Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
2001-09-12
2003-09-02
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200
Reexamination Certificate
active
06614324
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a center electrode assembly and a nonreciprocal circuit device which may constitute an isolator or a circulator for use in, for example, a microwave band, and relates to a communication apparatus including this nonreciprocal device.
2. Description of the Related Art
A center electrode assembly shown in
FIGS. 30A and 30B
is known for use in a concentrated-constant type isolator (nonreciprocal circuit device) adopted in mobile communication equipment such as mobile telephones. This center electrode assembly
200
is formed by wrapping a disk shaped microwave ferrite
201
in an electrode assembly
210
including three center electrodes
211
,
212
, and
213
.
The electrode assembly
210
is formed by extending outward the center electrodes
211
,
212
, and
213
at predetermined angles from the center planar portion (ground electrode)
215
. The center electrodes
211
and
212
are formed of one line, while the center electrode
213
is formed of two lines. In assembly, firstly the center planar portion
215
is abutted against the bottom surface of the ferrite
201
, then the center electrodes
211
,
212
, and
213
are wrapped around the top surface of the ferrite
201
across the side surface thereof (by making folded portions marked “a” and “b”), and these center electrodes are crossed with one another at predetermined crossing angles, on the top surface of the ferrite
201
.
A nonreciprocal circuit device having this type of center electrode assembly
200
is mainly used in mobile communication equipment, and significant progress is being made in miniaturizing it. Since the electrode assembly
210
requires more miniaturization, the line width of each of the center electrodes
211
,
212
, and
213
is being made smaller. Such center electrodes are formed by press work using a mold or by etching work, but there are limits to the working accuracy available. It is, therefore, difficult to form all center electrodes so as to have two lines, and currently, at least one of them is generally formed of one line.
FIG. 31
shows another conventional center electrode assembly. In this center electrode assembly
240
, an input center electrode
271
, an output center electrode
272
, and a terminal center electrode
273
are arranged on the top surface of a microwave ferrite
270
with insulating sheets
220
interposed between them so that the crossing angle G formed among mutually crossing center lines thereof becomes about 120°. First ends of the center electrodes
271
,
272
, and
273
are electrically connected to port portions P
1
, P
2
, and P
3
, respectively. The other ends of the center electrodes
271
,
272
, and
273
extend across the side surface of the ferrite
270
, and are electrically connected to ground electrode
276
provided on the bottom surface of the ferrite
270
. The ground electrode
276
covers substantially the entire bottom surface of the ferrite
270
.
In a center electrode assembly incorporated into a concentrated-constant type nonreciprocal circuit device, if the crossing angle formed among three center electrodes varies, it will significantly influence the electrical characteristics thereof such as the insertion loss and the isolation. It is, therefore, very important to ensure the stabilization of the crossing angle.
However, in the conventional center electrode assembly
200
shown in
FIGS. 30A and 30B
, since each of the center electrodes has a small line width, there is the risk that a line may break due to vibration and heating during assembly or during operation of communication equipment in which the center electrode assembly is incorporated. Such line breakage occurs especially at folded portions “a” and/or “b”. In particular, the line breakage of a center electrode formed of one line could cause a critical defect.
As indices of the performance of an isolator, there are insertion loss and isolation. The lower the insertion loss, the better the isolator. The wider the isolation bandwidth, the better the isolation characteristic. In
FIG. 32
, there is shown the relationship between the insertion loss
280
and the isolation characteristic
282
of the isolator in which the above-described center electrode assembly
240
, of which the crossing angle G is 120°, is incorporated (see the dotted lines).
Now, as a method for improving the insertion loss, it is known to increase the crossing angle G formed between the input center electrode
271
and the output center electrode
272
. For example, in
FIG. 32
, there is shown the relationship between the insertion loss
281
and the isolation characteristic
283
of the isolator incorporating the above-described center electrode assembly
240
when the crossing angle G is changed to 125° (see the solid lines). However, although this method can improve the insertion loss, this method reduces the isolation bandwidth, and is prone to increase the fraction of defective manufactured parts due to variations in characteristics among production lots of the center electrode assembly
240
.
Furthermore, enlarging the crossing angle formed between the input center electrode
271
and the output center electrode
272
reduces the distance A-A′ from the intersection point A (see
FIG. 31
) of the edge of the input center electrode
271
and that of the output center electrode
272
to the edges of the insulating sheets
220
. As a result, if the insulating sheets
220
are displaced to the position
220
a
indicated by the two-dot chain line
220
a
, short-circuit failures are prone to occur between the input center electrode
271
and the output center electrode
272
.
SUMMARY OF THE INVENTION
The present invention provides a center electrode assembly and a nonreciprocal circuit device, and a communication apparatus incorporating them, which have stable physical properties and high reliability, and which eliminate the risk of line breakage of the center electrodes thereof.
The present invention also provides a center electrode assembly and a nonreciprocal circuit device, and a communication apparatus incorporating them, which have improved the insertion loss without impairing other electrical characteristics, and which are less likely to have short-circuit failures.
In order to provide the foregoing, the present invention, in a first aspect, provides a center electrode assembly comprising an electrode assembly wherein a plurality of center electrodes extends outward from the center planar portion thereof at a predetermined angular distance; and a ferrite. In this center electrode assembly, the center planar portion is abutted against the bottom surface of the ferrite, then the center electrodes are wrapped around the top surface of the ferrite across the side surface thereof, and the center electrodes are crossed with each other on the top surface of the ferrite. At least one center electrode is formed of one line, and the line width of the above-mentioned center electrode is enlarged where it crosses the side surface of the ferrite near the center planar portion.
The present invention, in a second aspect, provides a center electrode assembly comprising an electrode assembly wherein a plurality of center electrodes extends outward from the center planar portion thereof at a predetermined angular distance; and a ferrite. In this center electrode assembly, the center planar portion is abutted against the bottom surface of the ferrite, then the center electrodes are wrapped around the top surface of the ferrite across the side surface thereof, and the center electrodes are crossed with each other on the top surface of the ferrite. At least one center electrode is formed of one line, and the line width of the above-mentioned center electrode is larger near the ferrite edge than near the ferrite center.
In the center electrode assembly in accordance with the first and second aspects, the ferrite is wrapped in the center electrodes by folding the center electrodes at the ferrite edge portions thereof near the center
Hasegawa Takashi
Ohira Katsuyuki
Jones Stephen E.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Pascal Robert
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