Electromagnetic wave polarization parameter estimation method based on single antenna

Abstract

The electromagnetic wave polarization parameter estimation method based on a single antenna is implemented as follows: (1) establish a three-dimensional rectangular coordinate system, and the real signal of the electromagnetic wave incident from any direction in space is represented as E(n); (2) use two adjacent snapshot electric field vectors p1 and p2 to calculate the vector m(n) parallel to the propagation direction of the electromagnetic wave, and take its average value #imgabs0#; (3) estimate the pitch angle θ and azimuth angle φ of the incoming wave based on the components of the vector #imgabs1#; (4) use coordinate transformation to obtain the pitch component E of the electric field θ (n) and the azimuth component E φ (n); (5) Obtain the analytical signals #imgabs2# and #imgabs3# of each component through Hilbert transform (6) Calculate the amplitude E of each component θm (n) and E φm (n), calculate the polarization parameter γ(n); (7) calculate the phase difference Δ(n) between the elevation component and the azimuth component, and estimate the polarization parameter η(n); (8) average the above polarization parameters to obtain the phase descriptor #imgabs4#. The present invention has the advantage of estimating the polarization parameters of electromagnetic waves based on a single antenna, with low cost and small size. The present invention can be applied to fields requiring polarization parameter estimation, such as communications and radar.

Description

Technical Field

[0001] The present invention relates to fields such as communications and radar that require polarization parameter estimation, and in particular to a method for estimating electromagnetic wave polarization parameters using a single polarization-sensitive antenna. Background Art

[0002] In communications and radar, the polarization characteristics of electromagnetic waves are a valuable information dimension. This often requires analyzing signals received by antennas to estimate the polarization parameters of incident electromagnetic waves. Polarization phase descriptor parameters are a key method for describing the polarization characteristics of electromagnetic waves. To estimate polarization parameters, an array antenna is typically used. Each antenna element is an orthogonal dual-polarized antenna capable of receiving both horizontally and vertically polarized signals. The array antenna estimates the signal's angle of incidence, which is then used to estimate the polarization parameters. However, compared to a single antenna, array antennas are more expensive and bulky. Summary of the Invention

[0003] The problem to be solved by the present invention is: how to use a single antenna to estimate the polarization parameters of electromagnetic waves without knowing the direction of the incoming wave. The method for solving this technical problem is a method for estimating the polarization parameters of electromagnetic waves based on a single antenna, and its implementation steps are:

[0004] (1) The receiving antenna is a polarization-sensitive antenna, which consists of three mutually orthogonal linearly polarized antennas. A three-dimensional rectangular coordinate system XYZ is established with the geometric center of the three orthogonal linearly polarized antennas as the origin. The three coordinate axes of the rectangular coordinate system are parallel to the electric field directions of the three linearly polarized antennas. The real signal of the electromagnetic wave incident from any direction in space is expressed as E(n) = E x (n)x+E y (n)y+E z (n)z, where (x, y, z) are the unit vectors of the rectangular coordinate system, E x (n), E y (n) and E z (n) are the electric field components in the x, y, and z directions, respectively. n is the snapshot number of the sampling signal, n = 1, 2, ..., N, where N is the number of snapshots used for estimation;

[0005] (2) Take p1=[E x (n) E y (n) E z (n)] T and p2=[E x (n+1) E y (n+1) E z (n+1)] TTwo adjacent snapshot electric field vectors, "T" represents transposition, and according to vector operation, the vector m(n)=p1×p2=[m x m y m z ] T In order to reduce the influence of noise, the average value of multiple estimates is used

[0006] (3) According to vector The three-dimensional components of the wave direction are used to estimate the pitch angle and azimuth angle. The pitch angle θ is expressed as When θ=0, the electromagnetic wave is incident vertically along the z-axis; when θ≠0, according to Calculate the azimuth angle φ when hour when hour

[0007] (4) Transform the electric field components of the rectangular coordinate system to the spherical coordinate system to obtain the electric field E in the two angular directions θ (n) = E x (n)cosθcosφ+E y (n)cosθsinφ-E z (n)sinθ,E φ (n) = -E x (n)sinφ+E y (n)cosφ;

