CN115015846A - Generalized self-adaptive monopulse angle measurement method based on conformal array antenna - Google Patents
Generalized self-adaptive monopulse angle measurement method based on conformal array antenna Download PDFInfo
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Abstract
The invention discloses a generalized self-adaptive monopulse angle measurement method based on conformal array antennas, which comprises the following steps: acquiring a guide vector direction cosine expression and a sub-array level adaptive monopulse ratio of a target signal received by a conformal array antenna; obtaining a partial derivative function expression of a guide vector of a transmitting signal of a conformal array antenna; solving a slope correction matrix and a deviation correction quantity of a monopulse ratio of the conformal array antenna, and constructing a generalized monopulse angle measurement formula of the conformal array antenna; and solving the direction cosine of the target signal by using a conformal array antenna generalized monopulse angle measurement formula so as to obtain the pitch angle and the azimuth angle of the target signal. The angle measurement method does not depend on the slope of a single pulse ratio curve obtained according to the self-adaptive sum and difference beam direction diagram, and the angle measurement error is minimum; the system freedom degree cannot be additionally lost, and better angle measurement performance can be kept along with the increase of the number of the sidelobe interferences.
Description
Technical Field
The invention belongs to the technical field of radar signal processing, and particularly relates to a generalized self-adaptive monopulse angle measurement method based on a conformal array antenna.
Background
With the advance of phased array radar technology, conformal array antennas are becoming an important direction for the development of modern radars. The conformal array antenna is arranged on the radar seeker, so that the good aerodynamic performance is achieved, the scattering sectional area of the radar can be effectively reduced, and the radar has low detectability. The conformal array antenna self-adaptive monopulse angle measurement technology is researched, and the angle tracking of the radar to the target can be realized.
In practical situations, the conformal array antenna has a large number of array elements, a large number of channels are required for array element-level adaptive processing, and a complex system structure, so that in order to reduce cost, simplify the system structure, reduce the calculation amount of an algorithm, reduce the complexity of the system, and meet the requirement of system real-time performance, the conformal array antenna needs to be subjected to subarray division processing. At present, a great deal of research is carried out on the angle measurement problem of linear arrays or planar arrays, and the existing self-adaptive monopulse angle measurement methods can be roughly divided into three categories: the first type is a sum and difference beam simultaneous zero setting technology, which requires the known interference direction and has poor self-adaptive capability; the second type is based on a self-adaptive directional diagram shape preserving technology, namely, a linear constraint method and other methods are adopted to carry out self-adaptive directional diagram shape preserving, so that the monopulse angle identifying characteristic is not distorted as much as possible; the third type is a monopulse angle measurement technique based on a maximum likelihood method, which is proposed by Davies et al based on an equidistant linear array model, but the method requires a difference beam as a derivative of a sum beam, which is not satisfied in most applications. Nickel provides a self-adaptive monopulse angle measurement algorithm under the condition of arbitrary sum and difference beams on the basis, and the method has wider applicability.
The method aims at the research of the conformal array antenna angle measurement algorithm, and the published documents are less. When the conformal array antenna adopts the traditional adaptive monopulse angle measurement, although the angle measurement of a target can be realized while interference signals are suppressed, the angle measurement performance of the conformal array antenna depends on a sum-difference beam directional diagram, and when the number of interference is more or the interference is positioned near a main beam, the main beam of the sum-difference beam is distorted due to null formed by the adaptive beam, so that the error of the traditional adaptive monopulse angle measurement is increased; a conformal array antenna constraint self-adaptive single-pulse angle measurement method is proposed in 2013 by ZhaoYingjun et al, and the method realizes shape preservation of a main beam by applying constraint conditions to the main beam, so that the sum-difference single-pulse angle measurement performance is guaranteed, but the applied additional constraint conditions consume the spatial domain freedom degree of the system.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a generalized adaptive monopulse angle measurement method based on a conformal array antenna, which does not depend on the slope of a monopulse ratio curve obtained according to adaptive sum and difference beam patterns, and also does not lose spatial degree of freedom, and when solving a steering vector of the conformal array antenna, the shielding effect of the conformal array antenna and the difference of antenna pattern of each array element are taken into consideration, wherein the conformal array antenna can be a uniform conformal array antenna, or a sparse conformal array antenna obtained after array arrangement optimization. The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a generalized self-adaptive monopulse angle measurement method based on conformal array antennas, which comprises the following steps:
s1: acquiring a guide vector direction cosine expression and a sub-array level adaptive monopulse ratio of a target signal received by a conformal array antenna;
s2: obtaining a partial derivative function expression of a guide vector of a transmitting signal of a conformal array antenna;
s3: solving a slope correction matrix and a deviation correction quantity of the monopulse ratio of the conformal array antenna, and constructing a generalized monopulse angle measurement formula of the conformal array antenna;
s4: and solving the direction cosine of the target signal by using a conformal array antenna generalized monopulse angle measurement formula, and further solving the pitch angle and the azimuth angle of the target signal.
