A rotation-based channel mismatch calibration and correlation interferometer direction finding method

Abstract

The present invention discloses a rotation-based channel mismatch calibration and correlation interferometer direction-finding method in the field of radio direction-finding technology. The rotation-based channel mismatch calibration and correlation interferometer direction-finding method includes the following steps: a process step of the rotation-based channel mismatch calibration and correlation interferometer direction-finding method; verifying the performance of the correlation interferometer direction-finding method using simulations; and evaluating the performance of the correlation interferometer direction-finding method based on a data set collected in a microwave darkroom. The rotation-based channel mismatch calibration and correlation interferometer direction-finding method can achieve a relatively ideal channel mismatch correction effect. On this basis, numerical calculations are used to construct a phase difference sample library, thereby improving the efficiency and accuracy of the direction-finding system.

Description

Technical Field

[0001] The present invention relates to the technical field of radio direction finding, and more particularly to a rotation-based channel mismatch calibration and correlation interferometer direction finding method. Background Art

[0002] Radio direction finding is the process of obtaining the direction of a signal source through equipment measurement based on the propagation characteristics of electromagnetic waves. Currently, the more common radio direction finding systems include phase response direction finding, amplitude response direction finding, and array response direction finding. Among them, the widely used circular array correlation interferometer belongs to the phase response direction finding system. The correlation interferometer direction finding method requires measuring the phase difference between each antenna array element and using the mapping relationship of the combination of phase differences on the angle axis to perform direction finding. For the correlation interferometer, the mismatch of the receiving channel causes the phase-frequency characteristics of each channel to be inconsistent, which will introduce errors when calculating the phase difference between each antenna array element, thereby causing the direction finding error of the correlation interferometer. Circular array interferometer direction finding technology is a technology that uses the principle of interferometer to determine the direction of the signal source. It determines the azimuth and elevation angle of the signal by measuring the phase difference of the signals received by different elements in the array antenna.

[0003] The mismatch of the receiving channel is an amplitude and phase error that is independent of the azimuth of the incident signal. It is relatively independent of errors caused by factors such as array element position error and antenna array mutual coupling. The main source of error is the inconsistency of the phase-frequency characteristics of the receiving channel composed of antenna elements, cables, and analog circuits. According to the direction-finding principle of the circular array correlation interferometer, the correction of the phase inconsistency of the circular array receiving channel is generally carried out by measuring a standard test signal incident perpendicular to the circular array to obtain phase difference data between different antenna elements. The data is stored in the system as correction data, similar to the inherent phase difference obtained between each channel. Thereafter, when the direction-finding system is actually working, after obtaining the measured phase difference, it is necessary to subtract the stored inherent phase difference data between each channel to complete the correction of the receiving channel mismatch.

[0004] However, in engineering applications, achieving the ideal perpendicular angle of incidence for standard test signals relative to the circular array is complex. Even with the use of auxiliary tools, it is difficult to avoid angle errors in these signals. Accurate correction of receive channel mismatch is impossible when angle errors exist. The impact of receive channel mismatch becomes more pronounced as the elevation angle of the incident signal increases.

[0005] While circular array interferometers (CAIs) offer high-precision and wide-coverage direction-finding capabilities, they also face challenges such as poor multipath mitigation, difficulty processing multiple signals, high computational complexity, and system size, weight, cost, and complexity. Existing CAIs suffer from mismatched receive channels, leading to inconsistent phase-frequency characteristics between channels. This introduces errors in the calculation of phase differences between antenna elements, resulting in direction-finding errors in the CAI. Summary of the Invention

[0006] The purpose of the present invention is to provide a rotation-based channel mismatch calibration and correlation interferometer direction-finding method to solve the technical problem that the mismatch of the receiving channels of the circular array correlation interferometer direction-finding technology in the prior art causes inconsistent phase-frequency characteristics of each channel, introduces errors when calculating the phase difference between each antenna array element, and thus leads to direction-finding errors of the correlation interferometer. The inconsistency of the phase-frequency characteristics of the circular array receiving channel is corrected, and on this basis, a phase difference sample library is efficiently and accurately constructed; theoretical analysis proves the effectiveness of the rotation correction method for receiving channel mismatch, and at the same time, a verification method combining simulation and experiment is used to effectively prove the good performance of the proposed method and improve the direction-finding accuracy of the circular array correlation interferometer.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a rotation-based channel mismatch calibration and correlation interferometer direction finding method, comprising the following steps:

[0009] S1. Process steps of the rotation-based channel mismatch calibration and correlation interferometer direction finding method;

[0010] S2. Use simulation to verify the performance of the correlation interferometer direction finding method, and evaluate the performance of the correlation interferometer direction finding method based on the data set collected in the microwave anechoic chamber.

