A method for direction finding of a radio signal source

Abstract

The present invention provides a method for direction finding of a radio signal source, comprising: receiving a radio signal using an interferometer antenna array; respectively performing beamforming on the received radio signal at each interferometer array element according to the steering vector array of the corresponding interferometer array element; taking the output of the first interferometer array element as a reference, detecting the phase difference of other array elements relative to the first interferometer array element to form a reference vector; calculating the incident angle of the radio signal according to the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element; calculating the virtual phase difference between the interferometer array elements according to each incident angle to be verified, obtaining a virtual phase difference vector; obtaining the included angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector, and selecting the incident angle to be verified corresponding to the minimum included angle as the final direction finding result. The present invention improves the direction finding accuracy of the radio signal source while obtaining a higher receiving gain.

Description

Technical Field

[0001] The present invention relates to the technical field of signal measurement, and more specifically, to a method for direction finding of radio signal sources. Background Art

[0002] In the field of direction finding and positioning of radio signal sources, the direction finding accuracy of signal sources directly affects the positioning accuracy and is one of the key indicators of the entire system. With the continuous development and application of wireless communication technologies, higher requirements have been put forward for the direction finding and positioning accuracy of radio signal sources. Traditional direction finding methods, such as the phase method, amplitude method, etc., although having certain advantages in specific scenarios, still have certain limitations and are difficult to meet the high-sensitivity and high-precision direction finding requirements in complex environments.

[0003] Higher requirements for the direction finding and positioning accuracy of radio signal sources have been put forward both in military and civilian applications. In the military field, accurate direction finding and positioning of radio signal sources are of great significance for electronic warfare, radar detection, etc., and can help one's own side quickly and accurately locate enemy signal sources and provide key information for tactical decisions. In civilian applications, such as the optimization of wireless communication networks, air traffic control, etc., high-precision direction finding and positioning technologies can effectively improve the performance and safety of the system and ensure the stability and reliability of communication. Therefore, continuously exploring and improving direction finding and positioning technologies and enhancing their accuracy and adaptability are important research directions in the current wireless communication and electronic engineering fields.

[0004] Specifically, the phase method for direction finding mainly determines the direction of the signal source by measuring the phase difference between signals at different antennas. Its advantage is that the principle is relatively simple, but in complex environments such as multipath interference, phase measurement is easily interfered, resulting in a decrease in direction finding accuracy. The amplitude method for direction finding determines the direction of the signal source based on the amplitude difference of the signal at different antennas. Although it is relatively easy to implement, its accuracy is limited by the antenna pattern and the amplitude change of the signal, and in the case of long distances or low signal intensities, the amplitude difference may not be obvious, affecting the direction finding effect.

[0005] Digital beamforming (DBF) direction finding technology, as an advanced digital signal processing technology, has received extensive attention in recent years. It synthesizes signals received by multiple antennas in the digital domain through weighting to form a beam pointing in a specific direction, thereby achieving high-precision direction finding of signal sources. The DBF technology has advantages such as high precision and high sensitivity, and can effectively improve the signal-to-noise ratio and anti-interference ability of signals. However, its implementation complexity is relatively high, requiring a large amount of computing resources and complex hardware support, resulting in a relatively high cost, which to some extent limits its promotion in some resource-constrained or cost-sensitive application scenarios.

[0006] The interferometer direction-finding technology has occupied a place in the field of radio signal source direction-finding due to its simple principle, small computational complexity, and ease of implementation. The interferometer direction-finding calculates the incident angle of the signal by measuring the phase difference between the signals received by two or more antennas and using the interference principle. However, the traditional interferometer direction-finding technology usually has insufficient sensitivity compared to DBF. High-precision direction-finding can be achieved through long baselines. In some application scenarios, the performance of the interferometer direction-finding technology may not meet the expectations.

