JPH07321546A - Radar system - Google Patents

Abstract

PURPOSE:To reduce a cross sectional area of a radar at a small offset angle by adopting a curved face for an array antenna so as to attain wide angle beam scanning. CONSTITUTION:In the radar system in which an array antenna 1 is offset by a prescribed angle theta with respect to an objective direction for the purpose of reducing a cross sectional area of the radar, a curves face is adopted for the array antenna 1. An exciting receiver 5 generates a transmission signal, the signal is sent from elements 3 arranged along a structural base 2 of the array antenna 1 and reflected on an object, the reflected wave is received by the array antenna 1 with a beam directivity based on phase information given by a beam controller 4 and a signal processing unit 6 provides an output of an object signal via the exciting receiver 5. Then wide angle beam scanning of + or -60 deg. or over is attained by adopting the curved face for the array antenna 1. Moreover, the radar cross sectional area when viewed from an object resident in a device axis direction at a small offset angle is reduced to a desired area in comparison with the case with a plane antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device mounted on an aircraft, for example.

[0002]

2. Description of the Related Art FIG. 11 (a) is a perspective view of an antenna of a conventional radar device, and FIG. 11 (b) is a radar device configuration diagram.
1 in FIG. 11 is a plane, the radar cross section reduction purposes constant angle theta [deg] offset by an array antenna with respect to the target direction, the 2 structural base, 3 ₁ to 3 _n
Is an n number of elements arranged along the structural substrate, 4 is a beam controller, 5 is an excitation receiver, and 6 is a signal processor.

Next, the operation will be described. Excitation receiver 5
The transmission signal generated in 1 is transmitted from the elements 3 _{1 to} 3 _n arranged along the structural substrate 2 of the array antenna 1, and the signal reflected by the target is directed by the beam controller 4 by the array antenna. The signal is received in the beam directivity, and the target signal and the like are output from the signal processor 6 through the excitation receiver 5.

In the phased array radar, since the antenna gain is lowered by beam scanning, the beam scanning range of the radar device is defined here as an angular range until the antenna gain becomes 1/2 of that in the front scanning.
Since the antenna gain is proportional to the projected area of the antenna array surface on the plane perpendicular to the beam scanning direction, the antenna gain is proportional to cosφ when the beam scanning angle is φ [degrees] in the planar array antenna, as shown in FIG. Thus, the beam scanning is possible up to ± 60 [degrees].

The relationship between the offset angle θ [degree] and the radar cross-sectional area σ [m ² ] of the rectangular planar antenna as shown in FIG.

[0006]

[Equation 1]

It is represented by FIG. 4 shows the antenna height a = 1.
[M], antenna width b = 1 [m], frequency 10 [GH
z] is a result of trial calculation. In this example, the offset angle θ of the flat array antenna is 10 as shown by the broken line.
It can be seen that if the angle is set to [degrees] or more, the radar cross-sectional area viewed from the partner radar device in the axial direction of the own device can be set to σ = 10 [m ² ] or less.

[0008]

In the conventional radar device, since the array antenna is constructed in a plane as described above, the antenna is used for wide-angle beam scanning of ± 60 [degrees] or more as shown by the broken line in FIG. The gain is significantly reduced, and the radar cross section can be reduced as the offset angle of the array antenna is increased as shown by the broken line in FIG. 4, but there is a problem that the antenna gain is reduced accordingly. It was

FIG. 5 is a conceptual diagram of generation of cross polarization by beam scanning of a curved array antenna. As shown in FIG. 5A, the hemispherical array antenna is moved in the front direction (φ =
Even if the polarization directions of the respective elements are aligned at 0 [degrees], the beam scanning is performed (φ = 45 [degrees], 90 [degrees]) as illustrated in FIG.
And a cross polarization component as shown in FIG. 5C is generated.
Generally, when the target is tracked by the monopulse angle measuring process, the cross polarization-to-main polarization ratio is required to be about −30 [dB] or less. There is a problem that the requirement cannot be satisfied due to the generation of the polarized component, and the monopulse angle measurement cannot be performed.

