JP7654330B2 - Antenna Device - Google Patents

Description

This invention relates to an antenna device, for example, to technology suitable for use in satellite communication antennas mounted on various mobile objects.

A conventional antenna for scanning radio waves on multiple channels is known to be an antenna device that is configured by combining multiple subarrays, each of which has multiple element antennas, a phase shifter that controls the phase of the received signal from each element antenna, and a combiner that combines the multiple phase-controlled received signals (see Patent Document 1).

JP 2003-168912 A

However, in the antenna device of Patent Document 1, a considerable number of phase shifters are required to be provided in correspondence with each of the multiple element antennas, which results in a complex device configuration and increased costs.

Therefore, the objective of this invention is to provide an antenna device that can scan beams in all directions without requiring a phase shifter.

In order to solve the above problem, the antenna device according to the present invention has a plane wave generating unit, an antenna unit, a first rotating unit, and a second rotating unit, the plane wave generating unit has a probe that radiates electromagnetic waves, and a main reflector and a sub-reflector that form a Cassegrain structure that converts the cylindrical electromagnetic waves radiated from the probe into plane electromagnetic waves, the antenna unit has a feed array that includes a plate-shaped base and a plurality of radiating stubs that are formed as slots in a row in the base and are arranged in parallel at equal intervals, and the first rotating unit rotates the plane wave generating unit and the antenna unit together around the probe as a center of rotation to perform beam scanning in the azimuth angle direction, and the second rotating unit rotates the antenna unit relative to the plane wave generating unit around the probe as a center of rotation to tilt the wavefront of the plane wave electromagnetic wave incident on the base of the antenna unit, thereby performing beam scanning in the altitude angle direction.

The antenna device according to the present invention may be configured such that the plane wave generating section has a folded waveguide including a lower layer waveguide and an upper layer waveguide that are stacked and each of which constitutes a parallel plate line, the Cassegrain structure is provided within the lower layer waveguide, and the antenna section is provided on the upper layer waveguide side.

The antenna device of this invention performs beam scanning in the azimuth direction by rotating the plane wave generating unit and the antenna unit together, and performs beam scanning in the altitude direction by rotating the antenna unit relative to the plane wave generating unit and tilting the wavefront of the electromagnetic plane wave incident on the base of the antenna unit. This makes it possible to scan the beam in all directions without the need for a phase shifter, and also makes it possible to reduce the cost of the antenna device.

The antenna device of the present invention also provides probe power feeding from the center of rotation of the plane wave generating unit and the antenna unit, making it possible to further simplify the configuration of the antenna device.

When the plane wave generating section of the antenna device according to the present invention has a folded waveguide, it is possible to make the antenna device more compact.

1A and 1B are diagrams illustrating a schematic configuration of an antenna device according to an embodiment of the present invention, in which (A) is a vertical cross-sectional view, and (B) is a plan view. 2 is a diagram illustrating a Cassegrain structure of a plane wave generating portion of the antenna device of FIG. 1 . FIG. 2 is a perspective view showing a schematic configuration of an antenna section (feed array) of the antenna device of FIG. 1 . 2A and 2B are diagrams illustrating the directivity in the xy plane of the antenna device of FIG. 1. FIG. 2A is a diagram illustrating the case where the radiation stubs are excited in phase, and FIG. 2B is a diagram illustrating the case where the radiation stubs are excited with a phase difference. 2 is a diagram showing an example of a state in which radiation stubs of an antenna section (feed array) of the antenna device of FIG. 1 are excited with a phase difference. FIG.

The present invention will be described below based on the illustrated embodiment. In this description, the structure of the antenna device 1 is associated with the x-axis, y-axis, and z-axis directions of a three-dimensional Cartesian coordinate system defined by mutually orthogonal x-axis, y-axis, and z-axis as shown in FIG. 1. In this invention, the plane wave generating unit 2 and the antenna unit 3 are configured to be rotatable along the yz plane, and the state in which the plane wave generating unit 2 and the antenna unit 3 are in the positions shown in FIG. 1 with respect to the x-axis, y-axis, and z-axis directions is referred to as the "state of FIG. 1". In addition, each figure is merely a diagram for explaining the schematic configuration and function of the antenna device 1, and does not strictly represent the detailed structure of each part or the dimensional relationships between them.