[0007] In view of the limitations of traditional direction-finding methods and the respective advantages and disadvantages of DBF and interferometer direction-finding technologies, researchers have been exploring how to combine the advantages of both. There is an urgent need for a direction-finding method that can combine DBF and interferometers. This method aims to make full use of the high precision of DBF and the simple and easy-to-implement characteristics of the interferometer, overcome the deficiencies when used alone, and thus reduce the system complexity and cost while ensuring the direction-finding accuracy, which has important practical application value. Summary of the Invention

[0008] The present invention aims to at least solve one of the above technical problems existing in the prior art.

[0009] For this reason, the present invention provides a method for direction-finding of radio signal sources.

[0010] The present invention provides a method for direction-finding of radio signal sources, including:

[0011] Receiving radio signals using an interferometer antenna array; the interferometer antenna array includes a plurality of non-equispaced interferometer array elements, and each interferometer array element includes a plurality of antenna units;

[0012] Performing beamforming on the received radio signals in each interferometer array element according to the steering vector matrix of the corresponding interferometer array element; wherein, the steering vector matrix of the interferometer array element includes the weights of the corresponding channels of each antenna unit in the interferometer array element when the beamforming direction is the first direction;

[0013] Based on the output results of beamforming of each interferometer array element, taking the output of the first interferometer array element as a reference, detecting the phase difference of other array elements relative to the first interferometer array element, and forming a reference vector according to the detection results;

[0014] Calculating the incident angle of the radio signal according to the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element, and the calculation result includes multiple incident angles to be verified;

[0015] Calculating the virtual phase difference between the interferometer array elements according to each incident angle to be verified, and obtaining the virtual phase difference vector corresponding to the incident angle to be verified;

[0016] Obtain the angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector, and select the incident angle to be verified corresponding to the minimum angle as the final direction finding result.

[0017] According to the radio signal source direction finding method of the above technical solution of the present invention, the following additional technical features may also be provided:

[0018] In the above technical solution, the steering vector array of the interferometer array element is:

[0019]

[0020] Where represents the steering vector array of the th interferometer array element; represents the weight of the th antenna element in the th interferometer array element corresponding to the channel, , , represents the total number of interferometer array elements, represents the total number of antenna elements in the interferometer array element; represents the distance between the th antenna element in the th interferometer array element and the reference antenna element; represents the beamforming direction of the interferometer array element; represents the speed of light; represents the signal angular frequency.

[0021] In the above technical solution, the beamforming of the received radio signals respectively in each interferometer array element according to the steering vector array of the corresponding interferometer array element includes:

[0022]

[0023] Where represents the output result of the beamforming of the th interferometer array element,

[0024] In the above technical solution, when performing the beamforming of each interferometer array element, the first direction is the interferometer normal direction, that is , .

[0025] In the above technical solution, the calculation of the incident angle of the radio signal according to the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element includes:

[0026]

[0027] Among them, represents the incident angle; represents the phase difference of the interferometer element with the longest baseline distance from the first interferometer element relative to the first interferometer element; takes an integer;

[0028] When has different values, corresponding incident angle calculation results can be obtained; all the incident angle calculation results that meet the requirements of the direction finding interval are obtained as the incident angles to be verified.

[0029] In the above technical solution, the calculating the virtual phase difference between interferometer elements according to each incident angle to be verified and obtaining the virtual phase difference vector corresponding to the incident angle to be verified includes:

[0030] The incident angle to be verified The corresponding virtual phase difference vector is expressed as:

[0031]

[0032] Among them, the calculation method of any element in the virtual phase difference vector is:

[0033]

[0034] represents the nth element in the virtual phase difference vector, that is, when the incident angle is the phase difference between the nth interferometer element and the first interferometer element; represents the th interferometer element relative to the spacing of the first interferometer element; among them, the value range of the virtual phase difference between elements should satisfy ; takes an integer

[0035] In the above technical solution, the obtaining the included angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector includes:

[0036]

[0037] Among them, represents the included angle operation between two vectors.

[0038] In the above technical solution, in each interferometer element, the number of antenna elements is odd.

