JPH07159529A - Interference type composite-aperture radar oscillation correcting device - Google Patents

Abstract

PURPOSE:To correct image distortions caused by the oscillation of a flying object, using an interference type composite-aperture radar image processor capable of obtaining highly accurate topographical information using two antennas. CONSTITUTION:Integral time 303 is calculated by an integral time calculating portion 31 using position/speed data 108. An accumulating portion 34 cumulates reproduced oscillation data 304 using the integral time 303, to originate accumulative data 305. Using the accumulative data 305 and the position/speed data 108, oscillation correction data 306 is obtained by an oscillation correction calculating portion 35. An oscillation correcting portion 38 takes the difference between the reproduced oscillation correction data 311 and interference data 312 and outputs this difference as correction interference data 113.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference type synthetic aperture radar motion compensator, and more particularly to an interference type synthetic aperture radar motion compensator mounted on an aircraft.

[0002]

2. Description of the Related Art An interferometric synthetic aperture radar (terrain mapping radar) capable of obtaining topographical information with high accuracy by using two antennas is disclosed in, for example, Japanese Patent Laid-Open No. 63-262578.
As shown in the publication, it was mounted on a satellite with stable orbit.

Since around 1990, development experiments of a processing device for an interferometric synthetic aperture radar mounted on an aircraft have been conducted mainly in overseas countries, especially in the United States ((Reference) Howard).
A. Zebker, “The TOPSAR Inte
rferometricRadar Topograp
hic Mapping Instrument ”, I
EEE Trans. Geosci. Remote
Sensing, vol. 30, pp. 933-
940, Sep. 1992).

FIG. 6 shows a conceptual diagram of an interferometric synthetic aperture radar. Radio waves are radiated toward the ground from two antennas 1 and 2 attached to a flying object, and reflected waves from the ground surface are received. When the well-known synthetic aperture radar image reproduction processing (Hisa Yonekawa et al. "Digital image reproduction of aircraft SAR" Chiba University Faculty of Engineering research report, Volume 35, No. 2) is performed on the data received by each antenna, X, y in FIG.
Image data (complex format) for the direction is obtained. Here, only the y direction is considered for simplification.

The position y of the image obtained by the antenna 1
The image data of _n is C ₁ , and the image data of the position y _n of the image obtained by the antenna 2 is C ₂ . The phase difference θ between these two data has the relationship shown in FIG. 8 as is well known, and can be calculated by the following equation (1).

Θ = arg (C ₁ · C ₂ ^* ) ... (1) −π ≦ θ ≦ π [*: complex conjugate, arg (C )] Also, the phase difference θ _{h = 0} of the plane at the point y _n can be calculated by the following equation (2).

Θ _{h = 0} = 2d cos β = 2d · h / (h ² + y _n ² ) ^1/2 (2) d: antenna spacing h: antenna altitude (−π ≦ θ _h ≦ π) expression by taking the difference between theta _{h = 0} in (1) of theta and formula (2) (phase difference elimination processing of the plane), altitude Z (y in y _n
The phase θ _c (−π ≦ θ _c ≦ π) according to n) is obtained. In the present specification, θ _c is referred to as interference data.

Using the interference data θ _c , the altitude h at y _n =
As is well known, Z (y _n ) can be calculated by the following equation (3), where l is the distance from the antenna 2 to the target.

H = Z (y _n ) = H−1 · cos θ _c ..... (3) The altitude h of the altitude h at the location y _n observed using the procedure described above. You can get the data.

[0010]

However, if the processing device of an interferometric synthetic aperture radar originally developed for a satellite having a stable orbit is used to process data obtained from an aircraft with unstable movement. , Due to the motion of the flying object as shown in FIG. 7, the altitude h shown in the equation (3) is h = H + ΔH−1 · cos (θ + Δθ) ..... (4) It will be represented by. Therefore, unless ΔH and Δθ are detected and the interference data is corrected, highly accurate topographical information cannot be obtained. It is an object of the present invention to provide distortion-free topographical information by removing distortion of the topographical information caused by the motion of a flying object based on ΔH and Δθ representing the motion.

[0011]

