Range fuzzy clutter suppression processing method and system for space-based early warning radar

Abstract

The present invention provides a method and system for range ambiguity clutter suppression in a space-based early warning radar. The method comprises acquiring multi-channel baseband echo data in elevation and azimuth, performing range and azimuth pulse compression processing, and converting the data into the post-Doppler domain. The method further comprises calculating the lower viewing angle corresponding to different range ambiguity components of each range unit, calculating the true Doppler frequency based on system prior information and the baseband Doppler frequency, and calculating the azimuth angle values ​​corresponding to each range ambiguity component at different Doppler frequencies. The method further comprises traversing different azimuth sub-channels, constructing an orthogonal projection weighted vector in conjunction with the elevation multi-channel, performing range ambiguity clutter suppression, and extracting range-ambiguity-free clutter. The method further comprises performing Doppler center correction processing, combining the azimuth multi-channel with space-time adaptive processing technology to perform clutter suppression, and obtaining a residual image after range ambiguity clutter suppression. The method implements range ambiguity clutter suppression in a practical space-based early warning radar system that takes into account antenna installation tilt and yaw angles.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a method and system for suppressing range fuzzy clutter in a space-based early warning radar based on orthogonal projection. Background Art

[0002] Because their detection range is much greater than that of airborne early warning radar systems, clutter echo signals received by space-based early warning radar systems often exhibit severe range ambiguity. Furthermore, the influence of the Earth's rotation effectively introduces yaw angle into the system, causing clutter to become range-dependent. When range ambiguity and clutter range dependence coexist, the space-time spectra of clutter with different range ambiguities no longer reside in the same location, significantly broadening the clutter main lobe. This severely impacts the performance of traditional space-time adaptive processing (STAP) clutter suppression and target detection.

[0003] Based on the elevation-azimuth multi-channel radar system, researchers at home and abroad have proposed numerous range-ambiguity clutter suppression algorithms. 3D-STAP processing technology effectively suppresses range-ambiguity clutter by combining elevation, azimuth, and time for adaptive processing. However, this method requires a large number of training samples and has high computational complexity, making it difficult to meet real-time processing requirements. Furthermore, waveform diversity techniques can effectively separate range-ambiguity clutter components by modulating the transmitted waveform. Examples include frequency diversity array (FDA), element-pulse coding (EPC), and azimuth phase coding (APC). However, due to the non-ideal orthogonality of the transmitted waveform, these algorithms suffer from cross-correlation interference after waveform separation, which can affect subsequent clutter suppression performance. Furthermore, these methods typically do not consider the actual radar system's antenna installation angle when performing range-ambiguity suppression. Summary of the Invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide a method and system for suppressing range ambiguity clutter in a space-based early warning radar.

[0005] A method for suppressing range ambiguity clutter in a space-based early warning radar according to the present invention includes:

[0006] Signal conversion step: Acquire the elevation and azimuth multi-channel baseband echo data of the space-based early warning radar, perform range and azimuth pulse compression processing, convert the multi-channel echo signal to the post-Doppler domain, and obtain the post-Doppler domain elevation and azimuth multi-channel baseband echo data;

[0007] Azimuth angle calculation steps: The post-Doppler domain elevation and azimuth multi-channel baseband echo data is sequentially traversed through all range cells, and the corresponding downward viewing angle corresponding to the different range ambiguity components of each range cell is calculated. The true Doppler frequency is calculated based on the radar system prior information and the baseband Doppler frequency. The azimuth angle values ​​of each range ambiguity component corresponding to different Doppler frequencies are then calculated in sequence.

[0008] Range-free clutter extraction steps: traverse different azimuth sub-channels, combine the pitch multi-channels to construct an orthogonal projection weighted vector, perform range-free clutter suppression, and extract range-free clutter;

[0009] Range ambiguity clutter suppression processing steps: Doppler center correction processing is performed on the clutter without range ambiguity, and then clutter suppression processing is performed based on the space-time adaptive processing technology of the azimuth multi-channel to obtain the residual image after range ambiguity clutter suppression processing.

