JPH0693028B2 - Radar device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a radar device, and more particularly to a device suitable for measuring a physical size of a target that makes a motion including a rotary motion.

[Technical background of the invention]

FIG. 5 shows a schematic configuration of a general radar device. In this radar device, the highly stable oscillator 10 is a circuit that generates a stabilized signal of a predetermined frequency, and the generated signal is supplied to the transmitter 20 and the receiver 50, respectively. The transmitter 20 generates a pulse signal having a required repetition period on the basis of the input signal, and transmits the pulse signal to the transmission / reception switch.
Supply to the antenna 40 via 30. As a result, the same pulse signal is emitted from the antenna 40 as a transmission signal. on the other hand,
The reflected wave from the target is received by the antenna 40, and this is supplied to the receiver 50 via the duplexer 30.
The oscillation signal of the highly stable oscillator 10 is also supplied to the receiver 50 as described above, and the reception signal is mixed with the oscillation signal and demodulated. This demodulated signal is supplied to the display device 60 and displayed appropriately.

By the way, the microwave band radar is generally known to be difficult to be influenced by the weather and the like, but it has been said that it is difficult to know even the shape of a target by the microwave band radar. This is because the spatial resolution of the radar itself is coarser than the target size. Here, as a technique to overcome this, a synthetic aperture radar (hereinafter abbreviated as SAR)
Was proposed and put into practical use. This like a number
SAR is a system in which an antenna and a transmitter / receiver are mounted on a platform that moves at high speed, and target echo data is collected at many places in the space associated with the movement of the antenna and the transmitter / receiver. By doing so, directivity equivalent to that of an antenna having a large aperture length is created, and the resolution of the radar device is improved.

However, in view of these functions of SAR, conversely, it can be inferred that even if the target object is moving, a normal fixed radar will be able to obtain the same high resolution as the above SAR. .

As an example of this, a method for obtaining high-resolution information about a target that rotates will be described below with reference to FIG.

Now, assuming that the point p, which is located r away from the center of rotation on the target, is two-dimensionally rotationally moved with angular velocity ωr and velocity v in the manner shown in FIG. Receives a signal with the Doppler frequency fd given by

Where λ is the wavelength of the radar transmission wave, x is the distance from the rotation center of the target to the point P on the x-axis taken in the direction perpendicular to the radar direction, and this observation is continued for time T. Then, since the frequency can be decomposed for each 1 / T, the resolution Δfd for the Doppler frequency fd is And the corresponding resolution in the x-axis direction in the figure Δx
Is Will be expressed as

As described above, with respect to the rotating target, it is possible to obtain high spatial resolution by simplifying the target with an appropriate time width. However, the resolution obtained by the equation (3) is the resolution in the direction orthogonal to the distance direction (hereinafter, this direction is referred to as the cross range direction, and the resolution in this direction is referred to as the cross range resolution). It is assumed to be obtained by pulse compression such as modulation within a transmission pulse.

[Problems of background technology]

The above-mentioned method is effective in that the target is decomposed in the cross range direction to improve this resolution, but the size of the target in the cross range direction cannot be directly known.
As a radar device, there still remains a problem. When the target is a ship or an aircraft, the rotational motion thereof is also a single vibration rolling, pitching or yawing motion, and the rotational speed changes from moment to moment. Therefore, the resolution obtained above is not constant.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radar device capable of directly measuring the size in the cross range direction of a target that makes a motion including at least a rotary motion.

