Diagonal loading technology loading capacity determination method applied to spread spectrum communication system

Abstract

The invention discloses a diagonal loading technology loading capacity determination method applied to a spread spectrum communication system, which comprises the following steps of: 1, sampling an array signal to obtain a sampling data covariance matrix; 2, different loading factors are loaded on the sampling data covariance matrix according to N gears; 3, solving a weight coefficient used for beam forming; 4, performing spatial filtering on the array signals, and calculating the signal-to-noise ratio of N paths of signals; and 5, comparing the signal-to-noise ratios of the N paths of signals, and taking the loading quantity of the path with the maximum signal-to-noise ratio as the loading quantity of the diagonal loading technology. According to the invention, variable loading factors are adopted, the loading factors are divided into multiple gears, and the loading factors are set according to simulation, so that a relatively good anti-interference effect is ensured when the signal-to-noise ratio of a signal is-20dB to 50dB.

Description

Technical Field

[0001] The invention belongs to the technical field of array signal processing, relates to beamforming technology, and relates to a method for determining a loading amount of a diagonal loading technology applied to a spread spectrum communication system. Background Art

[0002] Array signal processing is an important branch of the signal processing field. It distributes multiple sensors at different locations in space to form a sensor array to receive and process spatially propagated signals. Beamforming is an important direction and content of research in the field of array signal processing. Beamforming performs complex weighted processing based on the complex signals received by each sensor array element, and its output will form different gains for signals in different directions. When there are multiple signal sources or many interfering signals in space, it is necessary to enhance or extract the desired signal and suppress the unnecessary signal, so that a certain gain is formed in the direction of interest and suppression or nulling is formed in other directions. This process is called beamforming.

[0003] In the case of array element position error, amplitude and phase error, and received data containing the expected signal, the beamformer may experience problems such as decreased output signal-to-noise ratio, main lobe offset, increased side lobe level, and signal cancellation. Therefore, it is particularly important to develop a robust adaptive beamforming algorithm. Diagonal loading is such a robust adaptive beamforming algorithm. The diagonal loading algorithm is simple to design and easy to understand. The only difficulty is that there is no guiding literature to explain the determination of the diagonal loading amount.

[0004] Direct sequence spread spectrum communication has certain anti-interception and anti-interference capabilities. The signal is spread over a relatively wide frequency band, that is, the signal power spectrum density is very low, the signal power spectrum is relatively flat, and it is submerged in white noise. However, due to the limited bandwidth of the system, the anti-interference ability of the direct spread spectrum system is limited by the spread spectrum gain and will not be too high. Beamforming technology is usually used to improve the anti-interference ability of the system. Summary of the invention

[0005] (I) Purpose of the invention

[0006] The purpose of the present invention is to propose a method for determining the loading amount of a diagonal loading technology applied to a spread spectrum communication system, and to use the spectrum characteristics of direct spread spectrum communication to assist in determining the loading amount of the diagonal loading technology.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a method for determining a loading amount of a diagonal loading technology applied to a spread spectrum communication system, which comprises the following steps:

[0009] Step 1: Sample the array signal to obtain the covariance matrix of the sampled data;

[0010] Step 2: For the sampling data covariance matrix, load different loading factors according to N levels;

[0011] Step 3: Solve the weight coefficients used for beamforming;

[0012] Step 4: Filter the array signal in the spatial domain and calculate the signal-to-noise ratio of the N-channel signal;

[0013] Step 5: Compare the signal-to-noise ratios of the N channels, and use the loading amount of the channel with the largest signal-to-noise ratio as the loading amount of the diagonal loading technology.

[0014] In step 2, different loading factors γi are loaded into the covariance matrix of the sampled data according to N levels, where i=1, 2, ..., N.

[0015] In step 2, the loading factor is divided into multiple levels and is set to γ ​​according to experience. 1 =σ n , γ 2 =1e1*σ n , γ 3 =1e2*σ n , γ 4 =1e3*σ n , γ 5 =1e4*σ n , ..., γ n =le(N-1)*σ n ; σ n is the array signal noise power.

