CN111505592A - Method for measuring roll angle of satellite-borne radar by using base view differential interference - Google Patents

Method for measuring roll angle of satellite-borne radar by using base view differential interference Download PDF

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CN111505592A
CN111505592A CN202010338290.6A CN202010338290A CN111505592A CN 111505592 A CN111505592 A CN 111505592A CN 202010338290 A CN202010338290 A CN 202010338290A CN 111505592 A CN111505592 A CN 111505592A
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interference
antenna
echo
roll angle
echoes
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杨双宝
徐熙煜
康雪艳
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National Space Science Center of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/0218—Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/288—Coherent receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

The invention discloses a method for measuring a roll angle of a satellite-borne radar by using base view differential interference, which comprises the following steps: to left antenna A of satellite-borne radarLIntermediate antenna AOAnd a right antenna ARCarrying out azimuth-range compression processing on the received echoes to obtain pulse echoes after the compression processing of the three antennas; performing interference processing on the compressed pulse echoes to obtain two groups of interference echoes; performing azimuth-distance two-dimensional smoothing on the two groups of interference echoes respectively; extracting interference phase from the smoothed interference echo and calculatingDifferential interference phase; and estimating the roll angle by utilizing a least square algorithm based on a plurality of differential interference phases. The method of the invention does not need to establish a ground calibration field or a specific reference target; compared with the existing roll angle measuring method, the roll angle measuring method is simpler to operate, has fewer error sources and is higher in precision.

Description

Method for measuring roll angle of satellite-borne radar by using base view differential interference
Technical Field
The invention relates to the technical field of space-based radars, in particular to a method for measuring and calibrating a roll angle when a high-precision interference radar is measured over the ocean, and particularly relates to a method for measuring the roll angle of a satellite-borne radar by using bottom view differential interference.
Background
The existing international (bottom view) interferometric synthetic aperture radar altimeter and the small incident angle interferometric imaging radar altimeter at home and abroad (under development) comprise:
(1) a bottom view synthetic aperture radar altimeter, such as the European Bureau on-orbit radar altimeter Cryosat-2. Cryosat-2 is a typical dual antenna architecture, single-voyage short baseline bottom view interferometric synthetic aperture radar. The working modes of the device comprise a real aperture altimeter mode, a synthetic aperture altimeter mode and a bottom view interference mode. The bottom view interference mode is mainly used for measuring the terrain gradient of the ice rack in the north and south.
Since the terrain slope measurement of the south and north pole iceracks depends on the bottom view interferometry phase, and the interferometry phase is influenced by the base line roll angle, the base line roll angle must be accurately known when the slope terrain of the iceracks is observed. The roll angle measurement of the method depends on the star sensor on the star and the calibration of the star sensor.
The Cryosat-2 calibrates the roll angle measured by the star sensor by using a double-antenna base view interferometry phase over a specific sea area. This method requires knowledge of sea currents and the natural terrain slope variations, as it does not eliminate the effect of sea terrain slope errors on roll angle determination. Therefore, the accuracy of the roll angle is limited, and can only reach 0.1mrad, which cannot be improved any more.
(2) Space-based (space-borne) small-incidence-angle interferometric imaging radar altimeter. The method comprises a skunk No. two imaging altimeter which is transmitted in China, a new generation of marine dynamic imaging altimeter which is still planned, and a SWOT interference imaging altimeter which is planned abroad. The small-incidence-angle interference imaging altimeter has the main advantage that compared with a bottom-view radar altimeter, the observation swath of the small-incidence-angle interference imaging altimeter can be improved by about 8 times on the same track height, so that two-dimensional sea surface height imaging is realized, and the small-incidence-angle interference imaging altimeter has important significance on ocean dynamics.
The interference imaging radar mainly depends on a calibration field or a fixed reference target to realize the calibration of the roll angle. The calibration reference is the view angle of the calibration field or fixed reference target relative to the baseline center. When calculating the viewing angle geometrically, it is necessary to know the exact relative geometric position, and the exact time. The realization method is complex, has a plurality of influence factors and is easy to generate measurement errors.
Disclosure of Invention
The invention aims to overcome the defects that the conventional roll angle calibration technology of the interference radar cannot realize higher accuracy in a short time of 1s and limits further improvement of the interference measurement high accuracy, and provides a method for realizing the roll angle measurement of a satellite-borne radar by using base view differential interference, which can further improve the roll angle measurement accuracy and can reach the urad magnitude under the average condition of 1 s.