The present invention has been made in order to solve the above-mentioned problems. By making the array antenna into a curved surface shape, wide-angle beam scanning of ± 60 [degrees] or more is possible, and compared with a planar array antenna. It is an object of the present invention to provide a radar device capable of reducing the radar cross-sectional area without significantly reducing the antenna gain with a small offset angle.

Further, in the radar device provided with the curved array antenna, the array antenna front direction (φ
= 0 [degrees]), the cross polarization characteristics are prevented from deteriorating, which is a problem when beam scanning is performed.
An object of the present invention is to obtain a radar device having a low radar cross-sectional area that enables monopulse angle measurement at a desired beam scanning angle.

[0012]

A radar device according to the present invention is a radar device for offsetting an array antenna by a constant angle θ [degree] with respect to a target direction for the purpose of reducing a radar cross-sectional area. It is composed of.

Further, in the above radar apparatus, the array antenna is composed of a structural base formed of a cylindrical shape or a part of the cylindrical shape, and a plurality of elements arranged along the side surface thereof, and the polarization direction is cylindrical. It is aligned with the axial direction of.

Further, the array antenna of the above radar device is arranged along the spherical surface with a structural base formed by a spherical shape or a part of the spherical shape having an aperture length D [m] and a radius of curvature R [m]. And a radius of curvature of the array antenna is selected so that D / R ≦ 0.45.

[0015]

In the radar apparatus according to the present invention, the array antenna is formed into a curved shape, so that wide-angle beam scanning of ± 60 [degrees] or more becomes possible. Further, it is possible to reduce the radar cross-sectional area viewed from the target in the axial direction to a desired value with a smaller offset angle than that of the planar antenna.

Further, in the radar device according to the present invention, the polarization direction is aligned with the axial direction of the cylinder, so that the deterioration of the cross polarization characteristic at the time of beam scanning, which is a problem when the antenna is curved, can be prevented. .

Further, the radar device according to the present invention comprises:
When the array antenna has a spherical surface or a part of a spherical surface, the ratio of the antenna aperture diameter to the antenna curvature is D / R ≦ 0.
By selecting so as to be 45, even when φ = 60 [degree] beam scanning, the cross polarization-to-main polarization ratio, which is generally required to perform the monopulse angle measurement processing, is about −30 [dB] or less. Can be satisfied.

[0018]

【Example】

Example 1. A first embodiment of the present invention will be described below with reference to FIG. 1 (a) is a perspective view of an antenna for an aircraft-mounted radar, FIG. 1 (b) is a radar device configuration diagram, and 1 is an array antenna formed of a semi-cylindrical column, and has a low radar cross-sectional area as shown in FIG. For the purpose of optimization, it is offset by a constant angle θ [degree] with respect to the target direction. 2 is a structural substrate, 3
_{1 to} 3 _n are n elements arranged along the structural substrate, 4 is a beam controller, 5 is an excitation receiver, and 6 is a signal processor.

Next, the operation will be described. The transmitted signal is generated by the excitation receiver, and the structural substrate 2 of the array antenna 1
Are transmitted by the elements 3 _{1 to} 3 _n arranged along the line, are reflected by the target, are received by the array antenna in the beam directivity based on the phase information given by the beam controller 4, and the excitation receiver 5 Then, the target signal is output from the signal processor 6.

If the beam scanning range of the radar device is defined as an angular range until the antenna gain becomes 1/2 with respect to the front direction (φ = 0 [degree]) scanning, the antenna gain is a plane perpendicular to the beam scanning direction. Since it is proportional to the projected area of the antenna array surface onto, the beam scanning angle is φ [degrees] (1
+ Cos φ) / 2, as shown by the solid line in FIG.
It can be seen that the semi-cylindrical array antenna can perform beam scanning up to ± 90 [degrees].

