An airborne machine phase-scan radar (SAR) mode beam steering method

Abstract

The application belongs to the technical field of airborne synthetic aperture radar (SAR) mode beam control, and particularly relates to a kind of airborne synthetic aperture radar (SAR) mode beam control method, and relates to the electric scanning and mechanical scanning control method of antenna azimuth beam and elevation beam pointing, in the spotlight SAR mode, azimuth beam and elevation beam can always well cover the center of imaging area in the same aperture time, to ensure SAR image quality and azimuth resolution; in the strip SAR mode, azimuth beam can always well be orthogonal to the imaging track angle, to ensure SAR image quality and moving target positioning accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of airborne phase scanning radar SAR mode beam control, and particularly relates to an airborne phase scanning radar SAR mode beam control method, and relates to an electric scanning and mechanical scanning control method for antenna azimuth beam and elevation beam pointing. BACKGROUND

[0002] With the increasing complexity of radar use scenarios, in addition to the traditional detection and monitoring capability for ground and low-altitude targets, a high-resolution imaging capability for ground targets is also required, for example, a helicopter-borne surveillance and early warning radar.

[0003] In a specified mission airspace, the aircraft usually needs to perform reconnaissance and surveillance tasks multiple times back and forth, and the aircraft trajectory is composed of curved segments and straight-line segments. Usually, only on the straight-line route, the radar can output high-quality SAR images.

[0004] In the SAR mode, a plurality of apertures are composed, and in each aperture time, the antenna beam needs to cover the same target area for the radar to output high-quality spotlight SAR images. In the strip SAR mode, the antenna beam pointing angle needs to always maintain an orthogonal relationship with the imaging track angle in each aperture time, so that the radar can output high-quality strip SAR images, and the moving target can be superimposed on the SAR image with high positioning accuracy.

[0005] The airborne phase scanning radar has the functional features of mechanical azimuth 360-degree scanning and azimuth + elevation two-dimensional electric beam scanning. Due to atmospheric disturbance, the heading of the aircraft fluctuates irregularly on the straight-line route. At present, the airborne phase scanning radar adjusts the antenna beam pointing in real time through a servo motor. For a radar antenna with a large aperture and large inertia, this technical solution has the following defects:

[0006] 1) The antenna beam pointing lags due to inertia, and the antenna cannot be rotated to the azimuth command angle position in time. In the spotlight mode, the radar antenna azimuth beam does not cover the same target in the same aperture time, and in the strip SAR mode, the radar antenna azimuth beam pointing does not maintain an orthogonal relationship with the imaging track angle.

[0007] 2) The antenna beam pointing leads due to inertia, and the antenna rotates beyond the azimuth command angle position. In the spotlight mode, the radar antenna azimuth beam does not cover the same target in the same aperture time, and in the strip SAR mode, the radar antenna azimuth beam pointing does not maintain an orthogonal relationship with the imaging track angle.

[0008] The present application is proposed in view of the above technical defects. SUMMARY

[0009] The purpose of the present application is to provide an airborne radar S AR mode beam control method to overcome or alleviate at least one aspect of the known technical defects.

[0010] The technical solution of the present application is:

[0011] An airborne radar S AR mode beam control method, for the spotlight S AR mode, comprising:

[0012] S11, receiving inertial navigation data in real time, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C;

[0013] S12, using the inertial navigation longitude Lon ins , latitude Lat ins , height H ins and the longitude lon sar , latitude Lat sar , height H sar of the imaging area, to calculate the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr of the radar antenna beam;

[0014] S13, converting the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr into the radar azimuth initial command angle Az_rd_ctr0 and the radar elevation initial command angle El_rd_ctr0 through the coordinate system conversion matrix;

[0015] S14, comparing the radar azimuth initial command angle Az_rd_ctr0 with the radar mechanical azimuth angle Az_serv, and adjusting the initial mechanical azimuth angle through motor control according to the difference value, and comparing the radar elevation initial command angle El_rd_ctr0 with the electrical beam elevation angle El_rd, and performing initial control of the electrical beam elevation direction according to the difference value through the wave control module;