In an embodiment of the present invention, the S1 includes:
s1.1: obtaining a guide vector direction cosine expression of a target signal received by a conformal array antenna;
s1.2: carrying out dimensionality reduction processing on the conformal array antenna to obtain sub-array level self-adaptive sum beam output power, sub-array level self-adaptive pitch difference beam output power and sub-array level self-adaptive azimuth difference beam output power of the conformal array antenna;
s1.3: and obtaining a subarray-level pitching dimension self-adaptive monopulse ratio and a subarray-level azimuth dimension self-adaptive monopulse ratio of the conformal array antenna by utilizing each output power.
In one embodiment of the present invention, the S1.1 includes:
obtaining a direction vector direction cosine expression of a target signal received by the conformal array antenna:
wherein r is i ＝[x i y i z i ]Coordinates of the ith antenna element are shown, i is 1,2, … N, N is the total number of antenna elements, f 1 f 2 ... f N The corresponding directional diagram of each antenna element is shown,
represents the direction cosine of the target signal, theta represents the pitch angle of the target signal,
indicating the azimuth angle of the target signal, and lambda indicates the target signal wavelength;
will be provided with
Is recorded as v ═ u u' v]Obtaining an expansion a (u, u', v) of the directional cosine expression of the target signal steering vector:
in one embodiment of the present invention, the S1.2 includes:
dividing the conformal array antenna into a plurality of sub-arrays, and respectively obtaining sub-array level self-adaption and beam weight vectors w sub_∑ Sub-array level adaptive elevation difference beam weight vector
Sum-subarray level adaptive azimuth difference beam weight vector
Using w sub_∑ ，
And
respectively obtaining sub-array level self-adaptive sum beam output power, sub-array level self-adaptive pitch difference beam output power and sub-array level self-adaptive azimuth difference beam output power:
P sub_∑ ＝w sub_∑ x
wherein x represents an incoming wave signal received by the conformal array antenna.
In one embodiment of the present invention, the S1.3 includes:
using sub-array level adaptation and beam output power P sub_∑ Sum sub-array level adaptive elevation difference beam output power
Obtaining a subarray level pitching dimension self-adaptive monopulse ratio of the conformal array antenna:
using sub-array level adaptation and beam output power P sub_Σ Sum-sub-array level adaptive azimuth difference beam output power
Obtaining conformal array of antennasSub-array level azimuth dimension adaptive monopulse ratio of the line:
in an embodiment of the present invention, the S2 includes:
obtaining a partial derivative function expression of the conformal array antenna steering vector according to a derivation rule:
wherein, a u,t Represents the partial derivative function of conformal array antenna steering vector a (v) relative to u at v t Expression of (a) v,t Represents the partial derivative function of the conformal array antenna steering vector a (v) relative to v at v t The expression (c) of (a) is,
θ t ,
the pitch angle and the azimuth angle of the signals transmitted by the conformal array antenna are respectively shown.
