Channel characteristic simulation method based on pre-distortion reconstruction

Abstract

The invention discloses a channel characteristic simulation method based on pre-distortion reconstruction, which belongs to the field of signal processing, and comprises the following steps: firstly, transmitting a broadband correction signal and collecting a loopback signal, calculating a channel calibration coefficient of a reconstruction device by using a frequency domain equalization algorithm, and normalizing a channel response of the reconstruction device; then collecting or defining the amplitude-frequency characteristics of the to-be-simulated equipment, and generating a corresponding predistortion loading coefficient; and carrying out convolution fusion on the two groups of coefficients to obtain a pre-distortion reconstruction coefficient, carrying out convolution processing on the to-be-transmitted signal, and outputting a signal matched with a target channel characteristic. According to the scheme, pure digital implementation is adopted, software dynamic configuration is supported, repeated frequency sweeping or matrix inversion is not needed, target switching can be completed at the millisecond level, decoupling of self channel distortion and target characteristics is achieved, and the requirements of electronic warfare for high-fidelity and low-delay waveform camouflage are met.

Description

Technical Field

[0001] This invention belongs to the field of signal processing, and particularly relates to a method for simulating channel characteristics based on predistortion reconstruction. Background Technology

[0002] In the field of radio frequency (RF) signal processing, high-power transmit links commonly face the problems of amplifier nonlinearity and uneven frequency response of passive devices, leading to in-band fluctuations, phase nonlinearity, and harmonic distortion in broadband signals. To realistically reproduce enemy RF fingerprints in scenarios such as electronic warfare, equipment testing, or feature recognition, existing solutions generally adopt a "pre-distortion + correction" approach: first, the channel response is obtained through ergonomic step scanning or frequency domain least squares fitting, and then an inverse filter is constructed on the baseband side for distortion compensation. Relevant literature has verified that FPGA-controlled rapid frequency sweep calibration can compress the measurement time across the 2-18 GHz frequency band to tens of milliseconds, and weighted least squares FIR equalization can also significantly suppress inter-channel amplitude and phase errors, providing a basic model for subsequent waveform camouflage.

[0003] However, the aforementioned technologies still rely on a one-way calibration model of "measure first, then compensate," requiring a complete measurement of the channel before running with fixed coefficients. If the simulated target changes or the channel drifts due to temperature or bias, frequency scanning and resolving of the canonical equations are necessary. The computational and storage costs increase linearly with frequency density, making it difficult to meet the low-latency requirements of electronic warfare for instantaneous acquisition and dynamic reconstruction. Furthermore, the non-ideals of the channel are not fully normalized, and the inverse filter residuals are superimposed on the target characteristics, causing a decrease in simulation accuracy. Traditional predistortion parameters are fixed in hardware, making it impossible to quickly load amplitude-frequency fingerprints of different targets via software, lacking flexibility and versatility. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a channel characteristic simulation method based on predistortion reconstruction, comprising: Based on the loopback signal of the transmission channel of the reconstruction device and the original transmission signal, the channel calibration coefficient of the reconstruction device itself is obtained; Based on the channel amplitude-frequency characteristics of the device to be simulated, the predistortion loading coefficient of the device to be simulated is obtained; The channel calibration coefficients and the predistortion loading coefficients are convolved and fused to generate predistortion reconstruction coefficients; The transmitted signal is processed according to the predistortion reconstruction coefficients to generate an output signal that matches the channel characteristics of the device to be simulated.

[0005] Optionally, obtaining the channel calibration coefficient of the reconstruction device itself based on the loopback signal of the transmission channel and the original transmission signal of the reconstruction device includes: Transmit a broadband correction signal and acquire the loopback signal after it has passed through the transmission channel of the reconstruction device; Frequency domain response analysis is performed on the loopback signal and the original transmitted signal to obtain a frequency response estimate; Based on the frequency response estimation, the inverse channel response of the reconstruction device itself is calculated as the channel calibration coefficient.

[0006] Optionally, calculating the inverse channel response of the reconstruction device itself includes: The frequency domain equalization algorithm is used to divide the conjugate value of the frequency response estimate by the sum of the square of its modulus and the regularization factor to obtain the inverse frequency domain response. Perform an inverse Fourier transform on the frequency domain inverse response to obtain the time domain channel calibration coefficients.