Figure 1 is a diagram showing the schematic configuration of an antenna device 1 according to an embodiment of the present invention. The antenna device 1 according to the embodiment mainly has a plane wave generating unit 2, an antenna unit 3, a first rotating unit (not shown), a second rotating unit (not shown), and a control unit (not shown).

The antenna device 1 according to this embodiment has a plane wave generating section 2, an antenna section 3, a first rotating section, and a second rotating section. The plane wave generating section 2 has a probe 28 that radiates electromagnetic waves, and a main reflector 26 and a sub-reflector 27 that form a Cassegrain structure that converts the cylindrical electromagnetic waves radiated from the probe 28 into plane electromagnetic waves. The antenna section 3 has a plate-shaped base 311 and slots formed in a row in the base 311, which are arranged in parallel and spaced apart from each other at equal intervals. The antenna has a feed array 31 with multiple radiation stubs 312, and the first rotating part rotates the plane wave generating part 2 and the antenna part 3 together around the probe 28 as the center of rotation to perform beam scanning in the azimuth direction, and the second rotating part rotates the antenna part 3 relative to the plane wave generating part 2 around the probe 28 as the center of rotation to tilt the wavefront of the electromagnetic wave of the plane wave incident on the base part 311 of the antenna part 3 to perform beam scanning in the altitude direction.

The antenna device 1 according to this embodiment also has a folded waveguide in which the plane wave generating section 2 includes a lower layer waveguide 21 and an upper layer waveguide 22 that are stacked and each constitute a parallel plate line, the Cassegrain structure is provided within the lower layer waveguide 21, and the antenna section 3 is provided on the upper layer waveguide 22 side.

The plane wave generating unit 2 is a mechanism that functions as a plane wave generating mechanism, and mainly includes a lower layer waveguide 21, an upper layer waveguide 22, a folding section 23, a reflector 24, a conductor plate 25, a main reflector 26, a sub-reflector 27, a probe 28, and a choke 29 (see Figures 1 and 2). The plane wave generating unit 2 is configured to be rotatable along the yz plane by the first rotating section.

The lower waveguide 21 and the upper waveguide 22 are rectangular waveguides with a wide wall width (i.e., width in the y-axis direction in the state of FIG. 1; in other words, horizontal width) of a and a narrow wall width (i.e., width in the x-axis direction; in other words, height) of b when viewed from the xy plane in the state of FIG. 1, folded back 180° along the wide wall width (i.e., along the y-axis direction in the state of FIG. 1) and stacked in the x-axis direction. The lower waveguide 21 and the upper waveguide 22 each constitute a parallel plate line.

The folded portion 23 is formed in a rectangular shape with a width in the y-axis direction (in other words, horizontal width) of a and a width in the x-axis direction (in other words, height) of 2×b when viewed in the xy plane in the state shown in FIG. 1, and connects the lower waveguide 21 and the upper waveguide 22.

A reflector 24 is formed on the surface of the folded portion 23 that faces the lower waveguide 21 and the upper waveguide 22 (i.e., the inner surface along the xy plane).

The conductor plate 25 is disposed along the yz plane between the lower waveguide 21 and the upper waveguide 22 to separate the lower waveguide 21 and the upper waveguide 22, and serves as a common wall for the lower waveguide 21 and the upper waveguide 22. The end of the conductor plate 25 on the folded section 23 side is spaced from the reflector 24, and an opening window is provided in the folded section 23 for the lower waveguide 21 and the upper waveguide 22.

