CN114137476A - Short wave direction finding method based on polarization correction - Google Patents
Short wave direction finding method based on polarization correction Download PDFInfo
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- CN114137476A CN114137476A CN202111437458.XA CN202111437458A CN114137476A CN 114137476 A CN114137476 A CN 114137476A CN 202111437458 A CN202111437458 A CN 202111437458A CN 114137476 A CN114137476 A CN 114137476A
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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
Abstract
The invention discloses a short wave direction finding method based on polarization correction, which is used for a short wave antenna array, wherein the antenna array is formed by arranging M horizontal polarization antenna array elements according to a circular array, M is more than or equal to 3, and the interval of the antenna array elements is theta (determined according to the width of an antenna beam): a space narrow-band plane wave with central frequency is incident to the antenna array at an angle, a scanning angle-correlation coefficient curve is obtained according to a plurality of steps, the scanning angle corresponding to the maximum correlation coefficient point is the incoming wave direction, and the frequency point direction finding is finished. The invention discloses a short wave direction finding method based on polarization correction, which eliminates the interference of polarization components on direction finding by correcting polarization components of incoming waves. Compared with the existing short wave direction finding algorithm, the method has the remarkable advantages that: the method has a relatively obvious correction effect on the incoming wave with the polarization component, and can measure a more accurate incoming wave direction.
Description
Technical Field
The invention belongs to the field of short wave direction finding, and particularly relates to a short wave direction finding method based on polarization correction in the field.
Background
The short wave direction finding is the process of determining the incoming wave direction by using a short wave antenna array and direction finding instrument equipment thereof according to the propagation characteristics of electromagnetic waves. The method of processing the electromagnetic signals received by the short wave antenna to determine the incoming wave direction is called direction finding algorithm. Direction finding algorithms can be divided into two broad categories: scalar and vector methods. The scalar method is an algorithm for carrying out direction finding by utilizing one item of amplitude or phase of a received signal, and the vector method can carry out direction finding by utilizing amplitude and phase information at the same time. The polarization correction short wave direction finding method in the application is based on a vector method to carry out direction finding.
In actual direction finding, real sky wave signals are generally elliptical polarized waves and comprise horizontal and vertical polarized components, most of common direction finding antennas are linear polarized antennas, the direction finding antennas are affected by the polarized components of incoming wave signals in the direction finding process, direction finding errors can be increased by the polarized components, direction finding results are seriously affected, even completely wrong direction finding results can be caused, and therefore the influence of the polarized components on the direction finding is eliminated in short wave direction finding. However, at present, the polarization correction method aiming at short wave direction finding has not been reported in public by referring to domestic related documents.
Disclosure of Invention
The invention aims to solve the technical problem of providing a short wave direction finding method based on polarization correction, which mainly differs from the traditional short wave direction finding algorithm in that: firstly, polarization correction is carried out on actual receiving data of each antenna array element, and direction finding calculation is carried out by using corrected response data, so that the influence of incoming wave polarization components on short wave direction finding is eliminated.
