阅读说明：本技术 一种机载雷达的主瓣杂波时频域分布的计算方法 (Calculation method for time-frequency domain distribution of mainlobe clutter of airborne radar ) 是由 梅慧 易堃 祝伟才 汪超 罗伟伦 杜若非 于 2021-08-04 设计创作，主要内容包括：本发明公开了一种机载雷达主瓣杂波时频域分布的计算方法,包括：将雷达的主瓣波束的波束指向转换至北天东坐标系；计算所述主瓣波束相对照射面的照射角；根据所述照射角、主瓣波束宽度和载机飞行高度计算杂波在时域上的位置分布；根据载机飞行速度与雷达主瓣波束参数计算杂波在频域上的位置分布,本发明通过实时快速计算主瓣杂波在时域和频域上二维分布结果,为机载雷达进行目标检测划出检测盲区边界避免产生虚警,针对目标连续跟踪时提供避开主瓣杂波盲区的依据。(The invention discloses a method for calculating the time-frequency domain distribution of main lobe clutter of an airborne radar, which comprises the following steps: converting the beam direction of a main lobe beam of the radar to a North heaven coordinate system; calculating an irradiation angle of the main lobe beam relative to an irradiation surface; calculating the position distribution of the clutter on the time domain according to the illumination angle, the main lobe beam width and the flight height of the carrier; according to the method, the position distribution of the clutter on the frequency domain is calculated according to the flight speed of the airborne radar and the radar mainlobe beam parameters, the two-dimensional distribution results of the mainlobe clutter on the time domain and the frequency domain are quickly calculated in real time, the boundary of a detection blind area is drawn for the airborne radar to avoid generating false alarms, and a basis for avoiding the mainlobe clutter blind area is provided for the continuous tracking of the target.)

1. A method for calculating the time-frequency domain distribution of the mainlobe clutter of an airborne radar is characterized by comprising the following steps:

step S1, converting the beam direction of the main lobe beam of the radar to a North heaven coordinate system;

step S2, calculating the irradiation angle of the main lobe beam relative to the irradiation surface;

step S3, calculating the position distribution of clutter on a time domain according to the illumination angle, the mainlobe beam width and the flight height of the carrier;

and step S4, calculating the position distribution of the clutter on the frequency domain according to the flight speed of the carrier and the radar mainlobe beam parameters.

2. The method of claim 1 wherein the radar beam parameters include beamwidth of the mainlobe beam, azimuth pointing angle and elevation pointing angle of the mainlobe beam relative to the antenna front.

3. The method for calculating the time-frequency domain distribution of the airborne radar mainlobe clutter according to claim 2, wherein the step S1 comprises:

the beam pointing angle of the main lobe beam of the radar relative to the antenna array is (theta)_y,θ_z) The pointing angle (theta) of the main lobe beam_y,θ_z) Conversion to the coordinate system of the carrier (x)₁,y₁,z₁) The following:

wherein, theta_yIndicating the azimuthal orientation, theta, of the main lobe beam with respect to the antenna array_zRepresenting the pitch orientation of the main lobe beam relative to the antenna array;

directing beams according to carrier attitude angle from carrier coordinate system (x)₁,y₁,z₁) Go to the North Tiandong coordinate System (x)₂,y₂,z₂) The following:

wherein, theta_N、θ_E、θ_DRespectively representing the pitch angle, the roll angle and the yaw angle of the attitude angle of the carrier.

4. The method for calculating the time-frequency domain distribution of the airborne radar mainlobe clutter according to claim 3, wherein the step S2 comprises:

calculating azimuth angle theta of beam pointing under north heaven coordinate system'_yAnd a pitch angle θ'_z：

θ′_z＝asin(-z₂)

Depression elevation angle theta 'under north heaven coordinate system according to beam pointing'_zCalculating the irradiation angle theta of the main lobe beam relative to the irradiation surface_dep＝-θ′_z。

5. The method for calculating the time-frequency domain distribution of the airborne radar mainlobe clutter according to claim 4, wherein the step S3 comprises:

the position r distribution of the clutter on the time domain is calculated by adopting the following formula:

wherein, theta_B∈(-θ_BW/2,θ_BW/2)，θ_BWThe main lobe beam width is shown, and h is the height of the aircraft flight relative to the illuminated surface.

6. The method for calculating the time-frequency domain distribution of the airborne radar mainlobe clutter according to claim 5, wherein the step S4 comprises:

the vector of the wave beam pointing to the north heaven coordinate system isThe aircraft flight velocity vector is the aircraft velocity vectorThe two vector angles θ are:

calculating the position f of the clutter on the frequency domain according to the projection of the carrier velocity vector on the mainlobe beam_cDistribution:

wherein the content of the first and second substances,indicating the aircraft flight speed at the center of the radar main lobe beamProjection of (2); theta_B∈(-θ_BW/2,θ_BW/2), λ represents the wavelength of the main lobe beam of the radar.

