according to the phase difference to obtain a phase-aligned signal. The parameter calibration unit of the digital predistortion module obtains the predistortion prediction signal by a preset predistortion coefficient, compares the phase alignment signal with the predistortion prediction signal to obtain the prediction error, and adjusts the preset predistortion coefficient based on the prediction error.

[0022] As a preferred option, the predistortion system also includes a downlink calibration compensation module; The downlink calibration compensation module includes a control unit, a signal injection unit, and a calibration compensation unit; The control unit controls the switching of the downlink calibration compensation module; The signal injection unit injects a known high-frequency calibration signal into the downlink module; The calibration compensation unit acquires the calibration baseband signal output by the downlink module and acquires the ideal reference signal corresponding to the known high-frequency calibration signal. The two are compared to obtain the distortion characteristics of the downlink. Based on the distortion characteristics of the downlink, an inverse filter is constructed and the parameters of the inverse filter are adjusted. The feedback baseband signal is input to the inverse filter, and the output is a correction feedback baseband signal; The time delay compensation module calculates the phase difference between the correction feedback baseband signal and the reference signal to obtain a phase alignment signal, and performs subsequent calibration compensation based on the phase alignment signal with a preset pre-distortion coefficient.

[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. This application extracts the original baseband digital signal as a reference signal and performs phase difference calculation and phase shift compensation on it with respect to the down-converted feedback signal. While preserving the distortion characteristics of the feedback signal, it achieves alignment with the reference signal in the time dimension. This can truly reflect the impact of the power amplifier's nonlinear distortion on the output of the pre-distorted baseband signal, making the power amplifier's nonlinear distortion curve converge. This improves the adjustment accuracy of the preset pre-distortion coefficient of the digital predistorter and the adaptive convergence speed, enabling more accurate tracking of power amplifier state changes and achieving linear compensation optimization.

[0024] 2. This application calibrates the downlink of the feedback signal separately by introducing a known test signal, constructing an inverse model of its distortion characteristics (i.e., an inverse filter). This effectively removes the distortion components introduced by the feedback transmission path itself, ensuring that subsequent digital predistorter parameter adjustment is based solely on the difference between the pure power amplifier distortion and the predicted predistortion signal. This eliminates the interference of feedback transmission path errors on the learning of preset predistortion coefficients. This application improves the stability and reliability of the digital predistorter for power amplifier linearization compensation.

[0025] 3. The feedback signal calibration mechanism of this application improves the tolerance to differences in radio frequency signal system components and environmental changes. It can adaptively track and compensate for the drift of radio frequency system characteristics caused by factors such as temperature changes and device aging through periodic calibration, thus ensuring the robustness and adaptability of the radio frequency signal system.

[0026] 4. The technical solution of this application is particularly suitable for broadband, peak-to-average power ratio (PAPR) signals, such as 5G / 6G, massive MIMO and satellite communication scenarios. Its excellent linearization performance provides key support for the system to adopt higher-order modulation methods (such as 1024QAM) and wider signal bandwidth, directly improving spectrum utilization and system capacity. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a method for predistorting radio frequency power amplifier signals based on feedback transmission compensation, according to an embodiment of this application. Figure 2 This is a flowchart illustrating step S600 of a method for predistorting RF power amplifier signals based on feedback transmission compensation, according to an embodiment of this application. Figure 3 This is a flowchart illustrating step S700 of a method for predistorting RF power amplifier signals based on feedback transmission compensation, according to an embodiment of this application. Figure 4 This is a schematic diagram of the process of S610, which is a pre-distortion method for RF power amplifier signals based on feedback transmission compensation in another embodiment of this application, to calibrate and compensate the downlink. Figure 5This is a schematic diagram of the architecture of a radio frequency power amplifier signal predistortion system based on feedback transmission compensation according to an embodiment of this application; Figure 6 This is a schematic diagram of the architecture of an exemplary computer device according to an embodiment of this application. Detailed Implementation

[0028] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of this application.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that in the optional embodiments of this application, the object information and other related data involved require the permission or consent of the object when the embodiments of this application are applied to specific products or technologies, and the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. That is to say, if the embodiments of this application involve data related to the object, it needs to be obtained with the authorization and consent of the object, the authorization and consent of the relevant departments, and in compliance with the relevant laws, regulations, and standards of the country and region. If personal information is involved in the embodiments, the acquisition of all personal information requires the consent of the individual. If sensitive information is involved, the separate consent of the information subject is required, and the embodiments also need to be implemented with the authorization and consent of the object.

