Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
1998-12-22
2001-11-20
Urban, Edward F. (Department: 2683)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S114100, C333S204000
Reexamination Certificate
active
06321069
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an arrangement for reducing interference of radio frequency signals particularly in a transceiver summing part comprising a conductive housing and at least one common transmission line for at least two different signals.
DESCRIPTION OF THE PRIOR ART
In a radio system, in the radio frequency parts of a transceiver, for example in a duplex filter, intermodulation arises particularly between several different signals to be transmitted, the intermodulation being caused by non-linear interfaces or ferromagnetic materials on a signal path. The non-linear interface creates various entry combinations of signals, whereby sum and beat frequencies of frequencies in the signals are generated. Some of these frequencies may appear on a transmission channel or on a reception channel, whereby they interfere with a transmission and/or reception operation and are harmful to the operation of the entire radio system.
The non-linear interface is formed, for example, by the coupling between the ground plane of a printed board arranged in a transmission line and the ground plane of a housing. The purpose of the ground plane of the printed board is to reduce interference, but the coupling to the housing causes intermodulation of signals. A non-linear effect is amplified if the coupling between ground surfaces is weak. In order to avoid non-linear effects, it is known to strengthen the coupling between the ground plane of the printed board and the housing by securing a plate to the housing with screws, whereby the ground surface of the plate is tightly pressed against the housing. Coupling can be further improved by using conductive paste or glue between the ground plane of the printed board and the housing. However, these means do not entirely remove the non-linear interface between the ground surfaces and do not therefore solve the problem produced by intermodulation of signals.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is to provide a method and an apparatus implementing the method so as to solve the above mentioned problems. This is achieved by the method of the type presented in the introduction, characterized in that, in order to reduce intermodulation distortion of signals, which arises in the summing part, the housing of the summing part is arranged to function as a ground plane for the transmission line without a separate ground plane connected to the transmission line. The preferred embodiments of the invention are disclosed in the dependent claims.
The arrangement of the invention provides many advantages. Intermodulation interfering with the operation of the transceiver and arising from a transmission signal in a non-linear coupling can be removed, and the quality of the reception in particular and the operation quality of the radio system on the whole can thus be improved.
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A photocopy of the International Search Report for PCT/FI98/00368.
Altera Law Group LLC
Nokia Telecommunications Oy
Urban Edward F.
LandOfFree
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