In an embodiment of the present invention, the conformal array antenna generalized monopulse angle measurement formula is as follows:
wherein u is t And v t Represents the beam direction of the signals transmitted by the radar conformal array antenna,
v t ＝sinθ t ，real {. is } represents the operation of the real part,
a slope correction matrix representing the ratio of the single pulses,
the deviation correction amount is indicated.
In one embodiment of the present invention, solving a slope correction matrix and a deviation correction quantity of a monopulse ratio of a conformal array antenna comprises:
adaptive sum beam weight vector w based on sub-array level sub_∑ Sub-array level adaptive elevation difference beam weight vector
Sum-subarray level adaptive azimuth difference beam weight vector
Obtaining a slope correction matrix and a deviation correction quantity:
compared with the prior art, the invention has the beneficial effects that:
1. when the conformal array antenna has interference close to the main beam in an external environment, compared with the conventional subarray-level traditional self-adaptive monopulse angle measurement method and the subarray-level constraint self-adaptive monopulse angle measurement method, the generalized self-adaptive monopulse angle measurement method based on the conformal array antenna has better angle measurement performance while realizing interference suppression. Because the subarray-level traditional self-adaptive monopulse forms a null at an interference position in order to inhibit interference, but because the interference distance is close to a main lobe, a pitch dimension difference beam pattern is distorted, an angle discrimination curve is seriously distorted at the moment, and the pitch dimension measurement error of the subarray-level traditional self-adaptive monopulse is sharply increased; and the sub-array level constrained self-adaptive monopulse ensures the shape of a difference beam pattern by applying constraint conditions to the main beam and can offset the loss caused by partial null. The angle measurement method does not depend on the slope of a single pulse ratio curve obtained according to the self-adaptive sum and difference beam pattern, and the angle measurement error is minimum.
2. When the number of the sidelobe interferences is large, compared with a subarray-level constrained adaptive single-pulse angle measurement method, the method disclosed by the invention realizes interference suppression and has smaller angle measurement error. As the sub-array level constraint self-adaptive single pulse applies constraint conditions to the main beam, the shape of the main beam is realized, and the additional constraint conditions cause the loss of the spatial domain freedom of the system. When the number of interference exceeds the remaining spatial domain freedom degrees after the constraint condition is applied, the subarray level constraint self-adaptive monopulse angle identification curve is distorted, so that the angle measurement error of the method is increased. The angle measurement method of the invention does not additionally lose the degree of freedom of the system, and can keep better angle measurement performance along with the increase of the number of the side lobe interference.
3. Compared with the array element-level adaptive processing of the conformal array antenna, the conformal array antenna subarray-level generalized adaptive monopulse angular measurement method can simplify the system structure, reduce the calculation amount of an algorithm, reduce the complexity of the system and meet the requirement of the real-time performance of the system.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a flowchart of a generalized adaptive monopulse angle measurement method based on a conformal array antenna according to an embodiment of the present invention;
fig. 2 is a cone conformal array model in a rectangular coordinate system according to an embodiment of the present invention;
FIG. 3(a) is a pitch angle error curve for three angle measurement methods in the presence of a side lobe interference and an interference near the main beam;
FIG. 3(b) is a diagram showing the azimuth error curves of three angle measurement methods in the presence of a side lobe interference and an interference close to the main beam;
FIG. 4(a) is a pitch dimension angle measurement error curve of three angle measurement methods as the number of side lobe interferences increases;
fig. 4(b) is an azimuth angle measurement error curve of the three angle measurement methods as the number of side lobe interferences increases.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined object, a generalized adaptive single-pulse angle measurement method based on conformal array antenna according to the present invention is described in detail below with reference to the accompanying drawings and the detailed description.
The foregoing and other technical matters, features and effects of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. The technical means and effects of the present invention adopted to achieve the predetermined purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only and are not used for limiting the technical scheme of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or device that comprises a list of elements does not include only those elements but may include other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of additional like elements in the article or device comprising the element.
