Wave transmission lines and networks – Resonators
Reexamination Certificate
1999-04-14
2001-04-17
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Resonators
C333S204000
Reexamination Certificate
active
06218915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dual-mode ring resonator, which is arranged on a substrate as a planar conductor ring, to which an input conductor and an output conductor are coupled.
2. Prior Art
Dual-mode ring resonators, in which two degenerate resonance modes are excited in a conductor ring, are known from the article “EXPERIMENTAL INVESTIGATION OF DUAL-MODE MICROSTRIP RING RESONATORS”, 20th European Microwave Conference 1990, pp. 901 to 906, and from IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol. 44, No. 5, May 1996, pp. 723 to 729. These dual-mode ring resonators are, for example used as bandpass filters, which should have an attenuation that is as high as possible in their attenuation band and an attenuation that is as low as possible in their passband. It is often desirable to make the transition band between the passband and the attenuation band comparatively smaller. This means that a bandpass filter is to be provided which has passband sides that are as steep as possible. A filter characteristic with steep sides or flanks is provided with the help of the dual-mode ring resonator, because this type of resonator has attenuation or blocking poles in the vicinity of the passband edges. The known dual-mode resonators are usually operated with their fundamental frequency modes. This type of fundamental frequency mode operation occurs when the length of the conductor ring is approximately equal to a single wavelength at the desired fundamental frequency. The comparatively small length of the conductor required for the fundamental frequency operation results in a small radius of curvature of the conductor ring, which results in radiation of a comparatively larger amount of electromagnetic energy. Moreover the load caused by the coupling of the input conductor and the output conductor is very high. These properties reduce the filter quality very greatly. An additional reduction of filter quality occurs because inhomogeneities in the conductor ring are needed for coupling both modes, as can be seen from both published references mentioned hereinabove. Because of the comparatively large radiation from the ring resonator, the resonance frequency depends strongly on the spacing of the ring resonator from the cover of a housing, from which the microwave radiation is fed to the ring resonator. The resonance frequency is subjected to undesirable changes due to fluctuations of the distance of the housing cover from the ring resonator, which are caused by thermal expansion of the housing or by mechanical oscillations.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a dual-mode ring resonator of the above-described type that has as high as possible a resonator quality and thus has reduced attenuation in the passband.
These objects, and others which will be made more apparent hereinafter, are attained in a dual-mode ring resonator, which is arranged on a substrate as a planar conductor ring, to which an input conductor and an output conductor are coupled.
According to the invention the conductor ring has an approximately square shape with rounded corners and the length of, or circumference of, the conductor ring is dimensioned so that the resonator operates with one of its even-numbered harmonic modes.
Because of that the distance around the conductor ring, its circumference, can be e.g. twice, four times or six times longer than when it is operated with its fundamental mode. The curvature radius of the conductor ring is greater and the coupling of the input and output conductors to the conductor ring thus loads the resonator less, whereby its radiation is significantly reduced. As a result of that its quality factor increases. Also the effect of the spacing between the ring resonator and the housing cover on the resonance frequency is strongly reduced. The greater dimensions of the conductor ring also have the advantage that it is comparatively insensitive to manufacturing tolerances.
Preferred embodiments of the invention are described in more detail in the description hereinbelow and are claimed in the appended claims.
The input and the output conductors are coupled to respective straight conductor sections of the conductor ring that are opposite from each other across the ring in one preferred embodiment. The position of the pole over and under the passband at the filter passband edges may be adjusted in a desired manner, because of the inductive coupling.
The input conductor and the output conductor can have narrowed or widened conductor sections whose length and width are selected so that these conductors are coupled to the conductor ring in such as way that reflections are reduced as much as possible.
REFERENCES:
patent: 5172084 (1992-12-01), Fiedziuszko et al.
patent: 5541559 (1996-07-01), Takahashi et al.
patent: 5684440 (1997-11-01), Yabuki et al.
patent: 0 844 682 A1 (1998-05-01), None
Knoppik, N.: “Vergleich und Gueltigkeit Verschiedener Berechnungsverfahren der Resonanzfrequenzen . . . ”, Nachrichtentechn. Z. 29 (1976) H. 2, S. 141-147.
“Stripline Dual-Mode Ring Resonator and Their Application to Microwave Devices”, by Hiroyuki Yabuki, Morikazu Sagawa, et al, IEEE Transactions on Microwave Theory and Techniques, Vo. 44, No. 5, May 1996, pp. 723-729.
“Experimental Investigation of Dual-Mode Microstrip Ring Resonator”, by M. Guglielmi and G. Gatti, 20-th Euroepan Microwave Conference 1990, pp. 901-906.
Nguyen Patricia T.
Pascal Robert
Robert & Bosch GmbH
Striker Michael
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