Telecommunications – Carrier wave repeater or relay system – Plural modulated carriers
Patent
1996-05-14
1998-09-15
Le, Thanh Cong
Telecommunications
Carrier wave repeater or relay system
Plural modulated carriers
455 22, H04B 715
Patent
active
058093982
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to an amplification device, a so-called repeater, for receiving and transmitting RF signals, which are preferably analogically or digitally frequency modulated and are present in cellular telecommunication systems. Specifically, the invention relates to a repeater which improves, through reception, amplification, and, preferably directed, re-transmission of the RF signals, transmitting and receiving performance of a, preferably, mobile terminal and a, preferably, stationary radio unit, in particular a base station, in one or several parts of a cell in at least one cellular telecommunication system.
2. Description of the Related Art
Prior art repeaters of the present type normally include two principally similar branches, one branch for down-link communication from the base station to the mobile terminal (the cellular telephone), and one branch for up-link communication from the mobile terminal to the base station. Each of these branches include for instance connection for said incoming signals, the latter being connected to channel selecting means, which includes wherein and channel selecting means, the output of said combiner being connected in turn, via a power amplifier, to the connection of the duplex means for outgoing signals in the second branch. This provides improved transmitting and receiving performance through an amplification and, possibly, a re-direction of the RF signals in the frequency ranges required for the radio communication between the subscriber terminal and the base station.
A prior art repeater of above mentioned type does not have a very high degree of efficiency due to the way in which its power amplifiers are arranged. These power amplifiers amplify all, or at least several, frequency ranges or channels amplified by the repeater. This requires firstly that each power amplifier is capable of providing all of the required output power for its respective branch. Secondly, it is required, as is customary in these applications, that the amplifier does not generate such high levels of mixing frequencies or intermodulation products that the communication is disturbed in the system itself or in other systems. Physically, intermodulation products occur when different frequencies are mixed in a non-linear element. The above mentioned requirements on the power amplifier will not be met by an amplifier with a very high degree of efficiency. A relatively expensive and complicated, so-called, class A amplifier would probably be necessary.
This way of arranging the power amplifiers between the combiner and the duplex means thus requires high power in order to obtain such high linearity in the power amplifiers that their internal generation of intermodulation products is kept at an acceptable level.
Another repeater of a similar type is known through the U.S. Pat. No. 4,754,495, which is incorporated by reference into this disclosure. This device does not aim at solving the above mentioned problems. In its capacity of constituting relevant art it forms, however, one basis of the invention. Some important characteristics of this prior art repeater is found in the preamble of claim 1.
Another repeater is known From the U.S. Pat. No. 4,941,200. This repeater, which in addition to its amplifier function is arranged to monitor and manipulate the signalling in a cell in a radio communication systems, employs well-known prior art from base stations for controlling and amplifying RF signals in order to meet a frequent and common standard for cellular telecommunication.
SUMMARY OF THE INVENTION
The invention is based on the object to provide a repeater, for a cellular telecommunication system, said repeater having a simpler design, a lower demand for maintenance, and a high degree of efficiency in combination with high power capacity and generation of low levels only of intermodulation products. A repeater according to the invention is intended mainly for raising (in a part of a cell) the levels and, possibly, converting the freque
REFERENCES:
patent: 4317216 (1982-02-01), Kaegebein
patent: 4754495 (1988-06-01), Kawano et al.
patent: 4941200 (1990-07-01), Leslie et al.
Moberg Tommy
Pravitz Anders
Allgon AB
Cong Le Thanh
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