JP2002071795A - Radar device for acquiring and tracking target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately acquire and track targets even in a multipath environment. SOLUTION: Radio waves are transmitted and received by an antenna unit 1, and the target is detected by a target detecting circuit 2 through the use of a reception signal received by the antenna unit 1. An off-bore-site angle when the target is detected is obtained by a angle measuring computing circuit 3, and the location of the target is specified and displayed on a display 5 on the basis of an azimuth angle and an elevation angle obtained from the result of target detection and the off-bore-site angle. Here, by detecting the velocity component of the target by a velocity detecting circuit 7 through the use of the result of target detection and by performing filter processing by a multipath removal computing circuit 8 through the use of the result of velocity detection and the result of target detection, indirect wave components among reflected components from the target are suppressed, and the elevation angle is recomputed, outputted to the display 5, selectively switched, and displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a target acquisition / tracking radar apparatus for detecting a target in a multipath environment and acquiring position information of the target with high accuracy.

[0002]

2. Description of the Related Art As is well known, in a target acquisition / tracking radar apparatus, a reflected echo of a target directly arrives at an antenna apparatus, and an indirect wave which is once reflected on the ground or the sea surface before reaching the antenna apparatus. Waves (multipath waves) are mixed and received. For this reason, the conventional radar device is designed so that the beam width of the antenna device is reduced as much as possible and the side lobe level is reduced. That is, by making the angle difference between the indirect wave and the direct wave incident on the antenna device larger with respect to the beam width of the antenna device, and by reducing the echo sensitivity incident from a direction other than the off boresight direction. In addition, the influence of the indirect wave is reduced (suppressed).

However, there is a limit to narrowing the beam width of the antenna device or lowering the side lobe level. When the target projectile flies at an extremely low altitude, or when the side lobe level of the antenna device is sufficiently reduced. If the target position cannot be lowered and the indirect wave is easily received, the position of the target cannot be accurately detected, and the target may be lost.

[0004]

As described above, the conventional target acquisition / tracking radar apparatus has a problem that the target position detection accuracy is deteriorated in an environment where multipath exists. In addition, when the target flies at a low altitude or when the antenna device has a high side lobe level and is likely to receive an indirect wave, the position of the target cannot be accurately detected, and the target is lost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and a highly accurate angle measurement can be performed even in a multipath environment, thereby enabling a target to be tracked without losing a target. An object of the present invention is to provide a radar device for acquisition and tracking.

[0006]

In order to achieve the above object, a target acquisition / tracking radar device according to the present invention receives a reflected wave by transmitting / receiving a radio wave by an antenna device,
A radar device that captures a target from this received signal, performs angle measurement calculation, obtains the position of the target, an azimuth angle, an elevation angle, and controls a beam pointing direction of the antenna device in accordance with a change in the position of the target, Target distance detecting means for detecting a distance to a target by using a reception signal received by the antenna device; speed detecting means for detecting a target speed component using a detection result of the target distance detecting means; An indirect wave suppressing unit that suppresses an indirect wave component of a reflected signal component from a target by performing a filtering process using a detection result of the detecting unit and a detection result of the target distance detecting unit; A target elevation angle is obtained from the received signal in which the indirect wave component has been suppressed by the suppression means.

According to the above configuration, since the indirect wave component is suppressed by the indirect wave suppressing means from the reflected signal component from the target, the target elevation angle is obtained. Will be able to do it.

The indirect wave suppression means uses the time interval for tracking the target, the target distance detection result, and the target speed detection result to determine the period of the phase relationship between the direct wave reflected from the target and the indirect wave. The indirect wave component can be suppressed by calculating and calculating the weight based on this cycle, and by weighting and adding the target position detection results sequentially obtained with the weight.

Further, using the target position detection result,
Of the reflected signal components from the target, the arrival direction of the indirect wave component is calculated, and the reception direction of the indirect wave is reduced by forming a null in the transmission / reception beam of the antenna device with respect to the arrival direction of the indirect wave. Will be able to do it.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a first embodiment of a target acquisition / tracking radar apparatus according to the present invention. This radar device comprises an antenna device 1, a target detection circuit 2, an angle calculation circuit 3, a beam control circuit 4, a display 5, a tracking processing circuit 6, a speed detection circuit 7, and a multipath removal calculation circuit 8.

