A Spatial Multi-Scale Detection Method Based on Coherent Frequency Diversity Array Radar

Abstract

A spatial multi-scale detection method based on a coherent frequency diversity array radar, comprising: S1: Set K consecutive regions of interest in the observation space, respectively denoted as [Θ1, Θ2,..., Θ K , Θ k = [θ k,start , θ k,end , #imgabs0##imgabs1# S2: Set the first detection bandwidth to the Kth detection bandwidth, B k is the kth detection bandwidth configured on the angular interval of the kth region of interest; S3: Divide the first transmitted signal to the Mth transmitted signal into K sub-pulse signals respectively, the kth sub-pulse signal corresponds to the angular interval of the kth region of interest, and obtain the bandwidths [B′1, B′2,..., B′ K of each sub-pulse signal, then the pulse width of the kth sub-pulse signal #imgabs2# S4: Determine whether it satisfies #imgabs3# If it satisfies, go to step S5; if not, return to step S2 to re-design the first detection bandwidth to the Kth detection bandwidth; S5: Obtain the pulse widths [T p,1 , T p,2 ,..., T p,K of each sub-pulse signal, #imgabs4# S6: The expression of the mth transmitted signal s m (t) of the mth transmitting array element is: #imgabs5# S7: Feed the transmitted signals to the radio frequency end respectively and transmit them through the antennas of the transmitting array elements.

Description

Technical Field

[0001] The present invention relates to the technical field of array signal processing, and particularly relates to a spatial multi-scale detection method based on a coherent frequency diverse array radar. Background Art

[0002] A frequency diverse array (FDA) radar is a new type of digital array radar. By introducing a progressive carrier frequency increment between adjacent transmit channels, its transmit direction pattern is time-modulated. Specifically, the main lobe of the beam scans different angular directions within the pulse duration, forming a wide coverage within a certain range. The beam scanning characteristics of a coherent FDA radar make it suitable for observing large-scale airspaces, such as air surveillance and space monitoring. Existing research shows that in terms of achieving wide spatial coverage observation, a coherent FDA radar has a higher transmit dimension angular resolution compared to traditional digital array wide transmit and narrow receive radars. And compared to orthogonal multiple-input multiple-output (MIMO) radars, a coherent FDA radar does not rely on complex coded waveform optimization design, and the beam scanning range is more flexible and controllable.

[0003] The detection scale of a radar in a certain direction is determined by the bandwidth of the detection signal in that direction. In actual wide spatial coverage observation applications, the scattering characteristics of potential target of interest in different observation directions are significantly different. For example, in the low elevation angle observation domain, typical targets include unmanned aerial vehicles (UAVs), UAV swarms, and aerodynamic targets such as low-altitude penetration cruise missiles and aircraft; in the high elevation angle observation domain, typical targets include high-altitude and high-speed aircraft and low-earth orbit satellites, etc. In addition, relevant research shows that for different applications such as target imaging recognition and target detection and tracking, the optimal detection bandwidth is different. Traditional wide spatial coverage observation methods transmit a single bandwidth waveform to cover the entire airspace, and can only form a single spatial resolution scale in different observation directions, which has obvious deficiencies. In order to better extract target information, a radar system needs to have the ability to flexibly adjust the detection scale (i.e., the bandwidth of the detection signal) in different observation directions. Summary of the Invention

[0004] The purpose of the present invention is to provide a spatial multi-scale detection method based on a coherent frequency diverse array radar, which can form different spatial resolution scales in different observation directions while achieving wide spatial coverage, so as to solve the deficiencies of the existing technology.

[0005] To achieve the above object, the present invention provides a method for spatial multi-scale detection based on a coherent frequency diversity array radar. The transmitting array of the coherent frequency diversity array radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmitting array includes M spaced transmitting elements. The M spaced transmitting elements include the first transmitting element to the Mth transmitting element arranged in sequence. M is an integer greater than or equal to 2. The spacing d between adjacent transmitting elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmitting element. The mth transmitting element has the mth transmitting signal s m (t), where 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 transmitting signals of adjacent transmitting elements. Δf is much smaller than the center frequency f0, and it includes:

[0006] Step S1: Set K consecutive regions of interest in the observation space. The K consecutive regions of interest include the first region of interest to the Kth region of interest. K is an integer greater than or equal to 2. The set of angular intervals of the K regions of interest is [Θ1, Θ2,..., Θ K , where, for any kth region of interest, the angular interval and satisfies where k is an integer greater than or equal to 1 and less than or equal to K;