[0008] (5) The pitch component E θ (n) and the azimuth component E φ (n) Perform Hilbert transform to obtain its corresponding analytical signal, and Where H[] means to find Hilbert transform;

[0009] (6) Multiply the above two analytical signals and their corresponding conjugates and then take the square root to obtain the estimated amplitude values of the two electric field components, The symbol [] * It means taking conjugate, the estimated phase descriptor parameter γ(n)=arctan(|E θm (n) / E φm (n)|);

[0010] (7) Multiply the analytical signal of the pitch component by the conjugate of the analytical signal of the azimuth component, and then normalize the amplitude to obtain Calculate the phase difference between the elevation component and the azimuth component Δ(n) = angle(Y(n)), where Δ(n)∈[-π,π], and angle() represents the phase angle. When Δ(n) ≥ 0, the phase descriptor parameter η(n) = Δ(n); when Δ(n) < 0, the phase descriptor parameter η(n) = Δ(n) + π.

[0011] (8) Take the average of the above polarization parameters, that is, Finally, the phase descriptor of the polarization characteristics of the electromagnetic wave is obtained Complete polarization parameter estimation.

[0012] The invention has the beneficial effect of using a single polarization-sensitive antenna to receive electromagnetic waves, eliminating the need to know the direction of the incoming waves, saving costs, and reducing the size of the antenna. The invention can be applied to fields such as communications and radar that require polarization parameter estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a system block diagram of an electromagnetic wave polarization parameter estimation method based on a single antenna;

[0014] Figure 2 It is a schematic diagram of the incident angle of electromagnetic waves in the rectangular coordinate system. DETAILED DESCRIPTION

[0015] First, a single antenna receiving signal model is established, then the direction of the electromagnetic wave is estimated, and then the electric field component of the received signal is converted from the rectangular coordinate system to the spherical coordinate system, and finally the phase descriptor parameters are estimated. The overall steps are as follows: Figure 1 The specific implementation steps are as follows:

[0016] (1) The receiving antenna is a polarization-sensitive antenna, which consists of three mutually orthogonal linearly polarized antennas. A three-dimensional rectangular coordinate system XYZ is established with the geometric center of the three orthogonal linearly polarized antennas as the origin. The three coordinate axes of the rectangular coordinate system are parallel to the electric field directions of the three linearly polarized antennas. The angle of the electromagnetic wave incident from any direction in space is as follows: Figure 2 As shown, the polarization-sensitive antenna has three output ports, corresponding to the three linearly polarized electric field components in the coordinate axis direction, which are represented by vectors as E(n)=E x (n)x+E y (n)y+E z (n)z, where (x, y, z) are the unit vectors of the rectangular coordinate system, E x (n), E y (n) and E z (n) are the electric field components in the x, y, and z directions respectively, n is the snapshot number of the sampling signal, n = 1, 2, ..., N, and N is the number of snapshots used for estimation.

[0017] (2) Take p1=[E x (n) E y (n) E z (n)] T and p2=[E x (n+1) E y (n+1) E z (n+1)] T Two adjacent snapshot electric field vectors, "T" represents transposition, and according to vector operation, the vector m(n)=p1×p2=[m x m y m z ] T In order to reduce the influence of noise, the average value of multiple estimates is used

[0018] (3) Estimate the pitch angle and azimuth of the incoming wave direction based on the three-dimensional components of vector m. The pitch angle θ is expressed as When θ=0, the electromagnetic wave is incident vertically along the z-axis; when θ≠0, according to Calculate the azimuth angle φ when hour when hour

[0019] (4) Transform the electric field components of the rectangular coordinate system to the spherical coordinate system to obtain the electric field E in the two angular directions θ (n) = E x (n)cosθcosφ+E y (n)cosθsinφ-E z (n)sinθ,E φ (n) = -E x (n)sinφ+E y (n)cosφ.

