Multilayered LC filter

Details Multilayered LC filter Multilayered LC filter

2001-08-23

2003-03-04

Ham, Seungsook (Department: 2817)

Wave transmission lines and networks

Coupling networks

Frequency domain filters utilizing only lumped parameters

C333S185000, C333S177000

Reexamination Certificate

active

06529101

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multilayered LC filters, and more specifically, to a multilayered LC filter for use in a mobile communication devices such as a cellular phone.
2. Description of the Related Art
As an example of such a multilayered LC filter,
FIG. 8
shows the construction of a conventional multilayered LC filter
1
. The multilayered LC filter
1
includes a laminated body
2
composed of laminated insulating sheets, and within the laminated body
2
, inductors L
1
and L
2
defined by inductor via holes provided in ceramic sheets and connected to each other, and capacitors C
1
and C
2
that are defined by hot-side capacitor patterns
3
and
4
and a ground-side capacitor pattern
7
.
One end of the inductor L
1
is electrically connected to an external ground electrode G
1
via an internal ground pattern
5
, and the other end thereof is electrically connected to the hot-side capacitor pattern
3
. Similarly, one end of the inductor L
2
is electrically connected to an external ground electrode G
2
, provided on the surface of the laminated body
2
, via an internal ground pattern
6
, and the other end thereof is electrically connected to the hot-side capacitor pattern
4
. The hot-side capacitor patterns
3
and
4
are electrically connected respectively to an external input electrode and an external output electrode (not shown) provided on the surface of the laminated body
2
.
In the multilayered LC filter
1
, the inductor L
1
and the capacitor C
1
define an LC resonator Q
1
. Similarly, the inductor L
2
and the capacitor C
2
define an LC resonator Q
2
. Because the internal ground patterns
5
and
6
are electrically separated, the ground sides of the two LC resonators Q
1
and Q
2
are not combine-coupled, but instead are electrically independent of each other. Thus, the coupling between the resonators Q
1
and Q
2
is capacitive and weak, with the value of the equivalent magnetic coupling being 0.1 or smaller.
As another example,
FIG. 9
shows the construction of another conventional multilayered LC filter
11
. The multilayered LC filter
11
includes a laminated body
12
including laminated ceramic sheets, and within the laminated body
12
, inductors L
1
and L
2
are defined by inductor via holes provided on insulating sheets and connected to each other, and capacitors C
1
and C
2
are defined by hot-side capacitor patterns
13
and
14
and a ground-side capacitor pattern
16
.
First ends of the inductor L
1
and the inductor L
2
are electrically connected respectively to external ground electrodes G
1
and G
2
via an internal ground pattern
15
, and second ends thereof are electrically connected respectively to the hot-side capacitor patterns
13
and
14
. The hot-side capacitor patterns
13
and
14
are electrically connected respectively to an external input electrode and an external output electrode (not shown) provided on the surface of the laminated body
12
.
In the multilayered LC filter
11
, the inductor L
1
and the capacitor C
1
define an LC resonator Q
1
. Similarly, the inductor L
2
and the capacitor C
2
define an LC resonator Q
2
. The ground sides of the two resonators Q
1
and Q
2
are combine-coupled via an internal ground pattern
15
, thus being electrically short-circuited. Thus, the coupling between the LC resonators Q
1
and Q
2
is inductive and strong, with the value of the equivalent magnetic coupling being 0.2 or larger.
However, although the conventional multilayered LC filters
1
and
11
can provide a value of the magnetic coupling between the LC resonators Q
1
and Q
2
of 0.1 or smaller, or 0.2 or larger, they fail to provide a value of the magnetic coupling between 0.1 and 0.2. It is known that, for example, in the multilayered LC filter
1
shown in
FIG. 8
, the value of the magnetic coupling between the LC resonators Q
1
and Q
2
can be adjusted by changing the distance between the inductors L
1
and L
2
. However, this method of adjusting the value of the magnetic coupling by changing the distance between the inductors L
1
and L
2
does not allow for selecting an arbitrary value of the magnetic coupling due to restrictions of the product size, and other limitations. For example, the distance between the inductors L
1
and L
2
may be shortened to a certain extent to adjust the value of the magnetic coupling between the LC resonators Q
1
and Q
2
. However, when the inductors L
1
and L
2
come too close to each other, problems may occur in the manufacturing process. For example, the ceramic material between the inductors L
1
and L
2
may crack at the time of firing.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a multi-layered LC filter which allows adjustment of the value of the magnetic coupling between LC resonators without changing the size of the filter.
According to a preferred embodiment of the present invention, a multi-layered LC filter includes a laminated body having a plurality of insulating layers that are stacked on each other. In the laminated body, a plurality of LC resonators including a plurality of inductors and a plurality of capacitors is provided. The multi-layered LC filter includes a plurality of via holes connected to each other in the lamination or stacking direction of the plurality of insulating layers, and a plurality of external ground electrodes provided on a surface of the laminated body, to which first ends of the plurality of inductors are electrically connected individually, and a bridge pattern disposed on a surface of one of the plurality of insulating layers and in proximity to the plurality of inductors, electrically connecting the plurality of external ground electrodes.
In accordance with another preferred embodiment of the present invention, a multi-layered LC filter includes a laminated body having a plurality of insulating layers stacked on each other. In the laminated body, a plurality of LC resonators having a plurality of inductors and a plurality of capacitors is provided. The multi-layered LC filter includes a first insulating layer on which segmented internal ground patterns are provided, a second insulating layer on which a plurality of inductor via holes and a bridge pattern in proximity to the plurality of inductor via holes are provided, a third insulating layer on which a plurality of inductor via holes is provided, a fourth insulating layer on which a plurality of hot-side capacitor patterns is provided, a fifth insulating layer on which a ground-side capacitor pattern is provided opposing the plurality of hot-side capacitor patterns, so as to form the plurality of capacitors of the plurality of LC resonators, and an external input electrode, an external output electrode, and a plurality of external ground electrodes provided on a surface of the laminated body which includes first to fifth insulating layers laminated. In the multilayered LC filter, the plurality of inductor via holes provided in the second insulating layer and the plurality of inductor via holes provided in the third insulating layer are connected to each other in the lamination direction of the plurality of insulating layers. First ends of the plurality of inductors are electrically connected to the plurality of hot-side capacitor patterns of the plurality of capacitors, and second ends thereof are electrically connected to the plurality of external ground electrodes via the internal ground patterns provided on the first insulating layer. The ends of the bridge pattern provided on the second insulating layer are electrically connected respectively to the plurality of external ground electrodes, and the bridge pattern is disposed in proximity to the plurality of inductors including the plurality of via holes.
The plurality of inductors primarily includes the plurality of via holes connected with each other. Although, for example, the internal ground patterns have respective inductive elements, the primary inductive elements of

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