[0016] In step 3, use the formula Obtain the weight coefficient W used for beamforming 1 , W 2 , W 3 , W 4 , W 5 , ..., W n ; The sampling covariance matrix is ​​represented by R, and the steering vector is represented by τ SP Represented by , the identity matrix is ​​represented by I.

[0017] In step 4, the array signal is spatially filtered to obtain N group signals, and the N group signals are despread and then subjected to fft spectrum analysis to obtain the peak value P and the noise power N, respectively, and calculate the signal-to-noise ratio P / N of the N group signals.

[0018] In step 5, the signal-to-noise ratios of the N combined signals are compared, and the weight coefficient of the path with the largest signal-to-noise ratio is used as the final weight coefficient for beamforming. The loading amount γ*I of the path with the largest signal-to-noise ratio is the loading amount of the diagonal loading technology.

[0019] (III) Beneficial effects

[0020] The above technical solution provides a method for determining the loading amount of diagonal loading technology applied to spread spectrum communication systems. The loading factor is divided into multiple levels and the loading factor is set according to simulation to ensure a better anti-interference effect when the signal-to-noise ratio is -20dB to 50dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of a process for obtaining digital multi-channel beamforming weight coefficients in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0023] In the process of determining the loading amount of diagonal loading technology, the loading factor γ is usually 10σ n , where σ n is the noise power, using the formula The weight coefficient W for beamforming is obtained, where the sampling covariance matrix is ​​represented by R and the steering vector is represented by τ SP Represented by , the identity matrix is ​​represented by I.

[0024] For signals with a large dynamic range, a fixed loading factor γ will result in the modulus of the weight vector being too large when the selected loading value is too small, and the robustness of the system cannot be guaranteed; when the loading value is too large, the system will lose its adaptability and the ability to suppress interference signals.

[0025] Therefore, the present invention adopts a variable loading factor, which is divided into multiple levels and is set to γ ​​according to experience. 1 =σ n , γ 2 =1e1*σ n , γ 3 =1e2*σ n , γ 4 =1e3*σ n , γ 5 =1e4*σ n The loading factor is set according to the simulation to ensure a better anti-interference effect when the signal-to-noise ratio is -20dB to 50dB.

[0026] The process of the method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system in this embodiment is as follows:

[0027] Step 1: Sample the array signal to obtain the covariance matrix of the sampled data;

[0028] Step 2: Load different loading factors γi, i = 1, 2, ..., N, to the sampling data covariance matrix according to N levels;

[0029] The loading factor is divided into multiple levels and is set to γ ​​according to experience. 1 =σ n , γ 2 =1e1*σ n , γ 3 =1e2*σ n , γ 4 =1e3*σ n , γ 5 =1e4*σ n , ..., γ n =le(N-1)*σ n ; σ n is the array signal noise power;

[0030] Step 3: Use the formula Obtain the weight coefficient W used for beamforming 1 , W 2 , W 3 , W 4 , W 5 , ..., W n ; The sampling covariance matrix is ​​represented by R, and the steering vector is represented by τ SP Indicates that the unit matrix is ​​represented by I;

[0031] Step 4: Filter the array signal in the spatial domain to obtain N group signals, perform FFT spectrum analysis on the N group signals after despreading, calculate the peak value P and noise power N respectively, and calculate the signal-to-noise ratio P / N of the N group signals;

[0032] Step 5: Compare the signal-to-noise ratios of the N combined signals. The weight coefficient of the path with the largest signal-to-noise ratio is used as the final weight coefficient for beamforming. The loading amount γ*I of the path with the largest signal-to-noise ratio is the loading amount of the diagonal loading technology.