[0016] S15, according to the timing relationship that the n aperture frame Ap_frame(n) pulse moment is aligned with the m processing frame pulse Prc_frame(m), the starting of the m processing frame corresponds to the n aperture frame, and the ending of the m+k-1 processing frame corresponds to the n aperture frame, the processing frame is mapped and divided within the aperture frame time, wherein k is the ratio of the aperture frame period to the processing frame period;

[0017] S16, for the first to n imaging aperture, according to the processing frame period real-time calculation of geographic system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr, the geographic system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr through the coordinate system conversion matrix changes to radar system azimuth command angle Az_rd_ctr and radar system elevation command angle El_rd_ctr, the radar system azimuth command angle Az_rd_ctr and radar system azimuth angle Az_rd comparison, when the difference exceeds the first angle threshold, servo through motor control radar antenna mechanical azimuth angle on the rough adjustment, when the difference is less than the first angle threshold 30° limit, no mechanical azimuth angle on the adjustment, with wave control module on the fine adjustment of the electric beam azimuth angle;

[0018] S17, for the first to n imaging aperture, according to the processing frame period real-time calculation of geographic system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr, the geographic system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr through the coordinate system conversion matrix changes to radar system azimuth command angle Az_rd_ctr and elevation command angle El_rd_ctr, the radar system elevation command angle El_rd_ctr and electric beam elevation angle El_rd comparison, when the difference exceeds the second angle threshold, with wave control module on the adjustment of the electric beam elevation angle, when the difference is less than the second angle threshold, no electric beam elevation angle on the adjustment.

[0019] According to at least one embodiment of the present application, in the above-mentioned airborne machine scanning radar (SAR) mode beam control method, in S1, the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr of the radar antenna beam are calculated in real time by using the longitude Lon ins , latitude Lat ins , height H ins , longitude lon sar , latitude Lat sar , height H sar of the imaging area of the inertial navigation system, and the specific steps are as follows:

[0020]

[0021]

[0022] Detx=

[0023] (N1+H sar )cos(Lat sar )cos(Lon sar )-(N2+H ins )cos(latsar )cos(lon sar );

[0024] Dety =

[0025] (N1+H sar )cos(Lat sar )sin(Lon sar )-(N2+H ins cos(lat) sar sin(lon) sar );

[0026]

[0027] Wayp x =

[0028] -Detx*sin(Lat ins )cos(Lon ins )-Dety*sin(Lat ins )sin(Lon ins )+Detz*

[0029] cos(Lat ins );

[0030] Wayp y =-Detx*sin(Lon ins )+Dety*cos(Lon ins );

[0031] Wayp z =

[0032] Detx*cos(Lat ins )cos(Lon ins )+Dety*cos(Lat ins )sin(Lon ins )+Detz*

[0033] sin(Lat ins );

[0034]

[0035]

[0036] in:

[0037] R a This is the Earth's semi-major axis;

[0038] R bis the semi-major axis of the earth;

[0039] N1, N2, Detx, Dety, Detz, Wayp x , Wayp y , Wayp z is an intermediate calculation.

[0040] According to at least one embodiment of the present application, in the airborne synthetic aperture radar (SAR) mode beam control method described above, in S13, the coordinate system conversion matrix is

[0041]

[0042] According to at least one embodiment of the present application, in the airborne synthetic aperture radar (SAR) mode beam control method described above, in S16, the first angle threshold is 30°.

[0043] According to at least one embodiment of the present application, in the airborne synthetic aperture radar (SAR) mode beam control method described above, in S17, the second angle threshold is 1°.

