Radio frequency direction finding method and system
阅读说明：本技术 一种射频测向方法及系统 (Radio frequency direction finding method and system ) 是由 左乐 廖骥 程鹏 李建军 成志强 王建水 聂剑坤 应钱诚 刘颖 张浩斌 于 2020-06-19 设计创作，主要内容包括：本发明提供了一种射频测向方法,包括：对于N元均匀圆阵天线,通过鉴相器获得每一路天线与第一路天线的电压相位差；在来波以仰角为0°入射圆阵天线时,记录各相位差为初始相位差；根据电压相位差和初始相位差构造每一路天线对应的复数；根据仰角<Image he="80" wi="76" file="DDA0002547905120000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>和方位角<Image he="81" wi="111" file="DDA0002547905120000012.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>计算每路天线与第一路天线的理论相位差；引入向量X和方向向量G,结合构造的复数计算迭代次数k+1的二维入射角的仰角<Image he="80" wi="128" file="DDA0002547905120000013.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>和方位角<Image he="79" wi="154" file="DDA0002547905120000014.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>计算迭代次数为k+1与迭代次数为k的二维入射角之差,并于门限值比较,小于门限值进入输出仰角和方位角；否则,k的值加1,再次计算理论相位差。本方法优势在于采用复数运算,避免了相位模糊问题,提高了测向精度高；采用迭代算法,避免了逻辑判断等运算。(The invention provides a radio frequency direction finding method, which comprises the following steps: for the N-element uniform circular array antenna, the voltage phase difference between each path of antenna and the first path of antenna is obtained through a phase discriminator; when incoming waves enter the circular array antenna with the elevation angle of 0 degree, recording each phase difference as an initial phase difference; constructing a plurality number corresponding to each antenna according to the voltage phase difference and the initial phase difference; according to the elevation angle And azimuth angle Calculating the theoretical phase difference between each antenna and the first antenna; introducing a vector X and a direction vector G, and calculating the elevation angle of the two-dimensional incident angle of the iteration number k +1 by combining the constructed complex number And azimuth angle Calculating the difference between the two-dimensional incident angles with the iteration times of k +1 and the iteration times of k, comparing the difference with a threshold value, and outputting an elevation angle and an azimuth angle when the difference is smaller than the threshold value; otherwise, the value of k is added by 1, and the theoretical phase difference is calculated again. The method has the advantages that complex operation is adopted, the phase ambiguity problem is avoided, and the direction finding precision is improved; and an iterative algorithm is adopted, so that operations such as logic judgment and the like are avoided.)
1. A radio frequency direction finding method is characterized by comprising the following processes:
step 1, for an N-element uniform circular array antenna, obtaining a voltage phase difference between each antenna and a first antenna through a phase discriminator;
step 2, when incoming waves enter the circular array antenna with the elevation angle of 0 degree, recording the voltage phase difference of each antenna and the first antenna obtained through the phase discriminator as an initial phase difference
Step 3, constructing a plurality number corresponding to each antenna according to the voltage phase difference and the initial phase difference;
step 4, setting the initial elevation angle asInitial azimuth angle ofThe iteration number k is 0;
step 5, when the iteration number is k, according to the elevation angleAnd azimuth angleCalculating the phase difference between each antenna and the first antenna;
step 6, introducing a vector X and a direction vector G, and calculating the elevation angle of the two-dimensional incident angle of the iteration times k +1 by combining the constructed complex number
Step 7, calculating the difference between the two-dimensional incident angles with the iteration times k +1 and the iteration times k, comparing the result with a threshold value, and entering step 8 if the result is smaller than the threshold value; otherwise, adding 1 to the value of the iteration times k, and entering the step 5;
step 8, outputting the two-dimensional incident angleAndas the elevation and azimuth of the radiation source.
2. The radio frequency direction finding method according to claim 1, wherein in step 1, N is not less than 3 in the N-element uniform circular array antenna.
