Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-06-15
2001-04-24
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S219100, C333S235000
Reexamination Certificate
active
06222428
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to tuning assembly for tuning a dielectric resonator in a cavity defined by cavity walls. The invention also concerns a filter employing such a tuning assembly.
The dielectric resonator includes two resonator bodies, namely a stationary resonator body and a movable resonator body, each of the two resonator bodies being made of a low-loss, high dielectric constant material.
The tuning assembly comprises a support structure mounted in an opening in a mounting wall, constituting one of the cavity walls, for supporting the two resonator bodies within the cavity. The support structure includes two mutually slidable support elements, viz. a first support element, including a tubular sleeve portion, for supporting a first one of the two resonator bodies, and a second support element, including a shaft extending axially through the mounting wall opening and inside the tubular sleeve portion, for supporting a second one of the two resonator bodies. One of the support elements is displaceable from the outside by a tuning adjustment means to effect an adjustment movement of one resonator body in relation to the other resonator body, whereby a resonant frequency of the dielectric resonator in the cavity can be tuned.
2. Prior Art
Such a tuning assembly is previously known from the published international patent application WO 97/02617 (Allen Telecom). The known tuning assembly is disposed in a filter including a number of neighbouring cavities, each having a dielectric resonator and a plastic resonator support. The resonator support is mounted in one mounting wall only. Thus, unlike many similar support structures, it is not guided or supported in the opposite wall of the casing. A tuning assembly of the latter kind is disclosed in WO98/56062 (Allgon AB), the contents of which are incorporated herein by reference.
In one embodiment, shown in FIGS. 8 through 10 of the first-mentioned document WO 97/02617, the dielectric resonator includes two cylindrical resonator bodies in the form annular ring members, one stationary and one movable, both of them being made of a low-loss, high dielectric constant ceramic material. The first, stationary resonator body is mounted on a plastic support in the form of a cylindrical sleeve having a plurality of longitudinal recesses and openings so as to make the support somewhat flexible. At the inner end, to be located inside the cavity, the sleeve is cut out so as to form a number of spaced apart holding elements or arms diverging from a shoulder. When mounting the first, stationary resonator body onto the plastic support, it is pushed with its central axial hole onto the diverging arms.
When the first, stationary resonator body reaches a position where it abuts the shoulder of the plastic support, the arms will snap radially outwardly and engage with cantilevered stops onto the upper or inner surface of the cylindrical resonator body so as to hold the latter with a clamping force between the cantilevered stops and the shoulder. In this way, the first resonator body will be held substantially stationary by the plastic support.
The second resonator body, on the other hand, is secured to an adjustment shaft, which is mounted so as to extend through the mounting wall opening and axially inside the supporting cylindrical sleeve. The adjustment shaft is threaded at an axially outer portion thereof and is rotatable so as to perform a linear movement in relation to the plastic support and the first, stationary resonator body. The rotational movement can be accomplished manually, by means of a knurled outer head on the shaft, or automatically by a stepping motor. Thus, tuning can be achieved by such a movement of the adjustment shaft and an associated displacement of the second resonator body in relation to the first resonator body.
However, the plastic material of the support structure, which is necessarily flexible to enable the desired snap locking of the first resonator body, will inevitably make the mounting of the first resonator body somewhat resilient and not quite exact in a fixed position. Moreover, the adjustment shaft, which extends freely inside the support sleeve, is allowed to orient itself at a slight inclinational angle in relation to the support sleeve, whereby the second resonator body will be tilted in relation to the first resonator body.
Accordingly, the mounting of the first resonator body onto the support structure is not quite exact, and the tuning can only be achieved approximately, i.e. for a given rotational movement of the adjustment shaft, the mutual positions of the first and second resonator bodies can vary somewhat with an associated shift of the resonant frequency.
SUMMARY OF THE INVENTION
Against this background, a main object of the invention is to provide a tuning assembly, which is more precise in its tuning process, so that a given adjustment movement will result in a predetermined, exact resonant frequency.
A further object is to provide a tuning assembly which is easy to manufacture and assemble.
Still another object is to provide a structure of the tuning assembly which will secure an efficient transfer of heat from the dielectric resonator to the outside of the cavity.
The stated main object is achieved for a tuning assembly, comprising:
a mounting wall constituting at least a part of one of the cavity walls and having an inside defining the cavity and an outside provided with a tuning adjustment means. There is
a support structure mounted in an opening in the mounting wall for supporting the two resonator bodies on the inside of the mounting wall.
The support structure including two mutually slidable support elements, each being made of a rigid material, with
a first support element including a tubular sleeve portion and a radially outer support means for clamping a first one of said two resonator bodies axially between the tubular sleeve portion and the radially outer support means, and
a second support element including a shaft being radially journalled by bearing means inside the tubular sleeve portion, at least in a region located axially inside the mounting wall, and carrying at an end portion thereof a second one of the two resonator bodies.
One of said two mutually slidable support elements being held stationary in relation to the mounting wall, whereas the other one of said two mutually slidable suppor elements is axially movable of the tuning adjustment means on the outside of said mounting wall.
The two slidable support elements are exactly aligned in relation to each other, and the two resonator bodies are precisely positionable in relation to each other so as to tune a resonant frequency of the dielectric resonator.
Accordingly, the frequency tuning can be made very precise, and the relative positions of the two resonator bodies will be retained exactly, even if the assembly is disturbed by vibrations or other movements. Nevertheless, the manufacture of the tuning assembly, and the mounting of the various parts are relatively inexpensive and easy to carry out in practice.
It is important that the shaft is journalled precisely by bearing means inside the tubular sleeve portion, at least in the region axially inside the mounting wall, so that the shaft and the tubular sleeve portion, and thus the two mutually slidable support elements, are aligned exactly relative to each other.
In order to achieve improved stability, the radially outer support means of the first support element is preferably located radially outside the tubular sleeve portion, e.g. in the form of an outer sleeve. Advantageously, the latter is heat conductive so as to lead away the heat generated in the first resonator body to the mounting wall.
A practical way to achieve an axial clamping force between the tubular sleeve portion and the radially outer support means is to mount the tubular sleeve portion slidably in the mounting wall opening and to apply a resilient load outside the opening, e.g., by means of a spring member, so that the tubular sleeve portion e
Akesson Daniel
Malmström Jan
Allgon AB
Jacobson Price Holman & Stern PLLC
Jones Stephen E.
Lee Benny
LandOfFree
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