[0011] Furthermore, the S1 includes the following steps:

[0012] S11. Collecting standard test signals based on a specific rotation mode of the turntable;

[0013] S12. Correct the inconsistency of the phase-frequency characteristics of the circular array receiving channel, and build a phase difference sample library based on this.

[0014] Furthermore, the S11 includes the following steps:

[0015] S111. Set the interval of the turntable rotation angle θ to Δη, and evenly divide the azimuth angle of 0° to 360° with the interval Δη to obtain the turntable rotation angle set Θ = [0, Δη, 2Δη, ..., (360-Δη)];

[0016] S112. When the Q-element circular array estimates the incoming wave direction, the reference channel receives the signal from the center element O. The main channel receives the signals from each element on the circumference in a time-sharing manner. The signals are down-converted to intermediate frequencies through the receiving channel and then sampled.

[0017] S113. The turntable rotates according to the angle set Θ. After each rotation, the data of the standard test signal is collected. The two sampling data are transformed by FFT. The spectral line position corresponding to the maximum value of the FFT amplitude spectrum is found, and the phase difference data is calculated by conjugate multiplication.

[0018] Furthermore, the S12 includes the following steps:

[0019] S121. Repeat Q times to obtain the phase difference between all elements on the circumference of the circular array and the central element, forming the phase difference vector data f(α, β, θ). Based on the rotation of the turntable and the completion of data acquisition, the phase difference data corresponding to the rotation angle set Θ are summed to obtain the channel mismatch correction result;

[0020] S122. Divide the possible areas of the incoming wave direction into a grid, where the grid division intervals meet the direction-finding error requirements, construct the theoretical phase difference vector for each possible incoming wave direction at the grid point, and subtract the correction result of the channel mismatch to construct a phase difference sample library;

[0021] S123. Select the cosine function as the cost function, and perform correlation operation on the phase difference vector data and the data stored in the phase difference sample library according to the decision rule.

[0022] Furthermore, the S121 includes the following steps:

[0023] S1211. After the rotation of the turntable and data collection are completed, the phase difference data corresponding to the rotation angle set Θ is summed to obtain

[0024]

[0025] Simplifying the key terms in the first two terms of the above formula, we have

[0026]

[0027]

[0028]

[0029] get,

[0030]

[0031] S1212. Ignoring oΔα, Δβ, further simplifying, the correction data for channel mismatch can be obtained as:

[0032]

[0033] Furthermore, the S2 includes the following steps:

[0034] S21. Method performance verification: Use simulation to verify the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method;

[0035] S22. Experimental Verification: Based on a data set collected in a microwave anechoic chamber, the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method is evaluated.

[0036] Furthermore, the S21 includes the following steps:

[0037] S211. Set the test system parameters. The direction finding error is expressed as the root mean square error (RMSE).

[0038] S212. Conduct simulation experiments on simulation scenarios based on multiple influencing factors such as signal-to-noise ratio, number of sampling points, and radius-to-wavelength ratio.

[0039] Furthermore, the test system parameters in S211 are: radius-to-wavelength ratio R / λ=3, N independent simulations are performed, and in the test data of each simulation, the azimuth angle range is 0° to 360° and the pitch angle range is 0° to 90°; the root mean square error RMSE formula is as follows:

[0040]

[0041] Among them, Δα i and Δβ i is the difference between the i-th measured direction and the true direction.

