Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-10-19
2001-08-21
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S202000, C333S134000
Reexamination Certificate
active
06278343
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric filter, a dielectric duplexer, and a communication apparatus using the same, which are used, for instance, in a microwave band.
2. Description of the Related Art
FIGS. 11A and 11B
show an example of a structure of a conventional dielectric filter, in which the effects of electromagnetic field leakage are reduced by providing an open terminal indented from an end surface of a dielectric block, thereby obtaining the desired coupling between resonators.
FIG. 11A
is a perspective view from the open end, and
FIG. 11B
is a cross-sectional view taken horizontally through the center.
The dielectric filter comprises inner conductors
13
a
and
13
b
, which are provided in through-holes
12
a
and
12
b
, respectively, running between two opposing end surfaces of a dielectric block
11
. A ground conductor
15
is provided substantially over all outer surfaces of the dielectric block
11
. Input/output electrodes
16
a
and
16
b
are provided extending from one major surface, which constitutes a mounting surface, to the side faces. In the inner conductors
13
a
and
13
b
(hereinafter referred to as open-side end surface) of each of the through-holes
12
a
and
12
b
, portions devoid of inner conductor i.e., nonconductive portion g are provided near one open surface. These nonconductive portions g function as open terminals, and the ground conductor
15
is short-circuited at the other open surface (hereinafter referred to as short-circuiting-side end surface).
The dielectric filter comprises two resonators formed by the inner conductors
13
a
and
13
b
. The resonators are coupled together by stray capacitance Cs, created in the nonconductive portions g, and are coupled externally by external coupling capacitance Ce, created between the inner conductors
13
a
and
13
b
and the corresponding inpu/output electrodes
16
a
and
16
b
. The external coupling capacitance Ce is adjusted by altering the position and area of the input/output electrodes
16
a
and
16
b
to achieve an appropriate external coupling.
Ordinarily, the greater the area of the input/output electrodes, and the closer the electrodes are positioned to the short-circuiting-side end surface, the worse the Qo of the resonators. That is, in order to prevent deterioration in the Qo, the input/output electrodes must be positioned closer to the open-side end surface and their areas must be reduced.
However, the conventional dielectric filter described above has a disadvantage in that, although it is possible to prevent deterioration in the Qo by providing the input/output electrodes near to the open-side end surface, the nonconductive portions g are provided at positions indented from the open-side end surface, and consequently the opposing area of the input/output electrodes and the inner conductors is reduced, thereby reducing the external coupling capacitance and making it impossible to obtain a desired external coupling.
There is a further problem in that operations such as changing the orientation of the dielectric block are necessary to provide the input/output electrodes on opposite side faces as in the conventional example described above, consequently increasing the cost of providing the input/output electrodes. Furthermore, when the input/output electrodes are provided only on the mounting surface, it is not easy to confirm the state of the solder after mounting.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a dielectric filter, a dielectric duplexer, and a communication apparatus capable of obtaining a desired external coupling with no deterioration in Qo, which are inexpensive and have excellent characteristics.
One preferred embodiment of the present invention provides a dielectric filter comprising: a plurality of through-holes provided between a pair of opposing end surfaces of a dielectric block; inner conductors provided inside the through-holes; a ground conductor provided on the outer surfaces of the dielectric block; nonconductive portions provided near one end surface, said end surface being regarded as an open-side end surface, and one major surface of the dielectric block being regarded as a mounting surface; at least part of a ridgeline between the open-side end surface and the mounting surface of the dielectric block being removed; and at least one input/output electrode, which is capacitance-coupled to a predetermined inner conductor, being provided crossing from the removed portion to the mounting surface.
Preferably, the removed portion forms a slope, a curved face, or a step.
Another preferred embodiment of the present invention provides a dielectric duplexer comprising at least two filter portions provided in a dielectric block, and at least one of the filter portions is the dielectric filter according to the present invention.
Yet another preferred embodiment of the present invention provides a communication apparatus comprising at least one of the dielectric filters and the dielectric duplexer of the present invention.
In the dielectric filter and dielectric duplexer of the configuration described above, since the ridgeline between the open-side end surface and the mounting surface of the dielectric block is removed, and input/output electrodes are provided crossing from the removed portion to the mounting surface, shortening the distance between the input/output electrodes and the inner conductors, a greater external coupling capacitance can be obtained. More specifically, the input/output electrode in the configuration of the present invention achieves a greater external coupling than a conventional input/output electrode of the same area, and can achieve the same external coupling capacitance while having a smaller area.
That is, even when the open end is indented at a position further inward than the open-side end surface, the input/output electrodes can be provided near the open-side end surface. In addition, the area of the input/output electrodes is small, making it possible to easily obtain a desired external coupling capacitance. Therefore, a desired external coupling can be achieved without adversely affecting the Qo of the resonators.
Furthermore, the removed portion can be more easily molded and cut away by making it a sloping face, a curved face, or a step. In addition, the input/output electrodes can be easily provided. These operations can be particularly easily performed when the removed portion is a slope.
Furthermore, since the input/output electrodes are provided only in one direction on the mounting surface side, they can be provided easily and with high precision. In addition, the state of the solder from the open-side end surface can be confirmed after mounting.
It is only necessary that at least one of the multiple input/output electrodes has the configuration of the present invention. The other input/output portions may be externally coupled by other means such as, for instance, external coupling holes.
Furthermore, the communication apparatus of the present invention comprises the dielectric filter or the dielectric duplexer having the characteristics described above. Consequently, the communication apparatus is inexpensive and has excellent characteristics.
REFERENCES:
patent: 5327109 (1994-07-01), Hoang et al.
patent: 5783980 (1998-07-01), Blair er al.
patent: 5929725 (1999-07-01), Toda et al.
patent: 6064283 (2000-05-01), Asada
patent: 43 19 214 A1 (1994-12-01), None
patent: 4-356801 (1992-12-01), None
patent: 08-032307 A (1994-07-01), None
patent: 11-205014 (1999-07-01), None
Search Report.
Ishihara Jinsei
Kato Hideyuki
Okada Takahiro
Murata Manufacturing Co. Ltd.
Nguyen Patricia T.
Ostrolenk Faber Gerb & Soffen, LLP
Pascal Robert
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