7. An electronic device comprising a processor and a memory, the memory having stored thereon a computer program which, when executed by the processor, implements the method of any of claims 1 to 6.

8. A readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the method of any one of claims 1 to 6.

Technical Field

The invention relates to the field of radar target identification and tracking, in particular to a method for calculating time-frequency domain distribution of main lobe clutter of an airborne radar.

Background

When the main lobe beam of the airborne radar for target detection irradiates the ground, the sea surface (under the condition) or the cloud layer (on the condition), stronger main clutter can be generated in the echo, and if the position of a target in the echo on the time-frequency two-dimensional graph is in the main clutter area, the target detection and tracking are difficult. Although target detection methods under a background with more clutter exist at present, because the main lobe clutter is generally far stronger than the target echo, the airborne radar should avoid the main clutter region as much as possible when carrying out target detection and tracking.

Disclosure of Invention

The invention aims to provide a method for calculating the time-frequency domain distribution of main lobe clutter of an airborne radar, which is used for rapidly calculating the two-dimensional distribution result of the main clutter in the time domain and the frequency domain in real time, marking out the boundary of a detection blind area for the airborne radar during target detection, avoiding false alarms and achieving the purpose of providing a basis for avoiding the main clutter blind area during continuous target tracking.

In order to achieve the above purpose, the invention is realized by the following technical scheme:

a method for calculating the time-frequency domain distribution of the mainlobe clutter of an airborne radar comprises the following steps:

step S1, converting the beam direction of the main lobe beam of the radar to a North heaven coordinate system;

step S2, calculating the irradiation angle of the main lobe beam relative to the irradiation surface;

step S3, calculating the position distribution of clutter on a time domain according to the illumination angle, the mainlobe beam width and the flight height of the carrier;

and step S4, calculating the position distribution of the clutter on the frequency domain according to the flight speed of the carrier and the radar mainlobe beam parameters.

Optionally, the radar beam parameters include a beam width of the main lobe beam, an azimuth pointing angle and a pitch pointing angle of the main lobe beam with respect to an antenna front.

Optionally, the step S1 includes:

the beam pointing angle of the main lobe beam of the radar relative to the antenna array is (theta)_y,θ_z) The pointing angle (theta) of the main lobe beam_y,θ_z) Conversion to the coordinate system of the carrier (x)₁,y₁,z₁) The following:

wherein, theta_yIndicating the azimuthal orientation, theta, of the main lobe beam with respect to the antenna array_zRepresenting the pitch orientation of the main lobe beam relative to the antenna array;

directing beams according to carrier attitude angle from carrier coordinate system (x)₁,y₁,z₁) Go to the North Tiandong coordinate System (x)₂,y₂,z₂) The following:

wherein, theta_N、θ_E、θ_DRespectively representing the pitch angle, the roll angle and the yaw angle of the attitude angle of the carrier.

Optionally, the step S2 includes:

calculating azimuth angle theta of beam pointing under north heaven coordinate system'_yAnd a pitch angle θ'_z：

θ′_z＝asin(-z₂)

Depression elevation angle theta 'under north heaven coordinate system according to beam pointing'_zCalculating the irradiation angle theta of the main lobe beam relative to the irradiation surface_dep＝-θ′_z。

Optionally, the step S3 includes:

the position r distribution of the clutter on the time domain is calculated by adopting the following formula:

wherein, theta_B∈(-θ_BW/2,θ_BW/2)，θ_BWThe main lobe beam width is shown, and h is the height of the aircraft flight relative to the illuminated surface.

Optionally, the step S4 includes:

the vector of the wave beam pointing to the north heaven coordinate system isThe aircraft flight velocity vector is the aircraft velocity vectorThe two vector angles θ are:

calculating the position f of the clutter on the frequency domain according to the projection of the carrier velocity vector on the mainlobe beam_cDistribution:

wherein the content of the first and second substances,representing a projection of the aircraft flight speed on the center of a radar main lobe beam; theta_B∈(-θ_BW/2,θ_BW/2), λ represents the wavelength of the main lobe beam of the radar.

In another aspect, the present invention also provides an electronic device comprising a processor and a memory, the memory having stored thereon a computer program which, when executed by the processor, implements the method as described above.

In yet another aspect, the present invention also provides a readable storage medium having stored therein a computer program which, when executed by a processor, implements a method as described above.

