JPH04328480A - Scanning beam antenna system apparatus - Google Patents

Abstract

PURPOSE:To obtain an antenna system apparatus which conducts sectoral scanning within a plane at a high speed. CONSTITUTION:Two wedges A and B each having a vertical surface and a slanting surface are disposed so that the vertical surface is perpendicular to a reference line of scanning and the axis X. These two wedges A and B are rotated at the same angular velocity and in the reverse direction to each other and parallel beams of an electromagnetic wave are made to pass through the two wedges, whereby a beam scanning in a sectoral shape within a plane is obtained. By selecting the relative initial positions of the two wedges A and B, the tilt of a scanning plane can be selected. Since only a mechanism rotating continuously in the same direction is provided and no mechanism element conducting a reciprocating motion is provided, scanning of high speed can be executed and an apparatus thus obtained is excellent in stability and durability.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention mainly relates to a millimeter wave (hereinafter referred to as "radio wave") having a means for repeating back and forth scanning so that a pencil beam-shaped electromagnetic wave (hereinafter sometimes referred to as "radio wave") draws a fan shape in one plane. This article relates to an antenna system for ``millimeter waves.''

0002

BACKGROUND OF THE INVENTION When millimeter waves are used as a medium to be mounted on a moving body and detect obstacles (hereinafter referred to as "targets") that exist at a close range or a relatively short distance ahead of the vehicle, sensitivity and From the viewpoint of accuracy, it was requested that a pencil beam-shaped radio wave be repeatedly scanned back and forth over an area that spreads in a fan shape in a plane parallel to the running surface in front of it, with the position of the radiating antenna and receiving antenna as the key point. Sometimes. This invention meets this need.

0003

2. Description of the Related Art Conventionally, it has been extremely difficult to control the pointing direction of an antenna and perform so-called beam scanning using millimeter waves. In the field of microwaves, antennas that electronically scan beams, such as phased array antennas, are already in use. However, phased array antennas require an electronically controllable variable phase shifter, but this phase shifter is difficult to obtain with satisfactory characteristics in the millimeter wave band. has not been put into practice.

On the other hand, among the systems that mechanically control the beam direction, conical scanning systems use, for example, the secondary mirror of a Cassegrain antenna that is offset and rotated, or a dielectric between the feed horn and the lens of a lens antenna. Methods such as inserting a body wedge and rotating it are used.

[0005] However, scanning a beam within a certain plane, such as within a horizontal plane or a vertical plane, is a structure unique to millimeter waves in which the antenna, transmitter, and down converter are coupled together by a waveguide. There is a method in which the entire device consisting of the components is mechanically reciprocated, and other methods include, for example, reciprocating a lens in front of the feed horn, or reciprocating a plane mirror in front of the feed horn. The only methods available were to convert the reflected light into a plane wave with a lens, or to convert it into a plane wave with a lens antenna and then apply it to a plane mirror, causing the plane mirror to rotate back and forth.

However, even in the millimeter wave band, the diameter of lenses and reflectors is around 10 cm, so it is difficult to rotate them back and forth at high speed (for example, more than 10 times per second), and even if it is possible, Since long-term continuous operation poses problems in stability and durability, it has been difficult to maintain the same performance over a long period of time.

[0007]

[Problems to be Solved by the Invention] The problem to be solved by the present invention is to obtain a new device that scans a millimeter-wave band pencil beam in a fan shape at high speed within one plane.

[0008]

[Summary of the Invention] This invention provides a dielectric wedge (a dielectric wedge along the beam flux) having a cross-sectional area equal to or larger than the aperture area in front (target side) of an antenna that radiates electromagnetic waves (for example, a parabolic antenna, a lens antenna). A beam that scans back and forth in a fan shape within a plane by placing two lenses with a wedge-shaped cross section (hereinafter referred to as "wedges") and rotating these two wedges in opposite directions at the same angular velocity. It is.

The inclination of the scanning plane with respect to the horizontal plane is determined by the relative positions of the two wedges relative to each other in space, and the opening angle of the scanning range (corresponding to the sector opening angle) is determined by the permittivity of the wedges. and the apex angle of the wedge. The rate of repetition of the scan is determined by the angular velocity of the wedge rotation.