[Outline of Invention]

In the present invention, the pulse signal is radiated to the target with a separation resolution capable of separating the target into a plurality of distance parts, and as a result, based on the signal corresponding to each reflected wave for each of the separated distance parts of the target. On the one hand, the received signal is decomposed by Doppler frequency to capture the shape of the target with the distance in the pulse signal radiation direction and the Doppler frequency as parameters, and on the other hand, from the received signal, the target rotational motion The center position is sequentially obtained, and the movement direction of the same target is further obtained from this transition. Finally, the angle (corresponding to the angle between the x-axis and the target-see FIG. 6) corresponding to the angle θ from the obtained moving direction of the target is determined, and the same angle is determined based on the value of the determined angle. The parameters relating to the target shape are converted into the distance in the pulse signal emission direction and the distance on the axis (x axis) orthogonal to the distance. As a result, the target is expressed by coordinates that can directly express the size, such as coordinates in the so-called distance direction and coordinates in the cross range direction, and it is possible to appropriately display an image with the converted parameters. If so, the physical shape of the target can be accurately known.

〔The invention's effect〕

As described above, according to the radar device of the present invention, the size of the target in the cross-range direction accompanied by the rotational motion can be directly measured, which is very useful in determining the physical shape of the target. Can bring various data.

Example of Invention

First, the principle of the present invention will be described with reference to FIG.

As described above, when the radar device and the target have the relationship as shown in FIG. 6, the radar receives the signal having the Doppler frequency fd as shown in the equation (1). , In this equation (1), P from the target rotation center
Since the distance r to the point and the angle θ formed by the target and the x-axis are unknown, both (2ωr / λ) and x in the equation are unknown, and the Doppler frequency fd is directly converted to the value of x in this state. It is not possible.

Therefore, in this invention, the distance from the radar to the point P R, also in the case where the distance to the rotational center of the target from the radar set to R _0, if R ₀ -R«R ₀ (normally this condition Holds), and the value of x above Paying attention to that, the value of x is substituted into the equation (1). Ie Becomes The values of R and R ₀ can be naturally understood from the time difference between the reception echo (reflected wave from the target) of the radar and the transmission pulse. Therefore, according to this equation (5), the value of (2ωr / λ), which is the proportional coefficient between the Doppler frequency fd and x, can be estimated by knowing the value of θ, which is the angle formed by the target and the x-axis. It can be seen that the information obtained as the Doppler frequency fd can be converted into the value of x, that is, the distance value in the cross range direction.

In determining the angle θ formed by this target and the x-axis, for example, the following method is effective.

When, for example, a ship or an aircraft is assumed to be the target, various vibrations and oscillations (these are considered to be rotational movements) occur during its operation, but the hull or body is generally oriented in the same direction as the traveling direction. It is considered that (this tendency is particularly remarkable in the case of ships). Therefore, by observing the positions of these targets continuously or intermittently and tracking them, it is possible to know this direction of travel, and if this direction of travel is known, the above-mentioned (direction of target) ≒ (progress of target) Direction), the direction of the target with respect to the cross range direction, that is, the angle θ between the target and the x-axis can be determined.

In this way, the information obtained as the Doppler frequency fd is effectively converted into the distance value x in the cross range direction.

FIG. 1 shows an embodiment of a radar device according to the present invention constructed on the basis of such a principle. However, this first
In the figure, elements having basically the same function as the elements shown in FIG. 5 are designated by the same reference numerals,
A duplicate description will be omitted.

The device of this embodiment is constructed by newly interposing a reception signal processing device 70 between the receiver 50 and the display 60 described above. However, in the transmitter 20 and the receiver 50, the hollow wire 40 has a distance resolution capable of separating the target into a plurality of distance portions.
It is assumed that the pulse signal is emitted to the same target through and the reflected wave from the target is received. Received signal processor 70
Is a device which is a main part of the present invention for obtaining coordinates of a target in a distance direction (radar direction) and a cross range direction, which are supposed to be performing a motion including at least a rotary motion based on a signal received under such a condition. Hereinafter, the function of the processing device 70 will be described in detail with reference to FIGS.

The output signal of the receiver 50, that is, the received signal corresponding to each reflected wave for each of the distance portions of the target (correctly this demodulated signal) is the frequency analyzer 71 of the received signal processing device 70 and the target. Each is added in parallel to the center position calculation circuit 72.