[0042] By adopting the above technical solution, the present invention has the following advantages:

[0043] The present invention provides a rotation-based channel mismatch calibration and correlation interferometer direction-finding method, which can collect standard test signals from a specific rotation mode of a turntable, correct the inconsistency of the phase-frequency characteristics of the circular array receiving channel, and efficiently and accurately construct a phase difference sample library on this basis, thereby improving the efficiency and direction-finding accuracy of the direction-finding system. Theoretical analysis proves the effectiveness of the rotation-corrected receiving channel mismatch method, and the conclusion is verified through simulation. Based on a data set collected in a microwave anechoic chamber, the direction-finding performance of the channel mismatch calibration and correlation interferometer direction-finding method is evaluated, effectively demonstrating the good performance of the method and improving the direction-finding accuracy of the circular array correlation interferometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0045] Figure 1 It is a schematic diagram of a circular array correlation interferometer direction finding receiver;

[0046] Figure 2 It is a schematic diagram of circular array direction finding;

[0047] Figure 3 Schematic diagram of a method for correcting receiving channel mismatch based on rotation;

[0048] Figure 4 is a flow chart of a rotation-based channel mismatch calibration and correlation interferometer direction finding method;

[0049] Figure 5 is the direction finding accuracy in different signal-to-noise ratio scenarios;

[0050] Figure 6 is the direction finding accuracy for scenarios with different numbers of sampling points;

[0051] Figure 7 is the direction finding accuracy for different scenarios with radius-wavelength ratio;

[0052] Figure 8 is a schematic diagram of a data acquisition method based on rotation correction for receiving channel mismatch;

[0053] Figure 9 (a) is the measured original phase difference between the circumferential array element and the central array element;

[0054] Figure 9 (b) is the phase difference between the circumferential array element and the central array element after channel mismatch correction;

[0055] Figure 10 is the direction-finding error of the measured data. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is described in detail below in conjunction with the drawings of the specification. The detailed features and advantages of the present invention are described in detail in the specific implementation mode. The content is sufficient to enable any technical personnel in this field to understand the technical content of the present invention and implement it accordingly. According to the description, claims and drawings disclosed in this specification, those skilled in the art can easily understand the relevant purposes and advantages of the present invention.

[0057] The relevant interferometer direction finding method is as follows:

[0058] The schematic diagram of the circular array correlation interferometer direction finding receiver is as follows: Figure 1As shown in the figure, a Q-element uniform circular array with a central element is considered, consisting of antenna elements, RF switches, receiving channels, and a signal processing unit. One antenna element is located at the center of the circular array and independently connected to one receiving channel, called the reference channel. The Q antenna elements are evenly distributed around the circumference of the circular array and are connected to another receiving channel, called the main channel, in a timed sequence via the RF switch. Receive channel mismatch is an amplitude and phase error that is independent of the incident signal's azimuth. It is related to factors such as differences in channel components, channel routing, and array element routing, leading to phase inconsistencies in the received signal.

[0059] The different spatial distances at which radio waves reach each antenna element cause the phase of the output signal to differ. Furthermore, the phase difference between the output signals of different elements is closely related to the direction of the incident signal. Circular array correlation interferometers typically determine the direction of the radiation source by measuring the phase difference between elements. Receive channel mismatch can affect direction-finding performance.

[0060] Assume that the signal x(t) reaches the antenna array element, x(t) = s(t) + n(t), s(t) is a single tone signal with a carrier frequency of f0, and n(t) is a signal with a mean of 0 and a variance of Narrowband Gaussian noise. For x(t) with f s The sampling rate is M points, with Δt = 1f s As the sampling interval, and m is used to represent mΔt. Then the sampling signal of the qth array element is:

[0061] x q (m) = s q (m)+n q (m),m=0,1,…,M-1q=1,…,Q (1)

[0062] After discrete Fourier transform DFT transformation, we get k is the number of the frequency domain signal, k∈0,1,…,K-1.

[0063] like Then the phase estimate of the received signal of the qth array element is

[0064]

[0065] Therefore, q represents the direction finding baseline composed of the qth antenna array element and the central array element. The phase difference between the received signal of array element q and the central array element O (denoted as array element 0) is Or

[0066]

[0067] Assume that the signal arrives at the antenna array element with the incident direction α, β, where α and β represent the azimuth and elevation angles of the incident signal, α∈0,360°, β∈0,90°, and let It represents the phase error related to the incident signal azimuth α, β. The phase difference of the received signal between the array elements on the circumference and the center array element is recorded as a vector form. This vector is related to the signal frequency, azimuth angle, and pitch angle.

[0068] In practical applications, by selecting some discrete frequencies, azimuths and elevation angles, the corresponding phase difference vectors are obtained and a phase difference sample library is constructed.