The invention adopts the following technical scheme:
a short wave direction finding method based on polarization correction is used for a short wave antenna array, the antenna array is formed by arranging M horizontal polarization antenna array elements according to a circular array, M is more than or equal to 3, the interval of the antenna array elements is theta (determined according to the width of an antenna beam), and the improvement is that:
is provided with a central frequency omega0At an angle theta1Incident to the antenna array, where theta1＝(θ1,φ1)，θ1And phi1Respectively the elevation angle and the phase angle of the incoming wave signal, and theta is more than or equal to 01＜90°，0≤φ1< 360 deg., as shown in FIG. 1, the output x of the m-th array element of the antenna arraym(t) is expressed as:
m is more than or equal to 1 and less than or equal to M, s (t) is a source signal of an incident antenna array and is an amplitude factor of an incoming wave signal, j omega0Is the phase factor of the incoming wave signal, nm(t) additive noise of the m-th array element, τm(Θ1) Relative time delay when an incoming wave signal is projected to the m-th array element is obtained;
step 1, recording measured values cv _ M of each antenna element, cv _ M ═ cv1,…,cvN,…,cvM]The cv _ M is an M-dimensional complex array, and the amplitude value of the actually measured receiving signal of each antenna array element is obtained, and the maximum value of the selected amplitude and the corresponding antenna direction theta are comparedN；
Step 2, recording the antenna array element corresponding to the maximum amplitude value as N, and selecting 2 × i +1 antenna array elements (i is determined according to the antenna type and the beam width) which take part in the operation, wherein the antenna array elements are N-i, …, N-1, N, N +1, …, N + i;
step 3, setting a scanning angle fai _ scan and a scanning range theta by taking the antenna array element N as a centerN-i*θ≤fai_scan≤θN+ i x theta, the scanning precision delta theta can be 0.1 degrees, 0.5 degrees, 1 degree, 2 degrees and the like according to the direction-finding precision requirement;
and 4, calculating the theoretical main polarization response of the 2 × i +1 antenna array elements by adopting a numerical method, and recording the theoretical main polarization response as cv, cv ═ xn-i，…，xn-1，xn，xn+1，…，xn+i]The cv is a 2 x i +1 dimensional complex array;
step 5, from the actually measured value array cv _ m of the antenna array element obtained in step 1, the actual antenna receiving data corresponding to the antenna array element N-i with the largest receiving amplitude is taken and recorded as cvN-i；
Step 6, calculating a response value of the N-i antenna array element about a scanning angle fai _ scan symmetric point by interpolation, and recording the response value as cv'N-iAnd calculating (cv)N-i+cv'N-i) The data is used as the corrected response data of the N-i antenna array element;
step 7, sequentially calculating the corrected response data of the other 2 × i antenna array elements selected in the step 2 according to the method in the step 6, sequentially storing the 2 × i +1 data, and marking as cv1, wherein the cv1 is a 2 × i +1 dimensional complex array;
and step 8, calculating correlation coefficients R of cv and cv 1:
in the above formula, x is cv data,
means cv data mean, y cv1 data,
mean cv1 data;
and 9, in the scanning range, fai _ scan is taken once every interval delta theta, the steps 5 to 8 are repeated, the correlation coefficients of cv and cv1 are sequentially calculated, a scanning angle-correlation coefficient curve is obtained, the scanning angle corresponding to the maximum correlation coefficient point is the incoming wave direction, and the frequency point direction finding is finished.
The invention has the beneficial effects that:
the invention discloses a short wave direction finding method based on polarization correction, which eliminates the interference of polarization components on direction finding by correcting polarization components of incoming waves. Compared with the existing short wave direction finding algorithm, the method has the remarkable advantages that: the method has a relatively obvious correction effect on the incoming wave with the polarization component, and can measure a more accurate incoming wave direction.
Drawings
FIG. 1 is a short wave antenna array receive model;
FIG. 2 is a schematic diagram of a short wave antenna array according to embodiment 1 of the present invention;
FIG. 3 is a 2.4MHz response curve actually acquired in a certain direction finding experiment;
FIG. 4 is a theoretical response curve of main polarization of 90 DEG for incoming wave and 46 DEG for main elevation at 2.4 MHz;
FIG. 5 is a plot of scan angle versus correlation coefficient calculated for polarization correction for a given experiment;
FIG. 6 is a plot of scan angle versus correlation coefficient for a test without polarization correction calculations;
fig. 7(a) is a schematic diagram of a direction finding result obtained by adopting a common direction finding method for a sky wave signal actually acquired (2.4MHz incoming wave signal, true incoming direction 28.7 degrees, and 128 times of sampling);
fig. 7(b) is a schematic diagram of a direction finding result obtained by applying the direction finding method of the present invention to a sky wave signal actually acquired (2.4MHz incoming wave signal, true incoming direction 28.7 °, and 128 samples).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The technical scheme of the invention is to provide a calculation method for actual polarized incoming wave direction finding, determine the direction with polarized incoming waves according to the calculation result of the method, set a signal source in a certain direction, and the transmitted incoming wave signals meet the following conditions:
(1) far field: supposing that the receiving antenna array is positioned in the far field of a signal source, the wave front of the signal can be approximate to plane wave when reaching the array, and the geometric aperture of the antenna array is far smaller than the distance between the signal source and the antenna array;
(2) narrow-band: assuming that the signal bandwidth is much smaller than the center frequency of the signal;
where B is the signal bandwidth, fcIs the center frequency of the signal;
(3) the incoming wave direction: the information source incident to the antenna array is assumed to be a point source, so that the radiation field angle of the information source is zero, namely the relative direction of the incoming wave is unique;
(4) noise: the noise of each antenna unit is mutually independent when receiving signals and mutually independent with the signals, and the mean value is 0 and the variance is sigma2White gaussian noise.