0010

According to the present invention, a beam can be scanned in a practical plane. Furthermore, it is possible to achieve a scanning angle range of 12 times or more the beam width at a scanning speed of 10 times per second or more, which was extremely difficult to achieve with the prior art.

[0011] This invention has a mechanism part that rotates the wedges, but since each wedge simply rotates continuously in the same direction around its axis of rotation, such a mechanism is less efficient than a mechanism that rotates back and forth. Much easier to manufacture,
It has good stability and durability, and can maintain constant performance over a long period of time. Since the wedge can be rotated continuously at high speed, reciprocating fan-shaped scanning can be performed continuously at high speed.

0012

Embodiment (Basic Configuration) FIG. 1 shows a first case of the basic configuration of an embodiment of the present invention.

[0013] Radio waves pass from the transmitter and down converter through the horn antenna, and from the radio lens, they become a parallel wave packet in front of it, a so-called pencil beam, and are radiated in the direction of the thick white arrow (forward: toward the target). It is known that this will happen, and this is assumed.

A signal from the control circuit passes through the drive circuit to rotate the motor, and the wedges WA and WB are respectively aligned with the scanning reference line (one directional line assumed in the horizontal plane, for example, in the direction of the trailing line of the moving object). (hereinafter referred to as the "X-axis").

[0015] Wedges WA and WB are made in the same shape using a dielectric material.

When the beam bundle φ passes through the wedges WA and WB, the directional line φax of the beam bundle φ swings and deviates from the X-axis.

FIG. 2 is a diagram illustrating the arrangement relationship between wedges WA and WB. The two surfaces sandwiching the apex angle θ are wedge W
Regarding A as A1 and A2, regarding wedge WB B
1, B2. Also, place the wedge on the radio lens side with W.
Let A be the wedge placed on the target side and WB.

One surface (hereinafter referred to as the "vertical surface") sandwiching the apex angle θ of wedges WA and WB, A1 and B1, is a Y-Z plane perpendicular to the X-axis (the Y-axis is a horizontal plane and perpendicular to the X-axis). and the Z axis coincides with the vertical line). Also, wedge WA, W
Another surface that sandwiches the apex angle of B (hereinafter referred to as the "slope")
A2 and B2 are arranged so as to face each other. In other words, the two wedges WA and WB have vertical surfaces A1 and WB located on the outside.
B1 is parallel and both are perpendicular to the X axis, and slopes A2 and B2
are on the inside facing each other.

The apex angles θ of the wedges WA and WB have the same value when viewed in any cross section perpendicular to both the vertical plane and the slope.

Furthermore, the two wedges WA and WB are arranged so that the closest points of their slopes A2 and B2 are separated by a distance g (design value) so that they do not come into contact with each other during rotation.

(Example 1) FIG. 3 shows wedges WA and WB.
This shows how the beam flux φ is deflected in the horizontal plane due to the rotation of . In this figure, wedges WA and WB are continuously rotating in opposite directions at the same angular velocity. The angular velocity is indicated by ω for the wedge WA and (−ω) for the wedge WB, respectively.

The beam flux φ is incident as a parallel wave flux from the left side of the figure parallel to the X-axis and perpendicularly to the vertical surface A1 of the wedge WA.

FIG. 3(a) is a view of the XY plane viewed from above, and wedges WA and WB have both slopes A2 and B2 included in the vertical plane, and both apexes (apex angle θ). (hereinafter the same shall apply) are on the same side with respect to the X-axis. This attitude is one of the regulating conditions for scanning the beam bundle φ in the horizontal plane. At this time, both bottoms (the top and the reflective side) have the shortest distance g.

In the case of this figure, the beam bundle φ (direction line φax of the beam bundle φ) is
It is refracted in the Y plane and exits from the B1 plane at an angle obliquely refracted to the left with respect to the X axis relative to the front of the radiation. In this case, the beam bundle φ is not refracted in the X-Z plane.