3. The radio frequency direction finding method according to claim 2, wherein in the step 3, the specific method for constructing the plurality of signals is:
wherein, ViRepresents the complex number, phi, corresponding to the ith antennai1The voltage phase difference between the ith antenna and the first antenna is shown,the initial phase difference between the ith antenna and the first antenna is shown when the incoming wave enters the circular array antenna with the elevation angle of 0 degree; 2,3,4, …, N, Vi＝1，i＝1。
4. The radio frequency direction finding method according to claim 3, wherein in the step 5, the specific method for calculating the theoretical phase difference between each antenna and the first antenna is as follows:
wherein the content of the first and second substances,
5. The radio frequency direction finding method according to claim 4, wherein in the step 6, an elevation angle of a two-dimensional incident angle is calculatedAnd azimuth angle
step 61, setting vector X(k)＝[x1,x2]T
Wherein T represents a matrix transpose;
step 62, calculating a direction vector, G ═ G1,g2]T(ii) a Wherein:
step 63, updating the vector X to obtain the value of the vector X at the (k + 1) th time;
X(k+1)＝X(k)+G
wherein the content of the first and second substances,
step 64, according to X(k+1)Calculating the elevation angle of the k +1 st two-dimensional incident angleAnd azimuth angle
Wherein, | | represents a complex modulus, real represents the operation of taking a complex real part, and arg represents the operation of solving a complex phase.
6. The radio frequency direction finding method according to claim 5, wherein in the step 7, the specific method for calculating the difference between the iteration number k +1 and the two-dimensional incident angle with the iteration number k is as follows:
wherein mod (x,2 π) is the remainder modulo 2 π by x.
7. The radio frequency direction finding method of claim 1, wherein in the step 7, the threshold value is a required direction finding accuracy.
8. A radio frequency direction finding system is characterized by comprising N-element uniform circular array antennas, N phase detection modules, N-1 phase detectors and a signal processing module, wherein each antenna is connected with the phase detectors through the corresponding phase detection modules, the phase detectors are respectively connected with the ith antenna and the 1 st antenna, and the voltage phase difference between the ith antenna and the first antenna is output; the processing module is connected with each phase detector to receive the voltage phase difference output by the phase detector, and is used for executing the direction finding method of any one of claims 1-7 and outputting the elevation angle and the azimuth angle of the radiation source, wherein i is 2,3,4, …, N.
Technical Field
The invention relates to the technical field of radio monitoring, in particular to a radio frequency direction finding method and a radio frequency direction finding system.
Background
The interferometer direction-finding system belongs to a phase direction-finding system, and solves the direction information of incoming waves by utilizing different signal phases received by each antenna unit caused by different antenna spatial positions when the incoming waves reach a direction-finding antenna array. The interferometer direction finding technology has been widely used in the passive direction finding field due to its high precision, clear principle, wide frequency band and other features.
The phase interferometer is a direction-finding method commonly adopted in the current direction-finding system because of high direction-finding precision. The linear least square method is simple in operation, and the two-dimensional incident angle can be obtained by processing the phase information of the circular array with least squares (see the documents: Y.Wu, H.C.so.simple and secure two-dimensional angle estimate for a single angular area with spatial angular array [ J ]. IEEE extensions Wireless Angle Wireless and Provisioning Letters 2008,7(1): 78-80; B.Liao, Y.T.Wu, S.C.Chan.A generating angle estimate for a single angular area 2012 [ J ]. IEEE antenna interference angles, 11(1): 986). However, the phase-based least square method does not consider the phase ambiguity problem and is not suitable for large-aperture circular arrays.
For a large-aperture circular array, the phase discrimination range of the phase discriminator is only 2 pi, when the antenna spacing is large enough to cause the actual phase difference to exceed 2 pi, the phase value output by the phase discriminator can overturn by taking 2 pi as a period, and multi-value ambiguity occurs, so that the real phase and the actual receiving phase are subjected to many-to-one mapping. When the radius of the circular array is large, the phase value range exceeds 2 pi, so that phase ambiguity occurs. The longer the distance between the two antennas is to obtain high angle measurement precision; to achieve a phase not exceeding 2 pi, the distance between the two antennas should be small enough, which is contrary to the condition of improving the direction-finding accuracy.
