A coherent fda radar quantitative transmit pattern design method

Abstract

The application discloses a kind of phase correlation FDA radar quantitative transmit pattern design method, the application realizes the quantitative design of the gain of the transmit pattern in multiple discontinuous regions of interest in observation space, improves the design freedom of FDA radar.Meanwhile, the application does not constrain the baseband waveform of phase correlation FDA radar, and no longer depends on the linear frequency modulation waveform to realize the design of pattern.In addition, the technology is based on phase correlation FDA radar, and compared with traditional MIMO radar, it does not depend on complex multi-dimensional coded waveform optimization design, and the computational complexity is low.The application can be widely applied to the related application of all-digital array radar, such as air search, space monitoring.

Description

Technical Field

[0001] This invention relates to the field of array signal processing technology, and more specifically, to a method for designing a quantitative transmission pattern for a coherent FDA radar. Background Technology

[0002] Frequency Diverse Array (FDA) radar achieves uniform and continuous scanning of a large-scale spatial domain by introducing small carrier frequency increments between array elements. The beam-scanning characteristics of coherent FDA radar are significant for applications requiring wide coverage of large-scale observation spaces, such as air search, air surveillance, and space monitoring. Research shows that, in achieving wide spatial coverage, coherent FDA radar offers higher transmit angular resolution compared to traditional digital array radars with a wide transmit-narrow receive mode. Furthermore, compared to orthogonal multiple-input multiple-output (MIMO) radar, coherent FDA radar does not rely on complex baseband waveform optimization design, resulting in lower computational complexity.

[0003] However, in actual observation, targets of interest within the observation space may be concentrated in several discontinuous regions of interest (ROIs). In such cases, transmission pattern design is needed to achieve higher transmission gain within a specified ROI angular range. Simultaneously, wide coverage of a large-scale observation space may be affected by potential interference and clutter signals from different directions. Therefore, pattern design is necessary to reduce transmission gain from the direction of interference signals. Thus, transmission pattern design is of great significance for the practical application of coherent FDA radar. Existing research has only proposed one method for designing coherent FDA radar transmission patterns based on piecewise linear frequency modulated (LFM) waveforms. However, this method not only requires the baseband waveform to be LFM but also fails to achieve quantitative and differentiated design of transmission gain within the ROI. These issues mean that there is still considerable room for improvement in the transmission pattern design method for coherent FDA radar. Summary of the Invention

[0004] The purpose of this invention is to provide a quantitative transmission pattern design method for coherent FDA radar, which utilizes the intra-pulse beam scanning characteristics of coherent FDA radar to achieve flexible control over the beam illumination space and illumination time, and realizes quantitative and differentiated design of transmission gain in different ROIs.

