Title: Apparatus for shaping the radiation pattern of a planar antenna near-field radar system
Abstract: A near-field radar apparatus includes a fixed beam planar radar antenna and a radiation pattern adaptation device disposed substantially at the near-field boundary of the antenna. The adaptation device comprises a plurality of dielectric elements that individually constitute or approximate different surface portions of an idealized quasi-spherical or quasi-cylindrical radome reflector. The dielectric elements can be maintained physically separate or combined about the diffraction point of the antenna to form a single dielectric element. The dielectric elements may be mounted on a radome that is otherwise transparent to the radiation pattern, or otherwise suspended at or near the near-field boundary of the antenna.
Patent Number: 6,897,819 Issued on 05/24/2005 to Henderson, et al.
| Inventors:
|
Henderson; Mark F. (Kokomo, IN);
Taylor; Ronald M. (Greentown, IN)
|
| Assignee:
|
Delphi Technologies, Inc. (Troy, MI)
|
| Appl. No.:
|
670431 |
| Filed:
|
September 23, 2003 |
| Current U.S. Class: |
343/713; 342/70; 343/700MS |
| Intern'l Class: |
H01Q 001/32 |
| Field of Search: |
343/713,872,700. MS,711,712
342/70,71,72
|
References Cited [Referenced By]
U.S. Patent Documents
| 3133284 | May., 1964 | Privett et al.
| |
| 3775769 | Nov., 1973 | Heeren et al.
| |
| 3852762 | Dec., 1974 | Henf et al.
| |
| 3935577 | Jan., 1976 | Hansen.
| |
| 3979755 | Sep., 1976 | Sandoz et al.
| |
| 4148040 | Apr., 1979 | Lunden et al.
| |
| 4318103 | Mar., 1982 | Roettele et al.
| |
| 4977407 | Dec., 1990 | Crane.
| |
| 5248977 | Sep., 1993 | Lee et al.
| |
| 5260710 | Nov., 1993 | Omamyuda et al.
| |
| 5530651 | Jun., 1996 | Uemura et al.
| |
| 5905457 | May., 1999 | Rashid.
| |
| 6072437 | Jun., 2000 | Zimmerman et al.
| |
| 6674412 | Jan., 2004 | Schmidt et al.
| |
Primary Examiner: Le; Hoanganh
Attorney, Agent or Firm: Chmielewski; Stefan V.
Claims
1. A near-field radar obstacle detection apparatus comprising:
a fixed beam planar radar antenna; and
an adaptation device for shaping a transmitted or received radiation of said
antenna, including a plurality of dielectric elements that individually constitute
different surface portions of an imaginary idealized quasi-spherical or quasi-cylindrical
reflector disposed substantially at a near-field boundary of said antenna.
2. The apparatus of claim 1, wherein said dielectric elements are supported by
a radome that is otherwise transparent to the transmitted or received radiation.
3. The apparatus of claim 2, wherein said dielectric elements are insert-molded
into said radome.
4. The apparatus of claim 1, wherein two or more of said dielectric elements
are combined about a diffraction point of said antenna to form a single multi-faceted
dielectric element disposed substantially at said near-field boundary.
5. The apparatus of claim 1, wherein said idealized reflector is quasi-cylindrical,
and said dielectric elements are defined by different surface portions of a post
disposed substantially at said near-field boundary.
6. The apparatus of claim 1, wherein said adaptation device compensates for off-axis
or off-center orientation of said antenna.
7. The apparatus of claim 1, wherein said adaptation device extends a field-of-view
of said antenna.
8. The apparatus of claim 1, wherein a radar antenna is mounted on a bumper of
said vehicle, and said adaptation device is supported on a fascia that surrounds
said bumper.
Description
TECHNICAL FIELD
The present invention is directed to near-field radar obstacle detection for
vehicles, and more particularly to apparatus for shaping the radar radiation pattern
of a planar radar antenna.
BACKGROUND OF THE INVENTION
Short-range obstacle detection for vehicle back-up and parking aid functions
can be achieved with a wide-angle radar system, but cost and packaging considerations
force design constraints that tend to limit the system performance. For example,
cost considerations effectively rule out the use of multiple transceivers for meeting
wide zone-of-coverage requirements, and both packaging and cost considerations
effectively require the use of planar transmit and receive antennas, which in general
are not well-suited to wide zone-of-coverage applications. Additionally, vehicle
styling and design considerations frequently require the radar system to be mounted
in a sub-optimal location (such as in the vehicle bumper) concealed behind vehicle
trim panels that alter the radar radiation pattern.
