Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-09-08
2001-10-16
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S202000, C333S134000
Reexamination Certificate
active
06304158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric filter, a composite dielectric filter, a antenna duplexer, and a communication apparatus incorporating the same, used in high-frequency bands.
2. Description of the Related Art
FIGS. 12A
,
12
B,
12
C,
12
D and
12
E show a structure of a prior art dielectric filter using a dielectric block mainly used in the microwave band. In this figure,
FIG. 12B
is a front view in which the dielectric filter is vertically stood, FIG.
12
(A) is the upper-surface view,
FIG. 12C
is the bottom view,
FIG. 12D
is the left-side view, and
FIG. 12E
is the right-side view. In this figure, the dielectric block is indicated by
1
. Inside the dielectric block
1
, resonance-line holes indicated by
2
a,
2
b,
and
2
c
are disposed, and on the inner surface of the holes, an inner conductor is disposed to form resonance lines
5
a,
5
b,
and
5
c.
On an outer surface of the dielectric block
1
, a ground electrode
3
is formed, and external terminals
6
and
7
separated from the ground electrode
3
are disposed at predetermined positions. The external terminal
6
and the resonance line
5
a
make a capacitive coupling, whereas the external terminal
7
and the resonance line
5
c
make a capacitive coupling. In this way, a dielectric filter having a pass-band characteristic of three-stage resonators is formed.
However, in the prior art dielectric filter shown in
FIGS. 12A
to
12
E, the external terminals
6
and
7
perform the input and output of signals in a imbalanced type, in which the respective ground electrodes being used as reference potentials. Therefore, in order to give signals to an amplification circuit of a balance input type for example, it is necessary to convert the signals of imbalance type to those of balance type by using a balun (an imbalance-balance converter). As a result, the filter occupies a large area portion on a circuit board, which being one factor hampering miniaturization.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a dielectric filter and a composite dielectric filter, in which input and output of signals can be performed in a two-terminal type or a balance type without using the balun, and a communication apparatus including the same.
One preferred embodiment of the present invention provides a dielectric filter, comprising: a plurality of resonance lines aligned in a dielectric block, in a dielectric substrate, or on a dielectric substrate; a plurality of input-output units respectively coupled to the plurality of resonance lines; at least one of the input-output units comprising a first external terminal capacitively coupled to one of the plurality of resonance lines, an external coupling line coupled to the one of the plurality of resonance lines to which the first external terminal is capacitively coupled, and a second external extending from an end of the external coupling line.
The above described dielectric filter can perform input and output of signals by using two terminals, which are not of the same phase.
In the above described dielectric filter, the phase difference between the signals of the first and second external terminals viewed from the one of the plurality of resonance lines to which the first external terminal is capacitively coupled may be substantially 180°. By this arrangement, the input and output of signals of balance type becomes possible.
Another preferred embodiment of the present invention provides a composite dielectric filter comprising a plurality of filters, wherein at least one of the plurality of filters are the above described dielectric filter; and a resonator comprising the resonance line is coupled between the one of the plurality of input-output units and the others of the plurality of input-output units.
Yet another preferred embodiment of the present invention provides an antenna duplexer comprising the composite dielectric filter of claim
3
, wherein the plurality of input-output units comprise a transmission signal input terminal, a reception signal output terminal, and an antenna terminal; and the plurality of filters include a transmission filter provided between the transmission signal input terminal and the antenna terminal, and a reception filter provided between the reception signal output terminal and the antenna terminal.
According to the above described composite dielectric filter, the plurality of filters are provided inside the single dielectric block, inside the single dielectric substrate, or on the single dielectric substrate. Further, a balun is not needed to be additionally disposed. Accordingly, the overall device can be further miniaturized. For instance, a transmission signal input terminal, a reception signal output terminal, and an antenna terminal are provided as the plurality of input-output units, a transmission filter is provided between the transmission signal input terminal and the antenna terminal, and a reception filter is provided between the reception signal output terminal and the antenna terminal to constitute an antenna duplexer.
Furthermore, a communication apparatus may be obtained by providing the above described dielectric filter or composite filter in a high-frequency circuit section. According to this arrangement, a compact and lightweight communication apparatus can be obtained.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 5489882 (1996-02-01), Ueno
patent: 5712604 (1998-01-01), Tada et al.
patent: 5870006 (1999-02-01), Tada et al.
patent: 5905420 (1999-05-01), Tsujiguchi et al.
patent: 6023207 (1999-02-01), Ito et al.
patent: 6163237 (2000-12-01), Toda et al.
Hiroshima Motoharu
Kato Hideyuki
Matsumoto Haruo
Nishijima Shohachi
Murata Manufacturing Co. Ltd.
Nguyen Patricia T.
Ostrolenk Faber Gerb & Soffen, LLP
Pascal Robert
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