CN109946689B - Target detection method based on spatial energy focusing technology - Google Patents
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Abstract
The invention discloses a target detection method based on a space energy focusing technology, which can effectively compress space energy on different programs and improve the energy of the space energy in an interference band by constructing a rectangular time invariant space point focusing frequency control array structure and applying the structure to a detection system to detect a target, thereby effectively improving the accuracy of target detection. The rectangular time-invariant space point focusing frequency control array provided by the invention has wide prospect in the aspect of radar detection, can be widely used in radar and wireless communication and has strong practicability, and more array structures can be explored based on the structure.
Description
Technical Field
The invention belongs to the technical field of microwave radars and wireless communication, and particularly relates to a design of a target detection method based on a space energy focusing technology.
Background
The array antenna technology has wide application in the fields of radar, wireless communication, sonar, navigation and the like, and the antennas can have different arrangement modes according to the requirements of practical application, and can be divided into linear arrays and area arrays at most. Compared with a single antenna, the array antenna can realize the functions of beam scanning, beam shaping, multi-beam and the like. Researchers at home and abroad often study performance and application according to the functional classification of array antennas, such as phased array antennas, frequency scanning antennas, adaptive antennas, Multiple Input Multiple Output (MIMO) antennas, and the like. In recent years, new arrays derived from phased arrays and MIMO have attracted much attention, such as phased arrays-MIMO, differential arrays, frequency control arrays, and the like, and these new arrays bring more degrees of freedom and wide application prospects. However, the target detection accuracy of the phased array or the existing frequency control array in the radar target detection system needs to be improved, so that it is very significant if the target detection accuracy can be improved by compressing and converging the spatial energy to a certain extent on the basis of the phased array or the frequency control array.
Phased array radars differ from conventional mechanical scanning radars in that they are widely used for radar target detection and imaging applications because they allow for free spatial scanning of the beam. Generally, the same signal is transmitted (received) by each array element of the phased array radar, the beam direction is controlled by accessing a phase shifter at the output end of each array element, and the spatial domain scanning of the beam can be realized by adjusting the phase shift amount of the phase shifter. In physical essence, the phased array antenna mainly utilizes coherence characteristics of radiation fields of antenna units, and completes convergence and concentration of radiation energy in an angle space dimension through interference superposition of electromagnetic fields, a typical process of the phased array antenna is shown in fig. 1, and it is easy to find from fig. 1 that the energy convergence and concentration process is mainly performed in the angle dimension, and energy is not converged and concentrated in a distance dimension.
The frequency control array is firstly proposed in the radar annual meeting in the united states in 2006, and unlike the phase control array, a small frequency offset (the frequency offset is far smaller than the carrier center frequency) exists between each adjacent antenna of the frequency control array. Because the frequency of the antenna transmitting signals is different, the phase superposition relations caused by different distances are different, so that the phases on certain distance units are mutually superposed to form wave crests, and the phases on certain distance units are mutually offset to form wave troughs, which inevitably causes the beam pattern to be not only related to the angle but also related to the distance, which is the main difference between a frequency control array and a phased array and also is the most main characteristic of the frequency control array.
As can be seen from fig. 2, the spatial energy compression of the frequency control array can make up for the disadvantage that the phased array cannot perform energy convergence in the distance dimension, so that the spatial energy compression of the frequency control array is compressed in the distance dimension and the angle dimension at the same time, which greatly improves the target detection precision of the radar. However, the frequency control array also has some problems, that is, after the spatial energy of the frequency control array is compressed into a focal zone, as can be seen from fig. 2, the focal zone is an irregular focal zone, and the accuracy of the distance calculation for the position where the frequency control array is located in the radar target detection system is low.
Disclosure of Invention
The invention aims to provide a target detection method based on a spatial energy focusing technology, which has higher energy convergence on spatial target detection, thereby having higher detection precision and further improving the accuracy of target detection.
The technical scheme of the invention is as follows: an object detection method based on a spatial energy focusing technology comprises the following steps:
and S1, generating an initial signal of the set carrier frequency through the signal source.