[0044] According to at least one embodiment of the present application, in the airborne synthetic aperture radar (SAR) mode beam control method described above, for the strip SAR mode, it includes:

[0045] S21, real-time receive inertial navigation data, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C;

[0046] S22, real-time receive imaging track angle Ang_trace_SARctrl;

[0047] S23, calculate the geographic azimuth command angle Az_geo_ctr using the imaging track angle Ang_trace_SARctrl, and utilize the inertial navigation height H ins , imaging area height H sar , to real-time solve the radar antenna beam geographic elevation command angle El_geo_ctr;

[0048] S24, change the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr into the radar system azimuth initial command angle Az_rd_ctr0 and the elevation initial command angle El_rd_ctr0 through the coordinate system conversion matrix;

[0049] S25, imaging the right side view direction, servoing the radar antenna azimuth mechanical angle to 90° position in radar system through motor control, imaging the left side view direction, servoing the radar antenna azimuth mechanical angle to -90° position in radar system through motor control, comparing the radar system azimuth initial command angle Az_rd_ctr0 with the radar system mechanical azimuth angle Az_serv, and according to the difference, the wave control module performs initial adjustment of the electric beam azimuth direction, comparing the radar system elevation initial command angle El_rd_ctr0 with the electric beam elevation angle El_bk, and according to the difference, the wave control module performs initial control of the electric beam elevation direction;

[0050] S26, according to the time sequence relationship that the nth aperture frame Ap_frame(n) pulse moment is aligned with the mth processing frame pulse Prc_frame(m), the mth processing frame corresponds to the start of the nth aperture frame, and the mth+k-1 processing frame corresponds to the end of the nth aperture frame, the processing frame mapping division in the aperture frame time is performed, wherein k is the ratio of the aperture frame period to the processing frame period;

[0051] S27, for the 1st to nth imaging aperture, the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr are calculated in real time according to the processing frame period, the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr are changed into the radar system azimuth command angle Az_rd_ctr and the elevation command angle El_rd_ctr through the coordinate system conversion matrix, and the radar system azimuth command angle Az_rd_ctr is compared with the radar system azimuth angle Az_rd, and according to the difference, the wave control module adjusts the electric beam azimuth angle.

[0052] S28, for the 1st to nth imaging aperture, the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr are calculated in real time according to the processing frame period, the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr are changed into the radar system azimuth command angle Az_rd_ctr and the elevation command angle El_rd_ctr through the coordinate system conversion matrix, and the radar system elevation command angle El_rd_ctr is compared with the radar system elevation angle El_rd, and when the difference exceeds the third angle threshold, the wave control module adjusts the electric beam elevation angle, and when the difference is less than the third angle threshold, the electric beam elevation angle is not adjusted.

[0053] According to at least one embodiment of the present application, in the airborne machine scanning radar SAR mode beam control method described above, in S23, the geographic system azimuth command angle Az_geo_ctr is calculated according to the image trace angle Ang_trace_SARctrl:

[0054] Az_geo_ctrl = Ang_trace_SARctrl + 90 for right-looking direction;

[0055] Az_geo_ctrl = Ang_trace_SARctrl - 90 for left-looking direction.

[0056] According to at least one of the embodiments of the present application, in the airborne machine scanning radar SAR mode beam control method described above, in S23, the calculation of the radar antenna beam geographic system elevation command angle El_geo_ctr is performed, and specifically:

[0057]

[0058] According to at least one of the embodiments of the present application, in the airborne machine scanning radar SAR mode beam control method described above, in S24, the coordinate system conversion matrix is

[0059]

[0060] According to at least one of the embodiments of the present application, in the airborne machine scanning radar SAR mode beam control method described above, the third angle threshold is 1°.

[0061] The present application has at least the following beneficial technical effects:

[0062] The present application provides an aircraft airborne machine scanning radar SAR mode beam control method, which can always cover the center of the imaging area by the azimuth beam and the elevation beam in the same aperture time in the spotlight SAR mode, thereby ensuring the SAR image quality and the azimuth resolution; and the azimuth beam can always be orthogonal to the imaging track angle in the strip SAR mode, thereby ensuring the SAR image quality and the motion target positioning accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 FIG. 1 is a schematic diagram of the airborne machine scanning radar SAR mode beam control method provided by the embodiments of the present application;

[0064] Figure 2 FIG. 4 is a schematic diagram of the processing frame mapping division in the aperture frame time provided by the embodiments of the present application;

[0065] Figure 3 FIG. 6 is an implementation effect diagram of the airborne machine scanning radar spotlight SAR mode beam control provided by the embodiments of the present application;

[0066] Figure 4 FIG. 7 is an implementation effect diagram of the airborne machine scanning radar strip SAR mode beam control provided by the embodiments of the present application.

