JP2001194456A - Composite aperture radar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain optimum point image response and a high-resolution images by compensating the vibration part of a plane, using the latest velocity data of an inertial navigation system, in a composite aperture radar system. SOLUTION: A signal for compensating plane vibration is formed, by using the latest velocity data of the inertial navigation system which are updated immediately prior to each transmitting of pulse. By multiplying the signal to a receiving signal, the vibration component of the plane is eliminated, and high-resolution imaging is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic aperture radar device which is mounted on a flying object such as an aircraft or an artificial satellite and compensates for a phase error caused by a fluctuation of the aircraft with high accuracy and acquires a high-resolution image. is there.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional synthetic aperture radar apparatus. In the figure, reference numeral 1 denotes a transmitting unit for transmitting radio waves, and 2 outputs a radio wave from the transmitting unit 1 and a reflected wave from a target. An input antenna, 3 is a receiving unit for receiving a radio wave from the antenna 2, 4 is a data processing unit for A / D converting a signal from the receiving unit 3, and 9 is the data processing unit 4.
An FFT conversion circuit 10 performs an FFT conversion of a signal from the FFT conversion circuit 10, a signal processing unit including the FFT conversion circuit 9, and an image output device 11 for displaying an image of the signal input from the signal processing unit 10.

Next, the operation will be described. Synthetic aperture radar is to temporally synthesize an equivalent array using the motion of an aircraft or a satellite as a radar platform. FIG. 8 is a diagram illustrating the principle of a synthetic aperture radar. In the figure, 14 is a synthetic aperture radar, 15
Is a radar beam, and 16 is the ground surface.

As shown in the figure, the synthetic aperture radar 14 keeps illuminating the point A on the ground 16 while moving from the position B to the position C. Therefore, by combining the data received from the point B to the point C, it is possible to equivalently combine an opening having a large length BC. At this time, the length BC is referred to as a synthetic aperture length, and the time required to move the length BC is referred to as a synthetic aperture time. Thus, the synthetic aperture radar can obtain a high resolution that cannot be obtained by a normal radar system in the same direction as the traveling direction of the platform.

However, in order to obtain this high resolution, it is necessary to correct the change in the distance between each reception point and the observation point with respect to the reception signal, and it is necessary to provide a signal processing circuit for this. Because this processing circuit is often large, it is often installed on the ground rather than on a platform.

The phase correction circuit in the signal processing circuit is hereinafter referred to as a synthetic aperture process. As can be seen from FIG. 8, in the above-described synthetic aperture radar, when the beam width is increased, the synthetic aperture length is increased, so that the theoretical resolution is improved by shortening the antenna length. In principle, the resolution is の of the antenna length. In the synthetic aperture radar, the resolution in the direction perpendicular to the platform is increased by a pulse compression technique used in a normal radar.

[0007]

The conventional synthetic aperture radar apparatus is constructed as described above, and does not take into account the actual movement of the aircraft, which is the platform of the radar, or the artificial body of the artificial satellite. Therefore, there is a problem in that the received signal contains a fluctuation component of the airframe, so that an optimal point image response cannot be obtained, and the resolution is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and calculates a high-resolution image by calculating an estimated position of a platform for each pulse using the latest speed data from an inertial navigation device. The purpose is to gain.

Another object of the present invention is to obtain a high-resolution image by smoothing velocity data even when the data rate of the inertial navigation device is lower than the pulse repetition period.

Another object of the present invention is to obtain a high-resolution image by cutting out a portion having a large error when smoothing velocity data of an inertial navigation system.

[0011]

According to a first aspect of the present invention, there is provided a synthetic aperture radar apparatus comprising: a phase compensation amount calculating means for calculating an amount of phase compensation due to a motion of an airframe from velocity data of an inertial navigation device; A synthesizing means for multiplying the signal for compensating the body motion from the phase compensation amount calculating means.

[0012] A synthetic aperture radar device according to a second aspect of the present invention comprises:
Phase compensation amount calculating means for calculating the phase compensation amount due to the fluctuation of the aircraft from the smoothed velocity data of the inertial navigation device, and synthesizing means for multiplying the received signal by the aircraft vibration compensation signal from the phase compensation amount calculating means. Are provided.

[0013] A synthetic aperture radar device according to a third aspect of the present invention comprises:
A phase compensation amount calculating means for calculating a phase compensation amount due to the fluctuation of the aircraft from the velocity data of the inertial navigation device smoothed after cutting out a portion having a large speed error; Combining means for multiplying the motion compensation signal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 6 denotes a phase compensation amount calculating circuit for calculating a phase compensation amount using the latest speed data from an inertial navigation device, and 7 denotes the phase compensation amount. The body motion compensation signal from the calculation circuit 6, 8 is a synthesizer that multiplies the received signal by the body motion compensation signal, 9 is an FFT conversion circuit that performs FFT conversion on the signal from the synthesizer 8, 1
Reference numeral 0 denotes a signal processing unit including the synthesizer 8 and the FFT conversion circuit 9, and reference numeral 11 denotes an image output device that displays an image of a signal input from the signal processing unit 10. Among the above, the transmitting unit 1, the antenna 2, the receiving unit 3, the data processing unit 4, the FFT conversion circuit 9, the signal processing unit 10, and the image output device 11 are equivalent to the conventional synthetic aperture radar device.

