A Direction Finding Method for Uniform Circular Array Phase Interferometer

Abstract

The present invention discloses a direction finding method for a uniform circular array phase interferometer, which includes receiving signals and compensating for the phase differences of each antenna channel, calculating the phase differences according to the baseline combination and constructing multiple groups of complex numbers containing arrival angle information in combination with the ambiguous phase combination, filtering out complex number elements with lower clustering degree by the clustering method and calculating all possible arrival angles, and finally obtaining the estimated value of the signal arrival angle by the energy method. The present invention can quickly obtain an accurate estimated arrival angle and has a low complexity.

Description

Technical Field

[0001] The present invention relates to the technical field of radio signal direction finding, and particularly to a direction finding method for a uniform circular array phase interferometer. Background Art

[0002] The purpose of radio direction finding is to detect the incoming wave direction of a radiation source, which has wide applications in military and civilian fields, such as electronic reconnaissance, radar, secondary radar, mobile communication, indoor positioning, etc. Compared with other direction finding methods, the phase interferometer direction finding method has the advantages of simple structure and easy implementation. Compared with other array forms, the circular array has a higher array surface space utilization rate in two-dimensional direction finding. In most cases, a uniform circular array is generally used.

[0003] Phase ambiguity resolution is the most core technical problem in interferometer direction finding. The algorithm for resolving ambiguity in a circular array is slightly more complex than that in a linear array and generally involves cluster analysis. The performance of the ambiguity resolution method based on clustering (see the literature: Xie Liyun, Wang Guangsong, Dai Xuchu. A new method for resolving ambiguity in two-dimensional direction finding of a circular array phase interferometer [J]. Telemetry and Remote Control, 2007, 28(5): 53-59) is restricted by the threshold setting problem. For a five-element uniform circular array, the ambiguity resolution method based on the improved phase accumulation method and the optimal baseline method (see the literature: Pan Yujian, Zhang Xiaofa, Huang Jingjian, Yang Jun, Yuan Naichang. Improvement and verification of the direction finding performance of a simulated phase discrimination circular array interferometer [J]. Systems Engineering and Electronics, 2015, 37(6): 1237-1240) provides relatively high direction finding performance. However, when applied to a six-element circular array, there are cases where more than one class satisfies the distance minimum requirement. Therefore, to solve this problem, the present invention derives the interferometer direction finding algorithms under different numbers of array elements, different baseline lengths, and different phase difference combinations, and integrates the clustering method and the energy method for ambiguity resolution, which can quickly obtain an accurate estimated arrival angle and has a low complexity. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides a direction finding method for a uniform circular array phase interferometer, which has the technical characteristics of quickly obtaining an accurate estimated arrival angle and having a low complexity.

[0005] In order to achieve the above-mentioned invention purpose, the technical solution adopted to solve its technical problems is as follows:

[0006] A direction finding method for a uniform circular array phase interferometer includes the following steps:

[0007] Step S1: Each antenna of the N-element uniform circular array simultaneously receives a signal of a certain length to eliminate the phase difference of the radio frequency channels;

[0008] Step S2: Calculate the phase difference φ according to the baseline (i, i + p) and the baseline (i + q, i + q + p) i,i+p and φi+q,i+q+p , combine with the fuzzy phase combination to construct multiple groups of complex numbers {f i pq};

[0009] Step S3: Analyze the clustering degree of each element in a certain group of complex numbers with elements in other groups through the clustering method, filter out elements with a lower clustering degree or a modulus value greater than 1, and calculate all possible angles of arrival using the remaining elements;

[0010] Step S4: For each possible angle of arrival, generate a steering vector using the array element position, wavelength, and circular array radius information, and combine it with the vector composed of the signals received by each antenna to generate signal S, calculate the signal energy, and take the angle with the strongest energy as the estimated value.

