Telecommunications – Carrier wave repeater or relay system – With transmission line
Patent
1994-10-13
1997-02-11
Pham, Chi H.
Telecommunications
Carrier wave repeater or relay system
With transmission line
455 15, 455 20, 455 332, 455 561, H04B 726, H04B 715
Patent
active
056030800
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to radio coverage in environments that are otherwise closed off to such coverage, and more particularly to cellular radio communications coverage in such closed off environments by means of repeaters, and even more particularly to a repeater system which converts communications system high radio frequency signals into low radio frequency signals for propagation in the closed off environment, and then back into high radio frequency signals.
2. Related Art
In a cellular telephone system, each portable telephone, referred to here as a mobile unit, is able to function only to the extent that it is able to send and receive radio signals to and from a base station associated with the system. However, in the real world environment there are impediments to normal radio communication. For example, at frequencies of approximately 1 GHz or higher, obstructions such as tunnels can attenuate the radio signal 50 dB/km up to total cut-off. The mount of attenuation will depend on circumstances such as the shape of the tunnel, and the presence of obstructions like trains. This attenuation makes the radio propagation environment erratic and unreliable.
Prior attempts to radiate radio frequency (RF) power into problematic isolated structures, referred to here as closed environments, include the use of leaky coaxial cable in the structure, and also the brute force approach of directing a large RF power level into the structure. However, such approaches have proven to be both expensive and prohibitively complicated.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide a simple and cost effective approach to providing radio coverage in closed environments.
Another object of the invention is to extend a cellular telephone architecture into a closed environment so that the closed environment is subdivided into several cells, and to provide for the hand off of frequencies between them as a mobile unit moves from one cell to another.
A further object of the invention is to offer a simple and cost effective solution which can be implemented as an "add-on kit" to present radio hardware without substantial change or extra cost to this hardware.
According to the present invention, the foregoing and other objects are attained in a repeater system for use in a communication system that includes a base station and a mobile unit, both operating at a high radio frequency. The repeater system provides a communications link between the base station and the mobile unit when the mobile unit is located in an environment that is substantially closed off to high radio frequency communication between the base station and the mobile unit. The repeater system comprises a first linear two-way frequency converter including a high frequency port for two-way coupling to the base station, and a low frequency port for two-way coupling to a low frequency signal that is capable of distributing frequency power through the closed environment. The repeater system also includes cable transmission means connected to the low frequency port of the first linear two-way frequency converter. The cable transmission means is located within the closed environment for radiating the low frequency converted signals within the closed environment. The repeater system also includes a first antenna for wireless coupling to the cable transmission means, and a second linear two-way frequency converter including a low frequency port connected to the first antenna for two-way coupling to a low frequency signal, and a high frequency port for two-way coupling to a signal that is compatible with the high radio frequency signal used by the communications system. The repeater system also has a second antenna connected to the high frequency port of the second linear two-way frequency converter.
With the above-described structure, a mobil unit in the vicinity of the second antenna can communicate with the base station in a normal fashion. The conversion of the high fr
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Charas Philippe
Kallander Stefan E. P.
Pham Chi H.
Telefonaktiebolaget LM Ericsson
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