JPS6020171A - Display device of synthetic-aperture radar - Google Patents

Abstract

PURPOSE:To display a radar image in form matching with the sensation of human beings by moving a frame being displayed according to the movement of an airframe. CONSTITUTION:A signal received by an antenna 1 is received by a receiver 4 and then processed by the signal processor 9 which consists of a pulse compression processor 5, range gate device 6, and azimuth compression processor 7 to input the result to the image memory 20 of an adaptive type scanner 19. Brightness information stored in the image memory 20 is displayed on a display device 22. A display position computing element 23 calculates the display position of each piece of brightness information on the display device 22. A controller 21 moves the display image vertically according to the moving speed of an airframe and rewrites the contents of the image memory 20 every time another frame is inputted.

Description

[Detailed description of the invention] This invention can be mounted on a VC on a flying object such as after an aircraft.

This relates to synthetic aperture radar that obtains images of the ground or sea surface.

First, the structure and principle of this type of conventional synthesis-Roseda will be explained. FIG. 1 is a block diagram showing the configuration of a conventional synthesis-lossider, and FIG. 2 is a block diagram.

It is a diagram showing the principle. In the figure, (1) is the antenna, (2)
is a circulator, (3) is a transmitter, (4) is a receiver,
(5) is a pulse compression processing device, (61 is a range gate device).

(7) is an azimuth compression processing device, (81 is a display device, [
91 is a signal processing device, θQ is the traveling direction of the flying object, α
υ is the antenna/7tprint, a is the observation cell, (I
3 is the range direction, t14 is the azimuth direction, and a ~ is the flying body.

(a) represents the transmitted signal, and (b) represents the received signal.

The transmission pulse signal generated by the transmitter (3) is transmitted via the circulator (2) and the antenna file to the transmission signal (A).
radiated toward the ground or sea surface. The radiated transmission signal (a) is reflected by a target on the ground or sea surface and is received again as a reception signal (ol) by the antenna 113.The reception signal (b) is sent to the circulator +
21 to the receiver (4). Receiver (4)
amplifies and detects the high frequency received signal and converts it to a baseband video signal.

This video signal is input to a pulse compression processing device (5) to increase the distance resolution, and pulse platen d is performed.

The pulse compressed video signal is passed through a range gate device (6
) and separated into range bins. In this case, the minimum distance difference ΔR that can be resolved into one is.

It is expressed as ΔR=−fi+ (C: light?, τ: pulse width after pulse compression).

Next, the output video signal of the range gate device is.

In order to increase the angular resolution in the azimuth direction I, azimuth compression is performed by an azimuth compression processing device (7).

Azimuth compression is a flying object equipped with synthetic aperture radar (
This is done by taking advantage of the Doppler effect caused by the movement of 151. Now, the square/to angle θ. The Doppler frequency fd from the target at is fd = child cosθ. (2) It is expressed as (v: flight speed of the flying object, λ: transmission wavelength). At this time, let 9 synthetic opening time be TI.

The minimum measurable Doppler frequency difference Δfd is Δfa=1
/Tx +31. Minimum angular difference (angular resolution) Δ that can be observed at this time
θ is Δθ=λ/(2vsin tun TI) +41.

In the fourth equation, the effective synthetic aperture length is L=yTl　einθo(51 Considering that it can be expressed as , the angular resolution Δθ is Δθ=λ/2L (61 becomes.

Pulse compression processing device (5), range gate device (6)
Synthetic aperture radar signal processing device u' 191 is a combination of three devices:
By dividing the ground or sea surface within υ within the antenna footprint by ΔR of the first equation for the range direction a, and by Δθ of the sixth equation for the azimuth direction t141, Sh.

Observation cell Q3 of size ΔR9Δθ is created. The video signal is decomposed into each observation cell component within the antenna footprint, and the signal strength of each component is arranged in a two-dimensional plane.
It is displayed as a radar image on the display device ffjtt8+.

After displaying the first frame, the first synthetic radar transmits and receives pulse radio waves and processes the received signal in exactly the same manner as described above, and after erasing the first frame, the second frame is displayed. The same applies to the third section below. 4th degree...The nth frame is displayed. At this time, the time during which one frame is displayed, frame time TF, is given by the following equation, for example.

TF = TI0TP t71 T: Synthetic aperture time TP: During signal processing time TF, the body fil that is flying is a distance of v'FF y
Therefore, the (n+1)th frame is an image of the ground surface shifted by the distance Pl of VTF in the y direction with respect to the nth frame. FIGS. 3 and 4 are diagrams for explaining the geometric relationship between frames.

In the figure, (Al, (Bl) are symbols representing the position of flying object α9.

αQ is the antenna beam when the flying object a4 is at (Al), and the antenna beam is at the same <(B).

Q~ is the target, [1 is the antenna beam (frame by IK).

(A) is a frame created by the antenna beam aη. When frame 01 is displayed, the flying object α9 is at position A, which remains on the display device (8) until frame 01 is obtained.
) is output above. When a frame prisoner is obtained, the flying body (I5 is at position B, so frame (to)
is the distance between A and B in the y direction with respect to frame Ql
``The image of the ground surface is shifted by vTF. Immediately after frame (A) is obtained, it is output on the display device +81 instead of the framer.

