JPH10170575A - Boresight alignment plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a boresight alignment plate that can obtain a high alignment accuracy with a small size with reference to a waveform, by arranging two flat plates, which comprises a step at a 1/4 wavelength and whose area and shape are mutually identical, side by side. SOLUTION: Electromagnetic waves, which are radiated to a space from a transmitter are reflected by a boresight alignment plate 9 on a rotating base, and they are received by a receiver via a receiving antenna. At this time, the synthetic radar reflection cross-section(RCS) characteristic of flat plates 9a, 9b, of the same area and the same shape, at the boresight alignment plate 9 becomes array synthetic patterns having an interval (a), and an optical path length becomes twice that of an ordinary array antenna. At this time, when a step (d) is set at a 1/4 wavelength, two RCS patterns are synthesized at an opposite phase. As the characteristic of the synthesized RCS pattern, an amplitude becomes minimum when the electromagnetic waves are incident perpendicularly to the boresight alignment plate 9. In addition, its level with reference to an angle is very steep and very highly sensitive near a perpendicular incident direction. Consequently, it is possible to obtain the boresight alignment plate, whose size is small and whose alignment accuracy is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boresight alignment plate used for boresight alignment when measuring an antenna.

[0002]

2. Description of the Related Art When a flat plate is irradiated with a radio wave, an RCS characteristic (RCS: Radar) indicating a reflection characteristic in a radio wave irradiation direction.
A method for performing boresight alignment at the time of antenna measurement using Cross Section (radar cross section of radar) is described in the following document.

[0003] Mammer J. et al. A, "Calibra
Tion Techniques For Compac
t Antenna Test Ranges ", Pr
receiveds of AMTA, Oct. 199
0, pp13-3 to13-5

Hereinafter, this method will be described. FIG.
Is a diagram showing a state of boresight alignment implementation, 1 is a conventional boresight alignment plate, 2 is a turntable, 3 is an angle detector, 4 is a transmitting antenna, 5 is a transmitter,
6 is a receiving antenna, 7 is a receiver.

Next, the operation will be described. Electromagnetic waves radiated from the transmitter 5 to the space via the transmission antenna 4 are reflected by the boresight alignment plate 1 placed on the turntable 2. This reflected wave is received by the receiver 7 via the receiving antenna 6. The degree of reflection at this time is generally determined by RC
Called S.

FIG. 14 is a view showing the boresight alignment plate 1. In the figure, reference numeral 8 denotes a line indicating the RCS observation direction. The angle characteristic σ (θ) of the RCS of such a flat plate is “
Where a and b are the dimensions of a flat plate,
θ represents the observation direction, λ represents the wavelength, and k represents the wave number.

[0007]

(Equation 1)

The characteristic represented by "Equation 1" becomes a pattern which becomes maximum when the light is perpendicularly incident on the flat plate (when θ is 0). Therefore, boresight alignment is performed by specifying the direction of the peak.

As a means for specifying the maximum direction,
Since the change in the pattern near the maximum value is small and the sensitivity to the angle change is reduced, the angle at two points that are several dB down from right to left or up and down from the maximum value is determined, and the average value is used as the maximum value. Is taken.

Since the alignment accuracy obtained in this case is determined by the sharpness of the beam, a method of increasing the size of the boresight alignment plate 1 with respect to the wavelength is used to obtain high alignment accuracy.

FIG. 15 shows that a = 400 mm and b = 200 m.
9 shows an RCS pattern when m and λ = 54.51 mm.

[0012]

In the conventional boresight alignment plate, it is necessary to increase the dimension with respect to the wavelength in order to achieve the required alignment accuracy.
When it is necessary to obtain very high precision, such as 0.005 degrees or less, there is a problem that a flat plate of several meters is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to obtain a boresight alignment plate that can obtain high alignment accuracy with a small size relative to a wavelength.

[0014]

According to a first aspect of the present invention, there is provided a boresight alignment plate in which two flat plates having a step of a quarter wavelength and having the same area and shape are arranged side by side.

Further, the boresight alignment plate according to the second invention is provided with a rotation mechanism that rotates about a direction perpendicular to the boresight alignment plate of the first invention as an axis.

Further, in the boresight alignment plate according to the third invention, flat plates having the same area and shape are arranged in a cross shape, and two diagonal flat plates are formed with a step of a quarter wavelength. It is made to have.

Further, the boresight alignment plate according to the fourth invention has one flat plate and one-fourth of the flat plate.
A flat plate having a half area having a wavelength step is arranged at the center of the plate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a configuration diagram of a boresight alignment plate according to Embodiment 1 of the present invention, and FIG. 2 is a diagram illustrating a state of performing boresight alignment using the same.

