JPH0245158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a spot light mapping radar device that is mounted on a flying object such as an artificial satellite or an aircraft and that obtains images on the ground or sea surface.

[Conventional technology]

Conventional spot light mating radar devices of this type are described, for example, in Brookener, E.ed.
“Radar Technology”, Artech House, 1976
This is described in detail in ch.18, but here we will briefly explain the structure and principle of the device.

FIG. 7 is a block diagram showing the configuration of a conventional spot light mapping radar device, and FIGS. 8 and 9 are diagrams for explaining its operating principle and operation.

In the figure, 1 is a transmitter, 2 is a transmission/reception switch, 3 is an antenna, 4 is a receiver, 5 is a pulse compression device, 6 is an azimuth compression device, 7 is a display device, 8 is a reference signal generator, and 9 is an inertia. Navigation equipment, 11 is an antenna drive device, A is a transmitted signal, B is a received signal, C is an observation target, D is a point in the observation target (C), E is an antenna beam, F is a spot light mapping radar device. represents a flying body.

In accordance with the position and speed of the flying object measured by the inertial navigation device 9, the antenna driving device 11 directs the antenna 3 toward the observation target d. Thereafter, the transmission pulse signal generated by the transmitter 1 is radiated as a transmission signal A to an observation target D on the ground or sea surface via a transmitter/receiver switch 2 and an antenna 3. The radiated transmission signal A is reflected by the observation target and is received by the antenna 3 again as a reception signal B. The received signal B is input to the receiver 4 via a transmitter/receiver switch. The receiver 4 amplifies and detects the high frequency received signal and converts it into a baseband video signal. This video signal is inputted to a pulse compression device 5 and subjected to pulse compression in order to improve the distance resolution. Pulse compression improves the resolution in the direction perpendicular to the direction of travel to the flying object, that is, in the range direction. At this time, the range resolution ΔR is expressed as ΔR=Cτ/2 (4) (C: speed of light, τ: pulse width after pulse compression). The video signal is then input to an azimuth compression device 6 to improve the resolution in the direction of travel to the flying object, that is, in the azimuth direction. Azimuth compression is performed using the Doppler effect produced by the movement of a spot light mapping radar device onto a flying vehicle. Assume now that the flying object is moving in a uniform straight line at a speed v as shown in Figure 8, and one point D of the observation target C is at a distance R _p and a squint angle θ _p at time t = 0. Consider a case. At this time, the relative distance R(t) between the flying object and point 2 at time t is given by R(t)=√ _p ² −2 _{p p} + ^{2 2} (2). Therefore, the instantaneous Doppler frequency f _d
(t) using the transmission wavelength λ is given by As is clear from the third equation, the received signal is a chirp signal whose instantaneous Doppler frequency changes with time t. At this time, since λ, R _p , θo, and v in the third equation are parameters that are known or can be measured by the inertial navigation device 9, the history of the time change of the Doppler frequency at point 2, that is, the Doppler history, is the reference signal generation. It can be calculated using the device 8. Therefore, for each range, a series of received signals,
By making a correlation with the reference signal generated by the reference signal generator 8, azimuth compression becomes possible in the same way as pulse compression.

Generally, in spot light mapping radar devices, θ _p is set to θ _p =π/2. At this time, the included aperture time T is not the antenna beam width θ _B but the azimuth angle movable range θ _S of the antenna drive device (with the direction of movement of the flying object as the reference, the boresight direction of the antenna beam is (π − θ _S ) /2 to (π+
It is movable within the range up to θ _S )/2. ) and is given by T=2R _p tan(θ _S /2)/v (4). When the synthetic aperture time is T, the azimuth resolution Δr is given by Δr=λ/2√( _p ) ² +(12) ² (5).

Through the above processing, the received signal with high resolution in both the range direction and the azimuth direction is displayed on the display device 7 as a two-dimensional radar image.

[Problem that the invention seeks to solve]

Since the conventional spot light mapping radar device is configured as described above, the azimuth resolution can be freely selected by selecting the azimuth angle movable range of the antenna driving device. When observations were made, the observation target became discontinuous, making it difficult to continuously observe a wide range.

This invention was made in order to solve the above-mentioned problems, and it is a spot light pine radar that automates the antenna drive so that it can continuously observe observation targets such as the ground or sea surface. The purpose is to obtain equipment.

[Means for solving problems]

The spot light mapping radar device according to the present invention automatically sets the synthetic aperture time to enable continuous observation, and has a beam direction control device added to control the movement of the antenna during the synthetic aperture. .

[Effect]

In the spot light mapping radar device of this invention, the distance R _p from the position of the flying object measured by the inertial navigation device to the observation target is set by the beam direction control device, and the moving speed v of the flying object and the antenna beam width are set. Based on θ _B , the synthetic aperture time T is automatically set so that a continuous area can be observed, and the movement of the antenna during the synthetic aperture is automatically controlled.

As a result, the spot light mapping radar device of the present invention can continuously observe the ground surface or the sea surface.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention is shown in FIG. 1, and the drawing will be described in detail. In Figure 1, 1
0 is a beam direction control device newly added in this invention, and 11 is a device that drives the antenna under the instruction of 10. Since the operations of the other devices 1 to 9 in the figure are equivalent to those of the conventional devices, the following description will focus on the operations of the beam direction control device 10 and the antenna drive device 11. An operation flowchart of the beam direction control device 10 is shown in FIG. 2, and the operation will be explained according to the figure.