[0007] Optionally, obtaining the predistortion loading coefficients of the device to be simulated based on the channel amplitude-frequency characteristics of the device to be simulated includes: Collect or set the transmission signal of the device to be simulated, and extract its amplitude-frequency response characteristics; Based on the amplitude-frequency response characteristics, a user-defined frequency domain distortion characteristic is constructed; The frequency domain distortion characteristics are converted into a time domain impulse response, which is used as the predistortion loading coefficient.

[0008] Optionally, converting the frequency domain distortion characteristics into a time domain impulse response includes: Perform an inverse Fourier transform on the frequency domain distortion characteristics to obtain the initial impulse response; The initial impulse response is windowed to obtain an optimized impulse response, which is used as the predistortion loading coefficient.

[0009] Optionally, the channel calibration coefficients and the predistortion loading coefficients are convolved and fused, including: The channel calibration coefficients and the predistortion loading coefficients are convolved in the time domain to generate unified predistortion reconstruction coefficients. The pre-distortion reconstruction coefficient is used to simultaneously compensate for the channel distortion of the reconstruction device itself and load the target channel characteristics.

[0010] Optionally, the process of processing the transmitted signal according to the predistortion reconstruction coefficients includes: The signal to be transmitted is convolved with the pre-distortion reconstruction coefficients to generate a pre-distorted baseband signal. The baseband signal is output to the subsequent transmission channel to simulate the characteristics of the target channel.

[0011] Optionally, the calculation of the frequency response estimation includes: Perform Fourier transforms on the loopback signal and the original transmitted signal respectively; The frequency response estimate of the channel is obtained by dividing the frequency domain representation of the loopback signal by the frequency domain representation of the original transmitted signal.

[0012] On the other hand, the present invention also provides an electronic device including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0013] On the other hand, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention employs a two-stage digital predistortion architecture: first, self-calibration, then loading target characteristics. It utilizes the loopback signal to calculate its own inverse response in real time, normalizing the reconstruction device channels to ideal linearity. Then, it injects user-defined arbitrary amplitude-frequency fingerprints via temporal convolution, achieving decoupled reconstruction of target characteristics and its own defects. This scheme is entirely software-configurable, eliminating the need for repeated frequency sweeps or matrix inversions. It can complete target switching and coefficient updates within milliseconds, thus solving the problems of insufficient simulation accuracy and slow response caused by channel residuals, parameter fixation, and high computational latency in traditional methods. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating a channel characteristic simulation technique and apparatus based on predistortion reconstruction according to an embodiment of the present invention. Figure 2 This is a flowchart illustrating the calculation of the calibration coefficients for the transmission channel of the reconfiguration device according to an embodiment of the present invention. Figure 3 This is a complete flowchart of the predistortion channel feature loading process according to an embodiment of the present invention; Figure 4 The time-domain waveform and spectrum of the transmission signal for the channel calibration of the reconstruction device in this embodiment of the invention; Figure 5 The time-domain waveform and spectrum of the channel distortion acquisition signal of the reconstruction device according to an embodiment of the present invention are shown. Figure 6 The time-domain waveform and spectrum of the device to be simulated in this embodiment of the invention are shown. Figure 7 The time-domain waveform and spectrum of the final output baseband signal in this embodiment of the invention; Figure 8 The channel calibration response and coefficients in this embodiment of the invention are schematic diagrams illustrating the inverse process of the channel response of the reconstruction device itself. Figure 9 This is a schematic diagram of the predistortion channel response and loading coefficients of the device to be simulated in an embodiment of the present invention; Figure 10 This is a schematic diagram comparing the predistortion loading channel characteristics and the output signal characteristics of an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] Example 1 This embodiment provides a channel characteristic simulation method based on predistortion reconstruction, including: Based on the loopback signal of the transmission channel of the reconstruction device and the original transmission signal, the channel calibration coefficient of the reconstruction device itself is obtained; Based on the channel amplitude-frequency characteristics of the device to be simulated, the predistortion loading coefficient of the device to be simulated is obtained; The channel calibration coefficients and the predistortion loading coefficients are convolved and fused to generate predistortion reconstruction coefficients; The transmitted signal is processed according to the predistortion reconstruction coefficients to generate an output signal that matches the channel characteristics of the device to be simulated.

[0019] This method achieves channel calibration and customizable predistortion loading of the transmitted signal through digital signal processing, including two main processes: calculation of the received signal calibration coefficient and predistortion loading of the transmitted signal.

