JPH0693029B2 - Radar device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device that improves cross-range resolution by utilizing the Doppler effect due to movement of a target and changes in attitude angle, that is, rotation.

[Conventional technology]

Conventionally, the operation principle of this type of radar device is described in, for example, the document MJ.
Prickett and CC Chen's "Principles of Inverse S"
Synthetic Aperture Radar (ISAR) Imaging-Principle of Imaging by Inverse Synthetic Aperture Radar "EASCON '80, PP 340-345.

FIG. 10 is a block diagram showing a conventional radar device constructed according to the above document. In the figure, 1 is a transmitter,
2 is a transmission / reception switch, 3 is a transmitting / receiving antenna, 4 is a receiver,
Reference numeral 5 is a range compression means, 6 is a two-dimensional storage means (hereinafter referred to as 2D storage means), 7 is means for compensating for a target motion (hereinafter referred to as motion compensation means), 8 is a cross-range compression means, and 9 is A two-dimensional display buffer (hereinafter referred to as a 2D display buffer) 10 is a monitor television (monitor TV).

FIG. 2 is a diagram showing the geometry of the radar device. In the figure, 16 is a radar device and 17 is a target. Also, in the figure, the Rng axis represents the range direction, the X axis represents the azimuth direction, and the Y axis represents the elevation direction.

3 and 4 are diagrams for explaining the movement of the target as seen from the radar device.

Next, the operation of the conventional radar device will be described.
Here, the target 17 (for example, a ship) is moving at a speed v _T in the X-axis direction, and at this time, the maximum roll angle is ± θ ₀ and its cycle is T ₀ , as shown in FIG. .

First, the high frequency pulse signal generated by the transmitter 1 is emitted from the transmission / reception antenna 3 toward the target 17 via the transmission / reception switch 2. The radar echo reflected by the target 17 is received again as a reception signal by the transmission / reception antenna 3, and is input to the receiver 4 via the transmission / reception switcher 2. The reception signal amplified and phase-detected by the receiver 4 is input to the range compression means 5, where a process for improving range resolution, that is, pulse compression is performed. The received signal after range compression is stored in the 2D storage means 6 according to the range number k and the pulse hit number 1. Following the range compression, in order to remove the random component from the motion of the target 17, the received signal is read from the 2D storage means 6 and the motion compensating means 7 is set so that the Doppler frequency at the center point of the target 17 becomes zero. Phase compensation and rearrangement of range bins are performed according to, and stored again in the 2D storage means 6. The received signal after such compensation is input to the cross range compression means 8, and the cross range resolution is improved by utilizing the Doppler frequency difference.

Next, the Doppler effect due to changes in the attitude angle of the target 17, here the roll angle, and the azimuth direction of the target 17 (X-axis direction)
The Doppler effect due to the movement of the will be described. Goal 17
As shown in FIG. 3, it is assumed that rolling is performed within a period T ₀ and a roll angle ± θ ₀ . At this time, time t
The roll angle θ _R (t) at Therefore, the Toppler frequency θ _R (t) due to the rotation of the point separated by the radius r ₀ from the center of rotation is Given in. In this type of radar device, θ _R (t) <<
Since 1, t << T ₀ , θ _R (t) is Can be approximated by In the above formula (3), ry is ry = r ₀ co
sθ _R (t) represents the length in the Y-axis direction. That is, by measuring the Doppler frequency θ _R (t),
The position ry on the Y axis can be obtained. When the frequency resolution of the FFT (Fast Fourier Transform) of the cross range compression means 8 is Δ, the cross range (Y-axis direction in this example) resolution Δry is Can be achieved.

When the target 17 is moving in the X-axis direction at a speed v _T ,
Doppler frequency at the point rx away from the center of the target 17 in the X-axis direction Is the distance R ₀ between the radar device 16 and the center point of the target 17, Given in. Yotsutte, Doppler frequency The position rx on the X-axis can be obtained by measuring. When the FFT frequency resolution of the cross-range compression means 8 is Δ, the cross-range (X-axis direction in this example) resolution Δrx is Can be achieved.

As described above, the high-resolution received signals in both the range direction and the cross range direction are stored in the 2D display buffer 9 and are converted into a composite video signal whose power is proportional to the luminance, and the two-dimensional image is obtained. Monitor as a radar image
Displayed on TV 10.

[Problems to be solved by the invention]

Since the above-described conventional radar device is configured as described above, since the cross range direction can be increased in resolution in only one of the azimuth direction (X axis) and the elevation direction (Y axis), it is essentially a three-dimensional object. However, there is a problem that the target 17, which is the above, can only be observed as a two-dimensional object in the range direction and the azimuth direction (or the elevation direction).

The present invention has been made to solve such a problem, and enables high resolution in two cross-range directions of an azimuth direction and an elevation direction, and a range direction is added to this to make a target three-dimensional. The purpose of the invention is to obtain a radar device that enables observation.