[0039] In the above technical solution, the antenna element is a 360° omnidirectional antenna.

[0040] In the above technical solution, several antenna elements in each interferometer array element are arranged at equal intervals.

[0041] In summary, due to the adoption of the above technical features, the beneficial effects of the present invention are as follows:

[0042] Through the complementary advantages of the combination of the two systems of DBF and interferometer, the present invention can obtain a higher direction-finding accuracy by using interferometer direction-finding. The direction-finding accuracy of the interferometer depends on the length of the longest baseline. Therefore, a higher direction-finding accuracy can be obtained by selecting a larger longest baseline length; by replacing the unit antenna with the DBF arraying method, the disadvantage of insufficient gain of the unit antenna of the interferometer is compensated. Thus, the ability to obtain a higher receiving gain while improving the direction-finding accuracy is achieved.

[0043] The additional aspects and advantages of the present invention will become obvious in the following description part, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0045] Figure 1 is a flowchart of a radio signal source direction-finding method according to an embodiment of the present invention;

[0046] Figure 2 is a schematic diagram of the array layout of an interferometer antenna array according to an embodiment of the present invention;

[0047] Figure 3 is an effect diagram of beamforming of an interferometer array element according to an embodiment of the present invention;

[0048] Figure 4 is a histogram of direction-finding results according to an embodiment of the present invention;

[0049] Figure 5 is a statistical graph of direction-finding ambiguity resolution probability according to an embodiment of the present invention. [[ID=�5]] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] In order to be able to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below in conjunction with the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0051] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0052] The following refers toFigures 1 to 5 Describe a radio signal source direction finding method provided according to some embodiments of the present invention.

[0053] Some embodiments of the present application provide a radio signal source direction finding method.

[0054] The first embodiment of the present invention proposes a radio signal source direction finding method, as Figure 1 shown, including the following steps S1 - S6.

[0055] S1. Use an interferometer antenna array to receive radio signals; the interferometer antenna array includes a number of non - equally spaced interferometer array elements, and each interferometer array element includes a number of antenna elements.

[0056] In some embodiments, as Figure 2 shown, the interferometer antenna array is composed of N non - equally spaced interferometer array elements, where each interferometer array element is composed of M (M is an odd number) equally spaced antenna elements.

[0057] In this disclosure, for simplicity, the following assumptions are made for the algorithm model: there is no error in the spacing between each interferometer array element and each antenna element within the array element; the characteristics of the antenna in the pitch direction are not considered; each antenna element is an ideal 360° omnidirectional antenna in azimuth; each antenna element has a uniform amplitude characteristic in azimuth.

[0058] Based on the above - mentioned interferometer antenna array, a mathematical description of the far - field signal received by the interferometer antenna array is as follows:

[0059] The th antenna element in the th interferometer array element, the complex signal expression of the received signal is denoted as

[0060]

[0061] Furthermore, the signals received by the entire interferometer array can be represented in matrix form as:

[0062]

[0063] The weight coefficients of each channel in beamforming can be combined into a matrix form (steering vector matrix). Then, the steering vector matrix when all antenna element channels of the th interferometer array element participate in beamforming in the interferometer array element beamforming is represented as:

[0064]

[0065] Among them, represents the The steering vector array of each interferometer element; Denote the th weight value of the corresponding channel of the , , Denote the total number of interferometer elements, Denote the total number of antenna elements in the interferometer element; Denote the th spacing of the th antenna element relative to the reference antenna element in the th interferometer element; Denote the beamforming direction of the interferometer element;

[0066] S2. Respectively perform beamforming on the received radio signals at each interferometer element according to the steering vector array of the corresponding interferometer element; wherein, the steering vector array of the interferometer element includes the weight values of the corresponding channels of each antenna element in the interferometer element when the beamforming direction is the first direction.

