Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1999-01-04
2002-04-16
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S202000, C333S219100
Reexamination Certificate
active
06373351
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a band elimination dielectric filter, a dielectric duplexer, and a communication device for use in a mobile communication system for example.
2. Description of the Related Art
A conventional band elimination dielectric filter is described referring to FIG.
8
and FIG.
9
.
FIG. 8
is a perspective view of a conventional band elimination dielectric filter
110
, and
FIG. 9
is a bottom plan view. The band elimination dielectric filter
110
comprises a dielectric resonator
120
consisting of ceramic in which two dielectric columns
122
are arranged in an intersecting manner in a cavity
121
having a conductive layer, a metallic case
130
and a base plate
140
. A shield cavity comprises the metallic case
130
and the conductive cavity
121
.
The metallic case
130
comprises an upper case and a lower case, but the upper case is not indicated in the figure to illustrate the inner structure in FIG.
8
. An external connector
131
is for inputting/outputting the signal to/from the outside is mounted on the lower case
130
. The base plate
140
is formed by providing a copper film
141
on each surface of an insulated base plate, and a strip line
142
is formed by etching a part thereof. The strip line
142
functions as a &lgr;/4 wavelength line, and each end thereof is connected to an internal conductor
132
of the external connector
131
. In the base plate
140
, the strip line
142
is arranged opposite to the lower case
130
on the upper surface side of the lower case
130
so that the strip line
142
is not brought into direct contact with the lower case
130
.
One end of a loop
133
for external coupling as an external coupling means is connected to the strip line
142
. The loop
133
for external coupling is extended from the base plate
140
upwardly and approximately in the perpendicular direction, while the other end of loop
133
for external coupling is connected to an etching part
143
below the base plate
140
and a copper film
141
(earth part) other than the strip line
142
. Above the base plate
140
, the copper film
141
in the vicinity of a penetration part of the loop
133
for external coupling is removed, and an earth plate
134
having a hole of approximately same size as that of the removed part is arranged on the base plate
140
. The earth plate
134
is mounted on an inner side surface of the lower case
130
, and electrically connected thereto.
In such a band elimination dielectric filter
110
, the signal inputted from one external connector
131
flows in two loops
133
for external coupling and the strip line
142
. The loops
133
for external coupling generate the magnetic field respectively, and the corresponding loop
133
for external coupling is respectively magnetically coupled with the dielectric column
122
. Then, the signal except the frequency corresponding to the dielectric column
122
is outputted from the external connector on the output side. The band elimination dielectric filter
110
thus functions as the two-stage band elimination dielectric filter to stop the resonance frequency band specified by the size of the dielectric column
122
.
The resonance frequency and the non loaded Q of the dielectric resonator are determined by the size of the cavity and the dielectric column. When the distance in the transverse direction viewed from an opening side of the dielectric resonator is defined as the “width”, the distance in the distal direction is defined as the “thickness”, and the distance between the contact surfaces of the cavity and the dielectric column is defined as the “height”, the following relationship is obtained.
For example, when the size of the cavity is left unchanged, and the width or the thickness of the dielectric column is increased, the resonance frequency is reduced. When the size of the dielectric column is left unchanged and the width of the cavity is increased, the resonance frequency is reduced. As for the relationship between the dielectric resonator and the non loaded Q. the non loaded Q is increased as the height of the dielectric column is increased.
As the height of the dielectric column is increased, the non loaded Q of the dielectric resonator is increased, but the cavity is also increased as the height of the dielectric column is increased. Thus, the conductive layer on the surface of the cavity is also increased in size, and the loss of the actual current flowing in the conductive layer is also increased. The loss corresponding thereto partly cancels the increase in the non loaded Q obtained by increasing the height of the dielectric column. Thus, in order to obtain the required non loaded Q, there is a concern that the dielectric resonator is increased in size. From this reason, a band elimination dielectric filter free from any loss by the actual current flowing in the conductive layer on the surface of the cavity has been desired.
In a case of a two-stage band elimination dielectric filter using a TM double mode dielectric resonator in which two dielectric columns are arranged in an intersecting manner in the cavity, two dielectric columns of the same shape are formed according to the desired resonance frequency. When the non loaded Q of the dielectric resonator is increased, the height of the dielectric column is required to be large, and the cavity is also high accordingly. Increase in the cavity by increasing the height of one dielectric column means increase in the width of the cavity when viewed from the other dielectric column. As described above, when the width of the cavity is increased, the resonance frequency is reduced, and in order to obtain the prescribed resonance frequency, the width or the thickness of the dielectric column is reduced and the resonance frequency is required to be increased. There has been a concern that the resonance frequency and the non loaded Q can not be individually designed even in the two-stage band elimination dielectric filter.
SUMMARY OF THE INVENTION
The band elimination dielectric filter of the present invention is realized in view of the above-mentioned problems, and its object is to provide a band elimination dielectric filter, a band elimination dielectric duplexer and a communication device in which the loss to be generated by the actual current flowing in the conductive layer of the cavity is eliminated, the non loaded Q is high, and the height is reduced. Another object is to provide the band elimination dielectric filter, the dielectric duplexer and the communication device in which the subordination of the resonance frequency and the non loaded Q to each other is weakened, and the resonance frequency and the non loaded Q can be individually designed.
To achieve the above-mentioned objects, the band elimination dielectric filter of the present invention includes a conductive shield cavity, a dielectric resonator which is arranged in the shield cavity and provided with electrodes formed on two surfaces opposite to each other, and an external coupling means which is arranged in the shield cavity and connected to the dielectric resonator.
The actual current flowing in the conductive layer on the surface of the cavity of the dielectric resonator is eliminated by the conventional band elimination dielectric filter, and the loss at the band elimination dielectric filter is eliminated. The corresponding non loaded Q is not canceled, the dielectric resonator need not be so high, and the height of the dielectric resonator can be reduced.
In a band elimination dielectric filter according to a second aspect of the invention, the dielectric resonator is continuously arranged in the shield cavity.
The height can be further reduced thereby.
In a band elimination dielectric filter according to a third aspect of the invention, the dielectric resonators are put on top of each other in the shield cavity.
Because the actual current flowing in the conductive layer on the surface of the cavity of the dielectric resonator is eliminated and the height is reduced
Ise Tomoyuki
Kubota Kazuhiko
Lee Benny
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Summons Barbara
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