[Means for solving problems]

The radar device according to the present invention divides a received signal into a set of data used for elevation compression processing and a set of data used for azimuth compression processing for each range / bin in order to efficiently store them. Dimensional storage means added,
Data for elevation compression is read from the three-dimensional storage means, elevation compression means for performing elevation compression, azimuth compression means for performing azimuth compression on the data after elevation compression, and elevation for each range bin. A three-dimensional display buffer is added to store the high-resolution processed results in both the syon direction and the azimuth direction and convert the processed results into a three-dimensional radar image.

[Action]

In the radar device of this invention, elevation compression is performed by utilizing the Doppler effect due to the change of the target roll angle or pitch angle, and further azimuth compression is performed by utilizing the Doppler effect due to the movement of the target in the azimuth direction. Thus, it becomes possible to observe the three-dimensional target in the elevation direction, the azimuth direction, and the range direction together with the range compression.

〔Example〕

FIG. 1 is a block diagram showing a radar apparatus according to an embodiment of the present invention. The same or corresponding parts as those of the conventional apparatus shown in FIG. The description is omitted. In the figure, 11 is a three-dimensional memory means (hereinafter, referred to as a 3D storage means), 12 Erebeshiyon compression means (E _L compressing means), azimuth compression means (A _Z compression means) 13, 14 3-dimensional display buffer (Hereinafter, referred to as 3D display buffer), 15 is a two-dimensional cross-range compression means.

In the radar device shown in FIG. 1, the target 17 is the second
X a point where the radar apparatus 16 Distance R ₀ away as shown in FIG.
It is moving at a velocity v _T in the axial direction, at which time the target 17
At T ₀ , it is assumed that the roll angle is ± θ ₀ . Doppler frequency θ _R due to rolling at this time
(T) is given by the above equation (3) as described above. Therefore, if the desired cross range resolution in the elevation direction, that is, the Y-axis direction is Δry, the required Doppler frequency resolution Δθ _R is Becomes If the length of the target 17 in the Y-axis direction is ΔRy, the required Doppler frequency bandwidth Bθ _R is Therefore, the sampling period Δty and the observation time ΔTy during elevation compression are Becomes Also, the Doppler frequency due to movement of the target Is given by the above equation (5), the azimuth direction,
That is, the desired cross range resolution in the X-axis direction is Δrx,
If the target 17 length in the X-axis direction is ΔRx, the required Doppler frequency resolution Δ And Doppler frequency bandwidth Is Therefore, the sampling period Δtx and the observation time ΔTx during azimuth compression are Becomes Generally, in the application of this type of radar device,
It is considered that Ty ≤ Δtx and T ₀ ≤ Δtx hold. For example, λ = 0.03m, θ ₀ = 2 °, T ₀ = 0.5s, △ rx ＝ △ ry = 1m, △ Rx
= 100m, △ Ry ＝ 20m, v _T ＝ 20kt, R ₀ ＝ 50Km, △ ty, △ Ty, △ tx, △ Tx are Becomes

FIG. 5 is a timing chart showing sampling rates at the time of elevation compression and azimuth compression in the radar apparatus of FIG. 1, and FIG. 6 is a logical structure of 3D storage means and 3D display buffer in the radar apparatus of FIG. FIG. 7, FIG. 7 and FIG. 8 are flow charts showing an elevation compression processing procedure and an azimuth compression processing procedure in the radar apparatus of FIG. 1, respectively.

Next, the operation of the radar apparatus according to the embodiment of the present invention shown in FIG. 1 will be described in detail. A high frequency pulse signal having a pulse repetition period (sampling period) Δty generated in the transmitter 1 is radiated from the transmission / reception antenna 3 toward the target 17 via the transmission / reception switch 2. The signal reflected by the target 17 is received by the transmission / reception antenna 3, and the transmission / reception switch 2
Then, the signal is input to the receiver 4 via the above, amplified and phase-detected, and then input to the range compression means 5. The reception signal that has been range-compressed by the range compression means 5 is stored in the 3D storage means 11. As described above, the elevation compression and the azimuth compression differ greatly in sampling rate (sampling period) Δty and Δtx suitable for the processing. Therefore, the 3D storage means 11 stores data three-dimensionally in the following procedure to facilitate the handling of data at two sampling rates.

Procedure 1 A received signal with a sampling period Δty, which is a pulse repetition period, is divided into partial sections for each azimuth compression sampling rate Δtx (= T ₀ ), as shown in FIG. 5, and 1 = for each partial section. Numbers 1,2,3, ..., L. However, L
= ΔTx / Δtx.

Procedure 2 Data for the observation time ΔTy is extracted for each sub-section, and m = 1, 2, 3, ..., M is numbered for each transmission pulse. However, M = ΔTy / Δty. This is performed for all the sub-sections 1 = 1, 2, 3, ..., L.

Step 3 For each transmission pulse, k = 1,2,3, for each range bin
,, K are numbered and s in the array s of the 3D storage means 11
Store in (m, l, k). k = 1,2, ..., K, l = 1,2, ..., L,
Perform all of m = 1,2, ..., M.