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

[0012] Step S11: The radius of the N-element uniform circular array is R, the element interval radian ω = 2π / N, numbered 1, 2,..., N in sequence. The elements simultaneously receive the spatial radio signal s(t) with wavelength λ from the elevation angle θ and azimuth angle direction of the antenna array. The received signal r i (t) of each element is:

[0013]

[0014] Step S12: The longer the signal length, the higher the measurement accuracy of the phase difference. When measuring once, the following relationship exists between the measurement accuracy of the phase difference and the signal-to-noise ratio: ε is the signal-to-noise ratio. When measuring L times, the accuracy is improved to

[0015] Step S13: Compensate for the phase difference of the RF channels. The phase difference is calibrated through the signal source in the normal direction of the far field of the antenna array.

[0016] Furthermore, the step S2 includes the following steps:

[0017] Step S21: The baseline (i, i + p) is not parallel to the baseline (i + q, i + q + p). The baseline (i, i + p) is composed of the (mod(i - 1, N)+1)-th and (mod(i + p - 1, N)+1)-th antenna elements, and its phase difference is:

[0018]

[0019] Step S22: Combine the wavelength, the size of the antenna array surface, and the direction finding range. Its maximum phase ambiguity number is The fuzzy phase difference set is {φ i,i+p +2M i,i+p π},

[0020] Similarly, the phase difference of the baseline (i+q, i+q+p) is:

[0021]

[0022] Step S23: Considering the wavelength, antenna array size, and direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i+q,i+q+p + 2M i+q,i+q+p π},

[0023] The sum of the phase differences between the baseline (i, i+p) and the baseline (i+q, i+q+p) is:

[0024]

[0025] The difference between the phase differences between the baseline (i, i+p) and the baseline (i+q, i+q+p) is:

[0026]

[0027] Step S24: Define:

[0028]

[0029]

[0030] Combined with the set of ambiguous phase differences, construct a set of complex numbers:

[0031]

[0032] By changing the value of i (i = 1, 2,..., N), construct N sets of complex numbers.

[0033] Furthermore, the step S3 includes the following steps:

[0034] Step S31: Taking a certain set of complex numbers f i pq as a reference, each element in this set is close to a certain element in the other sets, that is, their clustering degree is the highest. These several close elements correspond to the true direction of the incoming wave. Calculate the distance from each element in this set to each element in the other sets. If the modulus value of an element is greater than 1, the distance between the two is set to the maximum value;

[0035] Step S32: Search for the shortest distance from each element in this set to the elements in the other sets, then sum the N-1 shortest distances corresponding to each element, and find the element class with the smallest sum of distances in this set;

[0036] Step S33: There is at least one element class in the group. Calculate all possible arrival angles according to the elements in the element class:

[0037]

[0038] Further, the step S4 includes the following steps:

[0039] Step S41: For each possible arrival angle Generate an N×1 steering vector A in combination with the wavelength and the positions of the antenna array elements;

[0040] Step S42: Use the signals after eliminating the phase differences of the RF channels for each element to form an N×L-dimensional data vector R;

[0041] Step S43: Calculate S = A H R, obtain a 1×L-dimensional data vector S, and obtain the sum of the energies of its elements P, that is, P = ∑|s i | 2 where s i is the i-th element in the data vector S;

[0042] Step S44: Each possible arrival angle corresponds to an energy. The angle corresponding to the maximum energy is used as the unambiguous arrival angle estimate value.

[0043] Due to the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art:

[0044] A method for direction finding by a uniform circular array phase interferometer of the present invention has the technical characteristics of quickly obtaining an accurate estimated arrival angle and having a low complexity. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings:

[0046] Figure 1 is a schematic flow chart of a method for direction finding by a uniform circular array phase interferometer of the present invention;

[0047] Figure 2 is a schematic diagram of a six-element uniform circular array interferometer of the present invention. Detailed Embodiments

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] As Figure 1 shown, this embodiment discloses a method for direction finding by a uniform circular array phase interferometer, including the following steps:

[0050] Step S1: Each antenna of the N - element uniform circular array simultaneously receives a signal of a certain length to eliminate the phase difference of the radio frequency channels;