The radar cross section σ with respect to the offset angle θ [degree] on the side surface of the cylindrical antenna as shown in FIG. 3B.
[M ² ] is

[0022]

[Equation 2]

It is represented by FIG. 4 shows the result of trial calculation in the case where the radius of the cylinder is 0.5 [m], the height of the cylinder is 1 [m], and the frequency is [10 GHz]. When the columnar array antenna is offset by θ = 10 [degrees] with respect to the target direction, the radar cross-sectional area is σ = 0.0 as shown by the solid line in FIG.
It becomes 1 m ² or less, and it is possible to significantly reduce the radar cross-sectional area as compared with the case of a planar array antenna having the same offset angle and the same projection area. Therefore, by configuring the array antenna in a curved shape, it is possible to obtain a radar device having a low radar cross-sectional area with little deterioration in antenna gain.

Although the above-mentioned embodiment uses the radar device mounted on the aircraft, the present invention is not limited to this.
It may be outside of structures such as missiles, land vehicles, satellites, ground radar sites, and other buildings, and the shape may be part of a spherical surface, a cone, etc., or a part of a curved surface that combines these. Alternatively, there may be multiple locations.

Example 2. FIG. 6 (a) shows an array antenna composed of a structural base formed by a cylindrical shape or a part of a cylindrical shape and a plurality of elements arranged along the side surface thereof, and the axial direction of the cylindrical shape in the front direction. 6B is a perspective view of the antenna of the second embodiment in which the polarization directions are aligned with each other. FIG. 6B is a radar device configuration diagram, and 1 is an array antenna formed by a cylindrical shape or a part of the cylindrical shape. As shown in (b),
A fixed angle θ with respect to the target direction for the purpose of reducing the radar cross section
Offset by [degree]. 2 is a structural substrate, 3 ₁
˜3 _n are n elements arranged along the structural substrate, 4 is a beam controller, 5 is an excitation receiver, and 6 is a signal processor.

Next, the operation will be described. The transmitted signal is generated by the excitation receiver, and the structural substrate 2 of the array antenna 1
Are transmitted by the elements 3 _{1 to} 3 _n arranged along the line, are reflected by the target, are received by the array antenna in the beam directivity based on the phase information given by the beam controller 4, and the excitation receiver 5 Then, the target signal is output from the signal processor 6.

FIG. 7 is a conceptual diagram of beam scanning when the polarization direction is not aligned with the axial direction of the cylinder in the cylindrical array antenna. As shown in FIG. 7A, φ = 0 [degree]
If the polarization is not aligned with the axial direction of the cylinder in the direction shown in Fig. 7 (b)
And, as shown in FIG. 7C, it can be seen that cross-polarization components appear by beam scanning. FIG. 8 is a conceptual diagram when polarized waves are aligned in the axial direction of the cylinder with φ = 0 (FIG. 8 (a)). As shown in FIGS. 8 (b) and 8 (c), in this case φ It can be seen that cross-polarization components due to beam scanning in the direction do not occur.

Although the above embodiment uses the spherical array antenna for mounting on an aircraft, the present invention is not limited to this, and it is not limited to this, and can be applied to ships, missiles, land vehicles, satellites, ground radar sites, and other buildings. It may be outside the structure.

Example 3. FIG. 9A shows an array antenna, which is a structural base formed by a spherical shape or a part of the spherical shape having an aperture length D [m] and a radius of curvature R [m], and a plurality of array bases arranged along the side surface thereof. 9 is a perspective view of the antenna of the third embodiment in which the curvature of the array surface is D / R ≦ 0.45, and FIG. An array antenna having a curved surface shape such that the curvature of the array surface is D / R ≦ 0.45,
As shown in FIG. 9B, the angle is offset by a constant angle θ [degree] with respect to the target direction for the purpose of reducing the radar cross-sectional area. Reference numeral 2 is a structural substrate, 3 _{1 to} 3 _n are n elements arranged along the structural substrate, 4 is a beam controller, 5 is an excitation receiver, and 6 is a signal processor.

Next, the operation will be described. The transmitted signal is generated by the excitation receiver, and the structural substrate 2 of the array antenna 1
Are transmitted by the elements 3 _{1 to} 3 _n arranged along the line, are reflected by the target, are received by the array antenna in the beam directivity based on the phase information given by the beam controller 4, and the excitation receiver 5 Then, the target signal is output from the signal processor 6.