[0010] Preferably, the calculation expression of the post-Doppler domain pitch-azimuth multi-channel baseband echo data is:

[0011]

[0012] Where sinc(·) is the Sigmoid function, represents the post-Doppler domain echo signal of the space-based early warning radar of the i-th elevation sub-channel and the j-th azimuth sub-channel, N r and N a are the number of elevation sub-channels and azimuth sub-channels of the radar system, d i and d j Represents the radar antenna pitch sub-channel arrangement and radar antenna azimuth sub-channel arrangement of the i-th pitch sub-channel and the j-th azimuth sub-channel, respectively. and d r and d a is the physical spacing of the radar antenna elevation sub-channel and the physical spacing of the azimuth sub-channel, and R 0,p They represent the amplitude term of the p-th range ambiguity clutter signal at the i-th pitch sub-channel, the j-th azimuth sub-channel, and the initial slant range of the p-th range ambiguity clutter component, θ el,amb,p and θ azi,p It represents the lower viewing angle and azimuth of the pth range fuzzy clutter component, t is the range fast time variable, f a is the Doppler frequency variable, B represents the system bandwidth, θ inc is the radar antenna installation inclination angle, λ is the wavelength, T a is the accumulation time, v represents the platform running speed, ρ crb Indicates the system yaw amplitude, is the system yaw angle.

[0013] Preferably, the azimuth angle calculation expressions of different distance blur components are:

[0014]

[0015] Where θ el,amb,p represents the lower viewing angle corresponding to the p-th range blurred clutter component, and acos(·) represents the inverse cosine trigonometric function.

[0016] Preferably, the step of extracting clutter without range ambiguity includes: calculating the elevation multi-channel steering vector, the range ambiguity orthogonal projection matrix, and the orthogonal projection weighting vector of different range ambiguity clutter components in sequence according to the downward viewing angle and azimuth angle corresponding to the different range ambiguity clutter components, and then performing weighted processing on the elevation and azimuth multi-channel baseband echo data vector in the post-Doppler domain.

[0017] Preferably, the pitch multi-channel steering vector calculation expression of the fuzzy clutter components at different distances is:

[0018]

[0019] Where a amb,p is the pitch multi-channel steering vector of the p-th range ambiguity clutter component;

[0020] The distance fuzzy orthogonal projection matrix calculation expression is:

[0021]

[0022] Where A r,p,amb is the orthogonal projection matrix of the p-th distance blur component;

[0023] The orthogonal projection weighted vector calculation expression is:

[0024] ω amb,0 =A r,1,amb A r,2,amb …A r,p,amb a amb,0

[0025] Where, ω amb,0 To extract the zeroth-order range fuzzy clutter component, that is, the orthogonal projection weight vector of the unfuzzy range clutter component, I is the unit matrix;

[0026] The pitch multi-channel signal vector calculation expression is:

[0027]

[0028] Where, represents the pitch multi-channel signal vector constructed by the echo signal at the j-th azimuth sub-channel, Represents the post-Doppler domain elevation and azimuth multi-channel baseband echo data at the i-th elevation sub-channel and the j-th azimuth sub-channel.

[0029] According to the present invention, a space-based early warning radar range ambiguity clutter suppression processing system includes:

[0030] Signal conversion module: obtains the multi-channel baseband echo data of the space-based early warning radar in elevation and azimuth, performs range and azimuth pulse compression processing, converts the multi-channel echo signal into the post-Doppler domain, and obtains the multi-channel baseband echo data in the post-Doppler domain in elevation and azimuth;

[0031] Azimuth calculation module: This module sequentially traverses all range cells for the post-Doppler domain elevation and azimuth multi-channel baseband echo data, calculates the downward viewing angle corresponding to the different range ambiguity components of each range cell, calculates the true Doppler frequency based on the radar system prior information and the baseband Doppler frequency, and then sequentially calculates the azimuth angle values ​​of each range ambiguity component corresponding to different Doppler frequencies;

[0032] Range-free clutter extraction module: traverses different azimuth sub-channels, combines the pitch multi-channels to construct an orthogonal projection weighted vector, performs range-free clutter suppression, and extracts range-free clutter.

[0033] Range ambiguity clutter suppression processing module: Performs Doppler center correction processing on clutter without range ambiguity, and then combines azimuth multi-channel clutter suppression processing based on space-time adaptive processing technology to obtain the residual image after range ambiguity clutter suppression processing.