Next, the operation will be described. In the synthetic aperture radar apparatus configured as described above, the signal output from the transmission unit 1 is transmitted from the antenna 2, and the signal received by the antenna 2 is input to the reception unit 3, and the data processing unit 4 performs A / A D conversion is performed. Phase compensation amount calculation circuit 6
Then, the estimated position of the platform is calculated using the latest speed data of the inertial navigation device updated immediately before every transmission pulse.

An algorithm for calculating the latest speed data from the inertial navigation device will be described with reference to FIG. Here, the pulse repetition period is PRI, and the data rate of the inertial navigation system is To. As shown in FIG. 4, the position of the platform at time n · PRI (n is an integer) is obtained by using the velocity data Vs (m · To) at time m · To (m is an integer) updated by the inertial navigation system. Ps (n · PR
I) is Ps ((n-1) .PRI) + Vs (m.To)
・ It is estimated to be PRI. Here, Ps ((n−1) · P
RI) is the estimated position of the platform at time (n-1) PRI.

The estimated platform position Ps (n ·
Slant range Rs (n · PR) from PRI and target position
I) can be calculated, and the phase compensation amount is 4π / λ · Rs (n · P
RI). As a result, the body motion compensation signal 7exp (4π / λ · Rs (n · PRI)) is generated. By multiplying the received signal 5 by the combiner 8 with the body motion compensation signal 7, unnecessary body motion components can be removed. This is referred to as FFT in the signal processing unit 10.
The FFT conversion is performed by the conversion circuit 9 and sent to the image output device 11,
An optimal point image response can be obtained.

Embodiment 2 FIG. FIG. 2 is a diagram showing a second embodiment of the present invention. In FIG. 2, reference numeral 12 denotes a phase compensation amount calculation circuit for calculating a phase compensation amount using the latest speed data from the inertial navigation device which has been smoothed.

Next, the operation will be described. In the synthetic aperture radar apparatus configured as described above, the signal output from the transmission unit 1 is transmitted from the antenna 2, and the signal received by the antenna 2 is input to the reception unit 3, and the data processing unit 4 performs A / A D conversion is performed. Phase compensation amount calculation circuit 1
In FIG. 5, as shown in FIG. 5 (a), the latest speed data of the inertial navigation system updated immediately before each transmission pulse is smoothed by the hit pulse number corresponding time while overlapping the half of the hit pulse number corresponding time. Perform and average. For the smoothing, a first-order regression curve as shown in FIG. 5B or a second-order regression curve as shown in FIG. 5C is used.

Thus, even when the data rate of the inertial navigation device is slower than the pulse repetition period, speed data can be obtained with high accuracy. From this, the estimated position of the platform is calculated, the amount of phase compensation is estimated, and the body motion compensation signal 7 is generated. The calculation of the estimated position of the platform and the estimation of the phase compensation amount in the phase compensation amount calculation circuit 12 and the generation of the body motion compensation signal 7 are performed by the calculation of the estimated position of the platform and the phase compensation amount in the phase compensation amount calculation circuit 6 of the first embodiment. The operations are the same as those for the estimation and the generation of the body motion compensation signal 7. By multiplying the received signal 5 by the combiner 8 with the body motion compensation signal 7, unnecessary body motion components can be removed. This is subjected to FFT conversion by the FFT conversion circuit 9 in the signal processing unit 10 and sent to the image output device 11 to obtain an optimal point image response.

Embodiment 3 FIG. 3 is a diagram showing Embodiment 3 of the present invention. In FIG. 3, reference numeral 13 denotes phase compensation using speed data generated by cutting out a portion having a large speed error after smoothing the latest speed data from the inertial navigation device. 5 is a phase compensation amount calculation circuit for calculating the amount.

Next, the operation will be described. In the synthetic aperture radar apparatus configured as described above, the signal output from the transmission unit 1 is transmitted from the antenna 2, and the signal received by the antenna 2 is input to the reception unit 3, and the data processing unit 4 performs A / A D conversion is performed. Phase compensation amount calculation circuit 1
In FIG. 3, as shown in FIG. 6, the latest speed data of the inertial navigation system updated immediately before in each transmission pulse is smoothed by the hit pulse number corresponding time while overlapping the half of the hit pulse number corresponding time, and the speed error is further increased. Cut out 1/4 of each end of the regression curve with large. The smoothing is performed in the second embodiment.
5 (b) and 5 (c).

