CN114994597A - Interferometer direction finding method based on uniform circular array - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/14—Systems for determining direction or deviation from predetermined direction
- G01S3/46—Systems for determining direction or deviation from predetermined direction using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
- G01S3/48—Systems for determining direction or deviation from predetermined direction using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/14—Systems for determining direction or deviation from predetermined direction
- G01S3/46—Systems for determining direction or deviation from predetermined direction using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
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Abstract
The invention belongs to the technical field of electronic reconnaissance and relates to an interferometer direction finding method based on a uniform circular array. The invention provides a direction finding method of an interferometer based on a uniform circular array, which combines a amplitude comparison method and a phase comparison method, utilizes the characteristic that the uniform array can provide an omnidirectional azimuth angle and the directional diagram difference of different pitch angles of an antenna, and carries out the direction finding of the interferometer by a method of inquiring a database so as to finish the direction measurement estimation of a signal source. The method has the advantages that 360-degree omnidirectional direction finding of the direction finding by a phase comparison method can be realized, amplitude phase deviation caused by the pitch angle is corrected, so that the direction finding precision is effectively improved, the incident angle information of the signal is accurately estimated, the pitch angle information can be accurately estimated under the condition of high signal-to-noise ratio, the method is simple, and the effect is good.
Description
Technical Field
The invention belongs to the technical field of electronic reconnaissance and relates to an interferometer direction finding method based on a uniform circular array.
Background
Currently, signal detection usually adopts two modes of active detection and passive detection. Active detection means that detection equipment actively radiates signals outwards, and then receives signals reflected by a target object to complete direction finding on a target position, but with the gradual maturity of radar countermeasure technologies such as electronic interference and anti-radiation, active detection technologies represented by radars are increasingly challenged and threatened. The passive detection means that the detection device is not required to actively radiate signals outwards, and only the signals radiated outwards by the target radiation source are used for carrying out direction finding on the target to determine the position of the target. Compared with an active direction-finding system, the passive direction-finding system has the advantages of strong anti-interference capability, strong low-altitude detection capability, wide frequency coverage range, long action distance, good equipment portability and the like. Common passive direction finding methods mainly include amplitude method direction finding, phase method direction finding, spatial spectrum direction finding and the like.
The amplitude comparison method and the phase comparison method are the most commonly used passive direction finding methods, have the characteristic of simple method realization, generally adopt a plurality of independent antennas to form an antenna array covering 360 degrees of directions, and the antenna array mainly using the phase comparison direction finding method is called as an interferometer. In the actual direction finding process of the uniform circular array interferometer, a target signal usually has a certain pitch angle relative to a receiver, and antenna directional patterns under different pitch angles are different, so that the pitch angle can cause the phase and amplitude of an array element receiving signal to shift, and a direction finding result and a result under the condition of no pitch angle have larger deviation. By combining the measurement results of the amplitude comparison method and the phase comparison method, the database constructed by the actual array element directional diagram is searched, and the purpose of correcting amplitude-phase deviation caused by the pitching angle can be achieved by utilizing directional diagram information of the antenna with different pitching angles.
Disclosure of Invention
The invention aims to solve the problems and provides an interferometer direction finding method based on a uniform circular array, which combines a phase comparison method and a phase comparison method, utilizes the characteristic that a circular array antenna can cover 360-degree omnibearing azimuth angles and the directional diagram difference of the antenna under different pitch angles, and carries out interferometer direction finding by a method of inquiring a database so as to complete direction measurement and estimation of a signal source.
The technical scheme of the invention is as follows:
a interferometer direction finding method based on a uniform circular array combines information of two dimensions of a phase comparison method and a amplitude comparison method, a power ratio and phase difference database of different azimuth angles and pitch angles of adjacent array elements is constructed based on an actual antenna directional diagram, amplitude phase deviation caused by the pitch angles is corrected by searching a data position closest to a measured value of a signal phase difference and a power ratio of an adjacent antenna in the database constructed by the actual antenna directional diagram, and a flow schematic diagram of the technical scheme is shown in figure 1. The following steps are that the pitch angle theta and the azimuth angle of the antenna with the strongest receiving signal relative to the uniform circular array
The signal incidence direction estimation comprises the following steps:
s1, determining the actual pitch angle range and azimuth angle range of each array element according to the use scene of the interferometer, generating a power ratio lookup table and a phase difference lookup table of adjacent array elements in the appointed pitch angle and azimuth angle range by using the actual antenna array element directional diagram, setting 2N same antenna array elements which are arranged at equal intervals along the whole circumference by taking the uniform circular array interferometer antenna array shown in figure 2 as an example, defining the pitch angle theta of an antenna coordinate system as the included angle between the incident direction of a signal and the upward direction vertical to the array element arrangement plane, and setting the relative pitch angle theta of the signal to the pitch angle theta r Defined as the angle between the incident direction of the signal and the plane of the array element, the relative azimuth angle
Defined as the included angle between the projection of the incident direction of the signal on the array element arrangement plane and the azimuth reference direction of the array element directional diagram, and the global azimuth
Is defined as the included angle between the incident direction of the signal and the reference direction of the array element plane.