Means for solving the above-mentioned problems are provided by the present invention in which radio waves are radiated toward the ground from an interference type synthetic aperture radar mounted on a flying object, A signal obtained by receiving a reflected wave by the interference-type synthetic aperture radar is provided in an interference-type synthetic-aperture radar image processing device that generates an image representing a topographical change, and the image distortion due to the motion of the flying object is corrected. A device for correction,
A first recording / reproducing unit for storing and reproducing the motion data of the flying object output from the motion detection unit provided in the interference type synthetic aperture radar, and a position / speed detection unit provided in the interference type synthetic aperture radar. The integration time calculation unit that calculates the integration time of the SAR reproduction process based on the position / velocity data of the flying object output from the recording medium, and the fluctuation data that is the output data from the first recording / reproduction unit, An integrating unit that integrates based on an integration time of output data of the unit, a shake correction data calculating unit that calculates shake correction data based on the integrated data of the output data from the integrating unit and the position / speed data, and the shake. A second recording / reproducing unit that records and reproduces the shake correction data output from the correction data calculating unit, and interference data from the interference processing unit provided in the interference-type synthetic aperture radar is recorded. The difference between the generated third recording / reproducing unit, the interference data output from the third recording / reproducing unit, and the shake correction data output from the second recording / reproducing unit is calculated, and the difference data is obtained. An interference type synthetic aperture radar wobbling correction device comprising: a wobbling correction unit that outputs as correction interference data.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an interference type synthetic aperture radar motion compensator according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an interferometric synthetic aperture radar image processing apparatus equipped with the motion compensation apparatus of the present invention. The control unit 105 controls the transmission / reception units 3 and 5 by the control signal 105. Control signal 105 from control unit 4
The transmission / reception unit 3 and the transmission / reception unit 5 controlled by radiate a radio wave to the ground by switching the antennas 1 and 2 and receive a reflected wave from the ground. Reference numeral 101 denotes a transmitted wave transmitted from the antenna 1, 103 denotes a received wave of the antenna 1, 102 denotes a transmitted wave transmitted from the antenna 2, and 104 denotes a received wave of the antenna 2. The transmission / reception units 3 and 5 receive the received waves 103 and 104.
Respectively to generate received data 106 and 107. The received data 106 and 107 are output to the SAR image reproduction processing units 8 and 9, respectively. The position / velocity detector 6 detects the position and velocity of the flying object. The position and speed data are supplied to the SAR image reproduction processing units 8 and 9, the interference processing unit 10, and the motion compensation processing unit 11 as position / speed data 108. The SAR image reproduction processing units 8 and 9
Reception data 106, 107 and position / speed data 108
To process the complex SAR image reproduction data 110, 1
11 is generated. SAR image reproduction data 110 and 11
1 corresponds to C ₁ and C ₂ ^* in the above formula (1), respectively. The interference processing unit 10 uses the SAR image reproduction data 11
The 0, 111 and position / velocity data 108 are processed to generate complex interference data 112. Interference data 112
Corresponds to θ _c described above. The motion detector 7 detects a roll, pitch, and yaw direction fluctuation angle of a flying object equipped with the device of FIG. The fluctuation angles in the roll, pitch, and yaw directions are output to the shaking correction processing unit 11 as shaking data 109. The motion compensation processing unit 11 uses the position / speed data 10
8, processing the motion data 109 and the interference data 112,
The corrected interference data 113 is generated.

FIG. 2 is a block diagram showing the configuration of the interference processing unit 10 in FIG. The phase difference calculation unit 21 uses the SAR
The phase difference between the image reproduction data 110 and 111 is calculated and output as the phase difference data 201. Plane phase difference calculator 2
3 calculates a plane phase difference using the phase / velocity data 108 and outputs it as plane phase difference data 202. The plane phase difference data 202 is represented by the above-mentioned equation (2).
Corresponds to θ _{h = 0} . The plane phase difference removing unit 22 calculates the difference between the phase difference data 201 and the plane phase difference data 202 and outputs interference data 112.

FIG. 3 is a block diagram showing details of the processing of the motion compensation processing unit 11 in FIG. Integration time calculation unit 3
1 uses the position / velocity data 108 to calculate the integration time of data in the well-known SAR image reproduction processing, and outputs it as the integration time 303. Upset data 109
Is stored in the recording / playback unit 32. The recorded contents of the recording / reproducing unit 32 are cleared when reproduced. Recording / playback unit 32
Outputs the recorded data amount as a control signal 302 to the motion compensation control unit 33. When the data amount represented by the control signal 302 exceeds the reference value, the motion compensation control unit 33 outputs the reproduction control signal 301, and the motion data 109 recorded in the recording / reproducing unit 32 is output as the motion data 304. It The integration unit 34 uses the roll variation amount of the machine body and the integration time 303 of the motion data 304 to perform integration processing as shown in FIG. 4, and outputs the integrated motion data 305. FIG. 4A shows a time change of the roll fluctuation amount (= shaking amount) represented by the shaking data 304. Also, FIG.
(B) is an integration processing unit 3 for calculating the fluctuation amount shown in (a) of the same figure.
An example of the integrated shaking data 305 integrated in 4 is shown. The shaking correction data calculation unit 35 uses the integrated shaking data 305 and the position / speed data 108 to calculate the fluctuation amount φ of the interference data due to the fluctuation in the roll direction of the flying object as shown in FIG. Calculate using.

