Wave transmission lines and networks – Resonators – Coaxial or shielded
Reexamination Certificate
1999-06-24
2001-04-24
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Resonators
Coaxial or shielded
C333S206000, C333S227000, C333S203000, C333S230000
Reexamination Certificate
active
06222432
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention regards a quarter-wave coaxial cavity resonator for use in wide-band filters or combiners.
DESCRIPTION OF RELATED ART
A quarter-wave coaxial cavity resonator having a cavity comprising a cylindrical wall portion having a central symmetry axis, a bottom wall and a top wall joining the cylindrical wall at right angles, a right cylindrical resonator rod arranged coaxially along the axis and having a first end fixed from the bottom wall and a second end at a distance from the top wall, and means for feeding microwave energy to the resonator is well-known. Such resonators have been in practical use for at least some 20 years. They may have a theoretical unloaded Q value as high as 7000 and habitually reach 4000 to 6000 in manufactures for the frequency of 1.8 GHz, which is a common frequency band for telecommunication use. As the name of the device indicates, the length of the resonator rod corresponds to a quarter of the wavelength for the resonant frequency.
SUMMARY OF THE INVENTION
It is a particular object of the present invention to obtain a resonator of this type having a suitable coupling for broad-band use. Particularly in the telecommunications field, much information is sent and receive din broad microwave bands, and there exist particular problems in obtaining components which are as linear as possible in order to reduce all kinds of intermodulation.
The general tendency at present is to work with frequency bands which are as broad as possible. For example, and for the frequency band around 1.8-1.9 GHz, it is now often desired to obtain useful bandwidths of 40 MHz and even up to 80 MHz. However, already 40 MHz is a difficult limit to reach for resonators at a realistic level of signal load, since a broad bandwidth requires a high degree of coupling, and an increased coupling at a given level will lead to increased losses. Some sacrifice of Q value is therefore unavoidable in order to increase the bandwidth. It is thus an object of the invention to improve the general conditions for this balance of factors.
This object and other objects and advantages are obtained, according to the present invention, by a particular type of field coupling in a quarter-wave coaxial cavity resonator of the kind recited. Thus, an antenna having a T form is arranged within the resonator cavity in the way specified in the claims.
Although the cylindrical wall is normally a right cylindrical wall, it should be understood that in the present disclosure, the concept of cylindrical comprises not only the right cylinder having a circle as a generating curve, but comprises any form of generating curve, e.g., quadratic, or even have any regular form like a regular polygon. The same is true for the cylindrical resonator rod. For practical reasons of manufacture, however, this outer wall of the coaxial system is often made with a circular section.
With this geometry for the antenna, which is substantially a quarter-wave long, the fixed first end of the arm portion, joined with low reactance with the bottom of the resonator and with the bottom end of the resonator rod, will have maximum current and the free end thereof is at a current mode.
REFERENCES:
patent: 5262742 (1993-11-01), Bentivenga
patent: 5285178 (1994-02-01), Ahlberg
patent: 5389903 (1995-02-01), Piirainen
patent: 0 788 184 (1997-08-01), None
patent: WO 97/25753 (1997-07-01), None
Jones Stephen E.
Lee Benny
Telefonaktiebolaget L M Ericsson (publ)
Young & Thompson
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