Referring to fig. 1, fig. 1 is a flowchart of a generalized adaptive monopulse angle measurement method based on a conformal array antenna according to an embodiment of the present invention, where the method includes the following steps:
s1: and acquiring a steering vector direction cosine expression and a sub-array level adaptive monopulse ratio of the target signal received by the conformal array antenna.
Due to the particularity of the structure of the conformal array antenna, when incoming wave signals deviate from the visual axis, part of array elements are shielded by the projectile body, so that the incoming wave signals cannot be received, and the array elements are in a non-working state at the moment, so that the shielding effect brought by the conformal array antenna is reflected. Because each array element is positioned at different spatial positions instead of in the same plane, the working environments of the array elements are different, and the normal direction of each array element is perpendicular to the surface of a conformal carrier (a carrier attached to the conformal array antenna), the main beam directions of directional diagrams of the antenna directional diagrams of the array elements are different. When an external signal is incident to the conformal array antenna, the radiation gain of each array element does not contribute to the whole conformal array antenna, and therefore, the antenna directional diagrams of the antenna array elements are different. When solving the guide vector of an incoming wave signal received by the conformal array antenna, the shielding effect and the difference of antenna directional diagrams of each array element need to be taken into account, the obtained guide vector of a target signal is a (v), and the adaptive weight vector can be obtained by combining the adaptive beam forming criterion and the algorithm.
In the present embodiment, step S1 includes:
s1.1: and obtaining a direction cosine expression of a steering vector of the target signal received by the conformal array antenna.
Assuming that the incoming wave signal received by the conformal array antenna is x, it can be expressed as:
wherein t represents the fast beat number, s (t) is the signal amplitude of the target signal, N represents the noise signal, the noise signals of the array elements are uncorrelated and are all Gaussian white noise, and N-N (0, delta) 2 I)，N(0,δ 2 I) Is a normal distribution function expression, I represents an identity matrix, delta 2 Represents the variance of the white noise data,
a steering vector representing a target signal to be calculated, and theta represents a target to be calculatedThe pitch angle of the signal is,
indicating the azimuth of the incoming wave signal to be calculated.
In this embodiment, the conformal array antenna shielding effect and the difference of antenna directional patterns of each array element are taken into consideration, and the cosine expression of the direction of the steering vector of the target signal is obtained as follows:
wherein, for the ith antenna element, the coordinate of the element i is r i ＝[x i y i z i ]I is 1,2, … N, N represents the total number of antenna elements,
abbreviated as v ═ u u' v]Where v denotes the direction cosine of the target signal, f 1 f 2 ... f N The directional diagram corresponding to each antenna array element is shown, lambda represents the wavelength of a target signal, theta represents the pitch angle of the target signal,
representing the azimuth of the target signal.
The expansion a (u, u', v) of the directional cosine expression of the target signal steering vector can then be found:
s1.2: and carrying out dimensionality reduction on the conformal array antenna to obtain the sub-array level self-adaptive sum beam output power, the sub-array level self-adaptive pitch difference beam output power and the sub-array level self-adaptive azimuth difference beam output power of the conformal array antenna.
Assuming that the received incoming wave signal is x, combining with the adaptive beam forming rule and algorithm, the adaptive weight vector w can be obtained opt In practice, inIn this case, the conformal array antenna has a large number of array elements, a large number of channels are required for array element level adaptive processing, and a complex system structure, so that in order to reduce the cost, the conformal array elements are divided into a plurality of sub-arrays for dimension reduction processing. Respectively assuming that the obtained sub-array level adaptive sum beam weight vector, the sub-array level adaptive elevation difference beam weight vector and the sub-array level adaptive azimuth difference beam weight vector of the conformal array antenna are w sub_∑ ，
And
the sub-array level adaptive sum beam output power, the sub-array level adaptive elevation difference beam output power and the sub-array level adaptive azimuth difference beam output power are respectively as follows:
P sub_∑ ＝w sub_∑ x
s1.3: and obtaining a subarray-level pitching dimension self-adaptive monopulse ratio and a subarray-level azimuth dimension self-adaptive monopulse ratio of the conformal array antenna by utilizing each output power.