[0069] Let the phase difference vector of the incident signal measured data be expressed as:

[0070]

[0071] Under certain measurement criteria, Matching is performed to find the closest set of data from the phase difference sample library. The corresponding azimuth information is the direction of the incident signal. In the correlation matching process, it is used to measure the measured phase difference. The function that measures the degree of closeness to the phase sample f(α,β) is called the cost function or correlation function, and its function value is also called similarity. The cosine function is used as the cost function, and the decision rule is:

[0072]

[0073] in, represents the qth component of f(α,β), for The qth component of .

[0074] Due to the presence of noise, the peak value of the cost function generally does not reach the ideal value. The larger the peak value of the cost function, the closer the matched phase difference sample is to the measured phase difference, and the more reliable the direction finding result determined by it. If the peak value of the cost function is too small, it means that there are no samples in the original sample library that are close to the measured phase difference. The direction finding result determined by it is likely to be incorrect, and consider filtering out this direction finding result.

[0075] The impact of receiving channel mismatch on direction finding:

[0076] The schematic diagram of circular array direction finding is as follows: Figure 2 As shown, the three-dimensional coordinates xyz are established with the center O of the circular array as the origin, and the angle between the array element 1 and the x-axis is θ ( Figure 2 As shown in θ<0), when the incident signal a reaches the circular array with the incident direction α, β, the phase difference between the signal received by the array element q and the central array element O is Expressed as

[0077]

[0078] In the above formula, the subscript q represents the phase difference between the signals received by element q and the central element O, R is the array radius, λ is the wavelength of the incident signal, α and β represent the azimuth and elevation angles of the incident signal, respectively, and θ represents the angular difference between the line connecting element 1 and the central element O and the x-axis in the coordinate system.

[0079] The phase difference vector between the received signals of all the array elements on the circumference and the central array element is expressed as:

[0080]

[0081] A common correction method for receiving channel mismatch is to use a standard test signal incident perpendicular to the circular array, incident along the z-axis at a 90° elevation angle. The theoretical phase difference between different antenna elements received by the circular array is 0°. Therefore, to correct for phase inconsistencies between the circular array antenna elements and the cables between the antenna switches, it is sufficient to measure the phase difference at each frequency point at a 90° elevation angle. This is similar to the inherent phase difference between channels in signal acquisition. Based on this, combined with an expression based on the array steering vector, a phase difference sample library can be numerically calculated.

[0082] However, in reality, the incident angle of the standard test signal deviates from the z-axis to a certain extent, which leads to errors in the calibration of channel mismatch. Due to the influence of channel mismatch, an error unrelated to the incident signal is introduced into the modeling of the phase difference, which is expressed as

[0083]

[0084] In the above formula, represents the phase difference calculated from the measured data, Represents the phase difference data in the phase difference sample library, It represents the fixed phase difference between the channel of array element q and the center array element baseline, and ε represents the error caused by factors such as phase noise.

[0085] This paper analyzes the impact of correction errors on the direction-finding results of the correlation interferometer. Assuming an incident signal radius-to-wavelength ratio of 3, an elevation angle deviation of Δα, an azimuth angle of 0°, and a phase difference sample library resolution of 0.2°, the introduction of a fixed phase error in each channel during calculation results in phase difference errors for different incident radiation sources. This also introduces errors in the direction-finding results of the correlation interferometer, focusing on the elevation angle error.

[0086] Table 1 Relationship between direction-finding error of correlation interferometer and channel mismatch

[0087]

[0088] As shown in Table 1 above, elevation angle deviation causes channel mismatch. Furthermore, array surface unevenness further exacerbates this problem. As the elevation angle increases, direction-finding performance deteriorates. Faced with the demand for high-precision direction finding, methods for correcting phase mismatches between circular array antenna elements and cable array elements are difficult to achieve ideal normal alignment in actual engineering practice. The resulting error increases exponentially with increasing elevation angle, leading to exponentially higher direction-finding errors.

[0089] Direction finding method based on rotation correction of receiving channel mismatch

[0090] In theory, it is only necessary to measure the phase difference of each frequency point when the pitch angle β = 90°, which is similar to the inherent phase difference between each channel obtained by the correction signal. After that, the measured phase difference data received each time is subtracted from the inherent phase difference

[0091] The direction finding method based on rotation correction receiving channel mismatch is as follows: Figure 3 As shown in the figure, the circular array device on the left receives a standard test signal. The enlarged view shows that during calibration, the angle of the incident test signal and the z-axis deviates, causing a deviation in the channel mismatch calibration data.