FIG. 3(b) shows the situation when the wedges WA and WB have each rotated 90 degrees from the state of FIG. 3(a), as viewed from the side in the X-Z plane. In the case of It appears with a deviation in the Z-axis plane. In the positional relationship shown in this figure, the beam flux φ is not biased in the X-Y plane.

FIG. 3(c) shows the situation when the wedges WA and WB have further rotated by 90 degrees from the state of FIG. 3(b), as seen from above in the XY plane, as in the case of FIG. 3(a). This is what is shown. In this situation, the same expression of the restriction condition as in the case of (a) for scanning the beam bundle φ in the horizontal plane is realized in a different attitude. In this case, the beam flux φ is A
It is refracted in the X-Y plane by the 2, B2, and B1 planes, and is refracted diagonally forward to the right with respect to the X axis from the B1 plane relative to the front of the radiation, but is not refracted in the X-Z plane. .

FIG. 3(d) shows the situation when the wedges WA and WB have each further rotated by 90 degrees from the state of (c), when viewed from the side in the same direction as in (b) on the X-Z plane. This figure shows the situation in which the beam flux φ is
Refracted within the X-Z plane by the A2 and B2 planes, perpendicular to the front of the radiation from the B1 plane and parallel to the X axis, but along the Z axis with respect to the X axis from the position of incidence on the A1 plane, and ( The deviation in case b) is a deviation to a symmetrical position with respect to the X axis. In this figure, the beam bundle φ is not biased in the X-Y plane.

When the wedges WA and WB are further rotated by 90 degrees from the state shown in FIG. 3(d), they return to the state shown in FIG. 3(a).

The beam flux φ (directional line φax) is shown in FIG.
) and (c), the largest deviation occurs in the X-Y plane, and in the cases of FIGS. 3(b) and (d), the largest deviation occurs in the X-Z plane.

[0030] Here, the permittivity of wedges WA and WB is ε
From this and the apex angle θ, the beam flux φ (directional line φax)
Find the maximum value θT of the amount of deviation in the X-Y plane.

In FIG. 4, referring to FIG. 3(a), the beam flux φ incident from the left along the X-axis perpendicularly to the vertical surface A1 of the wedge WA is located at point a on the slope A2 of the wedge. W.B.
The beam is refracted at point b on the slope B2 and point c on the vertical plane B1, and its directional line φax exits in the direction d.

∠Xab=∠Xap=θ1 (1)
∠pbq=∠θ2 …………(2)∠qc
If d=θ3 (3), then θT =θ1 +θ2 +θ3 (4). Here,

[0033]

[Math 1]

[0034] However, in Snell's equation that gives the law of refraction of electromagnetic waves, (a) the dielectric constant of air (including the case of vacuum; the same applies in (b) and (c) below) is 1 (b) Air and wedge WA , WB are respectively 1. (c) The conductivity of air and wedges WA and WB is 0, respectively.

For example, if ε = 7.3 (selected value), the material (obtained from aluminum nitride, for example), and θ = 5.4°.
If we make a wedge with (design value), θ1 = 9.33°,
θ2 = -2.48°, θ3 = 11.95°,
θT = 18.8°. Therefore, as shown in Fig. 5, the directional line φax of the beam bundle φ is
It is possible to scan over a range of 18.8° on one side of the reference line and 37.6° on both sides of the reference line. This is the front 10 on the X axis
We obtain an opening distance of 6.8 m at m.

In practice, it is difficult to make the beam flux φ an ideal parallel wave flux, but in the millimeter wave band,
Since it is possible to make the beam width (half width) about 3 degrees with an antenna using a radio wave lens with a diameter of about 10 cm,
If wedges WA and WB as described above are used in front of an antenna having such a radio wave lens, it becomes possible to scan a range approximately 12 times the beam width at an aperture angle.

[0037] Also, the X-Z of the beam flux φ (direction line φax)
Find the maximum in-plane deviation.

In this case, referring to FIG. 3(b), the slopes A1 and B1 of the wedges WA and WB are parallel and are both perpendicular to the X-Z plane.

According to FIG. 6, the angle at which the beam bundle φ, which is perpendicularly incident on the vertical surface A1 parallel to the X-axis from the left and exits the slope A2, is refracted at point a is θ1 in the case of FIG. It enters the slope B2 at point b, is bent, and exits vertically from the vertical plane B1 at point c.