[0007] Step S2: Set the first detection bandwidth to the Kth detection bandwidth, denoted as [B1, B2,..., B K ; B k is the kth detection bandwidth configured for the angular interval of the kth region of interest;

[0008] Step S3: Divide the first transmitting signal to the Mth transmitting signal into K sub-pulse signals respectively. The K sub-pulse signals of the mth transmitting signal include the first sub-pulse signal of the mth transmitting signal to the Kth sub-pulse signal of the mth transmitting signal. The kth sub-pulse signal of the first transmitting signal to the kth sub-pulse signal of the Mth transmitting signal correspond to the angular interval of the kth region of interest. Obtain the bandwidths [B′1, B′2,..., B′ K of each sub-pulse signal required to achieve the detection bandwidths [B1, B2,..., B K , where B k ’ is the pulse width of each of the kth sub-pulse signal of the first transmitting signal to the kth sub-pulse signal of the Mth transmitting signal. The baseband waveform function of each sub-pulse signal is a linear frequency modulation waveform function. Then the expression for the pulse width B′ k of the kth sub-pulse signal is

[0009] Step S4: Determine whether it satisfies If it is satisfied, proceed to step S5; if not, return to step S2 to redesign the first detection bandwidth to the Kth detection bandwidth; where B t is the maximum transmission bandwidth of the coherent frequency diversity array radar;

[0010] Step S5: Obtain the pulse widths [T p,1 , T p,2 ,..., T p,K of each sub-pulse signal, where T p,k is the pulse width of the kth sub-pulse signal corresponding to the angular interval of the kth region of interest,

[0011] Step S6: Obtain the transmission signals [s1(t), s2(t),..., s M (t)] of each transmitting element. The expression of the mth transmission signal s m (t) of the mth transmitting element is: where η k is the delay time corresponding to the kth sub-pulse signal, i is an integer greater than or equal to 1 and less than or equal to k - 1; μ k is the chirp rate of the baseband waveform function of the kth sub-pulse signal, μ k = B′ k / T p,k , fm is the carrier frequency of the mth transmission signal, f m = f0 + (m - 1)Δf, f0 is the center frequency, f0 = c / λ, c represents the speed of light, t is the fast time variable, m is an integer greater than or equal to 1 and less than or equal to M, Tp is the pulse width of each of the first transmission signal to the Mth transmission signal, and j is the imaginary unit;

[0012] Step S7: Feed the transmission signals [s1(t), s2(t),..., s M (t)] to the RF end and transmit them through the antennas of the transmitting elements.

[0013] Optionally, the pulse widths of the first sub-pulse signal to the Kth sub-pulse signal are at least partially different.

[0014] Optionally, the baseband waveform functions transmitted within any one pulse duration of the first sub-pulse signal to the Kth pulse signal are the same.

[0015] Optionally,

[0016] Optionally, the pulse widths of the first sub-pulse signal to the Kth sub-pulse signal are at least partially different.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] This method is based on a coherent frequency diversity array radar, which realizes the transmission waveforms with different detection bandwidths configured in different detection directions in a wide spatial coverage detection mode, so as to form different spatial detection scales. While achieving wide spatial coverage, the present invention has the ability to transmit different detection waveforms in different detection directions, greatly expanding the design freedom of the array radar system, and can be widely applied to fields such as air search and space surveillance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a schematic diagram of the coherent frequency diversity array radar system based on the present invention.

[0021] Figure 2 It is a flowchart of the spatial multi-scale detection method based on the coherent frequency diversity array radar of the present invention.

[0022] Figure 3 It is the time-frequency diagram of the transmitted signal of the coherent frequency diversity array radar in the design example of the present invention;

[0023] Figure 4 It is the angle-angle ambiguity function diagram and range-angle ambiguity function diagram of the transmitted signal of the coherent frequency diversity array radar in the design example of the present invention;

[0024] Figure 5 It is a comparison diagram of one-dimensional profiles of the range-angle ambiguity function diagram of the transmitted signal of the coherent frequency diversity array radar in the design example of the present invention in different directions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The preferred embodiments of the present invention will be described in detail below 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 making a clearer and more definite definition of the protection scope of the present invention.

[0029] The coherent frequency diversity array radar based on the present invention is as Figure 1 shown. The transmitting array of the coherent frequency diversity array radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmitting array includes M spaced transmitting array elements. The M spaced transmitting array elements include the first transmitting array element to the Mth transmitting array element arranged in sequence. M is an integer greater than or equal to 2; the spacing d between adjacent transmitting array elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmitting array element.