[0067] For better illustrating the embodiments, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual product size. In addition, the drawings are only used for illustrative description and cannot be understood as a limitation to the present application. DETAILED DESCRIPTION

[0068] In order to make the technical solutions of the present application and the advantages thereof clearer, the technical solutions of the present application will be further clearly and completely described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are only part of the embodiments of the present application, which are only used to explain the present application, but not to limit the present application. It should be noted that, for the convenience of description, only parts related to the present application are shown in the drawings, and other related parts can be referred to the general design.

[0069] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of the present application should be the general meanings understood by the general technical personnel in the field to which the present application belongs. The words indicating the position used in the description of the present application are only used to indicate the relative direction or positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly. The "comprising" used in the description of the present application indicates that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, and other elements or objects are not excluded.

[0070] In addition, it should be further noted that, unless otherwise explicitly specified and limited, the "installation", "connection" and similar words used in the description of the present application should be understood in a broad sense, for example, the connection can be fixed connection or detachable connection; can be mechanical connection or electrical connection; can be directly connected or indirectly connected through intermediate medium, and the person skilled in the art can understand the specific meaning of the present application according to the specific circumstances.

[0071] A method for controlling the beam of a synthetic aperture radar (SAR) mode of an airborne radar is provided, as shown in Figure 1 The method includes: adjusting the direction of the radar antenna azimuth beam by servo through a motor to complete a large deflection angle, and dividing the aperture frame time by using the synchronization and proportion relationship between the aperture frame and the processing frame; calculating the geographic system azimuth and elevation command angle of the radar antenna azimuth beam by using the longitude, latitude and height data of the inertial navigation and the longitude, latitude and height data of the imaging area in the spotlight SAR mode; calculating the geographic system elevation command angle by using the height data of the airborne inertial navigation, the imaging distance and the height data of the imaging area in the strip SAR mode; changing the geographic system azimuth and elevation command angle into the radar system azimuth and elevation command angle by using the coordinate system conversion matrix; adjusting the azimuth electric beam by using the difference between the azimuth command angle and the antenna azimuth angle; and adjusting the elevation electric beam by using the difference between the elevation command angle and the antenna elevation angle.

[0072] In the beam steering SAR mode:

[0073] S11, receiving in real time the inertial navigation data on the aircraft 429 bus, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C, and other data.

[0074] S12, using the inertial navigation longitude Lon ins , latitude Lat ins , height H ins , and the longitude lon sar , latitude Lat sar , height H sar of the imaging area, referring to Formulas 1-10 to calculate the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr of the radar antenna beam in real time.

[0075]

[0076]

[0077] Detx=

[0078] (N1+H sar )cos(Lat sar )cos(Lon sar )-(N2+H ins )cos(lat sar )cos(lon sar )……Formula 3

[0079] Dety=

[0080] (N1+H sar )cos(Lat sar )sin(Lon sar )-(N2+H ins )cos(lat sar )sin(lon sar )……Formula 4

[0081]

[0082]

[0083] Wayp x =

[0084] -Detx*sin(Lat ins )cos(Lon ins )-Dety*sin(Latins )sin(Lon ins )+Detz*

[0085] cos(Lat ins )...Formula 6

[0086] Wayp y =-Detx*sin(Lon ins )+Dety*cos(Lon ins )...Formula 7

[0087] Wayp z =

[0088] Detx*cos(Lat ins )cos(Lon ins )+Dety*cos(Lat ins )sin(Lon ins )+Detz*

[0089] sin(Lat ins )...Formula 8

[0090]

[0091]

[0092] in:

[0093] R a This is the Earth's semi-major axis;

[0094] R b This is the Earth's minor axis;

[0095] N1, N2, Detx, Dety, Detz, Wayp x Wayp y Wayp z This is for intermediate computational costs.