A common approach for achieving the required zone-of-coverage in vehicle applications
is to narrow the antenna radiation pattern and to radiate the specified zone-of-coverage
by scanning. Another approach is to utilize custom-fabricated horns or non-planar
antenna elements to broaden the radar field-of-view. However, such approaches are
usually ruled out due to cost and packaging considerations. Accordingly, what is
needed is an apparatus for shaping and broadening a planar antenna radar system
field-of-view that is low cost and that does not significantly increase package size.
SUMMARY OF THE INVENTION
The present invention is directed to an improved near-field radar apparatus including
a fixed beam planar radar antenna and a radiation pattern adaptation device disposed
substantially at the near-field boundary of the antenna. The adaptation device
comprises a plurality of dielectric elements that individually constitute or approximate
different surface portions of an idealized-imaginary quasi-spherical or quasi-cylindrical
radome reflector. The dielectric elements can be maintained physically separate
or combined about the diffraction point of the antenna elements to form a single
dielectric element. The dielectric elements may be mounted on a radome that is
otherwise transparent to the radiation pattern, or otherwise suspended at or near
the near-field boundary of the antenna. The dielectric elements may be simple and
inexpensive to manufacture, and do not significantly impact the package size of
the radar apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of example, with reference
to the accompanying drawings, in which:
FIG. 1A is a cross-sectional side-view diagram of a vehicle bumper-mounted radar
system including a radiation pattern adaptation device according to this invention.
FIG. 1B is a cross-sectional overhead view of the vehicle bumper-mounted system
of FIG. 1A.
FIG. 2 is a graph depicting radiation patterns for the radar system of FIGS.
1A-1B, with and without the radiation pattern adaptation device.
FIG. 3 depicts a planar antenna circuit board of the radar system of FIG. 1,
along with idealized cylindrical reflectors.
FIG. 4 depicts a first embodiment of the radiation pattern adaptation device
of FIGS. 1A-1B.
FIG. 5 depicts a second embodiment of the radiation pattern adaptation device
of FIGS. 1A-1B.
FIG. 6A depicts a mechanization of the radiation pattern adaptation device of
FIG. 5 with the radar system of FIGS. 1A-1B.
FIG. 6B details the radiation pattern adaptation device of FIG. 6A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The radar system of the present invention applies in general to the use of a
fixed beam radar sensor in applications requiring a wide-angle zone-of-coverage.
The invention is illustrated herein in the context of a vehicle back-up and parking
aid, but is applicable to other vehicle systems such as frontal or side object
detection systems, and also to non-vehicle systems.
FIGS. 1A-1B depict a bumper-mounted back-up aid mechanization where a fixed
beam radar sensor
10 is concealed behind a plastic fascia
12 surrounding
the bumper frame
14. The adaptation device of the present invention is designated
by the reference numeral
16, and is disposed in front of the radar sensor
10. While FIGS. 1A-1B show the adaptation device
16 as being supported
on the radar sensor
10, it should be understood that the adaptation device
16 may be supported independent of the radar sensor
10—for
example, by the bumper frame
14 or the plastic fascia
12. In the
illustrated back-up aid application, the adaptation device
16 functions
to extend the azimuth angle field-of-view as graphically depicted in FIG. 2, where
the dashed traces designate a normal radiation pattern (i.e., without the adaptation
device
16) and the solid traces designate an expanded radiation pattern
achieved with the adaptation device
16. In other applications, the adaptation
device
16 may be used to extend the elevation angle field-of-view, or both
azimuth angle and elevation angle fields-of-view. In general, extending the radiation
field-of-view in this manner allows the use of an inexpensive fixed beam radar
sensor
10 in wide-angle zone-of-coverage applications. Additionally, the
adaptation device
16 compensates for anomalies due to the mounting location
of the radar sensor
10 and the pattern-altering characteristics of the fascia
12. For example, the bore-sight of radar sensor
10 may be displaced
from and not parallel with the longitudinal axis of the vehicle, the fascia
12
may be angled vertically or horizontally with respect to the bore-sight, and so on.