[0030] When the transmitting array element is an ideal omnidirectional array element, the mth transmitting array element has the mth transmitting signal s m (t),

[0031]

[0032] where t represents the fast time variable, represents the window function, w m represents the array weighting coefficient of the mth transmitting array element, f m = f0 + (m - 1)Δf, fm is the carrier frequency of the mth transmitting signal of the mth transmitting array element, f0 is the center frequency, f0 = c / λ, c represents the speed of light, and 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 transmitting signals of adjacent transmitting array elements of the coherent frequency diversity array radar, and Δf << f0, is the baseband waveform function; Tp is the pulse width of each of the first transmitting signal to the Mth transmitting signal.

[0033] The coherent frequency diversity array radar has the property of in-pulse beam scanning. The transmitting pattern function of the coherent frequency diversity array radar is three-dimensional coupled in terms of range-time-angle. The transmitting pattern P(θ, t - τ r ) of the coherent frequency diversity array radar is expressed as (Equation 2):

[0034]

[0035] where θ represents the azimuth angle, τ r represents the propagation delay, and j is the imaginary unit.

[0036] From the above (Equation 2), it can be obtained that the pointing of the main lobe of the beam of the coherent frequency diversity array radar has time-varying characteristics, which can be specifically expressed as:

[0037] where the value range of k is any integer, t represents the fast time variable, τ r represents the propagation delay, and θ represents the azimuth angle.

[0038] From (Equation 3), the beam scanning angular velocity of the coherent frequency diversity array radar is obtained, where ω θ represents the beam scanning angular velocity of the coherent frequency diversity array radar, d represents the spacing between adjacent transmitting array elements, and Δf is the frequency difference between adjacent transmitting array elements of the coherent frequency diversity array radar.

[0039] The dwell time of the beam of the coherent frequency diversity array radar in a certain angular interval θ width is The beam scanning characteristic of the coherent frequency diversity array radar results in a reduction in its beam dwell time. When transmitting a frequency-modulated waveform, the actual detection bandwidth of the coherent frequency diversity array radar in a certain angular direction is less than the bandwidth of the transmitted signal. Therefore, it is necessary to design the transmitted signal bandwidth of the coherent frequency diversity array radar according to the actual required detection bandwidth. Among them, T s is the dwell time, ω θ represents the beam scanning angular velocity of the coherent frequency diversity array radar, λ is the carrier wavelength, Δf is the frequency difference between the transmitted signals of adjacent transmitting array elements of the frequency diversity array radar, and M is the number of spaced transmitting array elements.

[0040] Utilizing the beam scanning characteristic of the coherent frequency diversity array radar, the ability to form different detection scales in different observation directions can be achieved by dividing sub-pulse signals and separately designing the bandwidth of the transmitted waveform within the sub-pulse signals.

[0041] Refer to Figure 2As shown in the figure, the present invention proposes a method for spatial multi-scale detection based on a coherent frequency diverse array (FDA) radar. The transmitting array of the coherent frequency diverse array radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmitting array includes M spaced transmitting elements. The M spaced transmitting elements include the first transmitting element to the Mth transmitting element arranged in sequence. M is an integer greater than or equal to 2. The spacing d between adjacent transmitting elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmitting element. The mth transmitting element has the mth transmitting signal s m (t), where 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 transmitting signals of adjacent transmitting elements. Δf is much smaller than the center frequency f0. The method includes the following steps:

[0042] Step S1: Set K consecutive regions of interest in the observation space. The K consecutive regions of interest include the first region of interest to the Kth region of interest. K is an integer greater than or equal to 2. The set of angular intervals of the K regions of interest is [Θ1, Θ2,..., Θ K , where the angular interval of any kth region of interest and satisfies k is an integer greater than or equal to 1 and less than or equal to K.

[0043] Step S2: Set the first detection bandwidth to the Kth detection bandwidth, denoted as [B1, B2,..., B K ; B k is the kth detection bandwidth configured on the angular interval of the kth region of interest.

[0044] In one embodiment, the first detection bandwidth to the Kth detection bandwidth are at least partially different. It is also possible to set the first detection bandwidth to the Kth detection bandwidth to be all different.

[0045] Set the values of the first detection bandwidth to the Kth detection bandwidth according to actual observation requirements.

