Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-05-03
2001-10-16
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S202000, C333S230000
Reexamination Certificate
active
06304160
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to cavity resonators and, more particularly, to coupling mechanisms for, and a filter using, TE
01&dgr;
and TE
011
mode resonators.
2. Description of the Related Art
In numerous electrical devices, such as electromagnetic filters, pairs of resonators are coupled together to pass electromagnetic energy from one resonator to the other resonator. The electromagnetic frequency response of individual resonators allows multiple resonators to be connected to create an electromagnetic filter having a desired frequency response. Currently, several different mechanisms are used to couple resonators. In one arrangement used for cylindrical TE
011
and TE
01&dgr;
mode resonators, each of the resonators has a slot in the longitudinal direction that exposes the internal cavity of the resonator to an external environment. The resonators are positioned in close proximity to each other with the slots aligned to couple magnetic fields within the resonators, thereby facilitating communication of the electromagnetic energy between the resonators.
In another arrangement, the resonators are connected by a conductive filament. The end portions of the filament form probes that extend into the inner cavities of the resonators. In this arrangement, the electromagnetic field in one resonator creates a current in the filament which, in turn, creates an electromagnetic field in the other resonator.
In coupling arrangements such as those described above, the coupling mechanism cannot be adjusted after assembly is complete. The electromagnetic field created in the second resonator may be out of phase with the electromagnetic field in the first resonator by a given amount which is determined by the characteristics of the coupling mechanism. This phase difference is constant regardless of the magnitude of the electromagnetic field in the first resonator. Additionally, the magnitude of the electromagnetic field in the second resonator is varied only by varying the magnitude of the electromagnetic field in the first resonator. In this way, the operation of the coupled resonators is set when the resonators are coupled together.
Therefore, there is a need for an improved coupling mechanism for TE
011
and TE
01&dgr;
resonators that provides an adjustable coupling between the resonators, and which allows adjustment of the magnitude and/or phase of the electromagnetic energy passed from the first resonator to the second resonator. A need also exists for improved coupling mechanisms that couple two resonators with waveguides to provide control of the relative coupling of the electromagnetic energy that is transferred between the waveguide and the coupled resonators.
SUMMARY OF THE INVENTION
The present invention may be embodied in a coupled-cavity microwave filter including an input port; a first resonator having a first opening, wherein the first opening receives electromagnetic energy from the input port; and a second resonator having a second opening, wherein the second opening receives electromagnetic energy from the input port and wherein the first resonator and the second resonator are electromagnetically coupled. The present invention may also include an output port; a third resonator having a third opening, wherein the third opening transfers electromagnetic energy to the output port and wherein the second resonator and the third resonator are electromagnetically coupled; and a fourth resonator having a fourth opening, wherein the fourth opening transfers electromagnetic energy to the output port and wherein the third resonator and the fourth resonator are electromagnetically coupled.
In some embodiments, the first opening may be a first distance from the input port while the second opening may be a second distance from the input port, and the third opening may be a third distance from the output port while the fourth opening may be a fourth distance from the output port.
In certain embodiments the first distance may be approximately equal to the second distance, thereby creating positive coupling. In other embodiments, a difference between the first distance and the second distance may be approximately one-half of a wavelength at which the first and second resonators operate, thereby creating negative coupling.
In certain other embodiments, the third distance may be approximately equal to the fourth distance, thereby creating positive coupling. Whereas, in other embodiments a difference between the third distance and the fourth distance may be approximately one-half of a wavelength at which the third and fourth resonators operate, thereby creating negative coupling.
In some embodiments, the second resonator may be directly coupled to the third resonator. In other embodiments, the second resonator may be coupled to the third resonator through a plurality of resonators, which may include four resonators.
In any of the foregoing embodiments, the first, second, third and fourth resonators may be tuned to operate at approximately a single frequency.
The first and second resonators may be electromagnetically coupled through an opening including tuning screws to adjust the coupling between the resonators. Additionally the third and fourth resonators may be electomagnetically coupled through an opening, which may include tuning screws to adjust the coupling between the resonators. Moreover, tuning screws may also be disposed in each of the first, second, third and fourth openings.
The features and advantages of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below.
REFERENCES:
patent: 4453146 (1984-06-01), Fiedziuszko
patent: 5608363 (1997-03-01), Cameron et al.
patent: 5684438 (1997-11-01), Cavalieri D'Oro et al.
patent: 5841330 (1998-11-01), Wenzel et al.
patent: 6150907 (2000-11-01), Loi et al.
Loi Keith N.
Tatomir Paul J.
Gudmestad Terje
Lee Benny
Nguyen Patricia T.
The Boeing Company
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