If the foot of the perpendicular line drawn from point b to the
L)・tanθ1 (8). Here, if the point on the X-axis of slope B2 is h, then L is the distance between point a on the X-axis and h
The distance between the two points (design value), ΔL is the distance between the h point and the H point on the X axis, and θ1 is θ1 in the case of FIG.

Furthermore, from FIG. 6, ΔL=δ・tanθ (9), so if we put this into equation (8), we get

0042
]

[Math 2]

##EQU1## is obtained.

[0044] Here, assuming L = 20 mm (design value),
Using the previous values of θ=5.4° and θ1 =9.33°, δ=3.34 mm is obtained. This is a value that poses no problem as a practical plane for a target 10 m ahead.

Incidentally, the denominator of equation (10) is required to be positive, but this is because the beam flux φ can exit from the slope A2 of the wedge WA at the refraction point on the A2 surface. This corresponds to the fact that the incident angle θ at a certain point a is shown to be less than or equal to Brewster's critical angle. When considering the path of electromagnetic waves in the opposite direction, Wedge W
The same applies to point b on the slope B2 of B.

(Example 2) In each of FIGS. 3(a) to 3(d), the Y-axis and Z-axis are interchanged, and "X-Y plane viewed from above" is replaced with "X-Z plane viewed from above". "View from the side", "X"
- Understand (a) to (d) by changing “viewing the Z plane from the side” to “viewing the If the angular relationship is understood as shown in FIGS. 3(a) to 3(d), it will be understood that the beam bundle φ is scanned in the X-Z plane. This is shown in Figure 7. Beam flux φ (directivity φax
) can be understood in accordance with the case of deviation in the horizontal plane as shown in FIG.

In the case of this embodiment, the regulating conditions for scanning the beam bundle φ in the X-Z plane can be expressed by the postures shown in (a) and (c). (a) and (c) are different postures showing the content of regulation using the same expression.

(Embodiment 3) Using the configurations shown in FIGS. 1, 2, and 3, conical scanning can be performed by rotating two wedges WA and WB in the same direction and at the same angular velocity. In conical scanning when only one wedge is rotated, the scanning angle (vertical angle of the cone) is fixed, but the relative positional relationship between the two wedges WA and WB (positional relationship between slopes) By changing , the scanning cone apex angle can be continuously changed from zero to θT (θT in Example 1). Conical scanning can be used for automatic tracking and detection of moving targets.

(Embodiment 4) In the configuration shown in FIGS. 1 and 2, if the two wedges WA and WB are rotated in the same direction at different angular velocities, the beam scans in a spiral manner. Spiral scanning can be used to search for targets.

(Embodiment 5) Using two sets of devices configured as shown in FIGS. 1 and 2, one set scans in a horizontal plane using the X-axis as a reference line, and the other set scans a vertical plane using the X-axis as a reference line. By scanning in the X-Z plane, it becomes possible to scan spatially and three-dimensionally. By scanning a millimeter-wave beam with a narrow beam width three-dimensionally and receiving the echoes from the target, it is possible to display the image of the target as a two-dimensional drawing in the Y-Z plane. be.

Furthermore, by using a pulse wave with a short time width as a radiation beam, resolution in the front-rear direction (X-axis direction: the direction of progress and reflection of the pulse wave packet) can be obtained.
It is also possible to display a Y-Z three-dimensional image. Even in weather conditions such as dense fog where the target cannot be seen using visible light, it is possible to obtain an image in front of a moving object using millimeter or submillimeter waves, whereas microwaves have long wavelengths and cannot be expected to be as clear. In the region, the wavelength becomes shorter and the clarity improves, and there is even less scattering than in the far-infrared region, so it is possible to display a clear image unique to the millimeter wave or submillimeter wave region.

Furthermore, when the beam is scanned horizontally for the purpose of detecting obstacles in front of the moving body, pitching of the moving body may cause the beam to swing up and down and be directed toward the running surface or in the opposite direction. However, if two sets of the apparatus of the present invention are used, one set scans in the horizontal direction, and the other set scans while controlling to cancel the vertical movement of the beam due to pitching of the moving body. This is very convenient because the beam can always scan parallel to the running surface regardless of pitching of the moving body. As described above, by using a plurality of devices of the present invention in combination, high-speed scanning can be performed by cubically emitting a millimeter wave beam and controlling its direction.