[0020] As an embodiment of the present invention, the process of calculating the received signal calibration coefficient includes: After the transmission calibration signal is generated by the digital baseband, it enters the channel distortion simulation stage; The channel distortion simulation stage simulates the distortion of the transmitted signal according to the preset distortion spectrum characteristics to obtain the simulated received signal; The calibration calculation process uses the original transmitted signal and the analog received signal, and employs a frequency domain equalization algorithm to calculate the channel calibration coefficients.

[0021] As an embodiment of the present invention, the mathematical relationship of the frequency domain equalization algorithm in the calibration calculation stage is: ; in, For channel time-domain calibration coefficients, For the frequency domain equalizer response, For estimating the frequency response of the transmit channel, For conjugate calculation factors, It is an adaptive regularization factor used to reduce the regularization weight at channel depth fading points.

[0022] As an embodiment of the present invention, the process of pre-distortion loading of the transmitted signal includes: Analyze the amplitude-frequency characteristic data of the channel of the analog device; Calculate the predistortion coefficients of the amplitude-frequency response of the channel of the device to be simulated, as the channel distortion characteristics customized by the user; The final output coefficients are obtained by convolving the channel calibration coefficients and the pre-distortion coefficients of the device to be simulated.

[0023] As an embodiment of the present invention, the pre-distortion processing step includes configurable distortion characteristic generation, the impulse response relationship of which is: ; in, Customize the impulse response of the predistortion filter for the user. User-defined frequency domain distortion characteristics.

[0024] As an embodiment of the present invention, the complete process of channel calibration and pre-distortion processing includes: Input the calibration baseband transmission signal, preset the channel distortion characteristics of the device to be simulated, and set the signal sample to be transmitted; Then, the channel calibration coefficients are calculated, the pre-distortion coefficients of the device to be simulated are calculated, and the two are convolved in the time domain, and the final loading coefficients are awaited. The channel response processing is performed on the signal sample to be transmitted to generate an orthogonal baseband transmission signal for subsequent processing stages.

[0025] This embodiment provides a digital predistortion method for high-precision simulation of target channel distortion characteristics, which has the following advantages: 1. This digital predistortion method first calibrates and normalizes its own digital channel, and then applies externally customizable predistortion parameters to accurately simulate the distortion characteristics of the target transmission channel. This two-step processing method can effectively eliminate the influence of the channel's non-ideality on the simulation accuracy. At the same time, the configurable predistortion parameters can flexibly match the channel characteristics of different targets, thereby achieving high-fidelity simulation of the target waveform. This solves the problems of traditional methods being limited by their own hardware characteristics, resulting in inaccurate simulation distortion, and lacking flexibility to adapt to diverse target waveforms. 2. This method is based on pure digital signal processing technology to calibrate and predistort the channel characteristics. The algorithm can be flexibly configured through software programming without relying on a specific hardware platform, which makes the implementation cost of this method low and easy to port and reuse in different systems. 3. This method organically combines channel calibration and pre-distortion processing. The two work together, with the calibration stage providing a clean reference platform for pre-distortion, while the pre-distortion stage injects target specificity, effectively ensuring the accuracy and adaptability of the simulation results.

[0026] Example 2 like Figure 1 , Figure 2 and Figure 3 As shown, this embodiment provides a channel characteristic simulation method based on predistortion reconstruction, including: This method consists of two main stages: channel calibration and customizable predistortion loading. The principle is as follows: when processing the transmitted signal, the amplitude and phase responses of the digital channel are first normalized through the channel calibration stage to eliminate inherent channel distortion. Then, customizable distortion characteristics are injected through the predistortion stage to simulate the distortion characteristics of the target channel. This method achieves high-fidelity target waveform simulation using pure digital signal processing technology. It effectively balances processing accuracy and flexibility requirements, meeting the need for simulating the distortion characteristics of specific target channels on a general-purpose platform.