In order to achieve the above object, the present invention provides a method for measuring a roll angle of a satellite-borne radar by using bottom view differential interference, the method comprising:
to left antenna A of satellite-borne radarLIntermediate antenna AOAnd a right antenna ARCarrying out azimuth-range compression processing on the received echoes to obtain pulse echoes after the compression processing of the three antennas;
performing interference processing on the compressed pulse echoes to obtain two interference echoes;
performing azimuth-distance two-dimensional smoothing on the two interference echoes respectively;
extracting an interference phase from the smoothed interference echo, and calculating a differential interference phase;
and estimating the roll angle by utilizing a least square algorithm based on a plurality of differential interference phases.
As an improvement of the above method, the pulse echo after compression processing is subjected to interference processing to obtain two interference echoes; the method specifically comprises the following steps:
Figure BDA0002467570300000021
Figure BDA0002467570300000022
wherein the content of the first and second substances,
Figure BDA0002467570300000023
is an antenna AOAn echo of a jth range gate of the received ith echo pulse;
Figure BDA0002467570300000024
is an antenna ALAn echo of a jth range gate of the received ith echo pulse;
Figure BDA0002467570300000025
is ARReceiving an echo of a jth range gate of an ith echo pulse by an antenna;
Figure BDA0002467570300000026
is an antenna AOAnd an antenna ALThe interference echo of the jth range gate between the ith interference echo pulse,
Figure BDA0002467570300000027
is an antenna AOAnd an antenna ARAn interference echo of a jth range gate between the ith interference echo pulse;
as an improvement of the above method, the method extracts an interference phase from a difference between the smoothed interference echoes, and calculates a differential interference phase; the method specifically comprises the following steps:
from interfering echoes
Figure BDA0002467570300000028
The interference phase extracted from
Figure BDA0002467570300000029
Comprises the following steps:
Figure BDA00024675703000000210
from interfering echoes
Figure BDA0002467570300000031
The interference phase extracted from
Figure BDA0002467570300000032
Comprises the following steps:
Figure BDA0002467570300000033
wherein the content of the first and second substances,
Figure BDA0002467570300000034
is a phase function; n1, n2 respectively represent the number of azimuth direction pulses and the number of range gates participating in the sum average; m isijThe jth range gate for the ith echo pulse, tracking gate labeled j 0;
calculating differential interference phase
Figure BDA0002467570300000035
Figure BDA0002467570300000036
Wherein k is the electromagnetic wave number, and B is the base length, i.e. the left radar antenna ALPhase center and right radar antenna ARDistance of phase centers.
As an improvement of the above method, the roll angle is estimated by using a least square algorithm based on a plurality of differential interference phases; the method specifically comprises the following steps:
differential interference phase
Figure BDA0002467570300000037
The relationship to the roll angle χ is:
Figure BDA0002467570300000038
wherein a, b and c are system parameters, sigmahIs the root mean square height of the earth surface;
and estimating the roll angle x by utilizing a plurality of differential interference phases and a least square method.
As an improvement of the above method, the method further comprises:
with intermediate antenna AOTransmitting electromagnetic pulses towards the ground for the transmitting antenna and at a designed pulse repetition frequency PRF;
the left antenna ALIntermediate antenna AOAnd a right antenna ARSimultaneously receiving ground reflection echoes;
and (3) performing on-track distance direction compression processing on the ground reflection echo of any antenna, performing on-track tracking on the processed echo, and keeping a target echo signal locked.
As an improvement of the above method, the intermediate antenna aOAt the center of the base line, the direction of the base line is from the left antenna ALPointing to the right antenna ARAnd A isOALSub-base line and AOARThe sub-lines are symmetrical.
The invention has the advantages that:
1. the method of the invention can not only carry out high-precision calibration on the satellite sensor in any sea area within 60 degrees of south latitude and north latitude of the whole world, but also directly apply the roll angle measurement result to the sea interference radar, such as a small-incidence-angle interference imaging radar altimeter specially used for a sea satellite.
2. The method is applicable to any open sea area within 60 degrees of north and south latitude, Antarctic ice sources and ice racks, large inland lakes and other flat areas in the world, and a calibration field does not need to be established independently;
3. because the high-precision roll angle measurement value can be directly provided in the global sea area, the method of the invention is beneficial to further improving the interference measurement precision;
4. the method can realize the roll angle calibration of the satellite-borne interference radar within 1s average and with the accuracy of the urad magnitude; this is currently not possible with other measurement means;
5. the method of the invention does not need to establish a ground calibration field or a specific reference target; compared with the existing roll angle measuring method, the roll angle measuring method is simpler to operate, has fewer error sources and is higher in precision.
6. For the ocean interference radar, the method can directly provide high-precision roll angle measurement values while the satellite-borne radar performs observation tasks.
