Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
2001-07-13
2002-08-27
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S909000
Reexamination Certificate
active
06441792
ABSTRACT:
TECHNICAL FIELD
The present invention relates to broadband antennas for vehicular communication. More specifically, the present invention relates to a broadband multi antenna module and a method of integrating this module into the exterior of a vehicle. The module contains multiple antennas operating in multiple frequency bands, which antennas, when excited appropriately, produce multiple beams and/or receive wireless signals in multiple bands for various wireless services. The present invention allows a single unit to be installed in the vehicle in one operation, which unit can contain all of the antennas necessary for the communication needs of an occupant of the vehicle.
Furthermore, the disclosed antenna module is thin enough to fit between a metallic ground plane that may be part of the vehicle frame. A second surface consisting of dielectric that acts as a radome may also form a part of the module. The module itself preferably combines a ground plane, a feed network, several antennas covering multiple bands and producing multiple beams and preferably also employs techniques for isolating these antennas from their neighbors. This invention reduces or eliminates antenna radiation from entering the interior of the vehicle, while maintaining a thin form factor. Other methods exist for creating low-profile, broadband antennas; however, many of them require removal of a portion of the metallic exterior of the vehicle, thus allowing antenna radiation into the vehicle interior.
BACKGROUND OF THE INVENTION
As demand for existing wireless services grows and new services continue to emerge, there will be an increasing need for antennas on vehicles. Existing antenna technology usually involves monopole or whip antennas that protrude from the surface of the vehicle. These antennas are typically narrow band. Thus, to address a wide variety of communication systems, it is necessary to have numerous such antennas positioned at various locations on the vehicle. Furthermore, as data rates continue to increase, especially with 3G, Bluetooth, direct satellite radio broadcast, and wireless Internet services, the need for antenna diversity will increase. This means that each individual vehicle will require multiple antennas each operating in different frequency bands, and/or with different polarizations and/or at different elevations relative to the horizon. Since vehicle design is often dictated by styling, the presence of numerous protruding antennas will not be easily tolerated. Furthermore, the installation of multiple antennas is costly.
The most basic prior art antenna is the simple whip monopole that is used for FM radio reception and cellular phones. The antenna has a nearly omnidirectional radiation pattern, producing a null only towards the sky. The primary disadvantage of the monopole antenna is that it protrudes from the exterior of the vehicle as an unsightly vertical wire with a height of roughly one quarter wavelength. The monopole is also typically narrowband with a bandwidth of roughly 10%. In order to access multiple wireless services operating on multiple frequencies, multiple monopole antenna would thus be required. Furthermore, if antenna diversity is used to provide directional sensitivity, the number of required antennas is even greater. A logical alternative might be to use a single broadband antenna that could cover all frequency bands of interest. Examples of broadband antennas include spiral antennas, flared notch antennas and log periodic antennas. However, with all of these types of antennas and with broadband antennas in general, the presence of the metallic ground plane is not tolerated. However, if a part of the metal vehicle body is removed and replaced with a dielectric, such a broadband antenna could be integrated into this dielectric and would function over a broad bandwidth. This concept is shown in
FIG. 1. A
significant drawback of this approach is that it allows the interior of the vehicle to receive just as much antenna radiation as the exterior. With increasing questions over the effects of electromagnetic radiation, this design may be undesirable.
Antennas exist which can function well in the presence of the metallic ground plane, such as patch antennas and various types of traveling wave antennas. These antenna all tend to excite surface currents in a surrounding ground plane. Such surface currents can tend to cause interaction between the individual antennas and can also cause radiation to occur at discontinuities or at edges of the ground plane. This problem is shown in FIG.
2
.
Thin antennas exist, such as patch antennas; however, they typically exhibit a narrow bandwidth and do not provide flexibility in the shape of the radiation pattern and/or their sensitivity pattern. Conversely, broadband antennas exist, but they generally are not thin and/or they cannot tolerate the presence of a nearby metal ground plane. One possible solution is to eliminate the metallic ground plane by removing a portion of the vehicle frame or body and replacing it with a sheet of dielectric. A thin broadband antenna can then be mounted on the dielectric sheet to provide access to many wireless services. The problem with this solution is that the elimination of the ground plane allows radiation inside the vehicle interior. Furthermore, with many services sharing the same antenna, interference between devices within the vehicle is increased.
The prior art includes the following:
1) D. Sievenpiper and E. Yablonovitch, “Circuit and Method for Eliminating Surface Currents on Metals” U. S. provisional patent application, Ser. No. 60/079,953, filed on Mar. 30, 1998 by UCLA and corresponding PCT application PCT/US99/06884, published as WO99/50929 on Oct. 7, 1999, the disclosures of which are hereby incorporated herein by reference.These applications disclose a Hi-Z surface.
2) U.S. Pat. No. 4,821,040 entitled “Circular Microstrip Vehicular RF Antenna”, assigned to Ball Corporation of Muncie, Ind. This patent describes an antenna consisting of a circular slot radiator that may be mounted within the roof of a vehicle.
3) U.S. Pat. No. 6,091,367 entitled “Light-weight Flat Antenna Device Tolerant of Temperature Variation”, by Kabashima, Shigenori; Ozaki, Tsuyoshi; Takahashi, Toru; Konishi, Yoshihiko; and Ohtsuka, Masataka. This patent describes an array of multiple conventional patch antennas.
4) U.S. Pat. No. 6,037,912 entitled “Low Profile Bi-Directional Antenna”, by DeMarre, Allen G. This patent describes a low-profile antenna system for mounting on the exterior of a vehicle.
5) U.S. Pat. No. 5,850,198 entitled “Flat Antenna with Low Overall Height”, by Lindenmeier, Heinz; Hopf, Jochen; and Reiter, Leopold. This patent describes an antenna for accessing multiple frequency bands for multiple RF services by providing multiple resonant regions that act as separate antennas.
6) U.S. Pat. No. 5,818,394 entitled “Flat antenna”, by Aminzadeh, Mehran; Burkert, Manfred; Daginnus, Michael; and Chen, Shun-Ping. This patent describes an antenna mounted below the windshield of a vehicle, resulting in a low-profile design which is hidden from view.
7) U.S. Pat. No. 5,682,168 entitled “Hidden Vehicle Antennas”, by James, Jesse C.; and Blackmon, Jr., James B. This patent describes a way of mounting antennas in motor vehicles.
8) U.S. Pat. No. 5,177,493 entitled “Antenna Device For Movable Body”, by Kawamura, Katsuaki. This patent describes a method of mounting an antenna on a vehicle.
9) U.S. Pat. No. 4,760,402 entitled “Antenna System Incorporated in the Air Spoiler of an Automobile”, by Mizuno, Hiroshi; Sakurai, Takashi ; and Shibata, Yoshihisa. This patent describes a way of hiding an antenna in the air spoiler of a vehicle.
Still there is a need for a single antenna unit that combines antennas for various services, and can be installed in a vehicle simply, preferably in one operation. This antenna unit should be thin and should contain a ground plane that can be integrated with or made to cooperate with the metal exterior of the vehicle so as to avoid vehicle interior radiation. Furth
Hsu Hui-Pin
Schaffner James H.
Sievenpiper Daniel F.
Tangonan Gregory L.
HRL Laboratories, LLC.
Ladas & Parry
Nguyen Hoang
Wong Don
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