A digital predistortion and dispersion compensation method for frequency hopping communication systems

Abstract

This invention belongs to the field of communication engineering technology and relates to a digital predistortion and dispersion compensation method for frequency hopping communication systems, comprising: generating S mixing signals x s (n), s∈(1,S), the signal x s (n) Input the signal x into the frequency hopping communication system respectively. s (n) The power amplifier forward signal z in a frequency hopping communication system s (n), power amplifier output signal μ s (n) System feedback signal v s (n); based on signal v s (n) and μ s (n) Calculate the group delay residual equalization signal r s (n); will the signal r s (n) and z s (n) Perform time alignment to obtain the time alignment signal r s '(n); based on signal x s (n) and r s (n) Estimate the predistortion coefficients and update them in the digital predistorter to obtain the updated frequency hopping communication system; input the mixing signal into the updated frequency hopping communication system to obtain the output signal with predistortion and dispersion compensation; This invention mathematically models the nonlinear behavior of the power amplifier under the excitation of a broadband signal for fast frequency hopping, and uses a combination of digital predistortion and dispersion compensation to accurately compensate for signal distortion caused by the nonlinearity of the power amplifier, thereby improving signal quality.

Description

Technical Field

[0001] This invention belongs to the field of communication engineering technology, and in particular relates to a digital predistortion and dispersion compensation method for frequency hopping communication systems. Background Technology

[0002] In the field of modern communications, frequency-hopping communication systems are widely used due to their excellent anti-interference capabilities and security. However, the nonlinear characteristics of the power amplifier, a key component in frequency-hopping communication systems, pose numerous challenges to the system.

[0003] Traditional power amplifiers operate within relatively fixed frequency and power ranges, making their design relatively simple. However, in frequency-hopping communication, as frequency hopping progresses, the power amplifier needs to rapidly switch operating states at different frequencies. Due to its nonlinear characteristics, this can lead to spectral regeneration, which not only expands the signal spectrum, encroaches on adjacent channels, and causes adjacent-channel interference, but also induces intermodulation distortion, generating new frequency components that interfere with the original signal. For example, when two or more signals of different frequencies pass through a nonlinear power amplifier, intermodulation products such as sum and difference frequencies are generated. These intermodulation products may fall within the signal's frequency band, resulting in a significant deterioration in signal quality.

[0004] Existing compensation methods, such as analog predistortion, can improve the linearity of power amplifiers to some extent, but they suffer from poor stability, limited accuracy, and difficulty in adapting to rapid frequency changes in frequency-hopping systems. While digital predistortion offers advantages such as high flexibility and ease of implementation, its compensation effect is often unsatisfactory when dealing with wideband frequency-hopping signals in frequency-hopping communication systems. On the one hand, during rapid frequency switching, it is difficult to quickly and accurately obtain the nonlinear characteristics of the power amplifier at each frequency point, resulting in the predistortion parameters not being adjusted in a timely and accurate manner. On the other hand, when processing wideband signals, traditional methods struggle to effectively address the varying degrees of nonlinearity experienced by different frequency components within the signal bandwidth.

[0005] Furthermore, the dispersion problem in frequency-hopping communication systems cannot be ignored. During signal transmission, due to factors such as the frequency selectivity of the transmission medium, group delay distortion occurs, causing signal components of different frequencies to arrive at the receiver at different times, further affecting signal synchronization and quality. Existing dispersion compensation methods are often independent of power amplifier nonlinearity compensation methods, lacking effective collaborative design and failing to comprehensively solve the signal distortion problem in frequency-hopping communication systems.