Next, the motion compensating means 7 reads s (m, l, k) as a received signal from the 3D storage means 11, performs phase compensation so that the Doppler frequency at the center point of the target 17 becomes 0, and also performs range walk compensation. 3D storage means 11
, And store it as s (m, l, k). After completion of the motion compensation by the motion compensating means 7, the elevation compressing means 12 reads s (m, l, k) from the 3D storage means 11, and performs the elevation compression by the FFT algorithm for the m-axis direction, that is, the sampling rate Δty. To do. The processing flow of this elevation compression is shown in the flow chart of FIG.

Now, the received signal S ₁ (m,
l, k) is However, m = 1,2, ..., M 1 = 1,2, ..., L k = 1,2, ..., K and are stored in the 3D storage unit 11. The elevation-compressed S ₁ (m, l, k) is read by the azimuth compression means 13, and this time in the l-axis direction, that is, the sampling rate Δ.
Azimuth compression is performed by the FFT algorithm for tx = T ₀ . The processing flow of this azimuth compression is shown in the flow chart of FIG. Received signal S ₂ (m, l, k) compressed in both elevation and azimuth directions
Is However, m = 1,2, ..., M l = 1,2, ..., L k = 1,2, ..., K, and after being transferred to the 3D display buffer 14 and converted to the image brightness proportional to the power. , Monitor as composite video signal
It is input to the TV 10 and displayed. At this time, S ₂ (m, l,
As shown in FIG. 6, k) represents the radar cross-sectional area of each cell when the target 17 is divided into small cells along the three axes of elevation direction, azimuth direction and range direction.

FIG. 9 is a block diagram showing a radar apparatus according to another embodiment of the present invention. In the figure, 9 is a two-dimensional display buffer (2D display buffer), 18 is a display plane selecting means, and other reference numerals are the same as those shown in FIG. The radar device shown in FIG. 9 is used for a target such as a ship.
This is especially effective when it is not possible to collect valid data in the range direction, such as when observing 17 directly from the side.At this time, the elevation direction is the vertical axis and the azimuth direction is the horizontal direction, as in optical photography. The shape of the target 17 on the two-dimensional plane as the axis is obtained.

〔The invention's effect〕

As described above, the present invention, in the radar device,
After the elevation compression is performed by using the change of the roll angle that is the target posture angle, the means for performing the azimuth compression by using the Doppler effect by the movement of the target is added, so the elevation direction and the azimuth It has an excellent effect that the resolution can be improved in both the direction and the two-dimensional cross-range compression, and the target can be observed as a three-dimensional object in combination with the range direction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a radar device according to an embodiment of the present invention, FIG. 2 is a diagram showing the geometry of the radar device, and FIGS. 3 and 4 are diagrams for explaining the movement of a target viewed from the radar device. 5 and FIG. 5 are timing charts showing sampling rates at the time of elevation compression and azimuth compression in the radar apparatus of FIG. 1, and FIG. 6 is 3D storage means and 3D in the radar apparatus of FIG.
FIG. 7 and FIG. 8 showing the logical structure of the display buffer are a flow chart showing the processing procedure of elevation compression and the processing procedure of azimuth compression in the radar apparatus of FIG. 1, and FIG. FIG. 10 is a block configuration diagram showing a radar device according to another embodiment, and FIG. 10 is a block configuration diagram showing a conventional radar device. In the figure, 1 ... transmitter, 2 ... transmission / reception switch, 3 ...
... Transmission / reception antenna, 4 ... Receiver, 5 ... range compression means, 6 ... 2D storage means, 7 ... motion compensation means, 8 ... cross range compression means, 9 ... 2D display buffer, 10 ... monitor・ TV (monitor TV), 11 …… 3D storage means, 12 ……
Erebeshiyon compression means (E _L compression means), 13 ...... azimuth compression means (A _Z compression means), 14 ...... 3D display buffer, 15
...... Two-dimensional cross-range compression means, 16 …… Radar device,
17 ... Target, 18 ... Display plane selection means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A movement and attitude angle of a target, that is, a pitch,
In a radar device that improves cross-range resolution by utilizing the Doppler effect caused by changes in roll and yaw, the Doppler effect due to the roll motion of the target is assumed on the premise that the target performs a combined motion of roll motion and straight or yaw motion. And the Doppler effect due to the straight movement or yaw movement of the target, and the elevation compression means for repeatedly performing the resolution enhancement in the elevation direction for a plurality of cycles by using the data in one cycle of the target roll movement, An azimuth compression unit that performs high resolution in the azimuth direction by utilizing the Doppler effect of the target straight movement or yaw motion for the data whose resolution has been increased in the elevation direction by the elevation compression unit,
Range direction, elevation direction and azimuth direction 3
The axis is provided with a three-dimensional storage means for three-dimensionally storing the received signal and an intermediate result in the processing process thereof, and a three-dimensional display buffer for storing the final result and converting it into a composite video signal. Radar device. 2. An arbitrary two axes are selected from a three-dimensional space determined by the three axes of the range direction, the elevation direction and the azimuth direction, and the range direction and the azimuth direction, the range direction and the elevation direction, or the azimuth direction and the elevation direction. Display plane selecting means for selecting a plane determined by two axes of directions, and a two-dimensional display buffer for extracting and storing display data relating to the plane selected by the display plane selecting means from the three-dimensional display buffer. The radar device according to claim 1, which is characterized in that.