As a result, more accurate speed data can be obtained. From this, the estimated position of the platform is calculated, the amount of phase compensation is estimated, and the body motion compensation signal 7 is generated. The calculation of the estimated position of the platform, the estimation of the phase compensation amount, and the generation of the body motion compensation signal 7 in the phase compensation amount calculation circuit 13 are performed by the phase compensation amount calculation circuit 6 and the phase compensation amount calculation of the first and second embodiments. The operations of calculating the estimated position of the platform, estimating the amount of phase compensation, and generating the signal 7 for the body motion compensation in the circuit 12 are the same. By multiplying the received signal 5 by the combiner 8 with the body motion compensation signal 7, unnecessary body motion components can be removed. This is referred to as FF in the signal processing unit 10.
An FFT is performed by the T conversion circuit 9 and sent to the image output device 11 to obtain an optimum point image response.

[0024]

According to the first aspect of the present invention, it is possible to compensate for the fluctuation component of the aircraft by calculating the amount of phase compensation using the latest speed data of the inertial navigation system, and obtain a high-resolution image. be able to.

According to the second aspect of the present invention, the phase compensation amount is calculated by using the latest speed data of the inertial navigation device which has been smoothed, so that even when the data rate of the inertial navigation device is slower than the pulse repetition period, the airframe can be used. Can be accurately compensated for, and a high-resolution image can be obtained.

According to the third aspect, the phase compensation amount is calculated by using the data generated by cutting out a portion of the latest speed data of the smoothed inertial navigation device having a large speed error, and thereby calculating the phase compensation amount. Compensation can be performed with higher accuracy, and an image with higher resolution than the above effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a synthetic aperture radar apparatus according to the present invention.

FIG. 2 is a diagram showing Embodiment 2 of a synthetic aperture radar device according to the present invention.

FIG. 3 is a diagram showing Embodiment 3 of a synthetic aperture radar device according to the present invention.

FIG. 4 is a diagram showing an algorithm for calculating velocity data in the synthetic aperture radar apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an algorithm for calculating velocity data in a synthetic aperture radar according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an algorithm for calculating velocity data in a synthetic aperture radar according to a third embodiment of the present invention.

FIG. 7 is a view showing a conventional synthetic aperture radar test apparatus.

FIG. 8 is a diagram illustrating the principle of a conventional synthetic aperture radar.

[Explanation of symbols]

Reference Signs List 1 transmitter, 2 antenna, 3 receiver, 4 data processor, 6 phase compensation amount calculation circuit, 8 combiner, 9 FF
T conversion circuit, 10 signal processing unit, 11 image output device,
12 phase compensation amount calculation circuit, 13 phase compensation amount calculation circuit, 14 synthetic aperture radar.

Claims (3)

[Claims] 1. A synthetic aperture radar device mounted on a flying object, a transmitting / receiving means for transmitting a radio wave in a target direction and receiving a reflected wave from the target, and A / D converting a signal received by the transmitting / receiving means. Data processing means, synthesizing means for multiplying the received signal from the data processing means by a signal for compensating the aircraft motion of the flying object, and generating the signal for aircraft motion compensation using the latest speed data from the inertial navigation device The phase compensation amount calculating means, and the signal from the synthesizing means,
A radar apparatus comprising: an FFT conversion means for performing T conversion. 2. A synthetic aperture radar device mounted on a flying object, a transmitting / receiving means for transmitting a radio wave in a target direction and receiving a reflected wave from the target, and A / D converting a signal received by the transmitting / receiving means. Data processing means, synthesizing means for multiplying the received signal from the data processing means by a signal for compensating the body motion of the flying vehicle, and applying the signal for body motion compensation to the latest speed data from the inertial navigation device corresponding to the number of hit pulses. A phase compensation amount calculating means for generating a signal obtained by superimposing half of the time and performing smoothing by a regression curve, and an FFT converting means for FFT-transforming a signal from the synthesizing means. Radar equipment. 3. A synthetic aperture radar device mounted on a flying object, a transmitting / receiving means for transmitting a radio wave in a target direction and receiving a reflected wave from the target, and A / D converting a signal received by the transmitting / receiving means. Data processing means, synthesizing means for multiplying the received signal from the data processing means by a signal for compensating the body motion of the flying vehicle, and applying the signal for body motion compensation to the latest speed data from the inertial navigation device corresponding to the number of hit pulses. A phase compensation amount calculating means for obtaining by superimposing half of the time, cutting out quarters at both ends having a large speed error, and then using a smoothed one by a regression curve;
A radar apparatus comprising: an FFT conversion unit that performs an FFT conversion on a signal from the synthesis unit.