Because of the symmetry of the array structure, the incident angle of any signal is within the range of the azimuth angle (90/N) degree of a certain antenna array element, so the azimuth angle range is the azimuth angle (90/N) degree of the antenna array element, and the direction pointed by the antenna array element corresponds to the direction pointed by the antenna array elementIn its own direction diagram
Therefore, it is
The value range of (A) is 90 +/-90/N degree. Determining the pitch angle range of the plane where the relative array elements are located to be theta according to the application scene of the antenna r1 ～θ r2 (θ r1 >θ r2 ) (the pitch angle of the incidence direction above the plane is specified to be positive), namely the theta value range is 90-theta r1 ～90-θ r2 。
The direction finding principle is that the area where the signal incidence direction is located is determined according to the serial number m of the strongest array element of the received signal and the serial number n of the second strongest array element of the adjacent signal, a distance query table is constructed by utilizing the relation between the difference of the amplitude response and the phase response of an antenna directional diagram and the relative incidence angle, then the position of the point with the closest distance is searched in the query table according to the signal power ratio and the phase difference measurement result of the two array elements, and the position is used as the estimation of the relative incidence angle of the signal relative to the strongest array element of the received signal. Making a power ratio lookup table A and a phase difference lookup table P at intervals of 1 degree, wherein A and P are both theta r2 -θ r1 A matrix of +1| × (180/N +1), assuming that the antenna pattern is F, then:
wherein i is 1| - | θ r2 -θ r1 +1| is the row number of the look-up table matrix, corresponding to the relative elevation angle θ of the signal with respect to the antenna receiving the strongest signal, j being 1- (180/N +1), corresponding to the relative azimuth of the signal
The relative azimuth of the signal with respect to the second strong array element of the signal reception signal,
a mode value representing the antenna pattern is shown,
and representing the phase of an antenna directional diagram, wherein A (i, j) is the ratio of the power response of the antenna with the strongest receiving signal at the moment to the power response of the antenna with the second strongest receiving signal, P (i, j) is the difference of the phase responses of the two antennas at the moment, and then the dynamic range normalization is carried out on two lookup tables:
where max (a) represents the maximum value of the elements in matrix a, min (a) represents the minimum value of the elements in matrix a, a divided by a constant is equivalent to each element in a divided by the constant.
S2, respectively obtaining the power ratio and the phase difference of two array elements adjacent to the signal incidence direction through measurement
Wherein
The power and phase of the array element with the strongest received signal are divided or subtracted by the power and phase of the second strong array element of the signal. Assuming that the signal incidence direction is as shown in FIG. 3, the signal relative incidence angle isα, then the phase difference between array element m and array element n is given by:
wherein d is the length of the base line of the antenna array element, λ is the wavelength corresponding to the central frequency of the signal carrier, and α is the relative incident angle of the signal relative to the strongest array element of the received signal. A distance lookup table D is constructed based on the lookup table A, P:
wherein the definition of the distance takes the form of a 1-norm,
each element representing a is subtracted
argminD (i, j) represents the value of (i, j) when D (i, j) takes the minimum value, and the relative angle of incidence of the signal with respect to the strongest antenna of the received signal is obtained by searching the abscissa and ordinate of the minimum value in D
And an estimate of the planar pitch angle relative to the array elements
Finally, the sequence number of the strongest array element of the received signal and the obtained relative incident angle of the signal are looked up to obtain the incident azimuth angle of the signal
The method has the advantages that 360-degree omnidirectional direction finding of the direction finding by a phase comparison method can be realized, amplitude phase deviation caused by the pitch angle is corrected, so that the direction finding precision is effectively improved, the incident angle information of the signal is accurately estimated, the pitch angle information can be accurately estimated under the condition of high signal-to-noise ratio, the method is simple, and the effect is good.
Drawings
FIG. 1 is a flow chart of the technical scheme.
FIG. 2 is a schematic plan top view of an array element of the uniform circular array interferometer.
