A method for spatial separation of co-frequency signals

Abstract

The application discloses a method for separating same-frequency signals in space, which comprises the following steps: S1, acquiring the elevation angle and azimuth angle of a satellite; S2, calculating a guide vector of a satellite signal coming direction; S3, injecting an interference signal into other satellite coming directions except the satellite signal coming direction to be pointed, so as to obtain a new input signal X'; S4, applying an adaptive beam forming algorithm to the new input signal to obtain a synthesized directivity pattern which forms a pointing gain in the signal coming direction to be separated and forms a "null" in other signal coming directions, so as to separate the same-frequency signals; the application solves the problems of a complex system, large volume and high cost caused by the traditional method for separating same-frequency signals in space by using multiple directional antennas; the application avoids the problem of high calculation complexity of the array signal processing method using a multi-linear constraint, greatly shortens the calculation time, and can be realized by simply modifying the traditional anti-suppression interference algorithm, and is convenient and easy to implement.

Description

Technical Field

[0001] This invention relates to the field of space signal processing technology, and in particular to a method for spatial separation of signals with the same frequency. Background Technology

[0002] In complex electromagnetic environments, it is sometimes necessary to separate signals from different directions in space, even though these signals may have the same frequency. For example, in a global satellite navigation system, multiple satellites transmit signals at the same frequency. It is necessary to set the delay and Doppler offset for the signals transmitted by each satellite to obtain the navigation signal for the target point. This requires spatial separation of the received signals of the same frequency.

[0003] There are two main methods for spatial separation of co-frequency signals in the existing technology. The first method uses multiple directional antennas, such as parabolic antennas or array antennas, and adjusts the antenna attitude to align the main beam of the antenna with the satellite to be separated. The second method uses a multi-linearly constrained array signal processing method to make the array antenna form a beam pointing to the satellite to be separated, while simultaneously creating nulls in the direction of other satellite signals. However, the first method requires a large number of directional antennas, resulting in a complex, large, and costly system. Although the second method significantly reduces system complexity, it has high computational complexity and long computation time, making it difficult to develop into an engineered product. These shortcomings are problems that urgently need to be solved by those skilled in the art.

[0004] Chinese patent (publication number CN109425875A) discloses a satellite signal separation and processing device and method. The patent includes an antenna array and a processor. The antenna array includes multiple array elements. The processor adjusts the shape of the composite radiation pattern of the multiple array elements to form a directional gain in the direction of arrival of the satellite signal to be separated, while attenuating it in the direction of arrival of other satellite signals, thereby separating the satellite signal to be separated. This patent is also used for satellite signal separation and processing, but the method it uses is a multi-linear constraint array signal processing method, which has high computational complexity, long computation time, and is difficult to apply in engineering. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention discloses a spatial separation method for signals of the same frequency;

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A spatial separation method for co-frequency signals, which receives co-frequency satellite signals from different directions in space via an M-element array antenna, includes the following steps:

[0008] S1. Obtain the satellite's elevation and azimuth angles;

[0009] S2. Calculate the steering vector of the satellite signal's direction of arrival;

[0010] S3. Inject interference signals from satellites other than the one to be targeted, to obtain a new input signal X'; Suppose there are L satellite signals s from different directions. i (t), whose direction of arrival is θ. i i = 1, ..., L, θ i The desired direction of arrival of the signal is θ. d , where a(θ) is the steering vector of the satellite signal with a direction of arrival of θ, the interference injected into the array received signal can be expressed as:

[0011]

[0012] J i (t) represents the direction of arrival θ. i Interference signals injected in the direction of the signal;

[0013] S4. Apply an adaptive beamforming algorithm to the new input signal to obtain a composite beam pattern that forms a directional gain in the direction of the signal to be separated and a null in the direction of other signals, thereby separating signals of the same frequency; calculate the optimal weights based on the adaptive beamforming algorithm:

[0014]

[0015] Where R is the covariance matrix of the input signal x(t) after the injection of interference, and a(θ) d ) is the guiding vector of the array in the direction of the signal to be separated, and its weighted output is: y(t) = w H x(t) is the obtained separated signal.