Now, if we pay attention to the target a, as shown in FIG. 4, each time the frame changes, the target 0 moves stepwise in the -Y direction by a distance corresponding to 7AB on the screen. The disadvantage of this type of video is that it is unnatural to the human senses and extremely difficult to view.

This invention attempts to solve the above problem by moving the frame being displayed in accordance with the movement of the flying object, and will be explained in detail below with reference to the drawings. al is an adaptive scanner;
The handle is an image memo IJ, t2υ is a controller, and Qz is a display.

The nth frame outputted from the signal processing device (9) is transmitted to the image memory (2), where it is stored until the n+1th frame is outputted. The controller Ql) instructs where on the screen of the display device the contents of the image memory are to be displayed, and performs display related controls such as screen erasure and screen display.

The controller Qυ controls the erasure and display of the screen at a constant cycle TW.
The contents of the image memory (a) are output on the repeating display OZ. However, the position of 1 display is calculated each time by the following formula.

X (i, j) = XO (1#j) t8 no Y (i, j
) =Yo (i ej)-Ks(lt)vTw(
91 here l;1. ~． L 1, j == Subscript indicating the image memory address X (is, i) e y (i,, +) = Pixel 1 *, +)
Coordinate value Xo(te,+)eYo(itj) in the coordinate system associated with the display device = initial coordinate value xs of pixel (itj) = scaling factor L = display number = (TF/Tw).

This calculation is performed by the display position calculator (c).

Controller 0 is sent to display position calculator (c) (1*v+T
Parameters such as W*''' eXo and Yo are transmitted to instruct calculations, and the 9 display position calculator (c) transmits the calculation results to the controller Qυ.

TV is a display (step-like movement of the screen on 2z)
KsvTw is selected to be sufficiently small so that it appears visually smoothly, and the image memory (a), the controller υ, and the display position calculator (c) form a so-called adaptive scanner a9.

During the L-th display of the n-th frame, the n+1-th frame is transmitted from the signal processing device (9) to the image memo IJ Ke, and the contents of the image memo IJ Ca1l are rewritten.

The next frame output to the display t2z is expressed by the formula t81,
+91, the position calculation was performed with 6=o (n+
1)+7) frames. The initial Y-coordinate value Y'o(1*j) in the (n+1')-th frame of the target commonly included in the n-th and (n+1)-th 7th AIC is the Y-coordinate initial value Y'o(Lj) in the n-th frame. ) can be expressed as the following formula: Y'0 (1-j)=”u(i,j) −Ks
L v Tw (1 (It is clear from 200)
The frames output to the display 12'A are from 14n to the nth frame.
Even in place of +1.

The movement of the target common to both frames is slightly KvTw
It is.

By repeating the above actions, the target that appears at the top of the display (to) will appear as the target you are about to fly! A moving image that smoothly moves downward in accordance with the movement of 9 and disappears under 1 display 02 is obtained, and a so-called line scanner-like image is obtained by the synthetic aperture radar.

It should be noted that although the description has been made here by taking a synthetic aperture radar as an example, the present invention is not limited to this, but can also be used for a display device of an image radar that takes an image of the ground surface using a real aperture radar.

As described above, according to the present invention, since radar images can be displayed in a form that matches human senses, Iruma's target detection and recognition ability can be improved, which has a significant effect.

[Brief explanation of drawings]

Fig. 1 is a book diagram showing the 474 configuration of a conventional synthetic aperture radar, Fig. M2 is a diagram showing the principle of synthetic aperture radar, and Figs. The figure shown in FIG. 5 is a diagram showing an embodiment of the present invention. In the figure, (!) is the antenna, (21 is the circulator, (
3) is a transmitter, (4) is a receiver, and (5) is a Norculus compression processing device. (6) Harenzi Gate Processing System@, [71 is the azimuth Senpai ID processing device, (8) is the display device, (9) is the signal processing device ~, Ql is the traveling direction of the flying object, αD is the antenna foot Print, H is the observation cell, Q31 is the range direction, (14 is the azimuth direction, 05 is the flying object,
uE9Qη is the antenna footprint, 0 seconds is the target,
H, (a) is a frame. α is an adaptive scanner, (A) is an image memo 1, and Q!
I] is the flilJ controller, ■ is the display, (2) is the display position calculator, (a) is the sending signal, (b) is the receiving signal, (A
l, (Bl is a symbol representing the position of the flying body (μ).In addition, in Figure 9, the same or equivalent parts are indicated with the same symbols. Agent Masuo Oiwa Figure 1 J Figure 21 3 figure n

Claims (1)

[Claims] In a display device for a synthetic aperture radar that takes an image of the ground surface in any desired direction other than the front or rear direction in the direction of movement of a flying object, a display device that displays an image memory and brightness information stored in the image memory; It is equipped with a computing unit that computes the display position of each luminance information on the display, the image memory and display, and a controller that controls the computing unit, and the display image is moved vertically according to the moving speed of the flying object. 1. A display device for synthetic aperture radar, characterized in that it has a function to move the image memory to the next frame, and a function to rewrite the contents of the image memory each time the next frame is input.