[0005] This invention provides a quantitative transmission pattern design method for a coherent FDA radar. The transmission array of the coherent FDA radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmission array includes M transmission elements spaced apart, where the M transmission elements are arranged sequentially from the first transmission element to the Mth transmission element, and M is an integer greater than or equal to 2. The spacing d between adjacent transmission elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmission element. The mth transmission element has a transmitted signal s of the mth transmission element. m (t), m is an integer greater than or equal to 1 and less than or equal to M, there is a frequency difference Δf between the transmitted signals of adjacent transmitting array elements, Δf << f0, f0 is the center frequency, including the following steps: Step S1: Set K regions of interest in the observation space, the K regions of interest are the first region of interest to the Kth region of interest, K is an integer greater than or equal to 2; the set of angle intervals of the K regions of interest is [Θ1,Θ2,...,Θ K ], the angle interval Θ of any k-th region of interest k =[θ k,start ,θ k,end ], And satisfy k is an integer greater than or equal to 1 and less than or equal to K; Step S2: Set the set from the first transmit gain of the first region of interest to the Kth transmit gain of the Kth region of interest as [ΔG1, ΔG2, ..., ΔG K ], any k-th transmit gain ΔG k Defined as ΔG k =max(g(Θ) k ))-G l ΔG k =max(g(Θ) k ))-G l ;max(g(Θ) k )) represents the maximum gain of the emission pattern in the k-th region of interest, G l S3: The set [ΔG1, ΔG2, ..., ΔG] set in step S2 is used as the reference for transmit gain comparison. K Any k-th transmit gain ΔG in ] k Does it exceed the upper limit of transmit gain ΔG? up If the value exceeds the limit, return to step S2 to reset the k-th transmit gain ΔG. k S4: Divide the first to the Mth transmitted signals into K sub-pulse signals, and the mth transmitted signal s m The K sub-pulse signals of (t) include the m-th transmitted signal s m The first sub-pulse signal of (t) to the mth transmitted signal s mThe Kth sub-pulse signal of (t); the kth sub-pulse signal of the first transmitted signal to the kth sub-pulse signal of the Mth transmitted signal correspond to the kth region of interest; initialize the set of pulse widths corresponding to the first sub-pulse signal to the Kth sub-pulse signal. The initial values ​​of the pulse widths of the k-th sub-pulse signals from the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal are all... Initialize the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal to obtain the initial set of carrier frequency differences. Let be the initial value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal. Step S5: Optimize the parameters of the first sub-pulse signal to the Kth sub-pulse signal; the process of optimizing the parameters of any kth sub-pulse signal includes steps S51 to S53; Step S51: Set the search step size of the pulse width of the kth sub-pulse signal to Δ T For any k-th sub-pulse signal, perform a certain number of iterations; in the i-th iteration, update the pulse width of the k-th sub-pulse signal for the k-th region of interest. and the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal. In the i-th iteration, based on the angle interval Θ of the k-th region of interest... k The array weighting vector [w] is formed by obtaining the array weighting coefficients of the k-th sub-pulse signal of the current first transmitted signal and the array weighting coefficients of the k-th sub-pulse signal in the M-th transmitted signal. 1,k ,w 2,k ,...,w M,k ] T Wherein, the array weighting coefficients of the k-th sub-pulse signal in the m-th transmitted signal. j is the imaginary unit; in the i-th iteration, the space-time coupling emission pattern P is obtained. k，i (θ,t), in, Let k be the delay time corresponding to the k-th sub-pulse signal in the i-th cycle. f0 = c / λ, where c represents the speed of light. For the m-th transmitted signal s in the i-th cycle m (t) is the carrier frequency of the k-th sub-pulse signal; l is an integer greater than or equal to and less than or equal to k-1, i is an integer greater than or equal to 1, t is the fast time, θ represents the azimuth angle, and Tp is the pulse width of each of the first to the M-th transmitted signals; Step S52: via Pk，i Integrating (θ, t) over a fast time interval yields the one-dimensional equivalent pattern g in the i-th cycle. k,i (θ), and obtain the k-th emission gain in the i-th loop corresponding to the k-th region of interest. Step S53: Determine With ΔG k Does the absolute value of the difference satisfy... If the condition is not met, continue the cycle for any k-th sub-pulse signal; if the condition is met, retain the current condition. and The parameter value, let This is the optimized value for the pulse width of the k-th sub-pulse signal; The optimized value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal; Step S6: According to and The system parameters and baseband signal are used to synthesize the transmit signals of each transmit array element and feed them to the radio frequency terminal; the expression for the m-th transmit signal of the m-th transmit array element is as follows: It is a baseband wave signal, where

[0006] Optional, G l It is numerically equal to the pattern gain of the coherent FDA radar under omnidirectional transmission conditions, i.e., taking The equivalent pattern gain when ΔG k When = 0, g(Θ) k ) = G l .

[0007] Optional, ΔG up The expression is: ΔG up =G u -G l =10log 10 MG l Among them, G u =10log 10 M, where G u =10log 10 M, G u It represents the maximum main lobe emission gain of a one-dimensional uniform linear array composed of M emission array elements in a phased array mode with the same array structure.

