A method for suppressing radar false alarm targets outside rectangular runway

Abstract

The present application belongs to the field of aviation safety technology, and particularly relates to a method for suppressing radar false alarm targets outside a rectangular runway. The method comprises: step 1, determining a rectangular coordinate system, and converting the rectangular runway area information into the linear equations of the four sides; step 2, obtaining the radar longitude and latitude information, the radar centerline heading angle, and the radar instantaneous beam scanning angle through a mobile airport pavement FOD detection radar, and converting the radar longitude and latitude information into the position information of the radar in the rectangular coordinate system, and converting the radar centerline heading angle into the deviation angle between the radar scanning centerline and the coordinate axis, and obtaining the radar line of sight linear equation; step 3, calculating the distance threshold on the radar line of sight according to the linear equations of the four sides and the radar line of sight linear equation; step 4, detecting the target according to the distance threshold on the radar line of sight, and realizing the suppression of radar false alarm targets outside the rectangular runway.

Description

Technical Field

[0001] The present application belongs to the field of aviation safety technology, and in particular relates to a method for suppressing false alarm targets of radar outside a rectangular runway. Background Art

[0002] Foreign Object Debris (FOD) on an airport runway refers to any object that appears in an inappropriate location at an airport. Such objects can scratch aircraft tires, hit aircraft fuel tanks or fuselages, causing aircraft to skid off the runway and cause aircraft accidents. In serious cases, they can endanger the lives and property of passengers, cause flight delays, and interrupt takeoff, resulting in huge economic losses.

[0003] At present, the detection of FOD at home and abroad still basically relies on manual scheduled patrols. This method is not only inefficient and unreliable, but also occupies the use time of the runway, forcing the number of flights to be reduced. In addition, due to human eye fatigue, the missed detection rate is very high, and there is a potential danger for the aircraft to take off on the runway. Many companies and institutions at home and abroad have carried out research and development on FOD detection systems. Nowadays, some large civil aviation airports in Europe and the United States have successively installed FOD detection systems for testing and verification. There are two types of technologies used, one is a fixed detection method and the other is a mobile detection method. Mobile FOD detection equipment uses a vehicle-mounted platform to install millimeter-wave radar to detect FOD. One of the problems encountered by mobile FOD radars during patrol detection is that targets such as roadside lights, grass, and light boxes outside the runway will cause many false alarms in radar detection, resulting in too many targets and unable to detect real FOD targets in the runway area.

[0004] Therefore, it is desired to have a technical solution to overcome or at least alleviate at least one of the above-mentioned defects of the prior art. Summary of the invention

[0005] The purpose of the present application is to provide a method for suppressing radar false alarm targets outside a rectangular runway to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A method for suppressing a radar false alarm target outside a rectangular runway, comprising:

[0008] Step 1: Determine the rectangular coordinate system and convert the rectangular runway area information into the straight line equations of the four sides;

[0009] Step 2: obtain radar longitude and latitude information, radar centerline heading angle and radar instantaneous beam scanning angle through a mobile airport pavement FOD detection radar, convert the radar longitude and latitude information into the position information of the radar in the rectangular coordinate system, convert the radar centerline heading angle into the deviation angle between the radar scanning centerline and the coordinate axis, and obtain the radar line of sight straight line equation;

[0010] Step 3: Calculate the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight;

[0011] Step 4: Detect the target according to the distance threshold on the radar line of sight to achieve radar false alarm target suppression outside the rectangular runway.

[0012] In at least one embodiment of the present application, in step 1, determining a rectangular coordinate system and converting the rectangular runway area information into straight line equations of four sides includes:

[0013] Get the four vertices A, B, C, and D of the rectangular runway area, where AB and CD are short sides, AD and BC are long sides, take vertex A as the origin, the direction of ray AB is the positive direction of the x-axis, and the direction of ray AD is the positive direction of the y-axis, and construct a rectangular coordinate system XoY;

[0014] Determine the rectangular coordinates A(x A ,y A )、B(x B ,y B )、C(x C ,y C )、D(x D ,y D ), when the width of the rectangular runway is W and the length is L, the rectangular coordinates of the four vertices are expressed as A(0,0), B(W,0), C(W,L), D(0,L);

[0015] The straight line equations of the four sides of the rectangular runway are:

[0016] AB: y = 0

[0017] BC: x = W

[0018] CD:y=L

[0019] DA:x=0.