[0027] The design process of the digital predistortion method for high-precision simulation of target channel distortion characteristics described in this embodiment mainly includes channel distortion simulation, calibration coefficient calculation, and predistortion characteristic loading configuration, specifically including: Step one is to design a channel distortion simulation process; First, a model of the distortion spectrum characteristics of the design channel is constructed. The channel distortion characteristics include two aspects: amplitude response and phase response. In this embodiment, a frequency domain discrete sampling method is used for modeling. Ideal channel distortion characteristics can be fully described by the amplitude and phase values ​​at frequency points. Let the channel distortion spectral characteristics be... ,in At frequency point , the amplitude response is (Unit: dB), phase response is (Unit: radians); In practical applications, channel distortion characteristics can be obtained through actual measurements or simulated through mathematical models. This embodiment uses the superposition of multiple sinusoidal components to simulate the fluctuation characteristics of the actual channel: ; in, For the amplitude of each sine component, For frequency coefficients, For the initial phase, Sampling frequency To simulate the fluctuation characteristics of an actual channel; Next, the channel distortion impulse response is calculated, converting the frequency domain distortion characteristics into a time domain impulse response, which is achieved through inverse Fourier transform: ; in, It is a time-domain impulse response. Representing the frequency function The exponential form of the phase component.

[0028] Next, windowing is applied to the impulse response to reduce spectral leakage: ; in For window functions, this embodiment uses a Hamming window; Step two involves designing the calibration coefficient calculation process; The first step is to design a frequency domain equalization algorithm. Let the transmitted linear frequency modulated signal be... The received signal after channel distortion is ; Channel response estimation is calculated in the frequency domain: ; Design a Wiener filter-type inverse channel response: ; in, For adaptive regularization factor, The conjugate of the estimated channel response.

[0029] Then, the calibration coefficients for the transmission channel are calculated and output. First, calculate the time-domain channel impulse response: ; Then, the high-frequency components outside the effective bandwidth of the filter channel are calculated: ; in, It is the impulse response of a low-pass filter designed based on the effective bandwidth of the channel; Then comes the channel calibration coefficient extraction: ; In the formula, for The index corresponding to the peak value of the modulus; ; ; In the formula, To extract the starting index, To extract the ending index, The length of the calibration coefficient output.

[0030] Final calibration coefficient output: ; Then comes the design pre-distortion feature loading configuration step; First, users can define the distortion characteristics themselves. This can be achieved through external signal acquisition or by customizing the distortion characteristics of the target channel. It supports multiple distortion characteristic description methods, including frequency point amplitude and phase tables, mathematical model parameters, etc. Next is the predistortion filter generation, which converts the user-defined frequency domain characteristics into a time domain impulse response: ; Then, the impulse response is optimized by windowing and length control.

[0031] The predistortion signal generation process includes: transmission channel calibration processing, and the transmitted signal undergoing calibration filtering. ; in For the calibration coefficient of the transmission channel, In order to transmit signals, The signal after channel calibration; Predistortion signal output ; In the formula The output is a calibrated and pre-distorted transmitted signal.

[0032] Example 3 like Figure 4-10 As shown, this embodiment provides a channel characteristic simulation method based on predistortion reconstruction, including: This embodiment implements and verifies the method based on frequency domain equalization and predistortion processing using the following metrics: (1) Complex sampling frequency of the signal ; (2) The transmitted signal is a linear frequency modulated signal with a pulse width of 100 μs and a bandwidth of 1000 MHz; (3) Simulate the distortion characteristics of the transmission channel and perform calibration processing, calibrating the filter coefficients to order 512; (4) Simulate the channel characteristics of the device to be simulated, and obtain the impulse response, i.e., the predistortion loading coefficient, which is taken as 512th order; (5) The transmitted signal sample can be set to any waveform. For easy comparison, a linear frequency modulated signal with a pulse width of 100μs and a bandwidth of 800 MHz is selected.

[0033] Using this method, this embodiment successfully obtained the channel calibration coefficients and generated the final output signal after customized pre-distortion loading. Figures 4-7 It clearly demonstrates the evolution and key characteristics of the signal throughout the entire processing flow. Figure 4 The time-domain waveform and spectrum of the transmission signal for channel calibration of the reconstruction device of the present invention are shown. The signal has the characteristics of wide bandwidth and linear frequency modulation, which provides an ideal excitation source for subsequent channel characteristic analysis and calibration. Figure 5 The time-domain waveform and spectrum of the channel distortion acquisition signal of the reconstruction device of this invention reflect its own channel distortion characteristics. It can be seen that the analog received signal after transmission through this channel has obvious fluctuations in amplitude, which truly reflects the distortion effect of the non-ideal characteristics of the channel on the signal. Figure 6 The time-domain waveform and spectrum of the device to be simulated in this invention reflect the channel characteristics of the device to be simulated, as well as the channel characteristics of the expected output. This response simulates the specific distortion characteristics of the target channel, providing a configurable basis for subsequent signal spoofing. Figure 7 The final output baseband signal of this invention has a time-domain waveform and spectrum, which will be radiated out through the transmission channel of the reconstruction device.