[0006] In summary, existing digital predistortion methods are difficult to achieve ideal compensation results when dealing with wideband frequency hopping signals. Furthermore, existing dispersion compensation methods are often independent of digital predistortion methods and cannot comprehensively solve the signal distortion problem in frequency hopping communication systems. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a digital predistortion and dispersion compensation method for a frequency-hopping communication system. The frequency-hopping communication system includes a digital predistorter, and the digital predistortion and dispersion compensation method includes:

[0008] S1. Generate S mixing signals x with different carrier frequencies. s Given (n), s∈(1,S), the mixing signals with different carrier frequencies are input into the frequency hopping communication system, and the power amplifier forward signal z of the mixing signals with different carrier frequencies in the frequency hopping communication system is collected. s (n), power amplifier output signal μ s (n) System feedback signal v s (n); where s is the index of the mixing signal;

[0009] S2, based on the system feedback signal v s (n) and power amplifier output signal μ s (n) Calculate the group delay residual equalization signal r s (n);

[0010] S3, equalize the group delay residual signal r s (n) and power amplifier forward signal z s (n) Perform time alignment to obtain the time alignment signal r s '(n);

[0011] S4. Mixing signals x based on different carrier frequencies s (n) and time alignment signal r s (n) Estimate the predistortion coefficients corresponding to different carrier frequencies, update the predistortion coefficients corresponding to different carrier frequencies to the digital predistorter of the frequency hopping communication system, and obtain the updated frequency hopping communication system;

[0012] S5. Obtain the output signal with predistortion and dispersion compensation based on the updated frequency hopping communication system.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. Effective compensation for signal distortion: This invention uses a combination of digital predistortion and dispersion compensation to comprehensively and accurately compensate for signal distortion caused by power amplifier nonlinearity and transmission medium. This allows the signal to maintain good waveform integrity during transmission, reduces signal distortion, and thus improves signal quality.

[0015] 2. Improved Frequency Adaptability: This invention generates mixing signals with different carrier frequencies. Based on the power amplifier forward signal, power amplifier output signal, and system feedback signal in the frequency hopping communication system, it mathematically models the nonlinear behavior of the power amplifier under the excitation of the broadband signal in fast frequency hopping. Based on the modeling results, it calculates the predistortion coefficient of the mixing signal at each carrier frequency, realizing cross-frequency, dynamically changing nonlinear compensation. This approach solves the adaptability problem of traditional methods in frequency changes, ensuring that signals at different frequency points in the frequency hopping communication system can receive effective predistortion processing, further stabilizing signal quality.

[0016] 3. Reduced hardware requirements: The digital predistortion and dispersion compensation method of the present invention reduces the dependence on hardware performance to a certain extent, and can avoid excessively increasing the complexity and cost of hardware devices such as power amplifiers in order to achieve the same signal quality, thereby reducing hardware requirements. Attached Figure Description

[0017] Figure 1 This is a flowchart of the digital predistortion and dispersion compensation method for a frequency hopping communication system provided in this embodiment of the invention;

[0018] Figure 2 This is a system block diagram of the digital predistortion and dispersion compensation method for a frequency hopping communication system provided in this embodiment of the invention;

[0019] Figure 3 This is a block diagram of the group delay residual equalization model of the frequency hopping communication system provided in this embodiment of the invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, this invention employs a digital predistortion and dispersion compensation method for a frequency-hopping communication system. The frequency-hopping communication system includes a digital predistorter, and the digital predistortion and dispersion compensation method includes:

[0022] S1. Generate S mixing signals x with different carrier frequencies. s Given (n), s∈(1,S), the mixing signals with different carrier frequencies are input into the frequency hopping communication system, and the power amplifier forward signal z of the mixing signals with different carrier frequencies in the frequency hopping communication system is collected. s(n), power amplifier output signal μ s (n) System feedback signal v s (n); where s is the index of the mixer signal; the power amplifier forward signal z s (n) and power amplifier output signal μ s (n) represent the signals collected from the input and output signals of the power amplifier in the frequency hopping communication system, respectively, and the system feedback signal v. s (n) represents the signal acquired in the final output signal of the frequency hopping communication system;

[0023] Generating mixed signals with different carrier frequencies includes: generating I-channel baseband signals and Q-channel baseband signals; up-converting the I-channel and Q-channel baseband signals at different frequency points; and combining the up-converted I-channel and Q-channel baseband signals to obtain the mixed signal x1(n)…x S (n); where S is the number of frequency hopping points of the up-conversion, and n is the time variable of the signal.