In the adaptive monopulse angle measurement, an adaptive monopulse ratio (the monopulse ratio is the ratio of the difference beam output to the sum beam output) needs to be utilized, so that the subarray level pitching dimension adaptive monopulse ratio R is respectively calculated by utilizing the output powers obtained in the step S1.2 u Sum-subarray level azimuth dimension self-adaptive monopulse ratio R v 。
In particular, using sub-array level adaptation and beam output power P sub_∑ Sum sub-array level adaptive elevation difference beam output power
Obtaining a subarray level pitching dimension self-adaptive monopulse ratio of the conformal array antenna:
using sub-array level adaptation and beam output power P sub_∑ Sum-array level adaptive azimuth difference beam output power
Obtaining a subarray-level azimuth dimension self-adaptive monopulse ratio of the conformal array antenna:
s2: and acquiring a guide vector partial derivative function expression of the transmission signal of the conformal array antenna.
If the conformal array antenna is horizontally placed under the geodetic coordinate system, a common conical conformal array or a common cylindrical conformal array is taken as an example, and the cross section perpendicular to the axis is a circle and has symmetry. As shown in fig. 2, when the conformal array antenna is horizontally placed, its symmetry axis is parallel to the Y-axis, and the Y-coordinate of each array element on any layer of the ring is the same. The direction of a transmitting signal of a known radar conformal array antenna is assumed to be
V for the direction cosine at this time t It is shown that,
abbreviated as v t ＝[u t u′ t v t ]。
The cosine expression of the direction of the steering vector of the target signal received by the conformal array antenna is given as
Due to the expression of various signal steering vectorsAnd all the same, the cosine expression of the direction of the directional vector of the transmitted signal of the conformal array antenna can be obtained:
assuming that the coordinate of an array element of the conformal array antenna is known as r ═ x y z, x represents an abscissa, y represents an ordinate, and z represents a vertical coordinate, a partial derivative function expression of a steering vector of the conformal array antenna can be obtained according to a derivation rule, and the partial derivative function expression comprises the following steps:
wherein, a u,t Represents the partial derivative function of conformal array antenna steering vector a (v) relative to u at v t Expression of (a) v,t Represents the partial derivative function of the conformal array antenna steering vector a (v) with respect to v at v t The expression (c) of (a) is,
θ t ,
respectively representing the pitch angle and the azimuth angle of the signals transmitted by the conformal array antenna.
S3: and solving a slope correction matrix and a deviation correction quantity of the monopulse ratio of the conformal array antenna, and constructing a generalized monopulse angle measurement formula of the conformal array antenna.
In many radar systems, the received signal of each array element cannot be obtained in practical application, for example, a difference beam may be obtained by sub-array level beam forming; when the array surface is a non-uniform array such as a sparse array, the sum beam cannot adopt uniform weighting; the noise component in the incoming signal x is not necessarily white noise due to the presence of the interfering signal.
In view of the above, the present embodiment can obtain the generalized monopulse angle measurement formula of the conformal array antenna:
wherein u is t And v t Represents the wave beam direction of the signals transmitted by the conformal array antenna of the radar,
v t ＝sinθ t real {. is } represents the operation of the real part,
a slope correction matrix representing the ratio of the single pulses,
the deviation correction amount is indicated. R u And R v Representing the single pulse ratio in the pitch and azimuth directions, respectively.
S3.2: and solving the slope correction matrix and the deviation correction quantity of the conformal array antenna to perform linear compensation on the self-adaptive monopulse ratio.
In practical situations, the conformal array antenna has a large number of array elements, a large number of channels are required for array element level adaptive processing, and a complex system structure, so in order to reduce cost, the angle measurement method of the embodiment of the invention reduces dimensions to a sub-array level for processing, and further solves a slope correction matrix and an offset correction quantity to obtain:
wherein, w sub_Σ Representing the sub-array level adaptation and beam weight vector of the conformal array antenna,
and
respectively representing the conformal array antenna sub-array level adaptive elevation difference beam weight vector and azimuth difference beam weight vector, which are already obtained in step S1; a is u,t And a v,t The partial derivative function expression representing the radar transmission signal steering vector has been solved in step S2.
