JP2013160705A - Radar cross-sectional area measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radar cross-sectional area measurement system for suppressing multiple reflection between an object to be measured and the ground without using a wave absorber.SOLUTION: A radar cross-sectional area measurement system includes: an object 4 to be measured, which is arranged on the ground; a measurement antenna device 2 which transmits test radio waves 5a toward the object 4 to be measured, and receives reflected waves 5b from the object 4 to be measured to measure radar cross-sectional area of the object 4 to be measured; and a support rotation mechanism 3 for supporting the object 4 to be measured at an upper part of the ground 10 and rotating it. A normal direction of the ground 10 in a peripheral area where the object 4 to be measured is arranged is set so as to be different from a projection direction from the object 4 to be measured to the ground of the peripheral area.

Description

  The present invention relates to a radar cross section measurement system that measures a radar cross section (RCS) by transmitting a test radio wave to a measurement object placed outdoors and receiving a reflected wave.

2. Description of the Related Art Conventionally, a radar cross-sectional area measurement system using a measurement antenna device that transmits a test radio wave to a measurement object placed outdoors and receives a reflected wave is well known.
FIG. 8 is a side sectional view schematically showing a general radar sectional area measurement system for measuring a radar sectional area (RCS) outdoors. In FIG. The support rotation mechanism 3 is disposed, and the object to be measured 4 is attached on the support rotation mechanism 3.

The support rotation mechanism 3 supports the device under test 4 and rotates the device under test 4 in a desired direction.
The measurement antenna device 2 transmits the test radio wave 5a (see the solid line arrow) to the device under test 4 after the device under test 4 is rotationally positioned in the desired direction by the support rotation mechanism 3, and the device under test 4 The reflected wave 5b from (see the one-dot chain line arrow) is received.

  The antenna apparatus for measurement 2 separately measures in advance a calibrator with a known RCS (for example, a conductor sphere) in the same manner, and installs the received power when the device under test 4 is installed and the calibrator. The RCS of the device under test 4 is measured by comparing the received power at that time.

When measuring the RCS of the device under test 4, it is naturally necessary to receive only the reflected wave 5 b from the device under test 4.
The propagation path 5 of the test radio wave 5a and the reflected wave 5b is as shown by a solid line arrow and a one-dot chain line arrow in FIG. Hereinafter, the reflected wave 5b that is received when the test radio wave 5a is directly reflected by the DUT 4 is referred to as a direct wave component.

  However, in actuality, the signal received by the measurement antenna device 2 includes not only the reflected wave 5b (direct wave component) but also the propagation path 6 between the DUT 4 and the ground 10 in the surrounding area. Multiple reflected waves 6c (see broken line arrows) resulting from the multiple reflected waves 6a and 6b (multiple reflected wave components) are included.

In addition, although the multiple reflected wave 6a is actually a single reflected wave, it is a component different from the measurement target. Therefore, in order to distinguish it from the measurement target reflected wave 5b, the multiple reflected wave 6a is hereinafter collectively referred to as a multiple reflected wave. .
The multiple reflected wave 6c is received by propagating through a path of the measurement antenna device 2 → the device under test 4 → the ground 10 in the peripheral area of the device under test 4 → the device under test 4 → the antenna device for measurement 2.

  At this time, if the distance between the DUT 4 and the ground 10 is sufficiently larger than the DUT 4, the reflected wave 5b (direct wave component) and the multiple reflected waves to the measurement antenna device 2 are used. The arrival time difference from 6c (multiple reflected wave component) increases, and both are clearly separated on the time axis.

If the above property is used, it is possible to extract only the reflected wave 5b (direct wave component) by removing or suppressing the multiple reflected wave 6c (multiple reflected wave component).
However, when the distance between the DUT 4 and the ground 10 is smaller than the DUT 4, it is difficult to extract only the direct wave component using the above method. Means must be used to remove or suppress multiple reflected wave components.

Therefore, conventionally, a technique for suppressing multiple reflected wave components using a radio wave absorber has been proposed (see, for example, Non-Patent Document 1).
FIG. 9 is a side cross-sectional view schematically showing a conventional radar cross-sectional area measurement system capable of suppressing multiple reflected wave components, and shows the technique described in Non-Patent Document 1.

In FIG. 9, the radio wave absorber 7 is disposed on the surface of the ground 10 in the peripheral area of the device under test 4 and the support rotation mechanism 3 so as to include the projection area of the device under test 4 onto the ground 10.
As shown in FIG. 9, by arranging the radio wave absorber 7, most of the multiple reflected waves 6 a that are reflected by the DUT 4 and incident on the ground 10 are dissipated as heat loss by the radio wave absorber 7. Therefore, it is possible to significantly suppress the multiple reflected wave 6b (see the dotted arrow).

N. C. Currie ed. , Techniques of Radar Reflexibility Measurement, Arthouse House, Inc. , MA, 1984.

In the conventional radar cross-sectional area measurement system, as in the technique described in Non-Patent Document 1 (FIG. 9), the radio wave absorber 7 is placed on the ground 10 in the peripheral area of the object 4 to be measured in order to suppress the multiple reflected wave 6b. Therefore, when the object to be measured 4 is large and the projection area onto the ground 10 becomes very wide, a very large number of radio wave absorbers 7 are required, resulting in an increase in cost. It was.
In particular, when the radio wave absorber 7 is always arranged outdoors, a very high weather resistance is required, so that there is a problem that the price of the radio wave absorber 7 becomes very expensive and further increases the cost. .

  In addition, a method of arranging the radio wave absorber 7 on the ground 10 only at the time of good weather measurement using a low price and general indoor radio wave absorber 7 (low weather resistance) can be considered. Each time, a great amount of labor is required to carry out, arrange and store the radio wave absorber 7, and it is also necessary to construct a facility for storing a huge amount of the radio wave absorber 7, resulting in an increase in cost. There was a problem that it could not be avoided.

  The present invention has been made to solve the above-described problems, and is a radar cross-sectional area measurement system capable of suppressing multiple reflections between an object to be measured and the ground without using a radio wave absorber. The purpose is to obtain.

  A radar cross-sectional area measurement system according to the present invention transmits a test wave to a device to be measured placed on the ground and the device to be measured, and receives a reflected wave from the device to be measured to detect the radar of the device to be measured. A radar cross-sectional area measurement system including a measurement antenna device for measuring a cross-sectional area and a support rotation mechanism for supporting and rotating the object to be measured above the ground. The normal direction of the ground of the area is set to be different from the projection direction from the object to be measured to the ground of the peripheral area.

  According to the present invention, it is possible to suppress multiple reflections between the object to be measured and the ground by using a simple and inexpensive configuration in which the shape of the ground in the peripheral area of the object to be measured and the support rotation mechanism is simply changed. it can.

It is the xz plane sectional view and the top view showing the radar sectional area measuring system concerning Embodiment 1 of this invention. It is explanatory drawing which shows the simulation analysis structure of Embodiment 1 of this invention. It is explanatory drawing which shows the effect of Embodiment 1 of this invention with the analysis result of FIG. It is yz surface sectional drawing which shows the other structural example of the radar cross-sectional area measurement system which concerns on Embodiment 1 of this invention. It is a xz plane sectional view and a top view showing a radar sectional area measurement system according to Embodiment 2 of the present invention. It is a xz plane sectional view and a top view showing a radar sectional area measurement system according to Embodiment 3 of the present invention. It is xz surface sectional drawing and the top view which show the other structural example of the radar cross section measuring system which concerns on Embodiment 3 of this invention. It is xz surface sectional drawing which shows the conventional radar cross-sectional area measurement system. It is xz plane sectional drawing which shows the other structural example of the conventional radar cross-section measuring system.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings.
1A and 1B are an xz plane sectional view and a top view showing Embodiment 1 of the present invention, an upper side is an xz plane sectional view, and a lower side is a top view as viewed from the z direction.

  In FIG. 1, a radar cross-sectional area measurement system according to Embodiment 1 of the present invention includes a measurement antenna device 2 disposed on the ground 1, a support rotation mechanism 3 disposed on the ground 10 in the peripheral area, and an object to be measured. A measurement object 4 and a spacer 8 for installing the support rotation mechanism 3 horizontally are provided.

In FIG. 1, the horizontal direction with respect to the measuring antenna device 2 is defined as the x axis, the normal direction with respect to the surface of the ground 1 is defined as the z axis, and the vertical direction with respect to the zx plane is defined as the y axis with respect to the center of the device under test 4 To do.
The measurement antenna device 2 transmits the test radio wave 5a in the −x direction and receives the reflected wave 5b of the test radio wave 5a in order to measure the RCS of the DUT 4.
The support rotation mechanism 3 supports the object to be measured 4 and positions the object to be measured 4 by rotating it around the z axis.

The ground 10 in the peripheral area of the DUT 4 and the support rotation mechanism 3 has a flat surface shape, but has a uniform shape in the y direction and is inclined with respect to the -x direction.
That is, the normal direction of the ground 10 in the peripheral area of the device under test 4 is set to be different from the projection direction from the device under test 4 to the ground 10 of the peripheral area.

In particular, in FIG. 1, the normal direction of the ground 10 in the peripheral area is different from the normal direction of the ground 1 other than the peripheral area (the ground 1 between the measurement antenna device 2).
Specifically, the ground 10 in the peripheral area of the DUT 4 and the support rotation mechanism 3 is inclined downward in the −x direction with respect to the region (ground 1) other than the peripheral area of the support rotation mechanism 3.
It is desirable that the range of the ground 10 to be inclined is set to be equal to or wider than the range including the projection area of the DUT 4 rotated at various angles onto the ground 10.

  With the above configuration, among the test radio waves 5a (solid arrows) transmitted from the measurement antenna device 2, the multiple reflected waves 6a (broken arrows) reflected downward by the device under test 4 and incident on the ground 10 are inclined. It is reflected by the ground 10 obliquely upward and to the left in the figure according to Snell's law, and becomes a multiple reflected wave 6b (broken arrows) that does not enter the object 4 to be measured.

  As a result, the multiple reflected waves 6a and 6b generated between the DUT 4 and the ground 10 are obtained when the ground 10 in the peripheral area is located on the same plane as the other ground 1 as in the conventional system (or other Compared to the case of being parallel to the ground 1), the RCS measurement error due to the multiple reflected wave components can be greatly suppressed.

Hereinafter, an electromagnetic field simulation result for confirming the effect of the first embodiment of the present invention will be described with reference to FIGS. 2 and 3.
FIG. 2 is an explanatory diagram showing a simulation analysis configuration according to the first embodiment of the present invention. The reflected wave 5b (direct wave component) to be measured and the multiple reflected wave 6c (multiple reflected wave component) corresponding to noise are shown. An analysis model that simplifies the problem is shown.

In FIG. 2, the measurement antenna device 2 is arranged at a position far away from the object to be measured 4, and the ground area 10 inclined in a planar shape similar to FIG. Is arranged.
In this case, the DUT 4 is a conductor having a shape like an airplane.

  The propagation path of the reflected wave 5b (one-time reflection component) that is the direct wave component of the test radio wave 5a is the measurement antenna device 2 → the object to be measured 4 → the measurement antenna device 2, and the multiple reflected wave 6c (three-time reflection). The propagation path of the component is as follows: measurement antenna device 2 → measurement object 4 → ground 10 → measurement object 4 → measurement antenna device 2.

  FIG. 3 is an explanatory diagram showing an RCS analysis result (effect of the first embodiment of the present invention) using the analysis model of FIG. 2, and the horizontal axis indicates the measurement angle of the measurement antenna device 2 as viewed from the device under test 4. (Rotation angle (0 ° to 360 °) of the DUT 4 and the vertical axis represents the RCS value (corresponding to the reception level).

In FIG. 3, the single reflection component (reflected wave) to be measured when θ = 0 °, θ = 10 °, and θ = 20 ° are set with the inclination angle θ of the ground 10 in the surrounding area as a parameter. 5b) shows an RCS (broken line) and an RCS (solid line) of a three-time reflected component (multiple reflected wave 6c) that becomes noise.
That is, the one-time reflected component (reflected wave 5 b) is the true value of RCS, and the three-time reflected component (multiple reflected wave 6 c) is an error due to multiple reflection between the DUT 4 and the ground 10.

As is apparent from the analysis result of FIG. 3, the inclination angle θ is set larger (θ = 10 °, θ = 20 °) than the conventional system in which the ground 10 is horizontal (inclination angle θ = 0 °). Thereby, the tendency for the RCS value of the three-time reflection component (multiple reflected wave 6c) to decrease can be confirmed.
The reason for this is that as the inclination angle θ increases, the ratio of the amount of the multiple reflected waves 6b on the ground 10 in the surrounding area again incident on the DUT 4 decreases.