[0092] Considering the correction signal angle error, let α0, β0, Δα and Δβ represent the azimuth angle, pitch angle and their respective angular deviations of the correction signal, respectively, and record them as (α, β) = (α0 + Δα, β0 + Δβ), then we have

[0093]

[0094] Where o(Δα, Δβ) is a high-order small error vector about Δα and Δβ, Indicates the phase difference of each channel mismatch,

[0095]

[0096] The interval of the turntable rotation angle θ is set to Δη, and the azimuth angle from 0° to 360° is evenly divided by this interval Δη. The turntable rotation angle set Θ = [0, Δη, 2Δη, …, (360-Δη)] is obtained. The turntable rotates according to the angle set Θ. After each rotation, the data of the standard test signal is collected, and the corresponding phase difference data is calculated to obtain f(α, β, θ).

[0097] After the rotation of the turntable and data collection are completed, the phase difference data corresponding to the rotation angle set Θ are summed to obtain:

[0098]

[0099] Simplifying the key terms in the first two terms of the above formula, we have

[0100]

[0101]

[0102]

[0103] Then you can get,

[0104]

[0105] Ignoring o(Δα, Δβ), we can further simplify and obtain the correction data for channel mismatch:

[0106]

[0107] Therefore, using a simple turntable-based test measurement method, it is possible to accurately calculate channel mismatch correction data. Based on this, combined with the phase difference calculation formula related to the signal's incident azimuth, appropriate angular intervals can be selected according to the direction-finding requirements. This numerical calculation method can be used to create a table and construct a phase difference sample library, significantly reducing the workload of field measurement "table creation." The direction-finding process uses a simple vector correlation operation, rather than the inverse cosine calculation used in traditional phase interferometer direction-finding. This eliminates the need for a deambiguation process, enabling comprehensive direction-finding with high accuracy.

[0108] The present invention provides a method for channel mismatch calibration and direction finding based on rotation, which specifically includes the following steps: Figure 4 As shown:

[0109] S1. Process steps of the rotation-based channel mismatch calibration and correlation interferometer direction finding method;

[0110] Among them, S1 includes the following specific steps:

[0111] S11. Collecting standard test signals based on a specific rotation mode of the turntable;

[0112] S11 includes the following specific steps:

[0113] S111. Set the interval of the turntable rotation angle θ to Δη, and evenly divide the azimuth angle of 0° to 360° with the interval Δη to obtain the turntable rotation angle set Θ = [0, Δη, 2Δη, ..., (360-Δη)];

[0114] S112. When the Q-element circular array estimates the incoming wave direction, the reference channel receives the signal from the center element O. The main channel receives the signals from each element on the circumference in a time-sharing manner. The signals are down-converted to intermediate frequencies through the receiving channel and then sampled.

[0115] S113. The turntable rotates according to the angle set Θ. After each rotation, the data of the standard test signal is collected. The two sampling data are transformed by FFT. The spectral line position corresponding to the maximum value of the FFT amplitude spectrum is found, and the phase difference data is calculated by conjugate multiplication.

[0116] S12. Correct the inconsistency of the phase-frequency characteristics of the circular array receiving channel, and build a phase difference sample library based on this.

[0117] Wherein, S12 includes the following specific steps:

[0118] S121. Repeat Q times to obtain the phase difference between all elements on the circumference of the circular array and the central element, forming the phase difference vector data f(α, β, θ). Based on the rotation of the turntable and the completion of data acquisition, the phase difference data corresponding to the rotation angle set Θ are summed to obtain the channel mismatch correction result;

[0119] S122. Divide the possible areas of the incoming wave direction into a grid, where the grid division intervals meet the direction-finding error requirements, construct the theoretical phase difference vector for each possible incoming wave direction at the grid point, and subtract the correction result of the channel mismatch to construct a phase difference sample library;

[0120] S123. Select the cosine function as the cost function and, based on the decision rule, perform a correlation operation on the phase difference vector data and the data stored in the phase difference sample library. The goal is to find the set of data in the phase difference sample library that is closest to the phase difference vector of the incoming signal. The corresponding azimuth information is the direction of the incident signal.

[0121] S2. Use simulation to verify the performance of the rotation-based channel mismatch calibration and correlation interferometer direction-finding method, and evaluate the performance of the rotation-based channel mismatch calibration and correlation interferometer direction-finding method based on the data set collected in the microwave anechoic chamber.