[0067] In some embodiments, the performing beamforming on the received radio signals at each interferometer element according to the steering vector array of the corresponding interferometer element includes:

[0068]

[0069] Wherein, Denote the output result of beamforming of the th interferometer element,

[0070] In a specific embodiment, when performing beamforming on each interferometer element, the first direction is the interferometer normal direction, that is , . Figure 3 The figure shows the effect diagram of beamforming of the interferometer element (sub-array). It can be seen that the reception gain of the signal can be improved through the beamforming of the interferometer element.

[0071] S3. Based on the output result of beamforming of each interferometer element, taking the output of the first interferometer element as a reference, detect the phase difference of other elements relative to the first interferometer element. And combine into a reference vector ;

[0072] In a specific embodiment, the interferometer antenna array is selected as a 4-element three-baseline array, and each interferometer array element is composed of 3 antenna elements, that is .

[0073] Based on the beamforming output of 4 interferometer array elements , and taking the output of the first array element as a reference, detect the phase difference of other array elements relative to the first array element , and denote them as . Among them, is the phase difference measured between the longest baseline array elements.

[0074] S4. According to the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element, calculate the incident angle of the radio signal, and the calculation result includes multiple incident angles to be verified.

[0075] In some embodiments, the calculation method is as follows:

[0076]

[0077] Among them, represents the incident angle; represents the phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element relative to the first interferometer array element; takes an integer; represents the th interferometer array element's spacing relative to the first interferometer array element, that is, the longest baseline distance.

[0078] When has different values, corresponding incident angle calculation results can be obtained; obtain all incident angle calculation results that meet the direction finding interval requirements as the incident angles to be verified.

[0079] Specifically, the incident angle to be verified needs to satisfy , is the lower limit of the direction finding interval, is the upper limit of the direction finding interval.

[0080] For different integer values, there are corresponding different incident angle values, which are respectively denoted as .

[0081] S5. Calculate the virtual phase difference between the interferometer array elements according to each incident angle to be verified, and obtain the virtual phase difference vector corresponding to the incident angle to be verified;

[0082] The incident angle to be verified The corresponding virtual phase difference vector is expressed as:

[0083]

[0084] Among them, the calculation method of any element in the virtual phase difference vector is:

[0085]

[0086] represents the nth element in the virtual phase difference vector, that is, when the incident angle is the phase difference between the nth interferometer array element and the first interferometer array element; represents the spacing of the nth interferometer array element relative to the first interferometer array element.

[0087] Among them, the value range of the virtual phase difference between array elements should satisfy ; takes an integer, that is .

[0088] S6. Obtain the included angle between the virtual phase difference vector corresponding to each to-be-verified incident angle and the reference vector, and select the to-be-verified incident angle corresponding to the minimum included angle as the final direction-finding result.

[0089] Among them, the calculation method of the included angle between the virtual phase difference vector corresponding to the to-be-verified incident angle and the reference vector is:

[0090]

[0091] Among them, represents the included angle operation between two vectors; the numerator term represents the dot product operation of two vectors; the denominator term represents the scalar product of the moduli of two vectors.

[0092] In a specific embodiment, the performance of the direction-finding method of the present disclosure is further analyzed and verified. Random phase discrimination errors are simulated for each channel, and the random range of the phase discrimination error is ; the direction-finding interval is , in the interval, every is used as a simulation signal incident angle; the signal frequency range is , and (frequency point 1), (frequency point 2) are used as simulation frequency points. At each pair of signal incident angles and signal frequency points, random phase discrimination errors are generated, and 1000 Monte Carlo simulations are performed, and the direction-finding simulation results are statistically analyzed. Figure 4 is the histogram of the direction-finding results, which shows that the signal frequency is , the incident angle of the signal is The histogram statistical result of the direction finding result obtained by using the method of the present invention when. It can be seen from the figure that only a small part of the wrong direction finding results in the direction finding results obtained by the method of the present invention, and most of the direction finding results are concentrated near the true incident angle of the signal. Figure 5 It is a statistical chart of the probability of direction finding ambiguity resolution. The present direction finding method shows good direction finding performance in the presence of phase discrimination errors in each channel.