[0051] Step S2: According to the baselines (i, i + p) and (i + q, i + q + p), calculate the phase differences φ i,i+p and φ i+q,i+q+p , and combine the ambiguous phase combinations to construct multiple sets of complex numbers {f i pq};

[0052] Step S3: Analyze the clustering degree of each element in a certain set of complex numbers with elements in other sets through the clustering method, filter out elements with a lower clustering degree or a modulus value greater than 1, and calculate all possible arrival angles using the remaining elements;

[0053] Step S4: For each possible arrival angle, generate a steering vector using information such as the element positions, wavelength, and circular array radius, and combine it with the vector composed of the signals received by each antenna to generate a signal S, calculate the signal energy, and take the angle with the strongest energy as the estimated value.

[0054] Further, the step S1 includes the following steps:

[0055] Step S11: The radius of the N - element uniform circular array is R, the element interval radian ω = 2π / N, numbered 1, 2,..., N in sequence. The elements simultaneously receive a spatial radio signal s(t) with a wavelength of λ from the elevation angle θ and azimuth direction of the antenna array. The received signal r i (t) of each element is:

[0056]

[0057] Step S12: The longer the signal length, the higher the measurement accuracy of the phase difference. When measuring once, the relationship between the measurement accuracy of the phase difference and the signal - to - noise ratio is as follows: ε is the signal - to - noise ratio. When measuring L times, the accuracy is improved to

[0058] Step S13: Compensate the phase difference of the RF channels. The phase difference is calibrated by a signal source in the normal direction of the far field of the antenna array. Since there is no phase difference introduced by the incident angle in the signals received by each antenna at this time, the analyzed phase difference is caused by the RF channels and components.

[0059] Further, the step S2 includes the following steps:

[0060] Step S21: The baseline (i, i + p) is not parallel to the baseline (i + q, i + q + p). The baseline (i, i + p) is composed of the (mod(i - 1, N)+1)-th and the (mod(i + p - 1, N)+1)-th antenna elements, and its phase difference is:

[0061]

[0062] Step S22: Combining the wavelength, the size of the antenna array surface, and the direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i,i+p +2M i,i+p π},

[0063] Similarly, the phase difference of the baseline (i + q, i + q + p) is:

[0064]

[0065] Step S23: Combining the wavelength, the size of the antenna array surface, and the direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i+q,i+q+p +2M i+q,i+q+p π},

[0066] The sum of the phase differences between the baseline (i, i + p) and the baseline (i + q, i + q + p) is:

[0067]

[0068] The difference between the phase differences of the baseline (i, i + p) and the baseline (i + q, i + q + p) is:

[0069]

[0070] Step S24: Define:

[0071]

[0072]

[0073] Combining the set of ambiguous phase differences, construct a set of complex numbers:

[0074]

[0075] By varying the value of i (i = 1, 2,..., N), N groups of complex numbers are constructed.

[0076] Furthermore, the step S3 includes the following steps:

[0077] Step S31: Taking a certain group of complex numbers f i pq as a reference, each element in this group is close to a certain element in the other groups, that is, their clustering degree is the highest. These several mutually close elements correspond to the true direction of the incoming wave. Calculate the distance from each element in this group to each element in the other groups. If the modulus value of an element is greater than 1, the distance between the two is set to the maximum value;

[0078] Step S32: Search for the shortest distance from each element in this group to the elements in the other groups, and then sum the N - 1 shortest distances corresponding to each element to find the element class with the smallest sum of distances in this group;

[0079] Step S33: There is at least one element class in this group. Calculate all possible arrival angles based on the elements in the element class:

[0080]

[0081] Furthermore, the step S4 includes the following steps:

[0082] Step S41: For each possible arrival angle generate an N×1 steering vector A in combination with the wavelength and the positions of the antenna array elements;

[0083] Step S42: Use the signals after eliminating the phase differences of the RF channels at each element to form an N×L - dimensional data vector R;

[0084] Step S43: Calculate S = A H R to obtain a 1×L - dimensional data vector S, and obtain the sum of the energies of its elements P, that is, P = ∑|s i | 2 , s i being the i - th element in the data vector S;

[0085] Step S44: Each possible arrival angle corresponds to an energy, and the angle corresponding to the maximum energy is used as the unambiguous arrival angle estimate value.

