Patent Application
20060104642
The invention relates generally to wireless communications, and more particularly to a combined transmitter and receiver incorporating a light source having a beam directing reflective surface 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 it must also overcome unique performance problems 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, another form of 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 their 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 directional antenna is provided that utilizes an existing light having a beam directing reflective surface for transmitting electromagnetic radio waves. 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.
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, may be operated without an impact on the performance of an existing headlight, and is 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 light as the radiating antenna element. Together, the light filament and the light beam reflector direct the RF transmission toward an intended receiver. In an embodiment, the directional antenna system includes an alternating current (AC) source, and an illuminator having a reflective surface for directing a beam of light. The AC source provides AC via a transmission link to the illuminator for creating a magnetic field about the illuminator and radiating electromagnetic radio waves. The reflective surface directs the electromagnetic radio waves in a predetermined direction, maximizing antenna performance. In an embodiment, the illuminator is a filament incorporated into a vehicle headlight wherein a direct current (DC) source supplies current to the filament. The antenna system may be incorporated with a fixed structure or with a mobile vehicle including a car, truck, airplane, ship, boat, etc.
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 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 by transmitting an information signal to a light source having a beam directing reflective surface. It is to be appreciated that features of the discussion and claims may be utilized with a simple light, which may be situated to a fixed structure such as to a building or post, as well as with lights 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. 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 and lights having distinct designs and manufacturers. Modification to an existing headlight is unnecessary for an extensive number of communication uses. Further, in an embodiment the present invention may be operated without any impact on the performance of the existing headlight, for example headlight luminosity or beam direction. The present invention also makes possible the elimination of mounting operations in production lines, such as the perforation of the car bodywork, together with the suppression of additional mechanical pieces that ensure a solid and watertight fixture of conventional whip antennas which 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 fully concealed and makes an 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 the receiver and are attenuated in other directions. Superior directivity of transmitting broadcasting signals is also obtained. Further, by directing transmissions toward the 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, 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 124, which is in the form of an alternating current (AC). Thus, transmission cable 124 provides both a DC power interface and an RF interface. The AC information signal flows to filament 112 with the usual DC power. A magnetic field is then produced around at least a portion of filament 112, which radiates energy in the form of electromagnetic waves to produce a wireless transmission. As discussed below, reflective surface 110 directs the electromagnetic waves in the direction that light beams are directed from reflective surface 110, without affecting the intensity or direction of any light beams generated from headlight 100. Reflective surface 110 can be in the shape of a parabola and direct electromagnetic waves as a parabolic antenna. Other shapes can also be used for reflective surface 110 including a hyperboloidal surface, ellipsoidal surface, etc.
In an embodiment of the present invention, a standard vehicle headlight acting as the radiating antenna element can be readily replaced for any reason (i.e., damaged headlight, worn filament, etc.) and the invention will fully operate. For example, headlight 100 can be disconnected from female power connector 120 and a replacement headlight reconnected to female power connector 120. An AC information signal generator is unaffected by such a replacement.
Referring to
It is to be appreciated that modifications can be made to the physical attributes of reflective surface 420 or to filament 422 to change the directive beam pattern from the antenna array. For example, modifications can include adding an additional filament, changing the filament 422 size, length or shape, changing filament 422 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 filament 422 is decreased, the resonant frequency of the system is increased, since filament 422 length is inversely proportional to system resonant frequency. Causing an increase in resonant frequency may prove useful in certain broadcasting applications.
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 232 (
As illustrated in
Factory installed vehicle headlights often employ two separate filaments, one for a high intensity beam 510 and one for a low intensity beam 512. As illustrated in
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.
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. As illustrated in
In an embodiment, signal generator 204 (
Referring to
In an embodiment of the present invention, employing an unmodified vehicle headlight, experimental beamwidth amplitudes were recorded. The recorded example RF beamwidth amplitudes measured at 0 degrees, 30 degrees, 60 degrees and 90 degrees, having frequencies of 200 MHz, 1 GHz, 2 GHz, 4 GHz and 6 GHz are shown below in Table 1 below.
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 an embodiment of the present invention, separated vehicle headlights are employed as an antenna element and a phased array is electronically scanned or steered to a desired direction by controlling the phase angle of the signal input to each antenna element. Further, in an embodiment, increasing the separation of the two headlight antenna elements narrows the beamwidth. Moreover, in an embodiment, beamwidths are varied, for example to create a null to minimize interference between signal transmission and signal reception.
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 antenna system as discussed herein may 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.