(Another basic configuration) (1) Wedges WA, W
The arrangement of B may be such that the vertical surfaces A1 and B1 face each other on the inside, and the slopes A2 and B2 face on the outside. Also in this case, the vertical planes A1 and B1 are arranged perpendicular to the X-axis, which is the scanning reference line. This is shown in FIG. Alternatively, regarding refraction, the same results as analyzed in FIGS. 3 and 7 can be obtained.

(2) Furthermore, wedges WA and WB are shown in FIG.
The vertical surfaces A1, B1 and the slopes A2, B2 may be arranged alternately, as shown in FIG. Also in this case, the vertical planes A1 and B1 are arranged perpendicular to the X-axis, which is the reference line. Regarding refraction, the same results as those analyzed in FIGS. 3 and 7 can be obtained.

(3) Furthermore, the wedges WA and WB are arranged as shown in FIG. 10, with the slopes A2 and B2 oriented in the opposite direction to that shown in FIG. 9, and the vertical surfaces A1 and B1 are oriented with respect to the It may also be vertical. The refraction is the same as in FIGS. 3 and 7.

(Summary of Examples) (1) This invention provides 2
The relationship between the postures of the slopes of the two wedges is shown in Figures 3(a) and 7(a).
), or an intermediate state between FIG. 3(c) and FIG. 7(c), the scanning plane moves along the X-axis with an inclination from the horizontal plane corresponding to that state (which can be understood as the initial state). It becomes a surface that includes.

(2) The postures of (a) and (c) in FIG. 3 can be regulated by the same expression, and the postures of (b) and (c) of FIG.
The posture of d) can be regulated by the same expression, different from that of (a) and (c), but if any one of (a), (b), (c) or (d) in Fig. 3 is regulated. If a regulation is imposed, the substantive meaning of that regulation will also be valid in the other three cases, even if the wording of the expression changes.

Similarly, (a), (b), (c), (
If any one of d) is regulated, its substantive meaning will be valid in the other three cases.

In addition, (a), (b), (c), (d) of FIG.
) and FIGS. 7(a), (b), (c), and (d) do not have the same mutual posture of the two wedges.

[0060] In implementation, an adjustment circuit is created in the drive circuit of the motor that drives each wedge, so that the mutual posture of each wedge can be changed as appropriate by adjusting it by electrical operation. It is convenient to do so. Of course, the angle may be changed and set by directly operating the wedge mount.

(3) The present invention can be implemented without restrictions on wavelength ranges such as radio waves or light waves. The material of the wedge is
Select and adopt depending on the nature and wavelength of the waves used.

(4) It is also possible to implement the present invention using sound waves/ultrasound waves.

(5) If the wedge is made of an object having a different refractive index from the surrounding medium surrounding the wedge, the environment for implementing the present invention is not limited to air. For example, ultrasound opens the door to underwater implementation.

[0064] Some artificial dielectric materials have variable dielectric constants that are less than 1, so it is possible to create wedges using such materials. The shape of the wedge may be the same as in FIGS. 2, 8, 9, and 10, although the specific value of the apex angle is determined depending on the implementation.
Regarding refraction, the same results as the analyzes shown in FIGS. 3 and 7 can be obtained.

(6) The signal waves to be used can be implemented not only with a single frequency but also with a mixture of various frequencies. This invention is applicable for each frequency.

For example, when it is desired to visually check the scanning situation with the human eye due to practical requirements, it is useful to use light waves in the visible range together with the millimeter waves or submillimeter waves used for the original scanning.

(7) The mobile object may be a vehicle on land, a vehicle on track, a ship on water or underwater, etc., and it is effective for short-range radars of these. It also opens the door to short-range radars for small airplanes, etc.