The frequency analyzer 70 is a known signal analyzer that decomposes the received signal into so-called Doppler frequency-decomposed signals having a plurality of filters that decompose the received signal into signals for each frequency component based on the frequency shift due to the Doppler effect, As a result, from the frequency analyzer 71, the distance in the pulse signal emission direction with respect to the target that is performing the motion including the rotary motion (the distance from the radar device to the separated portion of the target).
With R and the decomposed Doppler frequency fd as parameters, a signal whose shape is simulated is output. For example, suppose that the target is a ship, which is yawing as shown in FIG. 2 while advancing in a direction forming an angle θ with the x axis (direction orthogonal to the radar direction) while yawing. From the frequency analyzer 71, a signal having the content shown in FIG. 3 for the shape of the ship is output. That is, this signal has a content corresponding to the rotational movement in the direction of arrow a in the yawing (see FIG. 2) corresponding to this, as shown by the solid line a in FIG. Corresponding to the rotational movement in the b direction (see FIG. 2), the content shown by the broken line b in FIG. 3 is correspondingly provided. As described above, the shape represented here is a pseudo-shape determined based on the rotation mode of the target at a certain time, and strictly speaking, the speed of the target vibration (in this example, the yawing of the ship). Also, the size of the Doppler frequency fd, that is, the display size in the vertical axis direction in FIG.

Further, in parallel with this, the target center position calculation circuit 72 that receives the received signal is based on the received signal corresponding to each reflected wave for each of the plurality of target distance portions as described above. , A circuit for obtaining the rotational movement center position of the target at any time as the distance and azimuth from the radar device. For example, if the target is a ship as shown in Fig. 2,
Based on the change in the received signal due to the yawing in the a direction and the b direction described above, the center position of the ship itself is obtained. The information indicating the desired rotational movement center position of the target thus obtained is sequentially stored in the memory 73 of the next stage. Then, the trajectory of the target is stored in the memory 73 following the progress of the target.

There are various methods for obtaining the rotational movement center position described above. For example, as in the case of a target tracking device, the received target echo is opened at different positions on the time axis for the same time. A division in which two gates are set, and the spatial center position of the target is detected based on the positions on the time axis of these two gates where the signal level difference of the target echo output through these two gates is "0". It is possible to adopt the gate method.

The tracking circuit 74 is a well-known circuit that generally calculates the traveling direction of the target based on the positional information of the target obtained from continuous or intermittent target observation, and here, the target stored in the memory 73 is used. Based on a plurality of pieces of information indicating the past rotational movement center positions of, the substantial traveling direction of the target performing the movement including the rotational movement is calculated. The information indicating the traveling direction of the target thus calculated is fd / x converted together with the signal output from the frequency analyzer 71, that is, the signal indicating the target shape in a pseudo manner using the distance R and the Doppler frequency fd as parameters. Added to circuit 75.

The fd / x conversion circuit 75 converts the information obtained as the Doppler frequency fd by the frequency analyzer 71 into a cross range direction distance value (value of x) based on the above-mentioned principle. That is, the fd / x conversion circuit 75 is the tracking circuit 74 described above.
Based on the information indicating the advancing direction of the target added from the above, the angle formed by the advancing direction and the cross range direction, that is, the angle θ in the example shown in FIG. 2 is obtained and this is substituted into the above equation (5). The value of (2ωr / λ), which is a proportional coefficient between the Doppler frequency fd and the distance x in the cross range direction, is first estimated, and then the Doppler frequency fd added from the frequency analyzer 71 based on the designated coefficient value. The value of is converted into the value of the distance x in the cross range direction sequentially. As a result, the fd / x conversion circuit 75 outputs information indicating the shape of the target with parameters such as the distance R in the radar direction and the distance x in the cross range direction, which can directly represent the size, as described above. Will be done. Note that the values of R and R ₀ used when estimating the value of the coefficient (2ωr / λ) based on the equation (5), that is, the distance R from the radar to an arbitrary point of the target and the rotation of the same target from the radar. Distance to center R ₀
Is calculated based on the time difference between the reception echo and the transmission pulse at any time in the above-mentioned processing of the reception signal processing device 70 as described in the above principle, and these values are also not shown in the figure. Is added to the fd / x conversion circuit 75 through.