[0096] S13. Transform the geographic system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr into the radar system initial azimuth command angle Az_rd_ctr0 and initial elevation command angle El_rd_ctr0 through the coordinate system transformation matrix.

[0097]

[0098] in: These are the coordinates of the radar system. These are coordinates in the geography system.

[0099] S14, compare the radar system azimuth initial command angle Az_rd_ctr0 with the radar system mechanical azimuth angle Az_serv, and according to the difference delta_Az=(Az_rd_ctr0-Az_serv), the servo controls the radar antenna through the motor to make the initial adjustment of the mechanical azimuth angle, and compare the radar system elevation initial command angle El_rd_ctr0 with the electric wave beam elevation angle El_rd, and according to the difference delta_El=(El_rd_ctr0-El_rd), the wave control module makes the initial control of the electric wave beam elevation direction.

[0100] S15, according to the time sequence relationship that the nth aperture frame Ap_frame(n) pulse moment is aligned with the mth processing frame pulse Prc_frame(m), complete the processing frame mapping division in the aperture frame time, the aperture frame period T and the processing frame period t are in the proportional relationship T=k*t, wherein k is the ratio of the aperture frame period to the processing frame period, complete the mapping relationship between the processing frame and the aperture frame, the mth processing frame corresponds to the start of the nth aperture frame, and the m+k-1th processing frame corresponds to the end of the nth aperture frame, Ap_frame(n)->[prc_frame(m) prc_frame(m+k-1)], as shown in Figure 2

[0101] S16, for the first to nth imaging aperture, according to the processing frame period, refer to formulas 1-10 to calculate the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr in real time, change the geographic system azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr to the radar system azimuth command angle Az_rd_ctr and the radar system elevation command angle El_rd_ctr through the coordinate system conversion matrix of formula 11, compare the radar system azimuth command angle Az_rd_ctr with the radar system azimuth angle Az_rd, when the difference deltaAz=Az_rd_ctr-Az_rd exceeds the first angle threshold 30°, the servo controls the radar antenna through the motor to make the coarse adjustment of the mechanical azimuth angle, when the difference deltaAz=Az_rd_ctr-Az_rd is less than the first angle threshold 30°, no adjustment is made to the mechanical azimuth angle, and the wave control module makes the fine adjustment of the electric wave beam azimuth angle.

[0102] ​S17, for the 1st~nth imaging aperture, real-time calculate the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr according to the processing frame period formula 1~10, change the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr to the radar azimuth command angle Az_rd_ctr and the radar elevation command angle El_rd_ctr through the formula 11 coordinate system conversion matrix, compare the radar elevation command angle El_rd_ctr with the radar beam elevation angle El_rd, when the difference value deltaEl=(El_rd_ctr-El_rd) exceeds the second angle threshold 1°, adjust the radar beam elevation angle by the wave control module, when the difference value is less than the second angle threshold 1°, do not adjust the radar beam elevation angle.

[0103] In strip SAR mode:

[0104] S21, real-time receive the inertial navigation data on the aircraft 429 bus, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C and other data;

[0105] S22, real-time receive the imaging track angle Ang_trace_SARctrl on the control bus.

[0106] S23, calculate the geographic azimuth command angle Az_geo_ctr with the image track angle Ang_trace_SARctrl, calculate the geographic azimuth command angle Az_geo_ctr for the right side view direction imaging according to formula 12, calculate the geographic azimuth command angle Az_geo_ctr for the left side view direction imaging according to formula 13, and use the inertial navigation height H ins , the imaging area height H sar , refer to formula 14 to real-time solve the radar antenna beam geographic elevation command angle El_geo_ctr.

