JPS60257602A - Synthetic aperture radar antenna - Google Patents

Abstract

PURPOSE:To obtain an accurate picture at reproduction of picture by providing an active flatness monitor comprising a light emitting element, a photodetector and a mirror arranged apart from them to a synthetic aperture radar antenna so as to detect the displacement of the flatness of the antenna. CONSTITUTION:An expanded panel type antenna 12 for the synthetic aperture radar is mounted on a flying body 11. A flatness monitor main body 14 is fitted to one end of a center supporting frame 13 of the antenna. The monitor main body 14 is constituted by arranging many photodetectors 16 concentrically around the light emitting element 15. A mirror 17 is arranged to the tip 12' of the antenna so as to be opposed to the flatness monitor main body 14. The displacement of the flatness of the part arranged with the mirror is detected by the light detection of the photodetector 16. The displacement is transmitted to ground together with other data, an antenna pattern is calculated from the displacement at the reproduction of a picture and then various parameters are corrected in reproducing the picture so as to obtain the accurate picture for the object to be observed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an annular head applied to a synthetic aperture mounted on a flying body such as an artificial satellite.

[Techniques of Invention 44.1 Disadvantages and Problems] In general, people
A video radar mounted on a flying object such as a satellite or aircraft (Plano 1 Fume J,) transmits radio waves to the ground on the side of the f-hyperactive 711 object, and transmits this foul wave while moving. By receiving and combining each time, a relatively small open 0 antenna is used.
A synthetic aperture lator that can effectively synthesize Ohma ITI antennas is well known.

Such a synthetic aperture radar is used as a video sensor and can obtain all-weather high-resolution images.

FIG. 1 is a diagram showing a schematic configuration of such a synthetic open[] rake. In the figure, ■ is the flight yI of artificial satellites, aircraft, etc.
I body (platform), 2 is a transmitter mounted on the flying object, 3 is a receiver, 4 is a J transmission/reception duplexer, 5 is a receiver 3
6 is an antenna.

Next, we will proceed with the synthetic development “II” made up of these members.
The principle of operation of the /-evening will be explained based on FIG. 2.

A flying object 1, such as an artificial satellite, moves at a speed V along a specific route or axis path I set in advance in a desired manner. L6. Along Z, 81, 8. , 8, . . . , transmit pulse radio waves are emitted from the small aperture antenna 6 of the synthetic aperture radar mounted on the tower R at fixed time intervals to. This transmitted pulse radio wave has a wide width β and is radiated in a direction perpendicular to the orbit, and is received by the same antenna 6 as a reflected wave (radar echo) from an object on the ground G.

These reflected waves are inputted one after another while the flying object I is moving at a speed of {circle around (2)}, and amplitude information and phase information are recorded in the recording device 5 as received signals at each time point. For example, the point target P of the object starts being irradiated with the transmitted pulse radio waves at a point A1 on the trajectory of the flying object 1, and ends being irradiated with the transmitted pulse radio waves at the point A1.

The reflected wave from the point target P is received during this time, and the received signal contains distance information as well as phase information corresponding to the constantly changing relative velocity.This received signal is recorded and subjected to batch calculation processing (holographic processing). Ink processing), the same effect as using an antenna with a long aperture can be obtained (synthetic aperture method).

In this way, by recording and synthesizing the received signals acquired at each location one after another, a large aperture antenna that is several tens to tens of thousands of times larger than the antenna actually installed is used. This is equivalent to observing the object, and the azimuth resolution is improved accordingly, resulting in a clearer image.

Since a synthetic aperture is formed according to the operating principle described above, during the operating time required to form a synthetic aperture, there are strict conditions not only for the trajectory and attitude of the flying object but also for the antenna itself. Stability is required.

When installed on a satellite, the synthetic aperture radar antenna is usually larger than the satellite itself, so a foldable deployable panel antenna is used.
Since it must be able to withstand the space environment, strict mechanical and thermal flatness is required. For example, 10
For antennas of several meters in length, strict flatness is required, with an average (average value of the displacement of the entire antenna panel relative to the reference plane) of 50 or less and a maximum (largest displacement relative to the reference surface of the entire antenna panel) of 25 fl or less. has been done.

