Patent Application
20070008234
The invention relates generally to wireless communications, and more particularly to utilizing a light source or a simple reflector having a reflective surface and transparent cover to deliver a selected beam pattern for use as a directional antenna.
In the past, telecommunication services integrated in an automobile were limited to a few systems, mainly analog radio reception (AM/FM bands), for which a simple whip antenna was mounted to and extended from a vehicle body. A disadvantage of this fixed mast 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 of the signal frequency. This is because the whip antenna must exhibit certain mechanical characteristics to achieve user needs and meet required electrical performance. The antenna length, or the length of each element of an antenna array, depends on the received and transmitted signal frequencies. A further disadvantage of the monopole antenna is that it is susceptible to damage due to vandalism and car wash systems.
Further, the monopole antenna has a nearly omnidirectional radiation pattern, which provides a signal sent with approximately the same strength in all directions in a generally horizontal plane, producing a null only towards the sky. Another disadvantage of the monopole antenna is that it is typically narrowband with a bandwidth of roughly ten percent. With the rising number of communication systems, there are a continuously rising number of services that are to be integrated in the vehicle and which require further antennas to be arranged in the vehicle. Further, if antenna diversity is used to provide directional sensitivity, a number of antennas are required. However, since vehicle design is often dictated by styling, the presence of numerous protruding antennas is not desirable.
In an effort to minimize any aesthetically displeasing appearance or visually obstructive antenna characteristics, a trend emerged to embed the antenna system into the vehicle structure, such as, for example, into a rear window. Further, an integration of several telecommunication services into a single antenna is attractive to reduce manufacturing and installation costs of multiple antennas. However, rear window antennas exhibit troubles, for example, pattern disconnection of the thin window antenna often occur.
Not only are the electrical, mechanical and aesthetic properties of an antenna important, but an antenna must also overcome unique performance issues in the wireless environment. Further, antenna integration is becoming more necessary due to a cultural change towards an information society. The Internet has evoked an information age in which people around the globe expect, demand, and receive information. Car drivers expect to be able to drive safely while handling e-mail and telephone calls and obtaining directions, schedules, and other information accessible on the World Wide Web. Telematic devices can be used to automatically notify authorities of an accident and guide rescuers to the car, track stolen vehicles, provide navigation assistance to drivers, call emergency roadside assistance, and provide remote engine diagnostics. In designing the antenna, careful consideration must be given to the antenna electrical characteristics so that signals transmitted from and received by a communications device satisfies pre-determined operational limits, such as the bit error rate, signal-to-noise ratio or signal-to-noise-plus-interference ratio. In a number of applications, an omnidirectional antenna is less effective in achieving optimum values for these characteristics, as compared with a directional antenna.
The directional antenna, provides a concentrated signal or beam in a selected direction. Concentrating the beam increases the antenna gain and directivity. Directional antennas are often utilized to communicate with terrestrial support, with short range communication systems (SRC). Radio frequency (RF) communication signals are typically employed for their advantages of penetrating and passing through objects, their low power, and low cost.
However, directional antennas currently suffer from disadvantages of having complex shapes and large size, making them difficult to package in a vehicle. It is preferable to conceal the antenna to protect it from the environment and to preserve vehicle aesthetics. In order to conceal the antenna, it is usually necessary to locate the antenna beneath the sheet metal body of a vehicle. However, the sheet metal shields and adversely affects the performance of the directional antenna.
A novel directional antenna is described by U.S. patent application Ser. No. 11/987,786, entitled Directional Antenna, assigned to Delphi. In one description, the antenna includes an information signal impressed across a light filament of a vehicle headlight, and a reflective surface directs the electromagnetic radio waves in a predetermined direction. The antenna is fully concealed and can operate using an unmodified, factory installed vehicle headlight. However, the beam pattern is set in part by the physical characteristics and positioning of the filament and the reflective surface.