[0122] Among them, S2 includes the following specific steps:

[0123] S21. Method performance verification: Use simulation to verify the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method;

[0124] S21 includes the following steps:

[0125] S211. Test system parameter settings: radius-to-wavelength ratio R / λ = 3, perform N independent simulations, and in each simulation, the azimuth angle range is 0° to 360° and the elevation angle range is 0° to 90°. The direction-finding error is expressed as the root mean square error (RMSE).

[0126]

[0127] Among them, Δαi and Δβ i is the difference between the i-th measured direction and the true direction.

[0128] S212. Conduct simulation experiments on simulation scenarios based on multiple influencing factors such as signal-to-noise ratio, number of sampling points, and radius-to-wavelength ratio.

[0129] Simulation Scenario 1: Signal-to-Noise Ratio

[0130] Simulation test conditions: a narrowband signal arrives at a 5-element uniform circular array, the radius-to-wavelength ratio R / λ is set to 3, the elevation angle is randomly selected from 30° to 90°, the azimuth angle range is 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent experiments are performed under different signal-to-noise ratio conditions. Figure 5 The curve showing the direction finding error of the method of the present invention as the signal to noise ratio changes. Figure 5 It can be concluded that the direction finding error of the method of the present invention decreases with the increase of the signal-to-noise ratio.

[0131] Simulation scenario 2: number of sampling points

[0132] Simulation test conditions: a narrowband signal arrives at a 5-element uniform circular array, the radius-to-wavelength ratio R / λ is set to 3, the elevation angle is randomly selected from 30° to 90°, the azimuth angle range is 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent experiments are performed under different sampling point conditions. Figure 6 The curve showing the direction finding error of the method of the present invention as the signal to noise ratio changes. Figure 6 It can be concluded that the direction finding error of the method of the present invention decreases as the number of sampling points increases.

[0133] Simulation Scenario 3: Radius-to-Wavelength Ratio

[0134] The simulation test conditions are as follows: a narrowband signal arrives at a 5-element uniform circular array, the radius-to-wavelength ratio is set to R / λ = 3, the elevation angle is randomly selected from 30° to 90°, the azimuth angle range is 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent experiments are performed under different radius-to-wavelength ratio conditions. Figure 7 The curve showing the direction finding error of the method of the present invention as the signal to noise ratio changes. Figure 7 It can be concluded that the direction-finding error of the method of the present invention decreases with the increase of the radius-to-wavelength ratio.

[0135] S22. Experimental Verification: Based on a data set collected in a microwave anechoic chamber, the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method is evaluated.

[0136] like Figure 8As shown in the figure, data acquisition based on rotation correction for receive channel mismatch is performed in a darkroom. On the left is the circular array device under test, which is rotated about the z-axis using a turntable. On the right is a standard test source, emitting a standard test signal. The measured data parameters are set as follows: using a uniform 5-element circular array for direction finding, Q = 5, the radius-to-wavelength ratio R / λ = 3, the standard test source level at 0 dBW, the elevation angle range from 30° to 90°, the azimuth angle range from 0° to 360°, and the distance between the source and the circular array device under test at 5 m. The stepping interval is set to 0.5°, and the azimuth angle is evenly divided into this interval, resulting in a rotation angle set Θ = [0, 0.5°, 1°, …, 359.5°]. The turntable's azimuth angle is set according to this angle set. After each rotation, the incident standard test signal data is collected, and the corresponding phase difference data is calculated.

[0137] The phase difference data of all array elements and the central array element calculated from the measured data are as follows: Figure 9 As shown in (a), after the rotation of the turntable and data acquisition are completed, the phase difference data corresponding to the rotation angle set θ are summed to obtain the channel mismatch correction result [-1.6699 1.1683 -2.4556 1.0067 0.7370]. The phase difference data of all array elements and the central array element after calibrating the channel mismatch are as follows: Figure 9 As shown in (b), Figure 9 (b) shows the improvement in channel mismatch. It should be noted that because the standard test signal has a small pitch angle deviation, the phase difference values ​​are concentrated within the [-π,π] range. Even if the phase difference data exceeds the [-π,π] range, phase ambiguity can be easily corrected.