[0034] Preferably, the calculation expression of the post-Doppler domain pitch-azimuth multi-channel baseband echo data is:

[0035]

[0036] Where sinc(·) is the Sigmoid function, represents the post-Doppler domain echo signal of the space-based early warning radar of the i-th elevation sub-channel and the j-th azimuth sub-channel, N r and N a are the number of elevation sub-channels and azimuth sub-channels of the radar system, d i and d j Represents the radar antenna pitch sub-channel arrangement and radar antenna azimuth sub-channel arrangement of the i-th pitch sub-channel and the j-th azimuth sub-channel, respectively. and d r and d a is the physical spacing of the radar antenna elevation sub-channel and the physical spacing of the azimuth sub-channel, and R 0,pThey represent the amplitude term of the p-th range ambiguity clutter signal at the i-th pitch sub-channel, the j-th azimuth sub-channel, and the initial slant range of the p-th range ambiguity clutter component, θ el,amb,p and θ azi,p It represents the lower viewing angle and azimuth of the pth range fuzzy clutter component, t is the range fast time variable, f a is the Doppler frequency variable, B represents the system bandwidth, θ inc is the radar antenna installation inclination angle, λ is the wavelength, T a is the accumulation time, v represents the platform running speed, ρ crb Indicates the system yaw amplitude, is the system yaw angle.

[0037] Preferably, the azimuth angle calculation expressions of different distance blur components are:

[0038]

[0039] Where θ el,amb,p represents the lower viewing angle corresponding to the p-th range blurred clutter component, and acos(·) represents the inverse cosine trigonometric function.

[0040] Preferably, the range-ambiguity-free clutter extraction module includes: sequentially calculating the elevation multi-channel steering vector, the range ambiguity orthogonal projection matrix, and the orthogonal projection weighting vector of different range-ambiguity clutter components according to the downward viewing angles and azimuth angles corresponding to the different range-ambiguity clutter components, and then performing weighted processing on the post-Doppler domain elevation-azimuth multi-channel baseband echo data vector.

[0041] Preferably, the pitch multi-channel steering vector calculation expression of the fuzzy clutter components at different distances is:

[0042]

[0043] Where a amb,p is the pitch multi-channel steering vector of the p-th range ambiguity clutter component;

[0044] The distance fuzzy orthogonal projection matrix calculation expression is:

[0045]

[0046] Where A r,p,amb is the orthogonal projection matrix of the p-th distance blur component;

[0047] The orthogonal projection weighted vector calculation expression is:

[0048] ω amb,0 =A r,1,amb A r,2,amb …A r,p,amba amb,0

[0049] Where, ω amb,0 To extract the zeroth-order range fuzzy clutter component, that is, the orthogonal projection weight vector of the unfuzzy range clutter component, I is the unit matrix;

[0050] The pitch multi-channel signal vector calculation expression is:

[0051]

[0052] Where s ramb,j represents the pitch multi-channel signal vector constructed by the echo signal at the j-th azimuth sub-channel, Represents the post-Doppler domain elevation and azimuth multi-channel baseband echo data at the i-th elevation sub-channel and the j-th azimuth sub-channel.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] This invention constructs a radar observation model based on the actual radar system antenna installation tilt angle and utilizes subspace orthogonal projection weight vectors to achieve range ambiguity suppression. This overcomes the high computational complexity and inconvenience of existing range ambiguity suppression techniques in practical engineering applications. Following this range ambiguity suppression, a cascaded multi-channel space-time adaptive processing technique is then employed to effectively suppress range ambiguity clutter in a space-based, multi-channel early warning radar system in both elevation and azimuth. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0056] Figure 1 This is a flow chart of a method for processing range ambiguity clutter suppression for an elevation-azimuth multi-channel space-based early warning radar provided in an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram before range blur suppression processing;

[0058] Figure 3 This is a schematic diagram after range ambiguity suppression processing;

[0059] Figure 4 This is a schematic diagram of the Doppler center correction result;

[0060] Figure 5 This is the residual image of STAP processing and the enlarged image of the target focusing result;

[0061] Figure 6 The figure is compared with the results of STAP processing without range ambiguity suppression. DETAILED DESCRIPTION

[0062] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0063] Example 1

[0064] This embodiment provides a method for suppressing range ambiguity clutter in a space-based early warning radar based on orthogonal projection, comprising the following steps:

[0065] 1) Acquire multi-channel baseband echo data in pitch and azimuth for space-based early warning, perform range and azimuth pulse compression processing, and convert the multi-channel echo signal into the post-Doppler domain;

[0066] 2) Using the post-Doppler domain multi-channel echo data, sequentially traverse all range bins and calculate the corresponding down-angle view for each range ambiguity component. Calculate the true Doppler frequency based on system prior information and the baseband Doppler frequency, and then sequentially calculate the azimuth angle value of each range ambiguity component corresponding to each Doppler frequency.