[0008] Optionally, in step S52,

[0009] Optional,

[0010] Compared with the prior art, the advantages of the present invention are as follows:

[0011] This invention enables the quantitative and differentiated design of transmit pattern gain for multiple discontinuous regions of interest within the observation space, enhancing the freedom of pattern design technology for coherent FDA radar. Simultaneously, this invention does not impose constraints on the baseband waveform of the coherent FDA radar, eliminating reliance on LFM waveforms for pattern design. Furthermore, based on coherent FDA radar, this technology, compared to traditional MIMO radar, does not rely on complex multi-dimensional encoded waveform optimization design, resulting in lower computational complexity. This invention can be widely applied to related applications of all-digital array radar, such as air search and space surveillance. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the coherent FDA radar upon which this invention is based;

[0014] Figure 2 This is a flowchart of the design of the quantitative emission pattern for the coherent FDA radar of this invention;

[0015] Figure 3 This is the design result of the transmission pattern of the coherent FDA radar (two-dimensional space-time coupled pattern) in the design example of this invention;

[0016] Figure 4 This is the design result of the emission pattern of the coherent FDA radar in the design example of this invention (one-dimensional equivalent emission pattern). Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0021] See Figure 1 As shown, the transmitting array of a coherent frequency diversity array (FDA) radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmitting array includes M spaced transmitting elements, with the spacing d between adjacent transmitting elements satisfying d = λ², where λ is the carrier wavelength of the transmitting array, and λ corresponds to the center frequency f0, f0 = c / λ, where c represents the speed of light. The M spaced transmitting elements include the first to the Mth transmitting elements arranged sequentially. M is an integer greater than or equal to 2.

[0022] When all transmitting elements are ideal omnidirectional elements, for a coherent frequency diversity array radar, the m-th transmitting element has the m-th transmitted signal s. m (t), s m The expression for (t) is:

[0023]

[0024] Where t represents fast time. The window function, w m f is the array weighting coefficient for the m-th transmitting element. m =f0+(m-1)Δf,f m Let f0 be the carrier frequency of the m-th transmitting element, and m be the center frequency, where m is an integer greater than or equal to 1 and less than or equal to M; there exists a frequency difference Δf between adjacent transmitting elements of the coherent FDA radar, and Δf << f0. This is a baseband signal, and the baseband signal is the same in the first to the Mth transmitted signals; T p The pulse widths of the first to the Mth transmitted signals are respectively.

[0025] Coherent FDA radar possesses intra-pulse beam scanning properties. The transmission pattern function of coherent FDA radar is a three-dimensionally coupled range-time-angle pattern, P(θ, t-τ). r ) is represented as: Where θ represents the azimuth angle, τ r Indicates the propagation delay. When τ r =0, w m When = 1, it can be further deduced that Where j is the imaginary unit.

[0026] To quantitatively evaluate the emission pattern of a coherent FDA radar, the expression for the one-dimensional equivalent emission pattern g(θ) of a coherent FDA radar is defined as follows: Where t is the fast time.

[0027] The emission pattern P(θ, t-τ) of the coherent FDA radar defined by the above equation r By using fast time integration, it is transformed into a one-dimensional function g(θ) that is only related to the angle θ, thus enabling quantitative numerical comparison.

[0028] like Figure 1 As shown, the carrier frequency difference Δf between adjacent transmitting elements enables the coherent FDA radar to have intra-pulse beam scanning characteristics. By utilizing this property and designing transmission parameters such as sub-pulse width and carrier frequency difference through the method of dividing sub-pulses, flexible control of the beam illumination space and illumination time can be achieved, thereby realizing the quantitative and differentiated design of transmission gain in different regions of interest.

[0029] See Figure 2 As shown in the embodiment, the quantitative transmission pattern design method for coherent FDA radar uses a one-dimensional uniform linear array arranged along the azimuth direction. The transmission array includes M intervald transmission elements, from the first to the Mth transmission elements arranged sequentially, where M is an integer greater than or equal to 2. The spacing d between adjacent transmission elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmission element. The mth transmission element transmits a signal s. m (t), m is an integer greater than or equal to 1 and less than or equal to M, there is a frequency difference Δf between the transmitted signals of adjacent transmitting array elements, Δf << f0, f0 is the center frequency, including the following steps.

