Rotation-based channel mismatch calibration and correlation interferometer direction finding method

Abstract

The invention discloses a rotation-based channel mismatch calibration and correlation interferometer direction finding method in the technical field of radio direction finding. The rotation-based channel mismatch calibration and correlation interferometer direction finding method comprises the following steps: flow steps of the rotation-based channel mismatch calibration and correlation interferometer direction finding method; the performance of the correlation interferometer direction finding method is verified through analog simulation, and the performance of the correlation interferometer direction finding method is evaluated on the basis that a data set is collected in a microwave anechoic chamber. According to the rotation-based channel mismatch calibration and correlation interferometer direction-finding method, an ideal channel mismatch correction effect can be achieved, a phase difference sample library is constructed by using numerical calculation on the basis, and the efficiency and the direction-finding precision of a direction-finding system are improved.

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 to obtain the direction of the 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, array response direction finding, etc. 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 for 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 the errors caused by factors such as array element position error and antenna array mutual coupling. The error source is mainly 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 the standard test signal incident perpendicular to the circular array to obtain the phase difference data between different antenna elements, which is saved in the system as correction data, similar to the inherent phase difference between the channels. After that, 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 the channels to complete the correction of the mismatch of the receiving channel.

[0004] However, in engineering applications, it is relatively complicated to make the standard test signal reach the ideal incident angle perpendicular to the circular array. Even with additional auxiliary tools, it is difficult to avoid the incident angle error of the standard test signal. When there is an incident angle error, it is impossible to accurately correct the mismatch of the receiving channel. When the pitch angle of the incident signal increases, the impact of the mismatch of the receiving channel will be more significant.

[0005] For circular array correlation interferometer, while providing high-precision and wide coverage direction finding capabilities, circular array interferometer direction finding technology faces challenges such as poor anti-multipath capability, difficulty in processing multiple signals, high computational complexity, system size and weight, and cost and complexity. For the existing circular array correlation interferometer direction finding technology, 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. Summary of the invention

[0006] The purpose of the present invention is to provide a channel mismatch calibration and correlation interferometer direction finding method based on rotation, so as to solve the technical problem that the mismatch of the receiving channel of the circular array correlation interferometer direction finding technology in the prior art causes the phase-frequency characteristics of each channel to be inconsistent, and errors will be introduced when calculating the phase difference between each antenna array element, thereby causing the direction finding error 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 receiving channel mismatch method, 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 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 darkroom.

[0011] Furthermore, the S1 comprises 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 comprises 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 of the central element O, and the main channel receives the signals of the elements on the circumference in a time-sharing manner, down-converts them into intermediate frequency signals through the receiving channel, and then samples them;

[0017] S113. The turntable rotates according to the angle set θ, collects data of the standard test signal after each rotation, performs FFT transformation on the two-way sampling data, finds the spectral line position corresponding to the maximum value of the FFT amplitude spectrum, and calculates the phase difference data by conjugate multiplication.

[0018] Further, the S12 comprises the following steps:

[0019] S121. Repeat Q times to obtain the phase difference between all array elements on the circumference of the circular array and the central array element, forming the phase difference vector data f(α, β, θ). 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 correction result of the channel mismatch;

[0020] S122. Divide the possible area of ​​the incoming wave direction into grids, the grid division interval meets the direction finding error requirements, construct the theoretical phase difference vector of each possible incoming wave direction on 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] Further, 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. Ignore oΔα, Δβ, and further simplify, the correction data of channel mismatch can be obtained as:

[0032]

[0033] Further, the S2 comprises the following steps:

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

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

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

[0037] S211. Set the test system parameters, and the direction finding error is expressed by the root mean square error RMSE;

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

[0039] Further, 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 channel mismatch calibration and correlation interferometer direction finding method based on rotation, which can collect standard test signals from a specific rotation mode of a turntable, correct the inconsistency of the phase-frequency characteristics of a 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 correction receiving channel mismatch method, and the conclusion is verified through simulation; based on a data set collected in a microwave darkroom, the direction finding performance of the channel mismatch calibration and correlation interferometer direction finding method is evaluated, which effectively proves the good performance of the method and improves the direction finding accuracy of the circular array correlation interferometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objectives and advantages of the present invention will become more apparent from a reading of the detailed description of non-limiting embodiments made with reference to the following 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 is a schematic diagram of a method for correcting mismatch of receiving channels 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] Fig. 9 (a) is the measured original phase difference between the circumferential array element and the central array element;

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

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

[0056] The technical solution of the present invention is specifically described below in conjunction with the drawings in 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 the 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, the technical personnel in the field 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, which is composed of antenna elements, RF switches, receiving channels, signal processing units, etc. Among them, one antenna element is located at the center of the circular array and is independently connected to one receiving channel, called the reference channel; the positions of Q antenna elements are evenly distributed on the circumference of the circular array, and are switched in sequence by the RF switch to connect to another receiving channel, called the main channel. The mismatch of the receiving channel is an amplitude and phase error that is independent of the azimuth of the incident signal. It is related to factors such as the differences in the components of the channel, the channel routing, and the array element routing, resulting in inconsistency in the phase of the received signal.