FIG. 3 is a schematic view of an interferometer direction finding.
Fig. 4 shows the phase response directional diagram and the power response directional diagram of the antenna unit when the pitch angle is 0 degree.
Fig. 5 shows the phase response pattern and power response pattern of the antenna element at 30 degrees of elevation.
FIG. 6 is a circle matrix amplitude curve diagram and a phase curve diagram.
The measurement result curve of the phase comparison method and the improved interferometer method under the conditions of 720 dB signal-to-noise ratio and different relative pitch angles is shown.
The graph of the measurement result of the relative pitch angle of the improved interferometer under different relative pitch angles with 820 dB signal-to-noise ratio is shown.
FIG. 9 shows the root mean square error curves of the measured values of the azimuth angles under the conditions of different signal-to-noise ratios and the pitch angles of-5 to 30 degrees.
FIG. 10 shows the root mean square error curves of the pitch elevation measurements for different SNR.
Detailed Description
The technical solution of the present invention will be further explained with reference to the drawings and simulations.
The present example will perform simulation verification on the proposed method, and for simplicity, the following assumptions are made for the algorithm model:
1. the uniform circular array reconnaissance antenna array is in an XY plane, and a target has a certain pitch angle relative to the XY plane;
2. mutual coupling between antenna elements, antenna gain, beam width, etc. are uniform.
3. No amplitude and phase errors exist among array channels, and only Gaussian white noise exists in an electromagnetic environment.
The number of the circular array antennas is set to be 2N-12 array elements, the interval of a plurality of independent beams is 30 degrees at the moment, the azimuth angles of incident signals are 157 degrees and 10 degrees respectively, and the pitch angle relative to the plane of the array elements is-5 degrees to 30 degrees. During searching, firstly, the positions of the array element with the strongest signal and the array element with the second strongest signal are determined, then the power ratio and the phase difference of the array element with the strongest signal relative to the array element with the second strongest signal are calculated, and the azimuth angle information of the signal is obtained by searching the coordinate of the nearest numerical value in a prefabricated database. The uniform circular array antenna forms a wave beam covering 360 degrees of azimuth angles.
The simulation results are shown in the figure:
fig. 4 shows the power pattern and phase pattern of the real antenna at 0 ° relative to the elevation angle, and fig. 5 shows the power pattern and phase pattern of the real antenna at 30 ° relative to the elevation angle. As can be seen, the power pattern and the phase pattern of a real antenna are generally not the same at different relative elevation angles.
Fig. 6 shows the theoretical values of the phase ratio and amplitude ratio method at different relative angles of incidence for a relative pitch angle of 0 ° and a relative pitch angle of 30 °, respectively. As can be seen, the two curves are not identical at different relative pitch angles, and this difference is the basis for eliminating the pitch error and making the pitch angle estimation.
Fig. 7 shows the measurement results of signals with true incident angles of 157 ° and 10 ° respectively under the signal-to-noise ratio of 20dB, in which the phase reference of the phase comparison method refers to the antenna directional pattern at the relative elevation angle of 15 °, and the direction-finding error of the relative elevation angle taken as the reference in the selected range of the relative elevation angle is smaller than that of other elevation angles. From the results of fig. 6, it can be seen that under the condition of high signal-to-noise ratio, the improved interferometer direction-finding method completely eliminates the direction-finding error caused by the pitch angle, while the general phase comparison method can only correctly measure the incident direction of the signal around the selected reference datum relative to the pitch angle.
Fig. 8 shows the estimation results of the relative pitch angles when the signal incident angles are 157 ° and 10 ° respectively at a signal-to-noise ratio of 20dB, and it can be seen from the figure that the improved interferometer direction finding method can simultaneously estimate the pitch angle more accurately.
Fig. 9 shows the root mean square error of DOA estimation in different pitch angles by the phase comparison method and the present method at different signal-to-noise ratios at signal incident angles of 10 ° and 157 °, respectively. It can be seen from the figure that the error level of the ordinary phase comparison method for measuring the DOA at different pitch angles is higher and basically independent of noise under different signal-to-noise ratios, and the error of the method is obviously reduced along with the increase of the signal-to-noise ratio and is obviously better than that of the ordinary phase comparison method.
Fig. 10 shows the root mean square error of the pitch angle estimation by the method under different signal-to-noise ratios, and the estimation error of the pitch angle estimation by the method is obviously reduced along with the increase of the signal-to-noise ratio.