As described above, in the display device 60 which receives the signal subjected to such processing by the received signal processing device 70, for example, the distance R in the radar direction is represented by the horizontal axis and the distance x in the cross range direction is represented by the vertical axis. The image is displayed on the basis of the above, and it becomes possible to faithfully reproduce the shape of the target as shown in FIG. 2 above, as shown in FIG.

Thus, according to the radar apparatus of this embodiment, it is possible to obtain a high-resolution radar image that matches the physical shape of the target.

When observing such a moving target, the Doppler frequency caused by the movement of the target appears as an offset of the center frequency when performing the frequency analysis, but this is an obstacle to the above display. There is no.

Further, in the above-described embodiment, nothing was specified about this transmission / reception method except that transmission / reception was performed with a distance resolution capable of separating the target into a plurality of distance portions, but a so-called monopulse method using a monopulse antenna as the antenna 40, etc. If the angle measurement is performed in combination with, the target rotation center position and the like described above can be obtained more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a radar device according to the present invention, FIG. 2 is an explanatory diagram schematically showing an example of a target to be measured by the radar device of the present invention, and FIG. FIG. 4 is a diagram showing an example of a radar image obtained by frequency-analyzing a received signal corresponding to the target example shown in FIG. 2, and FIG. 4 is an example of a radar image obtained by the apparatus of the embodiment of the present invention. 2 is a diagram showing a radar image obtained corresponding to the target example shown in FIG. 2, FIG. 5 is a block diagram showing a general configuration of a conventional radar device, and FIG. 6 is a diagram for explaining the principle of the present invention. FIG. 10 ... Highly stable oscillator, 20 ... Transmitter, 30 ... Transceiver, 40 ... Antenna, 50 ... Receiver, 60 ... Display, 70 ...
... Reception signal processing device, 71 ... Frequency analyzer, 72 ... Target center position calculation circuit, 73 ... Memory, 74 ... Tracking circuit, 75
...... Fd / x conversion circuit.

Claims (1)

[Claims] 1. Radiation of a pulse signal to the target through the antenna and a reflected wave from the target with a distance resolution capable of separating the target into a plurality of distance portions with respect to the target performing at least a rotational motion. In the radar device for receiving and displaying and outputting the physical shape of the target based on the mode of the received reflected wave, the received signal corresponding to each reflected wave for each of the separated distance parts is Doppler frequency decomposed. First calculation means for performing a calculation to output a plurality of first paired data consisting of the distance in the pulse signal radiation direction for each distance portion and the decomposed Doppler frequency, and each reflected wave for each distance portion A second calculation means for sequentially calculating and outputting the center position of the target rotational motion based on the arrangement of the positions of the strong strength point and a plurality of strong strength points of the A storage unit that sequentially stores the position information indicating the center position of the output rotational movement of the target, and the moving direction of the target is calculated based on the stored position information, and the calculated moving direction of the target And third calculating means for calculating and outputting a proportional coefficient between the value of the Doppler frequency and the value in the cross range direction from an inclination angle between the cross range direction which is a direction orthogonal to the distance in the pulse signal emission direction. Based on the proportional coefficient output from the third calculating means,
Fourth calculating means for performing a calculation for converting the value of each Doppler frequency of the plurality of first paired data into the distance in the cross range direction and outputting the plurality of converted second paired data. And display means for displaying the physical shape of the target based on the position determined by the distance in the pulse signal emission direction and the distance in the cross range direction indicated by the plurality of second paired data. A radar device characterized by the above.