In example 1, in a short-wave large-scale direction-finding antenna array system, 36-element fishbone antennas are arranged according to a circular array, the antenna element interval θ is 10 °, and as shown in fig. 2, the fishbone antennas are horizontally-oriented antennas.
In a certain experiment, the actually measured response of the antenna array, which is actually acquired, of 2.4MHz and the actual incoming wave direction of 28.7 °, is shown in fig. 3, where the ordinate is the received signal amplitude in the figure, the abscissa is the azimuth angle corresponding to 16 pairs of antennas connected to a 16-channel receiver, and the curve in the figure is a 128-time continuous acquisition data curve.
Because the curve in fig. 3 is a curve for 128 times of continuously acquired data, it can be roughly seen from the graph that the amplitude value of the received signal of the 2 nd or 8 th pair of antennas of different curves is the largest, and counting the 128 times of sampled data, the antenna unit N corresponding to the maximum amplitude value can be obtained as 8, and the angle of the antenna unit facing the incoming wave direction is 60 °;
because the antenna array is a 36-element fish bone array, i is determined to be 2 according to the beam width of the fish bone antenna, and when N is 8, the receiving response of 5 pairs of antennas, 6 th, 7 th, 8 th, 9 th and 10 th, is selected to participate in direction finding calculation;
setting a scanning angle fai _ scan by taking the 8 th auxiliary antenna as a center, wherein the scanning range of the scanning angle is more than or equal to fai _ scan and less than or equal to 9 degrees, and the scanning precision delta theta is 0.1 degree;
through numerical calculation, when an incoming wave signal of 2.4MHz is incident to the antenna array, the horizontal polarization theory receiving response is shown in FIG. 4;
calculating by a polarization correction direction finding method to obtain a scanning angle-correlation coefficient curve, as shown in fig. 5, obtaining that the scanning angle corresponding to the maximum correlation coefficient point in the curve is 32.0 °, which means that the incoming wave direction obtained by the polarization correction method is 32.0 °; FIG. 6 is a plot of scan angle versus correlation coefficient without polarization correction;
calculating the directivity of the antenna array receiving data sampled 128 times continuously, as shown in fig. 7(b), the abscissa is the sampling frequency, the ordinate is the directivity, and the result of calculating the directivity is 30.9 ° which deviates from the true directivity by 2.2 °; compared with the traditional short-wave direction finding method, the direction finding is carried out on the same data, the direction-finding degree result of the figure 7(a) can be obtained, the statistical value is 56.8 degrees, and the deviation from the real direction is 28.1 degrees.
Through the comparison in the implementation process, the common short-wave direction finding method has a large and unstable error in actual direction finding, and the direction finding error exceeds 20 degrees when the direction finding error is maximum. The polarization correction direction-finding method also calculates a more accurate direction-finding result for the actual signal, and effectively eliminates the influence of the vertical polarization component on the direction finding.
