Radio signal source direction finding method

Abstract

The invention provides a radio signal source direction finding method. The radio signal source direction finding method comprises the following steps: receiving radio signals by using an interferometer antenna array; performing beam forming on the received radio signals in 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, and detecting the phase differences of other array elements relative to the first interferometer array element to form a reference vector; according to the measured phase difference of the interferometer array element with the longest baseline distance from the first interferometer array element, the incident angle of the radio signal is solved; calculating a virtual phase difference between the array elements of the interferometer according to each incident angle to be verified to obtain a virtual phase difference vector; and solving an included angle between the virtual phase difference vector corresponding to each to-be-verified incident angle and the reference vector, and selecting the to-be-verified incident angle corresponding to the minimum included angle as a final direction finding result. According to the invention, the direction finding precision of the radio signal source is improved while higher receiving gain is obtained.

Description

Technical Field

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

[0002] In the field of radio signal source direction finding and positioning, the direction finding accuracy of the signal source is directly related to the accuracy of positioning, and is one of the key indicators of the entire system. With the continuous development and application of wireless communication technologies, higher requirements are 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 are put forward both in military and civilian fields. In the military field, accurate radio signal source direction finding and positioning is of great significance for electronic warfare, radar detection, etc., and can help one's own side quickly and accurately locate the enemy signal source and provide key information for tactical decision-making. In the civilian aspect, 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 improving their accuracy and adaptability is one of the important research directions in the current wireless communication and electronic engineering fields.

[0004] Specifically, the phase method direction finding technology mainly determines the direction of the signal source by measuring the phase difference of the signal between different antennas. Its advantage is that the principle is relatively simple, but in complex environments such as multipath interference, the phase measurement is easily interfered, resulting in a decrease in direction finding accuracy. The amplitude method direction finding determines the direction of the signal source according to the amplitude difference of the signal on 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 distance or low signal intensity, 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 the signals received by multiple antennas by weighting in the digital domain to form a beam pointing to a specific direction, thereby achieving high-precision direction finding of the signal source. 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 the signal. 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 a certain extent limits its popularization in some resource-constrained or cost-sensitive application scenarios.

[0006] Interferometric 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. Interferometric direction finding measures the phase difference of a signal between two or more antennas and calculates the incident angle of the signal using the interference principle. However, traditional interferometric 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 interferometric direction finding technology may not meet expectations.

[0007] Given the limitations of traditional direction finding methods and the respective advantages and disadvantages of DBF and interferometric 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 interferometers, 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] To this end, 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: Receiving radio signals using an interferometric antenna array; the interferometric antenna array includes a number of non-equispaced interferometric array elements, and each interferometric array element includes a number of antenna elements; Performing beamforming on the received radio signals in each interferometric array element according to the steering vector array of the corresponding interferometric array element; wherein, the steering vector array of the interferometric array element includes the weights of the corresponding channels of each antenna element in the interferometric array element when the beamforming direction is the first direction; Based on the output results of beamforming of each interferometric array element, using the output of the first interferometric array element as a reference, detecting the phase difference of other array elements relative to the first interferometric array element, and forming a reference vector according to the detection results; Calculating the incident angle of the radio signal according to the measured phase difference of the interferometric array element with the longest baseline distance from the first interferometric array element, and the calculation result includes multiple incident angles to be verified; Calculating the virtual phase difference between interferometric 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; Calculating the 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 angle as the final direction finding result.

[0011] The radio signal source direction finding method according to the above technical solution of the present invention may further have the following additional technical features: In the above technical solution, the steering vector array of the interferometer elements is:

[0012] Wherein, represents the steering vector array of the th interferometer element; represents the weight of the th antenna element in the th interferometer element corresponding to the channel, , , represents the total number of interferometer elements, represents the total number of antenna elements in the interferometer element; represents the distance between the th antenna element in the th interferometer element and the reference antenna element; represents the beamforming direction of the interferometer element; represents the speed of light; represents the signal angular frequency.

[0013] In the above technical solution, the step of beamforming the received radio signals at each interferometer element according to the steering vector array of the corresponding interferometer element includes:

[0014] Wherein, represents the output result of beamforming of the th interferometer element,

[0015] In the above technical solution, when performing beamforming on each interferometer element, the first direction is the interferometer normal direction, that is , .

[0016] In the above technical solution, the step of calculating the incident angle of the radio signal according to the measured phase difference of the interferometer element with the longest baseline distance from the first interferometer element includes:

[0017] Wherein, 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; round down to an integer; When When the values are different, 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.