And S2, determining the row number N and the column number M of the rectangular time-invariant space point focusing frequency control array.
And S3, distributing the initial signal into N × M paths of frequency source signals by adopting a power divider.
And S4, setting the frequency offset value of each path of frequency source signal through the FPGA digital processor, and performing corresponding frequency offset on each path of frequency source signal through N × M phase-locked loops.
And S5, amplifying the frequency source signal after frequency offset, and outputting the amplified frequency source signal as a detection signal to a corresponding antenna of the rectangular time-invariant space point focusing frequency control array.
And S6, transmitting detection signals to the target through the rectangular time-invariant space point focusing frequency control array, receiving echo signals, and calculating according to echo time to obtain the distance of the detection target.
Further, step S4 includes the following substeps:
and S41, numbering the frequency source signals according to the coordinate position of each antenna in the rectangular time-invariant space point focusing frequency control array, and enabling the frequency source signals to correspond to the antennas in the rectangular time-invariant space point focusing frequency control array one by one.
S42, obtaining array element parameters g [ n, m ] of the rectangular time invariant space point focusing frequency control array by adopting an artificial bee colony algorithm in the FPGA digital processor.
And S43, calculating the line frequency offset value and the column frequency offset value of each path of frequency source signal according to the array element parameters g [ n, m ].
And S44, performing corresponding frequency offset on each path of frequency source signal by using a phase-locked loop according to the row frequency offset value and the column frequency offset value to obtain a frequency source signal after frequency offset.
Further, the calculation formula of the row frequency offset value and the column frequency offset value in step S43 is:
wherein Δ fxAnd Δ fyRespectively representing a line frequency offset value and a column frequency offset value, N and m respectively representing a line ordinal number and a column ordinal number of an antenna in the rectangular time-invariant space point focusing frequency control array, wherein N is 1, 2. M1, 2, e, M, θ0The elevation angle between the rectangular time-invariant space point focusing frequency control array and a target point is shown, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, R0Representing the distance from the focus frequency control array to the target point at the constant space point in the case of rectangle, c is the speed of light, f0Is the carrier frequency.
Further, the frequency source signal after the frequency offset in step S44 is expressed as:
f(n,m)＝f0+nΔfx+mΔfy
wherein f is(n,m)Representing the frequency, f, of the n-th row and m-th column of antennas in a rectangular time-invariant spatial point focusing frequency-controlled array0For carrier frequency, Δ fxAnd Δ fyRespectively, row and column frequency offset values.
Further, the far field array factor AF of the rectangular time invariant spatial point focusing frequency control array is:
n and m respectively represent the row ordinal number and the column ordinal number of the antenna in the rectangular time-invariant space point focusing frequency control array, and N is 1, 2. M1, 2, M, j is an imaginary unit, g [ n, M]Is an array element parameter of the rectangular time-invariant space point focusing frequency control array, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, and theta0Represents the elevation angle between the rectangular invariant space point focusing frequency control array and the target point,
the azimuth angle between the rectangular invariant space point focusing frequency control array and a target point is shown, theta represents the elevation angle between the rectangular invariant space point focusing frequency control array and any point in the space,
representing the azimuth angle, R, of the rectangular time-invariant spatial point focusing frequency control array and any point in space0The distance from the constant space point focusing frequency control array to the space point in the rectangular shape is shown, c is the speed of light,
representing the distance from the focus frequency control array to the focus point, f, of the invariant space point in the case of a rectangle0Is the carrier frequency.
Further, the distance calculation formula of the detection target in step S6 is:
Rm＝ctm/2
wherein R ismIndicating the distance of the detected object, c is the speed of light, tmIs the echo time.
The invention has the beneficial effects that:
(1) the invention provides a rectangular time invariant space point focusing frequency control array structure, which has more application scenes compared with the traditional linear array frequency control array structure and can realize fixed point focusing in a three-dimensional space.
(2) The rectangular time-invariant space point focusing frequency control array is applied to target detection, and appropriate parameters are selected in combination with actual conditions, so that space energy can be effectively compressed on different programs, the energy of the space energy in an interference band is improved, and the accuracy of target detection is effectively improved.