The reported literature reports adopt a multi-baseline method (see the literature: summer Shao, Yangjingji, one-dimensional search and long and short baseline combined interferometer design method [ J ] fire control radar technology, 2013,42(02): 33-37; quarterly dawn light, high dawn light; an airborne passive positioning method-interferometer positioning [ J ]. firepower and command control, 2008,33(11):158-, 2008; xileixue, Wang Guangsong, Dynasty, Xuxu, round array phase interferometer two-dimensional direction finding ambiguity resolving new method [ J ]. telemetering and remote control, 2007, (05): 53-59; zhao national Wei, high precision airborne single station passive positioning technology research [ D ]. instructor: plum, brave. northwest university of industry, 2007; yuanxiakang phase interferometer direction finding localization study [ J ]. Shanghai Spaceflight, 1999, (03):3-9), parallel baseline method (see literature: zhang Yi Sail, missile-borne radar direction finding technical research [ D ]. instructor: lyric facing river, university of electronic technology, 2018; cattail, parallel baseline solution fuzzy interferometer direction finding algorithm and realization [ D ]. instructor: koro spring forest, university of electronic technology, 2013; the university of electronic science and technology, a two-dimensional direction-finding method of a circular array phase interferometer based on a parallel baseline, China, CN201110235023.7[ P ]. 2012-04-18; china aerospace science and technology group company, fifth research institute, third research institute, a direction-finding positioning system combining phase difference direction finding and space spectrum direction finding, China, CN201510182536.4[ P ].2015-07-01, an extended baseline method (see literature: china, CN201110226585.5[ P ].2012-04-11), correlation method (see literature: tao, Ling Ming, Rirengang, even odd-even array element number-uniform circular array direction-finding performance research [ J ]. modern radar, 2016,38(11): 24-29; study of two-dimensional direction finding algorithm based on uniform circular array [ D ]. instructor: he, university of electronic technology, 2014; liu Mang surpasses, research on radio direction finding method [ D ]. instructor: yangjianhong, Lanzhou university, 2013; application of correlation operations in phase interferometer disambiguation [ J ] acoustic techniques, 2010,29(05): 538-; china, CN201310116050.1[ P ].2013-08-07), virtual baseline method (see literature: jianlinhong, wideband interferometer signal processing and direction finding algorithm research based on GPU [ D ]. instructor: who, university of electronic technology, 2012; wuvowei micro, Chengting, Jiakexin, He, interferometer direction finding algorithm [ J ] based on virtual array transform modern radar, 2012,34(03): 42-45; li Peng-Fei, broadcasting band direction of arrival base on virtual base evaluation and RBFNN [ J ]. Journal of evaluation, 2012,33(2): 210-. And an optimal baseline method is adopted, wherein different optimal baseline groups are selected according to different azimuth angles, and a two-dimensional incident angle is solved (see the literature: Panyujian, Dingxian, Huangjing, Yangxing, Yuannalchang. the improvement of direction-finding performance of a simulation phase demodulation circular array interferometer and the verification thereof [ J ]. systematic engineering and electronic technology, 37(6),2015), so that the problems of complex calculation and insufficient application of an antenna are solved.
For high accuracy direction finding, the distance between the antennas is required to be large enough, which results in a large ambiguity range of the phase, and one phase difference corresponds to many possible incident angles, which requires adding multiple sets of antennas to remove multiple values of the incident angle. For the ambiguity resolution methods such as the multi-baseline, the parallel baseline, the extended baseline, the virtual baseline and the like, the higher the accuracy is, the more the number of antennas is, the angle measurement only uses part of the antennas, and the rest antennas are only used for eliminating multiple values, so that the hardware resources are not fully utilized, and the angle measurement accuracy cannot be improved through the added antennas.
In a word, the method has the steps of searching, clustering threshold setting, logic judgment and the like, and has the problems of complex calculation and low precision caused by insufficient antenna application.
Disclosure of Invention
Aiming at the existing problems, a radio frequency direction finding method and a radio frequency direction finding system are provided, and the aim of high-precision real-time two-dimensional direction finding is achieved.
The technical scheme adopted by the invention is as follows: a radio frequency direction finding method, comprising the process of:
step 1, for an N-element uniform circular array antenna, obtaining a voltage phase difference between each antenna and a first antenna through a phase discriminator;
step 2, when incoming waves enter the circular array antenna with the elevation angle of 0 degree, recording the voltage phase difference of each antenna and the first antenna obtained through the phase discriminator as an initial phase difference
Step 3, constructing a plurality number corresponding to each antenna according to the voltage phase difference and the initial phase difference;
step 4, setting the initial elevation angle asInitial azimuth angle ofThe iteration number k is 0;
step 5, when the iteration number is k, according to the elevation angleAnd azimuth angleCalculate each antennaPhase difference with the first antenna;
step 6, introducing a vector X and a direction vector G, and calculating the elevation angle of the two-dimensional incident angle of the iteration times k +1 by combining the constructed complex number
Step 7, calculating the difference between the two-dimensional incident angles with the iteration times k +1 and the iteration times k, comparing the result with a threshold value, and entering step 8 if the result is smaller than the threshold value; otherwise, adding 1 to the value of the iteration times k, and entering the step 5;
step 8, outputting the two-dimensional incident angle
Further, in the step 1, N in the N-element uniform circular array antenna is not less than 3.
Further, in the step 3, a specific method for constructing a plurality of modules is as follows:
wherein, ViRepresents the complex number, phi, corresponding to the ith antennai1The voltage phase difference between the ith antenna and the first antenna is shown,
Further, in the step 5, a specific method for calculating the theoretical phase difference between each antenna and the first antenna is as follows:
wherein the content of the first and second substances,denotes the phase difference between the ith antenna and the first antenna, c is the wave speed in space, ρ denotes the radius of the circular array antenna, αiAnd indicating the angular position of the ith antenna, wherein the angular position of the first antenna is 0, and i is 2, 3.
Further, in the step 6, the elevation angle of the two-dimensional incident angle is calculated
step 61, setting vector X(k)＝[x1,x2]T
Wherein T represents a matrix transpose;
step 62, calculating a direction vector, G ═ G1,g2]T(ii) a Wherein:
step 63, updating the vector X to obtain the value of the vector X at the (k + 1) th time;
X(k+1)＝X(k)+G
wherein the content of the first and second substances,
step 64, according to X(k+1)Calculating the elevation angle of the k +1 st two-dimensional incident angle
Wherein, | | represents a complex modulus, real represents the operation of taking a complex real part, and arg represents the operation of solving a complex phase.
Further, in step 7, a specific method for calculating a difference between the iteration number k +1 and the two-dimensional incident angle with the iteration number k is as follows:
wherein mod (x,2 π) is the remainder of x modulo 2.
Further, in step 7, the threshold value is the required direction finding precision.
Furthermore, the radio frequency direction finding system comprises N-element uniform circular array antennas, N phase detection modules, N-1 phase detectors and a signal processing module, wherein each antenna is connected with the phase detectors through the corresponding phase detection modules, the phase detectors are respectively connected with the ith antenna and the 1 st antenna, and the voltage phase difference between the ith antenna and the first antenna is output; and the processing module is connected with each phase detector, receives the voltage phase difference output by the phase detector, and is used for executing the direction finding method and outputting the elevation angle and the azimuth angle of the radiation source, wherein i is 2,3 and 4 … N.
