JPS6375687A - Spot light mapping radar apparatus - Google Patents

Abstract

PURPOSE:To perform continuous observation, by adding a beam direction control apparatus calculating an antenna beam direction satisfying a predetermined condition at a synthetic aperture time set to a required value. CONSTITUTION:On the basis of the speed V of a flight body, the distance R0 up to an observation object, the angle theta0 formed by a flight body advance direction and an observation object direction and an antenna beam width thetaB etc. from an inertial navigation apparatus 9, a time T capable of performing continuous observation satisfying formula I wherein time (t) and an aperture time T are t.(-T/2<t<T/2) is automatically set to a beam direction control apparatus 10. Whereupon, the apparatus 10 calculates an antenna beam direction theta(t) satisfying formula II to automatically drive an antenna. Then, receiving and detection outputs are processed by a pulse compression apparatus 5 enhancing distance/azimuth resolving power and an azimuth compression apparatus 6 and an observation object being ground surface or the surface of the sea is continuously observed and the corresponding image is displayed on a display device 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a spotlight mapping radar device for obtaining images on the ground or sea surface mounted on a flying body such as an artificial satellite or an aircraft. .

[Conventional technology]

For a conventional spotlight mapping radar device of this kind, for example, Br0Ok61n (3r, E, θ
d.

“Radar Technology”, Artec
h House, 197 B, ch. 181 Although this has been described in detail, the configuration and principle of the device will be briefly explained here.

FIG. 7 is a block diagram showing the configuration of a conventional spotlight 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 transmitter/receiver 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
+i Mari 7 Arens signal generator, (9) is the inertial navigation device, aυ is the antenna drive device, (A) is the transmitted signal, (B) is the received signal, (C) is the observation target, and (2) is the observation target (H). 1 point in ), (E) represents an antenna drive device, and (F) represents a flying object equipped with a spotlight matuping radar device.

Depending on the position and speed of the flying object measured by the inertial navigation device (9), the antenna drive device (I) directs the antenna (31i to the object to be measured).Then, the transmitter (
The transmission pulse signal generated in step 1) is radiated as a transmission signal (a) to an observation target on the ground or sea surface via a transmitter/receiver switcher (2) and an antenna (3).

The radiated transmission signal (a) is reflected by the observation target 2'L
.

It is received again by the antenna (3) as a received signal (b). The received signal (b) is input to the receiver (4) via the transmitter/receiver switch.
The signal is amplified and detected, and converted to a baseband video signal. This video signal is input to a pulse compression device (51) to perform pulse compression in order to improve distance resolution.

Pulse compression improves the resolution in the direction perpendicular to the traveling direction of the flying object, that is, in the distance (range) direction.At this time, the range resolution ΔR is:

It is expressed as ΔR=−−f4+ (C: speed of light, τ: pulse width after pulse compression).The video signal is then input to the azimuth compression device (6). Improve resolution in the azimuth direction. Azimuth compression (flying object equipped with a spotlight pine radar device)
This is done using the Doppler effect caused by t+fdl of γL. Now, as shown in Figure 8, the flying body has a velocity of V and a constant velocity of +1i! 3! Assume that the observation target (C) is in motion, and when the point in the observation target (C) is 1 time t = Q, the distance Ha
Consider the case at e Squint angle θo. This hearing 2
The relative distance R(t) of the flying body (to the point) at time t is.

is given by Therefore, the instantaneous Doppler frequency afa(1
) is given by using the transmission wavelength λ. As is clear from the third equation, the received signal is a chirp signal whose instantaneous Doppler frequency changes at the same time as time t. At this time, λ in the third formula,
Since RO1θQ,V are parameters that are known or can be measured from the inertial navigation device (9), the history of temporal changes in the Doppler frequency of the inertial navigation device (9), that is, the Doppler history, can be obtained by calculation using the reference signal generator (8). Can be done.

Therefore, by correlating the series of reception signals 43 and the reference signal generated by the reference signal generator (8) for each range, azimuth compression can be performed in the same way as pulse compression.

Generally, in the spotlight mapping radar device π (1, θo is set to θo=−, ?). At this time.

-8- The aperture time T is determined not by the antenna beam θB but by the azimuth angle movable range θS of the antenna drive device (the boresight direction of the antenna beam is (π-1)S)/2 It is assumed that it is movable within the range from (π+θs)/2. ] is determined.

θS 2R□tan() T = (given by 41. If the synthetic aperture time is T, the azimuth resolution Δr is.

is given by

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

[Problem that the invention seeks to solve]

Since the conventional spotlight 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 over a wide area, the observation target became discontinuous, making it difficult to continuously observe a wide range.

This invention was made to solve the above-mentioned problems, and is a spotlight matuping radar device that automates the antenna drive so that observation targets on the ground or the sea surface can be continuously observed. The purpose is to obtain.

[Means for solving problems]

The spotlight mapping radar device according to the present invention automatically sets the synthetic aperture time to enable continuous observation, and is equipped with an I-beam direction control device to control the movement of the antenna during one synthetic aperture. be.

[Effect]

In the spotlight mapping radar device according to the present invention, the distance RO 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 distance RO is set from the position of the flying object measured by the inertial navigation device to the moving speed V of the flying object and the antenna beam width θB. Based on.

The synthetic aperture time T is automatically set so that a continuous area can be observed, and the movement of the antenna during the two synthetic apertures is automatically controlled.