Claims (1)
1. An interferometer direction finding method based on uniform circular array defines the pitch angle theta and the azimuth angle theta of the antenna with the strongest signal received by the uniform circular array
The method is characterized by comprising the following steps:
s1, determining the actually used pitch angle range and azimuth angle range of each array element according to the use scene of the interferometer, and generating an adjacent array element power ratio lookup table and a phase difference lookup table in the specified pitch angle and azimuth angle range by using the actual antenna array element directional diagram, wherein the method specifically comprises the following steps:
2N same antenna elements arranged at equal intervals are set along the whole circumference of the uniform circular array, the pitch angle theta of an antenna coordinate system is defined as the included angle between the incident direction of a signal and the upward direction vertical to the array element arrangement plane, and the signal is opposite to the pitch angle theta r Defined as the angle between the incident direction of the signal and the plane of the array element, the relative azimuth angle
Defined as the included angle between the projection of the incident direction of the signal on the array element arrangement plane and the azimuth reference direction of the array element directional diagram, and the global azimuth
Defining an included angle between a signal incidence direction and an array element plane reference datum direction;
due to the symmetry of the array structure, the incident angle of any signal is within the range of the azimuth angle (90/N) ° of a certain antenna array element, so the azimuth angle range is the azimuth angle (90/N) ° of the antenna array element, and the direction pointed by the antenna array element corresponds to the directional diagram of the antenna array element
Therefore, it is
The value range of (A) is 90 +/-90 (90/N) DEG; determining the pitch angle range of the plane where the relative array elements are located to be theta according to the application scene of the antenna r1 ～θ r2 (θ r1 >θ r2 ) I.e. theta is in the range of 90-theta r1 ～90-θ r2 ；
The direction finding principle is that the area where the signal incidence direction is located is determined according to the serial number m of the strongest array element of a received signal and the serial number n of the second strongest array element of an adjacent signal, a distance query table is constructed by utilizing the relation between the difference of the amplitude response and the phase response of an antenna directional diagram and the relative incidence angle, then the position of the point with the nearest distance is searched in the query table according to the signal power ratio and the phase difference measurement result of the two array elements, the position is used as the estimation of the relative incidence angle of the signal relative to the strongest array element of the received signal, a power ratio query table A and a phase difference query table P are manufactured at the interval of 1 degree, A and P are both | theta r2 -θ r1 A matrix of +1| × (180/N +1), assuming that the antenna pattern is F, then:
θ＝89-θ r1 +i,
wherein i is 1 to theta r2 -θ r1 +1| is the row number of the look-up table matrix, corresponding to the relative pitch angle θ of the signal with respect to the antenna with the strongest received signal, j being 1- (180/N +1), corresponding to the relative azimuth angle of the signal
The relative azimuth of the signal with respect to the second strong array element of the signal received signal,
a modulus value representing the antenna pattern is shown,
expressing the phase of the antenna directional diagram, A (i, j) is the ratio of the power response of the antenna with the strongest receiving signal at the moment and the power response of the antenna with the second strongest receiving signal, P (i, j) is the difference of the phase responses of the two antennas at the moment, and then carrying out dynamic range normalization on two lookup tables:
where max (A) represents the maximum value of the elements in matrix A, min (A) represents the minimum value of the elements in matrix A, A divided by a constant is equivalent to each element in A divided by the constant;
s2, respectively obtaining the power ratio and the phase difference of two array elements adjacent to the signal incidence direction through measurement
Wherein
Dividing or subtracting the power and the phase of the second strong array element of the signal by the power and the phase of the array element with the strongest received signal; the relative incident angle of the signal is α, the phase difference between the array element m and the array element n is given by:
wherein D is the base length of the antenna array element, λ is the wavelength corresponding to the signal carrier central frequency, α is the relative angle of incidence of the signal with respect to the strongest array element of the received signal, and a distance lookup table D is constructed based on a lookup table A, P:
wherein the definition of the distance takes the form of a 1-norm,
each element representing a is subtracted
argminD (i, j) represents the value of (i, j) when D (i, j) takes the minimum value, and the relative angle of incidence of the signal with respect to the strongest antenna of the received signal is obtained by searching the abscissa and ordinate of the minimum value in D
And an estimate of the planar pitch angle relative to the array elements
Finally, the sequence number of the strongest array element of the received signal and the obtained relative incident angle of the signal are looked up to obtain the incident azimuth angle of the signal
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| CN116819430A (en) * | 2023-06-30 | 2023-09-29 | 中国人民解放军军事科学院系统工程研究院 | Direction finding method for same-frequency signal under strong radiation source background |
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