[0067] 3) Traversing different azimuth sub-channels, constructing an orthogonal projection weighted vector based on the viewing angle and azimuth angle combined with the elevation multi-channel under the different range ambiguity components, performing range ambiguity clutter suppression, and extracting range-free clutter;

[0068] 4) Performing Doppler center correction processing, and then performing the unambiguous clutter suppression processing based on the space-time adaptive processing technology in conjunction with the azimuth multi-channel to obtain the final residual image after the range ambiguity clutter suppression processing.

[0069] The calculation expression of the post-Doppler domain radar echo signal in step 1) is:

[0070]

[0071] Where sinc(·) is the Sigmoid function, Indicates the i-th (i=1,2,…N r ) pitch sub-channel, j (j=1,2,…N a ) azimuth sub-channel space-based early warning radar post-Doppler domain echo signal, N r and N a The number of elevation sub-channels and azimuth sub-channels of the radar system respectively. i and d jRepresents the radar antenna pitch sub-channel arrangement and radar antenna azimuth sub-channel arrangement of the i-th pitch sub-channel and the j-th azimuth sub-channel, respectively. and d r and d a It is the physical spacing of radar antenna elevation sub-channel and azimuth sub-channel. and R 0,p θ represents the amplitude term of the p-th (p=0, 1, ... P-1) range ambiguity clutter signal at the i-th pitch sub-channel and the j-th azimuth sub-channel, and the initial slant range of the p-th range ambiguity clutter component. el,amb,p and θ azi,p It represents the lower viewing angle and azimuth of the pth range fuzzy clutter component. t is the range fast time variable, f a is the Doppler frequency variable, and B is the system bandwidth. inc is the radar antenna installation inclination angle, λ is the wavelength, T a is the accumulation time, v represents the platform running speed, ρ crb Indicates the system yaw amplitude, is the system yaw angle.

[0072] The azimuth calculation expressions of the different distance blur components in step 2) are:

[0073]

[0074] Where θ el,amb,p represents the lower viewing angle corresponding to the p-th (p=0, 1, ... P-1)th range fuzzy clutter component. acos(·) represents the inverse cosine trigonometric function.

[0075] The acquisition of the orthogonal projection weighted vector in step 3) specifically includes:

[0076] At each azimuth sub-channel, the pitch multi-channel steering vector, range ambiguity matrix and orthogonal projection weighted vector of different range fuzzy clutter components are calculated in sequence;

[0077] The pitch multi-channel steering vectors of the fuzzy clutter components at different distances are:

[0078]

[0079] Where a amb,p is the pitch multi-channel steering vector of the p-th (p=0,1,…P-1)th range ambiguity clutter component.

[0080] The distance fuzzy orthogonal projection matrix calculation expression is:

[0081]

[0082] Where A r,p,amb is the orthogonal projection matrix of the p-th (p=0,1,…P-1) distance blur component.

[0083] The orthogonal projection weighted vector calculation expression is:

[0084] ω amb,0 =A r,1,amb A r,2,amb …A r,p,amb a amb,0

[0085] Where, ω amb,0 To extract the zeroth-order range fuzzy clutter component, that is, the orthogonal projection weight vector of the unambiguous range clutter component, I is the unit matrix.

[0086] The pitch multi-channel signal vector calculation expression is:

[0087]

[0088] Where, represents the pitch multi-channel signal vector constructed by the echo signal at the j-th azimuth sub-channel, represents the back-Doppler domain radar echo signal at the i-th elevation sub-channel and the j-th azimuth sub-channel.

[0089] The following describes the specific implementation steps of a method for suppressing range ambiguity clutter in a space-based early warning radar based on orthogonal projection in this embodiment.

[0090] Each implementation step of this embodiment is carried out on the MATLAB R2018a simulation platform.

[0091] like Figure 1 As shown, the implementation steps of this embodiment include:

[0092] S1: Input N r ×N a Baseband echo data of multi-channel space-based early warning radar in elevation and azimuth r,i,j (t,t m ), i=1,2,…N r ,j=1,2,…N a , where N r =12, N a =16.

[0093] S2: Perform range pulse compression and azimuth pulse compression processing on the baseband echo signal of the elevation multi-channel space-based early warning radar described in the previous step, and convert it into the post-Doppler radar echo signal in formula (1).

