Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2002-04-08
2003-06-17
Ham, Seungsook (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S206000
Reexamination Certificate
active
06580339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to integral-type dielectric duplexers using dielectric blocks, which are provided in mobile communication devices, and to communication apparatuses which include the same.
2. Description of the Related Art
Referring to
FIG. 11
, the structure of a known dielectric duplexer will now be described.
A substantially-rectangular-parallelepiped-shaped dielectric block
1
includes a plurality of plated through holes
2
a
to
2
f
containing inner conductors
3
a
to
3
f
, respectively. The inner conductors on the plated through holes define respective resonant cavities. An outer conductor
4
is formed on substantially the entire exterior surface of the dielectric block
1
. In the vicinity of first ends of the plated through holes
2
a
to
2
f
(the right back side of the plated through holes as viewed in FIG.
11
), inner-conductorless portions
33
a
to
33
f
are provided, thus forming open ends of the resonant cavities. Second ends (the left front side as viewed in
FIG. 11
) of the plated through holes are short-circuit ends which are directly coupled to the outer conductor
4
. The face of the dielectric block located adjacent the short-circuit ends of the resonant cavities will be referred to as the short-circuit end face of the duplexer. In accordance with this structure a plurality of dielectric resonators are formed.
An input/output terminal
5
extends from a right side face of the dielectric block to a mounting surface (the bottom face in
FIG. 11
) of the dielectric block
1
which is opposed to a mounting board. The input/output terminal
5
is separated from the outer conductor
4
by an outer-conductorless portion
6
located therebetween. Although not shown in
FIG. 11
, a second input/output terminal is preferably formed extending from a left side face (opposite the right side face) to the bottom mounting surfaces. An antenna terminal
7
is formed between the plated through holes
2
c
and
2
d
and is separated from the outer conductor
4
by an outer-conductorless portion
8
. The antenna terminal
7
extends from the short-circuit end face to the mounting surface. An antenna excitation hole
9
is formed as a through-hole in the same axial direction as that of the plated through holes
2
a
to
2
f
in the dielectric block
1
. An electrode is formed on the inner surface of the antenna excitation hole
9
and is electronically coupled to the antenna terminal
7
.
A first portion of the duplexer containing plated through holes
2
a
to
2
c
and a second portion of the duplexer containing the inner-conductor-formed holes
2
d
to
2
f
each function as a three-stage dielectric filer in which the resonant cavities formed by the inner conductors of the plated through holes are coupled to one another. The first portion is typically regarded as a transmitter filter and the second portion is typically regarded as a receiver filter.
The above-described known dielectric duplexer has the following problems.
FIG. 12
illustrates an enlarged section of the duplexer of
FIG. 11
showing the distribution of ground current on a portion of the short-circuit end face thereof.
FIG. 12
shows the plated through holes
2
d
and
2
e
, the inner conductors
3
d
and
3
e
, the outer conductor
4
, the antenna terminal
7
, the outer-conductorless portion
8
, the antenna excitation hole
9
, a top electrode
10
, which is part of the outer conductor, and a bottom electrode
11
, which is also part of the outer conductor.
In response to a signal input to the dielectric duplexer, current flows from the inner electrodes to the outer conductor, which acts as a ground electrode. As shown in
FIG. 12
the current flowing from the inner conductor
3
e
to the top electrode
10
is substantially equal to the current flowing from the inner conductor
3
e
to the bottom mounting electrode
11
. As a result, there is substantially no potential difference between the top electrode
10
and the bottom electrode
11
in the area of the plated through hole
2
e
, and a TE (transverse electric) mode having an electric field component perpendicular to the top electrode
10
and the bottom electrode
11
is not excited.
In contrast, such a mode is excited in the area of the plated through hole
2
d
because of the presence of the outer-conductorless portion
8
which is provided on the short-circuit end face and the bottom mounting surface of the dielectric block, but not on the top surface thereof A current flowing from the inner conductor
3
d
adjacent to the antenna terminal
7
to the top electrode
10
is greater than a current flowing from the inner conductor
3
d
to the bottom electrode
11
. Thus, a potential difference is generated between the top electrode
10
and the bottom electrode
11
, and hence an electric field is generated. Accordingly, the TE mode having an electric field component perpendicular to the top electrode
10
and the bottom electrode
11
is excited.
Generally in a duplexer, the attenuation band of a transmitter filter is the pass band of a receiver filter, and the attenuation band of the receiver filter is the pass band of the transmitter filter. When a resonator forming the receiver filter, particularly a resonator adjacent to an antenna excitation hole, excites a TE mode in the pass band of the receiver filter, part of a transmission signal passing through the transmitter filter couples with the resonator forming the receiver filter, and the coupled signal is transmitted to the antenna excitation hole. Thus, the attenuation characteristic of the transmitter filter deteriorates significantly. In contrast, when a resonator forming the transmitter filter, particularly a resonator adjacent to the antenna excitation hole, excites the TE mode in the pass band of the transmitter filter, the attenuation characteristic of the receiver filter deteriorates significantly.
When a wave in a TE mode propagates between the transmitter filter and the receiver filter, the attenuation characteristics deteriorate.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a dielectric duplexer which has a simple structure having improved attenuation characteristics by reducing the excitation of undesirable modes in which a wave propagates between filters and to provide a communication apparatus using the same.
According to an aspect of the present invention, a dielectric duplexer comprises:
a dielectric block having an outer surface including top, bottom, front and rear surfaces;
a plurality of plated through holes extending through the dielectric block between the front to the rear surfaces thereof, each of the plated through holes having a respective inner conductor formed on an inner surface thereof;
an antenna excitation hole extending through the dielectric block from the front to the rear surface thereof, the antenna excitation hole having an electrode formed on an inner surface thereof;
an outer conductor located on the outer surface of the dielectric block and being directly connected to the inner conductors at the front surface of the dielectric block;
input/output terminals located on the outer surface of the dielectric block and being spaced from the outer conductor;
an antenna terminal located on the front surface and being directly coupled to the antenna excitation hole electrode, the antenna terminal being separated from the outer conductor by a conductorless area extending from the front to the bottom surfaces of the dielectric block; and
means for adjusting the relative flow of current through the outer conductor between the inner electrode of a first one of the plated through holes which is located adjacent the antenna terminal and the upper and lower surfaces of the dielectric block so as to cause the two current flows to be substantially equal.
The adjusting means may include at least one electrodeless portion formed on the outer conductor located on the front face of the dielectric block and located adjacent the antenna excitation hole. The emb
Dickstein Shapiro Morin & Oshinsky LLP.
Ham Seungsook
Murata Manufacturing Co. Ltd
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