Drawings
FIG. 1 shows the interference angle φ (χ, β, σ)h) A relation diagram of a base line transverse rolling angle x and a terrain slope angle β;
FIG. 2 is a schematic diagram of a geometric observation model;
FIG. 3 shows an antenna AOA schematic of the received echoes and their tracking points;
FIG. 4 is a schematic diagram of differential interference phases and corresponding roll angles of simulated echoes;
fig. 5 is a schematic diagram of roll angle estimation and estimation error obtained using differential phase.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
Figure 1 shows the geometric relationship between the terrain slope of the target surface being observed and the baseline vector (for clarity of illustration, the angle and height scale is distorted, but does not affect the problem nature and problem description).
In FIG. 1, the radar is flying into the page perpendicular to the plane of the page, antenna AL,AO,ARAnd receiving the electromagnetic wave reflected by the ground. From the theory of interferometry, antenna A can be knownLARInterference angle phi (x, β, sigma) corresponding to phase psi of interference echoh) (phi ═ psi/(k · B), where k is the electromagnetic wave number and B is the baseline length) are the antenna baseline roll angle χ, the terrain slope angle β (parameters defined later) and the local root mean square height σhAs a function of (c). Therefore, once the echo phase and baseline roll angle are established,the base line roll angle can be solved by the mathematical relation between the terrain slope angles.
The theoretical basis of the present invention, namely a mathematical model for describing the relationship between the interference phase and the roll angle, the terrain slope angle, is described below. Based on the geometric observation model shown in fig. 2 and the geometric relationship described in fig. 1, a desired mathematical model can be established.
In fig. 2, the antenna base length B. Radar antenna AOLocated at the center of the base line, with nadir N, and radar antenna AOThe height relative to the nadir N is H, and the local earth radius of the nadir N is Re. Baseline direction self-radar antenna ALDirectional radar antenna ARAnd the direction is the same as the X-axis direction. The radar flies along the Y-axis direction with the roll angle chi being positive counterclockwise (i.e. when chi is viewed against the flying direction)>At 0, the left antenna A looks against the direction of flightLHigher than the right antenna AR). The antenna pitch angle mu, viewed against the X-axis, is positive counterclockwise (i.e. when mu is>0, the radar visual axis is forward looking). The baseline yaw angle is ζ, and counterclockwise when viewed against the Z axis (i.e., in the down-view direction) (i.e., when ζ is positive)>0, left antenna ALRear, right antenna ARPrior). The spherical coordinates of the point target T are
Figure BDA0002467570300000051
Wherein
Figure BDA0002467570300000052
Figure BDA0002467570300000053
Indicating the height of the point target T above the reference sphere. The plane of the point target is the passing point
Figure BDA0002467570300000054
Figure BDA0002467570300000055
Tangent plane of, and passing point of
Figure BDA0002467570300000056
Is cutThe angle of the plane in the cross-track direction (in the X-axis direction) is defined by the same direction as the roll angle χ, defined as the slope angle β.
The base line is perpendicular to the plane formed by the connecting line from the satellite to the nadir and the flying speed. The phase centers of the 3 antennas are respectively positioned at A in figure 1O,AL,ARIn a position, and AOALSub-base line and AOARThe two baseline lengths are equal for ease of calculation, and therefore, it is assumed that the two baseline lengths are equal. The visual axes of the 3 antennas are in the same plane and are parallel to each other. Intermediate antenna AOThe boresight is in the plane formed by the satellite-to-nadir point connecting line and the flight speed and is parallel to the satellite-to-nadir point connecting line. Antenna AOEmitting an electromagnetic pulse, AO,AL,ARAnd 3 antennas simultaneously receive radar echoes reflected by the ground. In this embodiment, the antenna feed should be separated from the baseline to minimize the effect of baseline distortion on the baseline length.
For the observation model, the interference echo phase can be obtained:
Figure BDA0002467570300000057
wherein the content of the first and second substances,
Figure BDA0002467570300000058
indicating radar antenna AOAnd a radar antenna ALThe phase of the interference echo between;
Figure BDA0002467570300000059
indicating radar antenna AOAnd a radar antenna ARK 2 pi/lambda is the wave number of the electromagnetic wave, η 1+ h/ReFor local earth curvature, σhIs the local root mean square height. According to the formula (1), differential interference can be obtained
Figure BDA0002467570300000061
In the case of χ < 0.5 °, equation (2) can be further written as
Figure BDA0002467570300000062
Wherein a, b, c are radar system related parameters.