Claims (1)
1. A short wave direction finding method based on polarization correction is used for a short wave antenna array, the antenna array is formed by arranging M horizontal polarization antenna array elements according to a circular array, M is more than or equal to 3, the interval of the antenna array elements is theta, and the short wave direction finding method is characterized in that:
is provided with a central frequency omega0At an angle theta1Incident to the antenna array, where theta1＝(θ1,φ1)，θ1And phi1Respectively the elevation angle and the phase angle of the incoming wave signal, and theta is more than or equal to 01＜90°，0≤φ1If < 360 deg., the output x of mth array element of antenna arraym(t) is expressed as:
m is more than or equal to 1 and less than or equal to M, s (t) is a source signal of an incident antenna array and is an amplitude factor of an incoming wave signal, j omega0Is the phase factor of the incoming wave signal, nm(t) additive noise of the m-th array element, τm(Θ1) Relative time delay when an incoming wave signal is projected to the m-th array element is obtained;
step 1, recording measured values cv _ M of each antenna element, cv _ M ═ cv1,…,cvN,…,cvM]The cv _ M is an M-dimensional complex array, and the amplitude value of the actually measured receiving signal of each antenna array element is obtained, and the maximum value of the selected amplitude and the corresponding antenna direction theta are comparedN；
Step 2, recording the antenna array element corresponding to the maximum amplitude value as N, and selecting 2 x i +1 antenna array elements of N-i, …, N-1, N, N +1, …, N + i as direction-finding antenna array elements participating in operation;
step 3, setting a scanning angle fai _ scan and a scanning range theta by taking the antenna array element N as a centerN-i*θ≤fai_scan≤θN+ i × θ, the scan precision Δ θ is 0.1 °, 0.5 °, 1 ° or 2 °;
and 4, calculating the theoretical main polarization response of the 2 × i +1 antenna array elements by adopting a numerical method, and recording the theoretical main polarization response as cv, cv ═ xn-i，…，xn-1，xn，xn+1，…，xn+i]The cv is a 2 x i +1 dimensional complex array;
step 5, from the actually measured value array cv _ m of the antenna array element obtained in step 1, the actual antenna receiving data corresponding to the antenna array element N-i with the largest receiving amplitude is taken and recorded as cvN-i；
Step 6, calculating a response value of the N-i antenna array element about a scanning angle fai _ scan symmetric point by interpolation, and recording the response value as cv'N-iAnd calculating (cv)N-i+cv'N-i) The data is used as the corrected response data of the N-i antenna array element;
step 7, sequentially calculating the corrected response data of the other 2 × i antenna array elements selected in the step 2 according to the method in the step 6, sequentially storing the 2 × i +1 data, and marking as cv1, wherein the cv1 is a 2 × i +1 dimensional complex array;
and step 8, calculating correlation coefficients R of cv and cv 1:
in the above formula, x is cv data,
mean of cv data, y isThe cv1 data of the data,
mean cv1 data;
and 9, in the scanning range, fai _ scan is taken once every interval delta theta, the steps 5 to 8 are repeated, the correlation coefficients of cv and cv1 are sequentially calculated, a scanning angle-correlation coefficient curve is obtained, the scanning angle corresponding to the maximum correlation coefficient point is the incoming wave direction, and the frequency point direction finding is finished.
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Cited By (2)
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| CN114415107A (en) * | 2022-04-01 | 2022-04-29 | 中国电子科技集团公司第二十九研究所 | Polarization measurement method and system for improving array direction finding precision and storage medium |
| CN114609579A (en) * | 2022-03-23 | 2022-06-10 | 电子科技大学 | Defocusing direction finding error correction method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114609579A (en) * | 2022-03-23 | 2022-06-10 | 电子科技大学 | Defocusing direction finding error correction method |
| CN114415107A (en) * | 2022-04-01 | 2022-04-29 | 中国电子科技集团公司第二十九研究所 | Polarization measurement method and system for improving array direction finding precision and storage medium |
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