Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Reexamination Certificate
1999-06-29
2001-02-27
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
C343S755000
Reexamination Certificate
active
06195058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric lens, a dielectric lens antenna including the same, and a wireless device including the same. More specifically, the present invention relates to a dielectric lens applied for a motor-vehicle-mounted radar which uses millimeter-waves, a dielectric lens antenna including the same, and a wireless device including the same.
2. Description of the Related Art
With the recent advance of motor-vehicle-mounted radar, control of the directivity of an antenna has been a significant concern.
FIGS. 11A
,
11
B and
11
C show a prior art dielectric lens.
FIG. 11A
is a plan view,
FIG. 11B
is a front view, and
FIG. 11C
is a side view. In a dielectric lens
1
, a lens
2
is substantially in a shape formed by cutting a part of a sphere. In the plan view, it is formed rotation-symmetrically, namely, in a round form, and in the front view and the side view, it is formed in a circular form. The lens
2
is made of dielectric materials such as ceramics, resin, plastic, or their composite materials. The focal direction of the dielectric lens
1
is the -z-axis direction.
FIGS. 12A
,
12
B and
12
C show a dielectric lens antenna including the dielectric lens
1
shown in
FIG. 11A
,
11
B and
11
C.
FIG. 12A
is a plan view;
FIG. 12B
is a front view; and
FIG. 12C
is a side view. In
FIG. 12
, the dielectric lens antenna
5
is formed by disposing a primary radiator
7
at the focal point
6
of the dielectric lens
1
.
FIG. 13
shows a conceptual view (a front view) illustrating the directivity of a beam radiated from the dielectric lens
1
of the dielectric lens antenna
5
shown in
FIGS. 12A
,
12
B and
12
C. In
FIG. 13
, the same reference numerals are given to the same parts as those in
FIG. 12
or the equivalent parts to those in
FIG. 12
; their descriptions are omitted. As shown in
FIG. 13
, the shape of beam
3
radiated from the dielectric lens
1
of the dielectric lens antenna
5
is a pencil-beam shape on the x-z side. In this case, the length (the height in
FIG. 13
) of z-axis direction of the beam
3
indicates the magnitude of a gain of the dielectric lens antenna
5
, and the width of the beam
3
indicates the magnitude of the beam width of the dielectric lens antenna
5
.
As seen above, the gain of the dielectric lens antenna
5
amounts to a maximum value in the z-axis direction. With respect to the z-axis direction, the angle in which a gain decreases by 3 dB from the maximum value, namely, the angle in which the gain amounts to a half is referred to a half-value angle, which indicates the directivity of the antenna. The shape of the beam
3
radiated from the dielectric lens
1
of the dielectric lens antenna
5
is the same on all the sides which include the z-axis and parallel to the z-axis, such as the x-y side, so that the line connecting points of the half-value angles forms a round form when viewed from the front of the dielectric lens antenna
5
. In addition, the half-value angle is substantially indicated by a formula:
A half-value angle (&thgr;)=70&lgr;/D
(&lgr;: wavelength of the used frequency,
D: antenna-aperture diameter)
Thus, a half-value angle is inversely proportional to an antenna aperture diameter. In contrast, the wider the aperture diameter, the larger the gain.
A motor-vehicle-mounted radar does not necessarily require the information of a vertical direction (up-and-down directions) with respect to a traveling direction of a motor vehicle. On the contrary, in order to prevent malfunctions due to reactions with a pedestrian overpass or a viaduct, it may be better for the radar to have less information of a vertical direction. Meanwhile, the information of a horizontal direction (a traveling direction and right-and-left directions of a motor vehicle) is primarily necessary, since other motor vehicles and obstacles are targeted. This can require a wide-angle antenna, in which a beam is narrowed in the vertical direction, whereas it is widened in the horizontal direction. In this case, in order to widen the beam, namely, to widen the half-value angle, it is necessary to make the antenna-aperture diameter smaller, namely, it is necessary to reduce the diameter of the dielectric lens. However, reducing the diameter of the dielectric lens leads to decrease in gain, thereby it creates a problem in which the lens can only detect at close range when it is used in radar. In addition, reducing the diameter of the dielectric lens leads to extension of the beam not only in the horizontal direction but also in the vertical direction; it thereby leads to further decrease in the gain in the horizontal direction.
SUMMARY OF THE INVENTION
To overcome the above problems, preferred embodiments of the present invention provide a dielectric lens capable of widening a half-value angle in a specified direction without decreasing a gain significantly, a dielectric lens antenna including the same, and a wireless device including the same.
One preferred embodiment of the present invention provides a dielectric lens and a dielectric lens antenna including the dielectric lens, wherein the dielectric lens is rotation-symmetrically shaped, and a flat end is disposed at a part of the edge the dielectric lens. In the dielectric lens antenna, a primary radiator is disposed at the focal point of the dielectric lens.
By the above described structure and arrangement, it become possible to widen a half-value angle in the direction in which the flat ends of the lens are disposed without reducing a gain significantly.
Preferably, in the above described dielectric lens, a first flat end and a second flat end are respectively disposed at a part of the edge the dielectric lens and opposed to each other. This structure and arrangement allows the half-value angles of the dielectric lens and the dielectric lens antenna to be smaller in the vertical direction (horizontal direction) and to be greater in the horizontal direction (vertical direction).
In the above described dielectric lens antenna, the primary radiator and the dielectric lens may be connected by a supporting plate extending in a taper shape from the outer periphery of the primary radiator to the edge of the dielectric lens over the entire circumference; and at least inner surface of the supporting plate may be made of metal.
By the above described structure and arrangement, spillover losses can be reduced to thereby high efficiency is achieved.
Another preferred embodiment of the present invention provides a wireless device comprising the above described dielectric lens antenna.
Use of the dielectric lens antenna of the present invention can control extension of a beam to reduce malfunctions of a wireless device.
Other features and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention which refers to the accompanying drawings, wherein like reference numerals indicate like elements to avoid duplicative description.
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patent: 4825221 (1989-04-01), Suzuki et al.
patent: 5892487 (1999-04-01), Fujimoto
patent: 5900847 (1999-05-01), Ishikawa et al.
patent: 6034642 (2000-03-01), Kojima et al.
patent: 6052087 (2000-04-01), Ishikawa et al.
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Nakamura Fuminori
Tanaka Hiroaki
Yamada Hideaki
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Tran Chuc D
Wong Don
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