S4: and solving the direction cosine of the target signal by using a conformal array antenna generalized monopulse angle measurement formula so as to obtain the pitch angle and the azimuth angle of the target signal.
Specifically, the obtained slope correction matrix
Sum deviation correction amount
The value of (d) is substituted back to the generalized monopulse angle measurement formula, so that the direction cosines u and v of the target signal can be obtained, and the angle of the target signal can be further solved
Further, the effect of the generalized adaptive monopulse angle measurement method based on the conformal array antenna according to the embodiment of the present invention is further illustrated by the following simulation test:
(1) simulation conditions
In the simulation experiment of this embodiment, taking a conical conformal array antenna as an example, a coordinate system is established as shown in fig. 2, a pitch angle is defined as an included angle between a projection of an incoming wave signal on an XOY plane and the signal itself,
the azimuth angle of the incoming wave signal is represented, an included angle between the projection of the incoming wave signal on an XOY plane and the positive direction of a Y axis is defined as the azimuth angle, the section of the incoming wave signal vertical to the axis of the cone is a circle, the incoming wave signal has symmetry, and the conformal array antenna is divided into a plurality of linesThe method is divided into 12 subarray channels, and a nine-point constraint method is adopted in a subarray level constraint self-adaptive monopulse angular measurement method. The angle measurement performance of three methods, namely a subarray-level traditional self-adaptive monopulse angle measurement method (called traditional monopulse for short), a subarray-level constrained self-adaptive monopulse angle measurement method (called constrained monopulse for short) and a conformal array antenna subarray-level generalized self-adaptive monopulse angle measurement method (called generalized monopulse for short) provided by the invention are contrastively analyzed.
(2) Emulated content
Simulation experiment I: when a side lobe interference and an interference close to the main beam exist, angle measurement errors of the three angle measurement methods are compared. Assuming that the target signal is from (0 degree ), there exists a interference (3 degree, 0 degree) close to the main beam and a side lobe interference (15 degree, -30 degree), the dry-to-noise ratio is 60dB, monte carlo experiments are performed under different signal-to-noise ratios, and fig. 3(a) and fig. 3(b) are pitch dimension angle measurement error curves and azimuth dimension angle measurement error curves of three different angle measurement methods, respectively.
A second simulation experiment: and changing the number of side lobe interference, and comparing the change trends of error curves of the three angle measurement methods.
Assuming that the beam is directed (0 degrees and 0 degrees), the fixed signal-to-noise ratio is 20dB, the dry-to-noise ratio is set to 60dB, the number of the sidelobe interferences is changed to carry out a Monte Carlo experiment, and a pitching dimension angle measurement error curve and an azimuth dimension angle measurement error curve of three different angle measurement methods are respectively shown in fig. 4(a) and fig. 4 (b).
(3) Analysis of simulation results
As can be seen from fig. 3(a) and 3(b), when there is a side lobe interference and an interference close to the main lobe, the elevation dimension angle measurement error of the conventional single pulse at the subarray level is the largest, and the angle measurement error of the angle measurement method according to the embodiment of the present invention is always lower than that of the constrained adaptive single pulse at the subarray level. In summary, the angle measurement errors of the three methods all decrease with the increase of the input signal-to-noise ratio, and when the interference close to the main beam exists in the external environment, the angle measurement performance of the angle measurement method of the embodiment of the invention is superior to that of the sub-array level constrained adaptive single-pulse angle measurement.