[0034] Figure 8 The channel calibration response and coefficients of this invention are calculated based on the calibration signal acquired from the loopback and their corresponding frequency domain response. This is the inverse process of the channel response of the reconstruction device itself. The frequency response of the calibration filter is complementary to the channel distortion characteristics, providing an accurate inverse model basis for subsequent signal calibration. Figure 9 The predistortion channel response and loading coefficients of the device to be simulated in this invention are the desired predistortion frequency response and its corresponding time-domain filter coefficients. Figure 10 This is a comparison of the consistency between the predistortion loading channel characteristics and the output signal characteristics of the present invention.

[0035] On the other hand, this embodiment also provides an electronic device, including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0036] On the other hand, this embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0037] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A channel characteristic simulation method based on predistortion reconstruction, characterized in that, include: Based on the loopback signal of the transmission channel of the reconstruction device and the original transmission signal, the channel calibration coefficient of the reconstruction device itself is obtained; Based on the channel amplitude-frequency characteristics of the device to be simulated, the predistortion loading coefficient of the device to be simulated is obtained; The channel calibration coefficients and the predistortion loading coefficients are convolved and fused to generate predistortion reconstruction coefficients; The transmitted signal is processed according to the predistortion reconstruction coefficients to generate an output signal that matches the channel characteristics of the device to be simulated.

2. The method according to claim 1, characterized in that, The step of obtaining the channel calibration coefficient of the reconstruction device itself based on the loopback signal of the transmission channel and the original transmission signal includes: Transmit a broadband correction signal and acquire the loopback signal after it has passed through the transmission channel of the reconstruction device; Frequency domain response analysis is performed on the loopback signal and the original transmitted signal to obtain a frequency response estimate; Based on the frequency response estimation, the inverse channel response of the reconstruction device itself is calculated as the channel calibration coefficient.

3. The method according to claim 2, characterized in that, Calculating the inverse channel response of the reconstruction device itself includes: The frequency domain equalization algorithm is used to divide the conjugate value of the frequency response estimate by the sum of the square of its modulus and the regularization factor to obtain the inverse frequency domain response. Perform an inverse Fourier transform on the frequency domain inverse response to obtain the time domain channel calibration coefficients.

4. The method according to claim 1, characterized in that, The step of obtaining the predistortion loading coefficients of the device to be simulated based on the channel amplitude-frequency characteristics of the device to be simulated includes: Collect or set the transmission signal of the device to be simulated, and extract its amplitude-frequency response characteristics; Based on the amplitude-frequency response characteristics, a user-defined frequency domain distortion characteristic is constructed; The frequency domain distortion characteristics are converted into a time domain impulse response, which is used as the predistortion loading coefficient.

5. The method according to claim 4, characterized in that, Converting the frequency domain distortion characteristics into a time domain impulse response includes: Perform an inverse Fourier transform on the frequency domain distortion characteristics to obtain the initial impulse response; The initial impulse response is windowed to obtain an optimized impulse response, which is used as the predistortion loading coefficient.

6. The method according to claim 1, characterized in that, The channel calibration coefficients and the pre-distortion loading coefficients are convolved and fused, including: The channel calibration coefficients and the predistortion loading coefficients are convolved in the time domain to generate unified predistortion reconstruction coefficients. The pre-distortion reconstruction coefficient is used to simultaneously compensate for the channel distortion of the reconstruction device itself and load the target channel characteristics.

7. The method according to claim 1, characterized in that, The signal to be transmitted is processed according to the predistortion reconstruction coefficients, including: The signal to be transmitted is convolved with the pre-distortion reconstruction coefficients to generate a pre-distorted baseband signal. The baseband signal is output to the subsequent transmission channel to simulate the characteristics of the target channel.

8. The method according to claim 2, characterized in that, The calculation of the frequency response estimation includes: Perform Fourier transforms on the loopback signal and the original transmitted signal respectively; The frequency response estimate of the channel is obtained by dividing the frequency domain representation of the loopback signal by the frequency domain representation of the original transmitted signal.

9. An electronic device comprising a memory, a processor, and a computing program stored in the memory and executable on the processor, characterized in that, When the processor executes the computing program, it implements the method of any one of claims 1-8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1-8.

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