Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2000-08-24
2004-08-24
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S202000, C333S206000
Reexamination Certificate
active
06781480
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to duplexer dielectric filters and, more particularly, to a duplexer dielectric filter having an open area free from a conductive layer on the side surface of a dielectric block within a reception area, thus reducing the loading capacitance and increasing the coupling capacitance between neighboring resonators, and thereby producing a desired small-sized duplexer dielectric filter.
2. Description of the Prior Art
As is well known to those skilled in the art and the general public, mobile communication systems using super high frequency band waves have been largely substituted for conventional wire communication systems. Therefore, cellular phones are widely used and are subjected to active research and development to improve their operational performance and achieve the desired compactness, smallness and lightness thereof.
A duplexer filter is designed to commonly transmit and receive signals using one antenna at the same time. Such a duplexer filter comprises a reception filter and a transmission filter. The reception filter passes reception frequency components, but suppresses transmission frequency components. On the other hand, the transmission filter passes transmission frequency components, but suppresses reception frequency components. In order to use such duplexer filters in cellular phones, it is necessary that said duplexer filters be made to occupy a very small space. Such an object may be accomplished by integrated duplexer dielectric filters.
FIG. 1
is a perspective view showing the construction of a conventional integrated duplexer dielectric filter. As shown in the drawing, the conventional integrated duplexer dielectric filter comprises a dielectric block
1
having a generally cubic-shape. This duplexer dielectric filter has two filtering areas: a transmission area
10
and a reception area
20
. The dielectric block
1
has an upper surface
3
, a lower surface, and a side surface
5
. A conductive material is coated on the lower surface and the side surface
5
. A series of resonating holes
7
are regularly and parallely formed in the dielectric block
1
in such a way that the holes
7
completely extend from the upper surface
3
to the lower surface and are spaced apart from each other at regular intervals. The resonating holes
7
are entirely coated with a conductive material on their internal surfaces, thereby forming desired resonators.
A conductive pattern
9
, having a predetermined size, is formed on the upper surface
3
of the dielectric block
1
at a position around each of the resonating holes
7
. Such conductive patterns
9
are connected to the conductive layers on the internal surfaces of the resonating holes
7
, thus forming a loading capacitance between the resonating holes
7
and the conductive layer of the side surface
5
, and forming a coupling capacitance between neighboring resonators. The resonance frequency of the resonators is determined by both the resonating holes
7
and the loading capacitance, while the coupling capacitance couples the resonators to each other. The transmission area
10
and the reception area
20
of the upper and side surfaces
3
and
5
of the dielectric block
1
are provided with transmission and reception-terminals
12
a
and
12
b
for accomplishing the signal transmission and reception operation. An antenna terminal
12
c
, consisting of a conductive pattern, is formed at a position between the transmission and reception areas
10
and
20
. The transmission terminal
12
a
, the reception terminal
12
b
and the antenna terminal
12
c
are insulated from the conductive material disposed on the side surface
5
of the dielectric block by open areas
14
a
,
14
b
and
14
c
, respectively.
FIG. 2
is an equivalent circuit diagram of the duplexer dielectric filter of FIG.
1
. In
FIG. 2
, the reference character “R” denotes transmitting lines, each of which is always opened at one end thereof by an associated resonating hole
7
of the dielectric block
1
. As described above, he antenna terminal is disposed between the transmission area and the reception area. The elements related to the resonating holes
7
within the transmission area are indicated by the reference labels including the character “t”, for example, Cti, Ctij, Rti and Mtij, while the elements related to the resonating holes
7
within the reception area are indicated by the reference labels including the character “r”, for example, Cri, Crij, Rri and Mrij. The loading capacitance Cti, Cri (i=1, 2, 3), formed between the resonating holes
7
and the conductive layer on the side surface
5
of the dielectric block
1
, is connected to the open ends of the signal transmitting lines. A desired resonating circuit is formed by both the signal transmitting lines Rti, RH (i=1, 2, 3) and the loading capacitance.
In a conventional duplexer dielectric filter, it is necessary to accomplish both desired signal transmitting characteristics within a transmission frequency band and desired attenuation characteristics within a low frequency band. The desired transmission characteristics within the transmission frequency band are determined by a coupling of the resonance frequency of the resonators, determined by both the signal transmitting lines Rti, Rri and the loading capacitance Cti, Cri, the coupling capacitance Ctij, Crij (i,j=1, 2, 3), and electromagnetic coupling values Mtij, Mrij (i,j=1, 2, 3). The desired attenuation characteristics within the low frequency band are determined by a coupling. That is, both the attenuation characteristics and the frequency of an attenuation pole are determined by a combination of the coupling capacitance and magnetic coupling values.
In the conventional duplexer dielectric filters, the high frequency band within the transmission area is relatively lower than that of the reception area. Therefore, the electric field effect between the resonating holes is relatively higher within the reception area than that of the transmission area, but the magnetic field effect between the resonating holes is relatively higher in the transmission area than that of the reception area. Therefore, the resonators within the reception area form a capacitance coupling, but the resonators within the transmission area form an inductance coupling.
In such a conventional duplexer dielectric filter of
FIG. 1
, the determination of the resonance frequency or the coupling between the resonators are changed in accordance with the size of the conductive patterns
9
formed on the upper surface
3
of the dielectric block
1
. In other words, the operational characteristics of the duplexer the dielectrc filters are changed in accordance with both the gap between the conductive patterns
9
and the conductive layer of the side surface
5
, and the gap between the conductive patterns
9
.
As described above, in order to determine the resonance frequency of the duplexer dielectric filter, it is necessary to control the distance between the conductive patterns
9
, formed on the upper surface
3
of the dielectric block
1
, and the conductive layer formed on the side surface
5
of the dielectric block
1
. However, in a conventional duplexer dielectric filter, the resonance frequency within the transmission area is lower than that of the reception area, and so it is necessary to make the loading capacitance within the transmission area higher than that of the reception area. In order to form a high loading capacitance within the transmission area, it is necessary to enlarge the size of the conductive patterns
9
within the transmission area and to complicate the arrangement of those conductive patterns
9
.
The length of the signal transmitting lines within the transmission area
10
is equal to that of the reception area
20
, and so it is necessary to properly control both the loading capacitance and the coupling capacitance so as to accomplish the desired filtering characteristics of the duplexer dielectric fil
Kim Byung Taek
Lee Byoung HWA
Lee Benny
Renner , Otto, Boisselle & Sklar, LLP
Samsung Electro-Mechanics Co. Ltd.
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