Wave transmission lines and networks – Resonators – Dielectric type
Reexamination Certificate
2000-01-12
2001-07-03
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Resonators
Dielectric type
C333S234000, C333S235000
Reexamination Certificate
active
06255922
ABSTRACT:
The invention relates to a microwave resonator, comprising a substantially closed housing defining a cavity and a dielectric resonator device disposed in said cavity, said dielectric resonator device including a movable dielectric tuning body, which is mechanically coupled to an external actuator via a rod for displacement inside said cavity so as to control the resonant frequency of the resonator.
Such resonators are frequently used nowadays in microwave filters, combiners and the like. When using a dielectric resonator device in a cavity, the major part of the electro-magnetic field will be concentrated to the region of the dielectric resonator device. Therefore, the dielectric material, and any other material adjacent thereto, will be heated due to power dissipation.
The document U.S. Pat. No. 4,661,790 discloses a filter including a ceramic device in a resonator cavity, wherein a ceramic tuning body is displaceable in order to adjust the resonance frequency of the filter and also to compensate for different thermal expansion of the various components thereof. The rod, which carries the tuning body, is made of a metal material, in particular copper-plated nickel steel (“INVAR”), and protrudes a small distance into the cavity.
Such a metal rod protruding into the cavity will inevitably give rise to power losses because of a strong interaction between the resonating electro-magnetic field and the metal material.
Accordingly, the main object of the present invention is to solve this problem and to provide a microwave resonator, which will secure low power losses while enabling a secure, permanent and well-defined connection between the movable rod and the tuning body, even after long use at strongly varying temperatures.
A complicating factor is that metal fittings for securing the tuning body on the rod cannot be used, since they would influence the electro-magnetic field and be excessively heated. Moreover, it is difficult to find a glue or some other permanently adhesive material, which would hold the tuning body on the rod without ageing or losing its adhesive properties upon being heated.
The stated main object is achieved in that the rod is made of an electrically non-conductive material and is provided with a resiliently biassed clamping element adapted to clamp the dielectric tuning body against a stop means on the rod. Then, the tuning body will be exactly positioned at the stop means so long as the clamping means exerts a biassing force on the tuning body.
The resiliently biassed clamping element will hold the tuning body in a well-defined position, even if the clamping element and/or the rod would expand or contract due to thermal variations. Furthermore the clamping action can be maintained even after long use, since there is no need for fasteners or adhesives which are subject to ageing or become ineffective at varying temperatures.
The rod may be displaceable by a translatory or rotary motion. Likewise, the biassing force may be exerted axially, i.e. in parallel to the axis of the rod, or in a rotational direction.
The stop means is preferably a shoulder surface between first and second portions of the rod having different diameters. The tuning body may then be formed as a ring element, which is located externally on the rod portion having the smallest diameter. Alternatively, the rod is tubular at its wider portion, in which case the tuning body is located inside the tubular portion next to the shoulder forming a transition to a narrower portion of the rod. This narrow portion may be tubular or massive.
According to an advantageous embodiment, the clamping element is biassed by a spring arranged on a portion of the rod being located outside the cavity. In such a case, the spring may be made of steel, whereas the clamping element, which is normally elongated and reaches into the cavity, may be made of an electrically non-conductive, heat resistant material, e.g. aluminium oxide, which has the additional advantage of being somewhat heat conductive so as to lead away some of the heat generated in the tuning body.
Preferably, the movable rod, which carries the tuning body, extends through the whole cavity and through holes in opposite wall portions thereof. One end portion may then be coupled to an external motor, e.g. by threaded engagement with the rotating motor shaft, whereas the other end portion, outside the cavity, is provided with a spring. Most preferably, the spring acts on a clamping element in the form of a sleeve, which in turn exerts a biassing axial force on the tuning body, the latter being formed as a ring element, e.g. of ceramic material.
These and other features are stated in the claims and will also be apparent from the detailed description below.
REFERENCES:
patent: 2103515 (1937-12-01), Conklin et al.
patent: 4661790 (1987-04-01), Gannon et al.
patent: 4728913 (1988-03-01), Ishikawa et al.
patent: 5039966 (1991-08-01), Schmid et al.
patent: 5105158 (1992-04-01), Fiedziuszko
patent: 5345203 (1994-09-01), Gentsch et al.
patent: 5440281 (1995-08-01), Wey et al.
patent: 5612655 (1997-03-01), Stronks et al.
patent: 1561442 (1980-02-01), None
Patent Abstracts of Japan, JP 8-293710 A (Yagi Antenna Co Ltd), Nov. 5, 1996.
Malmström Jan
Ostin Joakim
Sjöholm Jan
Allogon AB
Jacobson & Holman PLLC
Nguyen Patricia
Pascal Robert
LandOfFree
Microwave resonator with dielectric tuning body resiliently... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microwave resonator with dielectric tuning body resiliently..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microwave resonator with dielectric tuning body resiliently... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438573