[0046] Step S3: Divide the first transmitting signal to the Mth transmitting signal into K sub-pulse signals respectively. The K sub-pulse signals of the mth transmitting signal include the first sub-pulse signal to the Kth sub-pulse signal of the mth transmitting signal. The kth sub-pulse signal of the first transmitting signal to the kth sub-pulse signal of the Mth transmitting signal correspond to the angular interval of the kth region of interest. Obtain the bandwidths [B′1, B′2,..., B′ K of the respective sub-pulse signals required to achieve any detection bandwidth [B1, B2,..., B K , where B k ’ is the pulse width of the kth sub-pulse signal of the first transmitting signal to the kth sub-pulse signal of the Mth transmitting signal respectively.

[0047] In one embodiment, the baseband waveform function of each sub-pulse signal is a chirp waveform function, and the pulse width B' of the k-th sub-pulse signal k is expressed as

[0048] The pulse widths of the first sub-pulse signal to the K-th sub-pulse signal are at least partially different. In one embodiment, the pulse widths of the first sub-pulse signal to the K-th sub-pulse signal are all different from each other.

[0049] The baseband waveform functions emitted by the first sub-pulse signal to the K-th pulse signal within any one pulse duration are the same.

[0050] The baseband waveform functions emitted by the first sub-pulse signal to the K-th pulse signal within different pulse durations are different or the same.

[0051] Step S4: Determine whether the following condition is satisfied If it is satisfied, go to step S5; if not, return to step S2 to re-design the first detection bandwidth to the K-th detection bandwidth; where B t is the maximum transmission bandwidth of the coherent frequency diversity array radar.

[0052] Step S5: Obtain the pulse widths [T p,1 , T p,2 ,..., T p,K of each sub-pulse signal, where T p,k is the pulse width of the k-th sub-pulse signal corresponding to the angular interval of the k-th region of interest

[0053] Step S6: Obtain the transmission signals [s1(t), s2(t),..., s M (t)] of each transmitting element. The expression of the m-th transmission signal s m (t) of the m-th transmitting element is:[[]]

[0054] where η k is the delay time corresponding to the k-th sub-pulse signal i is an integer greater than or equal to 1 and less than or equal to k - 1; μ k is the chirp rate of the baseband waveform function of the k-th sub-pulse signal, μ k = B' k / T p,k , fm is the carrier frequency of the m-th transmission signal, f m= f0 + (m - 1)Δf, where f0 is the center frequency, f0 = c / λ, c represents the speed of light, t is the fast time variable, m is an integer greater than or equal to 1 and less than or equal to M, Tp is the pulse width of each of the first transmitted signal to the Mth transmitted signal, and j is the imaginary unit.

[0055] Step S7: Feed the transmitted signals [s1(t), s2(t),..., s M (t)] to the RF end respectively and transmit them through the antennas of the transmitting array elements.

[0056] Design a space-time matched filter h(θ′, t) at the receiving end for matched reception. The expression of the space-time matched filter h(θ′, t) is

[0057]

[0058] To better visually explain the design example of the present invention, the multi-dimensional ambiguity function of the array signal composed of the first transmitted signal to the Mth transmitted signal is introduced here. The definition of the multi-dimensional ambiguity function is shown as follows:

[0059]

[0060] where s m (t) is the transmitted signal of the mth transmitting array element, s n (t) is the transmitted signal of the nth transmitting array element, s n * (t - τ) is the conjugate of s n (t) after a delay time of τ; both n and m are integers greater than or equal to 1 and less than or equal to M; θ represents the azimuth angle of the target, θ′ is the digital beamforming angle, τ is the range delay time, j is the imaginary unit, t represents the fast time variable, and f d is the Doppler frequency.

[0061] The first half of the definition formula of the multi-dimensional ambiguity function evaluates the spatial domain energy focusing performance of the coherent frequency diversity array radar. The second half of the multi-dimensional ambiguity function is similar to the traditional ambiguity function and evaluates the autocorrelation performance and Doppler tolerance of the transmitted waveform. The multi-dimensional ambiguity function is equivalent to performing equivalent transmit beamforming and time-domain matched filtering on the echo signal of the multiple-input single-output mode array radar. The three reduced-dimensional expressions of the multi-dimensional ambiguity function can be used to visually quantitatively and qualitatively evaluate the range resolution, Doppler tolerance, and spatial domain energy focusing performance of the array radar signal, which are respectively: (1) Range-Doppler ambiguity function χ(τ, f d ; θ = θ′), which can be used to analyze the autocorrelation performance and Doppler tolerance of the waveform; (2) Angle-Angle ambiguity function χ(θ, θ′; τ = 0, f d= 0) represents the influence of different azimuth angles θ and digital beamforming angles θ′ of the target on the reception gain under the condition of τ = 0, f d = 0, which is used to evaluate the spatial coverage ability of the waveform; (3) The range-angle ambiguity function χ(τ, θ; θ′ = θ0, f d = 0) represents the focusing performance of the array radar system on targets at different azimuth positions θ when the digital beamforming angle θ′ = θ0 under the zero Doppler condition. The present invention will be further described below through a set of design examples.