A directional antenna is provided that utilizes an existing light source having a beam directing reflective surface and a transparent cover for transmitting and receiving electromagnetic radio waves. Beam pattern, gain, polarization and wavelength can be selected for providing an effective resonant antenna. In view of the fact that lights having reflective surfaces are utilized in a wide variety of environments, it is to be appreciated that the present invention has numerous applications, including being employed with lights situated to a fixed structure such as to a building or post, as well as with lights attached to a mobile vehicle such as front headlights and rear lights. Simple reflectors without a light filament can additionally be utilized with the present invention.
In an embodiment, the directional antenna of the present invention reduces material costs, manufacturing costs and assembly costs, as compared to presently available antennas. The antenna system can be readily installed into a vehicle with minor additions or modifications, may be operated with minimal or no impact on the performance of an existing headlight, and can be fully concealed. Further, superior directivity of transmitting broadcasting signals is obtained at particular frequencies, as well as a reduction in power usage.
In an embodiment, the present invention can be used for vehicle-to-base or vehicle-to-vehicle communication systems. The present invention can be used for short range communication systems for a motor vehicle including electronic toll collection (ETC) systems. The present invention may further be useful for inter-roadway communication systems. The present invention can be used for long range communication systems. The present invention can further be useful for vehicle entry and exit monitoring systems, security and warning systems, adaptive cruise control, guidance applications, such as for controlling vehicles from drifting from their traffic lane. Additionally, the present invention may be used to detect objects, such as obstructions and other vehicles, distant from a vehicle in the forward direction. The present invention can be used for a forewarn ACC system or backup aid systems as well.
Features of the invention are achieved in part by making use of an existing reflective surface and transparent cover, such as in a vehicle headlight or simple reflector. In an embodiment, the radiating or receiving antenna element (a conductive material) is formed to the transparent cover of a vehicle headlight. Together, the conductive material and the light beam reflector direct an RF transmission toward an intended receiver, or receive an RF transmission from an intended receiver.
In an embodiment, a processor is connected to an AC source and an oscillator, the oscillator for generating a carrier frequency. A modulator thereafter superimposes the AC source onto the carrier frequency for transmission via a transmission link to the conductive material. A magnetic field is created about the conductive material, which radiates electromagnetic radio waves. The reflective surface directs the electromagnetic radio waves in a predetermined direction, maximizing antenna performance. In an embodiment, the conductive material is incorporated into a vehicle headlight. The antenna system may be incorporated with a fixed structure or with a mobile vehicle including a car, truck, airplane, ship, boat, etc.
Beam pattern, gain, polarization and wavelength can be selected through the design of the conductive material. The conductive material can be formed in an elected pattern, length and size, and can further be positioned a selected distance from the reflective surface. The distance that the conductive material is positioned with respect to the reflective surface can be selected by modifying the shape or depth of the transparent cover, since the conductive material is formed to the transparent cover.
In an embodiment the present invention generates an RF signal having a bandwidth at a frequency in the range of about 1 megahertz (MHz) to at least 100 gigahertz (GHz) for broadcasting to a receiver or for detecting objects. Experimental results have shown to date that the more useful transmitter frequencies, having acceptable gain and reaching a resonant frequency, are in the range of 80 MHz to 600 MHz for a standard motor vehicle headlight. It is to be appreciated that other standard motor vehicle headlights may vary in useful transmitter frequencies.
Other features and advantages of this invention will be apparent to a person of skill in the art who studies the invention disclosure. Therefore, the scope of the invention will be better understood by reference to an example of an embodiment, given with respect to the following figures.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Exemplary embodiments are described with reference to specific configurations. Those of ordinary skill in the art will appreciate that various changes and modifications can be made while remaining within the scope of the appended claims. Additionally, well-known elements, devices, components, methods, process steps and the like may not be set forth in detail in order to avoid obscuring the invention. Further, unless indicated to the contrary, the numerical values set forth in the following specification and claims are approximations that may vary depending upon the desired antenna characteristics sought to be obtained by the present invention.
