Duplexer dielectric filter

Details Duplexer dielectric filter Duplexer dielectric filter

1998-12-16

2001-01-02

Pascal, Robert (Department: 2817)

Wave transmission lines and networks

Coupling networks

Wave filters including long line elements

C333S207000, C333S222000, C333S134000

Utility Patent

active

06169465

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a duplexer dielectric filter used in a mobile communication terminal equipment having high frequency band charateristics, and more particularly to the duplexer dielectric filter in which predetermined conductive patterns are formed on a first surface of a dielectric block to form an electromagnetic coupling between adjacent resonators, whereby a small and light filter can be manufactured and a resonant frequency of a resonator can be adjusted easily.
BACKGROUND OF THE INVENTION
In the duplexer dielectric filter, generally, the signal is transmitted and received simultaneously through an antenna. The duplexer filter comprises a receiving-end filter and a transmitting-end filter, the receiving-end filter has a passing characteristic for the receiving frequency and a stopping characteristics for the transmitting frequency, while the transmitting-end filter has the passing characteristics for the transmitting frequency and the stopping characteristics for the receiving frequency. This duplexer filter has to be reduced in volume for the current mobile communication equipments. For the reduced filter, the duplexer dielectric filter has been introduced.
FIG. 1
is a perspective view illustrating a conventional integrated type duplexer dielectric filter. As shown in figure, the conventional duplexer dielectric filter comprises a dielectric block
10
divided into a reception filtering area and a transmission filtering area. In this structure, the dielectric block
10
includes first and second surfaces
11
and
13
opposing to each other, a side surface
13
disposed between the first and second surfaces
11
and
13
. The second surface
13
and the side surface
13
, i.e., the back surface and the side surface of the dielectric block
10
are substantially covered with the the conductive materials. Furthermore, a plurality of resonant holes
30
a
-
30
g
for penetrating the first and second surfaces
11
and
13
are arranged in parallel at predetermined distances from one another in the interior of the dielectric block
10
. Each of the plurality of resonant holes
30
a
-
30
g
is substantially covered with the conductive materials on the internal surface to thereby form a resonator.
A plurality of conductive patterns
31
a
-
31
g
having predetermined size are disposed on the first surface
11
of the dielectric block
10
. Each of the conductive patterns
31
a
-
31
g
is connected to the conductive material covered on the interior of each resonant hole
30
a
-
30
g
to apply a loading capacitance to each resonator and simultaneously to form coupling capacitance between the adjacent resonators. A resonant frequency of the resonator is determined upon the plurality of resonant holes
30
a
-
30
g
and the applied loading capacitance, and the coupling of two resonators is achieved by the formation of the coupling capacitance. In addition, input and output terminals
21
and
23
made of a conductive pattern
1
are disposed in the both of the first surface
11
and an antenna terminal
22
made of the conductive pattern is disposed between the reception filtering area and the transmission filtering area.
Typically, the duplexer dielectric filter has a high frequency band of the transmission filtering area relatively lower than that of the reception filtering area. Therefore, an electric field effect is predominent between the resonant holes in the reception filtering area, while a magnetic field effect is predominant between the resonant holes in the transmission filtering area. Hence, the resonant holes disposed on the reception filtering area are in a capacitance coupling relationship, and the resonant holes in the transmission filtering area are in an inductance coupling relationship.
In the above construction, determination of the resonant frequency or coupling between the resonators is dependent upon the size of the plurality of conductive patterns
31
a
to
31
g
on the first surface
11
. In other words, the characteristic of the duplexer dielectric filter is dependent upon the intervals between the conductive patterns
31
a
to
31
g
and the conductive material of the side surface
12
and between the conductive patterns
31
a
to
31
g.
To produce a small and light duplexer dielectric filter, meanwhile, the duplexer dielectric filter should be thin in thickness and the interval between the resonant holes
30
a
to
30
g
should be short in length. Since the dimension of the first surface
11
may be reduced in the miniature filter, however, there are problem that a desired attenuation characteristic can not be obtained due to limitations on the intervals between the conductive patterns
31
a
to
31
g
and the conductive material on the side surface
12
of the dielectric block
10
and between the conductive patterns
31
a
to
31
g.
On the other hand, if the size of the dielectric block
10
is designed to be small, even in the case where the intervals between the conductive patterns
31
a
to
31
g
and the conductive material of the side surface
12
thereof and between the conductive patterns
31
a
to
31
g
are established to be short, it is impossible to reduce the volume of the dielectric block
10
in the certain limitation because of the error caused by the limitation of the printing process.
Moreover, in the case where the resonant frequency is adjusted by varying the shape of the conductive patterns
31
a
to
31
g
, since the coupling capacitance and the loading capacitance are simultaneously changed, there is a problem that the passing and stopping features for the frequency signal are indicated in an irregular order. Furthermore, there remains a problem in that since the adjusting operation of the resonant frequency is not automatic, a labour cost in the production process should be high, to thereby decrease competitiveness of the production cost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a duplexer dielectric filter having predetermined conductive patterns on a first surface of a dielectric block thereof to form a loading capacitance to a resonator, form a coupling capacitance between the adjacent resonators, and form a cross coupling capacitance between the resonator not being adjacent, whereby the duplexer dielectric filter can be small and light and be manufactured in an simplified process.
Another object of the present invention is to provide a duplexer dielectric filter having a conductive pattern for use in adjusting a resonant frequency of a resonator on a first surface of a dielectric block thereof, thus to adjust accurately a resonant frequency band to a desired band in an accurate manner.
To achieve these and other objects according to the present invention, there is provided a duplexer dielectric filter including: a dielectric block comprised of first and second surfaces opposing to each other and a side surface disposed between the first and second surfaces, the second and side surfaces being substantially covered with a conductive material; a first filtering area comprised of at least one resonator having at least one resonant hole which is disposed to pass through the first and second surfaces of the dielectric block in a substantially parallel manner and is substantially covered with the conductive material on the interior thereof and for filtering a first input signal; a second filtering area comprised of at least one resonator having at least one resonant hole which is disposed to pass through the first and second surfaces of the dielectric block in a parallel manner and is substantially covered with the conductive material on the interior thereof and for filtering a second input signal; at least one first conductive pattern formed to have a predetermined size on the surroundings of the at least one resonant hole of the first surface on which the first and second filtering areas are occupied, thus to be connected with the conductive material covered with the interior of the at least one resonant hole and for applying a loading capacitance to the at l

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