[0059] The spatial distances at which radio waves reach each antenna array element are different, which results in different phases of the output signals from each antenna array element. Moreover, the phase difference between the output signals of different array elements is closely related to the direction of the incident signal. Circular array correlation interferometers generally determine the direction of the radiation source by measuring the phase difference between array elements. The mismatch of the receiving channel will affect the direction finding performance.

[0060] Assume that the signal x(t) arrives at 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. s The sampling rate samples 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 angle of the incident signal, α∈0,360°, β∈0,90°, and It represents the phase error related to the incident signal azimuth α, β. The phase difference combination of the received signal between the array elements on the circumference of the circular array and the central array element is recorded as a vector form. This vector is related to the signal frequency, azimuth and elevation 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 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 selected 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 cannot 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 higher the credibility of the direction finding result determined by it. If the peak value of the cost function is too small, it means that there is no sample in the original sample library that is close to the measured phase difference, and the direction finding result determined by it is likely to be wrong, so consider filtering out the 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 array element 1 and the x-axis is θ ( Figure 2 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 signal received by the array element q and the central array 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 angle difference between the line connecting the array element 1 and the central array element O and the x-axis in the coordinate system.

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

[0080]

[0081] The common correction method for receiving channel mismatch is to use a standard test signal incident perpendicular to the circular array, a signal incident along the coordinate axis z-axis with an elevation angle of 90°, and the theoretical phase difference between different antenna elements received by the circular array is 0°. Therefore, for the correction of the phase inconsistency of the circular array antenna elements and the cables before the antenna switching switch, it is only necessary to measure the phase difference of each frequency point at an elevation angle of 90°, which is similar to the inherent phase difference between each channel of the signal acquisition. On this basis, combined with the expression based on the array steering vector, the phase difference sample library can be obtained by numerical calculation.

[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 the channel mismatch factor, 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] The influence of correction error on the direction-finding results of correlation interferometer is analyzed. Assuming that the incident signal radius-to-wavelength ratio is 3, the elevation angle deviates from Δα, the azimuth angle is 0°, and the resolution of the phase difference sample library is 0.2°, the fixed phase error of each channel is introduced during calculation, resulting in phase difference errors of different incident radiation sources. The direction-finding results of correlation interferometer also produce errors, and the analysis of elevation angle error is focused on.

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

[0087]

[0088] As can be seen from Table 1 above, the pitch angle deviation causes channel mismatch. In addition, the uneven array surface will further aggravate the channel mismatch problem. As the pitch angle increases, the direction finding performance becomes worse. In the face of high-precision direction finding requirements, the method of correcting the phase inconsistency between circular array antenna elements and cable array elements is difficult to achieve ideal normal alignment in actual engineering practice. The resulting error increases exponentially with the increase of the pitch angle.

[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 minus the inherent phase difference

[0091] The direction finding method based on rotation correction receiving channel mismatch is as follows: Figure 3 As shown, the circular array device on the left receives the standard test signal. From the partial enlarged image, it can be seen that when the calibration is performed, the angle deviation between the incident test signal and the z-axis causes the deviation of the channel mismatch calibration data.

[0092] Considering the correction signal angle error, let α0, β0, Δα and Δβ represent the azimuth angle, elevation angle and their respective angle deviations of the correction signal, respectively, recorded 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, Represents 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 of 0° to 360° is evenly divided with the interval Δη, so as to obtain the turntable rotation angle set Θ = [0, Δη, 2Δη, …, (360-Δη)]. The turntable rotates according to the angle set Θ, and the data of the standard test signal is collected after each rotation, 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 is 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 we can get,

[0104]

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

[0106]

[0107] Therefore, the correction data of channel mismatch can be accurately calculated by using a simple test measurement method based on a turntable. On this basis, combined with the phase difference calculation formula related to the signal incident azimuth, the appropriate angle interval can be selected according to the requirements of the direction finding index, and the table can be made by numerical calculation to build a phase difference sample library, which greatly reduces the workload of "table making" in actual measurement. In the direction finding process, a simple vector correlation operation is used, instead of using the inverse cosine to calculate the incident angle like the traditional phase interferometer direction finding, and there is no need for the deambiguation process. It can complete all-round direction finding with high direction finding accuracy.

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

[0109] S1. Process steps of 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 of the central element O, and the main channel receives the signals of the elements on the circumference in a time-sharing manner, down-converts them into intermediate frequency signals through the receiving channel, and then samples them;

[0115] S113. The turntable rotates according to the angle set θ, collects data of the standard test signal after each rotation, performs FFT transformation on the two-way sampling data, finds the spectral line position corresponding to the maximum value of the FFT amplitude spectrum, and calculates the phase difference data 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 array elements on the circumference of the circular array and the central array element, forming the phase difference vector data f(α, β, θ). 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 correction result of the channel mismatch;

[0119] S122. Divide the possible area of ​​the incoming wave direction into grids, the grid division interval meets the direction finding error requirements, construct the theoretical phase difference vector of each possible incoming wave direction on 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 perform correlation operation on the phase difference vector data and the data stored in the phase difference sample library according to the decision rule. The purpose is to find the set of data closest to the phase difference vector of the incoming signal from the phase difference sample library, and 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 darkroom.