[0086] Example:

[0087] A six - element (N = 6) uniform circular array is as Figure 2As shown, the radius R = λ / 2, the element interval radian ω = π / 3, and they are numbered 1, 2,..., 6 in sequence. Define the elevation angle as the angle between the signal incident direction and the XOY plane, and define the azimuth angle as the angle between the projection of the signal incident direction on the XOY plane and the X-axis. The elements simultaneously receive the spatial radio signal s(t) with a wavelength of λ from the direction of the elevation angle θ and azimuth angle of the antenna array, and the received signal r i (t) of each element is:

[0088]

[0089] When the signal length L = 1024, the measurement accuracy of the phase difference is

[0090] Compensate for the phase difference of the RF channels. The phase difference is calibrated by the signal source in the normal direction of the far field of the antenna array. Because there is no phase difference introduced by the incident angle in the received signals of each antenna at this time, the analyzed phase difference is caused by the RF channels and components.

[0091] p = 3, q = 1;

[0092] The baseline (i, i + 3) is not parallel to the baseline (i + 1, i + 4). The baseline (i, i + 3) is composed of the (mod(i - 1, 6)+1)-th and (mod(i + 3 - 1, 6)+1)-th antenna elements, and its phase difference is:

[0093]

[0094] Combined with the wavelength, the antenna array size, and the direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i,i+3 +2M i,i+3 π}, M i,i+3 ∈[-1, 1];

[0095] Similarly, the phase difference of the baseline (i + 1, i + 4) is:

[0096]

[0097] Combined with the wavelength, the antenna array size, and the direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i+1,i+4 +2M i+1,i+4 π}, M i+1,i+4 ∈[-1, 1];

[0098] The sum of the phase differences of the baseline (i, i + 3) and the baseline (i + 1, i + 4) is:

[0099]

[0100] The difference between the phase differences of the baseline (i, i + 3) and the baseline (i + 1, i + 4) is:

[0101]

[0102] Definition:

[0103]

[0104]

[0105] Combined with the set of ambiguous phase differences, construct a set of complex numbers:

[0106]

[0107] By varying the value of i (i = 1, 2,..., 6), construct 6 sets of complex numbers.

[0108] Taking the first set of complex numbers f1 pq as a reference, each element in this set is close to a certain element in the other sets, that is, they have the highest clustering degree. These several close elements correspond to the true direction of the incoming wave. Calculate the distance from each element in this set to each element in the other sets. If the modulus value of an element is greater than 1, the distance between the two is set to the maximum value;

[0109] Search for the shortest distance from each element in this set to the elements in the other sets, and then sum the 5 shortest distances corresponding to each element. Find the element class with the smallest sum of distances in this set;

[0110] There is at least one element class in this set. Calculate all possible arrival angles based on the elements in the element class:

[0111]

[0112] For each possible arrival angle Combine the wavelength and the positions of the antenna array elements to generate a 6×1 steering vector A;

[0113] Use the signals after eliminating the phase differences of the RF channels by each element to form a 6×1024 - dimensional data vector R;

[0114] Calculate S = A H R, obtain a 1×1024 - dimensional data vector S, and obtain the sum of the energies of its elements P, that is, P = ∑|s i | 2 , s i is the i - th element in the data vector S;

[0115] Each possible arrival angle corresponds to an energy. The angle corresponding to the maximum energy is used as the unambiguous arrival angle estimation value.