[0024] Upconverting the I and Q baseband signals separately involves multiplying the I and Q baseband signals with the local oscillator (LO) signal using a mixer; for the I and Q signals, two different LO signals are used respectively, which have the same frequency hopping point but are 90° out of phase (i.e., orthogonal).

[0025] S2, based on the system feedback signal v s (n) and power amplifier output signal μ s (n) Calculate the group delay residual equalization signal r s (n);

[0026] The specific steps include:

[0027] like Figure 3 As shown, a group delay residual equalization model is constructed:

[0028] Where n is the time variable of the signal, and M is the number of tap stages of the filter in the group delay residual equalization model; d s,p and d s,M+p Here are the tap coefficients of the filter in the group delay residual equalization model, used to adjust the weights of different delay paths, where i is the index from 0 to M, T is the unit time offset, and s... 1 / T Represents the Laplace transform;

[0029] The basis function matrix V is calculated using an LTI cascaded network with a fixed time delay interval of 1 / τ based on the system feedback signal; where LTI is linear time invariant and 1 / τ is a time constant.

[0030] τ=B / f s

[0031] Where B is the bandwidth of the acquired signal, f s The system sampling rate;

[0032] The matrix is ​​constructed as follows: r s,N×1 =V s,N×(2M+1) d s,(2M+1)×1 Where N is the length of the signal, d s,(2M+1)×1 It is the coefficient matrix of the group delay residual equalization model, V s,N×(2M+1) It is a basis function matrix generated based on the system feedback signal, and is generated in the following way;

[0033]

[0034] The coefficients of the group delay residual equalization model are calculated based on the basis function matrix V and the power amplifier output signal: d s =(V s H V s ) - 1 V s H u s ; where u s The power amplifier output signal u s (n) The constructed matrix; directly put u s (n) are sorted by time to form a column vector:

[0035]

[0036] The coefficients and system feedback signal are input into the group delay residual equalization model to obtain the group delay residual equalization signal.

[0037] S3, equalize the group delay residual signal r s (n) and power amplifier forward signal z s (n) Perform time alignment to obtain the time alignment signal r s '(n);

[0038] The specific steps include:

[0039] Calculate the group delay residual equalization signal r respectively s (n) and power amplifier forward signal z s The wavelet coefficients W of (n) s,r (j,k) and W s,z (j,k):

[0040]

[0041] ψ j,k (n)=2 j / 2 ψ(2 j nk)

[0042] Where j is the signal r s (n) and z s The scale parameter of (n), where k is the signal r s (n) and z s The translation parameter of (n), ψ j,k (n) is a wavelet function with scale parameter j and translation parameter k. It is ψ j,k The conjugate complex number of (n);

[0043] The scaling parameter typically depends on the scaling order of the wavelet transform used; in one embodiment, the minimum value of the scaling parameter j is... min Typically, j is set to 0, representing the coarsest scale (the scale of the original signal), and the maximum value j is... max satisfy

[0044] Based on wavelet coefficients W x (j,k) and W y Calculate the wavelet domain cross-correlation function (j,k). Where δ is the Kronecker function, n and m are the time variables of the signal, 0≤n≤N-1, 0≤m≤N-1, and are defined as follows:

[0045]

[0046] Calculation makes Variable that reaches its maximum value Calculate the time delay based on variable k0. Based on the time delay Δn s For signal r s (n) is adjusted to obtain the time-aligned signal r'(n).

[0047] S4. Mixing signals x based on different carrier frequencies s (n) and time alignment signal r s (n) Estimate the predistortion coefficients corresponding to different carrier frequencies, update the predistortion coefficients corresponding to different carrier frequencies to the digital predistorter of the frequency hopping communication system, and obtain the updated frequency hopping communication system;

[0048] The input I-channel baseband signal and Q-channel baseband signal are the same set of data in one loop, except that the carrier is a frequency hopping point with subscripts 1-S; then after mixing, x1(n)...x is generated. S (n) Mixed signal; the operator matrix U can be formed through the memory polynomial model (MP model). mp :

[0049]

[0050] Then all the input signals are combined into an operator matrix U, as shown below:

[0051]

[0052] Where, x S (n) is the baseband signal after being mixed at the frequency hopping point S, q represents the memory depth of the MP model, and k represents the nonlinear order of the MP model;

[0053] Construct an output matrix, which is the weighted average of the corresponding values.