[0030] In technical solutions that employ digital predistortion (DPD) on the baseband signal to achieve a linear, undistorted output signal from the power amplifier (PA), the nonlinear characteristics of the PA (such as AM-AM and AM-PM curves) will continuously change. These changes originate from factors including PA operating state drift due to temperature variations and device aging, as well as changes in the PA operating point due to differences in baseband signal characteristics and varying degrees of PA power fallback. Therefore, continuous adaptive parameter calibration of the DPD is necessary to ensure the linearization of the PA output. The main method involves comparing the feedback signal with the predicted signal obtained based on the DPD's preset parameters, identifying the error, and then adjusting the DPD parameters accordingly.

[0031] However, technicians discovered that there are unavoidable physical deviations in time and phase between the data obtained from the feedback channel and the original baseband signal at the transmitting end. These deviations primarily originate from: fixed transmission delays generated during the spatial transmission path and when passing through analog devices such as power amplifiers, attenuators, mixers, couplers, cables, and filters; local oscillator offset and phase noise; and additional nonlinear distortion and noise in the feedback link. These deviations cause the power amplifier characteristic curve of the PA to diverge, and the comparison between the feedback signal and the original baseband signal cannot accurately reflect the linearization effect of the PA's final output signal. This leads to inaccurate parameter adjustment of the DPD, resulting in a deterioration in the transmission performance of the RF signal system.

[0032] This application discloses a method for predistorting RF power amplifier signals based on feedback transmission compensation. The aim is to accurately evaluate the true state characteristics of the PA output signal through feedback signals, providing a reliable basis for DPD parameter adjustment. Please refer to... Figure 1 Specifically, it includes the following steps.

[0033] S100: Acquire the raw baseband signal and input it into the digital predistorter.

[0034] S200, the digital predistorter outputs a predistorted signal to the uplink based on a preset predistortion coefficient.

[0035] In the embodiments of this application, the digital predistorter uses a memory polynomial model to predistort the original baseband signal in the digital domain, as shown in the following equation: ; Where x(n) is the original baseband signal at the nth time point; z(n) is the predistortion signal output by the digital predistorter; P is the nonlinear order of the model, used to capture amplitude distortion; M is the memory depth of the model, reflecting the influence of historical signals on the current output; θ is the predistortion coefficient, which is obtained through adaptive algorithm training and is also the target of the predistortion coefficient adjustment of DPD by feedback signal in this application.

[0036] For each time-delayed signal x(nm), calculate the different powers of its amplitude |x(nm)|. p-1 This is then multiplied by the source signal, generating multiple basis functions containing nonlinear characteristics. All basis functions are then based on their corresponding predistortion coefficients θ. n The weighted summation is performed to generate a predistorted signal z(n). After the signal is amplified by the power amplifier, its distortion will cancel out the distortion of the power amplifier itself.

[0037] S300, the uplink upconverts the predistorted signal and performs digital-to-analog conversion to obtain a high-frequency analog signal, which is then input to the power amplifier.

[0038] S400, the power amplifier outputs a linearized amplified signal to the coupler.

[0039] The S500 coupler outputs one antenna transmit signal and one feedback signal to the downlink.

[0040] Among them, the antenna signal is the external transmission signal that realizes baseband signal power amplification and linearization output based on DPD; the feedback signal is the signal used to realize DPD predistortion coefficient adjustment.

[0041] In the S600, the downlink performs analog-to-digital conversion and down-conversion on the feedback signal to obtain the feedback baseband signal. Then, the original baseband signal is extracted as a reference signal. The phase difference between the feedback baseband signal and the reference signal is calculated, and the phase-aligned signal is obtained by phase shifting the feedback baseband signal according to the phase difference.