A transmission wave transmitted from the antenna device 1 is reflected by a target and is received by the antenna device 1 as a reception echo. The received signal received by the antenna device 1 is converted into a monopulse signal (Σ (sum signal), Δ
AZ (azimuth angle component difference signal) and ΔEL (elevation angle component difference signal) are output. At this time, the azimuth angle and elevation angle for transmitting and receiving radio waves to and from the space are beam-formed according to the beam control circuit 4.

Of these monopulse signals, the Σ signal is 2
One is input to the target detection circuit 2. The target detection circuit 2 performs threshold detection on the Σ signal to determine the presence or absence of a target. When the target is detected, a detection timing signal is output to the angle measurement arithmetic circuit 3.
Further, it outputs the target distance information to the display 5.

The angle calculating circuit 3 performs angle measuring using a monopulse signal input from the antenna device 1 in synchronization with the detection timing input from the target detecting circuit 2. By this angle measurement calculation, the detected target off-bore sight angles (Δθ _AZ and Δθ _EL ) are obtained and output to the display 5.

The display unit 5 has an off-bore sight angle (Δθ _AZ and Δθ _EL ) input from the angle measurement operation circuit 3 and a beam scanning angle (θ _AZ and θ _EL ) input from the beam control circuit 4.
Calculates the azimuth and elevation of the target by adding
The target position information is displayed together with the target distance information (R) input from the target detection circuit 2. Further, the information of the azimuth angle, elevation angle and distance of these targets is sequentially stored in the tracking processing circuit 6.
Output to

The tracking processing circuit 6 predicts the next position of the target from information on the azimuth, elevation and distance of the target input from the display 5 and obtains a beam pointing angle corresponding to the direction, thereby obtaining a beam control circuit. 4 is output.

On the other hand, the target distance information (R) output from the target detection circuit 2 is output to the speed detection circuit 7. The speed detection circuit 7 calculates the relative speed (v) of the target by differentiating the target distance or the like. The obtained relative speed information of the target is output to the multipath removal arithmetic circuit 8.

In the multipath removal operation circuit 8, the target
The target distance information (R) input from the detection circuit 2 and the speed detection
In addition to the target relative speed (v) input from the output circuit 7,
Tracking data rate (T) set as
Antenna height (H_A), Sequentially input from the display 5
Elevation data (elevation angle 1: θ_EL1) From multi
Eliminates the effects of path components, resulting in the target
Angle data (elevation angle 2: θ _EL2) Is generated and output to the display 5
I do. The display 5 displays the target position information as the target position information.
Θ as angle data_EL1Or θ_EL2Select one of
indicate.

FIG. 2 shows a specific circuit configuration of the multipath removal operation circuit 8. This multipath removal operation circuit 8
Is adapted to a type of transversal filter, the multiplier 8 ₁₁ to 8 _1n, delayer _{8 21 ~8 2 (n-1} ), the adder 8 ₃₁ -
8 3 _(n-1) and consists of the weight calculation circuit 8 _4.

That is, the input signal (target elevation angle 1)
(Θ_EL1)) Is the delay unit 8_{twenty one}~ 8_{2 (n-1)}Tracking data
Rate (Z^-1), And each input and output is multiplied by
Calculator 8₁₁~ 8 _1nSent to On the other hand, the weight calculation circuit 8
In 4, the input target speed information (v) and distance information
(R), tracking data rate (T), antenna altitude
(H_A) And the complex weight
(W₁~ W_n) Is calculated, and the multiplier 8₁₁~ 8 _1nSet to
You. Each multiplier 8₁₁~ 8_1nAnd the complex weight (W₁~ W_n)
Is weighted by the adder 8₃₁~ 8_{3 (n-1)}By
And the output signal (target elevation angle 2 (θ_EL2))When
Become.

In the above configuration, the processing content of the multipath removal operation will be described with reference to FIG.