The roll angle χ can be obtained by the formula (3). Under the condition of enough measurement samples, the least square solution is adopted, and the roll angle measurement precision D (χ) is as follows:
Figure BDA0002467570300000063
η thereincThe coherence factor for interfering echoes is typically over 0.9 for oceans and ice racks. N is the independent observation pulse number, and 9000 independent observation pulse numbers can be obtained on the scale of 2km for a radar system adopting bottom view synthetic aperture processing. Therefore, the measuring precision of the roll angle x can reach the urad magnitude.
For the measurement scheme described above, with the system parameters 800km track height, Ka band, base length 2m (base length is defined as a)L,ARThe distance between the phase centers of the two antennas), the pulse repetition frequency is 9KHz, the signal bandwidth is 320MHz as an example, and the specific technical implementation is described.
High accuracy roll angle measurements can be achieved by performing bottom view differential interferometry as follows. On the star, with AOTo transmit the antenna and transmit electromagnetic pulses toward the surface at a designed pulse repetition frequency PRF. Receiving the ground reflection echo by 3 antennas simultaneously, and recording as psi0,ΨL,ΨR(ii) a To psio(ΨLOr ΨR) And performing azimuth-range compression (or only performing range compression), performing on-orbit tracking on the processed echo, and keeping a target echo signal locked. Then the following treatment processes are carried out:
step (ii) of1) The echo waves received by the 3 antennas are compressed in the azimuth direction and the distance direction, and A is processedOThe receiving interference echo of the antenna (or one of the other two antennas) is subjected to high-precision re-tracking processing (in the case of a short baseline, the A can be directly trackedOThe antenna receives the echo). The jth range gate of the ith echo pulse is recorded as mijThe tracking gate is labeled j0 (see tracking gate in FIG. 3), and outputs a corresponding root mean square height σ of the earth's surfaceh。
Step 2) interference processing is carried out on the pulse echo after compression processing to obtain
Figure BDA0002467570300000064
Figure BDA0002467570300000065
Wherein the content of the first and second substances,
Figure BDA0002467570300000071
is AOReceiving an echo of a jth range gate of an ith echo pulse by an antenna;
Figure BDA0002467570300000072
is ALReceiving an echo of a jth range gate of an ith echo pulse by an antenna;
Figure BDA0002467570300000073
is ARReceiving an echo of a jth range gate of an ith echo pulse by an antenna;
Figure BDA0002467570300000074
is AOAntenna and ALThe echo of the jth range gate of the ith interference echo pulse between the antennas,
Figure BDA0002467570300000075
is AOAntenna and ARThe echo of the jth range gate of the ith interfering echo pulse between the antennas.
Step 3) are right
Figure BDA0002467570300000076
And
Figure BDA0002467570300000077
and performing azimuth-distance two-dimensional smoothing.
Step 4), extracting interference phases:
Figure BDA0002467570300000078
Figure BDA0002467570300000079
wherein the content of the first and second substances,
Figure BDA00024675703000000714
is a phase function; n1, n2 represent the number of azimuth pulses and the number of range gates, respectively, participating in the sum-average.
Step 5) according to the formula (3), aiming at the ith group of echoes (A)O,AL,ARThe ith echo received by 3 antennas is a group) to obtain differential interference phases:
Figure BDA00024675703000000710
Figure BDA00024675703000000711
see phase given in fig. 4.
Step 6) measuring multiple groups of interference phases
Figure BDA00024675703000000712
And estimating the roll angle x and the radar system parameters a, b and c by using a least square algorithm. See the roll angle estimate given in fig. 5.
In view of the fact that no satellite-borne base view differential interference observation radar system exists at present, simulation experiments can be designed for verification. In the simulation, 7 roll angles were set in the cross-track direction. The simulation parameters are shown in table 1 below.
TABLE 1 simulation parameters
Figure BDA00024675703000000713
Figure BDA0002467570300000081
The simulation is performed according to the above parameters, and the simulation results are shown in fig. 3, 4, and 5. FIG. 3 is AOThe echo received by the antenna and the tracking point thereof. Fig. 4 shows the differential interference phase corresponding to the roll angle. FIG. 5 is a graph of the roll angle estimated using differential interference phase and its difference from a simulated set point.
The innovation points of the invention are as follows:
1. and modeling the echoes received by the radar antennas participating in the ground-view differential interference processing on each antenna echo under the same reference system, thereby obtaining a ground-view interference radar echo model and a ground-view differential interference phase model. And under a certain condition, decoupling the influence of the roll angle and the gradient of the target terrain on the interference phase. The method is an innovative point of the invention and a theoretical basis of the invention.
2. The method is a theoretical innovation and a technical innovation of the invention, wherein an interference phase equation set is constructed by adopting symmetrical double baselines, and the target terrain slope and the roll angle are separated from an interference phase.