The lower waveguide 21, upper waveguide 22, folded section 23, reflector 24, and conductor plate 25 constitute a folded waveguide, and the wide wall width a, narrow wall width b, and the distance between the end of the conductor plate 25 and the reflector 24 are appropriately set based on the free space wavelength and propagation mode of the electromagnetic waves propagating through the parallel plate line.

The main reflector 26 functions as a concave mirror with a Cassegrain structure, is formed in a parabolic shape when viewed in the yz plane, and is provided inside the lower waveguide 21. The opening dimension of the main reflector 26 is L [m], and the focal point is f2. In the example shown in the figure, L = a (where a is the wide wall surface width of the lower waveguide 21 and the upper waveguide 22). The aperture angle at which the entire main reflector 26 is viewed from the focal point f2 is set to, for example, any angle within the range of approximately 120° to 180°.

The sub-reflector 27 functions as a convex mirror with a Cassegrain structure, is formed in a hyperbolic shape in the yz plane, and is provided in the lower waveguide 21. One of the two focal points of the sub-reflector 27, focus f1, coincides with the phase center (also the rotation center position in the planar view of the plane wave generating unit 2 and the antenna unit 3) of the cylindrical wave (in other words, a hyperbola) emitted from the probe 28, and the other coincides with focus f2 of the main reflector 26.

The electromagnetic wave (in other words, the RF (Radio Frequency) signal) is supplied to the lower waveguide 21 by the probe 28. The probe 28 is disposed at the center of rotation of the plane wave generating unit 2 and the antenna unit 3 in a plan view (i.e., in the yz plane view).

A choke 29 is provided near the probe 28 on one side in the z-axis direction in the state of FIG. 1 (the side opposite the direction of the z-axis arrow in the state of FIG. 1). The choke 29 functions to direct the radiation direction of the probe 28 toward the secondary reflector 27 disposed on the other side of the probe 28 in the z-axis direction in the state of FIG. 1 (the side in the direction of the z-axis arrow in the state of FIG. 1).

The choke depth s of the choke 29 as seen from the probe 28 is adjusted to satisfy s = λ/4, where λ is the free space wavelength of the electromagnetic wave (RF signal).

The electromagnetic wave (which is a cylindrical wave) emitted from the probe 28 is converted into a plane wave by reflection from the subreflector 27 and the main reflector 26, and propagates in the lower waveguide 21 along the z-axis direction in the state shown in FIG. 1 in the direction of the z-axis arrow, passes through the turn-back section 23, and propagates in the upper waveguide 22 along the z-axis direction in the state shown in FIG. 1 in the opposite direction to the direction of the z-axis arrow. The z-axis direction for the plane wave generating section 2 and the antenna section 3 in the state shown in FIG. 1 is called the "electromagnetic wave propagation direction."

The probe 28 is electrically connected to, for example, a coaxial connector (not shown) that functions as an antenna port (in other words, an input/output port).

The structure/configuration of the coaxial connector is not limited to a specific structure/configuration in this invention, so a detailed description will be omitted, but the coaxial connector may have, for example, an inner conductor that is electrically connected to the probe 28 (via an electrical line if necessary) and receives a signal (SIG) from the inner conductor of the coaxial cable (not shown), and an outer conductor that is electrically connected to the wall of the lower waveguide 21 and receives a signal (e.g., GND) from the outer conductor of the coaxial cable, and may be structured/configured to supply an RF signal (in other words, a wireless communication wave) to the probe 28.

The antenna unit 3 has a feed array 31 as its main component. The antenna unit 3 is provided so as to be rotatable along the yz plane relative to the plane wave generating unit 2 by the second rotating unit. The center of rotation of the plane wave generating unit 2 in a planar view and the center of rotation of the antenna unit 3 in a planar view coincide with each other.

The feed array 31 includes a base 311 formed of a conductive material in the shape of a circular plate in the yz-plane, and a number of radiating stubs 312 (see also FIG. 3).