Compared with the prior art, the beneficial effects of adopting the technical scheme are as follows:
the invention provides a two-dimensional incident angle measuring method and system with simple realization and high precision. The method and the system have the advantages that complex number operation is adopted, so that the phase ambiguity problem is avoided; the information of all antennas on the circular array is utilized, so that the direction finding precision is improved; and an iterative algorithm is adopted, so that operations such as logic judgment and the like are avoided.
Drawings
FIG. 1 is a direction-finding system architecture diagram of the present invention.
Fig. 2 is a schematic view of a uniform circular array of the present invention.
FIG. 3 is a schematic view of the direction-finding coordinate system of the present invention.
Fig. 4 is a fixed incidence azimuth of 60 °, phase noise: 5 degrees, 10 degrees, 15 degrees and 20 degrees, and a relation graph of azimuth root-mean-square error and incident elevation angle.
Fig. 5 is a fixed incidence azimuth of 60 °, phase noise: 5 DEG, 10 DEG, 15 DEG, 20 DEG, and an elevation root mean square error and an incidence elevation angle.
Fig. 6 is a fixed incident elevation angle of 30 °, phase noise: 5 degrees, 10 degrees, 15 degrees and 20 degrees, and the azimuth root-mean-square error is plotted against the incident azimuth angle.
Fig. 7 is a fixed incident elevation angle of 30 °, phase noise: 5 DEG, 10 DEG, 15 DEG and 20 DEG, and the root mean square error of elevation angle is plotted against the incident azimuth.
Fig. 8 is a fixed incidence azimuth 45 °, elevation: the azimuth root mean square error is 10 degrees, 20 degrees, 30 degrees and 40 degrees, and the incidence elevation angle is a graph.
Fig. 9 is a fixed incidence azimuth 45 °, elevation: the root mean square error of the elevation angle is plotted against the incident elevation angle by 10 degrees, 20 degrees, 30 degrees and 40 degrees.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The invention provides a two-dimensional incident angle measuring method and system with simple realization and high precision. The method has the advantages that complex number operation is adopted, so that the phase ambiguity problem is avoided; the information of all antennas on the circular array is utilized, so that the direction finding precision is improved; an iterative algorithm is adopted, so that operations such as logic judgment and the like are avoided; the radio frequency receiving system shown in fig. 1 is used, and the main function of the radio frequency receiving system is to convert the extracted space electromagnetic wave into phases reaching different antennas, and the direction-finding system can be, but is not limited to, the form shown in fig. 1. In the figure, N is the number of antennas, and a phase discriminator is used for phase detection to obtain the phase difference between each antenna and one of the antennas. Without loss of generality, each antenna is subjected to phase discrimination with the first path of antenna.
Without loss of generality, the antenna array is positioned on the xoy plane and at an elevation angle thetasIs included angle between the incoming wave direction and the z-axis and has an azimuth angle phisThe incoming wave direction makes an angle with the x-axis, as shown in FIG. 3. The specific direction finding scheme is as follows:
a radio frequency direction finding method, comprising the process of:
step 1, as shown in fig. 2, for an N-element uniform circular array antenna, a phase detector is used to obtain a voltage phase difference Φ between each antenna and a first antennai1；
Step 2, when incoming waves enter the circular array antenna with the elevation angle of 0 degree, recording the voltage phase difference of each antenna and the first antenna obtained by the phase discriminator as an initial phase difference
Step 3, constructing a plurality number corresponding to each antenna according to the voltage phase difference and the initial phase difference;
step 4, setting the initial elevation angle asInitial azimuth angle ofThe iteration number k is 0;
step 5, when the iteration number is k, according to the elevation angle
step 6, introducing a complex number calculation iteration number k +1 constructed by combining the vector X and the direction vector G to calculate the elevation angle of the two-dimensional incident angle of the iteration number k +1And azimuth angle
Step 7, calculating the difference between the two-dimensional incident angles with the iteration times k +1 and the iteration times k, comparing the result with a threshold value, and entering step 8 if the result is smaller than the threshold value; otherwise, adding 1 to the value of the iteration times k, and entering the step 5;
step 8, outputting the two-dimensional incident angleAndas the elevation and azimuth of the radiation source.