[0030] Step S1: Set K regions of interest (ROIs) within the observation space. These K ROIs are designated as the first ROI to the Kth ROI, where K is an integer greater than or equal to 2. The set of angle intervals for the K ROIs is [Θ1, Θ2, ..., Θ]. K ], where the angle interval Θ of any k-th region of interestk =[θ k,start ,θ k,end ], And satisfy Where k is an integer greater than or equal to 1 and less than or equal to K. θ k，start and θ k，end Both represent the specific numerical value of the azimuth angle.

[0031] Step S2: Set the set of the first transmit gain of the first region of interest to the Kth transmit gain of the Kth region of interest as [ΔG1, ΔG2, ..., ΔG K ], where any k-th transmit gain ΔG k Defined as ΔG k =max(g(Θ) k ))-G l The unit is decibels.

[0032] Where max(g(Θ) k )) represents the maximum gain of the emission pattern in the k-th region of interest, G l As a benchmark for transmit gain comparison, G l Numerically, it is equal to the pattern gain of the coherent FDA radar under omnidirectional transmission, i.e., taking... The equivalent pattern gain at time ΔG k When = 0, g(Θ) k ) = G l g(θ) is the pattern function defined above, where θ k It represents an angle range.

[0033] Step S3: Determine the set [ΔG1, ΔG2, ..., ΔG] set in step S2. K Any k-th transmit gain ΔG in ] k Does it exceed the upper limit of transmit gain ΔG? up If any k-th transmit gain ΔG k Does it exceed the upper limit of transmit gain ΔG? up Then return to step S2 to reset the k-th transmit gain ΔG. k .

[0034] ΔG up The expression is: ΔG up =G u -G l =10log 10 MG l ; where G u =10log 10 M, G uIt represents the maximum main lobe transmission gain of a one-dimensional uniform linear array composed of M transmitting array elements in a phased array mode with the same array structure (no frequency shift between transmitting array elements).

[0035] Step S4: Divide the first to the Mth transmitted signals into K sub-pulse signals; the mth transmitted signal s m The K sub-pulse signals of (t) include the m-th transmitted signal s m The first sub-pulse signal of (t) to the mth transmitted signal s m The Kth sub-pulse signal of (t); the kth sub-pulse signal of the first transmitted signal to the kth sub-pulse signal of the Mth transmitted signal correspond to the kth region of interest; initialize the set of pulse widths corresponding to the first sub-pulse signal to the Kth sub-pulse signal. The initial values ​​for the pulse widths of the k-th sub-pulse signals from the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal are all set to... Initialize the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal, and obtain the set of initial values ​​of the carrier frequency difference of the corresponding first sub-pulse signal to the initial carrier frequency difference of the K-th sub-pulse signal. Let be the initial value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal.

[0036] Step S5: Optimize the parameters of the first sub-pulse signal to the Kth sub-pulse signal; the process of optimizing the parameters of any Kth sub-pulse signal includes steps S51 to S53.

[0037] Step S51: Set the search step size of the pulse width of the k-th sub-pulse signal to Δ. T For any k-th sub-pulse signal, perform a certain number of iterations; in the i-th iteration, update the pulse width of the k-th sub-pulse signal for the k-th region of interest. and the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal. In the i-th iteration, based on the angle interval Θ of the k-th region of interest... k The array weighting vector [w] is formed by obtaining the array weighting coefficients of the k-th sub-pulse signal of the current first transmitted signal and the array weighting coefficients of the k-th sub-pulse signal in the M-th transmitted signal. 1,k ,w 2,k ,...,w M,k ] TWherein, the array weighting coefficients of the k-th sub-pulse signal in the m-th transmitted signal. j is the imaginary unit; in the i-th iteration, the space-time coupling emission pattern P is obtained. k，i (θ,t), in, η k，i Let k be the delay time corresponding to the k-th sub-pulse signal in the i-th cycle. f0 = c / λ, where c represents the speed of light. For the m-th transmitted signal s in the i-th cycle m The carrier frequency of the kth sub-pulse signal in (t), l is an integer greater than or equal to and less than or equal to k-1, i is an integer greater than or equal to 1, t is the fast time, θ represents the azimuth angle, and Tp is the pulse width of each of the first to the Mth transmitted signals.