A system and method is described herein for providing a directional antenna. An existing light source or simple reflector having a beam directing reflective surface and a transparent cover is utilized for transmitting and receiving electromagnetic radio waves. Beam pattern, gain, polarization and wavelength can be selected for providing an effective resonant antenna. It is to be appreciated that features of the discussion and claims can be utilized with a simple light or reflector, which can be situated to a fixed structure such as to a building or post, as well as with lights or reflectors attached to a mobile vehicle including a car, truck, bicycle, airplane, ship, and boat. The present invention may be used to detect an object or communicate with a receiver/transmitter. In an embodiment, the present invention is employed for communication services of a motor vehicle.
In an embodiment, the directional antenna provided by the present invention is readily installed into a vehicle with a minor addition or modification. Material costs, manufacturing costs and assembly costs are reduced as compared with existing antennas. Further, an important advantage of the present invention is that the antenna system provided can be utilized with an assortment of vehicles, lights and reflectors having distinct designs and manufacturers. Further, in an embodiment the present invention may be operated with little to no impact on the performance of the existing headlight, for example headlight luminosity or light beam direction. The present invention also eliminates mounting operations in production lines. The perforation of the car bodywork is also avoided, ensuring a solid and watertight fixture. In contrast, conventional whip antennas often perforate the car bodywork and are exposed to high air pressure. Additionally, the present invention cannot easily become disconnected (i.e., upon exterior vehicle cleaning). Moreover, the directional antenna provided is concealed and makes a virtually imperceptible visual impact on the car design. Also, a driver's visibility (field of view) is not obstructed by the antenna system provided.
Additionally, a reduction in power is realized since the antenna beam patterns extend outward in the direction of a receiver and are attenuated in other directions. Superior directivity of transmitting broadcasting signals is also obtained. Further, by directing transmissions toward a receiver, and directively receiving signals, the antenna system of the present invention reduces effects of multipath fading. Further, the present invention obviates the problem of radiation leakage into the interior of a vehicle. Moreover, aerodynamic properties, a concern in regard to vehicle fuel consumption and vehicle noise, are unaffected.
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
In an embodiment, the present invention applies an information signal to transmission cable 126 passing to transmission cable 128, which can be in the form of an alternating current (AC). Transmission cable 126 and transmission cable 128 can be a conventional coaxial cable. Other transmission lines can be utilized such as parallel-wire or waveguides for transmission of microwaves. As shown, transmission cable 126 can be attached to conventional power cable 124. Transmission cable 128 is formed to headlight 100 and connects to conductive material 130. Optionally, transmission cable 126 and transmission cable 128 are separate and connectable cables to allow simple replacement of headlight 100 for any reason (i.e., damaged headlight, worn filament, etc.). This way, an AC information signal generator, providing a signal to transmission cable 128 is unaffected by such a replacement.
Referring to
Conductive material can be formed to the inside of a transparent cover, the outside of a transparent cover or formed within the material of a transparent cover. By forming the conductive material to the inside of a transparent cover or within the material of a transparent cover, outside environmental concerns are avoided, such as weather and cleaning concerns. Alternatively, the conductive material can be applied to the outside of a transparent cover to avoid dismantling a headlight. Further, the conductive material can be formed to a transparent cover by an adhesive including tape, or alternatively by painting the conductive material to the transparent material. The paint can act as a binder and adhesive. In an embodiment, the conductive material is formed to a transparent cover in thin strips with a minimized amount of conductive material to minimize any reduction of the light caused by the conductive material and emitted from the filament through the transparent cover. Various materials can be utilized as conductive material 432, including copper, silver, gold, aluminum, indium tin oxide, or a blend of metals. Further, conductive material 432 can be formed of a transparent material, i.e., indium tin oxide, to enhance aesthetics and maintain full performance of an existing light.