[0016] Preferably, for an array antenna with M elements, a maximum of M-1 co-frequency signals can be separated simultaneously, and the number of array elements is not less than the number of co-frequency signals to be separated.

[0017] Preferably, the interference signal injected in step S3 can be one or more combinations of broadband interference, narrowband interference, frequency sweep interference, pulse interference, or continuous wave interference.

[0018] Preferably, in step S3, the interference injected into the signal direction is set to be of the same type and the same magnitude.

[0019] Preferably, in step S4, the depth of the "zero trap" pointing to the direction of the satellite other than the satellite to be separated is not less than 30dB.

[0020] Preferably, an M*N rectangular planar array antenna is used. In step S2, when calculating the steering vector of the satellite signal's direction of arrival, the spacing between adjacent antennas is d, the elevation angle of the space signal is θ, and the azimuth angle is φ. Its steering vector... The distance difference in the X direction is dcosθcosφ, and the phase difference is 2π / λdcosθcosφ; the distance difference in the Y direction is dcosθsinφ, and the phase difference is 2π / λdcosθsinφ; then we have:

[0021]

[0022]

[0023] Usually, d = λ / 2 is taken, then:

[0024] a x =[1,e jπcos(θ)cos(φ) , ..., e jπ(M-1)cos(θ)cos(φ) ] T

[0025] a y =[1,e jπcos(θ)sin(φ) , ..., e jπ(N-1)cos(θ)sin(φ) ] T

[0026] calculate This gives us the steering vector of the signal coming from the pitch angle θ and the azimuth angle φ.

[0027] By employing the technical solution described above, the present invention has the following beneficial effects:

[0028] This invention discloses a spatial separation method for co-frequency signals, which can be used in satellite navigation systems to separate satellite signals from different directions, and can also be used in other wireless communication systems. As long as the direction of the signal can be obtained, spatial separation of co-frequency signals can be achieved. It solves the problems of system complexity, large size, and high cost caused by the use of multiple directional antennas in traditional co-frequency signal spatial separation methods. It avoids the problem of high computational complexity of array signal processing methods with multi-linear constraints, significantly shortens the calculation time, and can be implemented by simply modifying traditional anti-suppression interference algorithms, making it convenient and easy to implement. Attached Figure Description

[0029] Figure 1 This is a flowchart of the present invention;

[0030] Figure 2 This is a schematic block diagram illustrating the spatial detection characteristics of the adaptive beamforming algorithm;

[0031] Figure 3 This is a schematic block diagram of a spatial separation method for signals of the same frequency;

[0032] Figure 4 This is a schematic diagram describing the coordinates of the antenna array;

[0033] Figure 5 This is a schematic diagram of the composite radiation pattern of the antenna array;

[0034] Figure 6 This is a two-dimensional schematic diagram of the composite radiation pattern of the antenna array. Detailed Implementation

[0035] The present invention can be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "front", "rear", "left", "right" indicating the orientation or positional relationship, they are only corresponding to the drawings of this application for the convenience of describing the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation.

[0036] Example 1, in conjunction with Appendix Figures 1-4 A spatial separation method for co-frequency signals, which receives co-frequency satellite signals from different directions in space through an M-element array antenna, includes the following steps:

[0037] S1. Obtain the satellite's elevation and azimuth angles; these can be calculated from the satellite position and local position obtained by the receiver, combined with the antenna array attitude information, or by using methods such as direction finding of the satellite signal through the array channel.