[0020] In at least one embodiment of the present application, the mobile airport pavement FOD detection radar includes a mobile platform, a millimeter wave radar, a global positioning device and a display device, and the millimeter wave radar, the global positioning device and the display device are all installed on the mobile platform.

[0021] In at least one embodiment of the present application, in step 2, the radar longitude and latitude information, the radar centerline heading angle, and the radar instantaneous beam scanning angle are obtained by the mobile airport pavement FOD detection radar, and the radar longitude and latitude information is converted into the position information of the radar in the rectangular coordinate system, and the radar centerline heading angle is converted into the deviation angle between the radar scanning centerline and the coordinate axis, and the radar line of sight line equation is obtained, including:

[0022] The radar latitude and longitude information, the radar centerline heading angle and the radar instantaneous beam scanning angle θ are obtained through the mobile airport pavement FOD detection radar;

[0023] The radar latitude and longitude information is converted into the radar position information M(x M ,y M ), converting the radar centerline heading angle into the deviation angle between the radar scanning centerline and the y-axis

[0024] Get the radar line of sight equation:

[0025] When the conditions are met:

[0026]

[0027] and

[0028]

[0029] The equation of the radar line of sight is:

[0030]

[0031] When the conditions are met:

[0032]

[0033] or

[0034]

[0035] The equation of the radar line of sight is:

[0036] x=x M

[0037] Among them, the deviation angle between the radar scanning center line and the y-axis The y-axis is 0 degrees, counterclockwise rotation is a positive angle, the value range is [0, 360), and the unit is degree;

[0038] The instantaneous beam scanning angle θ of the radar takes the radar scanning centerline as 0 degrees, with negative angles to the left and positive angles to the right. The value range is [-Az, Az], where Az is the absolute value of the maximum scanning azimuth of the radar, in degrees.

[0039] In at least one embodiment of the present application, in step 3, calculating the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes:

[0040] When the radar sight angle points to the first quadrant, that is,

[0041] Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R;

[0042] Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side CD, and obtain the distance MR' between the radar M and the intersection point R';

[0043] The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0044] In at least one embodiment of the present application, in step 3, calculating the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes:

[0045] When the radar sight angle points to the second quadrant, that is,

[0046] Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N;

[0047] Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side CD, and obtain the distance MN' between the radar M and the intersection point N';

[0048] The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0049] In at least one embodiment of the present application, in step 3, calculating the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes:

[0050] When the radar sight angle points to the third quadrant, that is,

[0051] Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N;

[0052] Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side AB, and obtain the distance MN' between the radar M and the intersection point N';

[0053] The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0054] In at least one embodiment of the present application, in step 3, calculating the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes:

[0055] When the radar sight angle points to the fourth quadrant, that is,

[0056] Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R;

[0057] Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side AB, and the distance MR' between the radar M and the intersection point R';

[0058] The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0059] The invention has at least the following beneficial technical effects:

[0060] The method for suppressing false alarm targets of radar outside a rectangular runway of the present application can utilize the positioning data of the terrain and the operating parameters of the radar to calculate the detection range of the radar under working conditions in real time, limit the range of target reporting, and solve the problem that the radar cannot complete the detection of the designated area due to target saturation caused by false alarms in the non-detection area. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a flow chart of a method for suppressing false alarm targets of a radar outside a rectangular runway according to an embodiment of the present application;

[0062] Figure 2 is a schematic diagram of a rectangular coordinate system of an embodiment of the present application;

[0063] Figure 3 It is a schematic diagram of a mobile airport pavement FOD detection radar according to one embodiment of the present application.

[0064] in:

[0065] 1-Mobile platform; 2-Millimeter wave radar; 3-Global positioning device; 4-Display device. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the drawings.

[0067] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present application.

[0068] The following is combined with Figures 1 to 3 This application is described in further detail.