As illustrated in
In a further embodiment, a phased array pattern is employed utilizing at least two vehicle headlights. It is to be appreciated that vehicle headlights are spaced with maximized distance, making the headlights a useful component for spacing needs of a phased array antenna system. In a phased array operation, the current magnitude and phase of each vehicle headlight is adjusted to reinforce the radiation pattern in a desired direction and suppress the radiation pattern in undesired directions. Vehicle headlights 502A and 502B, being spaced apart on a vehicle, maximize the distance between radiating antennas, in a phased array embodiment of the present invention. Hence, the relation between the direction and intensity of RF beam radiation of the antennas (directivity) can be improved by utilizing two vehicle headlights or a dual element antenna. Further, in regard to directional pattern or directivity, by utilizing two headlights set apart, the widths of the RF beams can be narrowed, and the directional resolution can be improved. In an embodiment, beamwidths are varied, for example to create a null to minimize interference between signal transmission and signal reception.
It is to be appreciated that modifications can be made to the physical attributes of reflective surface 420, to transparent cover 412 and to conductive material 430 to change the directive beam pattern from the antenna array. By conductive material design freedom, the antenna length and distance from a reflective surface, and therefore gain, matching and wavelength can be adjusted. Also, improved beam pattern can be obtained. Variable beamwidth and beam steering is possible across the frequency range. The required resonance is selected to give the preferred reflection from the transparent cover and from the reflective surface.
Modifications can include changing the conductive material 430 size, length or shape, changing conductive material 430 spatial positioning in relation to reflective surface 420, and changing the curvature or shape of reflective surface 420. In the case wherein the length of conductive material 430 is decreased, the resonant frequency of the system is increased, since conductive material 430 length is inversely proportional to system resonant frequency. Causing an increase in resonant frequency may prove useful in certain broadcasting applications. Additionally, reflective surface 420 can be formed in the shape of a parabola and direct electromagnetic waves as a parabolic antenna. Other shapes can also be used for reflective surface 420 including a hyperboloidal surface, ellipsoidal surface, etc.
In an embodiment, the transparent cover 412 is modified from a standard manufactured version, wherein the modification includes one of a modified transparent cover shape and a modified transparent cover spatial positioning relative to the reflective surface 420. In another embodiment, a secondary transparent extension cover or extension is formed over the standard transparent cover 412. The conductive material 430 is formed on the secondary transparent extension cover. Further, it is to be appreciated that the conductive material 430 may be formed to both a standard transparent cover 412 and to an attachment transparent cover. This way, the processor can manage a transmission to an alternative conductive material to optionally vary the reflective properties of the signal. This addition can be utilized for raising the vertical pitch of a directional beam. This is useful to accommodate for signal interference due to an obstruction, or to accommodate for changes in orientation of the transmitter vehicle 500 relative to a receiver.
The system described follows established resonant frequency principles. In an embodiment, the transmitter is a variable frequency AC source. The variable frequency AC is applied to a series circuit containing some value of inductance and capacitance, which pose some value of reactance. As the frequency of the variable AC source is adjusted throughout its entire range, a specific frequency is reached causing the inductive reactance to equal the capacitive reactance. At this point in the frequency spectrum, the circuit current is the highest, capacitive reactance is equal to the inductive reactance, and resonant frequency is reached. As well known in the art, fr=1/(2π√{square root over ( )}(LC)), where fr is the resonant frequency, L is the inductance value and C is the capacitance value.
The range of the system transmission is dependant on the resonance selected and the selected power, which can be managed by the processor for the particular purpose of the transmission. In an embodiment, a transmission link is provided between a control means (not shown) and headlight antenna 200 (
Referring to
A further understanding of the above description can be obtained by reference to the following experimental result examples that are provided for illustrative purposes and are not intended to be limiting. While the experimental results of
In an embodiment, signal generator 204 (
Other features and advantages of this invention will be apparent to a person of skill in the art who studies this disclosure. For example, it is to be appreciated that the conductive material formed to the transparent cover as discussed herein can both transmit and receive signals through atmospheric free space. Thus, exemplary embodiments, modifications and variations may be made to the disclosed embodiments while remaining within the spirit and scope of the invention as defined by the appended claims.