[0094] S3: For the pitch-azimuth multi-channel echo data in the post-Doppler domain described in the previous step, traverse different range units in turn and calculate the lower viewing angle θ of the different range ambiguity components of each range unit el,amb,p , p=0,1,…P-1, where P=5.

[0095] S4: Calculate the true Doppler frequency for each of the distance units mentioned in the previous step according to the system prior information and the baseband multi-channel frequency until all Doppler units are traversed.

[0096] S5: Based on the viewing angles of the different range ambiguity components in step S3 and the true Doppler frequency in the previous step, use formula (2) to calculate the azimuth angle θ of the different range ambiguity components at different Doppler frequencies: azi,amb,p , p=0,1,…P-1.

[0097] S6: At different azimuth sub-channels, the viewing angle θ under different distance blur components described in step S3 el,amb,p The azimuth angles θ of the different range ambiguity components at different Doppler frequencies described in the previous step are azi,amb,p , use formula (3), formula (4) and formula (5) to calculate the pitch multi-channel steering vector, range fuzzy orthogonal projection matrix and orthogonal projection weight vector of different range fuzzy clutter components in turn

[0098] S7: Use the orthogonal projection weight vector in the previous step to weight the pitch multi-channel signal vector of formula (6) to obtain the following: At the j-th azimuth sub-channel, there is no range ambiguity signal s after range ambiguity suppression processing j,sup (t,f a ), j=1,2,…N a :

[0099]

[0100] S8: The range-free ambiguity signal s extracted from the different azimuth sub-channels in the previous step j,sup (t,f a ), j=1,2,…N a Perform Doppler center correction to obtain s j,comp (t,f a ), j=1,2,…N a .

[0101] S9: Combine the azimuth multi-channel signal s after the Doppler center correction process described in the previous step j,comp (t,f a ), j=1,2,…N a , clutter suppression processing is performed based on space-time adaptive processing technology.

[0102] S10: The final output is the residual map after range ambiguity clutter suppression processing in the space-based early warning radar system.

[0103] The range fuzzy clutter suppression processing results of the elevation and azimuth multi-channel space-based early warning radar based on the orthogonal projection technology obtained according to the present invention are as follows: Figure 2-Figure 6 As shown. Among them, Figure 2 To consider the image of the pitch-azimuth space-based early warning radar echo signal in the post-Doppler domain with range ambiguity clutter, Figure 3-Figure 5 The results of range ambiguity suppression processing based on the present invention, Doppler center correction results, STAP processing residual map and target focus result magnification map are shown respectively. Figure 6 A comparison of target slices using the present invention and without range ambiguity suppression is provided. The results show that the method provided by the present invention can effectively suppress range ambiguity clutter, significantly improving the clutter suppression and moving target detection performance of the space-based early warning radar system.

[0104] The present invention also provides a space-based early warning radar range ambiguity clutter suppression processing system. The system can be implemented by executing the process steps of the space-based early warning radar range ambiguity clutter suppression processing method. That is, those skilled in the art can understand the space-based early warning radar range ambiguity clutter suppression processing method as a preferred implementation of the space-based early warning radar range ambiguity clutter suppression processing system.

[0105] A space-based early warning radar range ambiguity clutter suppression processing system, comprising:

[0106] Signal conversion module: obtains the multi-channel baseband echo data of the space-based early warning radar in elevation and azimuth, performs range and azimuth pulse compression processing, converts the multi-channel echo signal into the post-Doppler domain, and obtains the multi-channel baseband echo data in the post-Doppler domain in elevation and azimuth;

[0107] Azimuth calculation module: This module sequentially traverses all range cells for the post-Doppler domain elevation and azimuth multi-channel baseband echo data, calculates the downward viewing angle corresponding to the different range ambiguity components of each range cell, calculates the true Doppler frequency based on the radar system prior information and the baseband Doppler frequency, and then sequentially calculates the azimuth angle values ​​of each range ambiguity component corresponding to different Doppler frequencies;

[0108] Range-free clutter extraction module: traverses different azimuth sub-channels, combines the pitch multi-channels to construct an orthogonal projection weighted vector, performs range-free clutter suppression, and extracts range-free clutter.

[0109] Range ambiguity clutter suppression processing module: Performs Doppler center correction processing on clutter without range ambiguity, and then combines azimuth multi-channel clutter suppression processing based on space-time adaptive processing technology to obtain the residual image after range ambiguity clutter suppression processing.

