JP2785592B2 - Target position calculator for synthetic aperture radar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target position calculating device for a synthetic aperture radar, and more particularly to a target position calculating device for a synthetic aperture radar in which correction of a target position change due to a change in attitude of a flying object on which the synthetic aperture radar is mounted is ensured. .

[0002]

2. Description of the Related Art As shown in FIG.
A radar device 11 is mounted on a flying object such as an artificial satellite 10 and travels along a traveling direction 12 while a ground surface
Is observed by beam irradiation.

Conventionally, a target position in a beam irradiation field has been calculated on the assumption that a target position (hereinafter, referred to as a target position) exists right beside.

In FIG. 2, an artificial satellite 10 traveling in a traveling direction 11 irradiates a beam at a predetermined beam angle to the ground surface 12 obliquely below. The actual target position 14 indicates the irradiation state of the actually irradiated beam, and the ideal target position 15 is the actual target position 14.
The figure shows the ideal target position excluding the influence of the posture change and the like. Further, the beam center 13 indicates the direction of the beam center with respect to the irradiation field, which results in the Doppler center described below.

[0005]

In this conventional synthetic aperture radar, even when the target position (irradiation field) is deviated from a direction perpendicular to the traveling direction of the artificial satellite due to a change in the attitude of an on-board flying object, etc. Since the target position is calculated assuming that the position exists in the direction perpendicular to the traveling direction of the flying object, there is a problem that the corresponding ground position information in the synthetic aperture radar image processing becomes inaccurate.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a target position calculating device in a synthetic aperture radar that can accurately grasp ground position information even when the target position does not exist in a direction perpendicular to the traveling direction of the artificial satellite.

[0007]

SUMMARY OF THE INVENTION A target position calculating apparatus in a synthetic aperture radar according to the present invention performs high-speed Fourier transform on data acquired by a synthetic aperture radar mounted on a flying object such as an artificial satellite to obtain spectral domain data. A Doppler center frequency estimating unit for estimating the Doppler center frequency of the power maximum value for the spectral domain data, and inputting the orbit data of the flying object and horizontally setting the velocity vector on the ground. A rotation speed vector corresponding target position calculation unit that calculates a target position when rotated by α degrees from the set value, and inputs the trajectory data and the target position to determine the relative position between the flying object and the ground surface target. A relative speed calculator for calculating a speed, and calculating a Doppler frequency from the relative speed A Doppler frequency calculation unit, and a target position determination unit that determines and outputs a target position with respect to the Doppler frequency when the Doppler center frequency and the Doppler frequency match while changing the variation α degree from the set value. It has a configuration provided.

Further, in the target position calculating apparatus for a synthetic aperture radar according to the present invention, the change α from the set value of the speed vector in the target position calculating unit corresponding to the rotational speed vector is represented by the following: The ground surface and horizontal maximum vector rotation component to be set in advance are set as an initial value, and the initial value is input to the target position determination unit.The target position is determined until the Doppler frequency and the Doppler center frequency match. It has a configuration in which the control is performed while being reduced and changed by the determining unit.

[0009]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of one embodiment of the present invention.

The embodiment shown in FIG. 1 is a spectrum domain converter 1 for converting time domain synthetic aperture radar data obtained by a synthetic aperture radar mounted on an artificial satellite as a flying object into spectral domain (frequency domain) data. , A Doppler center frequency estimator 2 for estimating the Doppler center frequency of the worst maximum value with respect to the synthetic aperture radar data converted to the spectral domain, and the orbit data of the satellite, and inputting the velocity vector into the horizontal direction α The target position calculating unit 3 corresponding to the rotational speed vector for estimating the target position when rotated by degrees, the orbit data of the artificial satellite and the target position calculated by the target position calculating unit 3 corresponding to the rotational speed vector are input, and the artificial satellite A relative speed calculation unit 4 for calculating a relative speed with respect to a target on the ground, and a dopping based on the relative speed A Doppler frequency calculating unit 5 for calculating a frequency, an output of the Doppler frequency calculating unit 5 and an output of the Doppler center frequency estimating unit 2, and a target position corresponding to a rotational speed vector until the input Doppler frequency matches the Doppler center frequency. And a target position determination unit 6 for reducing the velocity vector rotation angle α of the calculation unit 3 from the initial maximum value.

Next, the operation of this embodiment will be described.

In FIG. 1, a spectral domain conversion unit 1
Performs fast Fourier transform on the input synthetic aperture radar data, converts the data into spectral domain (frequency domain) data, and outputs the data.