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

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

[0124] S21 includes the following steps:

[0125] S211. Test system parameter settings: radius-to-wavelength ratio R / λ=3, N independent simulations are performed, and in each simulation, the azimuth angle range is 0°~360°, and the elevation angle range is 0°~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 scenario experiments 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 is set to R / λ=3, the elevation angle is randomly selected from 30° to 90°, the azimuth angle is from 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent tests 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 a function of the signal-to-noise ratio. Figure 5 It can be concluded that the direction finding error of the method of the present invention decreases as the signal-to-noise ratio increases.

[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 is R / λ=3, the elevation angle is randomly selected from 30° to 90°, the azimuth angle is from 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent tests are performed under different sampling point conditions. Figure 6 The curve showing the direction finding error of the method of the present invention as a function of the signal-to-noise ratio. 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] Simulation test conditions: 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 is from 0° to 360°, the number of sample points is 1024, the grid of the phase difference sample library is 0.2°, and 1000 independent tests are performed under different radius-to-wavelength ratios. Figure 7 The curve showing the direction finding error of the method of the present invention as a function of the signal-to-noise ratio. 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 the data set collected in a microwave anechoic chamber, the performance of the rotation-based channel mismatch calibration and the related interferometer direction finding method is evaluated.

[0136] like Figure 8As shown in the figure, data acquisition based on rotation correction of receiving channel mismatch is completed in a darkroom. On the left is the circular array device to be tested, and the rotation around the coordinate axis z is realized by using a turntable. On the right is the standard test source, which transmits a standard test signal. The parameters of the measured data are set as follows: taking the uniform 5-element circular array direction finding as an example, Q=5, the radius-to-wavelength ratio R / λ=3, the standard test source level is 0dBW, the pitch angle range is set to 30°~90°, the azimuth angle range is set to 0°~360°, and the distance between the signal source and the circular array device to be tested is 5m. The step interval is set to 0.5°, and the azimuth angle is evenly divided by this interval to obtain the rotation angle set Θ=[0,0.5°,1°,…,359.5°]. The azimuth angle of the turntable rotation is set according to the angle set Θ. 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 by the measured data are as follows: Fig. 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 is 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: Fig. 9 As shown in (b), Fig. 9 (b) shows the improvement effect of channel mismatch. It should be noted that since the pitch angle deviation of the standard test signal is small, the phase difference value is concentrated in the range of [-π,π]. Even if the phase difference data exceeds the range of [-π,π], the phase ambiguity can be corrected more easily.

[0138] The direction finding error of the measured data is as follows: Fig.10 As shown, from Fig.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 as a limitation of 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 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 rotation-based channel mismatch calibration and correlation interferometer direction finding method; 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 darkroom.

2. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 1, characterized in that: The S1 comprises the following steps: S11. Collecting standard test signals based on a specific rotation mode of the turntable; 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.

3. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 2, characterized in that: The S11 comprises 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)]; S112. When the Q-element circular array estimates the incoming wave direction, the reference channel receives the signal of the central element O, and the main channel receives the signals of the elements on the circumference in a time-sharing manner, down-converts them into intermediate frequency signals through the receiving channel, and then samples them; S113. The turntable rotates according to the angle set θ, collects data of the standard test signal after each rotation, performs FFT transformation on the two-way sampling data, finds the spectral line position corresponding to the maximum value of the FFT amplitude spectrum, and calculates the phase difference data by conjugate multiplication.

4. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 3, characterized in that: The S12 comprises the following steps: S121. Repeat Q times to obtain the phase difference between all array elements on the circumference of the circular array and the central array element, forming the phase difference vector data f(α, β, θ). 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 correction result of the channel mismatch; S122. Divide the possible area of ​​the incoming wave direction into grids, the grid division interval meets the direction finding error requirements, construct the theoretical phase difference vector of each possible incoming wave direction on 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.

5. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 4, characterized in that: 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 correction data of channel mismatch:

6. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 1, characterized in that: The S2 comprises the following steps: S21. Method performance verification: using simulation to verify the performance of the rotation-based channel mismatch calibration and related interferometer direction finding method; S22. Experimental verification: Based on the data set collected in a microwave anechoic chamber, the performance of the rotation-based channel mismatch calibration and the related interferometer direction finding method is evaluated.

7. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 6, characterized in that: The S21 comprises the following steps: S211. Set the test system parameters, and the direction finding error is expressed by the root mean square error RMSE; S212. Conduct simulation scenario experiments based on multiple influencing factors such as signal-to-noise ratio, number of sampling points, and radius-to-wavelength ratio.

8. A rotation-based channel mismatch calibration and correlation interferometer direction finding method as claimed in claim 7, characterized in that: 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 elevation angle range is 0° to 90°; the root mean square error RMSE formula is as follows: Among them, Δα i and Δβ i is the difference between the i-th measured direction and the true direction.

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