3. The advantage of measuring the roll angle by using the bottom view symmetrical base line and the three receiving channels (as shown in the attached drawing) on the open sea surface (/ flat ice land, large inland lake and other even flat terrains) is that the error caused by the gradient of the target terrain and the error caused by the root mean square height fluctuation of the target terrain can be eliminated, thereby obtaining the accurate roll angle.
4. The invention discloses a bottom view differential interference synthetic aperture echo processing flow, which is the 4 th innovation point of the invention.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. A method for achieving roll angle determination of an on-board radar using bottom view differential interference, the method comprising:
to left antenna A of satellite-borne radarLIntermediate antenna AOAnd a right antenna ARCarrying out azimuth-range compression processing on the received echoes to obtain pulse echoes after the compression processing of the three antennas;
performing interference processing on the compressed pulse echoes to obtain two interference echoes;
performing azimuth-distance two-dimensional smoothing on the two interference echoes respectively;
extracting an interference phase from the smoothed interference echo, and calculating a differential interference phase;
and estimating the roll angle by utilizing a least square algorithm based on a plurality of differential interference phases.
2. The method for measuring the roll angle of the spaceborne radar by utilizing the base-view differential interference according to the claim 1, wherein the compressed pulse echo is subjected to interference processing to obtain two interference echoes; the method specifically comprises the following steps:
Figure FDA0002467570290000011
Figure FDA0002467570290000012
wherein the content of the first and second substances,
Figure FDA0002467570290000013
is an antenna AOReceivingThe echo of the jth range gate of the ith echo pulse of (1);
Figure FDA0002467570290000014
is an antenna ALAn echo of a jth range gate of the received ith echo pulse;
Figure FDA0002467570290000015
is ARReceiving an echo of a jth range gate of an ith echo pulse by an antenna;
Figure FDA0002467570290000016
is an antenna AOAnd an antenna ALThe interference echo of the jth range gate between the ith interference echo pulse,
Figure FDA0002467570290000017
is an antenna AOAnd an antenna ARThe interference echo of the jth range gate of the ith interference echo pulse.
3. The method for realizing the roll angle measurement of the satellite-borne radar by using the bottom-view differential interference according to claim 2, wherein the interference phase is extracted from the smoothed interference echo, and the differential interference phase is calculated; the method specifically comprises the following steps:
from interfering echoes
Figure FDA0002467570290000018
The interference phase extracted from
Figure FDA0002467570290000019
Comprises the following steps:
Figure FDA00024675702900000110
from interfering echoes
Figure FDA00024675702900000111
The interference phase extracted from
Figure FDA00024675702900000112
Comprises the following steps:
Figure FDA00024675702900000113
wherein the content of the first and second substances,
Figure FDA0002467570290000021
is a phase function; n1, n2 respectively represent the number of azimuth direction pulses and the number of range gates participating in the sum average; m isijThe jth range gate for the ith echo pulse, tracking gate labeled j 0;
calculating differential interference phase
Figure FDA0002467570290000022
Figure FDA0002467570290000023
Wherein k is the electromagnetic wave number, and B is the base length, i.e. the left radar antenna ALPhase center and right radar antenna ARDistance of phase centers.
4. The method for realizing the roll angle measurement of the satellite-borne radar by using the base view differential interference according to claim 3, wherein the roll angle is estimated by using a least square algorithm based on a plurality of differential interference phases; the method specifically comprises the following steps:
differential interference phase
Figure FDA0002467570290000024
The relationship to the roll angle χ is:
Figure FDA0002467570290000025
wherein a, b and c are system parameters, sigmahIs the root mean square height of the earth surface;
and estimating the roll angle x by utilizing a plurality of differential interference phases and a least square method.
5. The method for realizing roll angle measurement of a satellite-borne radar by using bottom view differential interference according to any one of claims 1 to 4, wherein the method further comprises the following steps:
with intermediate antenna AOTransmitting electromagnetic pulses towards the ground for the transmitting antenna and at a designed pulse repetition frequency PRF;
the left antenna ALIntermediate antenna AOAnd a right antenna ARSimultaneously receiving ground reflection echoes;
and (3) performing on-track distance direction compression processing on the ground reflection echo of any antenna, performing on-track tracking on the processed echo, and keeping a target echo signal locked.
6. The method for realizing the roll angle measurement of the spaceborne radar by using the bottom-view differential interference as claimed in claim 5, wherein the intermediate antenna AOAt the center of the base line, the direction of the base line is from the left antenna ALPointing to the right antenna ARAnd A isOALSub-base line and AOARThe sub-lines are symmetrical.
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