[0038] S2. Calculate the steering vector of the satellite signal's direction of arrival; For an M*N rectangular planar array antenna, let the distance between adjacent antennas be d, the elevation angle of the space signal be θ, and the azimuth angle be φ, its steering vector... The distance difference in the X direction is dcosθcosφ, and the phase difference is 2π / λdcosθcosφ; the distance difference in the Y direction is dcosθsinφ, and the phase difference is 2π / λdcosθsinφ; then we have:

[0039]

[0040]

[0041] Usually, d = λ / 2 is taken, then:

[0042] a x =[1,e jπcos(θ)cos(φ) , ..., e jπ(M-1)cos(θ)cos(φ) ] T

[0043] a y =[1,e jπcos(θ)sin(φ) , ..., e jπ(N-1)cos(θ)sin(φ) ] T

[0044] calculate The steering vector of the signal with an elevation angle of θ and an azimuth angle of φ can be obtained. By changing the values ​​of θ and φ in turn, the steering vector of all satellite signals can be obtained.

[0045] S3. Inject interference signals from satellites other than the one to be targeted, to obtain a new input signal x'; Suppose there are L satellite signals s from different directions. i (t), whose direction of arrival is θ. i i = 1, ..., L, θ i The desired direction of arrival of the signal is θ. d , where a(θ) is the steering vector of the satellite signal with a direction of arrival of θ, the interference injected into the array received signal can be expressed as:

[0046]

[0047] J i (t) represents the direction of arrival θ. i The injected interference signal can be one or more combinations of broadband interference, narrowband interference, frequency sweep interference, pulse interference, or continuous wave interference. For ease of implementation and better implementation results, continuous wave interference or interference of the same type as the signal to be separated is preferred, such as broadband interference generated by spread spectrum signals that are consistent with satellite signals. In this embodiment, the injected interference signal is a continuous wave. For ease of calculation, the interference injected in each signal direction is set to be of the same type and the same magnitude, thus obtaining a new input signal x'.

[0048] S4. Apply an adaptive beamforming algorithm to the new input signal to obtain a composite beam pattern that forms a directional gain in the direction of the signal to be separated and a null in the direction of other signals, thereby separating signals of the same frequency; calculate the optimal weights based on the adaptive beamforming algorithm:

[0049]

[0050] Where R is the covariance matrix of the input signal x(t) after the injection of interference, and a(θ) d Let y(t) be the guiding vector of the array in the direction of the signal to be separated. The optimal weight W1 is obtained using signal x'. Substituting W1 into the formula y(t) = w H x(t) is the pointer to θ. d Directional satellite signals;

[0051] Change θ d By injecting interference into the directions of other satellites, we can obtain a new weight W2, which can be substituted into the formula y(t) = w Hx(t) can be used to separate the signal of the second satellite; by copying the signal L times, the signals of L satellites can be separated simultaneously using this method.

[0052] Because of the array processing algorithm, the array antenna with M elements has M-1 degrees of freedom and can separate up to M-1 signals of the same frequency at the same time. Most satellite navigation receivers have 12 channels. Considering that a certain margin can be left so that the system performance can achieve good processing results under not very harsh conditions, it can form 12 beam pointing with a 16-element planar array.

[0053] The navigation signal level received on the ground is between -122dBm and -133dBm. Considering the sensitivity range of a typical navigation receiver, the null depth pointing towards the direction of the satellite other than the satellite to be separated should be no less than 30dB. The theoretical gain of the 16-element antenna array in the direction of the satellite signal to be separated is 10*log16 = 12dB. After signal separation processing, the signals from each channel need to be combined and output. The signal loss after combining the signals from 12 channels is 10*log12 = 11dB. Considering the engineering processing loss, the carrier-to-noise ratio of the final output satellite signal is basically consistent with the actual reception.

[0054] Example 2, in conjunction with Appendix Figures 1-6 A spatial separation method for co-frequency signals, which differs from Embodiment 1 in that, based on Embodiment 1, a 16-element antenna array is used, with M=N=4; by substituting the elevation angle and azimuth angle of each satellite into the above formula, the steering vector of each satellite signal can be obtained;

[0055] Twelve satellites are evenly distributed at the zenith, with elevation and azimuth angles as follows: Satellite 1 (20°, 250°), Satellite 2 (70°, 40°), Satellite 3 (35°, 80°), Satellite 4 (80°, 150°), Satellite 5 (10°, 10°), Satellite 6 (40°, 340°), Satellite 7 (65°, 300°), Satellite 8 (80°, 200°), Satellite 9 (15°, 135°), Satellite 10 (55°, 220°), Satellite 11 (65°, 260°), and Satellite 12 (35°, 310°).

