Telecommunications – Wireless distribution system
Reexamination Certificate
2002-05-30
2003-07-29
Le, Thanh Cong (Department: 2684)
Telecommunications
Wireless distribution system
C455S099000, C455S575100
Reexamination Certificate
active
06600896
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to communications, and more particularly to systems for communications internally and in close proximity to vehicles having metallic structures. The invention is particularly useful at radio frequencies in the range of 0.1 to 100 MHz, with some variants of the invention able to operate at ranges above 500 MHz.
BACKGROUND ART
It is desirable to communicate information between various locations within and around vehicles, including but not limited to cars, trucks and tractor-trailers, trains, ships and planes. Traditionally, this has been obtained by installing conductive wires between points. More recently, optical cable has somewhat similarly been employed in this role. Traditional wireless technologies in the 2.4 and 5 GHz frequency bands are also used.
Unfortunately all of these prior art systems have disadvantages. Wire and optical cable consume appreciable material and require routing between the various locations using the information, often entailing considerable design complexity. The conventional wireless technologies also often entail considerable design complexity, both to ensure that the integrity of the information is maintained against corrupting influence from outside the vehicle as well as to ensure that the energy being used to communicate the information does not become a corrupting influence on other systems.
These concerns are exacerbated in the context of vehicles. Firstly, a vehicle has particular structure. It has compartments, that is, spaces or cavities. These include large compartments, which are here termed “major compartments.” For example and without limitation, in a common automobile the major compartments are the engine or under-hood compartment, the passenger compartment, and the trunk or boot. In a common freight-hauling truck the major compartments are the engine compartment, driver/passenger compartment, and the cargo area. In common vehicles the glove box or other interior storage areas, for instance, are not major compartments. As a generalization, physical access to the major compartments of a vehicle is usually available. In contrast, physical access to the other compartments of a vehicle often is problematical.
Secondly, a vehicle is mobile by its very nature. Its systems therefore have the ability to be corruptingly influenced or to become a corrupting influence in highly varying and very difficult to predict manners. For an example, consider the traditional wireless technologies in the 2.4 or 5 GHz frequency bands. If a vehicle employing these is brought near sensitive electronic equipment it may cause disruption of that equipment. Conversely, the very same vehicle may itself be severely disrupted if brought near high powered electronic equipment. These concerns complicate information communication within (which we will regard here as including attached to the outside of) and in close proximity to vehicles.
Accordingly, what is needed are better systems for communications within and near to vehicles. Such systems should preferably have the capability for a single transmission to reach all of the vehicle compartments, as well as the near proximity outside the vehicle, without the use of repeaters or multiple physical access points.
DISCLOSURE OF INVENTION
Accordingly, it is an object of the present invention to provide an exciter system and excitation methods for communications within and very near to vehicles.
Briefly, one preferred embodiment of the present invention is a system for communicating information between a first location within a vehicle and a second location either within or very near to the vehicle. The vehicle has a conductive metallic structure defining one or more major compartments. An exciter unit is provided that includes a first communication equipment and an exciter device that is conductively connected to the metallic structure of the vehicle. A remote unit is also provided that includes a second communication equipment having a probe that is not conductively connected to the metallic structure of the vehicle. The first communication equipment may accept the information at the first location and modulate a signal with it. The signal has a carrier frequency that exhibits cut-off at one half-wavelength, as defined by the smallest dimension of the major compartments of the vehicle. Operation at frequencies below cut-off produces evanescent electromagnetic fields. Operation at frequencies above cut-off produces the more conventional propagating electromagnetic fields. The exciter device can then receive the signal from the first communication equipment and conductively inject it as a current into the metallic structure of the vehicle such that an electromagnetic field is produced. The second communication equipment then is able to couplingly receive the electromagnetic field from the metallic structure of the vehicle via the probe, demodulate the information from the electromagnetic field, and provide the information at the second location. The second communication equipment also may accept the information at the second location, modulate the electromagnetic field with it, and couplingly transmit the electromagnetic field into the metallic structure of the vehicle via the probe, such that the current is generated there in. The exciter device then may conductively extract the signal, as the current, from the metallic structure of the vehicle and provide it to the first communication equipment. The first communication equipment is then able to demodulate the information from the signal and provide it at the first location. This accordingly provides the ability to communicate the information between the first location and the second location in a wireless manner.
Briefly, another preferred embodiment of the present invention is a system for communicating information between at least two locations within a vehicle. The vehicle has a conductive metallic structure defining one or more major compartments. A number of exciter units are provided, equaling the number of the locations and each including a communication equipment and an exciter device that is conductively connected to the metallic structure of the vehicle. The communication equipment may each accept the information at its respective location and modulate a signal with it, wherein the signal alternates at a radio frequency. The exciter devices may then receive the signal from their respective communication equipment and conductively inject it as a current into the metallic structure of the vehicle. The exciter devices may each also conductively extract the current from the metallic structure of the vehicle, obtain the signal from the current, and provide the signal to its respective communication equipment. The communication equipment may then demodulate the information from the signal and provide it at its respective location. This accordingly provides the ability to communicate the information between the locations in a wired equivalent manner.
An advantage of the present invention for wireless vehicle communications is that the dimensions of vehicles, particularly for the major compartments within a vehicle, are generally small with respect to the radio frequency (RF) wavelengths for proposed operations. This results in reduced transmission path losses thereby reducing the communications transmitter power required. Another aspect of the small vehicle interior dimensions with respect to operating wavelengths is that the dominant electromagnetic field within the vehicle will be evanescent fields generated by the exciter injected RF currents in the vehicle's metallic structure. Evanescent fields do not propagate and thereby do not introduce blockage or multipath effects within the vehicle, effects common to conventional propagation systems.
Another advantage of the invention for wireless vehicle communications is that at frequencies above cutoff, where cutoff occurs when the wavelength equals ½ the smallest dimension of the major compartments of the vehicle, the invention continues to inject cur
Chadwick George G.
Collins, IV Edward
Haight Robert W.
Cocomo MB Communications, Inc.
Cong Le Thanh
Hughes Michael J.
IPLO -Intellectual Property Law Offices
Nguyen Thuan T.
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