In step (21), the position and speed information of the flying object measured by the inertial navigation device 9 is input, and the distance R _p from the flying object to the center of the observation target, the traveling direction of the flying object, and the direction of the observation target are determined. the angle formed by
That is, the squint angle θ _p and the moving speed v of the flying object are set, and the azimuth angle movable range θ _S of the antenna driving device 11 is set equal to the beam width θ _B of the antenna 3 in the azimuth direction. However, in the following description, θ _p =π/2.

θ _S =θ _B (6) In step (22), the synthetic opening time T T =2R _p tan (θ _B /2)/v (7) is calculated from the sixth equation and the fourth equation.

After the synthetic aperture time T is determined, in steps (23) to (26), in order to control the beam direction of the antenna, the real time tin is set to the time t −T/2<t≦T/2 during the synthetic aperture (8 ). First, in step (23), the real time
The remainder Rem=tin−[tin/T]T (9) is determined when tin is divided by the synthetic opening time T. In the ninth equation, the Gauss symbol [ ] shall take the largest integer value within the bracket.

In step (24), the absolute value of this remainder Rem |Rem| is compared with T/2, and |Rem|>T/2
If so, proceed to step (25), set t=Rem−T (10), and if |Rem|≦T/2, proceed to step (26).
Proceed to and set t=Rem (11). Figure 3 shows how the time conversion is performed. In FIG. 3, the horizontal axis represents actual time tin, and the vertical axis represents time t after conversion. In addition, a black circle in the figure indicates that this point is included, and a white circle indicates that this point is not included, and one of the sawtooth-shaped mountains 1
correspond to the number of observations #1 to #5, respectively.

In step (27), the antenna beam direction θ(t) corresponding to time t after conversion is is determined, and an instruction is issued to the antenna driving device (11) in step (28). An example of calculation of θ(t) is shown in FIG.

At step (29), it is determined whether the observation has ended, and if it is to continue, the actual time tin is updated, and at step (23)
Return to In the case of termination, the process ends.

Through the above processing, the direction θ of the antenna beam is automatically controlled as shown in FIG.
Second observation in section #2, third observation in section #3
The second observation is carried out, and in each observation, the azimuth angle movable range of the antenna is automatically limited from (π-θ _B )/2 to (π+θ _B )/2, so the As shown, #1, #2,
Observations #3, #4, and #5 allow continuous observation of the ground or sea surface. In the above explanation, for simplicity, θ _p is π/2 as an example, but the present invention is effective for any θ _p .

〔Effect of the invention〕

As described above, according to the present invention, the beam direction control device automatically adjusts the synthetic aperture time to enable continuous observation according to the moving speed of the flying object, the distance to the observation target, and the antenna beam width. By setting this, it is possible to limit the antenna's azimuth angle movable range, calculate the antenna beam direction during the synthetic aperture in a timely manner, and control the antenna drive device, which is difficult to do with conventional spot light mapping radar equipment. This makes it possible to observe a continuous area with high temperature.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a spot light mapping radar device according to an embodiment of the present invention, and FIG. 2 is a beam direction control device 1 added in the present invention.
0, FIG. 3, FIG. 4, and FIG. 5 are diagrams for explaining the operation. FIG. 6 is a diagram for explaining the effect of this invention. FIG. Block diagram of ping radar device, No. 8
This figure is a diagram for explaining the operating principle of a spot light mapping radar, and FIG. 9 is a diagram showing an example of operation of a conventional spot light mapping radar device. In the figure, 1 is a transmitter, 2 is a transmission/reception switch, 3 is an antenna, 4 is a receiver, 5 is a pulse compression device, 6 is an azimuth compression device, 7 is a display device, 8 is a reference signal generator, and 9 is an inertia. A navigation device, 10 a beam direction control device, and 11 an antenna drive device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a spot light mapping device mounted on a flying object such as an artificial satellite or an aircraft to obtain an image of the ground or sea surface, an inertial navigation device that measures the movement of the flying object and an inertial navigation system are used. The synthetic _aperture time _T and time _t ( −T/2<t≦T/2), the beam direction θ (t) is expressed by the first equation T=2R _p tan(θ _B /2)/v (1) and the second equation a beam direction control device that determines the direction of the beam, an antenna drive device that drives the antenna according to the output of the beam direction control device, an antenna that emits radio waves toward an observation target and receives reflected waves, a transmitter, and a receiver. a pulse compression device that improves the range resolution of the signal detected by the receiver, an azimuth compression device that improves the azimuth resolution, a reference signal generator that generates a reference signal necessary for azimuth compression, and a display device. A spot light mapping radar device comprising: 2. In the beam direction control device, the beam direction θ (t) at the synthetic aperture time T and time t (-T/2<t≦T2) is determined by the following equations: T=R _p θ _B /v (21) and the 22nd equation. Spot light mapping according to claim 1, characterized in that the calculation is performed using an approximate expression of the formula θ(t) cos ^-1 (R _p cos θ _p -v sin2θ ₀ t/R _p (22) radar equipment.