[0069] The present application provides a method for suppressing false alarm targets of radar outside a rectangular runway, comprising the following steps:

[0070] Step 1: Determine the rectangular coordinate system and convert the rectangular runway area information into the straight line equations of the four sides;

[0071] Step 2: obtain the radar latitude and longitude information, the radar centerline heading angle and the radar instantaneous beam scanning angle through the mobile airport pavement FOD detection radar, and convert the radar latitude and longitude information into the position information of the radar in the rectangular coordinate system, convert the radar centerline heading angle into the deviation angle between the radar scanning centerline and the coordinate axis, and obtain the radar line of sight straight line equation;

[0072] Step 3: Calculate the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight;

[0073] Step 4: Detect the target according to the distance threshold on the radar line of sight to achieve radar false alarm target suppression outside the rectangular runway.

[0074] In a preferred embodiment of the present application, in step 1, determining a rectangular coordinate system, converting the rectangular runway area information into straight line equations of four sides includes:

[0075] Get the four vertices A, B, C, and D of the rectangular runway area, where AB and CD are short sides, AD and BC are long sides, and take vertex A as the origin. The direction of ray AB is the positive direction of the x-axis, and the direction of ray AD is the positive direction of the y-axis. Construct the rectangular coordinate system XoY, such as Figure 2 As shown;

[0076] Determine the rectangular coordinates A(x A ,y A )、B(x B ,y B )、C(x C ,y C )、D(x D ,y D ), when the width of the rectangular runway is W and the length is L, the rectangular coordinates of the four vertices are expressed as A(0,0), B(W,0), C(W,L), D(0,L);

[0077] The straight line equations of the four sides of the rectangular runway are:

[0078] AB: y = 0

[0079] BC: x = W

[0080] CD:y=L

[0081] DA:x=0.

[0082] The present invention relates to a method for suppressing false alarm targets of a radar outside a rectangular runway, wherein a mobile airport pavement FOD detection radar is used. Figure 3 As shown, it includes a mobile platform 1, a millimeter-wave radar 2, a global positioning device 3 and a display device 4. The millimeter-wave radar 2, the global positioning device 3 and the display device 4 are all loaded on the mobile platform 1. The mobile platform 1 travels along the airport pavement. The millimeter-wave radar 2 combined with the global positioning device 3 can detect the FOD target information in front; the detection distance range of the millimeter-wave radar 2 is Rg; in the millimeter-wave radar 2, the false alarm generated by the targets outside the runway to the radar is suppressed, so as to realize the effective detection of the FOD targets in the runway area.

[0083] In a preferred embodiment of the present application, in step 2, the radar longitude and latitude information, the radar centerline heading angle, and the radar instantaneous beam scanning angle are obtained by a mobile airport pavement FOD detection radar, and the radar longitude and latitude information is converted into the position information of the radar in a rectangular coordinate system, and the radar centerline heading angle is converted into the deviation angle between the radar scanning centerline and the coordinate axis, and the radar line of sight straight line equation is obtained, including:

[0084] The radar latitude and longitude information, the radar centerline heading angle and the radar instantaneous beam scanning angle θ are obtained through the mobile airport pavement FOD detection radar;

[0085] The radar latitude and longitude information is converted into the radar position information M(x M ,y M ), convert the radar centerline heading angle into the deviation angle between the radar scanning centerline and the y-axis

[0086] Get the radar line of sight equation:

[0087] When the conditions are met:

[0088]

[0089] and

[0090]

[0091] The equation of the radar line of sight is:

[0092]

[0093] When the conditions are met:

[0094]

[0095] or

[0096]

[0097] The equation of the radar line of sight is:

[0098] x=x M

[0099] Among them, the deviation angle between the radar scanning center line and the y-axis The y-axis is 0 degrees, counterclockwise rotation is a positive angle, the value range is [0, 360), and the unit is degree;

[0100] The instantaneous beam scanning angle θ of the radar takes the radar scanning centerline as 0 degrees, with negative angles to the left and positive angles to the right. The value range is [-Az, Az], where Az is the absolute value of the maximum scanning azimuth of the radar, in degrees.