[0038] Step S52: via R k，i Integrating (θ, t) over a fast time interval yields the one-dimensional equivalent pattern g in the i-th cycle. k,i (θ), And obtain the k-th emission gain in the i-th loop corresponding to the k-th region of interest.

[0039] Step S53: Determine With ΔG k Does the absolute value of the difference satisfy... If the condition is not met, continue the cycle for any k-th sub-pulse signal; if the condition is met, retain the current condition. and The parameter value, let This is the optimized value for the pulse width of the k-th sub-pulse signal; It is the optimized value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal.

[0040] The parameters of the first sub-pulse signal are optimized, then the parameters of the second sub-pulse signal are optimized, and so on, until the parameters of the Kth sub-pulse signal are optimized. After optimizing the parameters of the first sub-pulse signal, the following is obtained: and After optimizing the parameters of the first sub-pulse signal, the following is obtained: and After optimizing the parameters of the Kth sub-pulse signal, we obtain and

[0041] Step S6, according to and The transmitted signals of each transmitting element are synthesized based on system parameters and baseband signals and fed to the radio frequency terminal. The expression for the m-th transmitted signal of the m-th transmitting element is as follows:

[0042]

[0043] It is a baseband wave signal, where Baseband signal It can be any waveform, where l is an integer greater than or equal to and less than or equal to k-1.

[0044] This method utilizes the intra-pulse beam scanning characteristics of coherent frequency diversity array radar. By dividing the signal into sub-pulses and optimizing the width of the sub-pulses and the carrier frequency difference between transmitting elements, it influences the angular velocity of the beam scanning, thereby adjusting the transmission pattern. This method is specifically designed for coherent frequency diversity array radar; therefore, the baseband waveforms of each transmitting channel... This is the main difference between this method and the traditional MIMO-based radar transmit pattern design.

[0045] This method not only allows for the design of the angular range of the region of interest in the transmission pattern, but also enables the quantitative and differentiated design of the transmission gain between different regions of interest. This is because the method sequentially optimizes the transmission parameters of each sub-pulse signal, thus allowing for the quantitative adjustment of the beam scanning speed and beam dwell time within each sub-pulse signal, without any interference between the sub-pulse signals.

[0046] The standard used by this method to quantitatively evaluate the transmit pattern gain is the one-dimensional equivalent transmit pattern function g(θ). By integrating the two-dimensional equivalent transmit pattern of the space-time coupled radar along fast time, the one-dimensional equivalent transmit pattern of the coherent FDA radar can be obtained for quantitative evaluation.

[0047] The invention will be further illustrated below through experimental simulation.

[0048] First, the system parameters and transmit pattern design specifications for the coherent frequency diversity array radar are set as shown in the table below:

[0049] Table 1 Simulation parameters for this example

[0050]

[0051]

[0052] As shown in Table 1, two regions of interest (ROIs) are set in this example. The first ROI has an angle interval Θ1 = [-15°, 15°], and the second ROI has an angle interval Θ2 = [40°, 60°]. To illustrate the quantitative and differentiated design capability of the proposed method for coherent FDA radar transmission patterns, the transmission gains [ΔG1, ΔG2] of the ROIs are set to [4dB, 6dB], [3dB, 7dB], [7dB, 3dB], and [5dB, 5dB], respectively.