The invention has at least one of the following advantages:

the main lobe clutter calculation model based on the aircraft flight parameters (the aircraft flight parameters comprise an aircraft flight attitude angle, an aircraft flight speed vector and an aircraft flight height) and the radar beam parameters (the radar beam parameters comprise a radar main beam width, an azimuth pointing angle and a pitching pointing angle of the main beam relative to an antenna array surface) can quickly calculate the distribution condition of the main lobe clutter on two positions of a time-frequency domain in real time, so that a detection blind area boundary is drawn for the aircraft radar to avoid false alarm, and a basis for avoiding the main lobe clutter blind area is provided for the continuous tracking of a target.

Drawings

Fig. 1 is a schematic flowchart of a method for calculating time-frequency domain distribution of mainlobe clutter of an airborne radar according to an embodiment of the present invention;

FIG. 2 is a schematic representation of coordinates of a north heaven coordinate system and an airborne coordinate system according to an embodiment of the present invention;

fig. 3 is a schematic diagram of simulation clutter related to a unit partition method according to an embodiment of the present invention.

Detailed Description

The following describes in detail a method for calculating time-frequency domain distribution of mainlobe clutter of an airborne radar according to the present invention with reference to the accompanying drawings and the detailed description. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise scale for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.

As shown in fig. 1, the present embodiment provides a method for calculating time-frequency domain distribution of mainlobe clutter of an airborne radar, including:

and step S1, converting the beam direction of the main lobe beam of the radar into a North east coordinate system.

Specifically, as shown in fig. 2, the speed of the carrier in the projectile coordinate system (satisfying the right-hand criterion xyz) is (V)_x,V_y,V_z) Attitude angles of the carrier are in a northeast coordinate system (meeting right-hand criterion NED): theta_DIs yaw angle, θ_ETo a pitch angle, θ_NIs the roll angle. The step S1 includes:

the beam pointing angle of the main lobe beam of the radar relative to the antenna array is (theta)_y,θ_z) The pointing angle (theta) of the main lobe beam_y,θ_z) Conversion to the coordinate system of the carrier (x)₁,y₁,z₁) The following:

wherein, theta_yIndicating the azimuthal orientation, theta, of the main lobe beam with respect to the antenna array_zRepresenting the pitch orientation of the main lobe beam relative to the antenna array;

directing beams according to carrier attitude angle from carrier coordinate system (x)₁,y₁,z₁) Go to the North Tiandong coordinate System (x)₂,y₂,z₂) The following:

wherein the content of the first and second substances,θ_N、θ_E、θ_Drespectively representing the pitch angle, the roll angle and the yaw angle of the attitude angle of the carrier.

The radar beam parameters include a beam width of the main lobe beam, an azimuth pointing angle and a pitch pointing angle of the main lobe beam with respect to an antenna front.

And step S2, calculating the irradiation angle of the main lobe beam relative to the irradiation surface.

Specifically, the step S2 includes:

calculating azimuth angle theta of beam pointing under north heaven coordinate system'_yAnd a pitch angle θ'_z：

θ′_z＝asin(-z₂) (4)

Depression elevation angle theta 'under north heaven coordinate system according to beam pointing'_zCalculating the irradiation angle theta of the main lobe beam relative to the irradiation surface_dep＝-θ′_z(positive downward).

And step S3, calculating the position distribution of the clutter (the clutter in the embodiment is the main lobe clutter) on the time domain according to the illumination angle, the main lobe beam width and the flight height of the carrier.

The step S3 includes: the position r distribution of the clutter on the time domain is calculated by adopting the following formula:

wherein, theta_B∈(-θ_BW/2,θ_BW/2)，θ_BWThe main lobe beam width is shown, and h is the height of the aircraft flight relative to the illuminated surface.

And step S4, calculating the position distribution of the clutter on the frequency domain according to the flight speed of the carrier and the radar mainlobe beam parameters.

The step S4 includes: the beam is pointed at the north heaven coordinateIs a vector ofThe aircraft flight velocity vector is the aircraft velocity vectorThe two vector angles θ are:

calculating the position f of the clutter on the frequency domain according to the projection of the carrier velocity vector on the mainlobe beam_cDistribution:

wherein the content of the first and second substances,representing a projection of the aircraft flight speed on the center of a radar main lobe beam; theta_B∈(-θ_BW/2,θ_BW/2), λ represents the wavelength of the main lobe beam of the radar.

Calculating a projection component of the flight speed of the carrier in the beam direction according to the included angle between the flight speed vector of the carrier and the beam direction; and calculating clutter Doppler, wherein the distribution of the clutter in a frequency domain depends on the range of an included angle between a flight speed vector and the direction of the wave beam and the wave beam width when the flight speed of the carrier is determined.

In order to better understand the technical solution of the present embodiment, the present embodiment is further described by describing a preferred embodiment in detail.