[0018] In the above technical solution, 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 includes: Incident angle to be verified The corresponding virtual phase difference vector is expressed as:

[0019] Among them, the calculation method of any element in the virtual phase difference vector is:

[0020] represents the nth element in the virtual phase difference vector, that is, the phase difference between the nth interferometer array element and the first interferometer array element when the incident angle is ; represents the th spacing between the interferometer array element and the first interferometer array element; among them, the value range of the virtual phase difference between the array elements should satisfy ; Take an integer

[0021] In the above technical solution, obtaining the included angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector includes:

[0022] Among them, represents the included angle operation between two vectors.

[0023] In the above technical solution, in each interferometer array element, the number of antenna units is odd.

[0024] In the above technical solution, the antenna unit is a 360° omnidirectional antenna.

[0025] In the above technical solution, several antenna units in each interferometer array element are arranged at equal intervals.

[0026] In summary, due to the adoption of the above technical features, the beneficial effects of the present invention are: The present invention combines the advantages of two systems, namely DBF and interferometer, to complement each other. The interferometer direction finding can obtain high direction finding accuracy. The direction finding accuracy of the interferometer depends on the length of the longest baseline. Therefore, a larger longest baseline length can be selected to obtain higher direction finding accuracy. By using the DBF arraying method instead of unit antennas, the disadvantage of insufficient gain of the interferometer unit antenna is compensated. Thus, the ability to obtain higher receiving gain while improving the direction finding accuracy is achieved.

[0027] Additional aspects and advantages of the present invention will become apparent in the following description section, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 is a flowchart of a radio signal source direction finding method according to an embodiment of the present invention; Figure 2 is a schematic diagram of the array layout of an interferometer antenna array according to an embodiment of the present invention; Figure 3 is an effect diagram of beam forming of an interferometer array element according to an embodiment of the present invention; Figure 4 is a histogram of direction finding results according to an embodiment of the present invention; Figure 5 is a statistical graph of direction finding ambiguity resolution probability according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order 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.

[0030] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also 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.

[0031] The following refers to Figures 1 to 5 to describe a radio signal source direction finding method according to some embodiments of the present invention.

[0032] Some embodiments of the present application provide a radio signal source direction finding method.

[0033] 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.

[0034] S1. Receive radio signals using an interferometric antenna array; the interferometric antenna array includes a number of interferometer array elements with unequal spacing, and each interferometer array element includes a number of antenna elements.

[0035] In some embodiments, as Figure 2 shown, the interferometric antenna array consists of N interferometer array elements with unequal spacing, where each interferometer array element consists of M (M is an odd number) equally spaced antenna elements.

[0036] In the present disclosure, for simplicity, the following assumptions are made for the algorithm model: there is no error in the spacing between the interferometer array elements and between the antenna elements 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 the azimuth; and each antenna element has a uniform amplitude characteristic in the azimuth.

[0037] Based on the above interferometric antenna array, a mathematical description of the far-field signals received by the interferometric antenna array is as follows: The th antenna element in the th interferometer array element, and the complex signal expression of the received signal is denoted as

[0038] Furthermore, the signals received by the entire interferometric array can be represented in matrix form as:

[0039] 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 in the th

[0040] interferometer array element participate in beamforming is represented as: where represents the steering vector matrix of the th interferometer array element; represents the weight of the channel corresponding to the th antenna element in the th interferometer array element; represents the th The spacing of each antenna unit relative to the reference antenna unit; Indicates the beamforming direction of the interferometer array element; Indicates the speed of light; Indicates the signal angular frequency.

[0041] S2. Beamform the received radio signals at each interferometer array element according to the steering vector array corresponding to the interferometer array element; wherein, the steering vector array of the interferometer array element includes the weights of each antenna unit corresponding channel in the interferometer array element when the beamforming direction is the first direction.

[0042] In some embodiments, the beamforming the received radio signals at each interferometer array element according to the steering vector array corresponding to the interferometer array element includes:

[0043] Wherein, Represents the output result of the beamforming of the nth interferometer array element, Represents the matrix of the signals received by all antenna units in the nth interferometer array element.

[0044] In a specific embodiment, when performing the beamforming of each interferometer array element, the first direction is the interferometer normal direction, that is , . Figure 3 The figure shows the effect diagram of the beamforming of the interferometer array element (sub-array). It can be seen that the beamforming of the interferometer array element can improve the reception gain of the signal.

[0045] S3. Based on the output result of the beamforming of each interferometer array element, taking the output of the first interferometer array element as a reference, detect the phase difference of other array elements relative to the first interferometer array element. And combine into a reference vector ; 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 units, that is .