[0042] It should be noted that the feedback baseband signal is phase-shifted to obtain a phase-aligned signal. This phase-aligned signal eliminates the time delay in the transmission path of the feedback baseband signal, ensuring the accuracy of subsequent comparisons with the predistortion prediction signal. The phase-aligned signal itself retains all the linearized and nonlinear characteristics of the linearized amplified signal.

[0043] For more details, please see Figure 2 In the embodiments of this application, the cross-correlation method is used to align the feedback baseband signal with the reference signal, specifically including the following steps.

[0044] S601 preprocesses the reference signal x1(n) and the feedback baseband signal x2(n) by using a bandpass filter to remove noise and DC components outside the signal passband.

[0045] S602, the cross-correlation function R(m) of the reference signal x1(n) and the feedback baseband signal x2(n) is calculated as follows: ; Where t represents the sampling time of the reference signal x1(n) and the feedback baseband signal x2(n), ∗ denotes conjugate, and m is the time offset. The cross-correlation function R(m) characterizes the similarity between the reference signal x1(n) and the feedback baseband signal x2(n) under different relative delays m. The maximum value of the cross-correlation function R(m) is calculated as m=τ. max , τ max This refers to the time delay of the feedback baseband signal relative to the reference signal.

[0046] S603, calculate the phase difference Δϕ=2πfτ max Where f is the baseband signal frequency. The feedback baseband signal x2(n) is phase-shifted based on the phase difference Δϕ to obtain the phase-aligned signal y(n).

[0047] When the phase-aligned signal y(n) is compared with the predistortion prediction signal obtained based on the original baseband signal and the preset predistortion coefficient, the systematic time delay effect of the feedback signal is eliminated.

[0048] S700 compares the phase alignment signal with the predistortion prediction signal obtained by the digital predistorter based on the preset predistortion coefficient to obtain the prediction error, and adjusts the preset predistortion coefficient of the digital predistorter based on the prediction error.

[0049] For details, please refer to Figure 3 Adjusting the preset predistortion coefficients of the digital predistorter specifically includes the following steps: S701, the digital predistorter obtains the predistortion prediction signal y^(n|θ) based on the preset predistortion coefficients θ(n); S702, compare the phase alignment signal y(n) with the predistortion prediction signal y^(n|θ), and the prediction error is e(n)=y(n)- y^(n|θ); S703 employs the RPEM algorithm, updating the preset predistortion coefficients based on a recursive update formula, as follows: ; Wherein, K(n) is the Kalman gain, which determines the weight of the influence of the prediction error e(n) at the current moment on the parameter update direction, and intelligently balances the model prediction value and the feedback signal measurement value.

[0050] At the next step, a memory polynomial model with updated preset predistortion coefficients θ is used to output the predistorted signal.

[0051] The above technical solution enables the feedback signal to retain its distortion characteristics while achieving phase alignment with the reference signal in the time dimension. This allows it to accurately reflect the impact of the PA's nonlinear distortion on the output of the predistorted baseband signal, as well as the deviation from the DPD's predicted predistorted signal, thereby improving the accuracy and reliability of the DPD's predistortion coefficient adjustment.

[0052] However, in the above scheme, the feedback signal is down-converted to the feedback baseband signal via the downlink, introducing additional distortions, including amplitude imbalance of the downconverter (inconsistent gains between I and Q channels), phase non-orthogonality, inconsistent gain and delay of the filter for different frequency components within its passband, quantization noise of the analog-to-digital converter itself, and nonlinear distortion. These distortions are not caused by the PA and are not within the scope of DPD predistortion modulation, but they appear in the feedback signal used for DPD predistortion coefficient control, contaminating the DPD feedback control and affecting the control effect of the DPD predistortion coefficient. Therefore, it is necessary to remove and suppress the nonlinear distortion generated by the downlink.

[0053] Please see Figure 4 Another embodiment of this application provides a method for predistorting RF power amplifier signals based on feedback transmission compensation, which further includes step S610, performing downlink calibration compensation. This step is performed in parallel with step S600. Specifically, it includes the following steps.

[0054] S611, injects a known high-frequency calibration signal into the downlink.