In this embodiment, the irradiation surface is considered to be a plane surface without considering the fluctuation of the height of the irradiation surface.

Setting the flying speed of the carrier to V_x＝181m/s，V_y＝66m/s，V_zThe flying height h of the carrier relative to the ground is 8 km. The attitude angle of the carrier is as follows: yaw angle theta_D20 deg. and pitch angle theta_E15 DEG roll angle theta_N0 deg.. The beam pointing direction of the radar main lobe beam is: azimuth angle theta_y0 DEG and theta_z15. The main lobe beam width of the radar is theta_BWAt 9 deg.. The wavelength of the radar main lobe beam is 25 mm.

Clutter simulation is performed by adopting a range-doppler scattering unit division method, the repetition frequency of waveform pulse is 6.25kHz, and the clutter simulation result is shown in fig. 3. The range of mainlobe clutter is visible in fig. 3: r e (14.1km,18.68km), f_cE (2.55kHz,3.27 kHz). The clutter range is calculated according to the calculation method of the present invention as follows.

The following calculation is carried out according to the formula (1):

the calculation is carried out according to the formula (2) to obtain:

calculating according to the formula (3) and the formula (4) to obtain: theta'_y＝20°，θ′_z＝-30°。

Calculated according to the above equation (5): r.epsilon. (14.12km,18.58 km).

Calculated according to the above equations (6) and (7): theta 15.1729 DEG, f_c∈(15.07kHz,15.72kHz)。

Wherein f is_cAfter folding in the frequency domain at a pulse repetition frequency of 6.25kHz (f)_c＝f_c-2 × 6.25) to f_c∈(2.57kHz，3.22kHz)。

The distribution result of the mainlobe clutter calculated by the embodiment in the time-frequency domain is r epsilon (14.12km,18.58km) and f_cEpsilon (2.57kHz, 3.22kHz), and the practical simulated clutter result is r epsilon (14.1km,18.68km), f_cE (2.55kHz,3.27kHz), and the calculation result is basically consistent with the simulation result.

The main lobe clutter (clutter for short) calculation model based on the aircraft flight parameters (the aircraft flight parameters comprise an aircraft flight attitude angle, an aircraft flight speed vector and an aircraft flight height), the radar beam parameters (the radar beam parameters comprise radar main beam width, an azimuth pointing angle and a pitching pointing angle of a main beam relative to an antenna array surface) can quickly calculate the distribution condition of the main lobe clutter on two positions of a time-frequency domain in real time, a detection blind area boundary is drawn for target detection of an aircraft radar to avoid false alarm, and a basis for avoiding the main lobe clutter blind area is provided when the target is continuously tracked.

In another aspect, the present invention also provides an electronic device comprising a processor and a memory, the memory having stored thereon a computer program which, when executed by the processor, implements the method as described above.

In yet another aspect, the present invention also provides a readable storage medium having stored therein a computer program which, when executed by a processor, implements a method as described above.

In summary, the present embodiment provides a method for calculating the distribution of the mainlobe clutter in the time-frequency domain of the airborne radar, which calculates the distribution boundary of the mainlobe clutter in the time-frequency domain in real time based on the flight parameters of the airborne radar and the radar beam pointing direction. When the airborne radar carries out downward-looking target detection, a main lobe beam of the radar irradiates the ground or the sea surface to generate stronger main clutter, the distribution of the clutter on a time domain depends on the distance between a plane area irradiated by the main beam and the airborne radar, and the distribution on a frequency domain depends on the projection component of the speed of the airborne radar on the main beam. Therefore, the method for calculating the mainlobe clutter distribution mainly comprises the following processes: calculating the irradiation angle of the radar main beam relative to the irradiation surface through coordinate system conversion based on the flying speed vector of the carrier and the radar beam direction under the carrier coordinate system; calculating the upper and lower boundaries of the time domain clutter distribution according to the height of the carrier relative to the ground, the illumination angle and the main beam width; and calculating the upper and lower boundaries of the frequency domain clutter distribution according to the relation between the flight speed vector of the carrier and the beam direction. And finally, obtaining a time-frequency domain distribution result of the main clutter. The main clutter calculation model adopted by the embodiment can quickly calculate the distribution condition of the main clutter on two positions of a time-frequency domain in real time, so that a detection blind area boundary is drawn out for target detection of the airborne radar to avoid generating a false alarm, and a basis for avoiding the main clutter blind area is provided when the target is continuously tracked.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

It should be noted that the apparatuses and methods disclosed in the embodiments herein can be implemented in other ways. The apparatus embodiments described above are merely illustrative, and for example, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments herein. In this regard, each block in the flowchart or block diagrams may represent a module, a program, or a portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In addition, the functional modules in the embodiments herein may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.