[0110] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0111] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for suppressing range ambiguity clutter in a space-based early warning radar, characterized in that: include: Signal conversion step: Acquire the elevation and azimuth multi-channel baseband echo data of the space-based early warning radar, perform range and azimuth pulse compression processing, convert the multi-channel echo signal to the post-Doppler domain, and obtain the post-Doppler domain elevation and azimuth multi-channel baseband echo data; Azimuth angle calculation steps: The post-Doppler domain elevation and azimuth multi-channel baseband echo data is sequentially traversed through all range cells, and the corresponding downward viewing angle corresponding to the different range ambiguity components of each range cell is calculated. The true Doppler frequency is calculated based on the radar system prior information and the baseband Doppler frequency. The azimuth angle values ​​of each range ambiguity component corresponding to different Doppler frequencies are then calculated in sequence. Range-free clutter extraction steps: traverse different azimuth sub-channels, combine the pitch multi-channels to construct an orthogonal projection weighted vector, perform range-free clutter suppression, and extract range-free clutter; Range ambiguity clutter suppression processing steps: Doppler center correction processing is performed on the clutter without range ambiguity, and then clutter suppression processing is performed based on the space-time adaptive processing technology of the azimuth multi-channel to obtain the residual image after range ambiguity clutter suppression processing; The step of extracting clutter without range ambiguity includes: sequentially calculating the elevation multi-channel steering vectors, the range ambiguity orthogonal projection matrix, and the orthogonal projection weighting vectors of the different range ambiguity clutter components according to the downward viewing angles and azimuth angles corresponding to the different range ambiguity clutter components, and then performing weighted processing on the elevation and azimuth multi-channel baseband echo data vectors in the post-Doppler domain.

2. The method for suppressing range ambiguity clutter of a space-based early warning radar according to claim 1, characterized in that: The calculation expression of the post-Doppler domain pitch-azimuth multi-channel baseband echo data is: Where sinc(·) is the Sigmoid function, represents the post-Doppler domain echo signal of the space-based early warning radar of the i-th elevation sub-channel and the j-th azimuth sub-channel, N r and N a are the number of elevation sub-channels and azimuth sub-channels of the radar system, d i and d j Represents the radar antenna pitch sub-channel arrangement and radar antenna azimuth sub-channel arrangement of the i-th pitch sub-channel and the j-th azimuth sub-channel, respectively. and d r and d a is the physical spacing of the radar antenna elevation sub-channel and the physical spacing of the azimuth sub-channel, and R 0,p They represent the amplitude term of the p-th range ambiguity clutter signal at the i-th pitch sub-channel, the j-th azimuth sub-channel, and the initial slant range of the p-th range ambiguity clutter component, θ el,amb,p and θ azi,p It represents the lower viewing angle and azimuth of the pth range fuzzy clutter component, t is the range fast time variable, f a is the Doppler frequency variable, B represents the system bandwidth, θ inc is the radar antenna installation inclination angle, λ is the wavelength, T a is the accumulation time, v represents the platform running speed, ρ crb Indicates the system yaw amplitude, is the system yaw angle.

3. The method for suppressing range ambiguity clutter of a space-based early warning radar according to claim 2, characterized in that: The azimuth calculation expressions of different distance blur components are: Where θ el,amb,p represents the lower viewing angle corresponding to the p-th range blurred clutter component, and acos(·) represents the inverse cosine trigonometric function.

4. The method for suppressing range ambiguity clutter of a space-based early warning radar according to claim 1, characterized in that: The calculation expression of the pitch multi-channel steering vector of the fuzzy clutter components at different distances is: Where a amb,p is the pitch multi-channel steering vector of the p-th range ambiguity clutter component; The distance fuzzy orthogonal projection matrix calculation expression is: Where A r,p,amb is the orthogonal projection matrix of the p-th distance blur component; The orthogonal projection weighted vector calculation expression is: ω amb,0 =A r,1,amb A r,2,amb …A r,p,amb a amb,0 Where, ω amb,0 To extract the zeroth-order range fuzzy clutter component, that is, the orthogonal projection weight vector of the unfuzzy range clutter component, I is the unit matrix; The pitch multi-channel signal vector calculation expression is: Where, represents the pitch multi-channel signal vector constructed by the echo signal at the j-th azimuth sub-channel, Represents the post-Doppler domain elevation and azimuth multi-channel baseband echo data at the i-th elevation sub-channel and the j-th azimuth sub-channel.