(8) Since scanning is performed in a fan shape,
It is also effective in detecting obstacles in front of a curved road, and is expected to be used to quickly find out the situation on the track on the inside of a curve at a required curve point in a train, for example. In this case, by utilizing the fact that the centripetal force received from the orbit is a function of the curvature of the orbit, the magnitude of the centripetal force is sensed and the scanning reference line is directed to the inside of the curve in conjunction with that signal (for example, the antenna If the entire subsequent target side portion is rotated in this manner, it can be expected that the effect of searching inside the curve will be further improved.

(9) The present invention can be applied to both a radiating antenna and a receiving antenna.

[Brief explanation of drawings]

[Figure 1] Explanatory diagram of the example

[Figure 2] Explanatory diagram of the example

[Figure 3] Explanatory diagram of the example

[Figure 4] Explanatory diagram of the example

[Figure 5] Explanatory diagram of the example

[Figure 6] Explanatory diagram of the example

[Figure 7] Explanatory diagram of the example

[Figure 8] Explanatory diagram of the example

[Figure 9] Explanatory diagram of the example

[Fig. 10] Explanatory diagram of the embodiment

[Explanation of symbols]

WA, WB…Wedge
A1...Vertical surface of wedge WA A2...Slope of wedge WA B
1...Vertical plane B2 of wedge WB...Slope θ of wedge WB...Apex angle φ of wedges WA and WB formed by planes A1 and A2, and planes B1 and B2, respectively...Beam bundle
φax... Directional line of beam bundle φ X... Coordinate axis θT that forms an orthogonal coordinate system together with scanning reference line of beam bundle φ Y, Z...X... Directional line φax of beam bundle φ is refracted from scanning reference line X Maximum deviation angle δ... Maximum deviation amount by which the directional line φax of the beam bundle φ moves in parallel from the scanning reference line x

Claims (14)

[Claims] Claim 1: Two wedges made of a material having a refractive index different from that of a surrounding medium are provided during the path of a beam beam, so that the vertical plane of each wedge is aligned with the scanning reference line of the beam beam. The scanning beam is arranged such that the two wedges are perpendicular to each other, and each of the two wedges is configured to rotate about the reference line while keeping each of the vertical planes perpendicular to the reference line. Antenna system equipment. 2. The scanning beam antenna system device according to claim 1, wherein the two wedges are arranged so that their slopes face each other. 3. The scanning beam antenna system device according to claim 1, wherein the two wedges are arranged so that their vertical surfaces face each other. 4. The scanning beam antenna system device according to claim 1, wherein an inclined surface of one wedge faces a vertical surface of the other wedge. 5. The scanning beam antenna system according to claim 2, wherein the two wedges are rotated in opposite directions at the same angular velocity. 6. Claim 2, 3 or 4, characterized in that the two wedges are rotated in the same direction at the same angular velocity.
The scanning beam antenna system device described in . 7. The scanning beam antenna system device according to claim 5, wherein the relative positional relationship of the slopes of each of the two wedges is arbitrarily set. 8. The method according to claim 5 or 7, wherein when the slopes of the two wedges are both in a vertical plane, the tops of the two wedges are on the same side with respect to the reference line. The scanning beam antenna system device described above. [Claim 9] The top of each of the two wedges is on the same side with respect to the reference line when the slopes of each of the two wedges are both perpendicular to a vertical plane including the reference line. A scanning beam antenna system device according to claim 5 or 7. 10. The scanning beam antenna system device according to claim 2, wherein the two wedges are rotated in the same direction at different angular velocities. 11. Claims 1, 2, 3, 4, 5, 7, 8, characterized in that the two sets of devices are arranged so that their reference lines coincide and their scanning planes are orthogonal. Or the scanning beam antenna system device according to 9. 12. The scanning beam antenna system device according to claim 11, wherein the beam flux is a pulse wave. 13. Claims 1, 2, 3, 4, 5, 6, 7, characterized in that the beam flux is an electromagnetic wave.
13. The scanning beam antenna system device according to 8, 9, 10, 11 or 12. 14. Claims 1, 2, 3, 4, 5, characterized in that the beam bundle is based on a sound wave or an ultrasonic wave.
13. The scanning beam antenna system device according to 6, 7, 8, 9, 10, 11 or 12.