[0054] The predistortion coefficients are obtained using the least squares method. Where c = [c1(L)…c1(0)c2(L)…c2(0)…c S (L)…c S (0)] T L is the number of predistortion coefficients.

[0055] S5. Obtain the output signal with predistortion and dispersion compensation based on the updated frequency hopping communication system.

[0056] Specifically, the updated frequency hopping communication system generates a mixing signal, selects the corresponding predistortion coefficients based on the generated mixing signal, and finally outputs a predistortion and dispersion compensated output signal.

[0057] On the other hand, such as Figure 2 As shown, the present invention employs a system based on the above-described digital predistortion and dispersion compensation method for frequency hopping communication systems, comprising:

[0058] The baseband signal frequency hopping processing module is used to generate mixed signals with different carriers;

[0059] Frequency hopping communication systems are used to process mixed signals that generate different carriers; a frequency hopping communication system includes: a digital predistorter;

[0060] The signal acquisition module is used to acquire the power amplifier forward signal, power amplifier output signal and system feedback signal of the frequency hopping communication system through the analog-to-digital converter (ADC).

[0061] The group delay equalization module is used to calculate the group delay residual equalization signal based on the system feedback signal and the power amplifier output signal;

[0062] The wavelet domain time alignment module is used to time align the group delay residual equalization signal and the power amplifier forward signal.

[0063] The DPD coefficient estimation module is used to estimate the predistortion coefficients based on the mixing signals and time alignment signals of different carriers, and update the predistortion coefficients to the digital predistorter of the frequency hopping communication system.

[0064] The frequency hopping communication system includes: a first switch, a second switch, a DPD predistorter, a digital-to-analog converter (DAC), a power amplifier (PA), and a subsequent processing module. The output of the baseband signal frequency hopping processing module is connected to the output of the first switch. The output 1 of the first switch is connected to the input of the DPD predistorter. The output of the DPD predistorter is connected to the input 1 of the second switch. The output 2 of the first switch is connected to the input 2 of the second switch. The output of the second switch is connected to the input of the DAC. The output of the DAC is connected to the input of the PA. The output of the PA is connected to the input of the subsequent processing module.

[0065] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for digital predistortion and dispersion compensation in a frequency-hopping communication system, the frequency-hopping communication system comprising: A digital predistorter, characterized in that the digital predistortion and dispersion compensation methods include: S1. Generate S mixing signals x with different carrier frequencies. s Given (n), s∈(1,S), the mixing signals with different carrier frequencies are input into the frequency hopping communication system, and the power amplifier forward signal z of the mixing signals with different carrier frequencies in the frequency hopping communication system is collected. s (n), power amplifier output signal μ s (n) System feedback signal v s (n); where s is the index of the mixing signal; S2, based on the system feedback signal v s (n) and power amplifier output signal μ s (n) Calculate the group delay residual equalization signal r s (n); S3, equalize the group delay residual signal r s (n) and power amplifier forward signal z s (n) Perform time alignment to obtain the time alignment signal r s ′(n); S4. Mixing signals x based on different carrier frequencies s (n) and time alignment signal r s (n) Estimate the predistortion coefficients corresponding to different carrier frequencies, update the predistortion coefficients corresponding to different carrier frequencies to the digital predistorter of the frequency hopping communication system, and obtain the updated frequency hopping communication system; S5. Obtain the output signal with predistortion and dispersion compensation based on the updated frequency hopping communication system.