[0101] In this embodiment, in step 3, calculating the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes:

[0102] When the radar sight angle points to the first quadrant, that is,

[0103] Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R;

[0104] Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side CD, and obtain the distance MR' between the radar M and the intersection point R';

[0105] The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0106] When the radar sight angle points to the second quadrant, that is,

[0107] Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N;

[0108] Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side CD, and obtain the distance MN' between the radar M and the intersection point N';

[0109] The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0110] When the radar sight angle points to the third quadrant, that is,

[0111] Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N;

[0112] Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side AB, and obtain the distance MN' between the radar M and the intersection point N';

[0113] The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0114] When the radar sight angle points to the fourth quadrant, that is,

[0115] Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R;

[0116] Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side AB, and the distance MR' between the radar M and the intersection point R';

[0117] The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

[0118] The method for suppressing false alarm targets of radar outside a rectangular runway of the present application finally adopts the calculated distance limit on the radar line of sight as the distance threshold, detects targets within the threshold, and does not detect targets outside the threshold, thereby realizing the suppression of false alarm targets of radar outside the runway.

[0119] In one embodiment of the present application, the width W and length L of the rectangular runway are 45m and 3600m respectively, the detection range Rg of the millimeter wave radar 2 is 160m, and the radar scanning deviation angle The range is [0, 360), and the range of the radar instantaneous beam scanning angle θ is [-25°, 25°].

[0120] First, obtain the four vertices A, B, C, and D of the rectangular runway area, and construct a rectangular coordinate system with point A as the origin, the short side (AB) as the X-axis, and the long side (AD) as the Y-axis. The four vertices are converted to A (0, 0), B (45, 0), C (45, 3600), and D (0, 3600) accordingly, thus forming AB, BC, CD, and DA. The four boundary equations are:

[0121] AB: y = 0

[0122] BC: x = 45

[0123] CD: y = 3600

[0124] DA: x = 0

[0125] Secondly, the longitude and latitude of the radar are obtained by the global positioning device 3 of the mobile airport pavement FOD detection radar, and converted into the rectangular coordinate system point M (25, 100), and the deviation angle between the radar scanning center line and the y axis is 2°, and the radar instantaneous beam scanning angle θ is -20°, thus determining the radar line of sight equation:

[0126] y=tan(90+2+20)*(x-25)+100

[0127] Further, calculate the distance threshold on the radar line of sight:

[0128] Joint:

[0129] x=0

[0130] y=tan(90+2+20)*(x-25)+100

[0131] The coordinates of the intersection point N of the radar line of sight ray and the AD edge are obtained (0, 162), and the distance of MN is obtained as 66.85m;

[0132] Joint:

[0133] y=3600

[0134] y=tan(90+2+20)*(x-25)+100

[0135] The coordinates of the intersection point N' of the radar line of sight ray and the CD edge are obtained (-1389, 3600), and the distance MN' is obtained as 3774m;

[0136] The minimum value MN(66.85) among MN(66.85), MN'(3774) and Rg(160) is taken as the effective range limit on the current radar line of sight.

[0137] Finally, when the radar is at point M (25, 100), the radar scans the deviation angle When the scanning angle θ is 2° and the scanning angle θ is -20°, there are 6 targets in the current radar line of sight, and their coordinates are (66.85, -20°), (141, -20°), (172, -20°), (195, -20°), (201, -20°), and (235, -20°).

[0138] When the method of the present application is not used, false alarm targets outside the runway will cause the radar to be unable to complete detection; after using the method of the present application, the targets within the threshold (66.85, -20°) are detected, and the targets outside the threshold are not detected, which can achieve the suppression of false alarm targets of the radar outside the runway.

[0139] The method for suppressing the false alarm target of the radar outside the rectangular runway of the present application can use the positioning data of the terrain and the radar working parameters to calculate the detection interval of the radar under the working conditions in real time, limit the range of the target report, and solve the problem that the radar cannot complete the detection of the designated area due to the target saturation caused by the false alarm in the non-detection area. The present application is applicable to the situation where radars such as radars or optical devices are used for target detection in various environments such as airports and roads.