As can be seen from fig. 4(a) and 4(b), with the increase of the number of the side lobe interferences, the conventional adaptive monopulse angle measurement error of the subarray level is always greater than the angle measurement errors of the other two methods, when the number of the interferences is less than 3, the constrained adaptive monopulse angle measurement error of the subarray level is less than the generalized adaptive monopulse angle measurement error of the subarray level according to the embodiment of the present invention, when the number of the interferences exceeds 3, the constrained adaptive monopulse angle measurement error of the subarray level is sharply increased, and thereafter, the angle measurement error of the angle measurement method according to the embodiment of the present invention is always less than the constrained adaptive monopulse of the subarray level.
In addition, the sub-array level constrained adaptive monopulse conforms to the main beam pattern by applying additional constraints to the main beam, but the additional constraints lose spatial freedom. When the number of the interferences is smaller than the remaining spatial domain degrees of freedom after the constraint condition is applied, the subarray level constraint self-adaptive monopulse angle measurement error is smaller, and the angle measurement performance is better; when the number of interference exceeds the remaining spatial domain freedom degrees after the constraint condition is applied, the subarray level constraint self-adaptive monopulse angle identification curve is distorted, so that the angle measurement error of the method is increased. In summary, with the increase of the number of the sidelobe interferences, the angle measurement method in the embodiment of the present invention does not depend on the slope of the monopulse ratio curve obtained according to the adaptive sum-difference beam pattern, does not lose the system degree of freedom, and can maintain a good angle measurement performance.
When the conformal array antenna has interference close to the main beam in an external environment, compared with the conventional subarray-level traditional self-adaptive monopulse angle measurement method and the subarray-level constraint self-adaptive monopulse angle measurement method, the generalized self-adaptive monopulse angle measurement method based on the conformal array antenna has better angle measurement performance while realizing interference suppression. Because the subarray-level traditional self-adaptive monopulse forms a null at an interference position in order to inhibit interference, but because the interference distance is close to a main lobe, a pitch dimension difference beam pattern is distorted, an angle identifying curve is seriously distorted at the moment, and the error of the pitch dimension measurement of the subarray-level traditional self-adaptive monopulse is sharply increased; and the sub-array level constrained self-adaptive single pulse applies constraint conditions to the main beam, so that a poor beam pattern is conformal, and loss caused by a part of null can be offset. The angle measurement method does not depend on the slope of a single pulse ratio curve obtained according to the self-adaptive sum and difference beam pattern, and the angle measurement error is minimum. When the number of the sidelobe interferences is large, compared with a subarray-level constrained adaptive single-pulse angle measurement method, the method disclosed by the invention realizes interference suppression and has smaller angle measurement error. As the sub-array level constraint self-adaptive single pulse applies constraint conditions to the main beam, the shape of the main beam is realized, and the additional constraint conditions cause the loss of the spatial domain freedom of the system. When the number of interference exceeds the remaining spatial domain freedom degrees after the constraint condition is applied, the subarray level constraint self-adaptive monopulse angle identification curve is distorted, so that the angle measurement error of the method is increased. The angle measurement method of the invention does not additionally lose the degree of freedom of the system, and can keep better angle measurement performance along with the increase of the number of the side lobe interference.
In addition, compared with the conformal array antenna array element level self-adaptive processing, the conformal array antenna subarray level generalized self-adaptive monopulse angular measurement method can simplify the system structure, reduce the calculation amount of an algorithm, reduce the complexity of the system and meet the requirement of the real-time performance of the system.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (8)
1. A generalized adaptive monopulse angle measurement method based on conformal array antennas is characterized by comprising the following steps:
s1: acquiring a guide vector direction cosine expression and a sub-array level adaptive monopulse ratio of a target signal received by a conformal array antenna;
s2: obtaining a partial derivative function expression of a guide vector of a transmitting signal of a conformal array antenna;
s3: solving a slope correction matrix and a deviation correction quantity of the monopulse ratio of the conformal array antenna, and constructing a generalized monopulse angle measurement formula of the conformal array antenna;
s4: and solving the direction cosine of the target signal by using a conformal array antenna generalized monopulse angle measurement formula so as to obtain the pitch angle and the azimuth angle of the target signal.