[0033] Example

[0034] Reference Figure 1 As shown, for the sampling data covariance matrix, different loading factors γ are loaded in 5 levels respectively. 1 =σ n , γ 2 =1e1*σ n , γ 3 =1e2*σ n , γ 4 =1e3*σ n , γ 5 =1e4*σ n , σ nis the array signal noise power, using the formula Obtain the weight coefficient W used for beamforming 1 , W 2 , W 3 , W 4 , W 5 Then, the array signal is spatially filtered to obtain 5 groups of signals. After despreading the 5 groups of signals, the FFT spectrum analysis is performed to obtain the peak value P and the noise power N respectively, and the signal-to-noise ratio P / N of the 5 signals is calculated. The signal-to-noise ratio of the 5 combined signals is compared, and the weight coefficient of the path with the largest signal-to-noise ratio is the weight coefficient used for beamforming in the end, and the loading amount γ*I of this path is the loading amount of the diagonal loading technology.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the loading amount of diagonal loading technology applied to a spread spectrum communication system, characterized in that: The following steps are involved: Step 1: Sample the array signal to obtain the covariance matrix of the sampled data; Step 2: For the sampling data covariance matrix, load different loading factors according to N levels; Step 3: Solve the weight coefficients used for beamforming; Step 4: Filter the array signal in the spatial domain and calculate the signal-to-noise ratio of the N-channel signal; Step 5: Compare the signal-to-noise ratios of the N channels, and use the loading amount of the channel with the largest signal-to-noise ratio as the loading amount of the diagonal loading technology.

2. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 1, characterized in that: In step 2, different loading factors γi are loaded into the covariance matrix of the sampled data according to N levels, where i=1, 2, ..., N.

3. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 2, characterized in that: In step 2, the loading factor is divided into multiple levels, and is set to γ1 = σ according to experience. n ,γ2=1e1*σ n ,γ3=1e2*σ n ,γ4=1e3*σ n ,γ5=1e4*σ n , ..., γ n =le(N-1)*σ n ; σ n is the array signal noise power.

4. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 3, characterized in that: In step 3, use the formula Obtain the weight coefficients W1, W2, W3, W4, W5, ..., W used for beamforming n ; The sampling covariance matrix is ​​represented by R, and the steering vector is represented by τ SP Represented by , the identity matrix is ​​represented by I.

5. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 4, characterized in that: In step 4, the array signal is spatially filtered to obtain N group signals, and the N group signals are despread and then subjected to fft spectrum analysis to obtain the peak value P and the noise power N, respectively, and calculate the signal-to-noise ratio P / N of the N group signals.

6. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 5, characterized in that: In step 5, the signal-to-noise ratios of the N combined signals are compared, and the weight coefficient of the path with the largest signal-to-noise ratio is used as the final weight coefficient for beamforming. The loading amount γ*I of the path with the largest signal-to-noise ratio is the loading amount of the diagonal loading technology.

7. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 6, characterized in that: In step 2, the sampling data covariance matrix is ​​loaded with different loading factors γ1=σ in 5 levels. n ,γ2=1e1*σ n ,γ3=1e2*σ n ,γ4=1e3*σ n ,γ5=1e4*σ n , σ n is the array signal noise power.

8. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 7, characterized in that: In step 3, use the formula Obtain the weight coefficients W1, W2, W3, W4, and W5 used for beamforming.

9. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 8, characterized in that: In step 4, the array signal is spatially filtered to obtain 5 sets of path signals, and the 5 sets of path signals are despread and then subjected to FFT spectrum analysis to obtain the peak value P and the noise power N, respectively, and calculate the signal-to-noise ratio P / N of the 5 path signals.

10. The method for determining the loading amount of the diagonal loading technology applied to the spread spectrum communication system according to claim 9, characterized in that: In step 5, the signal-to-noise ratios of the five combined signals are compared, and the weight coefficient of the path with the largest signal-to-noise ratio is the weight coefficient ultimately used for beamforming, and the loading amount γ*I of this path is the loading amount of the diagonal loading technology.

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