As a result, the spotlight matuping radar device of the present invention can continuously observe the ground surface or the sea surface.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention is shown in FIG. 1, and one drawing will be described in detail. In FIG. 1, (10 is a beam direction control device newly added in this invention, and all is a device that drives the antenna under the instruction of αO. To other devices (1) in the figure Since the operation in (9) is equivalent to that of the conventional device, the following explanation will focus on the operations of the beam direction control device α1 and the antenna drive device αυ. The operation will be explained according to FIG. 2.

In step Qυ, input the position and speed information of the flying object measured by the inertial navigation device (91), and calculate the distance from the flying object to the center of the observation target! The angle formed by the squint angle θ
o and the moving speed V of the flying object are set, and the azimuth angle movable range θS of the antenna driving device I is set equal to the azimuth direction beam width θB of the antenna (3). However, in the following explanation, θo=-.

θS=θB(6) In step ■, 2 synthetic opening time T from the 6th 27th equation 4 ■ Calculate.

After the synthetic opening time T is determined, from step @(1)
In order to control the beam power opening of the antenna, the actual time tin is set to the time t during the synthetic aperture fi! 4. First, because of the step, the remainder Rθ when the real time tin is divided by the synthetic opening time T is tin Rom = tin − [−) T (
Find 91. In the ninth equation, the Gauss symbol [ ] shall take the largest integer value within the parentheses.

In step CD, the absolute value lRem1 of this remainder Rem
and T/2, l Roml) T/
At step 2, proceed to the final step.

t-Hem-T (11)
Then, if lRem1≦T/2, proceed to step (c) and t=Rem a
Let υ. The state of time conversion is shown in FIG. 3 Eζ. 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 Figure 1 indicates that this point is included, and a white circle indicates that this point is not included, and each sawtooth circular mountain corresponds to the number of observations #1 to #5. do.

In step (5), the antenna beam direction θ(1) = cos-1(r, +v2t2) (1
3 is obtained, and an instruction is issued to the antenna driving device (1, υ) in step @. An example of calculating θ(1) is shown in FIG. 4E.

At step 3, it is determined whether the observation has ended, and if it is to continue, the actual time tin lz is updated and the process returns to step (end).

In the case of termination, the process ends.

Through the above processing, the direction θ of the antenna beam is automatically controlled Iζ as shown in FIG. 5 with respect to the real time tin, and the first observation is made in the section #1.

The second observation is carried out in section #2, and the third observation is carried out in section #3. At this time, in each observation, the azimuth angle movable range of the antenna is automatically adjusted to (π-θB)/2.
to (π+θB)/2, so as shown in FIG. 6, $1. $2. #3. Observations #4 and #5 enable continuous observation of the ground or sea surface. The above explanation is for simplicity.

Although θo has been described using - as an example, this invention can be applied to any θo
It is valid for

〔Effect of the invention〕

As described above, according to the present invention, the beam direction control device can control the moving speed of the flying object, the distance to the observation target,
By automatically setting the synthetic aperture time to enable stray observations according to the antenna beam width, the antenna's azimuth angle movable range is limited, and the antenna beam direction during the synthetic aperture is calculated in a timely manner. However, since the antenna and I-motion device can be controlled, it becomes possible to observe a continuous area, which was difficult with conventional spotlight mapping radar equipment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a spotlight mapping radar device according to an embodiment of the present invention, FIG. 2 is an operation flowchart of the beam force direction control device fi (1B) added in the present invention, 4 and 5 are diagrams for explaining the operation, Figure 6 is a diagram for explaining the details of the invention, Figure 7 is the configuration of a conventional spotlight mapping radar device, and Figure 8 is a diagram for explaining the details of the invention. 9 is a diagram for explaining the operating principle of a spotlight mapping radar, and FIG. 9 is a diagram showing an example of operation of a conventional spotlight mapping radar device. In the figure, (1) is a transmitter, (2) is a transmitter/receiver 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, (9) is an inertial navigation device,
αl is a beam force direction control device, and υ is an antenna drive device. Note that in the two figures, the same reference numerals indicate the same - or ■'' portions.

Claims (2)

[Claims] (1) In a spotlight mapping radar device that is mounted on a flying object such as an artificial satellite or an aircraft and obtains images of the ground or sea surface, there is an inertial navigation device that measures the movement of the flying object, and an inertial navigation device that measures the movement of the flying object. The synthetic aperture time T and time t-(-T/2
<t≦T/2), the beam direction θ(t) is determined by the first formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) A beam direction control device and an antenna according to the output of the beam direction control device an antenna driver that drives the antenna, an antenna that emits radio waves toward the observation target and receives reflected waves, a transmitter, a receiver, and pulse compression that improves the range resolution of the signal detected by the receiver. What is claimed is: 1. A spotlight mapping radar device comprising: an azimuth compression device that improves azimuth resolution; a reference signal generation device that generates a reference signal necessary for azimuth compression; and a display device. (2) In the beam direction control device, the beam direction θ(t) at the synthetic aperture time T and time t (-T/2<t≦T/2) is calculated using the following formula: T=(R_oθ_B)/v (21) and the 22nd formula θ(t)=cos-i((R_ocosθ_o-vsi
2. The spotlight mapping radar device according to claim 1, wherein the calculation is performed using the approximation formula of n2θ_ot)/R_o)) (22).