Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1998-04-28
1999-12-21
Pascal, Robert
Wave transmission lines and networks
Plural channel systems
Having branched circuits
333134, 333202, 333230, 333235, 333254, 333256, 439578, H01P 504, H01P 1213
Patent
active
060054530
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of tuning a summing network of a base station, the summing network comprising: transmitters, filter means with in-connectors for receiving signals supplied by the transmitters and out-connectors for forwarding filtered signals, and combiner means with in-connectors for receiving and combining the signals obtained from the out-connectors of the filter means and an out-connector for supplying the combined signals to antenna means of the base station, at least one of said connectors being a coaxial connector and comprising an elongated inner conductor and a substantially tubular conductor that surrounds the inner conductor and is arranged coaxially with the inner conductor. The invention also relates to a coaxial connector comprising an elongated inner conductor and a substantially tubular conductor that surrounds the inner conductor and is arranged coaxially with the inner conductor. The invention further relates to a band-pass filter comprising a resonator means, an in-connector for receiving signals to be filtered and for supplying them to an electromagnetic field of the resonator, and an out-connector for receiving filtered signals from the electromagnetic field of the resonator means and for supplying them further, at least one of the connectors being a coaxial connector and comprising an elongated inner conductor and a substantially tubular conductor that surrounds the inner conductor and is arranged coaxially with the inner conductor.
The invention particularly relates to a summing network of combiner filters of a base station in a cellular radio system. A combiner filter is a narrowband band-pass filter in resonance with (tuned to) the carrier frequency of a transmitter connected to it. The adjustment range of the filters is usually 2-10% of the medium frequency. The signals obtained from the outputs of the combiner filters are summed by the summing network of the base station and supplied to the antenna of the base station. The summing network usually comprises a coaxial cable which leads to the antenna of the base station and to which the combiner filters are connected. In order that a maximum amount of the transmission power of the transmitters could transfer to the antenna, the summing network must be tuned to the frequency channels used by the transmitters of the base station. To be exact, the summing network is tuned at only one frequency, but with movement away from the optimum frequency, the mismatch will not rise strikingly at first. In the base stations of cellular radio systems, the summing network can thus usually be used at a frequency band with a width of about 1 to 3% of the medium frequency of the frequency band.
Tuning of previously known summing networks is based on the use of transmission lines of a precise defined length, proportional to the wavelength. This sets high requirements to the cabling of a summing network, since the transmission lines must be of exactly the correct length so as to optimize the summing network to the correct frequency. Because of the tolerance requirements for the length of the cables required by the branches of the summing network, summing networks are quite expensive. As the operating frequency grows, the wavelength is reduced, and, on the other hand, as the physical size of the equipment sets certain requirements to the mechanical length of the summing network, the electric length of the summing network easily grows too long and the operating band of the combiner will narrow. The operating frequency band of the transmission combiner is thus in practice determined by the summing network, i.e. if the operating band is to be changed, the summing network or part of the network must be changed.
As automatically (remote control) adjustable combiner filters have become more common, a need has arisen for changing the tuning of the summing network in a simple and quick manner. The useful frequency band of the summing network is in practice so narrow that the frequency channels of the transmitters of
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Ahonpaa Timo
Sarkka Veli-Matti
Nokia Telecommunications Oy
Pascal Robert
Summons Barbara
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