(3) The rectangular time-invariant space point focusing frequency control array provided by the invention has wide prospect in the aspect of radar detection, can be widely used in radar and wireless communication and has strong practicability, and more array structures can be explored based on the structure.
Drawings
Fig. 1 is a schematic diagram illustrating spatial energy compression of a phased array in the prior art.
Fig. 2 is a schematic diagram illustrating spatial energy compression of a frequency control array in the prior art.
Fig. 3 is a schematic structural diagram of a rectangular time-invariant spatial point focusing frequency control array target detection system according to an embodiment of the present invention.
Fig. 4 is a flowchart of a target detection method based on a spatial energy focusing technique according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a phased array rectangular array according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of a rectangular time-invariant spatial point focusing frequency control array model according to an embodiment of the present invention.
Fig. 7 is a schematic diagram illustrating a focusing effect of a frequency controlled lattice point according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is to be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, not to limit the scope of the invention.
The embodiment of the invention provides a target detection method based on a spatial energy focusing technology, which comprises the following steps S1-S6 as shown in fig. 3 and 4 together:
and S1, generating an initial signal of the set carrier frequency through the signal source.
In the embodiment of the invention, the carrier frequency is set to be 3 GHz.
And S2, determining the row number N and the column number M of the rectangular time-invariant space point focusing frequency control array.
And S3, distributing the initial signal into N × M paths of frequency source signals by adopting a power divider.
In the embodiment of the present invention, N is 5, and M is 5, so that 25(5 × 5) frequency source signals are generated in total.
And S4, setting the frequency offset value of each path of frequency source signal through the FPGA digital processor, and performing corresponding frequency offset on each path of frequency source signal through N × M phase-locked loops.
The step S4 includes the following substeps S41-S44:
and S41, numbering the frequency source signals according to the coordinate position of each antenna in the rectangular time-invariant space point focusing frequency control array, and enabling the frequency source signals to correspond to the antennas in the rectangular time-invariant space point focusing frequency control array one by one.
S42, obtaining array element parameters g [ n, m ] of the rectangular time invariant space point focusing frequency control array by adopting an artificial bee colony algorithm in the FPGA digital processor.
S43, calculating according to the array element parameters g [ n, m ] to obtain the line frequency offset value and the column frequency offset value of each path of frequency source signal, wherein the calculation formula of the line frequency offset value and the column frequency offset value is as follows:
wherein Δ fxAnd Δ fyRespectively representing a line frequency offset value and a column frequency offset value, N and m respectively representing a line ordinal number and a column ordinal number of an antenna in the rectangular time-invariant space point focusing frequency control array, wherein N is 1, 2. M1, 2, e, M, θ0The elevation angle between the rectangular time-invariant space point focusing frequency control array and a target point is shown, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, R0Representing the distance from the focus frequency control array to the target point at the constant space point in the case of rectangle, c is the speed of light, f0Is the carrier frequency.
S44, according to the line frequency offset value and the column frequency offset value, performing corresponding frequency offset on each path of frequency source signal by using a phase-locked loop to obtain a frequency source signal after frequency offset, wherein the frequency source signal after frequency offset has an expression as follows:
f(n,m)＝f0+nΔfx+mΔfy(2)
wherein f is(n,m)Representing the frequency, f, of the n-th row and m-th column of antennas in a rectangular time-invariant spatial point focusing frequency-controlled array0For carrier frequency, Δ fxAnd Δ fyRespectively, row and column frequency offset values.
And S5, amplifying the frequency source signal after frequency offset, and outputting the amplified frequency source signal as a detection signal to a corresponding antenna of the rectangular time-invariant space point focusing frequency control array.
S6, transmitting a detection signal to a target and receiving an echo signal through a rectangular time invariant space point focusing frequency control array, and calculating the distance of the detection target according to the echo time, wherein the calculation formula is as follows:
Rm＝ctm/2 (3)
wherein R ismIndicating the distance of the detected object, c is the speed of light, tmIs the echo time.