[0055] The high-frequency calibration signal can be injected through a separate vector signal generator. An RF switch is placed at the start of the downlink (after the coupler) to control the switching of downlink calibration compensation. If the downlink is occupied, S610 is switched off, and no downlink calibration compensation is performed; if the downlink is idle, S610 is switched on, and downlink calibration compensation is performed, updating the parameters of the inverse filter. In some specific implementations, a preset minimum frequency can be set for downlink calibration compensation to avoid excessively frequent parameter calibration, which could affect the stability of the DPD distortion coefficient.

[0056] S612, the downlink downconverts the known high-frequency calibration signal to a calibration baseband signal. This process is equivalent to allowing the high-frequency calibration signal to pass through the entire downlink process, which is consistent with the process of downconverting the feedback signal to the feedback baseband signal.

[0057] S613 compares the calibration baseband signal with the ideal reference signal corresponding to the known high-frequency calibration signal to obtain the distortion characteristics of the downlink.

[0058] The ideal reference signal is a digital baseband signal that is mathematically identical to the injected high-frequency test signal and has no distortion. In practice, while generating the high-frequency test signal, the vector signal generator produces a digital waveform (I / Q data) from its digital baseband section, which is then used to generate an RF signal via an internal high-precision DAC and up-conversion link. The currently used baseband I / Q data can be synchronously read from the signal generator's internal memory or digital port via control interfaces such as GPIB, LAN, or PCIe, thus directly obtaining the ideal reference signal. This reference signal is perfectly time-aligned with the output RF signal, contains no distortion from analog links, and introduces no additional noise.

[0059] S614 calibrates and compensates the preset predistortion coefficients of the digital predistorter based on the downlink distortion characteristics. Specifically, it constructs an inverse filter in the digital domain, whose characteristics are opposite to those of the downlink distortion.

[0060] After the S600 outputs the feedback baseband signal, this feedback baseband signal is input to the inverse filter, which outputs a corrected feedback baseband signal. This signal filters out the nonlinear distortion generated by the downlink. Then, the phase difference between the corrected feedback baseband signal and the reference signal is calculated to obtain a phase-aligned signal. Subsequent calibration and compensation using preset pre-distortion coefficients are then performed based on this phase-aligned signal. Thus, the effects of nonlinear distortion from the downlink are eliminated and removed from the phase-aligned signal.

[0061] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0062] Please see Figure 5 An embodiment of this application provides a radio frequency power amplifier signal predistortion system based on feedback transmission compensation, comprising an original baseband signal module 1, a digital predistorter module 2, an uplink module 3, a power amplifier 4, a coupler 5, a downlink module 6, a delay compensation module 7, and a downlink calibration compensation module 8.

[0063] The raw baseband signal module 1 sends the raw baseband signal to the digital predistorter module 2.

[0064] The digital predistortion module 2 includes a predistortion unit 21 and a parameter calibration unit 22. The predistortion unit 21 performs predistortion modulation on the original baseband signal based on the preset predistortion coefficients provided by the parameter calibration unit 22 and outputs a predistortion signal.

[0065] The uplink module 3 includes a digital-to-analog converter and an upconversion unit. The predistorted signal is upconverted to a high-frequency analog signal by the uplink module and then input to the power amplifier 4.

[0066] The power amplifier 4 outputs a linearized amplified signal to the coupler 5.

[0067] Coupler 5 outputs one antenna transmit signal 51 and one feedback signal to downlink module 6.

[0068] The downlink module 6 includes an analog-to-digital conversion unit and a downconversion unit. The feedback signal is downconverted to a feedback baseband signal through the downlink module.

[0069] The downlink calibration compensation module 8 includes a control unit 81, a signal injection unit 82, and a calibration compensation unit 83.

[0070] The control unit 81 controls the switching of the downlink calibration compensation module 8.

[0071] Signal injection unit 82 injects a known high-frequency calibration signal into downlink module 6.

[0072] The calibration compensation unit 83 acquires the calibration baseband signal output by the downlink module 6 and acquires the ideal reference signal corresponding to the known high-frequency calibration signal. It compares the two to obtain the distortion characteristics of the downlink and constructs an inverse filter 84 based on the distortion characteristics of the downlink, and adjusts the parameters of the inverse filter.