[0053] Figure 3 The two-dimensional space-time coupling patterns are obtained by existing methods and by designing using the method of this invention, wherein... Figure 3 (a) shows the transmission pattern of the coherent FDA radar in uniform omnidirectional transmission mode. In this case, the transmission pattern is ideally omnidirectional, therefore the transmission gain G in this case is used. l As a benchmark for quantitatively evaluating pattern gain. Figure 3 (b) A two-dimensional emission pattern obtained by the existing coherent FDA radar emission pattern design method. This method can only design the angular range of the region of interest and cannot quantitatively design and adjust the emission gain value within the region of interest. Figure 3 (c) to Figure 3 (f) These are four sets of two-dimensional space-time coupled emission patterns obtained using the method proposed in this invention, where the maximum pattern gain [ΔG1, ΔG2] within the region of interest is set to [4dB, 6dB], [3dB, 7dB], [7dB, 3dB], and [5dB, 5dB], respectively. Figure 3 (c) to Figure 3 As can be seen in (f), when the transmit gain design parameters between two regions of interest change, the pulse width and beam scanning speed (the rate at which the main lobe of the beam changes with the horizontal axis) of the corresponding two sub-pulses change sequentially.

[0054] Will Figure 3 By integrating the two-dimensional emission pattern along the fast time path, we obtain... Figure 4 The coherent FDA radar equivalent one-dimensional radiation pattern shown can be used to effectively and quantitatively evaluate the implementation effect of the radiation pattern design. Figure 4 The coherent FDA radar of China and Israel emits uniform omnidirectional signals (e.g.) Figure 3 The pattern gain in case (a) is used as a comparison reference and is set to 0dB. Figure 4The other curves correspond to the design and implementation effects of the four sets of transmit gain indices in Table 1. The quantitative evaluation of the implementation results is as follows: When the transmit gain indices are ΔG1 = 4dB and ΔG2 = 6dB, the pattern gain implemented by this invention is ΔG′1 = 4.00dB and ΔG′2 = 5.99dB; when the transmit gain indices are ΔG1 = 3dB and ΔG2 = 7dB, the pattern gain implemented by this invention is ΔG′1 = 3.00dB and ΔG′2 = 6.99dB; when the transmit gain indices are ΔG1 = 7dB and ΔG2 = 3dB, the pattern gain implemented by this invention is ΔG1′ = 6.98dB and ΔG2′ = 2.97dB; when the transmit gain indices are ΔG1 = 5dB and ΔG2 = 5dB, the pattern gain implemented by this invention is ΔG1′ = 4.99dB and ΔG2′ = 5.00dB. The results above demonstrate that the quantitative coherent FDA radar transmit pattern design method proposed in this invention can effectively achieve quantitative and differentiated design of transmit gain over multiple discontinuous regions of interest. The design results achieved by this invention show minimal deviation from the design specifications. In contrast, existing methods lack the ability to quantitatively design transmit gain, and this method allows for arbitrary transmit baseband waveforms, providing greater design freedom.

[0055] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner may make various modifications or alterations within the scope of the appended claims, as long as they do not exceed the protection scope described in the claims of the present invention, they shall be within the protection scope of the present invention.