In FIG. 1, reference numeral 8 is the same as in FIG. 14, 9a is a first flat plate, and 9b is a second flat plate. d is a step between the first flat plate 9a and the second flat plate. 2, 2, 3, 4, 5, 6, and 7 are the same as those in FIG. 13, and 9 is a boresight alignment plate according to the first embodiment of the present invention.

Next, the operation will be described. In FIG. 2, an electromagnetic wave radiated from the transmitter 5 to the space via the transmitting antenna 4 is reflected by a boresight alignment plate 9 placed on the turntable 2, and the reflected wave is received via the receiving antenna 6. The data received by the device 7 is the same as in the conventional example.

Next, the RCS of the boresight alignment plate 9
The angle characteristics will be described. The RCS angle characteristic of each of the first flat plate 9a and the second flat plate 9b is expressed by the above-mentioned "Equation 1". Also, the combined R of the first and second plates is
The CS characteristic is considered to be an array composite pattern having an interval a. In this case, unlike an ordinary array antenna, the optical path length is doubled in the RCS. Where the step d
Is set to １ wavelength, two RCS patterns are synthesized in opposite phases. Therefore, the combined RCS pattern obtained based on this is represented by "Equation 2".

[0022]

(Equation 2)

This characteristic shows that the amplitude becomes minimum when the electromagnetic wave is perpendicularly incident on the boresight alignment plate 9,
The same characteristics as the monopulse difference pattern in the monopulse antenna can be obtained. In the vicinity of the normal incidence direction, the level change with respect to the angle becomes very steep, so that the sensitivity is higher than that of the conventional boresight alignment plate 1 using a flat plate. Therefore, the same alignment accuracy can be obtained with a smaller size than the conventional boresight alignment plate 1.

FIG. 3 shows that a = 200 mm, b = 200 mm,
9 shows an RCS pattern when λ = 54.51 mm. In the figure, the dotted line shows the RCS pattern of the boresight alignment plate 9 according to the first embodiment of the present invention, and the solid line shows the RCS pattern of the conventional boresight alignment plate 1 having the same area. It can be seen from the figure that the change in amplitude is sharp near the vertical incidence direction.

FIG. 4 shows an RCS three-dimensional pattern under the same conditions as in FIG. From the figure, it can be seen that the direction in which the amplitude is minimum is constituted by a line.

Embodiment 2 FIG. FIG. 5 shows a second embodiment of the present invention. In the figure, 9 is the same as that of FIG. 1, and 10 is a mechanism for rotating the boresight alignment plate 9 around an axis perpendicular to the plate.

FIG. 6 is a view showing how alignment is performed using the boresight alignment plate 9 of FIG. In the figure, reference numeral 2b denotes a two-axis turntable.

The boresight alignment plate 9 realizes biaxial boresight alignment. The boresight alignment plate 9 is brought into the state shown in FIG. Is carried out.

Next, the rotation mechanism 10 rotates the boresight alignment plate 9 by 90 degrees. Thereby, NULL is formed in the elevation direction. Therefore, boresight alignment in the elevation direction is performed by driving the turntable in the elevation direction. Thereby, biaxial boresight alignment can be performed.

Embodiment 3 FIG. 7 shows a boresight alignment plate 11 according to a third embodiment of the present invention. In the drawing, reference numerals 9a and 9b are the same as those in FIG. 1, and a flat plate 9b having a step of a quarter wavelength is arranged at a diagonal position.

FIG. 8 is a diagram showing how alignment is performed using the boresight alignment plate 11 of FIG.

Since the RCS pattern of the boresight alignment plate 11 has the same structure as the boresight alignment plate 8 of the first embodiment of the present invention in both the turning direction and the elevation direction, the RCS pattern is on both the rotation and the elevation axes. NU
This becomes a pattern in which LL is formed.

FIG. 9 shows the R of the boresight alignment plate 11.
3 shows a CS three-dimensional pattern. From the figure, it can be seen that NULL is formed in a cross shape.

Therefore, this boresight alignment plate 1
When performing two-axis alignment using 1, the turning angle is driven with the elevation angle slightly changed to perform the alignment in the turning direction, and then the elevation angle is driven with the turning direction slightly changed. Perform alignment in the elevation direction. Thus, two-axis alignment can be performed.

Embodiment 4 FIG. FIG. 10 shows a boresight alignment plate 12 according to a fourth embodiment of the present invention. In the drawing, 12a is a central flat plate having a quarter wavelength step, 12b is an outer peripheral flat plate, and 12a and 12b have the same area.