[0116] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A direction finding method for a uniform circular array phase interferometer, characterized in that, It includes the following steps: Step S1: Each antenna of the N-element uniform circular array simultaneously receives a signal of a certain length to eliminate the phase difference of the RF channels; Step S2: Calculate the phase difference φ based on the baselines (i, i + p) and (i + q, i + q + p). i,i+p and φ i+q,i+q+p , and construct multiple sets of complex numbers {f i pq} by combining the ambiguous phase combinations; The following steps are included in the said step S2: Step S21: The baseline (i, i + p) is not parallel to the baseline (i + q, i + q + p). The baseline (i, i + p) is composed of the (mod(i - 1, N)+1)-th and the (mod(i + p - 1, N)+1)-th antenna elements, and its phase difference is: where R is the radius of an N-element uniform circular array, the angular spacing ω of the array elements is 2π / N, and the elements are numbered 1, 2, ..., N in sequence, and r i (t) is the received signal of each array element; Step S22: Considering the wavelength, antenna array size, and direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i,i+p + 2M i,i+p π}, Similarly, the phase difference of the baseline (i + q, i + q + p) is: where λ is the wavelength and θ is the elevation angle, and is the azimuth angle; Step S23: Considering the wavelength, antenna array size, and direction finding range, its maximum phase ambiguity number is The set of ambiguous phase differences is {φ i+q,i+q+p + 2M i+q,i+q+p π}, The sum of the phase differences between the baseline (i, i + p) and the baseline (i + q, i + q + p) is: The difference between the phase differences of the baseline (i, i + p) and the baseline (i + q, i + q + p) is: Step S24: Define: Combined with the set of ambiguous phase differences, construct a set of complex numbers: By changing the value of i, i = 1, 2, ……, N, construct N sets of complex numbers; Step S3: Analyze the clustering degree of each element in a set of complex numbers with elements in other sets through the clustering method, filter out elements with lower clustering degree or modulus greater than 1, and calculate all possible arrival angles using the remaining elements; Step S4: For each possible arrival angle, generate a steering vector using the element positions, wavelength, and circular array radius information, and combine it with the vector composed of the signals received by each antenna to generate signal S, calculate the signal energy, and take the angle with the strongest energy as the estimated value.

2. The method for direction finding by using a uniform circular array phase interferometer according to claim 1, characterized in that, The following steps are included in the said step S1: Step S11: The array elements simultaneously receive the spatial radio signal s(t) with wavelength λ incident from the elevation angle θ and azimuth angle of the antenna array of the antenna array. The received signal r i (t) of each array element is expressed as: Step S12: The longer the signal length is, the higher the measurement accuracy of the phase difference is. During single measurement, the following relationship exists between the measurement accuracy of the phase difference and the signal-to-noise ratio: ε is the signal-to-noise ratio. During L measurements, the accuracy is improved to Step S13: Compensate the phase difference of the RF channels, and the phase difference is calibrated by the signal source in the far-field normal direction of the antenna array.

3. A method for direction finding using a uniform circular array phase interferometer according to claim 2, characterized in that, The following steps are included in the said step S3: Step S31: Using a certain set of complex numbers f i pq as a reference, each element in this set is close to a certain element in the remaining sets, that is, their clustering degree is the highest. These several mutually close elements correspond to the true direction of the incoming wave. Calculate the distance from each element in this set to each element in the remaining sets. If the modulus value of an element is greater than 1, the distance between the two is set to a maximum value; Step S32: Search for the shortest distance from each element in this set to the elements in the remaining sets, then sum the N - 1 shortest distances corresponding to each element, and find the element class with the smallest sum of distances in this set; Step S33: There is at least one element class in this set. Calculate all possible arrival angles according to the elements in the element class:

4. A method for direction finding by a uniform circular array phase interferometer according to claim 3, characterized in that, The following steps are included in the said step S4: Step S41: For each possible angle of arrival generate an N×1 steering vector A in combination with the wavelength and the positions of the antenna array elements; Step S42: Use the signals of each element after eliminating the phase difference of the RF channels to form an N×L-dimensional data vector X; Step S43: Calculate S = A H X to obtain a 1×L dimensional data vector S, and obtain its element energy sum P, that is, P = ∑|s i | 2 , where s i is the i-th element in the data vector S; Step S44: Each possible arrival angle corresponds to an energy. The angle corresponding to the maximum energy is used as the unambiguous estimated arrival angle.

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