Φ (rad) = (2π / λ) {(l ₂ '−l ₁ ′) − (l ₂ −l ₁ )} (5) where l ₂ = (H ² + y ² ) ^1/2 l ₁ = {(H + d) ² + y ² } ^1/2 l ₂ ′ = {(H + m + d−y ₂ ′) ² + (x + y−x ₂ ′) ² } ^1/2 l ₁ ′ = {( H + m + d−y ₁ ′) ² + (x + y−x ₁ ′) ² } ^1/2 x ₂ ′ = x · cos θ− (m + d) sin θ y ₂ ′ = x · sin θ− (m + d) cos θ x ₁ ′ = x · cos θ−msin θ y ₁ ′ = x · sin θ−d cos θ θ: integrated shake data (roll direction) The result obtained by calculation by the equation (5) is the shake correction data 30.
It is output as 6 and is stored in the recording / reproducing unit 36. This data amount is used as the control signal 310 for the motion compensation control unit 33.
Output to. The interference data 112 is stored in the recording / playback unit 37. The amount of data stored in the recording / playback unit 37 is output to the motion compensation control unit 33 as a control signal 308.
The recording / playback units 36 and 38 clear the playback data each time playback is performed. When the data amounts of the recording / reproducing units 36 and 37 indicated by the control signals 310 and 308 both exceed the reference amount, the motion compensation control unit 33 reproduces the reproduction control signal 30.
9, 307 are output to the recording / reproducing units 36, 37, respectively, and are reproduced and output as the motion correction processing data 311 and the interference data 312. The motion correction unit 38 uses the equation (6)
The interference data 312 (θ _c ) and the shake correction data 3
Calculates 11 (phi) the difference between _{θ T = θ c -φ ························ (} 6), corrected interference theta _T The data 113 is output.

[0017]

As described above, by applying the present invention to the interferometric synthetic aperture radar image processing apparatus, the motion of the flying object can be corrected. The terrain information obtained will be accurate. The present invention has such an effect. Further, to apply the present invention, the SAR image reproduction processing units 8 and 9 and the interference processing unit 10 in the conventional interference type synthetic aperture radar image processing apparatus.
Therefore, according to the present invention, an improved interferometric synthetic aperture radar image processing device capable of providing accurate topographical information can be obtained by simply changing the design of the conventional device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an interferometric synthetic aperture radar image processing apparatus including an interferometric synthetic aperture radar motion compensation apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an interference processing unit in the apparatus of FIG.

FIG. 3 is a block diagram showing the configuration of a motion compensation processing unit that is an embodiment of the present invention in the apparatus of FIG.

4 is a diagram showing a concept of integration processing performed by an integration unit in the motion compensation processing unit of FIG.

FIG. 5 is a diagram showing the influence of roll fluctuations on interference data.

FIG. 6 is a diagram showing a basic concept of an interferometric synthetic aperture radar.

FIG. 7 is a conceptual diagram showing the influence of motion of a flying object on altitude accuracy.

FIG. 8 is a diagram showing a relationship between image data C ₁ and C ₂ and a phase difference θ between these two data.

[Explanation of symbols]

 1, 2 Antenna section 3, 5 Transmission / reception section 4 Control section 6 Position / speed detection section 7 Motion detection section 8, 9 SAR image reproduction processing section 10 Interference processing section 21 Phase difference calculation section 22 Planar phase difference removal section 23 Planar Phase difference calculation unit 31 Integration time calculation unit 32, 36, 37 Recording / playback unit 33 Motion correction control unit 34 Integration unit 35 Motion correction data calculation unit 38 Motion correction unit

Claims (2)

[Claims] 1. A signal obtained by radiating radio waves from an interferometric synthetic aperture radar mounted on a flying object toward the ground and receiving a reflected wave from the ground by the interferometric synthetic aperture radar, A shake detection unit provided in an interferometric synthetic aperture radar, which is provided in an interferometric synthetic aperture radar image processing device and corrects image distortion due to the motion of the flying object. Based on the first recording / reproducing unit that stores and reproduces the motion data of the flying object output from, and the position / speed data of the flying object output from the position / speed detecting unit provided in the interferometric synthetic aperture radar An integration time calculation unit for calculating the integration time of the SAR reproduction processing, and integration for integrating the fluctuation data which is the output data from the first recording / reproduction unit based on the integration time of the output data of the integration time calculation unit. A motion compensation data calculation unit that calculates motion compensation data based on the integrated data of the output data from the accumulator and the position / speed data, and the motion compensation data output from the motion compensation data calculation unit. From the second recording / reproducing unit for reproducing, the third recording / reproducing unit for recording and reproducing the interference data from the interference processing unit provided in the interference type synthetic aperture radar, and the third recording / reproducing unit. Interference characterized by having a shake correction unit that takes a difference between the output interference data and the shake correction data output from the second recording / reproducing unit and outputs the difference data as correction interference data. Type synthetic aperture radar motion compensation device. 2. The interferometer according to claim 1, wherein the integrating unit 34 uses only the roll variation amount of the flying object in the motion data output from the first recording / reproducing unit. Synthetic aperture radar motion compensation device.