In the embodiment of the invention, the detection system shown in fig. 3 is constructed by adopting the rectangular time-invariant spatial point focusing frequency control array, so as to detect the target distance, and compared with the traditional linear array frequency control array structure, the method has more application scenes and can realize fixed point focusing in a three-dimensional space. The specific construction principle and process of the rectangular time invariant space point focusing frequency control array are as follows:
as shown in fig. 5, a schematic structural diagram of a typical phased array rectangular array antenna is provided, and through coordinated control of phase and amplitude of feed signals of antenna elements in a phased array system, convergence and concentration of emitted electromagnetic energy in different spatial direction angles can be achieved, and the basic theoretical basis is as follows:
the propagation formula for a phased array is:
where s (-) phased array electromagnetic wave propagation function, t is forward propagation time of energy in the phased array, i is an imaginary unit, N represents the number of rows of the array antenna, M represents the number of columns of the array antenna, and R represents the number of rows of the array antenna0Representing the distance, theta, of the target point to the antenna array0Represents the elevation angle of the target point and the antenna array,
representing the azimuth angle of the target point and the antenna array,
indicating the distance of the focal point to the antenna array,
representing the elevation angle of the focal point and the antenna array,
indicating the azimuth angle, phi, of the focal point and the antenna arraynmThe coordinate position is represented as (N, m) phase of the transmission signal, N being 1, 2.., N; m1, 2, M, c is the speed of light, ωxIs the transverse angular frequency, omega, of the antenna arrayyIs the longitudinal angular frequency, omega, of the antenna array0xTransverse angular frequency, omega, of the focal point0yIs the longitudinal angular frequency of the focal spot and has:
ωx＝πΔfx(5)
ωy＝πΔfy(6)
wherein Δ fxAnd Δ fyRespectively representing the row and column frequency offset values, dx and dy respectively representing the transverse and longitudinal differential distances of the focal point, λcRepresenting the wavelength of light.
The theoretical basis of the phased array is provided, and a rectangular time-invariant space point focusing frequency control array model is provided on the basis, as shown in fig. 6.
Because time-invariant spatial focusing needs to be realized, the time factor in the propagation formula must be eliminated, and a nonlinear formula needs to be constructed to counteract the influence of the time factor, namely formula (1):
wherein Δ fxAnd Δ fyRespectively representing the line frequency offset value and the column frequency offset value, and n and m respectively representing the invariant spatial point focusing frequency control when the rectangle is formedThe array antenna comprises a row number and a column number of antennas in the array, wherein N is 1, 2. M1, 2, e, M, θ0The elevation angle between the rectangular time-invariant space point focusing frequency control array and a target point is shown, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, R0Representing the distance from the focus frequency control array to the target point at the constant space point in the case of rectangle, c is the speed of light, f0Is the carrier frequency.
Meanwhile, order:
substituting the formula (1) and the formula (9) into the formula (4) to obtain the far field array factor AF of the rectangular time invariant space point focusing frequency control array as follows:
n and m respectively represent the row ordinal number and the column ordinal number of the antenna in the rectangular time-invariant space point focusing frequency control array, and N is 1, 2. M1, 2, M, j is an imaginary unit, g [ n, M]Is an array element parameter of the rectangular time-invariant space point focusing frequency control array, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, and theta0Represents the elevation angle between the rectangular invariant space point focusing frequency control array and the target point,
the azimuth angle between the rectangular invariant space point focusing frequency control array and a target point is shown, theta represents the elevation angle between the rectangular invariant space point focusing frequency control array and any point in the space,
representing the azimuth angle, R, of the rectangular time-invariant spatial point focusing frequency control array and any point in space0The distance from the constant space point focusing frequency control array to the space point in the rectangular shape is shown, c is the speed of light,
representing a rectangular time invariant space pointDistance from focusing frequency control array to focusing point, f0Is the carrier frequency.