[0093] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0094] Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for finding the direction of a radio signal source, characterized in that: include: Using an interferometer antenna array to receive radio signals; the interferometer antenna array includes a plurality of unequally spaced interferometer array elements, each of which includes a plurality of antenna units; performing beamforming on the received radio signal at each interferometer array element according to a steering vector array of the corresponding interferometer array element; wherein the steering vector array of the interferometer array element includes a weight value corresponding to a channel of each antenna unit in the interferometer array element when the beamforming direction is a first direction; Based on the output results of the beamforming of each interferometer array element, the phase differences of other array elements relative to the first interferometer array element are detected with the output of the first interferometer array element as a reference, and a reference vector is formed according to the detection results; The incident angle of the radio signal is solved based on the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element, and the solution results include multiple incident angles to be verified; Calculate the virtual phase difference between interferometer array elements according to each incident angle to be verified, and obtain the virtual phase difference vector corresponding to the incident angle to be verified; The angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector is calculated, and the incident angle to be verified corresponding to the minimum angle is selected as the final direction finding result.

2. The method for finding the direction of a radio signal source according to claim 1, wherein: The steering vector array of the interferometer array element is: in, Indicates the Steering vector array of interferometer elements; Indicates the The interferometer array element The weight of the channel corresponding to each antenna unit, , , represents the total number of interferometer array elements, represents the total number of antenna elements in the interferometer array; Indicates the The interferometer array element The distance between the antenna units and the reference antenna unit; represents the beamforming pointing direction of the interferometer array element; represents the speed of light; Indicates the signal angular frequency.

3. The method for finding the direction of a radio signal source according to claim 2, wherein: The step of beamforming the received radio signal at each interferometer array element according to the steering vector array of the corresponding interferometer array element comprises: in, represents the output result of the beamforming of the nth interferometer array element, The matrix representing the received signals of all antenna units in the nth interferometer array element.

4. The method for finding the direction of a radio signal source according to claim 3, wherein: When performing beamforming for each interferometer array element, the first direction is the interferometer normal, that is, , .

5. The method for finding the direction of a radio signal source according to claim 3, wherein: The calculating the incident angle of the radio signal according to the measured phase difference of the interferometer array element having the longest baseline distance from the first interferometer array element comprises: Among them, Indicates the The distance between the first interferometer array element and the first interferometer array element, that is, the longest baseline distance; represents the angle of incidence; It represents the phase difference of the interferometer element with the longest baseline distance to the first interferometer element relative to the first interferometer element; Take the integer; when When the values are different, the corresponding incident angle solution results can be obtained; all incident angle solution results that meet the direction finding interval requirements are obtained as the incident angle to be verified.

6. The method for finding the direction of a radio signal source according to claim 5, wherein: The step of calculating the virtual phase difference between interferometer array elements according to each incident angle to be verified and obtaining a virtual phase difference vector corresponding to the incident angle to be verified includes: Incident angle to be verified The corresponding virtual phase difference vector is expressed as: The calculation method of any element in the virtual phase difference vector is: represents the virtual phase difference vector; Represents the nth element in the virtual phase difference vector, that is, the incident angle is When , the phase difference between the nth interferometer array element and the first interferometer array element; Indicates the The distance between the interferometer array elements and the first interferometer array element; the virtual phase difference value range between the array elements should satisfy ; Take the integer.

7. The method for finding the direction of a radio signal source according to claim 6, wherein: The step of obtaining the angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector includes: in, Represents the angle operation between two vectors; represents the reference vector.

8. The method for finding the direction of a radio signal source according to claim 1, wherein: In each interferometer array element, the number of antenna units is odd.

9. The method for finding the direction of a radio signal source according to claim 1, wherein: The antenna unit is a 360° omnidirectional antenna.

10. The method for finding the direction of a radio signal source according to claim 1, wherein: Several antenna units in each interferometer array element are arranged at equal intervals.

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