5. A space-based early warning radar range ambiguity clutter suppression processing system, characterized in that: include: Signal conversion module: obtains the multi-channel baseband echo data of the space-based early warning radar in elevation and azimuth, performs range and azimuth pulse compression processing, converts the multi-channel echo signal into the post-Doppler domain, and obtains the multi-channel baseband echo data in the post-Doppler domain in elevation and azimuth; Azimuth calculation module: This module sequentially traverses all range cells for the post-Doppler domain elevation and azimuth multi-channel baseband echo data, calculates the downward viewing angle corresponding to the different range ambiguity components of each range cell, calculates the true Doppler frequency based on the radar system prior information and the baseband Doppler frequency, and then sequentially calculates the azimuth angle values ​​of each range ambiguity component corresponding to different Doppler frequencies; Range-free clutter extraction module: traverses different azimuth sub-channels, combines the pitch multi-channels to construct an orthogonal projection weighted vector, performs range-free clutter suppression, and extracts range-free clutter. Range ambiguity clutter suppression processing module: performs Doppler center correction processing on clutter without range ambiguity, and then combines azimuth multi-channel clutter suppression processing based on space-time adaptive processing technology to obtain the residual image after range ambiguity clutter suppression processing; The range-ambiguity-free clutter extraction module includes: sequentially calculating the elevation multi-channel steering vector, the range ambiguity orthogonal projection matrix, and the orthogonal projection weighting vector of different range-ambiguity clutter components according to the downward viewing angle and azimuth angle corresponding to the different range-ambiguity clutter components, and then performing weighted processing on the elevation-azimuth multi-channel baseband echo data vector in the post-Doppler domain.

6. The space-based early warning radar range ambiguity clutter suppression processing system according to claim 5, characterized in that: The calculation expression of the post-Doppler domain pitch-azimuth multi-channel baseband echo data is: Where sinc(·) is the Sigmoid function, represents the post-Doppler domain echo signal of the space-based early warning radar of the i-th elevation sub-channel and the j-th azimuth sub-channel, N r and N a are the number of elevation sub-channels and azimuth sub-channels of the radar system, d i and d j Represents the radar antenna pitch sub-channel arrangement and radar antenna azimuth sub-channel arrangement of the i-th pitch sub-channel and the j-th azimuth sub-channel, respectively. and d r and d a is the physical spacing of the radar antenna elevation sub-channel and the physical spacing of the azimuth sub-channel, and R 0,p They represent the amplitude term of the p-th range ambiguity clutter signal at the i-th pitch sub-channel, the j-th azimuth sub-channel, and the initial slant range of the p-th range ambiguity clutter component, θ el,amb,p and θ azi,p It represents the lower viewing angle and azimuth of the pth range fuzzy clutter component, t is the range fast time variable, f a is the Doppler frequency variable, B represents the system bandwidth, θ inc is the radar antenna installation inclination angle, λ is the wavelength, T a is the accumulation time, v represents the platform running speed, ρ crb Indicates the system yaw amplitude, is the system yaw angle.

7. The space-based early warning radar range ambiguity clutter suppression processing system according to claim 6, characterized in that: The azimuth calculation expressions of different distance blur components are: Where θ el,amb,p represents the lower viewing angle corresponding to the p-th range blurred clutter component, and acos(·) represents the inverse cosine trigonometric function.

8. The space-based early warning radar range ambiguity clutter suppression processing system according to claim 5, characterized in that: The calculation expression of the pitch multi-channel steering vector of the fuzzy clutter components at different distances is: Where a amb,p is the pitch multi-channel steering vector of the p-th range ambiguity clutter component; The distance fuzzy orthogonal projection matrix calculation expression is: Where A r,p,amb is the orthogonal projection matrix of the p-th distance blur component; The orthogonal projection weighted vector calculation expression is: ω amb,0 =A r,1,amb A r,2,amb …A r,p,amb a amb,0 Where, ω amb,0 To extract the zeroth-order range fuzzy clutter component, that is, the orthogonal projection weight vector of the unfuzzy range clutter component, I is the unit matrix; The pitch multi-channel signal vector calculation expression is: Where, represents the pitch multi-channel signal vector constructed by the echo signal at the j-th azimuth sub-channel, Represents the post-Doppler domain elevation and azimuth multi-channel baseband echo data at the i-th elevation sub-channel and the j-th azimuth sub-channel.

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