The Doppler center frequency estimating apparatus 2
The frequency with the power maximum from the spectral domain data,
That is, the Doppler center frequency is estimated and output.

The rotation speed vector corresponding target position calculation unit 3 calculates a target position corresponding to a rotation speed vector obtained by rotating a speed vector parallel to the surface of the artificial satellite by α degrees. The above-mentioned α degree sets the maximum value of the rotation angle of the velocity vector based on the attitude change of the artificial satellite as an initial value. The maximum value of α to be set as the initial value can be easily set in advance based on the allowable maximum fluctuation value of the attitude angle of the artificial satellite during flight.

As shown in FIG. 2, the target position calculating section 3 corresponding to the rotational velocity vector calculates the satellite velocity vector from the orbit data of the satellite, the earth ellipsoid model data and the distance between the satellite and the ground, as shown in FIG. The target position when rotated by α degrees in the direction is calculated and output.

The rotation angle α due to the fluctuation of the satellite velocity vector parallel to the ground surface results in a rotation angle α as a fluctuation amount of the target position on the ground surface, which is perpendicular to the traveling direction of the artificial satellite. The target position calculated as? Therefore,
In the target position calculating unit 3 corresponding to the rotation speed vector, α
The relative speed calculation unit 4 calculates a relative speed for the target position corresponding to the satellite speed vector rotated by α degrees, and calculates a relative speed corresponding to the target position corresponding to the satellite speed vector rotated by α degrees. Find the relative speed.

The Doppler frequency calculator 5 calculates the Doppler frequency based on the relative speed obtained by the relative speed calculator 4 by a known method.

The target position determining section 6 receives the Doppler center frequency estimated by the Doppler center frequency estimating section 2 and the Doppler frequency calculated by the Doppler frequency calculating section 5, and rotates the target Doppler frequency until the two Doppler frequencies match. The speed vector rotation angle α of the speed vector corresponding target position calculation unit 3 is controlled to be reduced from the maximum value of the initial value, and when the Doppler frequency and the Doppler center frequency match, a correct target position is output.

[0019]

As described above, the present invention estimates the Doppler center frequency of an actual target irradiated by a synthetic aperture radar using a radar mounted on a flying object, and provides a Doppler frequency that matches the Doppler center frequency. Calculating the position has an effect that a synthetic aperture radar image that secures accurate ground position information can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a target position when a velocity vector of an artificial satellite on which a synthetic aperture radar is mounted is rotated by α degrees horizontally on the ground.

FIG. 3 is a diagram showing target position fluctuations when the attitude of an artificial satellite equipped with a synthetic aperture radar changes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spectral-domain conversion part 2 Doppler center frequency estimation part 3 Target position calculation part corresponding to rotation speed vector 4 Relative velocity calculation part 5 Doppler frequency calculation part 6 Target position determination part 10 Artificial satellite 11 Radar device 12 Travel direction 13 Beam center 14 Actual Target position 15 Ideal target position

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (2)

(57) [Claims] 1. A spectrum domain conversion section for performing a fast Fourier transform on data acquired by a synthetic aperture radar mounted on a flying object such as an artificial satellite to convert the data into spectrum domain data; A Doppler center frequency estimating unit for estimating the maximum Doppler center frequency, and calculating the target position when the orbit data of the flying object is input and its velocity vector is rotated horizontally by α degrees from the set value by a variation amount from the set value horizontally. A rotational speed vector corresponding target position calculating unit, a relative speed calculating unit that inputs the trajectory data and the target position to calculate a relative speed between the flying object and a target on the ground, and calculates a Doppler frequency from the relative speed. A Doppler frequency calculating section for calculating, and changing the Doppler frequency while changing the variation α degree from the set value. Target position calculating system in the synthetic aperture radar, characterized in that it comprises a target position determination unit that determines a target position output for said Doppler frequency when the puller center frequency and the Doppler frequency matching. 2. A variation α from a set value of a speed vector in the target position calculating unit corresponding to the rotation speed vector.
The degree is determined by setting in advance the ground surface and horizontal vector maximum rotation component caused by the attitude change of the flying object to the velocity vector and setting this as an initial value, and inputting this initial value to the target position determination unit. A target position calculating device for a synthetic aperture radar, wherein the control is performed while decreasing the target position by the target position determining unit until the Doppler center frequency and the Doppler center frequency match.