FIG. 10 shows a trial calculation of the relationship between the antenna aperture diameter-antenna curvature ratio D / R and the peak value of the cross polarization component. As can be seen from FIG. 10, the beam scanning range is ± 6
The peak value of the cross polarization component is −30 when 0 degree is set.
The antenna diameter-to-antenna curvature ratio required to be [dB] or less is D / R ≦ 0.45. However,
As the D / R becomes smaller, the beam shape becomes closer to the planar shape and the beam scanning range becomes narrower. Therefore, in order to perform the monopulse angle measurement in the wide beam scanning of ± 60 [degrees] or more, D / R = 0.45.
Is desirable.

Although the above-described embodiment uses the spherical array antenna for mounting on an aircraft, the present invention is not limited to this. For example, ships, missiles, land vehicles, satellites, ground radar sites, other buildings, etc. It may be outside the structure.

[0033]

As described above, according to the present invention, when the array antenna is offset by a constant angle θ [degree] with respect to the target direction for the purpose of reducing the radar cross-sectional area, the array surface is curved. As a result, it is possible to obtain a radar apparatus having a low radar cross-sectional area which can be reduced to a desired radar cross-sectional area with a smaller offset angle than a rear array antenna and which can scan a wide-angle beam of ± 60 [degrees] or more. It is possible.

Further, it is possible to prevent the deterioration of the cross polarization characteristic, which is a problem when the array antenna is formed into a curved surface in the above radar apparatus, and to obtain a radar apparatus having a low radar cross-sectional area capable of a monopulse side angle. is there.

[Brief description of drawings]

FIG. 1 is an antenna perspective view and a radar device configuration diagram of a radar device according to a first embodiment of the present invention.

FIG. 2 is a comparison diagram of beam scanning ranges of a flat plate antenna and a semi-cylindrical antenna.

FIG. 3 is an external view of a flat plate antenna and a cylindrical antenna.

FIG. 4 is a comparison diagram of radar cross-sectional area σ calculation values of a flat plate antenna and a cylindrical antenna.

FIG. 5 is a conceptual diagram of cross polarization generation when the array surface is curved.

FIG. 6 is an antenna perspective view of a radar device and a configuration diagram of the radar device according to a second embodiment of the present invention.

FIG. 7 is a conceptual diagram of cross polarization generation when the polarization is not aligned in the axial direction of the cylinder in the cylinder array antenna.

FIG. 8 is a conceptual diagram when the polarized waves are aligned in the axial direction of the cylinder in the cylindrical array antenna.

FIG. 9 is a perspective view of an antenna of a radar device and a configuration diagram of the radar device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between a ratio (D / R) of an antenna aperture diameter to a radius of curvature and a peak value of a cross polarization component.

FIG. 11 is a perspective view of an antenna of a conventional radar device and a configuration diagram of the radar device.

[Explanation of symbols]

1 Array Antenna 2 Structural Substrate 3 _{1 to} 3 _n Element 4 Beam Controller 5 Excitation Receiver 6 Signal Processor

Claims (3)

[Claims] 1. A plurality of elements are arranged on a structural substrate,
An array antenna that is offset by a certain angle with respect to the target direction for the purpose of reducing the radar cross-sectional area and a transmission signal are generated.
The array is composed of an excitation receiver that processes a received signal, a signal processor that detects a target signal from the received signal, and a beam controller that gives phase information to each element so that the array antenna has a desired directivity. A radar device having a curved surface. 2. The radar device according to claim 1, wherein the array surface is formed into a cylindrical shape or a part of a cylindrical shape for the purpose of reducing the radar cross-sectional area, and the polarization direction is aligned with the axial direction of the cylinder. 3. The array surface is formed by a spherical shape or a part of a spherical shape having an antenna aperture length D [m] and a curvature radius R [m] of the array surface for the purpose of reducing the radar cross-sectional area. 2. The radar device according to claim 1, wherein the ratio of the radius of curvature of the surface is selected to be D / R ≦ 0.45.