The multiple radiation stubs 312 are each formed as a row of slots in the base 311. The multiple radiation stubs 312 are arranged parallel to each other in their respective longitudinal directions (i.e., the y-axis direction in the state of FIG. 1) and spaced apart from each other at equal intervals D in a direction perpendicular to each longitudinal direction (i.e., the z-axis direction in the state of FIG. 1).

The mutual spacing D between the radiation stubs 312 arranged consecutively in a direction perpendicular to each other's longitudinal direction (in other words, their own) is adjusted to satisfy λ/2≦D<λ, where λ is the free space wavelength of the electromagnetic wave (RF signal).

The feed array 31 is circular in the yz plane and has multiple elongated slots formed to define multiple radiating stubs 312.

The antenna unit 3 rotates along the yz plane relative to the plane wave generating unit 2 while the surface of the base 311 opposite the side indicated by the x-axis arrow in the figure comes into contact with and slides against the end surface of the plane wave generating unit 2.

In addition, each of the radiating stubs 312 may be buried in a dielectric (in other words, filled with a dielectric).

Here, each opening (i.e., an elongated slot) as the radiating stub 312 has no conductive shielding and allows electromagnetic energy to propagate through the opening as the radiating stub 312, thereby defining the antenna radiation pattern.

A plane wave/electromagnetic wave (RF signal) propagates in the electromagnetic wave propagation direction (i.e., the z-axis direction in the state of FIG. 1) within the upper waveguide 22 of the plane wave generating unit 2, and the plane wave/electromagnetic wave (RF signal) excites a displacement current in the electromagnetic wave propagation direction, which is the direction in which the plane wave/electromagnetic wave (RF signal) propagates, in the feed array 31 (specifically, the base 311). The displacement current in the electromagnetic wave propagation direction then excites an equivalent electromagnetic wave that travels along the x-axis direction toward the radiating stub 312 and is radiated into free space. The RF signal then passes through the radiating stub 312 of the feed array 31 and is radiated in the form of a plane wave.

The feed array 31 having the above configuration corresponds to a part of a structure also called a continuous transverse stub (CTS) antenna, and the function of the feed array 31 is described, for example, in "The Continuous Transverse (CTS) Array: Basic Theory, Experiment, and Application" (Milroy, W.W. "Proceedings of the Antenna Applications Symposium Held on 25-27 September 1991. Volume 1" AD-A253 682, pp. 253-283) as well as in JP-A-2006-522561, U.S. Patent No. 6,281,838, U.S. Patent No. 5,757,379, U.S. Patent No. 5,483,248, U.S. Patent No. 5,379,007, and U.S. Patent No. 5,266,961.

The first rotating unit (not shown) rotates the plane wave generating unit 2 along the yz plane with the probe 28 (or, more specifically, the phase center of the cylindrical wave/electromagnetic wave emitted from the probe 28) as the center of rotation when viewed in the yz plane.

The second rotating part (not shown) rotates the antenna part 3 along the yz plane with the probe 28 (or more specifically, the phase center of the cylindrical wave/electromagnetic wave emitted from the probe 28) as the center of rotation when viewed in the yz plane.

The first and second rotating parts are configured as mechanisms including, for example, a holding mechanism/guide mechanism that rotatably supports the plane wave generating unit 2 and the antenna unit 3 around the probe 28 as the center of rotation, as well as a motor, and drive the plane wave generating unit 2 and the antenna unit 3 to rotate along the yz plane.

When the first rotating part rotates the plane wave generating part 2, the antenna part 3 also rotates, and when the second rotating part rotates the antenna part 3, only the antenna part 3 rotates. In other words, when the first rotating part is operated, the plane wave generating part 2 and the antenna part 3 rotate together, and when the second rotating part is operated, the antenna part 3 rotates independently.

The drive of the motors of the first rotating unit and the second rotating unit is controlled by a control unit (not shown), i.e., the degree of rotation of the plane wave generating unit 2 and the degree of rotation of the feed array 31 relative to the plane wave generating unit 2 are each controlled by the control unit.

