JP2743560B2 - Synthetic aperture radar device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic aperture radar, and more particularly, to a synthetic aperture radar apparatus that is operated using a small-sized aircraft that does not have an inertial navigation device mounted on a moving platform.

2. Description of the Related Art Synthetic aperture radar devices using a flying object such as a large aircraft or artificial satellite equipped with an inertial navigation device as a moving platform are well known. Resolution δ _{r in the} direction of distance perpendicular to the direction of flight of the flying object by this synthetic aperture radar device
Is (1) expressed as equation, the distance resolution [delta] _r mainly inversely proportional to the signal bandwidth Delta] f.

δ _r = C / 2 · 2.8 / π · 1 / Δf · 1 / cosθ (1) C: radio wave propagation velocity, Δf: signal bandwidth, θ: elevation angle, and parallel azimuth resolution in the traveling direction of the flying object δ _a will,
It is expressed as in equation (2).

δ _a ≒ D / 2 = V / f _D (2) D: real aperture of antenna, v: speed of aircraft f _D : Doppler bandwidth As is clear from equations (1) and (2), synthetic aperture The radar system has a problem that δ _r and δ _a are not constant because the θ, v, and f _D are greatly affected when the aircraft sway is large, and there is a fundamental problem that the image is missing in severe cases. . Conventionally, in order to solve this problem, an inertial navigation device is mounted on an aircraft or the like to minimize the sway, and at the same time, the attitude error data is recorded and corrected at the time of image reproduction.

[Problems to be solved by the invention]

In the above-mentioned conventional synthetic aperture radar system, a very high attitude stability accuracy is required for the flying object as a mounting platform. There is a problem that it is impossible to obtain a high quality synthetic aperture radar image.

[Means for solving the problem]

The synthetic aperture radar system of the present invention receives information from a position measurement device which is mounted on a small aircraft and measures its own position using an artificial satellite, and obtains a distance resolution and a surrounding resolution corresponding to the attitude stability of the small aircraft. It has a configuration in which the beam width of the transmission radio wave is widened and the pulse repetition frequency is increased to such an extent that the degradation of the target information caused by the decrease can be compensated.

Further, the synthetic aperture radar device of the present invention has a configuration in which the information received from the position measurement device includes information on the position, speed, and altitude of the small aircraft.

〔Example〕

 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 mounted on a small machine such as a Cessna machine and uses a position measuring device (Global Positioning System) 6 for acquiring information such as position / velocity / altitude using an artificial satellite, and a synthetic aperture radar device. Comprising 10. Also, synthetic aperture radar system
Reference numeral 10 denotes a transmitting unit 1 for generating a transmitting pulse, a receiving unit 2 for receiving a receiving pulse from the ground, a SAR (Synthetic Aperture Radar) antenna 3 for transmitting and receiving a transmitting and receiving pulse, and a receiving unit. A signal processing unit 5 for processing the output of the second unit 2 to output an output signal 12, and a transmitting unit 5 based on position / velocity / altitude information 9 output by the position measuring device 6
Control of the transmission condition of the signal processing unit 4
And a control unit 5 for performing the above signal processing.

FIG. 2 is an operation conceptual diagram for explaining the operation of the present invention. Before describing the operation of the embodiment shown in FIG. 1, the principle of the operation of the present invention will be described first.

In FIG. 2, reference numeral 13 denotes a plurality of artificial satellites for the aircraft to obtain data on its own position / altitude / speed and the like. The aircraft 17 traveling in the traveling direction L receives the radio waves from the artificial satellite 3 and processes them to obtain the above-described data. The current of the synthetic aperture radar radiated from the aircraft 17 to the ground is higher than the conventional one, with an azimuth beam width 14 having a wider beam width, a higher pulse repetition frequency,
Therefore, the transmission pulse 16 has a narrow transmission pulse interval 15. In this way, with a wide azimuth beam width 14,
Since the target 18 can be observed for a longer time than before, sufficient information on the target 18 can be obtained even if the aircraft 17 slightly shakes. Also, transmission pulses with high pulse repetition frequency
By adopting the 16, it is possible to accurately follow the fluctuation of the aircraft 17. The main point of the present invention is to incorporate as much aircraft motion information as possible into the received synthetic aperture data.

 Returning to FIG. 1, the description of the embodiment will be continued.

The transmitting unit 1 generates a transmission pulse of the synthetic aperture radar device 10 and radiates it from the SAR antenna 3 toward the ground. The received pulse reflected from the ground is received by the SAR antenna 3 and amplified to a predetermined level by the receiving unit 2, and then is received by the signal processing unit 4.
A / D conversion, range (distance) / azimuth (azimuth) compression, and the like are performed and output as an output signal 12.

The received radio wave 8 from the artificial satellite 13 is transmitted to the receiving antenna 7
The position / velocity / altitude information 6 is obtained by processing by the position measuring device 6, and this information is output to the control unit 5 at a speed sufficient for image processing.

The control unit 5 sets an optimum pulse repetition frequency necessary to secure a desired resolution or the like from the altitude information or the like provided in this way, and outputs a pulse repetition switching control signal 11 for supplying this information to the transmission unit 1. I do. The position / velocity / altitude information 9 is also input to the signal processing unit 4 and used directly for processing in the signal processing unit 4 or attached to the data of the output signal 12.

〔The invention's effect〕

As described above, the present invention is capable of obtaining attitude error information from a received SAR image by providing a position measuring device using an artificial satellite, increasing the antenna beam width, and increasing the pulse repetition frequency. Thus, there is an effect that a high-quality image can be obtained even with a SAR mounted on a small aircraft having poor attitude stability.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a conceptual diagram of the operation of the present invention. 1 ... transmitter, 2 ... receiver, 3 ... SAR antenna, 4 ... signal processor, 5 ... controller, 6 ... position measuring device, 7 ... receiver antenna, 8 ... received radio wave, 9 …… Position / velocity / altitude information, 10
... Synthetic aperture radar device, 11 ... Pulse repetition switching control signal, 12 ... Output signal, 13 ... Satellite, 14 ... Azimuth beam width, 15 ... Transmission pulse interval, 16 ... Transmission pulse, 17
…… Aircraft, 18 …… Target.

Claims (1)

(57) [Claims] 1. A distance corresponding to the attitude stability of a small aircraft while receiving information on the position, speed, and altitude of the small aircraft from a position measuring device mounted on the small aircraft and measuring its own position using an artificial satellite. A synthetic aperture radar apparatus characterized in that a beam width of a transmission radio wave is widened and a pulse repetition frequency is increased so as to be able to compensate for the deterioration of target information caused by a decrease in resolution and azimuth resolution.