Dielectric filter having coupling windows between...

Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention

Reexamination Certificate

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Details

C333S202000, C333S206000, C333S222000, C333S134000

Reexamination Certificate

active

06243564

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a dielectric filter comprising a plurality of dielectric blocks and a transceiver using the dielectric filter.
PRIOR ART
In a conventional dielectric filter of the kind referred to above, there are provided a plurality of resonators in a hexahedral rectangular dielectric unit. All of the six surfaces of the filter are substantially coated with an electrode film, and therefore, the filter does not require a shielding case or a mounting bracket, that is, the filter is able to be mounted on the surface of a circuit board. In the conventional structure as described above, since a plurality of resonators are provided in one dielectric block, many different kinds of molds must be provided if filters having different numbers of resonators are desired. More specifically, as the dielectric filter of this type is generally formed of ceramic material, the dielectric filter is manufactured by placing a ceramic material powder in a mold and baking the mold. Therefore, a different mold must be prepared for each type of filter to be manufactured, thus raising manufacturing costs. Moreover, since the distance between the resonators is determined by the size and shape of each mold, the degree of coupling between the resonators is hard to set.
In another example of a conventional dielectric filter of a comb line type, the degree of coupling of the resonators and the frequency of each resonator are interrelated as a function of the structure of the filter. One is changed when the other is changed, and each affects the other, and therefore, it is difficult to adjust the resonant frequency and the degree of coupling independently of each other.
In a further example of a known dielectric filter, a single resonator is provided in a single dielectric block which is coupled with another dielectric block having a resonator. Since a separate element is used to couple the dielectric blocks in this example, the structure is complicated and the number of parts is increased. This complicates manufacturing procedures and increases manufacturing costs.
Yet another known dielectric filter is composed of a plurality of dielectric bodies, each of which is provided with a resonator and bonded together to form a unit. The resonator used is a quarter-wave resonator wherein one end face is short-circuited and the other end face is open-circuited. Electromagnetic energy leaks from the open end face, leading to undesirable coupling of resonators. It is very difficult to achieve a predetermined degree of coupling with this structure. Further, a shielding cover to prevent undesired coupling with an external circuit is required. There is also a limit to the degree the transceiver can be miniaturized when this type of filter is employed.
SUMMARY OF THE INVENTION
A central object of the present invention is to provide a novel dielectric filter which can be easily manufactured to be compact in size, and with a variable number of resonators, which does not require a bracket or a shielding case and which does not require different molds for each resonator. It is a further object of the present invention to reduce the number of components and reduce manufacturing costs. It is a further object of the present invention to provide a filter wherein the resonant frequency of each resonator and the degree of coupling between resonators can be independently set or adjusted as desired.
A dielectric filter in which both the resonant frequency of each resonator and the degree of coupling between resonators can be adjusted independently. The dielectric filter includes at least first and second dielectric blocks, each having a through bore extending between first and second end faces thereof and a plurality of side surfaces extending between those end faces. Substantially all of the faces of the dielectric blocks, including the bore, are covered with a conductive film to define a first dielectric resonator whose electric energy component varies in the direction of an axis of the through bore. A first coupling electrode is formed, isolated from the conductive film, on at least one and preferably bridging between two of the side surfaces of the first dielectric block for coupling an input signal applied thereto to the first dielectric resonator. A second coupling electrode is formed, isolated from the conductive film, on a second one of the side surfaces of the first dielectric block in a location wherein the electric energy component in the first dielectric block is at a relatively high level so that electric energy in the first dielectric block exits the first dielectric block via the second coupling electrode. The second dielectric block has a first side surface which abuts the second side surface of the first dielectric block. A third coupling electrode is formed on the first side surface of the second dielectric block at a location corresponding to the second coupling electrode such that electric energy leaving the first dielectric block via the second coupling electrode enters the second dielectric block via the third coupling electrode and sets up an electromagnetic field in the second dielectric block whose electric energy component varies in the direction of the through bore of the second dielectric block. A fourth coupling electrode is formed on at least one and preferably bridging between two of the surfaces of the second dielectric block at a location where the resonant electric energy component in the second dielectric block is relatively high such that electric energy in the second dielectric block leaves the dielectric block via the fourth coupling electrode.
A transceiver according to the present invention can be miniaturized by using the dielectric filter of the present invention mentioned above.


REFERENCES:
patent: 5130683 (1992-07-01), Agahi-Keshah et al.
patent: 6026281 (2000-02-01), Yorita
patent: 6075975 (2000-06-01), Yorita
patent: 53601 (1989-03-01), None

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