[0107] Az_geo_ctrl=Ang_trace_SARctrl+90…Equation 12

[0108] Az_geo_ctrl=Ang_trace_SARctrl-90…Equation 13

[0109]

[0110] S24, the geographical azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr are changed into the radar azimuth initial instruction angle Az_rd_ctr0 and the radar elevation initial instruction angle El_rd_ctr0 through the coordinate system conversion matrix of formula 11.

[0111] S25, the right side view direction is imaged, and the radar antenna azimuth mechanical angle is controlled to 90° in the radar system through the motor servo, the left side view direction is imaged, and the radar antenna azimuth mechanical angle is controlled to -90° in the radar system through the motor servo, the radar azimuth initial instruction angle Az_rd_ctr0 is compared with the radar mechanical azimuth angle Az_serv, and the wave control module adjusts the initial direction of the electric wave beam according to the difference delta_Az=Az_rd_ctr0-Az_serv.

[0112] Az_rd_ctr0-Az_serv.

[0113] S26, according to the time sequence relationship that the nth aperture frame Ap_frame(n) pulse moment is aligned with the mth processing frame pulse Prc_frame(m), the processing frame mapping division in the aperture frame time is completed, the aperture frame period T and the processing frame period t are in the proportional relationship T=k*t, wherein k is the ratio of the aperture frame period to the processing frame period, the mapping relationship between the processing frame and the aperture frame is completed, the mth processing frame corresponds to the start of the nth aperture frame, and the m+k-1th processing frame corresponds to the end of the nth aperture frame, Ap_frame(n)->[prc_frame(m) prc_frame(m+k-1)].

[0114] S27, for the first to nth imaging aperture, the geographical azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr are calculated in real time according to the processing frame period and with reference to formulas 12-14, the geographical azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr are changed into the radar azimuth instruction angle Az_rd_ctr and the radar elevation instruction angle El_rd_ctr through the coordinate system conversion matrix of formula 11, when the side view direction changes (the left side imaging changes to the right side imaging or the right side imaging changes to the left side imaging), the radar antenna azimuth mechanical angle is controlled to 90° or -90° in the radar system through the motor servo, the radar azimuth instruction angle Az_rd_ctr is compared with the radar azimuth angle Az_rd, and the wave control module adjusts the azimuth angle of the electric wave beam according to the difference deltaAz=Az_rd_ctr-Az_rd.

[0115] S28, for the first ~ n imaging aperture, according to the processing frame period, referring to formula 12~formula 14, real-time calculation of geographical system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr, the geographical system azimuth command angle Az_geo_ctr and elevation command angle El_geo_ctr is changed into radar system azimuth command angle Az_rd_ctr and elevation command angle El_rd_ctr through formula 11 coordinate system conversion matrix, the radar system elevation command angle El_rd_ctr and radar system elevation angle El_rd are compared, when the difference deltaEl=(El_rd_ctr-El_rd) exceeds the third angle threshold 1°, the wave control module is used to adjust the electric wave beam elevation angle, when the difference is less than the third angle threshold 1°, no adjustment is made to the electric wave beam elevation angle.

[0116] Figure 3 The effect diagram of the beam control of the spotlight SAR mode is shown in Figure 9, from which it can be seen that the antenna azimuth beam at different positions on the flight path at the same aperture time can be well focused on the imaging center region, Figure 4 The effect diagram of the beam control of the strip SAR mode is shown in Figure 10, from which it can be seen that the radar antenna azimuth beam electric axis at different positions on the flight path at the same aperture time can be well orthogonal to the imaging track angle.