However, despite this strict requirement for flatness, it has not been considered to directly monitor the flatness of the antenna during observation operations, so the obtained images and antenna The relationship with flatness has not been evaluated or analyzed. Therefore, if there is a variation in the flatness of the antenna in the space environment, the image will not be corrected based on that variation, and the image will not be corrected based on this variation. There was a problem in that errors were introduced and accurate images of the observed object could not be obtained.

[Purpose of the invention]

The present invention was made in order to solve the problem of overcasting in conventional synthetic aperture radars, and provides a synthetic aperture radar antenna that is equipped with an antenna flatness monitor to detect the amount of displacement of the antenna surface skin. The purpose is to provide

[Summary of the invention]

The present invention equips a synthetic aperture radar antenna with an active flatness monitor consisting of a light-emitting element, a light-receiving element, and a mirror disposed apart from these, detects the amount of displacement of the antenna flatness, and detects the amount of displacement of the antenna flatness to detect the synthetic aperture. This allows accurate images of objects to be observed to be obtained when reproducing radar images.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 3 is a plan view of one embodiment of the synthetic aperture radar antenna according to the present invention, FIG. 4 is a side view thereof, and FIG. 5 is an enlarged front view of the main body of the flatness monitor. In the figure, 11
1 is a flying object such as an artificial satellite, and 12 is a deployable panel antenna of a synthetic aperture radar mounted on the flying object 11. A flatness monitor main body 14 is attached to one end of the central support frame 13 of the antenna 12. The monitor main body 14 is constructed by arranging a large number of light receiving elements 16 concentrically around a light emitting element 15. On the other hand, antenna 1
A mirror 17 is disposed at the tip end 12' of the flatness monitor 2 so as to face the flatness monitor body 14.

In the synthetic aperture radar antenna 12 configured in this manner, light (for example, laser light) emitted from the light emitting element 15 of the flatness monitor main body 14 is reflected by the mirror 17 disposed at the tip 12' of the antenna 12. and light emitting element 1
The light is detected by one of the light receiving elements 16 arranged concentrically with respect to the light receiving element 5. Therefore, depending on which light receiving element 6 is used for detection, the amount of displacement in flatness of the mirror arrangement portion (in this embodiment, the tip) can be detected.

Then, the detected antenna flatness displacement is transmitted to the ground together with other data, and the antenna pattern is calculated from the displacement during image playback), and various parameters for image playback are corrected based on this. By adding , an accurate image of the observed object can be obtained.

In the above embodiment, one flatness monitor is arranged on the antenna, that is, the main body of the monitor is placed on the central support frame, and the mirror is placed on the tip, but the number of flatness monitors is not limited to one. Depending on the size of the antenna, a plurality of antennas can be arranged, and the arrangement position is not limited to the center and tip of the antenna, but can be appropriately set as necessary.

In addition, in the above embodiment, after detecting the displacement amount of the antenna flatness, the detected amount is used as the parameter correction amount during image reproduction. If the antenna panel is configured to be corrected by control, the flatness of the antenna panel itself may be automatically corrected in accordance with the detected displacement amount.

〔Effect of the invention〕

As described above in detail based on the embodiments, according to the present invention, the amount of displacement in the flatness of the antenna panel can be easily detected by the flatness monitor, and correction is made during image reproduction according to the amount of displacement. Alternatively, by correcting the flatness of the antenna panel itself, a positive image of the observation object can be obtained.

[Brief explanation of drawings]

The first FI is a schematic configuration diagram of a general synthetic aperture radar, and the second
3 is a plan view of an embodiment of the synthetic aperture radar antenna according to the present invention, and FIG.
The figure is a side view thereof, and FIG. 5 is an enlarged front view of the main body of the flatness monitor. In the figure, 11 is a flying object, 12 is a synthetic aperture radar antenna, 14 is a flatness monitor body, 15 is a light emitting element, 1
Reference numeral 6 indicates a light receiving element, and reference numeral 17 indicates a mirror. Figure 1 Complete Figure 2 East Figure 3 Figure 5

Claims (1)

[Claims] A composite plane mounted on a flying object such as an artificial satellite is equipped with an active flatness monitor consisting of a light-emitting element, a light-receiving element, and a mirror installed separately. A synthetic aperture radar antenna characterized by: