JPS60253305A - Reflection factor variable radar reflector - Google Patents

Abstract

PURPOSE:To improve a modulating function to a circular polarized wave by fixing each conductor grid member with rotation of a fixed angle of about 45 deg.C and a parallel state kept to the polarized wave surface of a radio wave reflector and connecting a bias control circuit to both ends of the radio wave reflector. CONSTITUTION:A radio wave relfector 12 and a conductor grid 21 are put approximately in parallel to each other with a distance L1 equal to about lambda/4 compared with the length lambda of a radar wave. Now a right revolving circular polarized wave A radiated from a radar antenna 3 is vertically made incident on a reflection factor variable radar reflector 30. Thus the vertical component of the wave A passes through the grid 21 with virtually no reception of effects. While the phase of the component parallel to the grid 21 passes through the grid 21 with a delay of about pi/2 radians. Then both passed components are synthesized and reach the front surface of the reflector 12 set at the rear side in the form of a horizontal polarized wave. In this case, the delayed phase value can be set at an optional level with proper control of the space between grids 21.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a variable reflectance radar reflector, and in particular to a variable reflectance radar reflector suitable for changing the reflectance for circularly polarized radar waves. Regarding.

[Conventional technology]

In general, radar reflectors are used to improve the reflectance of unspecified small targets and navigational aids to facilitate the detection of such targets.

In recent years, the reflector can be installed by changing its reflectance using the above reflector! (So-called passive telemetry that transmits a certain amount of information from a location to a radar station) I
Research and development regarding J is actively being carried out. In passive telemetry, the reflector itself that transmits information does not emit radio waves, so it does not interfere with other communications, and it does not dissipate power circuits like a normal transmitter, so the device is small and simple. At the same time, the reflector's h￥＠k
It has the excellent advantage that it can be used by unspecified radar stations at the same time by being equipped with a demodulator that can decode it, and therefore it can be used in a wide range of applications for the transmission of constant data such as target identification and environmental information. It is expected.

On the other hand, in Japanese Patent Application No. 54-88519 and No. 54-88520, the applicants have previously proposed that a slot formed in a metal plate be electrically or mechanically brought into a resonant or non-resonant state with respect to a radar plate. By switching, we have proposed a variable reflectance radar reflector that has a relatively wide bandwidth, simple configuration, and easy adjustment.

This variable reflectance radar reflector is useful for linearly polarized waves (horizontal polarized waves) used for general navigation, but
Circularly polarized waves, which are used to remove interference caused by reflections of raindrops, have the disadvantage that, as described below, the change in reflectance is small, making them impractical for practical use.

That is, for circularly polarized waves, for example, as shown in FIG. 6, when a right-handed circularly polarized wave A emitted from the radar antenna 3 enters the metal plate IK, the phase of the reflected wave is reversed and becomes a left-handed circularly polarized wave B.
becomes. This reflected wave from the idle leg is not received by a radar that transmits and receives using the same antenna. In addition, in the slot resonance type variable reflectance radar reflector shown in Japanese Patent Application No. 54-88520 mentioned above, as shown in FIG. ,5
A plurality of switching diodes 6.6... are connected at predetermined intervals to ゜..., and these diodes 6.6... The configuration is such that a predetermined bias voltage is selectively applied from the bias control circuit 7 via the plates 4A, 4A.

The bias control circuit 7ri is composed of a diode 8 and a switch 9, and by opening and opening the switch 9, the diode 6
．． 6. ... is on (ON) or off (OFF) L, the diode 6.6. When ... is ON, each diode 6
．． 6. ...The narrow gap between the two becomes a resonant slot, which is formed so that it is in a non-resonant state when it is OFF.

Diode 6.6 of this variable reflectance radar reflector 4
．． When . Meanwhile, switch 9 is closed (second
(See figure) Said diode 6.6. ... becomes ONL conductive, a resonant slot is formed. At this time, in the circularly polarized wave A emitted from the radar antenna 3, the vertically polarized wave component in the same direction as the resonant slot is reflected (see B1 in Figure 7), and only the horizontally polarized wave component A2 in the direction perpendicular to the resonant slot is reflected. pass. Therefore, the reflected wave will be only the vertically polarized wave component B1, and the incident power will be 1/2. This vertically polarized component B1
When received by the circularly polarized radar antenna 3, an additional 1/2 degree of power is lost due to the structure of the circularly polarized radar antenna 3.
Suppose all the incident waves of fC, f! are reflected. Only the power of V4 at the imaginary reflection level will be received. In practice, the switching diode 6.6.・・・
When * is OFF, the reflection of the horizontally polarized wave component is incomplete due to the existence of a slit, while when it is ON, a part of the horizontally polarized wave component is reflected. For this reason, switching diodes 6.6. The level difference between the reflected waves due to ON and 0FFK became even smaller, and for this reason, the variable reflectance radar reflector 2 shown in Fig. 7 could not fully perform its function for circularly polarized waves. .

[Problem that the invention seeks to solve]

On the other hand, in Japanese Patent Application No. 56-140172, the applicant proposed a variable reflectance radar reflector for both linearly polarized waves and circularly polarized waves, with the intention of improving the above-mentioned disadvantages.

However, for circularly polarized waves, the device disclosed in 'II Application No. 56-140172 divides the beam into a horizontal component and a vertical component and reflects them separately, and the reflectance is only for one component. Since the reflectance is made variable, the difference in the variable level of reflectance is small, and therefore is not necessarily sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the conventional example and to provide a reflective Honmachi-modified radar reflector that can perform an effective modulation operation, particularly for circularly polarized radar waves.

[Means for solving problems]

Therefore, in the present invention, a conductor grating and a radio wave reflector are arranged in front and behind the incoming radar wave at a distance of about 14 wavelengths of the radar wave, and the radio wave reflector is placed in the same plane. a plurality of strip-shaped metal plates disposed between each other, gaps provided between the strip-shaped metal plates, and a plurality of switching devices disposed in each of these gaps to connect the respective strip-shaped metal plates. the conductor grid,
It is formed by a plurality of grating members arranged in i-parallel on the same plane at predetermined intervals, and the whole of each grating member is maintained parallel to the polarization plane of the radio wave reflector. The device is fixed in a state where it is rotated by a predetermined angle after 457 jiJ, and a bias control circuit for controlling the bias voltage applied to the switching diode is connected to both ends of the radio wave reflector. This aims to achieve the above objective.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

1 and 2, 3Fi shows a radar antenna similar to the conventional example described above, and 12 indicates a radio wave reflector and 2
1 each indicates a conductor grid. The radio wave reflector 12 and the conductor grating 21 are arranged substantially parallel to each other and separated from each other by a distance equal to approximately /4 with respect to the wavelength λ of the radar wave.

Among them, in this embodiment, the conductor grating 21 has a vertical plane vc with respect to the arrival direction of the radar wave as shown in the figure.
A plurality of conductive stripes 22 , 22 , . . . . are arranged in a parallel lattice shape at predetermined intervals. Further, in this embodiment, the conductive strip 22 is formed of a metal wire member with +kL, di approximately λ/32, but it may also be formed using metal foil or a nonwoven paint. It may be something. Further, the distance between each of the conductive stripes 22,
is set to 0.38λ in this embodiment. The t'Lfc conductor grating 21 configured in this manner has a function of converting the circularly polarized radar waves transmitted from the radar antenna 3 into linearly polarized waves.

, On the other hand, the radio wave reflector 12#:t located at the rear with respect to the direction of arrival of the radar waves is constructed in substantially the same manner as the conventional variable reflectance radar reflector described above (see FIG. 7). That is, gaps 15, 15, etc., having a predetermined interval are formed between a plurality of strip-shaped metal plates 14, 14, having a predetermined width Latl. The longitudinal direction of this narrow gap 15, 15, . Switching diodes 16, 16, . . . are installed in the narrow gaps 15° 15, .
* are loaded two-dimensionally at a predetermined interval apart. The switching diode 16.16...
The interval L6 is set slightly smaller than h. A bias flt1311 circuit 17 is connected to the gold M plates 14A and 14AK at both ends of the radio wave reflector 12 formed in this manner, and by opening and closing the switch 18 of this bias control circuit 17, the pw source is controlled. 19 is a bias voltage of 1 voltage, each of the switching diodes 16, 16...
. . . is applied in a switching manner. Specifically, when the switch 18 is closed, the switching diode 1
6.16... becomes FiON, and a resonant slot is isometrically formed in the narrow gap 15.15... of each switching diode 16 threshold. Also, when the switch 18 is opened, the switching diode 16.
FL, the radio wave reflector 12 is in a non-resonant state and performs the same reflecting action as a normal Kanahashi reflector commensurate with its area. That is, the t″Lfc radio wave reflector 12 configured in this manner has a function of allowing horizontally polarized wave components to pass when the switching diode 16 is ON, and reflecting an incident wave when the switching diode 16 is OFF.

Next, the overall operation of the above embodiment will be explained based on FIGS. 1 and 2.

Now, when the right-handed circularly polarized wave A emitted from the radar antenna 3 is perpendicularly incident on the variable reflectance radar reflector 3o, this circularly polarized wave AFi conductor grating 21 generates a component perpendicular to the grating. passes through almost unaffected. Further, the phase of the component parallel to the grating passes with a delay of approximately Y2 radians. Then, when the waves of the frequency components that have passed are combined, they reach the front of the rear radio wave reflector 12 as horizontally polarized waves. In this case, the phase value of the delay can be set to any value by appropriately adjusting the grating spacing of the conductor grating 21. FIG. 4 shows experimental results proving the relationship between the phase delay in this case and the dimensions between the conductive gratings.

Here, the switch 18 is open (see Figure 1).
, and switching diode 16°16...
When is in the OFF state, most of the horizontally polarized waves are reflected by the radio wave reflector 12. When this reflected wave returns to the conductor grating 21, the component perpendicular to the grating passes through without being affected, and the component parallel to the grating has a phase difference of approximately /2 Fujian. Pass late. Therefore, when the image wave components of the reflected waves that have passed are combined, a right-handed circularly polarized wave C is obtained, and the incident wave A is reflected without any harm. Therefore, in radar antenna 3,
It is possible to obtain received power at a level corresponding to the radar cross section of the variable reflectance radar reflector 30.

Next, as shown in FIG. 2, when the switch 18 is closed and a predetermined bias voltage is applied to the switching diodes 16, 16, . . . to turn them on, the incident circularly polarized wave Afl, Converted into υ horizontally polarized wave by the grating 21 n
1 through the radio wave reflector 12 through a resonance slot formed in the radio wave reflector 12 (see FIG. 2). Therefore, the circularly polarized wave A1 is not reflected by the variable reflectance radar reflector 30F'i, and the reflected wave is not received by the radar antenna 3.

A2 shows the passing wave in this case.

Actually KH1 said switching diode 16°16...
When . . . is OFF, the polarization of the conductor grating 21 is not completely converted. Therefore, imperfections occur in the reflected circularly polarized waves. Also, at 08 of the switching diode 16.16, incomplete transmission of the horizontally polarized wave converted by the conductor grating 21 occurs, but the interval L of the conductor grating 21? +
By adjusting the mutual spacing between the radio wave reflector 12 and the conductor grating 21, the spacing Ls between the gaps 15 of the radio wave reflector 12, etc., it is possible to improve the variable level difference in reflectance.

Here, the variable reflectance radar reflector 30Fi shown in FIGS. 1 and 2 is effective only for right-handed circularly polarized waves, but for left-handed circularly polarized waves, the conductor grating 21 is Turn to the left when looking from the side.

All you have to do is install it at an angle of radian.

According to the nine embodiments described above, it is possible to obtain a higher level of modulation factor for circularly polarized waves than the conventional variable reflectance radar reflector, so it is very useful for passive telemetry using circularly polarized waves. It is valid.

Moreover, the overall configuration is small, simple, and inexpensive, and
Since a switching diode is used to change the reflectance, the response speed is fast, and since multiple switching diodes are inserted in series between the strip-shaped metal plates, the power resistance is improved. be able to.

Next, FIG. 3 shows another embodiment in which the wave lens is equipped with the variable reflectance radar reflector for in-hole polarization shown in the above embodiment. In the figure, 40 is a radio wave lens such as a Luneberg lens made of dielectric material. When a radar wave is incident from the center line direction of this radio wave lens 40, it is focused at an antisymmetric point P. In this case, this focal point PK
When equipped with a reflector, the light passes through the radio wave lens 40 again and is reflected in the incident direction. Therefore, as shown in FIG. 3, if a conductor grating 21A and a radio wave reflector 22A similar to those described above are provided facing each other at a predetermined interval on the inner and outer shells near the focal plane of the radio wave lens 40, the switching Diode 26A, 26A.

By turning ON and OFF . . . , the same reflectance variable effect as in the first embodiment described above can be performed on wide-angle incident radar waves (circularly polarized waves) K.

Therefore, the other embodiments have a wide range of applications, such as being able to target mobile stations such as ships.

In this case, when comparing the degree of modulation between the above embodiment and the conventional example using the metal reflector as a reference, it is found that the conventional example has a modulation degree of about 6 dB, while the above embodiment has an Fi < 11 dB as shown in FIG.
It was possible to obtain a modulation degree of more than (dB). This fifth
The figure shows experimental data of the reflection pattern of the above-mentioned other example, and the horizontal axis indicates the rotation angle (degrees) about the radio wave reflector of the variable reflector for circularly polarized waves in this example.

〔Effect of the invention〕

As described above, according to the present invention, the reflectance of circularly polarized radar waves can be varied significantly,
Therefore, if the reflectance is changed by the bias control circuit according to the information sent to the outside, the radar station demodulates the reflected radar waves, so that the radar station can always maintain normal operation even under weather conditions such as rain and fog. It is possible to provide an unprecedented variable reflectance radar reflector that enables passive telemetry.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
Figure 3 is an explanatory diagram showing another embodiment, Figures 4 and 5 are diagrams showing experimental values, and Figures 6 and 7 are diagrams showing conventional examples. It is a diagram. DESCRIPTION OF SYMBOLS 12... Radio wave reflector, 14, 14A... Strip-shaped metal plate, 15... Slit, 16... Switching diode, 17... Bias control circuit, 21... Conductor grid, 22... ...Grid member. Patent applicant: Nozomi Hasebe (and 1 other person) Figure 3/7 Figure 4 Interval (mrn), -□ Figure 5 Rotation P4 (false) □

Claims (1)

[Claims] (1) A conductor grating and a radio wave reflector are arranged in front and behind the incoming radar wave at a distance of about 14 wavelengths of the radar wave, and the radio wave reflector is arranged on the same plane. A plurality of strip-shaped metal plates provided, gaps provided between the strip-shaped metal plates, and a plurality of switching diodes arranged in each of these gaps and connecting the respective strip-shaped metal plates. The conductor grating is formed by a plurality of grating members arranged substantially parallel on the same plane at predetermined intervals, and each grating member is entirely aligned with the polarization plane of the radio wave reflector. 45 while maintaining a parallel state to
The variable reflectance radar is fixed in a state where it is rotated by a predetermined angle back and forth, and is connected to both ends Kri of the radio wave reflector and a bias control circuit that controls a bias voltage applied to the switching diode. reflector.