At the focus point
Where the array element phase of the array is 0, producing a maximum value, and at non-focusing points, where the field value is non-maximum due to the phase not being 0, the pair g n, m]A better focus spot can be achieved by performing parameter optimization. When t is 300ns, the energy distribution diagram of the frequency control array space is shown in fig. 7, and as can be seen from fig. 7, the effect of spatial point focusing is basically achieved.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (2)
1. A target detection method based on a spatial energy focusing technology is characterized by comprising the following steps:
s1, generating an initial signal of a set carrier frequency through a signal source;
s2, determining the number of rows N and the number of columns M of the rectangular time-invariant space point focusing frequency control array;
s3, distributing the initial signal to N × M frequency source signals by adopting a power divider;
s4, setting a frequency offset value of each path of frequency source signal through the FPGA digital processor, and performing corresponding frequency offset on each path of frequency source signal through N × M phase-locked loops;
s5, amplifying the frequency source signal after frequency offset, and outputting the amplified frequency source signal as a detection signal to a corresponding antenna of the rectangular time-invariant space point focusing frequency control array;
s6, transmitting detection signals to the target through the rectangular time-invariant space point focusing frequency control array, receiving echo signals, and calculating according to echo time to obtain the distance of the detection target;
the step S4 includes the following sub-steps:
s41, numbering frequency source signals according to the coordinate position of each antenna in the rectangular time invariant space point focusing frequency control array, and enabling the frequency source signals to correspond to the antennas in the rectangular time invariant space point focusing frequency control array one by one;
s42, obtaining array element parameters g [ n, m ] of the rectangular time invariant space point focusing frequency control array by adopting an artificial bee colony algorithm in the FPGA digital processor;
s43, calculating according to the array element parameters g [ n, m ] to obtain the line frequency offset value and the column frequency offset value of each path of frequency source signal;
s44, performing corresponding frequency offset on each path of frequency source signal by using a phase-locked loop according to the row frequency offset value and the column frequency offset value to obtain a frequency source signal after frequency offset;
the calculation formula of the row frequency offset value and the column frequency offset value in step S43 is as follows:
wherein Δ fxAnd Δ fyRespectively representing a line frequency offset value and a column frequency offset value, N and m respectively representing a line ordinal number and a column ordinal number of an antenna in the rectangular time-invariant space point focusing frequency control array, wherein N is 1, 2. M1, 2, e, M, θ0The elevation angle between the rectangular time-invariant space point focusing frequency control array and a target point is shown, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, R0Representing the distance from the focus frequency control array to the target point at the constant space point in the case of rectangle, c is the speed of light, f0Is the carrier frequency;
the frequency source signal expression after the frequency offset in step S44 is:
f(n,m)＝f0+nΔfx+mΔfy
wherein f is(n,m)Representing the frequency, f, of the n-th row and m-th column of antennas in a rectangular time-invariant spatial point focusing frequency-controlled array0For carrier frequency, Δ fxAnd ΔfyRespectively representing a row frequency offset value and a column frequency offset value;
the far field array factor AF of the rectangular time invariant space point focusing frequency control array is as follows:
n and m respectively represent the row ordinal number and the column ordinal number of the antenna in the rectangular time-invariant space point focusing frequency control array, and N is 1, 2. M1, 2, M, j is an imaginary unit, g [ n, M]Is an array element parameter of the rectangular time-invariant space point focusing frequency control array, t is the forward propagation time of energy in the time-invariant space point focusing frequency control array, and theta0Represents the elevation angle between the rectangular invariant space point focusing frequency control array and the target point,
the azimuth angle between the rectangular invariant space point focusing frequency control array and a target point is shown, theta represents the elevation angle between the rectangular invariant space point focusing frequency control array and any point in the space,
representing the azimuth angle, R, of the rectangular time-invariant spatial point focusing frequency control array and any point in space0The distance from the constant space point focusing frequency control array to the space point in the rectangular shape is shown, c is the speed of light,
representing the distance from the focus frequency control array to the focus point, f, of the invariant space point in the case of a rectangle0Is the carrier frequency.
2. The object detection method according to claim 1, wherein the distance calculation formula of the detected object in the step S6 is:
Rm＝ctm/2
wherein R ismIndicating the distance of the detected object, c is the speed of light, tmIs the echo time.
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