As apparent from FIG. 3, in the case of the analysis model of FIG. 2, the RCS values of the three-time reflection component when the inclination angle θ of the ground 10 is set to about 20 ° are almost all measurement angles. It can be confirmed that the value is lower than the RCS value of the three-time reflection component at the inclination angle θ = 0 °.
As a result, it can be seen that the RCS measurement error caused by the multiple reflection between the DUT 4 and the ground 10 can be reduced by appropriately selecting the inclination angle θ of the ground 10 (about 20 °).

  From the above examination results, the ground 10 in the peripheral area of the DUT 4 is not limited to the configuration shown in FIG. 1 (inclined in the −x direction), and in view of obtaining the suppression effect of the multiple reflected waves 6c, It can be seen that it may tilt in the direction.

  However, when the descending inclination direction of the ground 10 in the peripheral area is set to approximately the + x direction (the direction of the measurement antenna device 2), the reflected wave from the ground 10 itself, not the DUT 4, depending on the inclination angle θ. Note that there is a possibility that the signal will be received by the measurement antenna device 2.

For example, as shown in FIG. 4, the ground 10 in the peripheral area of the DUT 4 may be inclined in the −y direction (a direction orthogonal to the straight x-axis connecting the measurement antenna device 2 and the DUT). .
4 is a yz-plane cross-sectional view showing another configuration example of the radar cross-sectional area measurement system according to Embodiment 1 of the present invention. The same reference numerals as those described above are given to the same components as those described above (see FIG. 1). ing.
In the configuration of FIG. 4 as well, the multiple reflected wave 6b is reflected in the −y direction (upwardly diagonally to the left in the figure), so that the effect of suppressing the multiple reflected wave 6c can be achieved as described above.

  As described above, the radar cross-sectional area measurement system according to the first embodiment (FIGS. 1 to 4) of the present invention includes the measurement object 4 disposed on the ground (on the ground 10) and the measurement object 4. The measurement antenna device 2 that transmits the test radio wave 5a toward the target and receives the reflected wave 5b from the DUT 4 and measures the RCS (radar cross section) of the DUT 4, and the DUT 4 on the ground 10 is provided with a support rotation mechanism 3 for supporting and rotating above 10.

The normal direction of the ground 10 in the peripheral area where the DUT 4 is arranged is set to be different from the projection direction from the DUT 4 to the ground 10 in the peripheral area. In this case, the shape of the ground 10 in the peripheral area is an inclined plane.
Furthermore, in the ground 10 in the peripheral area, the range in which the normal direction is different from the normal direction of the other ground 1 includes a projection area from the measurement object 4 when the measurement object 4 rotates.

  In this way, by using a simple and inexpensive configuration in which the shape of the ground 10 in the peripheral area of the object to be measured 4 and the support rotation mechanism 3 is different, the object to be measured 4 and the ground can be used without using a radio wave absorber. Multiple reflections between 10 and 10 can be suppressed.

Embodiment 2. FIG.
In the first embodiment (FIGS. 1 to 4), the ground 10 in the peripheral area of the DUT 4 is set to an inclined plane. However, the shape of the ground 10 is not limited to a plane. As shown in FIG.

  FIG. 5 is an xz plane sectional view and a top view showing a radar sectional area measuring system according to Embodiment 2 of the present invention. Components similar to those described above (see FIG. 1) are denoted by the same reference numerals. Detailed description is omitted.

In FIG. 5, the shape of the ground 10 in the peripheral area of the DUT 4 is a curved surface (for example, a parabolic surface).
In other words, the shape of the ground surface 10 is a shape corresponding to a parabolic surface having a focal point (or focal line) F in the vicinity of the upper left corner of the drawing deviating from the position of the DUT 4.

When the parabolic surface of the ground 10 has the focal point F, the shape of the ground 10 is a three-dimensional paraboloid that is not uniform in both the xz plane and the yz plane.
On the other hand, when the parabolic surface of the ground 10 has a focal line F, the shape of the ground 10 is a cylindrical parabolic surface that is uniform in the y direction.

