Dielectric duplexer and communication apparatus

Details Dielectric duplexer and communication apparatus Dielectric duplexer and communication apparatus

2002-10-22

2004-06-08

Summons, Barbara (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S127000, C333S134000, C333S203000, C333S206000

Reexamination Certificate

active

06747527

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dielectric duplexers mainly for use in mobile communication, to radio frequency (RF) modules, and to communication apparatuses including the same.
2. Description of the Related Art
Referring to
FIG. 7
, the configuration of a known dielectric duplexer will now be described.
FIG. 7
is an external perspective view of a dielectric duplexer.
Referring to
FIG. 7
, the dielectric duplexer includes a dielectric block
51
, inner-conductor-formed holes
52
a
to
52
f
, containing inner conductors
53
a
to
53
f
, an outer conductor
54
, an input/output electrode
55
, outer-conductorless portions
56
and
58
, an antenna input/output electrode
57
, and an inner-conductor-formed hole
59
functioning as an antenna excitation hole.
The substantially-rectangular-parallelepiped-shaped dielectric block
51
includes the inner-conductor-formed holes
52
a
to
52
f
, containing the inner conductors
53
a
to
53
f
, respectively. The outer conductor
54
is formed on the entirety of an exterior surface of the dielectric block
51
. In the interior near an end face having first ends of the inner-conductor-formed holes
52
a
to
52
f
(the right back side in FIG.
7
), inner-conductorless portions are provided to isolate the inner conductors
53
a
to
53
f
from the outer conductor
54
, and hence the first ends become open-circuited ends. Second ends opposing the open-circuited ends (the left front side in
FIG. 7
) are short-circuited ends. As a result, dielectric resonators are formed. The inner-conductor-formed hole
59
is formed to penetrate the dielectric block
51
in the same axial direction as that of the inner-conductor-formed holes
52
a
to
52
f.
On the exterior surface of the dielectric block
51
, the input/output terminal
55
extends from an end face in the direction in which the inner-conductor-formed holes
52
a
to
52
f
are arrayed to a mounting face (bottom face in
FIG. 7
) opposing a mounting board. The input/output terminal
55
is separated from the outer conductor
54
by the outer-conductorless portion
56
therebetween. Between the inner-conductor-formed holes
52
c
and
52
d
, the antenna input/output electrode
57
is formed to extend from the short-circuited end face having the short-circuited ends of the inner-conductor-formed holes
52
a
to
52
f
to the mounting face. The antenna input/output electrode
57
is separated from the outer conductor
54
by the outer-conductorless portion
58
therebetween. The antenna input/output electrode
57
is connected to an inner conductor in the inner-conductor-formed hole
59
.
In this state, a first portion including the inner-conductor-formed holes
52
a
to
52
c
and a second portion including the inner-conductor-formed holes
52
d
to
52
f
each function as a three-stage band-pass-type dielectric filer in which the resonators formed by the inner conductors are coupled to one another. Thus, the dielectric duplexer having one of the filters as a transmitter filter and the other filter as a receiver filter is formed.
The above-described known dielectric duplexer has the following problems.
In the known dielectric duplexer, when the transmitter filter and the receiver filter are both band pass filters, the impedance in each of the pass bands of the transmitter filter and the receiver filter as seen from the antenna input/output electrode is substantially infinite. Thus, the transmitter filter and the receiver filter function as a dielectric duplexer.
FIG. 8
shows the equivalent circuit of a dielectric duplexer in which one of the filters is a band eliminate filter. In this case, as shown in
FIG. 9
, the impedance of the band eliminate filter in the pass band of the band pass filter is substantially zero.
FIG. 9
is a Smith chart showing the impedance of the transmitter filter (band eliminate filter) as seen from the antenna in the reception band (pass band) of the receiver filter (band pass filter). The Smith chart shows the impedance of a communication system in the 800 MHz band (the pass band of the receiver filter ranges from 810 MHz to 828 MHz), wherein symbol A indicates the impedance at 810 MHz and symbol B indicates the impedance at 828 MHz.
As shown in
FIG. 9
, the impedance of the transmitter filter as seen from the antenna is substantially zero, and hence the transmitter filter as seen from the antenna is essentially short-circuited in the reception band. This causes a reception signal from the antenna to enter the transmitter filter. As a result, the transmitter filter and the receiver filter do not function as a duplexer.
In order to solve this problem, a dielectric duplexer arranged as shown in
FIGS. 10A
to
10
C is devised.
FIGS. 10A
to
10
C are three partial views of the dielectric duplexer, namely,
FIGS. 10A and 10C
illustrating faces having apertures of inner-conductor-formed holes and
FIG. 10B
illustrating the bottom face, which is a mounting face.
FIGS. 10A
to
10
C show a band eliminate filter, which is one of the filters forming the dielectric duplexer.
Referring to
FIGS. 10A
to
10
C, the dielectric duplexer includes a dielectric block
61
, inner-conductor-formed holes
62
a
to
62
d
,
70
, and
71
, an outer conductor
64
, outer-conductorless portions
66
and
68
, an input/output electrode
67
, and an antenna input/output electrode
69
.
In the dielectric duplexer shown in
FIGS. 10A
to
10
C, the inner-conductor-formed holes
62
a
to
62
d
,
70
, and
71
, containing inner conductors, are formed to extend from a first face of the dielectric block
61
(
FIG. 10A
) to a second face opposing the first face (FIG.
10
C). The inner-conductor-formed holes
62
a
,
62
c
,
62
d
,
70
, and
71
each have a stepped structure formed by portions having different internal diameters. The inner-conductor-formed hole
62
b
has a straight structure. The outer conductor
64
is formed on the substantial entirety of an exterior surface of the dielectric block
61
. The outer-conductorless portions
66
and
68
are provided to extend from the first face (
FIG. 10A
) to the bottom face, which is the mounting face (FIG.
10
B). This results in the formation of the input/output electrode
67
and the antenna input/output electrode
69
. The inner-conductor-formed holes
70
and
71
are connected to the input/output electrode
67
and the antenna input/output electrode
69
, respectively. An inner-conductorless portion is provided in the interior near the first face (
FIG. 10A
) including the input/output electrode
67
and the antenna input/output electrode
69
, and hence an open-circuited end of a resonator formed by the inner-conductor-formed hole
62
c
is formed. Inner-conductorless portions are provided in the interior near the second face opposing the first face (FIG.
10
C), and hence open-circuited ends of resonators formed by the inner-conductor-formed holes
62
a
and
62
d
are formed.
The inner-conductor-formed holes
62
a
to
62
d
,
70
, and
71
are arranged in two lines from the bottom face to the top face of the dielectric block
61
. The resonators formed by the inner-conductor-formed holes
62
a
,
70
,
62
c
, and
62
d
form two one-stage band eliminate filters by interdigitally coupling the inner-conductor-formed hole
62
a
with the inner-conductor-formed hole
70
and by interdigitally coupling the inner-conductor-formed hole
62
c
with the inner-conductor-formed hole
62
d
. The one-stage band eliminate filters are interdigitally coupled to each other at an electrical angle of &pgr;/2 between the inner-conductor-formed hole
70
and the inner-conductor-formed hole
62
d
. As a result, a two-stage band eliminate filter is formed.
The resonator formed by the inner-conductor-formed hole
71
functions as a &pgr;/2 phase circuit by interdigitally coupling to the resonator formed by the inner-conductor-formed hole
62
d
at an electrical angle of &pgr;/2. The band eliminated by the band eliminate filter, as seen from the antenna input/output electrode
69
, i.e.,

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