[0062] First, assume that the system parameters of the coherent FDA radar and the design indexes of spatial multi-scale detection are as shown in the following table:

[0063] Table 1 Simulation parameters of this example

[0064]

[0065]

[0066] Refer to Figure 3 The time-frequency diagram of the transmitted signal of the coherent frequency diversity array radar in the design example of the present invention is shown. As shown in the figure, the transmitted signal of each transmitting array element is divided into three sub-pulse signals, and the three sub-pulse signals respectively correspond to the angular regions of three regions of interest. The transmitted signal is divided into three sub-pulses, corresponding to three consecutive angular intervals, Θ1 = [-90°, -30°], Θ2 = [-30°, 30°], Θ3 = [30°, 90°]. After calculation, the pulse widths of the sub-pulse signals are T p,1 = 2.5 μs, T p,2 = 5 μs, T p,3 = 2.5 μs. The detection bandwidths quantitatively designed on the three different angular intervals are B1 = 15 MHz, B2 = 30 MHz, B3 = 20 MHz. According to the system parameters of the coherent frequency diversity array radar in Table 1, it can be calculated that the transmitted signal bandwidths within each sub-pulse signal should be B′1 = 71.25 MHz, B′2 = 285 MHz, B′3 = 95 MHz. Holds and meets the system design requirements.

[0067] To further evaluate and demonstrate the design example of the present invention, the angle-angle ambiguity function χ(θ, θ′; τ = 0, f d = 0) and the range-angle ambiguity function χ(τ, θ; θ′ = θ0, f d = 0) are introduced for analysis and explanation. As Figure 4 (a) shows the angle-angle ambiguity function χ(θ, θ′; τ = 0, f of the FDA transmitted signal designed in this example d= 0), where the horizontal axis is sinθ corresponding to the target azimuth angle represented by sine, and the vertical axis is sinθ′ corresponding to the digital beamforming angle represented by sine. It can be seen from the figure that when sinθ = sinθ′, that is, on the secondary diagonal, the ambiguity function forms a high gain, which indicates that the coherent FDA radar in this design example has the ability of omnidirectional wide-coverage detection. As Figure 4 (b)ˉ(d) show the corresponding range-angle ambiguity functions χ(τ, θ; θ′ = θ0, f d = 0), where the horizontal axis represents the azimuth angle θ and the vertical axis represents the range delay time τ. From Figure 4 (b)ˉ(d), it can be seen that when the digital beamforming angle θ′ is set in different angle intervals Θ1:Θ3, there are differences in the main lobe width in the range dimension, indicating that the spatial resolution scales formed at different azimuth positions are different in this design example.

[0068] In order to further quantitatively evaluate the design example of the present invention, Figure 5 respectively take Figure 4 the one-dimensional profiles at the positions of θ = -40°, θ = 0° and θ = 40° in (b)ˉ(d) for comparison and explanation. As Figure 5 shown, the solid line is the one-dimensional range image of the detection waveform when θ = -40° (located in the angle interval Θ1), the designed detection bandwidth is B1 = 15 MHz, the theoretical resolution is 10 m, and as shown, its actual range resolution is 9 m, and the peak sidelobe ratio is -34.10 dB; the short dashed line is the one-dimensional range image of the detection waveform when θ = 0° (located in the angle interval Θ2), the designed detection bandwidth is B2 = 30 MHz, the theoretical resolution is 5 m, and as shown, its actual range resolution is 4.5 m, and the peak sidelobe ratio is -45.56 dB; the dotted line is the one-dimensional range image of the detection waveform when θ = 40° (located in the angle interval Θ3), the designed detection bandwidth is B3 = 20 MHz, the theoretical resolution is 7.5 m, and as shown, its actual range resolution is 6.6 m, and the peak sidelobe ratio is -33.82 dB. The above experimental results show that the actual effect of the method proposed by the present invention reaches the theoretical design index, and the actual resolution is slightly better than the theoretical resolution.

