Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-06-02
2001-03-06
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S219000, C333S235000, C333S207000, C333S223000
Reexamination Certificate
active
06198364
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a resonator filter comprising a housing structure, at least one resonator conductor in the housing structure, and a regulating means for regulating the frequency band of the resonator filter.
Resonator filters are used in base stations of mobile telephone networks, for example. In base stations, resonator filters can be used for instance as matching networks or filtering circuits in amplifiers of transceiver units. There are several different kinds of resonator filters, and a resonator usually comprises a housing or a body. Resonator filters comprising a housing structure are for instance a coaxial resonator filter or an LC filter. The housing structure of a resonator is made of metal. In coaxial resonator structures, for example, the housing structure encloses a conductor situated in the middle area of the cavity of the housing structure, this conductor being called a resonator or a resonator pin. Additionally, it is known to use so-called helix resonators, in which the resonator is formed of a helical resonator conductor.
The length of a resonator pin is generally equal to a fourth of the wavelength of a signal coming to the resonator or to half of said wavelength. For this reason, resonators are very practical in the microwave area. In solutions according to the prior art, the resonator is fastened to the bottom of the housing structure. In a solution, a regulating means implemented by a wire is fastened beside the fixing point of the resonator. The wire forms an inductive coupling. It has been possible to change the frequency band of the resonator by changing the length and the position of the wire.
In another prior art solution, the wire is fastened to the resonator. However, resonators according to the prior art show the problem that they are difficult to tune and regulate accurately to the correct frequency band in the mounting stage. In a further solution according to the prior art, soldering the wire in the resonator has led to tuning problems.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a resonator filter of novel type, which eliminates the problems associated with the prior art solutions.
This object is achieved by means of a resonator filter of the invention, which is characterised in that the regulating means is substantially transverse to the propagation direction of the resonator conductor so that the regulating means forms at least one turn around the resonator conductor transversely to the propagation direction of the resonator conductor.
Many advantages are achieved by means of the resonator filter of the invention. By this solution, the resonator filter can be provided with a coupling that makes the filter easy to regulate accurately to the correct frequency band by using a regulating means. An easy regulation is possible because only a minor change in the frequency filtered by the resonator is provided even if the distance between the turns of the regulating means is changed relatively much, for instance. In addition, the resonator filter of the solution is mechanically durable. Further, the resonator filter is easy and fast to mount in comparison to the prior art solutions.
REFERENCES:
patent: 4374370 (1983-02-01), Opovski et al.
patent: 4422058 (1983-12-01), Vizmuller
patent: 4682131 (1987-07-01), May
patent: 0673077 (1995-01-01), None
patent: 95516 (1995-09-01), None
patent: 2235339 (1991-02-01), None
ADC Telecommunications OY
Jones Stephen E.
Ladas and Parry
Lee Benny
LandOfFree
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