[0073] The feedback baseband signal is input to the inverse filter 84, and the output correction feedback baseband signal is sent to the time delay compensation module 7.

[0074] The delay compensation module 7 extracts the original baseband signal from the original baseband signal module 1 as a reference signal, calculates the phase difference between the correction feedback baseband signal and the reference signal, and shifts the phase of the feedback baseband signal according to the phase difference to obtain a phase-aligned signal.

[0075] The parameter calibration unit 22 of the digital predistortion module 2 obtains the predistortion prediction signal through the preset predistortion coefficient, compares the phase alignment signal with the predistortion prediction signal to obtain the prediction error, and adjusts the preset predistortion coefficient based on the prediction error.

[0076] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the RF power amplifier signal predistortion system based on feedback transmission compensation described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0077] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0078] In one embodiment, a computer device is provided, the internal structure of which can be shown in the following diagram. Figure 6 As shown, the computer device includes a processor, memory, network interface, and database connected via a system bus. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores the memory polynomial model of the digital predistorter, predistortion coefficients, and the predistortion coefficient adaptive algorithm RPEM. The network interface connects and communicates with external RF control links and uplink / downlink transmission links. When executed by the processor, the computer program implements a RF power amplifier signal predistortion method based on feedback transmission compensation.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for predistorting RF power amplifier signals based on feedback transmission compensation, characterized in that, Includes the following steps; S100: Acquire the raw baseband signal and input it into the digital predistorter; S200, the digital predistorter outputs a predistorted signal to the uplink based on a preset predistortion coefficient; S300, the uplink upconverts the predistorted signal to a high-frequency analog signal input to the power amplifier; S400, the power amplifier outputs a linearized amplified signal to the coupler; The S500 coupler outputs one antenna transmit signal and one feedback signal to the downlink; In S600, the downlink downconverts the feedback signal to the feedback baseband signal, then extracts the original baseband signal as the reference signal, calculates the phase difference between the feedback baseband signal and the reference signal, and shifts the phase of the feedback baseband signal according to the phase difference to obtain the phase-aligned signal. S700 compares the phase alignment signal with the predistortion prediction signal obtained by the digital predistorter based on the preset predistortion coefficient to obtain the prediction error, and adjusts the preset predistortion coefficient of the digital predistorter based on the prediction error.

2. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 1, characterized in that, In S600, the phase-shifting of the feedback baseband signal to obtain the phase-aligned signal specifically includes the following steps: S601 preprocesses the reference signal x1(n) and the feedback baseband signal x2(n) by using a bandpass filter to remove noise and DC components outside the signal passband; S602, the cross-correlation function R(m) of the reference signal x1(n) and the feedback baseband signal x2(n) is calculated as follows: ； Where t represents the sampling time of the reference signal x1(n) and the feedback baseband signal x2(n), ∗ indicates taking the conjugate, and m is the time offset; the cross-correlation function R(m) characterizes the similarity between the reference signal x1(n) and the feedback baseband signal x2(n) under different relative delays m, and m=τ is used to calculate the maximum value of the cross-correlation function R(m). max , τ max This refers to the time delay of the feedback baseband signal relative to the reference signal; S603, calculate the phase difference Δϕ=2πfτ max , where f is the baseband signal frequency; the feedback baseband signal x2(n) is phase-shifted based on the phase difference Δϕ to obtain the phase-aligned signal y(n).

3. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 2, characterized in that, In S700, adjusting the preset predistortion coefficient of the digital predistorter specifically includes the following steps: S701, the digital predistorter obtains the predistortion prediction signal y^(n|θ) based on the preset predistortion coefficients θ(n); S702, compare the phase alignment signal y(n) with the predistortion prediction signal y^(n|θ), and the prediction error is e(n)=y(n)- y^(n|θ); S703 employs the RPEM algorithm, updating the preset predistortion coefficients based on a recursive update formula, as follows: ； Where K(n) is the Kalman gain.

4. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 1, characterized in that, It also includes the S610, which performs downlink calibration and compensation, specifically including the following steps; S611, injects a known high-frequency calibration signal into the downlink; S612, the downlink downconverts the known high-frequency calibration signal to the calibration baseband signal; S613 compares the calibration baseband signal with the ideal reference signal corresponding to the known high-frequency calibration signal to obtain the distortion characteristics of the downlink; S614 calibrates and compensates the preset predistortion coefficients of the digital predistorter based on the distortion characteristics of the downlink.

5. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 4, characterized in that, In S614, the specific method for calibrating and compensating the preset predistortion coefficients of the digital predistorter is as follows: an inverse filter is constructed in the digital domain, whose characteristics are opposite to those of the downlink distortion characteristics; after the feedback baseband signal is input into the inverse filter, a correction feedback baseband signal is output; the phase difference between the correction feedback baseband signal and the reference signal is calculated to obtain a phase alignment signal; and the subsequent calibration and compensation of the preset predistortion coefficients is performed based on the phase alignment signal.

6. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 5, characterized in that, S610 includes switching control for downlink calibration compensation. If the downlink is occupied, S610 is switched off and downlink calibration compensation is not performed. If the downlink is idle, S610 is switched on and downlink calibration compensation is performed, updating the parameters of the inverse filter.

7. The method for predistorting RF power amplifier signals based on feedback transmission compensation according to claim 1, characterized in that, The digital predistorter employs a memory polynomial model.

8. A predistortion system for radio frequency power amplifier signals based on feedback transmission compensation, characterized in that, It includes a raw baseband signal module, a digital predistorter module, an uplink module, a power amplifier, a coupler, a downlink module, and a delay compensation module; The original baseband signal module sends the original baseband signal to the digital predistorter module; The digital predistortion module includes a predistortion unit and a parameter calibration unit. The predistortion unit performs predistortion modulation on the original baseband signal based on the preset predistortion coefficient provided by the parameter calibration unit and outputs a predistortion signal. The uplink module includes a digital-to-analog converter and an upconversion unit. The predistorted signal is upconverted to a high-frequency analog signal by the uplink module and then input to the power amplifier. The power amplifier outputs a linearized amplified signal to the coupler; The coupler outputs one antenna transmit signal and one feedback signal to the downlink module; The downlink module includes an analog-to-digital conversion unit and a downconversion unit. The feedback signal is downconverted to a feedback baseband signal by the downlink module and then input to the delay compensation module. The delay compensation module extracts the original baseband signal as a reference signal, calculates the phase difference between the feedback baseband signal and the reference signal, and shifts the phase of the feedback baseband signal according to the phase difference to obtain a phase-aligned signal. The parameter calibration unit of the digital predistortion module obtains the predistortion prediction signal by a preset predistortion coefficient, compares the phase alignment signal with the predistortion prediction signal to obtain the prediction error, and adjusts the preset predistortion coefficient based on the prediction error.

9. A predistortion system for radio frequency power amplifier signals based on feedback transmission compensation according to claim 8, characterized in that, It also includes a downlink calibration compensation module; The downlink calibration compensation module includes a control unit, a signal injection unit, and a calibration compensation unit; The control unit controls the switching of the downlink calibration compensation module; The signal injection unit injects a known high-frequency calibration signal into the downlink module; The calibration compensation unit acquires the calibration baseband signal output by the downlink module and acquires the ideal reference signal corresponding to the known high-frequency calibration signal. The two are compared to obtain the distortion characteristics of the downlink. Based on the distortion characteristics of the downlink, an inverse filter is constructed and the parameters of the inverse filter are adjusted. The feedback baseband signal is input to the inverse filter, and the output is a correction feedback baseband signal; The time delay compensation module calculates the phase difference between the correction feedback baseband signal and the reference signal to obtain a phase alignment signal, and performs subsequent calibration compensation based on the phase alignment signal with a preset pre-distortion coefficient.

10. A computer program product, characterized in that, The computer program product includes a computer program or instructions that enable the computer program or instructions to perform the steps in the RF power amplifier signal predistortion method based on feedback transmission compensation as described in any one of claims 1 to 7.

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