[0069] In summary, the coherent FDA radar spatial multi-scale detection method proposed by the present invention can, while achieving wide-coverage spatial detection, form different spatial resolution scales in different observation directions. This method can effectively improve the detection performance of the radar in the wide-coverage spatial detection mode and can be widely applied to application fields such as air warning search and space surveillance.

[0070] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner may make various deformations or modifications within the scope of the appended claims. As long as it does not exceed the protection scope described in the claims of the present invention, it shall be within the protection scope of the present invention.

Claims

1. A spatial multi-scale detection method based on a coherent frequency diversity array radar. The transmitting array of the coherent frequency diversity array radar is a one-dimensional uniform linear array arranged along the azimuth direction. The transmitting array includes M spaced transmitting array elements. The M spaced transmitting array elements include the first transmitting array element to the Mth transmitting array element arranged in sequence. M is an integer greater than or equal to 2. The spacing d between adjacent transmitting array elements satisfies d = λ / 2, where λ is the carrier wavelength of the transmitting array element. The mth transmitting array element has the mth transmitting signal s m (t), where 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 transmitting signals of adjacent transmitting array elements. Δf is much smaller than the center frequency f0. It is characterized in that Step S1: Set K consecutive regions of interest in the observation space. The K consecutive regions of interest include the first region of interest to the Kth region of interest. K is an integer greater than or equal to 2. The set of angular intervals of the K regions of interest is [Θ1, Θ2,..., Θ K , where the angular interval Θ k of any kth region of interest is 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 first detection bandwidth to the Kth detection bandwidth, denoted as [B1, B2,..., B K ; B k is the kth detection bandwidth configured for the angular interval of the kth region of interest; Step S3: Divide each of the first transmission signal to the Mth transmission signal into K sub-pulse signals. The K sub-pulse signals of the mth transmission signal include the first sub-pulse signal of the mth transmission signal to the Kth sub-pulse signal of the mth transmission signal. The kth sub-pulse signal of the first transmission signal to the kth sub-pulse signal of the Mth transmission signal correspond to the angular interval of the kth region of interest. Obtain the bandwidths [B′1, B′2,..., B′ K required for any realization of the detection bandwidth [B1, B2,..., B K , where B k ’ is the pulse width of each of the kth sub-pulse signal of the first transmission signal to the kth sub-pulse signal of the Mth transmission signal. The baseband waveform function of each sub-pulse signal is a chirp waveform function. Then the expression for the pulse width B′ k of the kth sub-pulse signal is Step S4: Determine whether the following condition is satisfied If the condition is satisfied, proceed to step S5; if not, return to step S2 to redesign the first detection bandwidth to the Kth detection bandwidth. Here, B t is the maximum transmit bandwidth of the coherent frequency diversity array radar; Step S5: Obtain the pulse widths [T p,1 , T p,2 ,..., T p,K , where T p,k is the pulse width of the k-th sub-pulse signal corresponding to the angular interval of the k-th region of interest, Step S6: Obtain the transmission signals [s1(t), s2(t),..., s M (t)] of each transmitting array element. The expression of the m-th transmission signal s m (t) of the m-th transmitting array element is: where η k is the delay time corresponding to the k-th sub-pulse signal, i is an integer greater than or equal to 1 and less than or equal to k - 1; μ k is the chirp rate of the baseband waveform function of the k-th sub-pulse signal, μ k = B′ k / T p,k , fm is the carrier frequency of the m-th transmission signal, f m = f0 + (m - 1)Δf, f0 is the center frequency, f0 = c / λ, c represents the speed of light, t is the fast time variable, Tp is the pulse width of each of the first transmission signal to the M-th transmission signal, and j is the imaginary unit; Step S7: Feed the transmitted signals [s1(t), s2(t),..., s M (t)] to the radio frequency end respectively and transmit them through the antennas of the transmitting array elements.

2. The spatial multi-scale detection method based on a coherent frequency diversity array radar according to claim 1, wherein The pulse widths of the first sub-pulse signal to the Kth sub-pulse signal are at least partially different.

3. The method for spatial multi-scale detection based on a coherent frequency diversity array radar according to claim 1, wherein The baseband waveform functions emitted by the first sub-pulse signal to the Kth pulse signal within any pulse duration are the same.

4. The method for spatial multi-scale detection based on a coherent frequency diversity array radar according to claim 1, wherein 5. The space multi-scale detection method based on a coherent frequency diversity array radar according to claim 1, wherein The pulse widths of the first sub-pulse signal to the Kth sub-pulse signal are at least partially different.

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