[0140] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for suppressing false alarm targets of radar outside a rectangular runway, characterized in that: include: Step 1: Determine the rectangular coordinate system and convert the rectangular runway area information into the straight line equations of the four sides, including: Get the four vertices A, B, C, and D of the rectangular runway area, where AB and CD are short sides, AD and BC are long sides, take vertex A as the origin, the direction of ray AB is the positive direction of the x-axis, and the direction of ray AD is the positive direction of the y-axis, and construct a rectangular coordinate system XoY; Determine the rectangular coordinates A(x A ,y A )、B(x B ,y B )、C(x C ,y C )、D(x D ,y D ), when the width of the rectangular runway is W and the length is L, the rectangular coordinates of the four vertices are expressed as A(0,0), B(W,0), C(W,L), D(0,L); The straight line equations of the four sides of the rectangular runway are: AB: y = 0 BC: x = W CD:y=L DA: x = 0; Step 2: Obtain radar latitude and longitude information, radar centerline heading angle, and radar instantaneous beam scanning angle θ through a mobile airport pavement FOD detection radar, and convert the radar latitude and longitude information into the position information of the radar in the rectangular coordinate system, and convert the radar centerline heading angle into the deviation angle between the radar scanning centerline and the coordinate axis y-axis. Get the radar line of sight equation; Step 3: Calculate the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight; Step 4: Detect the target according to the distance threshold on the radar line of sight to achieve radar false alarm target suppression outside the rectangular runway; In step 3, the calculation of the distance threshold on the radar line of sight according to the straight line equations of the four sides and the straight line equation of the radar line of sight includes: When the radar sight angle points to the first quadrant, that is, Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R; Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side CD, and obtain the distance MR' between the radar M and the intersection point R'; The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar; When the radar sight angle points to the second quadrant, that is, Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N; Combine the straight line equation of the short side CD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side CD, and obtain the distance MN' between the radar M and the intersection point N'; The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar; When the radar sight angle points to the third quadrant, that is, Combine the straight line equation of the long side AD and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N of the radar line of sight and the long side AD, and obtain the distance MN between the radar M and the intersection point N; Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point N' of the radar line of sight and the short side AB, and obtain the distance MN' between the radar M and the intersection point N'; The minimum value among MN, MN' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar; When the radar sight angle points to the fourth quadrant, that is, Combine the straight line equation of the long side BC and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R of the radar line of sight and the long side BC, and obtain the distance MR between the radar M and the intersection point R; Combine the straight line equation of the short side AB and the straight line equation of the radar line of sight to obtain the coordinates of the intersection point R' of the radar line of sight and the short side AB, and obtain the distance MR' between the radar M and the intersection point R'; The minimum value among MR, MR' and Rg is used as the distance threshold on the current radar line of sight, where Rg is the detection distance range of the millimeter wave radar.

2. The method for suppressing false alarm targets of radar outside a rectangular runway according to claim 1, characterized in that: The mobile airport pavement FOD detection radar comprises a mobile platform (1), a millimeter wave radar (2), a global positioning device (3) and a display device (4); the millimeter wave radar (2), the global positioning device (3) and the display device (4) are all installed on the mobile platform (1).

3. The method for suppressing false alarm targets of radar outside a rectangular runway according to claim 2, characterized in that: In step 2, the radar longitude and latitude information, the radar centerline heading angle, and the radar instantaneous beam scanning angle are obtained by the mobile airport pavement FOD detection radar, and the radar longitude and latitude information is converted into the position information of the radar in the rectangular coordinate system, and the radar centerline heading angle is converted into the deviation angle between the radar scanning centerline and the coordinate axis, and the radar line of sight straight line equation is obtained, including: The radar latitude and longitude information, the radar centerline heading angle and the radar instantaneous beam scanning angle θ are obtained through the mobile airport pavement FOD detection radar; The radar latitude and longitude information is converted into the radar position information M(x M ,y M ), converting the radar centerline heading angle into the deviation angle between the radar scanning centerline and the y-axis Get the radar line of sight equation: When the conditions are met: and The equation of the radar line of sight is: When the conditions are met: or The equation of the radar line of sight is: x=x M Among them, the deviation angle between the radar scanning center line and the y-axis The y-axis is 0 degrees, counterclockwise rotation is a positive angle, the value range is [0, 360), and the unit is degree; The instantaneous beam scanning angle θ of the radar takes the radar scanning centerline as 0 degrees, with negative angles to the left and positive angles to the right. The value range is [-Az, Az], where Az is the absolute value of the maximum scanning azimuth of the radar, in degrees.

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