[0020] (5) The pitch component E θ (n) and the azimuth component E φ (n) Perform Hilbert transform to obtain its corresponding analytical signal, and Where H[] represents the Hilbert transform.

[0021] (6) Multiply the above two analytical signals and their corresponding conjugates and then take the square root to obtain the estimated amplitude values of the two electric field components, The symbol [] * It means taking conjugate, the estimated phase descriptor parameter γ(n)=arctan(|E θm (n)E φm (n)|).

[0022] (7) Multiply the analytical signal of the pitch component by the conjugate of the analytical signal of the azimuth component, and then normalize the amplitude to obtain Calculate the phase difference between the elevation component and the azimuth component Δ(n)=angle(Y(n)), where Δ(n)∈[-π,π] and angle() represents the phase angle. When Δ(n)≥0, the phase descriptor parameter η(n)=Δ(n); when Δ(n)<0, the phase descriptor parameter η(n)=Δ(n)+π.

[0023] (8) Take the average of the above polarization parameters, that is, Finally, the phase descriptor of the polarization characteristics of the electromagnetic wave is obtained Complete polarization parameter estimation.

Claims

1. The electromagnetic wave polarization parameter estimation method based on a single antenna is implemented in the following steps: (1) The receiving antenna is a polarization-sensitive antenna, which consists of three mutually orthogonal linearly polarized antennas. A three-dimensional rectangular coordinate system XYZ is established with the geometric center of the three orthogonal linearly polarized antennas as the origin. The three coordinate axes of the rectangular coordinate system are parallel to the electric field directions of the three linearly polarized antennas. The real signal of the electromagnetic wave incident from any direction in space is expressed as E(n) = E x (n)x+E y (n)y+E z (n)z, where (x, y, z) are the unit vectors of the rectangular coordinate system, E x (n), E y (n) and E z (n) are the electric field components in the x, y, and z directions, respectively. n is the snapshot number of the sampling signal, n = 1, 2, ..., N, where N is the number of snapshots used for estimation; (2) Take p1=[E x (n) E y (n) E z (n)] T and p2=[E x (n+1) E y (n+1) E z (n+1)] T Two adjacent snapshot electric field vectors, "T" represents transposition, according to vector operation, the vector parallel to the propagation direction of the electromagnetic wave is obtained as m(n)=p1×p2=[m x m y m z ] T In order to reduce the influence of noise, the average value of multiple estimates is used (3) According to vector The three-dimensional components of the wave direction are used to estimate the pitch angle and azimuth angle. The pitch angle θ is expressed as When θ=0, the electromagnetic wave is incident vertically along the z-axis; when θ≠0, according to Calculate the azimuth angle φ when hour when hour (4) Transform the electric field components of the rectangular coordinate system to the spherical coordinate system to obtain the electric field E in the two angular directions θ (n) = E x (n)cosθcosφ+E y (n)cosθsinφ-E z (n)sinθ,E φ (n) = -E x (n)sinφ+E y (n)cosφ; (5) The pitch component E θ (n) and the azimuth component E φ (n) Perform Hilbert transform to obtain its corresponding analytical signal, and Where H[] means to find Hilbert transform; (6) Multiply the above two analytical signals and their corresponding conjugates and then take the square root to obtain the estimated amplitude values of the two electric field components, The symbol [] * It means taking conjugate, the estimated phase descriptor parameter γ(n)=arctan(|E θm (n) / E φm (n)|); (7) Multiply the analytical signal of the pitch component by the conjugate of the analytical signal of the azimuth component, and then normalize the amplitude to obtain Calculate the phase difference between the elevation component and the azimuth component Δ(n) = angle(Y(n)), where Δ(n)∈[-π,π], and angle() represents the phase angle. When Δ(n) ≥ 0, the phase descriptor parameter η(n) = Δ(n); when Δ(n) < 0, the phase descriptor parameter η(n) = Δ(n) + π. (8) Take the average of the above polarization parameters, that is, Finally, the phase descriptor of the polarization characteristics of the electromagnetic wave is obtained Complete polarization parameter estimation.

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