[0117] So far, the technical solution of the present application has been described in combination with the preferred embodiments shown in the drawings, and those skilled in the art should understand that the protection scope of the present application is obviously not limited to these specific embodiments, and those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A method for beam control in SAR mode of an airborne phase-scanned radar, characterized in that, For the beamforming SAR mode, comprising: S11, receiving inertial navigation data in real time, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C; S12, calculating the azimuth and elevation command angles of the radar antenna beam using inertial navigation longitude Lon, latitude Lat, height H, and the longitude lon, latitude Lat, height H of the imaging area ins ins ins sar sar sar data​​​​​ S13, changing the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr into the radar system azimuth initial command angle Az_rd_ctr0 and the radar system elevation initial command angle El_rd_ctr0 through the coordinate system conversion matrix; S14, comparing the radar system azimuth initial command angle Az_rd_ctr0 with the radar system mechanical azimuth angle Az_serv, and the servo controls the radar antenna through the motor according to the difference, to make the initial adjustment of the mechanical azimuth angle, and comparing the radar system elevation initial command angle El_rd_ctr0 with the electric beam elevation angle El_rd, to make the initial control of the electric beam elevation direction by the wave control module according to the difference; S15, according to the time sequence relationship that the n aperture frame Ap_frame(n) pulse moment is aligned with the m processing frame pulse Prc_frame(m), mapping and dividing the processing frame in the aperture frame time, wherein the m processing frame corresponds to the n aperture frame start, and the m+k-1 processing frame corresponds to the n aperture frame end, and k is the ratio of the aperture frame period to the processing frame period; S16, for the 1~n imaging aperture, real-time calculating the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr according to the processing frame period, changing the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr into the radar system azimuth command angle Az_rd_ctr and the radar system elevation command angle El_rd_ctr through the coordinate system conversion matrix, comparing the radar system azimuth command angle Az_rd_ctr with the radar system azimuth angle Az_rd, and the servo controls the radar antenna through the motor to make the coarse adjustment of the mechanical azimuth angle when the difference exceeds the first angle threshold, and not making the adjustment of the mechanical azimuth angle when the difference is less than the first angle threshold 30° limit, and the wave control module makes the fine adjustment of the electric beam azimuth angle; S17, for the 1~n imaging aperture, real-time calculating the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr according to the processing frame period, changing the geographic azimuth command angle Az_geo_ctr and the elevation command angle El_geo_ctr into the radar system azimuth command angle Az_rd_ctr and the radar system elevation command angle El_rd_ctr through the coordinate system conversion matrix, comparing the radar system elevation command angle El_rd_ctr with the electric beam elevation angle El_rd, and the wave control module makes the adjustment of the electric beam elevation angle when the difference exceeds the second angle threshold, and not making the adjustment of the electric beam elevation angle when the difference is less than the second angle threshold.

2. The airborne synthetic aperture radar (SAR) mode beam control method according to claim 1, wherein: In S1, the geographic azimuth Az_geo_ctr and the elevation El_geo_ctr of the radar antenna beam are calculated in real time using the inertial navigation longitude Lon ins , latitude Lat ins , altitude H ins , and the longitude lon sar , latitude Lat sar , altitude H sar of the imaging area, specifically as follows: Detx = (N1 + H sar ) cos(Lat sar ) cos(Lon sar ) - (N2 + H ins ) cos(lat sar ) cos(lon sar ); Dety = (N1 + H sar ) cos(Lat sar ) sin(Lon sar ) - (N2 + H ins ) cos(lat sar ) sin(lon sar ); Wayp x = -Detx * sin(Lat ins ) cos(Lon ins ) - Dety * sin(Lat ins )sin(Lon ins )+Detz*cos(Lat ins ) Wayp y = -Detx * sin(Lon ins ) + Dety * cos(Lon ins ) Wayp z = Detx * cos(Lat ins )cos(Lon ins )+Dety* cos(Lat ins )sin(Lon ins )+Detz*sin(Lat ins ); 3. The airborne synthetic aperture radar (SAR) mode beam control method according to claim 2, wherein: R a is the Earth's semi-major axis; R b is the earth's semi-minor axis; N1, N2, Detx, Dety, Detz, Wayp x , Wayp y , Wayp z are intermediate computational quantities.

