Duplexer having laminated structure

Details Duplexer having laminated structure Duplexer having laminated structure

2000-12-11

2002-07-02

Pascal, Robert (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S185000

Reexamination Certificate

active

06414567

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a duplexer for use in communication systems such as microwave communication systems, and more particularly, to a duplexer having a laminated structure.
2. Description of the Related Art
A conventional laminated type duplexer is shown in
FIGS. 4 and 5
. Referring first to
FIG. 4
, a laminated duplexer
1
includes a laminated structure defined by ceramic sheets
2
to
9
. Inductor patterns
12
to
17
are provided on a surface of the ceramic sheet
6
. Frequency-adjusting capacitor patterns
18
to
23
are provided on a surface of the ceramic sheet
7
. Coupling-adjusting capacitor patterns
24
to
27
are provided on a surface of the ceramic sheet
5
. Shield patterns
28
a
and
29
a
are provided on a surface of the ceramic sheet
3
, and shield patterns
28
b
and
29
b
are provided on a surface of the ceramic sheet
9
.
The duplexer
1
includes a three-stage band-pass filter BPF
1
having LC resonators Q
1
to Q
3
at the left as viewed in
FIG. 4
, and a three-stage band-pass filter BPF
2
having LC resonators Q
4
to Q
6
at the right as viewed in FIG.
4
. The inductor patterns
12
to
17
define inductors L
1
to L
6
of the LC resonators Q
1
to Q
6
, respectively. The frequency-adjusting capacitor patterns
18
to
23
and the ends of the inductor patterns
12
to
17
which face the frequency-adjusting capacitor patterns
18
to
23
define capacitors Cl to C
6
of the LC resonators Q
1
to Q
6
, respectively.
The LC resonators Q
1
to Q
3
of the band-pass filter BPF
1
are electrically connected to coupling capacitors Cs
1
and Cs
2
(not shown in FIGS.
4
and
5
). The coupling and adjusting capacitors Cs
1
and Cs
2
are defined by the inductor patterns
12
to
14
and coupling-adjusting capacitor patterns
24
and
25
, which face these inductor patterns
12
to
14
. The shield patterns
28
a
and
28
b
are arranged such that the patterns
12
to
14
,
18
to
20
,
24
and
25
are positioned therebetween.
Likewise, the LC resonators Q
4
to Q
6
of the band-pass filter BPF
2
are electrically connected to coupling capacitors Cs
3
and Cs
4
(not shown). The coupling capacitors Cs
3
and Cs
4
are defined by the inductor patterns
15
to
17
and coupling-adjusting capacitor patterns
26
and
27
, which face the inductor patterns
15
to
17
. The shield patterns
29
a
and
29
b
are arranged such that the patterns
15
to
17
,
21
to
23
,
26
and
27
are positioned therebetween.
The ceramic sheets
2
to
9
are laminated, and are integrally fired to define a laminate
35
shown in FIG.
5
. The laminate
35
is provided with a transmitter terminal electrode Tx, a receiver terminal electrode Rx, an antenna terminal electrode ANT, and grounding terminal electrodes G
1
to G
4
. The inductor pattern
12
of the LC resonator Q
1
is connected to the transmitter terminal electrode Tx, and the inductor pattern
17
of the LC resonator Q
6
is connected to the receiver terminal electrode Rx. The inductor patterns
14
and
15
of the LC resonators Q
3
and Q
4
are connected to the antenna terminal electrode ANT. The grounding terminal electrode G
1
is connected to one end of each of the inductor patterns
12
to
14
, and the grounding terminal electrode G
2
is connected to one end of each of the frequency-adjusting capacitor patterns
18
to
20
in the LC resonators Q
1
to Q
3
. The grounding terminal electrodes G
1
and G
2
are also connected with the shield patterns
28
a
and
28
b
. The grounding terminal electrode G
3
is connected to one end of each of the inductor patterns
15
to
17
, and the grounding terminal electrode G
4
is connected to one end of each of the frequency-adjusting capacitor patterns
21
to
23
of the LC resonators Q
4
to Q
6
. The grounding terminal electrodes G
3
and G
4
are also connected with the shield patterns
29
a
and
29
b.
In general, duplexers have characteristics that depend upon the Q factor of inductors of LC resonators. The Q factor of an inductor is expressed by Q=2&pgr;f
0
L/R, where L represents the inductance of the inductor, R represents the resistance of the inductor, and f
0
represents the resonant frequency. From the equation, it is clear that the resistance R should be reduced to increase the Q factor of the inductor. The resistance R is inversely proportional to the cross-sectional area S of an inductor pattern that is used to define the inductor. To increase the Q factor of the inductor, therefore, the cross-sectional area S of the inductor patterns
12
to
17
must be increased.
However, increasing the thickness of the inductor patterns
12
to
17
to increase the cross-section S of the inductor patterns
12
to
17
produces undesirable results. Specifically, an internal strain of the laminate
35
is increased causing delamination when the ceramic sheets
2
to
9
are integrally fired. Furthermore, if pattern widths of the inductor patterns
12
to
17
are increased to increase the cross-section S of the inductor patterns
12
to
17
, the LC resonators Q
1
to Q
6
is greatly increased.
The axial directions of the inductors L
1
to L
6
of the LC resonators Q
1
to Q
6
are perpendicular to the stacking direction of the ceramic sheets
2
to
9
. When an electric current flows through the inductors L
1
to L
6
, a magnetic flux &phgr; is generated so as to surround the inductors L
1
to L
6
on planes perpendicular to the axial directions of the inductors L
1
to L
6
. However, since the inductors L
1
to L
6
and the patterns
18
to
23
,
24
to
27
,
28
a
,
28
b
,
29
a
and
29
b
are arranged in parallel, the magnetic flux &phgr;passes through the patterns
18
to
23
,
24
to
27
,
28
a
,
28
b
,
29
a
and
29
b
, so that eddy currents are generated in the patterns
18
to
23
,
24
to
27
,
28
a
,
28
b
,
29
a
and
29
b
. This produces inductors L
1
to L
6
that have very low Q factors.
SUMMARY OF THE INVENTION
To overcome the above-described problems, preferred embodiments of the present invention provide a laminated-type duplexer which is compact and which has inductors with very high Q factors.
To this end, preferred embodiments of the present invention include a laminated type duplexer having insulator layers which are laminated to define a laminate including a plurality of filters embedded therein, each of the filters having an inductor and a capacitor, wherein each inductor includes a via hole or via-holes connected in sequence in the stacking direction of the insulator layers, and at least two adjacent filters of the plurality of filters are electrically connected to each other through a matching inductor pattern.
Since the inductor is defined by the via-holes connected in sequence, increasing the cross-section of each via-hole or increasing the number of via-holes results in increased cross-sectional area of the inductor. This improves the Q factor of the inductor without increasing the thickness or width of inductor patterns in conventional technique.
When an electric current flows through the inductor, magnetic flux is generated to surround the inductor on a plane that is substantially perpendicular to the axial direction of the inductor. However, since the inductor is substantially perpendicular to a capacitor pattern and a shield pattern, the generated magnetic flux does not pass through such patterns, so that no eddy current occurs in such patterns. This results in an inductor having a very high Q factor and reduced eddy current loss.
Other features, elements, characteristics and advantages of present invention will become apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.


REFERENCES:
patent: 5029043 (1991-07-01), Kitahara et al.
patent: 5719539 (1998-02-01), Ishizaki et al.
patent: 6011959 (2000-01-01), Reeser et al.
patent: 2303495 (1997-02-01), None
patent: 6-85506 (1994-03-01), None

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