Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
2002-08-14
2003-11-04
Ham, Seungsook (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S235000
Reexamination Certificate
active
06642815
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a multi-purpose dielectric resonator filter for use at a mobile communication base station to serve as each of a receiving filter, a transmitting filter, a duplexer, and the like.
Conventionally, band pass filters for allowing the passage of only signals in a specified frequency band have been used at base stations for mobile communication such as a mobile phone. For example, a receiving system uses a receiving filter to remove signals for communication systems using the other frequency bands and a transmitting system uses a transmitting filter not to send undesired electric waves to the systems using the other frequency bands. Such filters for use at the base stations are required to have a sufficiently low loss to provide the base stations with an adequate receiving sensitivity and power efficiency, a sharp filter characteristic provided for a reduced interval in frequency band between the adjacent base stations, and reduced size and weight for easier mounting on the overheads of the base stations. As an example of a filter satisfying such requirements, a dielectric resonator filter composed of a plurality of dielectric resonators coupled to each other has been proposed, which comes in various configurations.
FIG. 21
is a perspective view schematically showing an example of a conventional six-stage dielectric resonator filter. As shown in
FIG. 21
, the conventional dielectric resonator filter comprises six cylindrical dielectric resonators
511
A to
511
F formed by sintering a dielectric powder material. The resonance frequency of each of the dielectric resonators
511
A to
511
F is determined by the height and diameter of the cylindrical configuration thereof. In this example, the six dielectric resonators
511
A to
511
F operate as a six-stage band pass filter. An enclosure
520
of the dielectric resonator filter comprises a main body
521
composed of a bottom wall and side walls, a lid
522
, partition walls
523
A to
523
G connected to each other to partition, into chambers, a space enclosed by the enclosure main body
521
. The dielectric resonators
511
A to
511
F are disposed on a one-by-one basis in the respective chambers defined by the partition walls
523
A to
523
G of the enclosure
520
. Interstage-coupling tuning windows
524
A to
524
E for providing electromagnetic field couplings between the resonators are provided between the five partition walls
523
A to
523
E of the seven partition walls
523
A to
523
G and the side walls of the enclosure main body
521
. The interstage-coupling tuning windows
524
A to
524
E are provided with respective interstage-coupling tuning bolts
531
A to
531
E each for tuning the strength of an electromagnetic field coupling between the resonators. The enclosure main body
521
is provided with input/output terminals
541
and
542
each composed of a coaxial connector to input and output a high-frequency signal to and from the outside. Input/output coupling probes
551
and
552
are connected to the respective core conductors of the input/output terminals
541
and
542
.
Resonance-frequency tuning members
561
A to
561
F each composed of a disk and a bolt formed integrally to tune the resonance frequency of the corresponding one of the dielectric resonators
511
A to
511
F are attached to the enclosure lid
521
. The resonance-frequency tuning members
561
A to
561
F are disposed to have their respective center axes at the same plan positions as the respective center axes of the dielectric resonators
511
A to
511
F (i.e., at the concentric positions).
Since the frequency characteristics including passband width and attenuation characteristic of a dielectric resonator filter are generally determined by the resonance frequency and Q factor of each of the resonators and an amount of coupling between the individual dielectric resonators, the configuration and the like of each of the dielectric resonators are calculated from the specifications of the frequency characteristics of the filter at the design stage. In practice, however, filter characteristics as designed cannot be obtained due to an error in the configurations of the dielectric resonators and enclosure and to a mounting error. To provide filter characteristics as designed, the resonance-frequency tuning members
561
A to
561
F are provided in the conventional dielectric resonator filter to render the respective resonance frequencies of the dielectric resonators
511
A to
511
F variable. In addition, the interstage-coupling tuning bolts
531
A to
531
E are provided to render the strengths of interstage couplings variable. Through the tuning using the tuning mechanism, desired filter characteristics are provided.
For the resonance-frequency tuning members
561
A to
561
F, a structure as shown in
FIG. 21
has been used widely in which the frequency characteristics of the dielectric resonators
511
A to
511
F are made variable by tuning the distance between conductor plates opposed to the dielectric resonators
511
A to
511
F and the dielectric resonators
511
A to
511
F by using the bolts.
The dielectric resonator filter having such a structure operates as follows. If a high-frequency signal transmitted from, e.g., a signal source or an antenna and inputted into the enclosure
520
via the input/output terminal
541
has a frequency within the pass band of the filter, the signal couples to an electromagnetic field mode in the input-stage dielectric resonator
511
A by the effect of the input/output coupling probe
551
so that TE01&dgr; as a basic resonance mode is excited.
The resonance mode couples to respective electromagnetic field modes in the subsequent dielectric resonators
511
B,
511
C, . . . in succession through the interstage-coupling tuning windows
524
A,
524
B, . . . so that the electromagnetic field mode excited in the dielectric resonator
511
F couples to the output-side input/output probe
552
and the high-frequency signal is outputted from the input/output terminal
542
. On the other hand, the high-frequency signal having a frequency outside the pass band of the filter is reflected without coupling to the resonance mode in the dielectric resonator and sent back from the input/output terminal
541
.
FIG. 24
is a perspective view schematically showing an example of a conventional four-stage dielectric resonator filter. As shown in
FIG. 24
, the conventional dielectric resonator filter comprises four cylindrical dielectric resonators
611
A to
611
D formed by sintering a dielectric powder material. In this example, the four dielectric resonators
611
A to
611
D operate as a four-stage band pass filter. An enclosure
620
of the dielectric resonator filter comprises a main body
621
composed of a bottom wall and side walls, a lid
622
, and partition walls
623
A to
623
D connected to each other to partition, into chambers, a space enclosed by the enclosure main body
621
. The dielectric resonators
611
A to
611
D are disposed on a one-by-one basis in the respective chambers defined by the partition walls
623
A to
623
D of the enclosure
620
. Interstage-coupling tuning windows
624
A to
624
C for providing electromagnetic field couplings between the resonators are provided between the three partition walls
623
A to
623
C of the four partition walls
623
A to
623
D and the side walls of the enclosure main body
621
. The interstage-coupling tuning windows
624
A to
624
C are provided with respective interstage-coupling tuning bolts
631
A to
631
C each for tuning the strength of an electromagnetic field coupling between the resonators. The enclosure main body
621
is provided with input/output terminals
641
and
642
each composed of a coaxial connector to input and output a high-frequency signal to and from the outside. Input/output coupling probes
651
and
652
are connected to the respective core conductors of the input/output terminals
641
and
642
.
Resonance-frequency tuning members
661
A to
661
D each composed of a disk and a bolt fo
Enokihara Akira
Minami Kunihiko
Nakamura Toshiaki
Okajima Michio
Okazaki Yasunao
Ham Seungsook
Harness & Dickey & Pierce P.L.C.
Matsushita Electric - Industrial Co., Ltd.
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