The antenna device 1 performs beam scanning in the azimuth (AZ) direction and elevation (EL) direction. The azimuth (AZ) angle is an angle defined with the north or south direction as 0° and clockwise as positive. The elevation (EL) angle is an angle defined with the horizon as 0° and heading toward the zenith.

The antenna device 1 performs beam scanning in the azimuth (AZ) direction by rotating the plane wave generating unit 2 (and the antenna unit 3) using the first rotating unit.

The antenna device 1 also rotates the antenna unit 3 relative to the plane wave generating unit 2 using the second rotating unit (in other words, rotates the antenna unit 3 independently), thereby performing beam scanning in the elevation angle (EL) direction.

Specifically, by controlling the degree of rotation of the feed array 31 of the antenna unit 3 relative to the plane wave generating unit 2, the degree of longitudinal inclination of each of the multiple radiating stubs 312 of the feed array 31 relative to the wavefront of the electromagnetic wave propagating along the electromagnetic wave propagation direction within the upper waveguide 22 of the plane wave generating unit 2 is changed, and a tilt is imparted to the wavefront of the electromagnetic wave incident on the feed array 31 (specifically, the base 311), thereby performing beam scanning in the elevation angle (EL) direction.

That is, by using the oblique incidence of the guided mode propagating to the feed array 31, the phase front of the electromagnetic wave entering the radiating stub 312 is changed in the longitudinal direction of the radiating stub 312, thereby performing beam scanning in the H-plane in the longitudinal direction of the radiating stub 312.

In this invention, the phase front of the electromagnetic wave entering the radiating stub 312 is changed in the longitudinal direction of the radiating stub 312 by using the oblique incidence of the guided mode propagating to the feed array 31, so that the radiating stub 312 functions as a mechanism in which multiple element antennas are arranged in a row along the longitudinal direction of the radiating stub 312. The (hypothetical) element antennas considered to constitute the radiating stub 312 are called "virtual element antennas 312a."

Figure 4 (A) shows the relationship between the arrangement and directivity of the multiple virtual element antennas 312a when the radiation stub 312 is excited in phase, i.e., when each of the multiple virtual element antennas 312a considered to constitute the radiation stub 312 is excited in phase.

In this case, the longitudinal direction of the radiation stub 312 is aligned along a direction perpendicular to the electromagnetic wave propagation direction (i.e., the y-axis direction in the state of FIG. 1) (see FIG. 1(B)), and adjacent virtual element antennas 312a are excited in phase, in other words, it can be considered that adjacent virtual element antennas 312a are excited in such a way that the difference Δφ in the amount of phase shift between them is 0 (zero).

When the radiating stubs 312 are excited in phase, the wavefront of the electromagnetic wave is formed parallel to the arrangement of the multiple virtual element antennas 312a (i.e., the longitudinal direction of the radiating stubs 312, i.e., the y-axis direction in Figures 1 and 4(A)), and a main lobe is formed in a direction perpendicular to the arrangement of the multiple virtual element antennas 312a (i.e., the x-axis direction in Figures 1 and 4(A)).

Figure 4 (B) shows the relationship between the arrangement and directivity of the multiple virtual element antennas 312a when the radiation stub 312 is excited with a phase difference, that is, when each of the multiple virtual element antennas 312a considered to constitute the radiation stub 312 is excited with a phase difference.

In this case, the longitudinal direction of the radiation stub 312 is inclined relative to a direction perpendicular to the electromagnetic wave propagation direction (see FIG. 5), and adjacent virtual element antennas 312a are excited with a phase difference of Δφ (≠0). In other words, it can be considered that adjacent virtual element antennas 312a are excited while being controlled so that the difference Δφ in the amount of phase shift between them is constant at a certain value (but not 0).