[0138] The direction-finding error of the measured data is as follows: Figure 10 As shown, from Figure 10 The results of the measured data analysis show that the direction finding error performance of the method of the present invention is good, and the direction finding error of more than 98% of the measured data is less than 0.5°.

[0139] Finally, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. Various equivalent changes or substitutions can be made without departing from the concept of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the essential spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. A rotation-based channel mismatch calibration and correlation interferometer direction finding method, characterized in that: The following steps are involved: S1. Process steps of the rotation-based channel mismatch calibration and correlation interferometer direction finding method; Said S1 comprises the following steps: S11. Collecting standard test signals based on a specific rotation mode of the turntable; The S11 includes the following steps: S111. Set the interval of the turntable rotation angle θ to Δη, and evenly divide the azimuth angle of 0° to 360° with the interval Δη to obtain the turntable rotation angle set Θ = [0, Δη, 2Δη, ..., (360-Δη)]; S12. Correct the inconsistency of the phase-frequency characteristics of the circular array receiving channel and build a phase difference sample library based on this; The S12 includes the following steps: S121. Repeat Q times to obtain the phase difference between all the array elements on the circumference of the circular array and the central array element, forming the phase difference vector data f(α, β, θ). Based on the rotation of the turntable and after the data acquisition is completed, the phase difference data corresponding to the rotation angle set θ are summed to obtain the channel mismatch correction result. S2. Use simulation to verify the performance of the correlation interferometer direction finding method, and evaluate the performance of the correlation interferometer direction finding method based on the data set collected in the microwave anechoic chamber.

2. A rotation-based channel mismatch calibration and correlation interferometer direction finding method according to claim 1, characterized in that: The S11 further includes the following steps: S112. When the Q-element circular array estimates the incoming wave direction, the reference channel receives the signal from the center element O. The main channel receives the signals from each element on the circumference in a time-sharing manner. The signals are down-converted to intermediate frequencies through the receiving channel and then sampled. S113. The turntable rotates according to the angle set Θ. After each rotation, the data of the standard test signal is collected. The two sampling data are transformed by FFT. The spectral line position corresponding to the maximum value of the FFT amplitude spectrum is found, and the phase difference data is calculated by conjugate multiplication.

3. The rotation-based channel mismatch calibration and correlation interferometer direction finding method according to claim 1, characterized in that: The S12 further includes the following steps: S122. Divide the possible areas of the incoming wave direction into a grid, where the grid division intervals meet the direction-finding error requirements, construct the theoretical phase difference vector for each possible incoming wave direction at the grid point, and subtract the correction result of the channel mismatch to construct a phase difference sample library; S123. Select the cosine function as the cost function, and perform correlation operation on the phase difference vector data and the data stored in the phase difference sample library according to the decision rule.

4. The method for channel mismatch calibration and direction finding based on rotation according to claim 1, wherein: The S121 includes the following steps: S1211. After the rotation of the turntable and data collection are completed, the phase difference data corresponding to the rotation angle set Θ is summed to obtain Simplifying the key terms in the first two terms of the above formula, we have get, S1212. Ignore o(Δα, Δβ) and further simplify to obtain the channel mismatch correction data:

5. The method for channel mismatch calibration and direction finding based on rotation according to claim 1, wherein: The S2 comprises the following steps: S21. Method performance verification: Use simulation to verify the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method; S22. Experimental Verification: Based on a data set collected in a microwave anechoic chamber, the performance of the rotation-based channel mismatch calibration and correlation interferometer direction finding method is evaluated.

6. The method for channel mismatch calibration and direction finding based on rotation according to claim 5, wherein: The S21 includes the following steps: S211. Set the test system parameters. The direction finding error is expressed as the root mean square error (RMSE). S212. Conduct simulation experiments based on multiple influencing factors such as signal-to-noise ratio, number of sampling points, and radius-to-wavelength ratio.

7. The method for channel mismatch calibration and direction finding based on rotation according to claim 6, wherein: The test system parameters in S211 are: radius-to-wavelength ratio R / λ=3, and N independent simulations are performed. In the test data of each simulation, the azimuth angle range is 0° to 360°, and the pitch angle range is 0° to 90°. The root mean square error (RMSE) formula is as follows: Among them, Δα i Indicates the difference between the azimuth measured direction and the true direction, Δβ i It represents the difference between the i-th measured direction of the pitch angle and the true direction.

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