In a conventional fixed-beam radar system, the field-of-view can be extended
using
a quasi-cylindrical or quasi-spherical reflector at or near the near-field boundary
of the radar antenna. In general, the near-field boundary is given by (2*D/λ),
where D is the aperture diameter of the antenna (i.e., the planar length of the
antenna's active elements in the direction of interest) and λ is the radar
wavelength. The region between the near-field boundary and the antenna is referred
to as the near-field region, and typically comprises an area within about two wavelengths
of the antenna. A reflector at or near the near-field boundary has the effect of
a slightly defocused lens, and the radar beams (transmitted and received) are refracted
as they pass through the reflector, effectively extending the field-of-view. A
typical application requiring an extended azimuth zone-of-coverage is depicted
in FIG. 3, where the reference numeral
20 designates a radar sensor circuit
board on which are formed two planar patch antennae: a transmit antenna
22
comprising the patch elements
22a, and a receive antenna
24
comprising the patch elements
24a. The transmit and receive reflector
28 and
26 are located at or near the near-field boundaries of the
transmit and receive antennae
22 and
24, respectively, and each reflector
26,
28 is cylindrical or quasi-cylindrical. In certain situations,
transmit and receive antennae
22,
24 may be combined, in which case
only a single reflector is required. In applications requiring an extended elevation
zone-of-coverage, the reflectors
26,
28 can be rotated by 90°,
while in applications requiring extended azimuth and elevation zones-of-coverage,
the reflectors can be spherical (or quasi-spherical) instead of cylindrical.
As indicated above, traditional cylindrical or spherical reflector elements (such
as the reflectors
26 and
28 depicted in FIG. 3) are expensive to
manufacture, and difficult to package in an environment such as depicted in FIG.
1. The present invention overcomes this problem through the recognition
that the benefits achieved with traditional cylindrical or spherical reflectors
can be achieved at a much lower cost with an adaptation device comprising a plurality
of dielectric elements that individually constitute or approximate different surface
portions of an idealized quasi-spherical or quasi-cylindrical reflector. This approach
is illustrated in FIG. 3 by the dielectric elements
26a and
26b
which constitute different surface portions of the reflector
26, and
the dielectric elements
28a and
28b which constitute
different surface portions of the reflector
28. In a preferred implementation,
the elements
26a,
26b,
28a,
28b
each represent only a small portion of the respective idealized reflectors
26,
28 so that they may be easily integrated into a radome that is
otherwise transparent to the emitted and received radiation, and may be approximated
as planar (i.e., non-curved) elements with negligible optical degradation. FIG.
4 depicts such an embodiment, where eight dielectric elements
30a,
30b,
30c,
30d,
30e,
30f,
30g,
30h are supported on a radome
30 that is
otherwise transparent to the emitted and received radiation. Of course, the elements
30a-
30h may be different in number and area than shown,
and may be incorporated into radome
30 by an insert molding process if desired.
Additionally, different dielectric elements such as the elements
32a
and
32b can be combined within the diffraction or near-field
region of an antenna
34 as illustrated in FIG. 5 to form a single multi-faceted
dielectric element
36. As indicated in FIG. 5, the orientation of the individual
dielectric elements
32a,
32b is maintained, and the
combined element
36 remains at or near the near-field boundary of the antenna
34. In the case of a cylindrical reflector, it may be desirable to form
each combined dielectric element as a post
38,
40 physically suspended
in front of the radar sensor
10, as shown in FIG.
6A. The post
38
is detailed in FIG. 6B, where the surface
38a corresponds to the
element
32a of FIG. 5, and the surface
38b corresponds
to the element
32b of FIG.
5.
In summary, the present invention provides a simple and inexpensive adaptation
device that enables a fixed beam planar antenna radar sensor to achieve an extended
field-of-view for applications requiring a wide-angle zone-of-coverage, while also
compensating for anomalies due to mounting variations (skewed, off-axis or de-centered
patterns, for example), for pattern displacement due to physical separation of
the transmit and receive antennas, and dielectric films such as the vehicle bumper
fascia
12. While the invention has been described in reference to the illustrated
embodiment, it should be understood that various modifications will occur to persons
skilled in the art, and radar systems including such modifications may fall within
the scope of this invention, which is defined by the appended claims.
*