Claims

1. A quantitative transmission pattern design method for a coherent FDA radar, wherein the transmission array of the coherent FDA radar is a one-dimensional uniform linear array arranged along the azimuth direction, the transmission array comprising M intervald transmission elements, the M transmission elements comprising a first transmission element to the Mth transmission element arranged sequentially, where M is an integer greater than or equal to 2; the spacing d between adjacent transmission elements satisfies , Let be the carrier wavelength of the transmitting element; the m-th transmitting element has the m-th transmitted signal as . m is an integer greater than or equal to 1 and less than or equal to M, and there is a frequency difference between the transmitted signals of adjacent transmitting array elements. , , As the center frequency, it is characterized by, Includes the following steps: Step S1: Set K regions of interest (ROIs) within the observation space. These K ROIs are designated as the first ROI to the Kth ROI, where K is an integer greater than or equal to 2. The set of angle intervals for the K ROIs is... The angle interval of any k-th region of interest And satisfy k is an integer greater than or equal to 1 and less than or equal to K; Step S2: Set the set of the first transmit gain of the first region of interest to the Kth transmit gain of the Kth region of interest as follows: Any k-th transmit gain Defined as ; This represents the maximum gain of the transmission pattern within the k-th region of interest. Used as a benchmark for transmit gain comparison; Step S3: Determine the set set in step S2. Any k-th transmit gain Does it exceed the transmit gain limit? If the value exceeds the limit, return to step S2 to reset the k-th transmit gain. ; Step S4: Divide the first to the Mth transmitted signals into K sub-pulse signals, and the mth transmitted signal... The K sub-pulse signals include the m-th transmitted signal The first sub-pulse signal to the m-th transmitted signal The Kth sub-pulse signal; the kth sub-pulse signal of the first transmitted signal to the kth sub-pulse signal of the Mth transmitted signal correspond to the kth region of interest; initialize the set of pulse widths corresponding to the first sub-pulse signal to the Kth sub-pulse signal. The initial values ​​of the pulse widths of the k-th sub-pulse signals from the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal are all... , Tp represents the pulse width; Initialize the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal to obtain the initial set of carrier frequency differences. , Let be the initial value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal. ; Step S5: Optimize the parameters of the first sub-pulse signal to the Kth sub-pulse signal; the process of optimizing the parameters of any kth sub-pulse signal includes steps S51 to S53; Step S51: Set the search step size of the pulse width of the k-th sub-pulse signal to be... For any k-th sub-pulse signal, perform a certain number of iterations; in the i-th iteration, update the pulse width of the k-th sub-pulse signal for the k-th region of interest. and the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal. , , ; In the i-th iteration, based on the angle interval of the k-th region of interest The array weighting vector is formed by obtaining the array weighting coefficients of the k-th sub-pulse signal in the current first transmitted signal and the array weighting coefficients of the k-th sub-pulse signal in the M-th transmitted signal. Wherein, the array weighting coefficients of the k-th sub-pulse signal in the m-th transmitted signal. j is the imaginary unit; in the i-th iteration, the emission pattern of the space-time coupling is obtained. , ,in, , Let k be the delay time corresponding to the k-th sub-pulse signal in the i-th cycle. , , Represents the speed of light. For the m-th transmitted signal in the i-th cycle The carrier frequency of the k-th sub-pulse signal; l Let be an integer greater than or equal to and less than or equal to k-1, i be an integer greater than or equal to 1, and t be the fast time. Tp represents the azimuth angle, and Tp is the pulse width of each of the first to the Mth transmitted signals; Step S52: Through Integrating over a fast time interval yields the one-dimensional equivalent pattern in the i-th iteration. And obtain the k-th emission gain in the i-th loop corresponding to the k-th region of interest. ; Step S53: Determine and Does the absolute value of the difference satisfy... If the condition is not met, the loop continues for any k-th sub-pulse signal; if the condition is met, the current condition is retained. and The parameter value, let , ; This is the optimized value for the pulse width of the k-th sub-pulse signal; It is the optimized value of the carrier frequency difference between adjacent sub-pulse signals from the k-th sub-pulse signal of the first transmitted signal to the k-th sub-pulse signal of the M-th transmitted signal; Step S6: According to and The system synthesizes the transmission signals of each transmitting element based on the system parameters and the baseband signal, and feeds them to the radio frequency terminal; the expression for the m-th transmitting signal of the m-th transmitting element is as follows: , It is a baseband wave signal, where .

2. The quantitative emission pattern design method for coherent FDA radar according to claim 1, characterized in that, It is numerically equal to the pattern gain of the coherent FDA radar under omnidirectional transmission conditions, i.e., taking The equivalent pattern gain when hour, .

3. The quantitative emission pattern design method for coherent FDA radar according to claim 1, The expression is: ; in, G u It represents the maximum main lobe emission gain of a one-dimensional uniform linear array composed of M emission array elements in a phased array mode with the same array structure.

4. The quantitative emission pattern design method for coherent FDA radar according to claim 1, in step S52, .

5. The quantitative emission pattern design method for coherent FDA radar according to claim 1, .

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