FIG. 3 shows an example of a path where a direct wave and an indirect wave from a target reach the antenna of the antenna device 1, respectively, where A is the antenna position, T is the target position, S is the multipath reflection point, θ _EL is the target elevation angle, φ is the estimated angle of the multipath wave, R ₀ is the distance between the antenna position A and the target position T, a is the distance between the target position T and the multipath reflection point S, b
Is the distance between the antenna position A and the multipath reflection point S, l _a
Is the horizontal distance between the target position T and the multipath reflection point S, l _b
Is the horizontal distance between the antenna position A and the multipath reflection point S,
H _A indicates the antenna altitude, H _T indicates the target altitude, and v _R indicates the relative speed of the target.

First, a: b = H _T : H _A

(Equation 1) Next, l _a: from H _A: l _b = H _T

(Equation 2) From equation (1)

(Equation 3) Can be derived from Equation (2).

(Equation 4) Can be derived. Equation (4) is

(Equation 5) Can be expressed as

Here,

(Equation 6) Is established, so if equation (5) is substituted into equation (6),

(Equation 7) And from equations (3) and (7)

(Equation 8) Becomes When the equation (8) is expanded in series,

(Equation 9) Therefore, the path difference Δl ₀ between the direct wave and the indirect wave is

(Equation 10) Can be expressed as

Approximating equation (9) up to the second term of the series expansion,

[Equation 11] Becomes Here, the target height H _T is constant, the target distance R approaches R-r (where, theta _EL approximates a constant), the path difference .DELTA.l ₁ of the direct wave and the indirect wave,

(Equation 12) Becomes From equations (11) and (12),

(Equation 13) Becomes

The target relative speed v _R is

[Equation 14] It is. Therefore, in the multipath removal operation circuit 8,

(Equation 15) Is calculated by using θEL, R0, and HA from Expressions (13) and (14).

That is, one cycle of the amplitude / phase fluctuation of the received signal caused by the multipath is the observation time (t) represented by the equation (14) where n = 1 in the case of the equation (15). , The multipath removal operation circuit 8 obtains t that satisfies the relationship of the expression (15), and obtains t from the relationship with the tracking data rate (T).

(Equation 16) An integer value M is obtained. For example, assuming that the complex weight W _i is set in the multipath operation circuit 8, i = 1 to M
For K (K = 1, 2, 3,...), A value having a desired weight is set, and for i> M · K, _Wi = 0. As a result, the variation of the amplitude and phase of the periodic reception signal due to the multipath for K cycles is weighted and added, and the periodic variation component can be suppressed.

Therefore, according to the radar device having the above-described configuration, the periodic echo due to multipath can be suppressed in the reflected echo from the target, which is a composite signal of the direct wave and the indirect wave, and the target is lost. Without this, the position information at the time of tracking can be detected with high accuracy.

FIG. 4 is a block diagram showing the configuration of a second embodiment of the radar system for target acquisition and tracking according to the present invention. This radar device has a configuration in which a multipath incident angle calculation circuit 9 and a null beam phase calculation circuit 10 are added to the configuration of the first embodiment shown in FIG. For this reason,
4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here.

In FIG. 4, a multipath incident angle calculation circuit 9 uses a target distance information input from the target detection circuit 2, target elevation angle data output from the multipath removal calculation circuit 8, and antenna elevation information to perform multipath incidence angle calculation. Is used to calculate the angle at which the multipath is incident, and the angle region at which the multipath is incident is defined as a null forming angle.
Output to

The null beam phase calculation circuit 10 uses the beam control signal input from the beam control circuit 4 and the null formation angle input from the multi-path incident angle calculation circuit 9 to form, for example, an array of antenna devices 1 in an array. Each set phase of the antenna element is calculated, and anti-clutter is formed in the angle region where the multipath is incident. still,
About Anti-clutter, THE TRANSACTIONS OF
THE IEICE. VOL.E 73, NO2 FEBRUARY 1990, P245-249, "
The details are described in "Side Lobe Suppression with Phase Weight Only" or the like, and the description is omitted here.

With reference to the example shown in FIG. 3 in the above configuration, the multipath incident angle calculation processing which is a feature of this embodiment will be described.

In FIG. 3, the multipath incident angle φ can be obtained by the following equation.