2. The digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 1, characterized in that, Generating mixed signals with different carrier frequencies includes: generating I-channel baseband signals and Q-channel baseband signals; up-converting the I-channel and Q-channel baseband signals to different frequencies; and combining the I-channel and Q-channel baseband signals after up-conversion to the same frequency to obtain the mixed signal x1(n)…x S (n); where S is the number of frequency hopping points of the up-conversion, and n is the time variable of the signal.

3. The digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 1, characterized in that, The calculation of the group delay residual equalization signal based on the system feedback signal and the power amplifier output signal includes: constructing a group delay residual equalization model; calculating the basis function matrix using an LTI cascaded network based on the system feedback signal; calculating the coefficients of the group delay residual equalization model based on the basis function matrix and the power amplifier output signal; and inputting the coefficients and the system feedback signal into the group delay residual equalization model to obtain the group delay residual equalization signal r. s (n); where LTI is linear time invariant.

4. The digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 3, characterized in that, Group delay residual equalization models include: Where n is the time variable of the signal, and M is the number of tap stages of the filter in the group delay residual equalization model; d s,p and d s,M+p represents the tap coefficients of the filter in the group delay residual equalization model, where i is the subscript index from 0 to M, and T is the unit offset of time.

5. A digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 3, characterized in that, The coefficients of the group delay residual equalization model, calculated based on the basis function matrix and the power amplifier output signal, include: d s =(V s H V s ) -1 V s H u s Where d is the coefficient matrix of the group delay residual equalization model corresponding to the s-th mixing signal, and u s The power amplifier output signal u s (n) Constructs a matrix, V s Let H be the basis function matrix corresponding to the s-th mixing signal, where the superscript H indicates the conjugate transpose and the superscript -1 indicates the inverse.

6. The digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 1, characterized in that, Time alignment of the group delay residual equalization signal and the power amplifier forward signal includes: calculating the group delay residual equalization signal r respectively. s (n) and power amplifier forward signal z s The wavelet coefficients W of (n) s,r (j,k) and W s,z (j,k), based on wavelet coefficients W s,r (j,k) and W s,z Calculate the wavelet domain cross-correlation function (j,k). Calculation makes The variable k0 reaches its maximum value; the time delay Δn is calculated based on variable k0. s Based on the time delay Δn s For signal r s (n) is adjusted to obtain the time-aligned signal r. s ′(n); where j is the signal r s (n) and z s The scale parameter of (n), where k is the signal r s (n) and z s The translation parameter of (n).

7. A digital predistortion and dispersion compensation method for a frequency-hopping communication system according to claim 6, characterized in that, wavelet cross-correlation function Where δ is the Kronecker function, and n and m are the time variables of the signal.

8. A digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 1, characterized in that, Estimating the predistortion coefficients based on the mixing signals and time-aligned signals of different carrier frequencies includes: constructing an operator matrix U based on the mixing signals of different carrier frequencies, constructing an output matrix based on the time-aligned signal, and estimating the predistortion coefficients based on the output matrix and the operator matrix U.

9. A digital predistortion and dispersion compensation method for a frequency hopping communication system according to claim 1, characterized in that, The output matrix is ​​constructed based on the time-aligned signal, including: in, This is the output matrix.

10. A system employing the digital predistortion and dispersion compensation method for a frequency-hopping communication system as described in any one of claims 1 to 9, characterized in that, include: The baseband signal frequency hopping processing module is used to generate mixed signals with different carrier frequencies; Frequency hopping communication systems are used to process mixed signals that generate different carrier frequencies; Frequency-hopping communication systems include: digital predistorters; The signal acquisition module is used to acquire the power amplifier forward signal, power amplifier output signal, and system feedback signal of the frequency hopping communication system. The group delay equalization module is used to calculate the group delay residual equalization signal based on the system feedback signal and the power amplifier output signal; The wavelet domain time alignment module is used to time align the group delay residual equalization signal and the power amplifier forward signal. The DPD coefficient estimation module is used to estimate the coefficients of digital predistortion (DPD) based on the mixing signal and time alignment signal of different carrier frequencies, and update the digital predistortion coefficients to the digital predistorter of the frequency hopping communication system.

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