Further, in the step 1, N in the N-element uniform circular array antenna is not less than 3.
Further, in the step 3, a specific method for constructing a plurality of modules is as follows:
wherein, ViRepresents the complex number, phi, corresponding to the ith antennai1The voltage phase difference between the ith antenna and the first antenna is shown,the phase difference between the ith antenna and the first antenna is shown when the incoming wave enters the circular array antenna with the elevation angle of 0 degree; i is 2,3, …, N. V.v. ofi＝1，i＝1
Further, in the step 5, a specific method for calculating the theoretical phase difference between each antenna and the first antenna is as follows:
wherein the content of the first and second substances,
Further, in the step 6, the elevation angle of the two-dimensional incident angle is calculatedAnd azimuth angleThe method comprises the following specific steps:
step 61, setting vector X(k)＝[x1,x2]T
Wherein T represents a matrix transpose;
step 62, calculating a direction vector, G ═ G1,g2]T(ii) a Wherein:
step 63, updating the vector X to obtain the value of the vector X at the (k + 1) th time;
X(k+1)＝X(k)+G
wherein the content of the first and second substances,
step 64, according to X(k+1)Calculating the elevation angle of the k +1 st two-dimensional incident angleAnd azimuth angle
Wherein, | | represents a complex modulus, real represents the operation of taking a complex real part, and arg represents the operation of solving a complex phase.
Further, in step 7, a specific method for calculating a difference between the iteration number k +1 and the two-dimensional incident angle with the iteration number k is as follows:
wherein mod (x,2 π) is the remainder modulo 2 π by x.
Further, in step 7, the threshold value is the required direction finding precision.
As shown in fig. 1, the present invention further provides a radio frequency direction finding system, which includes N-ary uniform circular array antennas, N phase detection modules, N-1 phase detectors, and a signal processing module, wherein each antenna is connected to the phase detector through a corresponding phase detection module, the phase detectors are respectively connected to the ith antenna and the 1 st antenna, and output a voltage phase difference between the ith antenna and the first antenna; and the processing module is connected with each phase detector, receives the voltage phase difference output by the phase detector, and is used for executing the direction finding method and outputting the elevation angle and the azimuth angle of the radiation source, wherein i is 2,3 and 4 … N.
To verify the effect of the present invention, the root mean square of the direction error was calculated by 1000 monte carlo simulations, and the results are shown in fig. 4 to 9. The working frequency is 3GHz, and the signal noise is white Gaussian noise.
Fig. 4 and 5 show the rms error in azimuth and rms error in elevation versus angle of incidence, respectively, at different snr. The simulation conditions are as follows: the array element number N is 5, the array radius r is 360mm, the phase noise respectively takes 5 degrees, 10 degrees, 15 degrees and 20 degrees, and the incident azimuth angle is 60 degrees.
Fig. 6 and 7 show the root mean square error in azimuth and the root mean square error in elevation, respectively, as a function of the angle of incidence at different signal-to-noise ratios. The simulation conditions are as follows: the number of array elements N is 7, the array radius r is 400mm, the phase noise respectively takes 5 degrees, 10 degrees, 15 degrees and 20 degrees, and the incident elevation angle is 30 degrees.
Fig. 8 and 9 show the rms error in azimuth and in elevation as a function of the signal-to-noise ratio at different angles of incidence, respectively. The simulation conditions are as follows: array element number N is 9, array radius r is 500mm, incident elevation angle: 10 degrees, 20 degrees, 30 degrees and 40 degrees, and the incidence azimuth angle is 45 degrees.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed. Those skilled in the art to which the invention pertains will appreciate that insubstantial changes or modifications can be made without departing from the spirit of the invention as defined by the appended claims.
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
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