2. The generalized adaptive monopulse goniometry method based on conformal array antenna according to claim 1, wherein said S1 comprises:
s1.1: obtaining a guide vector direction cosine expression of a target signal received by a conformal array antenna;
s1.2: carrying out dimensionality reduction processing on the conformal array antenna to obtain sub-array level self-adaptive sum beam output power, sub-array level self-adaptive pitch difference beam output power and sub-array level self-adaptive azimuth difference beam output power of the conformal array antenna;
s1.3: and obtaining a subarray-level pitching dimension self-adaptive monopulse ratio and a subarray-level azimuth dimension self-adaptive monopulse ratio of the conformal array antenna by utilizing each output power.
3. The generalized adaptive monopulse angular measurement method based on conformal array antenna according to claim 2, wherein said S1.1 comprises:
obtaining a direction vector direction cosine expression of a target signal received by the conformal array antenna:
wherein r is i ＝[x i y i z i ]Coordinates of the ith antenna element are shown, i is 1,2, … N, N is the total number of antenna elements, f 1 f 2 ...f N The corresponding directional diagram of each antenna element is shown,
represents the direction cosine of the target signal, theta represents the pitch angle of the target signal,
indicating the azimuth angle of the target signal, and lambda indicates the target signal wavelength;
will be provided with
Is recorded as v ═ u u' v]Obtaining an expansion a (u, u', v) of the directional cosine expression of the target signal steering vector:
4. the generalized adaptive monopulse angular measurement method based on conformal array antenna according to claim 2, wherein said S1.2 comprises:
dividing the conformal array antenna into a plurality of sub-arrays, and respectively obtaining sub-array level self-adaption and beam weight vectors w sub_Σ Sub-array level adaptive elevation difference beam weight vector
Sum-subarray level adaptive azimuth difference beam weight vector
Using w sub_Σ ，
And
respectively obtaining sub-array level self-adaptive sum beam output power, sub-array level self-adaptive pitch difference beam output power and sub-array level self-adaptive azimuth difference beam output power:
P sub_Σ ＝w sub_Σ x
wherein x represents an incoming wave signal received by the conformal array antenna.
5. The generalized adaptive monopulse angular measurement method based on conformal array antenna according to claim 4, wherein S1.3 comprises:
using sub-array level adaptation and beam output power P sub_Σ Sum sub-array level adaptive elevation difference beam output power
Obtaining a subarray level pitching dimension self-adaptive monopulse ratio of the conformal array antenna:
using sub-array level adaptation and beam output power P sub_∑ Sum-array level adaptive azimuth difference beam output power
Obtaining a subarray-level azimuth dimension self-adaptive monopulse ratio of the conformal array antenna:
6. the generalized adaptive monopulse goniometry method based on conformal array antenna according to claim 4, wherein said S2 comprises:
obtaining a partial derivative function expression of the conformal array antenna steering vector according to a derivation rule:
wherein, a u,t Represents the partial derivative function of conformal array antenna steering vector a (v) relative to u at v t Expression of (a) v,t Represents the partial derivative function of the conformal array antenna steering vector a (v) relative to v at v t The expression (c) of (a) is,
θ t ,
respectively representing the pitch angle and the azimuth angle of the signals transmitted by the conformal array antenna.
7. The conformal array antenna-based generalized adaptive monopulse angle measurement method according to claim 6, wherein the conformal array antenna generalized monopulse angle measurement formula is as follows:
wherein u is t And v t Represents the beam direction of the signals transmitted by the radar conformal array antenna,
v t ＝sinθ t real {. is } represents the operation of the real part,
a slope correction matrix representing the ratio of the single pulses,
the deviation correction amount is indicated.
8. The generalized adaptive monopulse angular measurement method according to claim 7, wherein solving slope correction matrix and deviation correction of monopulse ratio of conformal array antenna comprises:
adaptive sum beam weight vector w based on sub-array level sub_∑ Sub-array level adaptive elevation difference beam weight vector
Sum-subarray level adaptive azimuth difference beam weight vector
Obtaining a slope correction matrix and a deviation correction quantity:
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