4. The airborne synthetic aperture radar (SAR) mode beam control method according to claim 3, wherein: In S13, the coordinate system conversion matrix is ​ In S16, the first angle threshold is 30°.

5. The airborne synthetic aperture radar (SAR) mode beam control method according to claim 4, characterized in that, In S17, the second angle threshold is 1°.

6. The airborne machine phase-scan radar (SAR) mode beam steering method of claim 5, wherein, For strip SAR mode, the method comprises: S21, receiving inertial navigation data in real time, including inertial navigation longitude Lon ins , latitude Lat ins , height H ins , roll γ, pitch θ, heading C; S22, receiving the imaging track angle Az_geo_SARctrl in real time; S23, calculate the geographic azimuth command angle Az_geo_ctr with the like track angle Ang_trace_SARctrl, and use the inertial navigation height H ins , the imaging area height H sar , calculate the radar antenna beam geographic elevation command angle El_geo_ctr in real time; S24, converting the geographic azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr into the radar azimuth initial instruction angle Az_rd_ctr0 and the radar elevation initial instruction angle El_rd_ctr0 through a coordinate system conversion matrix; S25, imaging the right side view direction, and serving the radar antenna azimuth mechanical angle to the radar system 90° position through motor control; imaging the left side view direction, and serving the radar antenna azimuth mechanical angle to the radar system -90° position through motor control; comparing the radar azimuth initial instruction angle Az_rd_ctr0 with the radar mechanical azimuth angle Az_serv, and performing initial adjustment of the electric beam azimuth pointing according to the difference value; comparing the radar elevation initial instruction angle El_rd_ctr0 with the electric beam elevation angle El_bk, and performing initial control of the electric beam elevation pointing according to the difference value; S26, according to the time sequence relationship that the n aperture frame Ap_frame(n) pulse moment is aligned with the m processing frame pulse Prc_frame(m), mapping and dividing the processing frames in the aperture frame time, wherein the first m processing frame corresponds to the n aperture frame start, and the m+k-1 processing frame corresponds to the n aperture frame end, k is the ratio of the aperture frame period to the processing frame period; S27, for the first to n imaging apertures, calculating the geographic azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr in real time according to the processing frame period, converting the geographic azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr into the radar azimuth instruction angle Az_rd_ctr and the radar elevation instruction angle El_rd_ctr through a coordinate system conversion matrix, and comparing the radar azimuth instruction angle Az_rd_ctr with the radar azimuth angle Az_rd to adjust the electric beam azimuth angle according to the difference value; S28, for the first to n imaging apertures, calculating the geographic azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr in real time according to the processing frame period, converting the geographic azimuth instruction angle Az_geo_ctr and the elevation instruction angle El_geo_ctr into the radar azimuth instruction angle Az_rd_ctr and the radar elevation instruction angle El_rd_ctr through a coordinate system conversion matrix, comparing the radar elevation instruction angle El_rd_ctr with the radar elevation angle El_rd, and adjusting the electric beam elevation angle when the difference value exceeds the third angle threshold, and not adjusting the electric beam elevation angle when the difference value is less than the third angle threshold.

7. The airborne synthetic aperture radar (SAR) mode beam steering method according to claim 6, wherein, In S23, the geographic azimuth command angle Az_geo_ctr is calculated based on the image track angle Ang_trace_SARctrl: For imaging in the right-looking direction, Az_geo_ctrl = Ang_trace_SARctrl + 90; For imaging in the left-looking direction, Az_geo_ctrl = Ang_trace_SARctrl - 90.

8. The airborne synthetic aperture radar (SAR) mode beam steering method according to claim 7, wherein, In S23, the radar antenna beam geographic elevation command angle El_geo_ctr is calculated based on the image track angle Ang_trace_SARctrl, and the calculation is as follows:

9. The airborne synthetic aperture radar (SAR) mode beam steering method according to claim 8, wherein, In S24, the coordinate system conversion matrix is 10. The airborne synthetic aperture radar (SAR) mode beam steering method according to claim 9, wherein, The third angle threshold is 1°.

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