FIG. 11 is a diagram showing how alignment is performed using the boresight alignment plate 12 of FIG.

The RCS pattern of the boresight alignment plate 12 is a pattern in which a point having a minimum amplitude is formed only in a direction perpendicular to the plate.

FIG. 12 shows a three-dimensional RCS pattern of the boresight alignment plate 12. From the figure, it can be seen that NULL is formed as a point.

Therefore, this boresight alignment plate 1
When two-axis alignment is performed by using 2, the two-axis alignment can be performed by driving the turning angle and the elevation angle to drive in the direction of the smallest amplitude.

[0040]

According to the first aspect of the present invention, the flat plates having a quarter-wave step are arranged side by side.
Since the S pattern shows a steep change in the vicinity of the vertical incidence direction, there is an effect that a boresight alignment plate that can realize high alignment accuracy even with a small size can be obtained.

According to the second aspect, the mechanism for rotating the boresight alignment plate according to the first aspect around an axis perpendicular to the plate is provided, so that high alignment accuracy is achieved in the two axes of the turning direction and the elevation direction. There is an effect that a boresight alignment plate that can be obtained is obtained.

According to the third aspect of the present invention, since the flat plate having a quarter-wave step is arranged diagonally, a pattern in which the amplitude is minimized in a cross shape in the turning and elevating directions is formed. Thus, the same effect as that of the second invention can be easily obtained.

According to the fourth aspect, since the flat plate having a quarter-wave step is arranged at the center of the plate, a point where the amplitude becomes minimum only in the direction perpendicular to the plate is formed. The same effect as that of the third invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of a boresight alignment plate according to the present invention.

FIG. 2 is a diagram showing a state of boresight alignment using the boresight alignment plate according to the first embodiment of the present invention;

FIG. 3 is a diagram showing an RCS pattern of the boresight alignment plate according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a three-dimensional RCS pattern of the boresight alignment plate according to the first embodiment of the present invention.

FIG. 5 is a diagram showing Embodiment 2 of a boresight alignment plate according to the present invention.

FIG. 6 is a diagram showing a state of boresight alignment using a boresight alignment plate according to a second embodiment of the present invention.

FIG. 7 is a diagram showing Embodiment 3 of a boresight alignment plate according to the present invention.

FIG. 8 is a diagram showing a state of boresight alignment using a boresight alignment plate according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a three-dimensional RCS pattern of a boresight alignment plate according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a boresight alignment plate according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a state of boresight alignment using a boresight alignment plate according to a fourth embodiment of the present invention.

FIG. 12 is a diagram showing a three-dimensional RCS pattern of a boresight alignment plate according to a third embodiment of the present invention.

FIG. 13 is a view showing a state of boresight alignment using a conventional boresight alignment plate.

FIG. 14 is a view showing a conventional boresight alignment plate.

FIG. 15 RCS of conventional boresight alignment plate
It is a figure showing a pattern.

[Explanation of symbols]

1 boresight alignment plate, 2 turntable, 3 angle detector, 4 transmitting antenna, 5 transmitter, 6 receiving antenna, 7 receiver, 8 line indicating RCS observation direction, 9
Boresight alignment plate, 10 rotation mechanism, 11
Boresight alignment plate, 12 Boresight alignment plate.

Claims (4)

[Claims] 1. A first flat plate, which is the same as the first flat plate disposed at the right or left of the first flat plate with a step of a quarter wavelength in the thickness direction in parallel with the first flat plate. A boresight alignment plate comprising a second flat plate having an area and a shape. 2. The boresight alignment plate according to claim 1, further comprising a function of rotating the first and second flat plates around an arrival direction of the electromagnetic wave. 3. A first flat plate, and a second flat plate having the same area and shape as the first flat plate arranged in parallel with the first flat plate and having a step of a quarter wavelength in the thickness direction. And a third flat plate having the same area and shape as the first flat plate, which is arranged in parallel with the upper or lower portion of the first flat plate with a step of a quarter wavelength in the thickness direction, A boresight alignment plate comprising a fourth flat plate having the same area and shape as the first flat plate, which is disposed in parallel with the upper or lower portion of the flat plate and has a step of a quarter wavelength in the thickness direction. 4. A first flat plate and a half of a first flat plate which is parallel to the first flat plate and has a step of a quarter wavelength in the thickness direction and is disposed at the center of the first flat plate. A boresight alignment plate comprising a second flat plate having an area of 1.