Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1998-03-25
2002-05-14
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S202000, C333S219100
Reexamination Certificate
active
06388541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric resonator, a dielectric filter, a sharing device, and a communication apparatus which are used in a microwave band, a millimeter wave band, or the like.
2. Description of the Related Art
In recent years, a communication system achieving a large capacity and a high speed has been required in accordance with a rapid increase in demand of a mobile communication system or multimedia systems. With such an increase in amount of information to be communicated, a use frequency band has been extended from a microwave band to a millimeter wave band. Even in the millimeter wave band, a TE01&dgr; mode dielectric resonator constituted by a conventionally known cylindrical dielectric material can be used in a manner in the microwave band. At this time, severe processing precision is required because the resonance frequency of the TE01&dgr; mode dielectric resonator is determined depending on the external size of the cylindrical dielectric material. However, a precise size cannot be set with respect to the resonance frequency because of a factor such as contraction or the like of the dielectric material in sintering.
When a plurality of TE01&dgr; mode dielectric resonators are arranged at predetermined intervals in a metal case to constitute a dielectric filter, coupling between an input/output means such as a metal loop and a dielectric resonator or between dielectric resonators is determined by the distance therebetween. For this reason, the resonators and the like must be arranged at a high a positional precision.
Therefore, the present inventor proposes, in Japanese Patent Application No. 7-62625, a dielectric resonator which solves the above problems and is excellent in processing precision and a dielectric filter which is excellent in positional precision.
The basic arrangement of a dielectric filter according to this application is shown in FIG.
12
.
FIG. 12
is an exploded perspective view of the dielectric filter according to this application.
As shown in
FIG. 12
, a dielectric filter
101
is constituted by a dielectric substrate
102
and upper and lower conductive cases
103
and
104
.
The dielectric substrate
102
is a substrate having a predetermined specific inductive capacity. An electrode
102
a
is entirely formed on one major surface of the substrate except for three circular openings
102
c
each having a predetermined size, and an electrode
102
b
is entirely formed on the other major surface except for three circular openings
102
db
each having a predetermined size. The three openings
102
c
in one major surface oppose the three openings
102
d
in the other major surface, respectively.
The upper conductive case
103
consists of a metal, and has a box-like shape which opens downward. The upper conductive case
103
is arranged near the openings
102
c
of the electrode
102
a
to be spaced apart from the dielectric substrate
102
.
The lower conductive case
104
consists of a dielectric material, and has a box-like shape which opens upward and has flanges projecting from the side surfaces of the lower conductive case
104
. A shielding conductor
106
is formed on the inner peripheral surface of the lower conductive case
104
, and input/output electrodes
105
a
and
105
b
are formed at positions opposing both the end openings
102
d
of the three openings
102
d
of the electrode
102
b
such that the input/output electrodes
105
a
and
105
b
are insulated from the shielding conductor
106
. The input/output electrodes
105
a
and
105
b
are led from holes
104
a
and
104
b
formed in the side surface of the lower conductive case
104
. In addition, a spacer
107
for keeping a predetermined interval between the inner bottom surface of the lower conductive case
104
on which the shielding conductor
106
is formed and the dielectric substrate
102
is arranged in the lower conductive case
104
. The spacer
107
consists of a dielectric material having a low dielectric constant not to disturb electromagnetic fields in the upper and lower conductive cases
103
and
104
.
When this structure is used, electromagnetic field energy is confirmed by the dielectric substrate
102
near a portion sandwiched by the three openings
102
c
and
102
d
in which the electrode
102
a
opposes the electrode
102
b
, and three resonators can be achieved. For this reason, a dielectric filter having a three-stage resonator can be obtained.
With this arrangement, since a resonance region can be defined by the size of an opening portion of an electrode, a method such as etching can be used, and a dielectric filter which can extremely accurately reproduce dimensional precision of a resonator with respect to a resonance frequency and positional precision between resonances can be formed.
However, an unnecessary TEM mode electromagnetic wave may be generated by the electrode edge portions of the openings of the electrodes
102
a
and
102
b
formed on the dielectric substrate
102
. Such a TEM wave transmits between the electrodes
102
a
and
102
b
formed on the dielectric substrate
102
to be reflected by the end face of the dielectric substrate
102
to generate a standing wave, so that resonance occurs in the structure. This standing wave operates as a spurious output with respect to the filter characteristics of the dielectric filter
101
itself to affect the out-of-band characteristics of the filter. As a result, the filter characteristics of the dielectric filter
101
itself may be degraded.
An unnecessary TEM mode electromagnetic wave generated by the electrode edge portions of the openings of the electrodes
102
a
and
102
b
formed on the dielectric substrate
102
transmits between the electrode
102
a
and the conductor
104
a
or the electrode
102
b
and the conductor
104
b
to be reflected by the end portion of the dielectric substrate
102
to generate a standing wave, so that resonance occurs in the structure. This standing wave also operates as a spurious output with respect to the filter characteristics of the dielectric filter
101
itself to affect the out-of-band characteristics of the filter. As a result, the filter characteristics of the dielectric filter
101
itself may be degraded.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and has as its object to provide a dielectric filter which can suppress a spurious output acting as unnecessary resonance to prevent the out-of-band characteristics of the filter from being degraded.
A dielectric resonator according to the first aspect comprises a dielectric substrate, a first conductor formed on one major surface of the dielectric substrate, a second conductor formed on the other major surface of the dielectric substrate, a first opening formed in the first conductor to expose the dielectric substrate from the first conductor, a second opening formed in the second conductor to expose the dielectric substrate from the second conductor, a first conductive plate arranged to be spaced apart from the first conductor and to cover at least the first opening, a second conductive plate arranged to be spaced apart from the second conductor and to cover at least the second opening, a resonance portion determined by the first opening and the second opening, and an electromagnetic wave absorbing member arranged between the first and second conductive plates.
In this manner, an electromagnetic wave in a mode in which unnecessary resonance occurs can be absorbed by the electromagnetic wave absorbing member.
In a dielectric resonator according to the second aspect, the electromagnetic wave absorbing member is arranged between at least one of the first and second conductive plates and the dielectric substrate.
In this manner, an unnecessary TEM mode electromagnetic wave generated by the electrode edge portions of the openings of the electrodes
102
a
and
102
b
formed on the dielectric substrate
102
and transmitting between the electrode
102
a
and the conductor
104
a
Hiratsuka Toshiro
Iio Ken'ichi
Sonoda Tomiya
Bettendorf Justin P.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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