When the radiation stub 312 is excited with a phase difference, the wavefront of the electromagnetic wave is tilted with respect to the arrangement of the multiple virtual element antennas 312a (i.e., the longitudinal direction of the radiation stub 312), and as a result, the direction of the main lobe rotates by Δθ with respect to the direction perpendicular to the arrangement of the multiple virtual element antennas 312a (i.e., the x-axis direction in Figures 1 and 4(B)). Note that if the mutual distance between the virtual element antennas 312a is d, then Δθ = d sin(Δφ).

By performing phase shift control that realizes the relationship between the arrangement and directivity of the multiple virtual element antennas 312a that are considered to constitute the radiating stub 312 as described above by controlling the rotation of the antenna unit 3 (specifically, the feed array 31), it is possible to scan the directivity within the H-plane in the longitudinal direction of the radiating stub 312.

For example, the second rotation unit is operated to rotate the antenna unit 3 relative to the plane wave generating unit 2, and the degree of rotation of the antenna unit 3 relative to the plane wave generating unit 2 is adjusted to set the altitude angle (EL) direction, and the first rotation unit is operated while the degree of rotation of the antenna unit 3 relative to the plane wave generating unit 2 is fixed, causing the plane wave generating unit 2 and the antenna unit 3 to rotate together, thereby performing beam scanning in the azimuth angle (AZ) direction.

According to the antenna device 1 of the embodiment, the plane wave generating unit 2 and the antenna unit 3 are rotated together to perform beam scanning in the azimuth direction, and the antenna unit 3 is rotated relative to the plane wave generating unit 2 to tilt the wavefront of the electromagnetic wave of the plane wave incident on the base 311 of the antenna unit 3 to perform beam scanning in the altitude direction. This makes it possible to scan the beam in all directions without the need for a phase shifter, and also makes it possible to reduce the cost of the antenna device.

In the antenna device 1 according to the embodiment, the probe is powered from the center of rotation of the plane wave generating unit 2 and the antenna unit 3, which further simplifies the configuration of the antenna device.

In addition, according to the antenna device 1 of the embodiment, the plane wave generating section 2 has a folded waveguide, which makes it possible to make the antenna device more compact.

Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there are design changes within the scope of the invention that do not deviate from the gist of the invention, they are included in the invention.

Specifically, in the above embodiment, the plane wave generated by the power supply unit is incident on the feed array 31 (specifically, the base 311) of the antenna unit 3, but the mechanism for generating the plane wave incident on the feed array 31 is not limited to the power supply unit in the above embodiment, and a plane wave generated by another plane wave generating mechanism may be incident on the feed array 31.

REFERENCE SIGNS LIST 1 Antenna device 2 Plane wave generating section 21 Lower waveguide 22 Upper waveguide 23 Folded section 24 Reflector 25 Conductor plate 26 Main reflector 27 Sub-reflector 28 Probe 29 Choke 3 Antenna section 31 Feed array 311 Base 312 Radiating stub 312a Virtual element antenna

Claims (2)

The antenna includes a plane wave generating unit, an antenna unit, a first rotating unit, and a second rotating unit,
The plane wave generating unit is
A probe that emits electromagnetic waves;
a main reflector and a sub-reflector forming a Cassegrain structure for converting the cylindrical electromagnetic wave radiated from the probe into a plane electromagnetic wave,
The antenna portion is
A plate-shaped base;
a plurality of radiating stubs formed in the base as a series of slots arranged in parallel and equally spaced apart relation to one another;
The first rotating unit rotates the plane wave generating unit and the antenna unit together around the probe as a rotation center, thereby performing beam scanning in an azimuth direction;
and rotating the antenna unit with respect to the plane wave generating unit around the probe as a rotation center by the second rotating unit to tilt a wavefront of the electromagnetic wave of the plane wave incident on the base of the antenna unit, thereby performing beam scanning in an altitude angle direction.
1. An antenna device comprising: the plane wave generating section has a folded waveguide including a lower layer waveguide and an upper layer waveguide which are laminated and each of which constitutes a parallel plate line,
The Cassegrain structure is disposed within the underlying waveguide;
The antenna unit is provided on the upper waveguide side.
2. The antenna device according to claim 1 .