[Equation 17] Therefore, the multipath incidence angle calculating circuit 9, the target distance information R ₀ from the target detection circuit 2 receives the target elevation angle data θEL antenna altitude information H _A from the multipath removal operation circuit 8, using the equation (9) Is calculated by substituting into equation (17). Thereby, the multipath incident angle φ can be obtained.

A null beam control signal is generated by the null beam phase calculation circuit 10 for the multipath incident angle φ obtained in this manner so as to form a null, and the antenna device 1
Control the excitation phase distribution of. Thereby, the reception sensitivity of the multipath wave can be suppressed, and the influence of the multipath can be reduced.

In the case of a conventional radar device, as described above,
In an environment where a multipath exists, a composite signal in which a direct wave and an indirect wave are mixed becomes a reception echo, so that the error of the off-bore sight angle calculated by the angle measurement circuit 3 increases,
In some cases, not only the accuracy of target position detection is deteriorated, but also the target position is erroneously recognized, the tracking processing circuit does not operate normally, and the target cannot be tracked. On the other hand, in the radar device having the above configuration, in the reflected echo from the target, which is a composite signal of the direct wave and the indirect wave (multipath wave),
Since the indirect wave is suppressed and the direct wave component is extracted, the position information at the time of tracking can be detected with high accuracy without losing the target.

[0036]

As described above, according to the present invention, it is possible to perform a highly accurate angle measurement operation even in a multipath environment, thereby enabling a target to be tracked without losing a target. A radar device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a target acquisition / tracking radar apparatus according to the present invention.

FIG. 2 is an exemplary block diagram showing a specific circuit configuration of a multipath removal arithmetic circuit which is a main part of the embodiment;

FIG. 3 is a diagram showing an example of a path through which a direct wave and an indirect wave from a target reach the antenna of the antenna device 1 for explaining the processing content of the embodiment.

FIG. 4 is a block diagram showing a configuration of a target acquisition / tracking radar apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... antenna device 2 ... target detection circuit 3 ... goniometric calculation circuit 4 ... beam control circuit 5 ... display 6 ... tracking processing circuit 7 ... velocity detection circuit 8 ... multipath rejection arithmetic circuit 8 ₁₁ to 8 _1n ... multiplier 8 ₂₁ to 8 _{2 (n-1)} ... delay unit 8 ₃₁ to 8 _{3 (n-1)} ... adder 8 ₄ ... weight calculation circuit 9 ... multi-path incident angle calculation circuit 10 ... null beam phase calculation circuit

Claims (3)

[Claims] 1. A reflected wave is received by transmitting / receiving a radio wave by an antenna device, a target is captured from the received signal, and angle measurement is performed to obtain a target position, an azimuth angle, and an elevation angle. In a target acquisition and tracking radar device that tracks a target by controlling the beam directing direction of the antenna device corresponding to the target distance, a target distance that detects a distance to the target using a reception signal received by the antenna device Detecting means; speed detecting means for detecting a target speed component using the detection result of the target distance detecting means; filtering processing using the detection result of the speed detecting means and the detection result of the target distance detecting means The indirect wave suppressing means for suppressing the indirect wave component of the reflected signal component from the target, and the received signal in which the indirect wave component is suppressed by the indirect wave suppressing means. Target acquisition and tracking radar apparatus and obtains the elevation angle of the target. 2. The method according to claim 1, wherein the indirect wave suppressing unit uses a time interval for tracking the target, a target distance detection result, and a target speed detection result to determine a phase relationship between the direct wave reflected from the target and the indirect wave. Phase period calculating means for calculating a period, and a weight is calculated based on the period calculated by the phase period calculating means, and the indirect wave component is suppressed by weighting and adding target position detection results sequentially obtained with the weight. 2. The target acquisition / tracking radar apparatus according to claim 1, further comprising a filter processing unit. 3. An indirect wave arrival direction calculation means for calculating an arrival direction of an indirect wave component among reflected signal components from a target using the target position detection result, and an indirect wave arrival direction obtained by the means. 2. A target acquisition / tracking radar apparatus according to claim 1, further comprising a null beam forming means for forming a null in a transmission / reception beam of said antenna apparatus in an arrival direction of said antenna apparatus.