[0056] Satellite 4 is the satellite to be separated; Figure 5 This is a schematic diagram of the composite radiation pattern of the antenna array. As can be seen from the diagram, the beamforming algorithm creates multiple "nulls" in the radiation pattern. Figure 6 This is a two-dimensional schematic diagram of the composite radiation pattern of the antenna array. It can be clearly seen from the figure that the gain of the satellite signal to be separated is close to the normalized gain of 0dB, while a "null" with a depth of not less than 80dB is formed in the direction of other satellite signals, thereby separating the satellite signal to be separated.

[0057] The parts of this invention not described in detail are prior art. It will be apparent to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and are intended to encompass all changes falling within the meaning and scope of equivalents within this invention.

Claims

1. A spatial separation method for co-frequency signals, comprising receiving co-frequency satellite signals from different directions in space via an M-element array antenna, characterized in that: it includes... The following steps: S1. Obtain the satellite's elevation and azimuth angles; S2. Calculate the steering vector of the satellite signal's direction of arrival; S3. Inject interference signals from satellites other than the one to be targeted, to obtain a new input signal X'; Suppose there are L satellite signals s from different directions. i (t), whose direction of arrival is θ. i i = 1, ..., L, θ i The desired direction of arrival of the signal is θ. d , where a(θ) is the steering vector of the satellite signal with a direction of arrival of θ, the interference injected into the array received signal can be expressed as: J i (t) represents the direction of arrival θ. i Interference signals injected in the direction of the signal; S4. Apply an adaptive beamforming algorithm to the new input signal to obtain a composite beam pattern that forms a directional gain in the direction of the signal to be separated and a null in the direction of other signals, thereby separating signals of the same frequency; calculate the optimal weights based on the adaptive beamforming algorithm: Where R is the covariance matrix of the input signal x(t) after the injection of interference, and a(θ) d ) is the guiding vector of the array in the direction of the signal to be separated, and its weighted output is: y(t) = w H x(t) is the obtained separated signal.

2. The spatial separation method for co-frequency signals as described in claim 1, characterized in that: For an M-element array antenna, a maximum of M-1 co-frequency signals can be separated simultaneously, and the number of array elements is not less than the number of co-frequency signals to be separated.

3. The spatial separation method for co-frequency signals as described in claim 1, characterized in that: The interference signal injected in step S3 can be one or more combinations of broadband interference, narrowband interference, frequency sweep interference, pulse interference, or continuous wave interference.

4. The spatial separation method for co-frequency signals as described in claim 1 or 3, characterized in that: In step S3, the interference injected into the signal direction is set to be of the same type and the same magnitude.

5. The spatial separation method for co-frequency signals as described in claim 1, characterized in that: In step S4, the "zero depth" of the direction from which the satellite to be separated is located shall not be less than 30 dB.

6. The spatial separation method for co-frequency signals as described in claim 1, characterized in that: Using an M*N rectangular planar array antenna, in step S2, when calculating the steering vector of the satellite signal's direction of arrival, let the distance between adjacent antennas be d, the elevation angle of the space signal be θ, and the azimuth angle be φ, and its steering vector... The distance difference in the X direction is dcosθcosφ, and the phase difference is 2π / λdcosθcosφ; the distance difference in the Y direction is dcosθsinφ, and the phase difference is 2π / λdcosθsinφ; then we have: Usually, d = λ / 2 is taken, then: to x =[1,e jπcos(θ)cos(φ) ,…,And jπ(M-1)cos(θ)cos(φ) ] T to y =[1,e jπcos(θ)sin(φ) ,…,And jπ(N-1)cos(θ)sin(φ) ] T calculate This gives us the steering vector of the signal coming from the pitch angle θ and the azimuth angle φ.

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