[0046] 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 , which are respectively denoted as . Wherein, is the phase difference measured between the longest baseline array elements.

[0047] S4. Calculate the incident angle of the radio signal based on the measured phase difference of the interferometer element with the longest baseline distance from the first interferometer element. The calculation results include multiple incident angles to be verified.

[0048] In some embodiments, the calculation method is as follows:

[0049] where 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; take an integer; represents the th interferometer element's spacing relative to the first interferometer element, i.e., the longest baseline distance.

[0050] 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.

[0051] 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.

[0052] different integers take values, then corresponding different incident angle values, denoted as , .

[0053] S5. Calculate the virtual phase difference between interferometer 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 virtual phase difference vector corresponding to the incident angle to be verified is expressed as:

[0054] where the calculation method of any element in the virtual phase difference vector is:

[0055] represents the nth element in the virtual phase difference vector, i.e., the phase difference between the nth interferometer element and the first interferometer element when the incident angle is ; represents the th interferometer element's spacing relative to the first interferometer element.

[0056] Among them, the value range of the virtual phase difference between array elements should satisfy ; Take an integer, that is .

[0057] S6. 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.

[0058] Among them, the calculation method of the angle between the virtual phase difference vector corresponding to the incident angle to be verified and the reference vector is:

[0059] Among them, represents the 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.

[0060] In a specific embodiment, the performance of the direction finding method of the present disclosure is further analyzed and verified. Simulate random phase discrimination errors 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 an incident angle of the simulation signal; the signal frequency range is , and (frequency point 1), (frequency point 2) are used as the 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 gives the histogram statistical results of the direction finding results obtained by using the method of the present invention when the signal frequency is and the signal incident angle is . It can be seen from the figure that only a small part of the wrong direction finding results are in the direction finding results obtained by using 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 is the probability statistical chart 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.

[0061] In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0062] Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for direction finding of a radio signal source, characterized in that, Comprising: Receiving radio signals using an interferometer antenna array; the interferometer antenna array includes a number of non-equispaced interferometer array elements, and each interferometer array element includes a number of antenna elements; Performing beamforming on the received radio signals at each interferometer array element according to the steering vector array of the corresponding interferometer array element; wherein, the steering vector array of the interferometer array element includes the weights of the corresponding channels of each antenna element in the interferometer array element when the beamforming direction is the first direction; Based on the output results of beamforming at 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; 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 results include multiple incident angles to be verified; Calculating the virtual phase difference between 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; Calculating the 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 angle as the final direction finding result.

2. The radio signal source direction finding method according to claim 1, wherein The steering vector array of the interferometer array element is: Among them, represents the steering vector array of the th interferometer array element; represents the weight of the th channel corresponding to the th antenna element in the , , represents the total number of interferometer array elements, represents the total number of antenna elements in the interferometer array element; represents the spacing of the th antenna element relative to the reference antenna element in the th interferometer array element; represents the beamforming direction of the interferometer array element; represents the speed of light; represents the signal angular frequency.

3. The radio signal source direction finding method according to claim 2, wherein The performing beamforming on the received radio signals at each interferometer array element according to the steering vector array of the corresponding interferometer array element includes: Among them, represents the output result of beamforming of the nth interferometer array element, represents the matrix of signals received by all antenna elements in the nth interferometer array element.

4. The radio signal source direction finding method according to claim 3, characterized in that When performing beamforming for each interferometer element, the first direction is the interferometer normal, that is , .

5. The direction finding method of a radio signal source according to claim 3, characterized in that, The 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 includes: 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; When the values are different, corresponding incident angle calculation results can be obtained; all incident angle calculation results that meet the requirements of the direction finding interval are obtained as the incident angles to be verified.

6. The radio signal source direction finding method according to claim 5, wherein The calculating the virtual phase difference between 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 includes: Angle of incidence to be verified The corresponding virtual phase difference vector is expressed as: Wherein, 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, 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; wherein, the value range of the virtual phase difference between array elements should satisfy ; takes an integer.

7. The radio signal source direction finding method according to claim 6, wherein The calculating the angle between the virtual phase difference vector corresponding to each incident angle to be verified and the reference vector includes: Among them, represents the angle operation between two vectors; represents the reference vector.

8. The radio signal source direction finding method according to claim 1, characterized in that, In each interferometer array element, the number of antenna elements is odd.

9. The radio signal source direction finding method according to claim 1, characterized in that The antenna element is a 360° omnidirectional antenna.

10. The radio signal source direction finding method according to claim 1, wherein In each interferometer array element, a number of antenna elements are arranged equispaced.

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