As described above, in the radar cross-sectional area measurement system according to Embodiment 2 (FIG. 5) of the present invention, the shape of the ground 10 in the peripheral area is a curved surface, specifically, a parabolic surface. It consists of a part or part of a columnar paraboloid.
As a result, as compared with the case where the ground 10 is an inclined plane as described above (FIGS. 1 to 4), the propagation path of the multiple reflected wave 6 b can be reliably deviated from the DUT 4.
Therefore, it is possible to further reliably reduce the amount of the multiple reflected waves 6b between the DUT 4 and the ground 10 that are incident on the DUT 4 again.

Embodiment 3 FIG.
In the first and second embodiments (FIGS. 1 to 5), the ground 10 made of an inclined plane or curved surface in the peripheral area of the DUT 4 is formed below the vertical position of the other ground 1. However, the present invention is not limited to these configurations. For example, as shown in FIGS. 6 and 7, the ground 10 in the peripheral area may be formed above the vertical position of the other ground 1.

  FIG. 6 is an xz plane sectional view and a top view showing a radar sectional area measuring system according to Embodiment 3 of the present invention, and FIG. 7 is another configuration of the radar sectional area measuring system according to Embodiment 3 of the present invention. It is xz surface sectional drawing and a top view which show an example.

6 and 7, the ground 10 in the peripheral area of the DUT 4 and the support rotation mechanism 3 has a conical side shape that is rotationally symmetric with respect to the z axis, and is above the vertical position of the ground 1 in other regions. Is formed.
In FIG. 7, the DUT 4 and the support rotation mechanism 3 are housed in a recess 10a formed at the center of the ground 10 in the peripheral area.

Even when the ground 10 in the peripheral area is formed as shown in FIGS. 6 and 7, the effect of suppressing multiple reflections between the DUT 4 and the ground 10 can be obtained as described above.
In addition, since the substantial amount of configuration of the ground 10 in the peripheral area is reduced as compared with the first and second embodiments, the ground 10 can be formed at a low cost.

6 and 7, the shape of the ground 10 is a conical side surface shape that is rotationally symmetric with respect to the z axis. .
In the first to third embodiments (FIGS. 1 to 7), the measurement antenna device 2 may have a total of two antenna configurations (quasi-monostatic), one for transmission and one for reception. A single antenna configuration (completely monostatic) may be used for both transmission and reception.

  For example, even when a quasi-monostatic consisting of two antenna configurations is applied as the measurement antenna device 2, if the separation angle between the transmission antenna and the reception antenna as viewed from the device under test 4 is small, it is completely monostatic. Nearly identical measurement results can be obtained.

  Furthermore, in the first to third embodiments, the case where the support rotation mechanism 3 is directly installed on the ground 10 has been described as an example. However, only the surface shape (normal direction) of the ground 10 in the peripheral area of the DUT 4 is described. As long as is different from other surfaces, some structure may be interposed.

  DESCRIPTION OF SYMBOLS 1 Ground, 2 measuring antenna apparatus, 3 support rotation mechanism, 4 to-be-measured object, 5a test radio wave, 5b reflected wave, 6a, 6b, 6c multiple reflected wave, 10 ground, (theta) inclination angle.

Claims (6)

An object to be measured placed on the ground;
A measurement antenna device that transmits a test radio wave toward the object to be measured, receives a reflected wave from the object to be measured, and measures a radar cross-sectional area of the object to be measured;
A radar cross-sectional area measurement system comprising: a support rotation mechanism for supporting and rotating the object to be measured above the ground;
A radar cross-sectional area measurement system, wherein a normal direction of a ground surface in a peripheral area where the measurement object is arranged is set to be different from a projection direction from the measurement object to the ground surface in the peripheral area.   The radar cross-sectional area measurement system according to claim 1, wherein the ground shape of the peripheral area is an inclined plane.   The radar cross-sectional area measurement system according to claim 1, wherein the ground shape of the peripheral area is a curved surface.   The radar cross-sectional area measurement system according to claim 3, wherein the ground shape of the peripheral area is a part of a paraboloid.   The radar cross-sectional area measurement system according to claim 3, wherein the ground shape of the peripheral area is a part of a columnar paraboloid.   The range in which the normal direction differs from the normal direction of the other ground on the ground of the peripheral area includes a projection area from the measurement object when the measurement object rotates. The radar cross-sectional area measurement system according to any one of claims 1 to 5.

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